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Fireside Chat: Q&A with the Xperts

Posted by Charles Wells

In this Fireside Chat with the Xperts, Dr. Glen Thomas and Dr. Bill Cardoso take time to address some of the questions that have come up during earlier presentations.  We got some great questions from viewers, and the doctors really put the “X” in Xperts when tackling them.  Questions covered this week included: What are the differences between open and closed X-ray tubes?  How are reflective and transmissive sources different? How does geometric magnification work? What is the difference between kV and mA?

If you are operating an X-ray system, considering how a system might suit a particular application, or just intensely curious about how X-ray machines work, this presentation will scratch your itch. Register for upcoming Fireside Chats with the Xperts and view our archives here.

 

Transcript:

David Kruidhof:

Morning, everyone. Thanks for joining us this week for another. Fireside Chat with the Xperts. Today, we’re doing a Q&A, that we’ve had several questions over the last few weeks on our topics that we’ve covered, we weren’t able to get all of the questions, so we just want to take a break for going into these new topics and answer some of those for you. So we have today, Dr. Bill Cardoso, our CEO, and Dr. Glen Thomas, our VP of Technology. So we’re pulling out the big guns, lots of knowledge here, lots of experience with X-ray. So we’ll be diving into these questions for you.

Dr. Bill Cardoso:

He was talking about you, Glen, when he said big guns, by the way.

Dr. Glen Thomas:

Yeah. Okay. Yep. We’ll see. We’ll see how stumped we can get. Sounds good.

Dr. Bill Cardoso:

Should have called the segment, “Stump the Chumps.” That’d be funny.

Dr. Glen Thomas:

There you go.

David Kruidhof:

So our first question, what are the differences between open and closed X-ray tubes?

Dr. Glen Thomas:

Open and closed X-ray tubes are, that’s a consistent question that we get on a regular basis. You have to go back to the basics of why an open X-ray tube was designed, and it all starts with the physics of X-ray, right? We can bend the rules, but the rules are always going to be there. And the rule is, you can have one watt of power per micron of focal spot size. Focal spot size gives us the resolution, because it’s a pin source, right? It’s a point source, just like a flashlight or even the sun. It’s a point source. So that is the point that the X-ray, or the electron beam hits the target anode and reflects.

Dr. Glen Thomas:

So with that one watt per micron limitation, in the late sixties, they were running into some problems in industry that we were looking, trying to see through jet engine impellers and jet engine components, right? And we needed the resolution to see some of those welds. The problem was that to get past that one watt per micron of focal spot law, essentially, we would have to open up the focal spot, to the point where you were less resolution on your X-ray tube than the requirement of the application, right?

Dr. Glen Thomas:

So some really smart guys got together and designed an open X-ray tube, which is essentially, all X-ray tubes have consumables. The consumable is the filament, which is where we burn the electrons off of the filament, just like a tungsten light bulb. And then we have the anode, which is the point that we have the electron beam coming from the filament, hitting the anode, producing photons. You have about a 3,850 degree temperature at that point. And that’s the main reason why we can’t exceed that wattage, because it will start melting holes in the tungsten. So essentially, to be able to pull that off reliably, pull that heat off, there’s 98% of X-ray energy that’s produced during making an X Ray image is heat. So we had to pull that heat off very quickly.

Dr. Glen Thomas:

To get around that concept, they decided that it would be a good idea to make those consumables replaceable by the operator. There are some other schemes in medical applications that we do the same concept as far as saving the focal spot, and being able to apply a lot more power to the focal spot. But that’s just, again, another way to trick physics, right? So the concept there was, we could take an image and we can take a very high power image, say 10 watts per micron, and we can intentionally destroy the X-ray tube. We can destroy the filament and we can destroy the anode.

Dr. Glen Thomas:

So an open X-ray tube is designed to be field repairable by a fairly experienced or trained technician. You’ll get a lot of rhetoric about, “Oh, it’ll last forever,” and you just got to change the filament and you just have to change the anode. It’s an easy task if you have the training to do so. So essentially this X-ray tube was designed that would vacuum itself down every time you turn the tube on. So you would take an image, you would get a two minute shot, you would just totally destroy the X-ray tube, but they were accomplishing what was needed. And what the requirement was, we need high resolution images of very heavy, dense components. So that was a success.

Dr. Glen Thomas:

Open X-ray tubes have a lot of ancillary sub components that no one ever seems to mention. They say, “Oh yeah, this tube will last forever. You can change the filament and rotate the anode. Right?” What they don’t tell you is you have a turbo molecular pump, you have a roughing pump, you have a high voltage component that’s almost, in some cases, larger than the cabinet itself, as well as a cooling system to cool the tube, right? Because if we’re pulling out all of that heat and we’re intentionally creating a lot of heat, you can literally destroy the X-ray tube housing. You can melt it. So we still have to pull off a real large amount of heat fairly quickly.

Dr. Glen Thomas:

So, in a closed X-ray tube is essentially that. It’s an X-ray tube that’s vacuumed down during manufacturer to about 10 torr, as far as pressure. The X-ray tube has a fixed element, it has a fixed anode, as well as, in most cases, a lot of focusing grids, or essentially magnetics that focus that electron beam to a really fine point. Service wise, there are no end user serviceable parts. In open X-ray tube, you have the filament, you have the anode, you have O-rings, you have greasing of the high voltage components like the wells for the high voltage cables. So there’s all kinds of different parts that have to be maintained.

Dr. Glen Thomas:

Closed X-ray tube, it either works or it doesn’t, there’s not really much that’s a user serviceable issue, but they are highly reliable and they are somewhat maintenance free. We get a lot of complaints or questions that says, “Well, I have to replace the whole tube when it breaks.” Yes. Closed X-ray tube, you do have to replace the complete housing, the complete tube, the high voltage, say in five to seven years, 10 years, depends on your usage, because if you remember, every X-ray tube has consumable components. Every time you create X-rays, you’re pulling electrons off of that tungsten, just like a light bulb in your house, and you turn on the tungsten light bulb.

Dr. Glen Thomas:

So eventually the X-ray tube, the closed X-ray tube, will die or will become unusable due to the pitting on the anode itself. So you get a really bad X-ray image, and it happens so slowly, over time, that you don’t even realize it. If you walked in, the operators using this machine, and unless he’s using IRQ or image quality indicators, he really has no clue that it’s degraded to the point that it has. And you walk in as a service guy, or even a sales guy, and you look at it and you’re like, “Wow, what’s up with that?” And they’re like, “What?” So, but over a five to seven year period, you will probably have to replace the closed tube.

Dr. Glen Thomas:

Yes, they are fairly expensive. Could cost tens of thousands of dollars, depending on the tube. But when you look at the individual maintenance, and downtime, and the expertise that it takes to service an open X-ray tube, the costs are pretty close to the same, right? So you pay a lot more money up front for the ability to have a lot more service issues with an open X-ray tube, and a closed X-ray tube, you pay a fair amount of money, but you have maintenance free for five to seven years. Right?

Dr. Glen Thomas:

One of the major disadvantages of that X-ray tube is, if you don’t really know what you’re doing, and you get some dust in there, so in a dusty environment or production environment, one speck of dust would be enough to destroy an open X-ray tube. Problems that you have with open X-ray tubes is when you, if you get a fingerprint, or you get dust, and you fire that thing up, you’re going to create carbon tracks. That X-ray electron beam is going to find a different place to land, other than the anode that you expect. And when it does that, it could pit the interior of the X-ray tube to the point where it’s now unusable, you have to buy a new one. A single fingerprint inside of an open X-ray tube will destroy the tube forever. It’s impossible to fix that. The oils in your skin will create an arc, and you will have a major issue.

Dr. Glen Thomas:

The only advantages of an open X-ray tube, a recent, in the last few years is, when you use it in electronics, you can get high magnifications. And the main reason for that is we can direct that electron beam to, say, the window of the X-ray source. Typically we would use an anode made out of tungsten, and that anode is embedded in a copper substrate, a bar. And essentially that bar is grounded and it has a heat sink on the end of it that’s immersed in high voltage oil, right? When you look at the open X-ray tube, we can actually aim that electron beam at the window, and we can use a diamond, and we can use some other exotic windows, that create the X-ray photons at the window. And what that does is that allows for extreme magnification on the X-ray source. So in applications like electronics, the only reason to go with an open X-ray tube would be if you needed extreme magnifications.

