Issue link: https://iconnect007.uberflip.com/i/1515637
FEBRUARY 2024 I DESIGN007 MAGAZINE 13 embedded components, you now have to cal- culate all that, and there are various trade-offs because it's now a material vs. component situation. ere's a lot of information that's needed: power dissipation, voltage drop, cur- rent rating, current density, etc. Shaughnessy: How do you test a component embedded in the board? That sounds like it could be problematic. Normally, when I'm designing for test, I want to have 100% of the nodes available with a test point. But if I start putting formed resistors in line with a trace on an inner layer, I no longer have 100% unique component testability. I only have chain testability. Let's assume it's a QFP. e QFP comes out, goes through a full through-via, and gets to an inner layer. en we attach our resistor to the via, and downstream from the resistor we get to another point. Now I have to go from the pin of the device through one embedded resis- tor, or maybe two embedded resistors before I hit another via that comes back to the surface for testing those two or three resistors. So, there are DFM challenges when you're doing embedded. Johnson: How do today's CAD tools handle embedding components? I can speak to Altium, which does not directly support the embedded workaround that I teach my students. Altium supports the cavi- ties—the embedded as physical parts and cavi- ties. When making and defining that footprint, you can say, "Here are my surface mount pads, and my solder mask." Altium allows you to put the footprint on layer three or whatever of the board, and you can define cavity fea- tures. What it does not support right now is formed resistors, but you can get around that manually by adding the layer definition. I can define those as my mask layers for the resistor opening in the resistor definition itself and just add those two component layers. So, there are workarounds for that. Shaughnessy: Is there anything else you'd like to add, Kris? I'm glad to see my students interested in embedded components. is is something that every designer must be aware of because even in run-of-the-mill commercial digital prod- ucts, the silicon guys keep making silicon so small. Every PCB designer needs to be able to deal with signal integrity, and the only way we can deal with signal integrity moving forward is with embedded resistors. e traditional techniques we used are becoming not quite obsolete, but certainly ineffectual because of the rise time issue. Embedding components is something that every designer will have to do. It might not be on a daily basis, but they must be at least cognitively aware that they need to consider this process. Shaughnessy: Thanks for your time, Kris. ank you all. I enjoyed it. DESIGN007 Kris Moyer