Investigating Analytical Tools for Testing Cleanliness with Foresite's Eric Camden

Estimated reading time: 23 minutes

Camden: Well, there are some head scratchers. Like I said earlier, we have a general idea when we see a failure mode; we start by looking at topics A, B, or C, in that order. And then sometimes if you get down to J, K, L that's where it gets to be kind of frustrating and when you've got to start looking outside the box. We've tested everything that we know to test. Then you really must start using your knowledge of the assembly process, going all the way back to prefab manufacturing, to figure out where to find this failure mode.

And sometimes—we started doing this 12−13 years ago—we really started focusing on bare fab innerlayer cleanliness that's causing issues. The miniaturization of boards, blind vias, buried vias, things like that. If there's ragged drill we found you can shorten the space between an innerlayer ground plane and a via, and now if you don't have a good solid insulative space between that via and that ground you can have innerlayer leakage that you never see on the surface of the board. You may or may not be able to detect it even with the best of X-ray. We started looking at cleanliness of innerlayers because we saw some leakage event. And it's not always CAF, the historical CAF, but there are other ways to get that kind of innerlayer shorting that we hadn't seen before then. We try to adapt when we've run the gamut and come out with nothing at the end of it. Then we see that it was one of those issues that we saw where we started focusing on the innerlayer bare board cleanliness.

Goldman: You keep going back further and further in the process.

Camden: Yes, until you get back to a handful of sand. Was the sand contaminated that we used for this wafer that was used for this chip? Sometimes you have to go all the way back to the beginning.

Goldman: And there's always something to learn.

Camden: There seems to always be something to learn, especially in this industry because there's always somebody trying to push the envelope. Embedded devices is where we're headed next—you get handed something that looks like a bare card that has all the resistors and capacitors built into the board itself. I think there's only so many places we can go from here. When you think back to printed wiring boards, when everything was hand wired and wrapped, to looking at your cellphone today. That would have filled 10 server rooms for the same kind of power just 30 years ago. We've made leaps and bounds, and when you start talking about aerospace and implantable medical, these devices must be pristine. And we really enjoy being on the forefront of some of these technological advances where some of these customers are coming to us and saying that they want to make sure that they’re putting this out there right the first time, because it is mission critical. Sometimes it is literally life or death with some of the stuff we work on. We must be sure that what we're giving is really good information. And so far, obviously we're still open, so it's a great place to be.

Goldman: I would venture to say your business is only going to increase by leaps and bounds as we go into 5G and beyond. We think electronic devices have exploded now, but I think there's going to be a much bigger explosion, shall we say, of electronics everywhere. And some of that like automotive is going to need to be super reliable. There is going to be a whole lot more that you're going to inspect.

Camden: Right. Then you start thinking about networks, not just wireless charging but over the air kind of charging for your cellphone, things like that. You hear those hints and rumors out there that your phone will always be charged because it's just in the air. There are things out there that we're very much looking forward to and hopefully we'll play some part in that in providing reliability data.

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