Dr. Glen Thomas:

And being a capitalist world, closed X-ray tube manufacturers have made some really unbelievable X-ray tubes in the last few years that rival the magnification of an open X-ray tube, in a closed tube package. So you get to all of the advantages of an open X-ray tube for a general operator with electronics, you’re never going to overdrive the X-ray tube intentionally. So you get all of the advantages of an open X-ray tube, as far as magnification, and you get it in a nice compact package, which results in a smaller cabinet in the X-ray, and a small overall footprint of the X-ray system itself, because you don’t have the external coolers, the external high voltage requirements.

Dr. Glen Thomas:

So it’s just, open X-ray tubes have their place. But in my opinion, open X-ray tubes really don’t have a place in electronics unless you’re looking at high magnifications, and we’re eliminating that as well.

Dr. Bill Cardoso:

Yeah, I think that’s been a huge improvement, or development, or the past few years is that transmissive closed tube source that’s being… And just for some background, on a closed tube, or even in an open tube, we have two different processes to generate X-rays, right. You can have your target, your anode, it can be on an angle like this one, pretend my phone’s a target here. And you have what’s called an electron gun, or the filament, that’s going to warm up and generate free electrons. Those electrons get accelerated and when they hit the target, you have this shower of X-ray photons getting out of the source, right? So X-rays get generated here, they go super fast, hit the target, and there’s something called bremsstrahlung radiation. So the electoral is moved out of the shell, and then when it goes back to its shell, it emits this X-ray photon. So that’s called reflective tube, because you can see it reflects, there’s a reflective motion to generate X-rays.

Dr. Bill Cardoso:

And then what Glen was talking about is the transmissive. So the window that provides that vacuum seal of the tube, so this is the outside world, this is inside the tube. Instead of reflecting, what you do is you put the target at the window and you shoot the electron beams right at the window, and on the other side you have X-ray photons coming out.

Dr. Bill Cardoso:

So what does it matter? Right? Because this method is really, really, really hard to make. The reflective method, it’s been around since the late 1800s. That’s what Röntgen was playing with when he discovered X-rays in the first place, right? This, the advantage of reflective, right? It’s been around for a while, because here in the back of the anode, you’re usually going to see a chunk of copper, a chunk of metal, to cool off this side of the X-ray tube. Why? Because as you have, as Glenn was saying, right, you have a lot of electrons hitting this target. It’s going to warm up, right? It’s going to create a lot of heat, and you have to dissipate the heat. If you don’t, you end up putting a pin, a hole on the target, and that hole is going to screw up with your resolution. Why? Because out of this target, you want the X-ray’s to get out of here in a perfect cone, every line going like this, going like that. But perfect, so that target ideally is a point in space.

Dr. Bill Cardoso:

If you start warming up because of the temperature, the stress of the material of the target, what happens is that there’s not a point anymore. Now it became an area, and in that area is going to happen, is this electron comes this way, one X-ray photon on goes that way, the other one goes that way, and as a result, you end up with a fuzzy image. So the edges of the image are not as sharp as they could be. This is the difference between mini focus or micro-focus or a nano focus X-ray resource, the smaller the target, the better the resolution, the lower the power that you can run. Like Glenn said, if you want to blast a lot of power, you’re not going to have a tiny target anymore. Right? It’s going to warm up and make your resolution worse.

Dr. Bill Cardoso:

So there’s a lot of heat here, right? So if you take this target and you put at the window, you want this window to be as thin as possible. If you have a thick window, a block of copper to cool off the target, you’re not going to have an X-rays coming out, right. They’re going to be shielded by the window itself. So you need thermal dissipation, right? A low impedance thermal path from the target to your cooling, heat sink. And at the same time it has to be really thin, ideally, no matter at all. So that is a big challenge that X-ray source companies have been working with the past few years. And diamond is one of the materials that fits the profile of being good heat dissipation, it’s very strong and you can make it very thin, right? So it doesn’t shield the X-rays that you’re generating.

Dr. Bill Cardoso:

And so what does it matter? What does it matter if it’s a reflective source or a transmissive source, right? Why go through the pains of making a transmissive source with this exotic window? Because, can you imagine, you have to hold vacuum here, right? So you have the box of the X-ray source, that’s my little window that this target, and at the same time it has to hold vacuum. What happens when things warm up? Expand? What happens when they cool off? They contract, right? So this has to keep vacuum, at the same time that it has to stay stationary in one place, because you don’t want your target doing this. Right. And it has to hold vacuum while expanding and contracting, because of the heat that’s being generated here. So not an easy mechanical object to build.

Dr. Bill Cardoso:

It matters because of magnification. Right? Glenn also mentioned magnification. Magnification, if you imagine you have your source here, okay, on my window, the sample is going to be sitting on top of the source. Then I have my sample, and then the sensor is going to be on the other side of the sample, and the X-ray image is going to be the shadow of my sample on to the sensor. The magnification is going to be, so M for magnification is going to be one plus the distance between the sample and the sensor, is the numerator. And the denominator is distance between the sample and the source. So what does that mean? So it’s one plus this distance, divided by this distance, what does it mean? It means that to magnify, I have to bring my sample as close as possible, right? As close as possible to my source.

Dr. Bill Cardoso:

Now, if my source is like this, and that point is several, maybe a half an inch, an inch away from where the window is, that limits how much I can magnify my image, right. Now, if my target is now 300 microns behind a window, or half a millimeter, right, now I can bring my sample, place right on top of the source and achieve very, very high degrees of magnification. So this transmissive closed tubes have really allowed us to provide the best of both worlds. Really high mag, because a transmissive source, and at same time, a closed tube. So we can offer a low maintenance X-ray source.

Dr. Bill Cardoso:

And so nowadays you could ask us, when do we use one or the other? Because we’ve used both, and open tubes and closed tubes, they have their place in X-ray applications. For the high mag, in the past, we used an open tube, now we’re using this transmissive closed tubes because they’re just easier to use, and we don’t have to be worrying about the two vacuum pumps and a high voltage block, and a cooling system for the tubes, it’s much simpler, more compact and make things much easier for the user. And we leave the open source nowadays for the high power stuff, right. But when you get to the 225, 300 kVs and up, we’re going to be talking about an open tube application, because at that level or that amount of power, there’s no diamond enough today that can pull that kind of power. Now we’re talking, you’re going to be discussing rotating anodes, we’re going to be talking about a chiller that can pull quite a bit of heat out of the source.

David Kruidhof:

All right, thank you, gentlemen. That was a lot about reflective or transmissive as well.

Dr. Bill Cardoso:

Well that was the, we were summarizing, right, Glen?

Dr. Glen Thomas:

Exactly. We had at least three questions there.

David Kruidhof:

Great.

Dr. Glen Thomas:

That’s good.

David Kruidhof:

All right. That’s good. Well, we got eight minutes, so I’ll give you a simpler one.

Dr. Bill Cardoso:

It’s got to be a yes or no question, otherwise it’s going to take more than eight minutes.

David Kruidhof:

What’s the difference, practically speaking, right? What’s the difference between kV and mA, kilovolts and amps, milli amps, micro amps, in a source? What does that practically mean, when a customer is designing a system?

Dr. Glen Thomas:

So that’s another one that could be a long conversation, right?

David Kruidhof:

Don’t make this one long, Glen.

Dr. Bill Cardoso:

Yes. There is a difference.

David Kruidhof:

There is a difference. Done.

Dr. Glen Thomas:

So if we look at kV and mA, and an easy way for a layman, without getting into the physics, is to think of a garden hose, right? Consider the X-ray tube, the same as a garden hose, where we’re projecting photons, and in this case, where our water hose is projecting water, right? So if you look at the kV, the kV would be the pressure, the amount of pressure that pushes the water, or the photons out of the hose, right? So the kV gives you the ability to penetrate items. The higher the kV, the better, and the faster the photons are going to be able to traverse through the sample. So kV is the penetration, that’s the power behind the electrons and the photons.

