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Since I've ever only done rather simple boards: when would you actually need 16 layers? How complex of a component are we talking about when it would be feasibl
by Etheryte 10y ago
Since I've ever only done rather simple boards: when would you actually need 16 layers? How complex of a component are we talking about when it would be feasible to use that many layers?
- honkhonkpants 10y agoUsually you might need this if your software fails to route with "only" 14 layers.
- jacquesm 10y agoYou might be able to route it but that doesn't mean it will work due to crosstalk and then those additional layers will come in handy as ground.
- DigitalJack 10y agoAnything with RF sensitivity can benefit from isolating ground layers. You can use layers for managing thermal effects. Vertical isolation of signal groups to reduce cross-talk. Horizontal space restrictions. And then of course, signal count and density. Many FPGAs have a thousand or more pins.
- toomuchtodo 10y agoYour comment reminds me why it always pays to consult with an expert, pennies up front versus real dollars later.
- stephen_g 10y agoWe find 4 and 8 layer boards are the best for most of our RF designs (depending on frequency, complexity, etc.) - more layers than that and your dielectric layers start to get too thin and then your tracks have to be super narrow to hit a 50 ohm impedance... But of course, that also depends on what type of substrate you're using, etc. But for complex digital boards, 16 (or more) layers is common.
- nibnib 10y agoModern BGAs will often need that many layers just to break out all the signals.
- kabdib 10y agoGoogle something like "bga escape routing" -- I found one chip that needed 12 layers pretty quickly.
- revelation 10y agoOnce you use a BGA with X balls in Y rows and Z columns with so and so pitch the minimum number of layers needed quickly goes way up. If you use any kind of BGA you will want to start with 4 layers just for signal integrity.