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50 DESIGN007 MAGAZINE I SEPTEMBER 2025 TA RG E T C O N D I T I O N Rethinking the PCB Stackup Recipe by Kelly Dack , CIT, CID+ Marie Antoinette is attributed with saying, "Let them eat cake," but historians now agree she likely never said it. It was probably revolutionary propa- ganda to paint her as out of touch with the starving masses. Yet, the phrase still lingers, and oddly enough, it applies to the world of PCB design. Today's designers, in their well-intentioned pur- suit of signal integrity and performance, are writing stackup specifications that resemble high-end pastry recipes. But are we forgetting the realities of offshore fabrication and the limitations of the PCB "bakers" who have to make these designs work? Let's revisit the classic cake metaphor for stackups and explore why the recipe approach is falling flat, and how we can return to performance-based design that satisfies everyone at the table. The Layer Cake Stackup Metaphor The layer cake analogy for PCB stackups isn't new. Designers often describe the stack as a baked cake: cores and prepregs as cake layers and sticky frosting, held together through pressure and heat. It's simple and helpful until it becomes too specific. When designers call out exact materials—brand names, resin systems, weave styles—and forbid any substit- utions, they've crossed from "baking" into "gourmet patisserie." The result? A tasty metaphor gone stale in the fab shop. Five Basic Ingredients of a Stackup Let's get back to basics. A standard cake recipe has five essential components: flour, eggs, liquid, leavening agent, and flavoring.