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36 DESIGN007 MAGAZINE I AUGUST 2024 dangerous when a PCB designer steps naively into unfamiliar areas and does not know where to look. I have been bitten many times by the cost adder, but I've learned from my mistakes. Now, I'm offering a few free doses of cost adder anti-venom. Species: Serpens Materia (Material Cost Adders) While most think of PCB material as simple glass-epoxy sheet stock or FR-4, PCB laminates have expanded into very advanced, brand- name, trademarked product lines that target specific performance and operational require- ments for advanced PCBs. When a PCB design layout goes to produc- tion, be wary of Serpens materia. Fabrication drawing notes must contain a material specifi- cation through which the PCB is made. Global PCB fabrication suppliers prefer simple glass/ resin or polyimide laminates that can be read- ily procured from multiple sources. But oen, PCB designers make the mistake of specifying brand-name materials or part numbers when it is not required. Other designers even declare "no substitutions." Designers who proceed in this manner without advanced understanding and justification are reaching dangerously into the den of Serpens materia. When their design moves to volume quantities, they will most certainly experience a painful strike from this adder with swelling of cost and necrotic prod- uct profit margin to follow. e anti-venom for Serpens materia is mod- est but powerful. It must be injected directly into the design fabrication note-specifying material. Aer dosing, a basic material note's brand name, cost swollen specification can heal by stating: "Materials: Laminated, glass base, epoxy resin type FR-4 series or equiva- lent per IPC-4101 with Tg >/= 130°C and a Td >/= 300°C electro-deposited copper foil. Nominal base (starting) copper thickness for all layers shown on stackup detail." Species: Serpens Processus (Process Cost Adders) ere are many ways to process a single fea- ture on a PCB. For example, a board edge can be routed out, punched out, V-scored, laser cut, or even cut with an abrasive water jet. e way the designer lays out the shape of the board geometry will allow or eliminate many of the available processes. If a board outline maintains a rectangular shape, it can tolerate almost any process and allows the supplier to use V-scoring, which can be very cost-effec- tive. But rounding the corners to eliminate a sharp edge means an additional process step of routing to form the rounded edge. With rounded corners and straight edges, a PCB can be processed with a combination of V-scoring and routing at a cost for the additional pro- cess. Rounded features on a PCB outline are notorious hiding places for Serpens processus because of the additional process of routing and associated machine time or shiing the processing to a tab-route solution requiring mouse bites.