Dr. Glen Thomas:

mA, if you think of the water hose analogy, the mA would be the diameter of the hose, the amount of water, or in an X-ray tube, the amount of photons that make up the X-ray beam. Because we could essentially have an X-ray beam that’s 150 kV and one photon, right? You will get a small blip on some screen somewhere, but you won’t be able to create an X-ray image. To create a usable X-ray image, you need to have the proper amount of penetration, which is the kV, to be able to penetrate the part, and you need enough photons to actually create an image. If you think of that, you think of a dot matrix printer, right? The lack of photons would be the same as if you had a dot matrix printer that was putting out, or even worse yet the nine pin printer of the eighties, right? You’ll get a definite-

David Kruidhof:

Maybe he doesn’t know what that is, Glenn.

Dr. Glen Thomas:

You’ll get a definite degradation of the image. So the mA gives you more photon statistics, the ability to light up the image detector, whether it’s a film, digital detector, image intensifier, regardless, the mA gives you more photon statistics. It puts more photons on the image. And then it goes back to that physics concept, as we still have a wattage issue. Right? So if we have, typically in an electronics X-ray system, pretty standard is nine watts of power, right? So that gives us the ability just to do a hundred, let’s say 90 kV at 0.2 mA right, is a good number. 0.256 mA. So we use very low mA. So we have the ability to maintain that focal spot.

Dr. Glen Thomas:

A lot of X-ray tubes are iso watt, which means that they are limited in wattage. You can’t overdrive the X Ray tube. If you crank up the kV to a real high point, the X-ray system will drive down the mA, to maintain a stable wattage that stays within that safety threshold of the X-ray source and the X-ray tube. So in a lot of cases, you’re not using the full kV of an X-ray source. Your optimum kV is somewhere in between zero and the full, maximum power. So with that, you get a happy medium in kV, which is the ability to penetrate the part. Because if you over penetrate the part, you start losing artifacts, or you start losing details in the actual X-ray image. So there’s a fine point where kV and mA make a difference. If you over penetrate the part, and you don’t have enough kV, you could still get an image, but it’s going to be a very grainy image. It’s going to be featureless for a matter.

Dr. Glen Thomas:

So what you want to do is have a happy medium of kV and mA. And through algorithms, back in the day, you had to be fairly fluent in X-ray to understand how much kV and mA. A practitioner like an RT in a medical industry, they’re really good at knowing what their kV and mA is going to come out to. They make those determinations fairly quickly, because their samples change. They may be doing an elbow or wrist, but each individual has a different density, so they will make those changes on the fly. And they’re pretty highly trained at being able to make those judgments.

Dr. Glen Thomas:

Used to be X-ray, industrial X-ray, was the same thing. Back in the day, when it was all film, and you only had one shot one and chance. So you would climb up on a bridge, or you would climb up on a tower, essentially they would stack the film and they would run a multiple, so they would stack the film and they would do one X-ray image at, say, one mA, 10 seconds at a hundred kV. And then they would pull one off the film, and since film is a cumulative, they would continue to add time and kV and mA adjustments to get a bunch of exposures, right? So they would have a lot of different exposures in this one shot, and they were up in the air. So they would come down, and then they would pick the best image out of, say, 10, right? So that kV and mA adjustment is somewhat tricky.

Dr. Glen Thomas:

And one thing that we’ve done to eliminate some of those issues for an operator is the wise software that we have. It adjusts kV and mA, and it adjusts brightness and contrast, and has some algorithms that will give you the ability to make those changes seamless. The software looks at the exposures and looks at the gray scale values based on the histograms, and will make those adjustments for you. So all you really need to know if you’re an operator is the basics of what they do. And the main reason for that is that you get a general idea of what kV you need to not over penetrate the part, and you let the X-ray system and the software make those other decisions as far as how much brightness, contrast, exposure rates and the mA that’s needed to accomplish the goal.

David Kruidhof:

Nice, thanks, Glen. Right on time. It’s 10:30 on the dot. You must be watching the clock.

Dr. Glen Thomas:

Well, we can keep going.

Dr. Bill Cardoso:

He’s done it before, David.

David Kruidhof:

Well, we have a long list of questions. So we’re going to continue this next week. I want to keep these to half an hour for you guys, as we said we would. So if you have any other questions that came up today, or questions you just want answered in general, if you’re watching this on YouTube later, you can leave a comment below, or you’re welcome to email us info@creativeelectron.com. Thanks, Glenn. Appreciate it. Thank you, Bill for your time.

Dr. Bill Cardoso:

Thank you, guys.

David Kruidhof:

And please join us again next week.

Dr. Glen Thomas:

Thanks. Take care.

David Kruidhof:

Bye.

Speaker 5:

Creative Electron

Partner Webinar: X-ray & Deep Learning-Based Inspection Solutions for Medical Devices

Posted by Charles Wells


Our VP of Engineering, Carlos Valenzuela, will be joining Matt Remnek of Cognex in a conversation about X-ray & Deep Learning-Based Inspection Solutions for Medical Devices.  Carlos has been working with customers in the medical device space for years to develop autonomous custom systems for their unique applications. He knows that every device is unique and requires its own solution, which we deliver using our X-ray expertise, software skills, and team of mechanical engineers.

Join us to learn about the broad range of analysis that can be performed on your medical device using X-ray and Cognex inspection solutions, including final internal product integrity verification, final packaging assembly verification, in-process metrology of components, and counterfeit prevention.

Cognex will be hosting this webinar on June 23, 2020 at 2pm EDT | 1pm CDT | 12pm MDT | 11am PDT

Please register here to receive an invite to the webinar.

Fireside Chat: The X-Factor – How X-ray Technology is Improving the Electronics Assembly Process (Part II)

Posted by Charles Wells

Ok, so it’s no Godfather Part II, but this sequel still packs a punch.  Dr. Bill Cardoso provides the star power for this Fireside Chat with the Xperts, as we continue to explore the important role of X-ray inspection in electronics manufacturing.

Dr. Cardoso demonstrates why he’s our MVP when it comes to understanding bottom terminated components (BTC) such as QFP, QFN, and BGAs on PCBs.  Not to be missed, he shares one of his all-time favorite X-ray images of a BGA that is a one stop shop for common defects.  Join us for other Fireside Chats with the Xperts here.

 

Transcript:

Dr. Bill Cardoso:              Welcome to another Fireside Chat with the Xperts. Today, I’m really happy to be here with my colleague and good friend, Dr. Glen Thomas. And the topic for today is a continuation of the presentation we started last week, which is an overview on the basics of X-ray inspection. So the idea here should give you an overview of how X-ray technology works and the many applications where X-rays are utilized. So last week, Glen went over several different X-ray applications. Some of the basics and the physics of X-ray inspection, and we stopped last week at the bottom terminated component. So just to give you a quick overview, a bottom terminated component is every component where the leads or the contacts are under the component. So the bottom line is you can’t really see those solder points because they’re being hidden by the component itself.

Dr. Bill Cardoso:              And got to a point in why they exist, right? Why BTCs exist? Well, as technology evolved and microchips got denser and denser and denser, engineers, component engineers, put the leads or the contacts on periphery of the component. So we’ve all seen the components. They started, they were rectangular and have leads or contacts on both sides. And as time evolved, the flat pack was developed. So you had contacts on the four sides of the component that were started to be square. There were some difficulties assembling them, but what happened is we got to a point where, as the Silicon Valley technology evolved, the density of those components increased. And as a result, the periphery of the component wasn’t enough to put all the content. So the component engineers at the time in the ’80s developed this ball grid array technology.

Dr. Bill Cardoso:              So the pads ended up on the bottom of the component, and here’s a side view of that arrangement. So you have the components over right here, that’s all your silicone and all the electronic smarts are, and the interface of the world printed circuit board is done through these balls and contacts that are underneath the component. The problem as we talked about last week is that you can’t really see those pads anymore because now they’re being hidden by encapsulation of the component.

Dr. Bill Cardoso:              So X-ray technology became essential in the manufacturing of electronic circuits, because only with X-ray you can see through the component and visualize these solder connections, like you can see here on the right. And with that, and why do you need to do that? Well, you need to make sure that those solder connections are there to begin with, that they are done properly. Do you have enough solder on each one of those contacts? And that those solder points are not touching each other, thus causing short-circuits. Well, we have… I would like to share with you the best and also the worst BGA or Ball Grid Array X-ray image ever, ever, ever. Why is the best and the worst? It’s the best from an X-ray perspective and from an understanding perspective, because this one X-ray image has every single problem you can find on a BGA assembly. It’s incredible.

