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As the size of electronic devices continues shrinking, more PCB designers consider embedding components in the PCB itself. This not only reduces the skyline of the board, but has the added effect of increasing the board’s overall reliability.
IPC’s Kris Moyer teaches design techniques for embedding components, and he’s noticed an upswing in his students’ interest in embedded component design. We recently spoke with him about embedding component design: best practices, pros and cons, and when it makes sense for designers to start embedding.
Andy Shaughnessy: I understand you’ve had a lot of interest in embedded components in your design classes. What are students curious about?
Kris Moyer: Some interesting student questions have all been related to embedded components, especially about the viability of the embedded for high reliability. They ask, “How viable and reliable are the embedded resistors, cavities, and so on for military applications or stuff that has to go into space?”
When they ask, “Is this an additive process?” I respond that it's a subtractive process for embedded resistors. There are a lot of processing, reliability, and design questions. There's the trade-off question, too: At what point does it make more sense to embed resistors vs. just shrinking down to, say, an 0105? Is it better to take the cost into the embedded process?
Shaughnessy: I think some people are wary of the cost of getting involved with embedded components, even though it can save money in the long run.
Moyer: That's one of the trade-offs. There's an initial design and manufacturing cost to get into the embedded design techniques. But once you're in, you will see improvements in the long run. You won't have as many failed boards; you can reduce size and item count. On the other hand, without embedded resistors, if I have to make enough room on my board, even using double-sided placement, to have 1,000 physical resistors on there, how much bigger does my board need to be? How much more does my product need to cost, and what about the weight? If I can take off 1,000 resistors, even at a penny each, that’s still $10 per board.
Nolan Johnson: When does it make sense to go with embedded?
Moyer: One of the biggest trade-offs when you’re considering embedded is actually the silicon geometry. The problem is that as the silicon has decreased, the rise times are faster. While you're transitioning from zero to one or one to zero, and you're either rising or falling, you're actively driving the transmission line. Therefore, you don't necessarily need to worry about reflections or crosstalk. When you exceed that distance, now you have to worry about it. As the rise times have gotten faster, the distance the signal travels is now smaller, to the point that for some leading-edge boards, rise times were nearly 100 picoseconds.
To read this entire conversation, which appeared in the February 2024 issue of Design007 Magazine, click here.
