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Page 78 of 113

JANUARY 2023 I PCB007 MAGAZINE 79 This is one of the technology areas where you see similar processes coming together. solder—basically solder tops that you then use to connect chips during packaging. To give you some more details on the redistribution layers, we offer, for example, very high purity copper chemistries like Spherolyte® UF 3, which is one of the big players in the market because it can form the smallest lines and spaces. We are talk- ing about down to even one micrometer lines and spaces nowadays. Additionally stacking of RDL layers goes hand in hand with certain requirements like filling of features, where we offer market leading performance. e redis- tribution layers are responsible for connecting structures within the plane—connecting the different areas of the chip. Historically, when we talked about pillars, we were talking about solder application. For larger structures you had the tin-silver or tin-solder bump directly on the pad. But due to miniaturization, it's more favorable if you have smaller pillars with a little solder bump on top. You have to consider electro- chemical deposition chemistry with the pil- lars, which are mostly made of copper; quite oen, a nickel layer is used as a diffusion bar- rier, but because Spherolyte® UF 5 is so pure, we don't necessarily need this nickel layer for our processes. Some customers still want it, though, because they've always had it. On top of that, you have mostly tin-silver deposits, or sometimes tin, depending on the customer's requirements. Starkey: ere used to be two distinct technol- ogy areas: PCB and semiconductor/packaging. Nowadays, the two are getting closer together, and I think advanced packaging will be a big area of future development for the PCB side. Do you have any comments on the merging of these two technologies? Helbich: I totally agree; I also see that hap- pening. I think this is one of the advantages that we as a company now have, of course; having a long successful history in PCB and being successful in semiconductor packaging gives us the opportunity to follow this trend from both sides and opens the field for in depth study. Starkey: You've been able to offer expertise in both areas. In this case, it's just a question of how to reapply existing knowledge, rather than trying to build knowledge in areas you're unfamiliar with. Helbich: Exactly. You see this in technologies like our electroless deposition processes. In the semiconductor area, you oen have metal pads—under-bump metallization—which are basically contacts for wire bonds, similar to bonding processes like soldering. On the PCB side, for example, you also have these clas- sic ENEPIG stacks, such as nickel, palladium, gold stacks. is is one of the technology areas where you see similar processes coming together. Of course, the requirements differ in some aspect. is also brings me to our second pillar: electroless deposition. In this area, we offer a variety of nickel processes. We needed a range of options in this area because requirements vary across applications; for example, phos- phorus content might be a consideration, or the requirements for high temperature appli- cations, and so on. en we have a palladium process; here, purity is key for reliability, and we are one of the leading companies when it comes to pure palladium deposits. We're work- ing together on this with the big players in the power semiconductor field. en there's the gold layer, which requires different processes

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