Dr. Bill Cardoso:              And it’s also the worst because it has all the defects you can imagine in one BGA assembly. So let’s walk around this image and go over what the problems are. The first one can see here is coplanarity. Coplanarity can be visualized once you have this tilted view of the BGA. So if you look straight down with an X-ray, you have this two dimensional view, and as you tilt the board, or you tilt the sensor, you have this perspective view of the BGA, and that’s what we’re looking at here. We’re going to go over more details, and we’ll call it two and a half D, which is a made up term developed by X-ray companies. But we’re going to go over what’s 2D, two and a half-D and 3D, but for now, just think that this is a tilted view of this BGA.

Dr. Bill Cardoso:              And as you look at that row of balls on that corner, on that side of the BGA, you see that this ball is fairly round. And as you move towards the right side of the BGA, the ball gets elevated. You have this hour glass shape forming up here. So what this physically represents is that the BGA is like this. So that’s the PCB here, and the BGA is off, taking off from the board. So the coplanarity is a big problem because it means that you have… might end up with no contacts in one side of the BGA and short on the other side of the BGA. So what causes that? Once the BGA goes reflow profile, there is a wide range of CTE mismatches that occur during the process. CTE is coefficient of thermal expansion.

Dr. Bill Cardoso:              So the CTE mismatch causes the potato chip effect. So the BGA basically can go like this if it’s a heated past it’s capabilities. So either the BGA or the board potato chip causing this effect. Or during the reflow the BGA can walk, and if not enough or a disproportional amount of solder has been placed on different pads, you might end off just by the capillarity of the solder as it wets, you might end up having this effect. Big problem. It’s definitely something that has to be inspected and looked at. Short circuits are fairly straightforward to recognize. So here you have two balls that have been a shorted together. A head-in-pillow is a difficult one to see and to find because head-in-pillow is that problem where the board, your assembly, works sometime. And sometimes it doesn’t work.

Dr. Bill Cardoso:              Usually it works when it’s in your shop while you are making things. You test it and it works, you ship, and your costumer says it doesn’t work. Then you test it and guess what? It works. And because this is a problem where the ball sits on the pad, and it makes contact once in a while. It depends on… We’ve seen a situation, for example, where the test jig that was testing the board was enough to push the BGA down and make contact. As soon as released from the jig and shipped to the customer that contact open, and now the board doesn’t work. So you bring to your facility, your test on the jig and works perfectly fine because that jig is applying physical force onto the BGA to make contact. You shipped to the customer. You don’t have the jig, it doesn’t work. So it’s a very hard problem to diagnose because of this in terms of functioning, and it’s called head-in-pillow because it resembles a head on the pillow. It just rests and opens from time to time.

Dr. Bill Cardoso:              Again, another defect mode that requires a tilted view and again, very hard to diagnose, very hard to find. But when you find it can signify insufficient reflow, because you weren’t able to wet the ball onto the pad. In a situation like this, since you have coplanarity, it might mean that we didn’t have enough physical contact between the pad on the board and the ball itself to properly wet and make the metallurgic contacts that you need to have a reliable solder joint. Moving on here on the side of the BGA, you have an open. An open is a good case scenario for head-in-pillow defect. What do I mean by that? It means that the open you don’t have a connection, no matter what the ball was sitting high, the pad is here, and you don’t have any connection. It’s a best case scenario from head-in-pillow from because you don’t have to worry about this on and off connection. It’s always going to be off.

Dr. Bill Cardoso:              Splattered is something that happens when… usually signifies too much heat when you reflow and the bubbles that can be air or flux instead of balls, you just pop and splatter solder throughout the BGA. I mean, if you just look at this piece of solder and say, “What’s the big deal? Just a little piece of solder inside my BGA’s not a problem.” Yeah. It’s not a problem except that as you… it might lodge between the power and ground, for example, VCC and ground causing a short and causing a mess, malfunction. So you can’t… it’s not a reliable assembly and should not be allowed.

Dr. Bill Cardoso:              Moving on here. Solder mask problems are not straightforward to recognize. A solder mask issue… So let’s go back. What’s a solar mask? So you start with a PCB. You have your board, and the board has copper traces and contacts, and land pads where the BGA’s going to sit on. Now you have a solder pad and you have a trace that connects to the solder pad. Now, if you just put a little solder on the solder pad, the solders going to run on the trace. And as we said earlier, you need that volume of solder so that you can keep the separation between the PCB and to BGA. So to avoid solder from running through the trace of each pad, we need to put a mask on top that’s called solder mask.

Dr. Bill Cardoso:              So this mask that covers all the traces and just leaves the pads for each BGA ball. And what happens is that if the pads for some reason are… if the solder mask is defective, that solder is going to run through to the copper traces, and as a result you’re not going to have enough solder volume to keep the separation between BGA and the PCB. And as you have the discontinuing, this inconsistency of solder volume, you might end up with opens or even head-in-pillow. So that’s a big problem. It can be a defect on the PCB manufacturing itself, but it can also be excess heat in your reflow profile which caused the mask to lift. You have the peeling of the mask, and that allows solder to go like under a rug and potentially cause a lot of problems on that assembly.

Dr. Bill Cardoso:              Voids are… it’s the Holy Grail of BGA inspection. That’s the very first thing you look for are voids. Too much voiding is a problem. Why? Because this… so what are voids? Voids are areas of the solder ball that are occupied by either flux or air, right? So it’s imagine a bubble of air, a bubble of a flux inside the solid object. So that bubble is, if it’s big enough, as the assembly goes through a temperature cycle, as things get hot and cold… imagine your car in the morning and then in the middle of the day. Can go from 30 Fahrenheit to 90 Fahrenheit in one day, which is a very aggressive temperature cycle.

Dr. Bill Cardoso:              Well, that bubble has a coefficient temperature expansion. It moves, expands and contracts as a certain rate. The solid object around it, which is a solder ball, has a different CTE. And this guy here, this bubble is going to expand faster. So as things heat up and contract, you can imagine that now this solid object is going to be moving as well. And guess what? You don’t want to have this thing moving, because they’re going to create cracks. And eventually you can separate the ball, shear the ball away from the BGA or from the PCB.

Dr. Bill Cardoso:              So voids are in some situations hard to avoid, but they should be minimized. And there are different standards. IPC 610 specifies a percentage of voiding on the BGA that you can have as a functional what the class of product you have, class one, two or three, which is a function of how reliable that assembly has to be. You can imagine that if you are manufacturing a toaster that’s going in your kitchen, the requirements are very different from a reliability standpoint then if you are making a toaster that’s going to go on an airplane or a submarine. So different electronic examples have very different reliability requirements, and voiding is a part of that reliability composition. The shape of the ball, as you can see here is a good indicator off wetting off the ball. So wetting, I don’t know if you guys… just go over. Wetting is the ability of a solder to connect and run on a specific metal. In this case, solder onto the pad of the board.

Dr. Bill Cardoso:              You want to see a shape that is round or oval. That’s what we’re looking for on a BGA inspection. An odd shape like you see here in the image represent that… and as a result, you ended up moving on top of the solder mask and creating this odd shape. And finally you have a missing balls. So missing balls, as you can imagine from the name, is when the ball is just not there. And when you are attaching the BGA onto the board, the BGA has the balls already onto each one of the pads. And you can either put flux on the board or you can stencil some fresh solder onto the board. And then when you mate the BGA onto the board, you reflow the solder wet, and you connect. Situations like this often happen when the balls on the BGAs get knocked down accidentally because mechanical shock, because from picking up from the tray and putting on the board, in that process some of the balls got dislodged.

Dr. Bill Cardoso:              We also have seen a counterfeit BGAs where in the process of counterfeiting the BGA, the BGA’s removed, it’s cleaned. And when new balls were attached or reflowed onto the BGA, the wetting wasn’t done properly. So the ball doesn’t really stick to the BGA and ends up falling fairly easily, causing a situation like this. So we have a whole session of this fireside chat about counterfeit detection, and we’re going to cover that at that time. But for now, keep in mind that if you see missing balls, it shouldn’t happen. Really shouldn’t happen. If it’s a brand new BGA, you shouldn’t see any missing balls. If there are missing balls, it’s very likely this BGA has been reworked at some point. By the way, feel free to leave any questions on the chat. Or if you want to raise your hand, you can get unmuted and I’ll be more than happy to address your questions.

