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86 PCB007 MAGAZINE I JULY 2019 Shaughnessy: Are you talking about copper, FR-4, and any sort of surface? Kidd: Yes. We'll have some applications in me- tallics, polymers, and in composites as well. Bien: That's a good point, though. It's particu- larly difficult to control surface chemistry and match surface chemistry between dissimilar materials. It's very easy to bond metal to met- al, and it's pretty easy to bond composite to composite, but metal to polymer, glass to poly- mer, and those material interfaces are more challenging to create to promote adhesion. Shaughnessy: What are the biggest takeaways from your talk? Kidd: Namely, the sensitivity of this surface. As Alex mentioned, we have a monomolecular layer that we're trying to control, and that lay- er is highly sensitive to contamination events. Contact contaminants from the manufactur- ing process—things like upstream process aids from stamping or anything left over from any wash process from a chemical etch bath— have a huge impact. Or perhaps you've had a change in your supply chain where supplier X used chemical X, and now supplier Y is using chemical Y, and all of a sudden, you have more random failures or successes, and you don't know why. It's drawing attention to those small chang- es in a process that can affect that monolayer that we're trying to adhere to. We'll mainly be talking about contamination, how to look for it, how to characterize that, using various surface characterization techniques—such as FTIR, XPS, and contact angle measurements— and surface activation and detection of coat- ings. The main takeaway is to increase the awareness of the sensitivity and how you can change—negatively or positively—that sur- face, even unknowingly. Shaughnessy: With one small thing having a large influence on the process. Bien: A small change in the process creates a snowball effect downstream. Kidd: Exactly. Think about a fingerprint. If you put a fingerprint on the surface, that's 1,000– 10,000 molecules thick. If you try to stick something to it now, you're not sticking to the surface; you're sticking to the chemicals and the oil from that person's fingers. That kind of sensitivity is important. Shaughnessy: You measure down to the ang- strom level? Kidd: Yes. Bien: A couple of nanometers is the thickness that we want to be sensitive to. Shaughnessy: And you get to see it on a moni- tor? Do you get a read-out? Bien: It's a digital output. Kidd: We have a couple of machines and prod- ucts called the Surface Analyst that will allow inspections to be made. We have an automated solution that will deposit the droplet, analyze the droplet, and give you a read-out. It can mash all of the data together to give you a sta- tistical output that is significant for whatever manufacturing process you are trying to look at—batch to batch and all that jazz. Bien: We employ every surface technology that's in the marketplace. We're a process de- velopment and optimization house as well as a manufacturer of products that allow compa- nies to measure and control their surfaces, and we see this as a hole in this industry. There's a It's particularly difficult to control surface chemistry and match surface chemistry between dissimilar materials.

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