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10 DESIGN007 MAGAZINE I DECEMBER 2024 Feature Q&A with Kris Moyer Kris Moyer teaches several PCB design classes for IPC and Sacramento State, includ- ing advanced PCB design. His advanced design classes take on some really interesting topics, including the impact of a designer's choice of advanced packaging upon the design of the layer stackup. Kris shares his thoughts on the relationship between packaging and stackup, what PCB designers need to know, and why he believes, "e rules we used to live by are no longer valid." Kris, tell us how advanced packaging can impact stackup design. What challenges do designers need to be aware of? Kris Moyer: With advanced packaging you usually need to use HDI or UHDI technol- Effects of Advanced Packaging and Stackup Design ogy. is usually means sequential lamination. With sequential lamination you need to select materials that can survive multiple lamination thermal cycles. When we were discussing advanced packag- ing and stackup design recently, you said, "The rules we used to live by are no longer valid." Expand on that a little bit. As I mentioned, your selection of materials is now further restricted by the need for mate- rials that survive multiple lamination cycles. Additionally, since we are adding layers one at a time and need plating on all layers, not just the outer layers, the copper design is now more difficult. Also, since we are adding lay- ers one at a time, we can now have some select