Dr. Bill Cardoso:              All right. So one of our pet peeves here at Creative Electron is that when people are designing boards, design electronics, these really should think electronics design in three dimensional way. Why? Because if you think about electronic design or when you’re designing a board, if you think about how the board is going to be inspected with an X-ray, it can save you a lot of money. Let me explain why, because as you add complexity to your… and overlap between the top and the bottom layer, as you add more complexity to the board, the complexity of the equipment inspecting the board is also going to grow. So you can go from a simple 2D X-ray system that’s going to cost you X to a two and a half D system that’s going to cost you more than two and a half X, to requiring a three-dimension, so computer tomography for a higher complexity.

Dr. Bill Cardoso:              Let’s go over some of the examples where we’re going to show you how small changes on the design of the board can save you a lot of money in the inspection of the board once the board is built. So here’s a good example. It’s a 2D, two dimensional straight down X-ray of a ball grid array. And I want to point your attention to these balls here. You see this one here, that one there, this one, that one, this one. So you have several locations where decoupling capacitors, these components here are capacitors. By the way, how can you tell apart capacitors and resistors on an X-ray? Capacitors have a very dense dielectric, and as a result they are very radiopaque, which shows very dark on an X-ray image. So these dark components here, these are capacitors.

Dr. Bill Cardoso:              The light ones on the other hand, resistors, or ceramic resistors are very light and not radiopaque at all. So they show basically transparent on an X-ray image, and you can tell they’re there by looking at the fillet they leave on the pad. So that’s a resistor, resistor, capacitor, capacitor and so on. So anyway, to minimize noise on the BGA, on the circuit on the BGA, you need to add a capacitor. Basically a low pass filter on your power supply to make sure the power supply has enough… too much ripple. And to minimize the inductance or the impedance between the pad on the BGA to the capacitor, what you do is you try to place the capacitor as close as possible to the balls, to the contacts.

Dr. Bill Cardoso:              And what people end up doing, what designers end up doing is perfectly aligning capacitors onto the balls, which makes it very hard to expect with a 2D X-ray, because you look here, you can’t tell if this is a short or a capacitor. So it makes life very, very hard for the X-ray. Now with a 2D X-ray, you can’t make a determination if these are legit shorts or just a capacitor sitting there. So what do we have to do is to go ahead and tilt the board to get us a nice perspective, two and a half D. Now, this is a more expensive X-ray machine. You need more time. You need the right angle, better trained operator to make that determination. As you can see here, let me go back and forth between those two images. And you can see here is that people look at this, it looks like a big capacitor hiding several balls there. So as we tilt, you can see there was one short that was being hidden by that big capacitor.

Dr. Bill Cardoso:              And you can actually see that some of this, as we tilt, these are legit shorts that are on capacitors. So it’s very important that if you can, what we’re suggesting here is that you shift to offset those capacitors if possible, outside the BGA, and bring traces in, or at least shift them away from the ball just enough that we can separate what’s a ball or a solder ball, and what’s a capacitor. So we looked at what a 2D inspection is straight down view with the X-ray imager. We saw what a two and a half D, which is tilting the sensor or tilting the table, the stage, to give you that perspective view, a tilted view of the image. So what’s 3D inspection. What is a computed tomography? So there’s a wide range of ways that you can collect this tomographic or 3D, three dimensional perspective on an X-ray image.

Dr. Bill Cardoso:              This is a fairly straightforward one that is very intuitive to understand. So let’s go with this one for now. So imagine you have three objects. You have these blue objects, the pink and red. So you have a square, a circle, and a triangle. And this can be the ball of the BGA, the PCB, and a capacitor on the other side of the PCB, and the bottom layers of the same assembly. Now, let’s look at perspective one here. So this arrangement, the sensor and the source are going to make this movement. One is going to rotate clockwise. The source rotating clockwise, the sensor rotating counter clockwise. And in that arrangement you have many tilted views off this depth stack, the same stack of objects.

Dr. Bill Cardoso:              So in perspective one, the square is on the top, the circle is in the middle, and the triangle is on the bottom here. That’s the perspective on the X-ray sensor of those three objects. As we move the source and the sensor, you can see how the square, circle and triangle separate differently. So they do this dance and they separate and come back together. And that’s a function of the projection of the source in the sensor onto that stack of samples. That’s pretty straightforward. Now, since, you know… you don’t know where those things are. You don’t know where your sample is. But you do know where your source is and your sensor. You know where your imaging training is at all times and exactly what angles and what projections your imaging at. And as a result, you can by doing some simple arithmetic on each one of those images, you can separate the top layer to the bottom layer of your board.

Dr. Bill Cardoso:              And in this example, we have a QFP here on the top layer, and a resistor on the bottom layer. And that fillet of the resistor is masking a potential short between those two pads of the QFP. So by applying this 3D tomography, you separate the top and the bottom to have a clear idea of the top side and the bottom side, thus clearing this arrangement from a potential defect. So to make it very straight forward, these are the three different X-ray modalities available for inspection. 2D, which is a straight down view of your sample. Two and a half D, so that’s when your tilt and you have the perspective view. And finally, three dimensional where you get the full volume of the sample that you can move around, decompose, and provide with a larger insight, and complexity of the X-ray system grows as the number of dimensions grow. So with that we’re going to open for any questions now. We’re getting to the top of the half an hour here. Any questions?

Dr. Bill Cardoso:              So we have a question here from John, which is… Okay. Yeah. So he’s asking, what is half a dimension? Well, half a dimension doesn’t exist? This is a made up term that the X-ray industry came up with several years ago to differentiate between 2D and 3D right? So you call 2D is a straight down shot of the sample, 3D is a volumetric interpretation where you have X, Y, and Z in formation. Dimensional Z information, not only density Z information on your sample. So instead of pixels, you have voxels on a 3D representation. And half a D is a tilted view. So it’s more for marketing term than anything else?

Dr. Bill Cardoso:              All right, we have another question coming up here. This one’s from Dave. Does it matter where the voids are inside the ball? That’s a good question. Yes, it does matter. As you can see here, with a 2D imaging you can see what voids are, but you can’t really tell… you have a solder ball. You can’t really tell if that… imagined that this is solder ball and that a golf ball is the void. You can’t really tell if the void is on the top that interfaces with the board or at the bottom, if it interfaces with the BGA. You don’t really tell with 2D image, you’d be looking at a straight down shot. So by doing a two and a half view, you can tell that for example, this void is right on the edge and right on the interface with the board.

Dr. Bill Cardoso: So that’s a very bad place to have a void. And even if the void is below the threshold set by your quality group or IPC, whatever other standard are you going to use, even if it’s below that threshold of 20, 25%, that’s still a fail. It has to be rejected and reworked. So this is all the time we have for today. Thank you so much for participating and attending. Don’t forget next week, we have another Fireside Chat with the Xperts. Check our website to see exactly what the topic is going to be, but it’s going to be a Wednesday, 10 o’clock Pacific time. Glen. Thanks again for participating. And I’ll see you guys next week. Thank you.

Fireside Chat: The X-Factor – How X-ray Technology is Improving the Electronics Assembly Process (Part I)

Posted by Charles Wells

Creative Electron is excited to launch our Fireside Chat with the Xperts series with “The X-Factor – How X-ray Technology is Improving the Electronics Assembly Process (Part I).”   There’s none better than Dr. Glen Thomas to guide us as to how and why X-ray inspection has become such an important tool in electronics manufacturing.

This presentation offers a terrific overview of SMT manufacturing and how X-ray inspection informs every aspect of an SMT lines effectiveness, and helps to improve efficiency as well as quality.  Check out the full line-up of upcoming Fireside Chats here.

 

Transcript:

Dr. Bill Cardoso:           All right. Good morning. This is the first of our new series Fireside Chat with the Xperts. This is a new set of online presentations that we’re going to give. Since, with the 2020 coronavirus pandemic, we haven’t been able to travel and give these presentations live. So, we’re going to be doing that from our homes now as we enjoy the shelter-in-home lockdown. So, the first conversation we’re going to have is a generic presentation we’ve given a couple of times that it will cover a lot of the background on X-ray inspection. Some of the applications on how X-ray is used on a daily basis in our industry to improve manufacturing.

