Issue link: https://iconnect007.uberflip.com/i/1460418
MARCH 2022 I PCB007 MAGAZINE 13 that will drop the insertion loss. In fact, I'm starting to look into the copper foil suppli- ers to see what they're doing. Recently, I cre- ated a copper foil selection guide based on roughness data from suppliers' datasheets to better understand how it impacts the perfor- mance and cost of the PCB. When many of the suppliers started showing better SI, that's when we found out the copper changed but not the resin. Another topic related to material is panel size, which doesn't affect insertion loss or reli- ability but does influence cost. If an OEM really wants to save even the last penny, we will opti- mize to a specific panel size. Some laminate suppliers have certain large sheet sizes that are beneficial for material utilization rate. Johnson: at's where the manufacturing floor comes into play and material utilization and every square centimeter of board that you can use is a benefit to the margin at the bottom line. Mok: Right. Usually this is the area where our PCB purchasing department really gets involved. We look at utilization to find a panel size that min- imizes panel waste to get the lowest per-piece manufacturing cost. Johnson: Eddie, thanks for the insight. is truly is a two-way conversa- tion nowadays, on per- formance, availabilit y and cost, isn't it? Mok: It definitely is. My pleasure. PCB007 Johnson: It's a nice, holistic look; all those are factors in a material selection. Mok: Different members of the team will have different requirements based on their job. e SI guy wants something specific perfor- mance-wise, but the commodity guy is watch- ing the pricing. e program manager is pri- marily concerned with keeping to the sched- ule. We get them to just draw a line and start somewhere. It just opens another dialogue because they're just not familiar with all these new materials. We like to offer customers alter- native solutions to improve SI performance at the most cost-effective way. As the materials manufacturers develop iter- atively improved materials, they are under- standably careful not to violate UL by chang- ing the resin system. To do that, they switch to a better copper foil. at's an easy thing