Dr. Bill Cardoso:             So, today’s presentation, as you can see here, we have quite an aggressive schedule. We’re going to cover quite a few topics. That’s the reason why we split this conversation into two sessions. So, we have today at 10 o’clock Pacific time and next week, or next Wednesday, we’re going to have the second half of this presentation. We’re going to keep on … We’ll basically cover everything we missed. We didn’t have a chance to cover today. And every Wednesday at 10 o’clock, after that, we’re going to have sessions of half an hour. We’re going to keep it short and to the point, so that we can fit in our busy, busy days. Even though we’re home, we are still quite busy.

Dr. Bill Cardoso:             So, I’m really happy to introduce you, today, to Dr. Glen Thomas, who is our VP of Technology. He is a guy who doesn’t really need a lot of introduction. He’s been doing X-ray inspection for 20 plus years, even though he’s super young, he’s been in this since high school, right Glen?

Dr. Glen Thomas:            Pretty much.

Dr. Bill Cardoso:             And, so today, we’re going to … Glen’s going to give a presentation. Next Wednesday, I’m going to cover some of the topics that we didn’t cover today. And with that, you have the floor, Glen.

Dr. Glen Thomas:            Thanks.

Dr. Bill Cardoso:             Let me give you control so you can run the presentation yourself.

Dr. Glen Thomas:            All right.

Dr. Glen Thomas:            How do we change, how do we change slides?

Dr. Bill Cardoso:             Let me give it to you, right now.

Dr. Bill Cardoso:             You should be able to do it now.

Dr. Glen Thomas:            What changes it? I guess we forgot to go over this earlier, didn’t we?

Dr. Bill Cardoso:             I know. Well, you just let me know and I’ll change the slide. Yeah.

Dr. Glen Thomas:            So, essentially, what we see here is we see a typical SMT line, right? We have the screen printer, SPI, pick and place, reflow and AOI, as well as X-ray at the end. This would be the ideal setup. Some companies will make a choice, whether they want to go with AOI or X-ray and ideally, you would want both. Most of the time, they will choose between AOI and X-ray depending on their needs and how many problems they have. Typically, with the X-ray and AOI, they both compliment each other. They’re not really inclusive one or the other, but most customers tend to pick one or the other. So, that’s just the way that beast works. Okay, next slide.

Dr. Glen Thomas:            So, essentially, you get a lot of defects with this manufacturing process for bottom components, bottom terminated components, and in solder joint integrity, in general. Essentially, with X-ray for the SMT line, what we’re looking for is solder joint integrity. We want to eliminate the excess solder. We want to, which would be solder bridges and in insufficient solder. And, in that insufficient solder, you’re looking at voiding and you’re looking at lack of solder joint integrity due to not having enough solder or solder paste, solder masks. So, in these three areas, you have quite a few different defects that would fall under those three areas. In X-ray, we’ll actually find that it excels in most of the areas, especially the insufficient solder. Okay, next slide.

Dr. Glen Thomas:            Again, we can look at misalignment, polarity and missing components, and this is where AOI does a really great job. And X-ray, it’s just a matter of being a plus. We can find misalignment, we can find polarity, in most cases, and we can find missing components, as well. But that’s not the main focus for X-ray, that would be more of a function of AOI. Okay, next slide.

Dr. Glen Thomas:            This is where AOI fails and X-ray excels, is in the voiding, the bridging, the solder balls, excess solder and insufficient solder. We can go over gull wing components with insufficient solder, later in the presentation, but X-ray excels at these five key areas of SMT inspection. Next slide.

Dr. Glen Thomas:            Solder joint measurement data, collected during X-ray test, can be used statistically to analyze, identify manufacturing drifts, trends and other processes, right? So, essentially, what we’re saying is we can use X-ray. We can look at a solder joint. We can determine based on what characteristics the solder joint has, we can go back and we can pinpoint areas in the process that are most likely to cause that issue. So, the X-ray will be able to give you an idea and monitor multiple processes and be able to show you drifts. So, if you notice a drift in the process, you will use X-ray to look at that and you can see a drift and you can actually go back and fix your process on the fly while you’re still producing shippable product.

Dr. Glen Thomas:            One of the key problems that we see a lot of is people will use X-ray only as a last resort and not necessarily manage their processes. So, what they do is they use X-ray as an, “Oh no, we have a problem when we can’t ship product,” right? Smart contract manufacturers and smart OEMs, use the X-ray to look at the process consistently, so that they can see drifts, fix the drifts before they actually have a problem. Okay.

Dr. Glen Thomas:            Okay. Basic principles of X-ray, X-ray, whether it’s medical or industrial all uses the same principle, right? We use an X-ray source, typically for small fine pitch components. We would use a five micron source or better. In some cases, if you’re looking at magnification on very small components, you will need a much smaller focal spot than even the five micron. Five micron focal spots, three micron focal spots are pretty much the standard in surface mount inspection in solder joint integrity these days.

Dr. Glen Thomas:            We always need a sensor. The old days, sensor was film. We had some digital detectors and back in the day, they were pretty crude. We considered them digital, but they were actually just a phosphorous and screen with a digital or a CCD camera. And then we went to image intensifiers. They became the de facto standard for many years in industrial X-ray and in surface mount technology.

Dr. Glen Thomas:            Now flat panel detectors are the standard. It’s rare that you’ll find an X-ray system with an image intensifier. And, if it is using an image intensifier, it’s going to be based on the application and the need, rather than just a general imaging device. X-ray sensors with digital detectors excel. And there’s a lot of reasons for that. The main reason is the digital gives us a better gray scale contrast, more spatial resolution and we’re not doing as much conversion. The image intensified systems have analog 256 gray scale. And then we pick that up with a camera and there’s a lot of inefficiencies. Then we’ve got to convert it analog to digital. So, you have some more loss in the inefficiencies. So, digital detectors, flat panel detectors are going to be around and they’re going to stay around there. They’re actually beneficial for companies when they do image processing. Okay.

Dr. Glen Thomas:            As far as … Let’s go back to one other slide, the back slide. As far as image processing, back in the day, image processing was pretty straightforward. We took an analog image, fed it out to a monitor, and we would look at it and you would use a dry erase type marker or a crayon and draw on the actual monitor. If you saw an issue, right, you would, we had three or four times frame averaging, and then we used last image hold. So, you would do a last image hold rundown. You would circle the problem, run down and get the engineer and show him the problem. Then we went to image processing, which. was kind of straightforward.

Dr. Glen Thomas:            It was about the late, mid to late eighties, we had some image processing available. There were only, really, three companies that were building image, processing computers at that time. And they were kind of, kind of archaic compared to what we can do with image processing today. But that also allowed us to use digital printers or actually thermal printers at the time.

Dr. Glen Thomas:            So, now we could save that image, right? And it became much more useful as time went on. Image processing today is actually the key to image X-ray imaging for all types of components, because we have the ability to do some algorithms. We can automate the process. We can save data and use that data to monitor the process. So, essentially anybody can build an X-ray system with an X-ray source and the detector. The secret is really having a beneficial software to analyze and understand the information that you’re getting from the X-ray machine. Next step.

Dr. Glen Thomas:            Why do we need X-ray? Back in the early, or, mid to late eighties, some bright engineer decided that bottom terminated components made a lot of sense, made the boards smaller, gave them a lot more inner connections. It just made sense to make a bottom terminated component. What they forgot about was, what we’ll talk about later, is the ability to inspect that and to actually verify that your process is working.

Dr. Glen Thomas:            So, essentially BGAs revolutionized the X-ray industry for X-ray imaging and surface mount technology. Up to that point, we would, we built a few systems, but most X-ray systems at that point were to look at wire sweep and we would look at components and we would look at bare boards for inner layer registration. It didn’t do a whole lot of X-ray for solder joint integrity, but the BGA changed that whole concept, and actually built the industry that we see today. Next step.

Dr. Glen Thomas:            So, if you take a look at a BGA, you’ve got a lot of balls underneath the solder joints. Those solder joints, there’s a lot that can happen in there. You have solder paste applications, you have solder masks, you have the component itself, placement of the component. You have co-planarity issues with the board or with the component. So, you have a lot of different issues that can happen on a BGA. In a perfect process, you put the BGA down, you apply some heat to it, the BGA self aligns and everything goes well.

Dr. Glen Thomas:            But it’s, the process of placing a BGA sounds fairly straightforward, but it’s actually quite a complex process that requires more or less perfect execution prior to soldering the BGA to the board. So, if he can take a look at the X-ray image, you see that we see some solder balls. So, essentially, those solder balls will give us a great indication as to whether we’re have a fairly decent connection to the substrate, right? In this ball in this image, you can see that we have some balls with no voiding. All the sizes of the balls are pretty standard and circular. So, it’s a fairly decent X-ray image of a BGA. And that’s what most people strive for in the industry. Next one.

Dr. Glen Thomas:            QFNs, QFNs are interesting, as well. Instead of the standard ball, we have a pad and we would need to mount or solder the components to that pad on the substrate. It’s a different process. Some of the same processes, as far as solder paste application, placing the component and your general placement of the products, pretty close to a BGA. One of the problems you have with QFNs is you have a lot less mass as far as the solder paste. So, your profiles can get a little bit weird as far as heat. And, they’re close to impossible to inspect with AOI. Same as a BGA.

Dr. Glen Thomas:            As far as the solder joint integrity on it, this image, those all look pretty decent. It’s not too bad. And when I say decent, what you’re looking for in this component versus a BGA is you’re looking for the solder fillet, the grounds, darker areas around the circumference of each connection. And in this case, if you had a bad solder joint, you would literally see instead of a nice rounded shape, then the nice flow from light to dark, you would see just a straight line. It should be easy to pick up. But those do look like pretty good solder joints. So, the difference between BGA inspection and QFN inspection is essentially we’re looking at solder fillets more so than the solder balls themselves. Okay, next.

Dr. Glen Thomas:            Right here, perfect example of a QFN. Essentially, what we see is, we see some voiding underneath the ball, the pads, in a few places, but essentially, we have a straight out open. There’s no solder fillet at all. And by solder fillet, you can look at the connections and you can see the black blobs all along the bottom. And by inspecting a QFN, you’ve got a couple of voids in there, but for the most part, you have two opens, essentially. They’re pretty easy to pick up and pretty straightforward. AOI would most likely could pick that up. Because it would be probably outside the component a bit on this component, but at what AOI wouldn’t be able to tell you is if you had solder flow up under the leads and you had a nice solder flow, but X-ray will give you that indication that you have solder flow. Because you can have a solder ball on the outside of that pad and outside of that pin and still not have solder flow or a real connectivity.

Dr. Glen Thomas:            And we can also see that all of those balls are somewhat round. When solder melts, it likes to puddle, and it will puddle in a circular fashion. When it’s cold and it doesn’t have a good solder connection or the solder paste application is not actually working well. What you’ll get is you’ll get a lot of angular solder joints. And, in solder joints, angular is always bad. It means that you have a cold solder joint and you have a lack of adhesion. So, even with AOI, you might be able to pick that up.

Dr. Glen Thomas:            There’s been all kinds of different concepts with visual imaging, a lot of silly scopes where they would try to look down under a BGA. And it just makes no sense for a production environment. Looking under each BGA is silly. It’s just pure folly because you can only see two or three rows in efficiently. And with that, you really can’t get an overall view of the solder joint, the circularity, the solder fillet. You really can’t look at BGAs with visual, using a scope with some type of fiber optic input. Next step.

Dr. Glen Thomas:            Void measurements, that’s the key, one of the major keys to the ability to monitor your process. You can look at the percentage of voiding. You look back at that voiding. Most voiding in BGA happens at the screen printer, your solder paste integrity. If you open a bucket of solder paste, you plop some in your printer and you go at it in the morning. You’ll get some really nice results. As time goes by, somebody might leave the lid off of that solder paste. The, the factory heats up from nice, cool morning to a later in the day, it gets a little warmer or in some cases it gets colder in the building.

Dr. Glen Thomas:            You will have a change in your solder paste consistency, and you might get some contamination in your solder paste. Voiding is also an indication of maybe your substrates weren’t clean. You have metalization issues in the substrate. They were shipped and they became, corroded to a degree while they were shipped. So,, the voiding will tell you a lot about your process, but it mostly goes back to the introduction of voids in your solder paste. Essentially, you don’t have a void until to you apply some heat to the board and run it through the reflow oven. And then, any impurities, in any air or any junk that you may have in the solder joint, will … Those gases will expand. And that’s what creates your voiding.

Dr. Glen Thomas:            For BGA voiding, you typically can do about 25%. That’s about usually the number that most people will consider a good solder joint. If you have less than 25% voiding, in all cases in BGA, you don’t want that voiding to penetrate the circumference of the ball. What that does is, it gives you some nice edges and will create a vibration crack over time and create issues. So, voiding will let you monitor your process pretty efficiently.

Dr. Glen Thomas:            And as far as voiding on that, one of the processes that you would have is to generate the report. Generating reports are really key to being able to monitor your process from shift, day to day, from shift to shift or from product run to product run. You put away a dirty stencil and you came back and ran the product again, and somebody forgot to clean the stencil. So, now you have a bunch of opens or you have a bunch of bridging, and that’s all based on the fact that your stencil was probably clogged or dirty, things like that. So, you can really apply X-ray to your process and get some good information. You can also generate a report for later reference and use it as a learning tool. Next slide.

Dr. Glen Thomas:            Solder voids and LED assemblies. Solder voids and LED assemblies are the death to an LED. Solder voids are a major problem for LED substrates. The substrate to the LED attachment is critical to remove heat. So, if you get a lot of voiding in your LED, you’re going to get a lot of warranty returns. And in most cases, if you have a lot of voiding, you just put a $5 bill in each box and call it a day. This is going to cost you money in the long run. So, the X-rays give you the ability to look at those solder defects and fix the problems.

Dr. Glen Thomas:            Most of the problems with LED is just the basic concept of how they’re attached and the power that’s applied to them, essentially. You can always tell when someone really doesn’t understand LEDs, when you buy a flashlight and it has a two pound heat sink on a AA flashlight. It’s, they’re trying to pull the heat away because they had no clue how to do it mechanically with the substrate to LED attachment. Okay, next slide.

Dr. Glen Thomas:            Let’s see where we go. Essentially, it’s what you’re looking at right now. Led inspection, major flaws in the process and major voiding. Essentially, the LED process is the same, in most cases, to a BGA inspection. We’re looking for excessive solder, lack of solder and primarily, in this case, voiding. The major difference is we’re looking at a square or rectangular pad instead of a BGA pad.

Dr. Glen Thomas:            So, the LED voiding calculations are important and they use a different criteria than a BGA void would. We’re interested in, not only the amount of voiding, percentage wise, as compared to the pad, but we’re looking at the largest void as well. As well as in this case, you can see a lot of extraneous BGA ball or not BGA, but solder balls underneath the component, as well. So, there’s quite a few different problems with this component as it’s mounted. Okay.

Dr. Glen Thomas:            Another one, essentially here, we’re just looking at voiding in the attachment, it’s pretty straightforward. It’s pretty simple. This one we would use a rectangular instead of the BGA ball. Voiding is pretty easy to pick up, but also we can see a lack of solder fillet, as well. That’s why you’ve got a nice rectangular, outer edge around this component. It doesn’t have a real nice solder fill. This could be a solder mask issue, more so than a solder paste issue.

Dr. Glen Thomas:            Same thing, same concept. I found a new love for the color contrast. Over the years, that was a worthless environment. You would take a nice, back in the day, 256 gray scale image, and you would apply some color to it and you would bring it down to 32 colors, pretty much worthless. The new algorithms that we’re doing, and the ability with computer power, as well as monitors, the whole concept and digital detectors with thousands and thousands of gray scale, allow us to do a much better job with color.

Dr. Glen Thomas:            At one time, pseudo color was just used to impress the VPs up in the office and to impress the customer to a degree. The advantage of colors and the pseudo color is that we can tie a color to a specific gray scale value. And it makes for a much faster inspection routine. In this case, we’re looking at the solder joint itself, in red, and then we’re looking at the traces in blue. Following traces in an X-ray is a really tedious task because of the multilayers.

Dr. Glen Thomas:            So, having the ability to take a layer or a density and assign a color to it, and then follow that color, it makes a lot of sense. If you were training a person that has no concept of X-ray and you tell them that you want to see red in all of the solder joints, that’s one way to train in an operator pretty quickly, and it works. But in this case, we’re applying some other filters, which gives you a contoured effect as well. So, it really makes those voids stand out. All right, next one.

Dr. Glen Thomas:            Automated X-ray, essentially, in this case, what we’re doing is where we were looking at an automated X-ray system, which essentially, comes in, component comes in, we take an image, we instantly measure the voiding and then move on to the next part, pass or fail. And that gives us the ability to provide quite a bit of data on the products. The future of X-ray imaging is going to be automated X-ray. Where we eliminate the operators concepts of what is actually a good solder joint and what’s not. One of the problems with operators and with manual X-ray is, it’s all dependent on the person, what they consider a good X-ray, for one, which means the settings of the machine can change drastically.

Dr. Glen Thomas:            Monitors, you look at a monitor, one person sees a perfect image. Other person says, “No, it needs a little bit more contrast or it needs less contrast.” So, there’s all these inefficiencies when operators are involved in X-ray. They decide that it … There were some medical studies years ago that they took 50 or 100 radiologists, and they showed them exact images. And they came up with 50 or 100 different concepts of what that image was. Not only was acceptable or not, but what the outcome for the patient was, and they brought those same radiologists back two weeks later and gave them the same images. And even the radiologists couldn’t agree on what was a good image and what was not, and what was passable. So, taking the operator out of the equation is key to getting decent and consistent results, to be able to monitor your process. All right, next one.

Dr. Bill Cardoso:             Glenn. So, we got you to the top of the half an hour, 10:30. I know time goes by. So, we can start to on a BGA inspection next week, but I wanted to open for questions for about five minutes. If people have any questions they want to address now, and of course, they’re always welcome to email us or text or a tweet, Facebook, LinkedIn, Instagram us. We are on every platform and happy to address. So, anyway, open to the floor, you can raise your hand if you have any questions. Otherwise, we’ll wrap up the video today and start again with our next Fireside Chat on Wednesday with again, with Glen and I in this same Zoom meeting, same time. So, it sounds like we’re going to take questions offline today, Glen. Thanks again for the great presentation. Thank you all for attending. And I’ll see you guys again next week. Thanks so much. Bye bye.

 

Fireside Chat with the Xperts

Posted by electron

One of the many things this global pandemic disrupted was our Lecture Series. In a regular year, we give between 30 and 50 presentations worldwide. Needless to say we’re not doing that nowadays, so we moved this content online.

Welcome to Fireside Chat with the Xperts!

The idea here is to present free, live, fresh, non-commercial, relevant information about x-ray inspection. We will host the Fireside Chats in Zoom, so you’ll be able to ask questions during the presentations. We’ll keep these Fireside Chats to 30 minutes, every Wednesday at 10AM PDT starting April 22nd. You will need to register by emailing info@creativeelectron.com with your request of the presentation you’d like to attend. You can attend them all – but we’ll limit attendance so we can have a Fireside Chat – not a webinar.

This is a unique opportunity to have access to experts and professionals who are usually too busy designing and building x-ray systems. Since they are bored at home, this is the perfect time to chat!

Register today

April 22: The X-Factor – How X-ray Technology is Improving the Electronics Assembly Process (Part I)
Hosted by Dr. Glen Thomas and Dr. Bill Cardoso

April 29: The X-Factor – How X-ray Technology is Improving the Electronics Assembly Process (Part II)
Hosted by Dr. Glen Thomas and Dr. Bill Cardoso

May 6:Autonomous X-Ray Inspection of Medical Devices
Hosted by Carlos Valenzuela

May 13: Are X-Ray Machines Safe?
Hosted by Mariem Ortiz

May 20: How AI is Changing the Way we Make Things
Hosted by Jonathan Jimenez

May 27: Robots and Cobots – the Good, the Bad, and the Ugly
Hosted by Griffin Lemaster

June 3: Getting the Best Out of Your Legacy X-Ray Machine
Hosted by Dave Phillips

June 10: Can Radiation Damage Electronic Components?
Hosted by Dr. Bill Cardoso

June 17: 10 Ways to Find Counterfeit Electronic Components Using X-Rays
Hosted by David Kruidhof

June 24: Identifying Voids on Bottom Terminated Components (BTC) Assemblies with X-ray Analysis
Hosted by Carlos Valenzuela

July 1: To PM or not to PM: Is that Really the Question?
Hosted by Dave Phillips

July 8: Q&A with the Xperts
Hosted by Dr. Glen Thomas and Dr. Bill Cardoso

Register today!

Events in January/February

Posted by electron

Events in January/February

MedTech Monday

January 27
Location: The Hills Hotel,
25205 La Paz Rd. in Laguna Hills, CA 92653
Speaker: Carlos Valenzuela
Title: Autonomous x-ray inspection of medical devices

IPC APEX 2020

February 4-6
Location: San Diego Convention Center
111 W Harbor Dr., San Diego, CA 92101
Booth 1107

Tue, Feb 4: 1:30 PM to 3:00 PM
I-03 INTERACTION: I4.0 – Inspection as The Currency of The Smart Factory
Moderator: Dr. Bill Cardoso
Location: 33C

MD&M West 2020

February 11-13
Location: Anaheim Convention Center
800 W Katella Ave, Anaheim, CA 92802
Booth 2494

Mountain View Reverse Engineering Meetup

Posted by electron

Join us at the Mountain View Reverse Engineering Meetup at Alice’s Smokehouse.

At this special event, our own Bill Cardoso will be arriving with our famous Creative Electron mobile x-ray lab van! Bring things to x-ray! The more interesting, the better…

7:00 – 9:00: mingle

7:10 – 8:00: “X-Ray Tips and Tricks Counterfeit Detection” by Bill Cardoso

8:00 – 9:00: mingle, mobile x-ray van demo! Then, some loitering in the parking lot for good measure!

Special thanks to Scotty Allen for helping facilitate this!(https://www.youtube.com/channel/UCO8DQrSp5yEP937qNqTooOw)

See you there, get there early and join the fun.

The X-ray Van is on the road!

Posted by electron

The X-ray Van is on the road to BIOMEDevice 2019 in San Jose

Once again, the Creative Electron X-ray Van is on the road, this time to the Biomed Device Show in San Jose, California. Our own David Kruidhof will be visiting customers along the way and then representing us at the San Jose McEnery Convention Center on December 4th and 5th.

Biomed Device San Jose offers an expansive showcase of cutting-edge technologies, contract services, and educational content, spanning an array of topics from digital health to minimally invasive devices, to surgical robotics, while offering a full spectrum of practical solutions to today’s engineering challenges. Meet industry experts, make new connections, and see the latest tech discoveries in action all under one roof.

https://biomedevicesanjose.com/

LA/Orange County Expo & Tech Forum Thursday, November 7, 2019

Posted by electron

Creative Electron is proud to attend the LA/Orange County Expo & Tech Forum Thursday, November 7, 2019

Join us at the SMTA LA/OC conference held at The Grand Event Center – 4101 E Willow Street, Long Beach, CA 90815.  This exciting event hosts electronics engineering and manufacturing professionals seeking to improve processes through best practices and real world solutions. SMTA offers exclusive access to local and global communities of experts as well as accumulated research and training materials from thousands of companies dedicated to advancing the electronics industry.

On the road with the x-ray van…
At the show!

Visit us to discuss how we can help your company with quality  control and counterfeited detection solutions.

Creative Electron at the 25th Anniversary of the MDM event in Minneapolis, MN.

Posted by electron

Creative Electron is honored and proud to attend the 25th Anniversary of the MD&M conference in Minneapolis. Medical Design & Manufacturing (MD&M) connects companies with top industry experts. What sets MD&M Minneapolis apart is that it’s actually five complementary events in one. The definitive event of the med-tech industry, MD&M Minneapolis empowers its attendees to access expertise across the supply chain. The heart of this show is not only connecting companies with innovators in med-tech, but also giving access to industry leaders in 3D printing, biocompatible materials, plastics manufacturing, robotics, and automation, to name a few.