harry eaton wrote:
The world has changed quite a bit since the birth of 'pcb': With very high density, very high pin count chips, it is simply topologically impossible, even with micro-vias, to fit all the necessary connections into less then 4 or perhaps 6 inner routing layers, no matter how much you try and how much routing space you can 'waste' on the outside. Add to that 2 power planes and 2 outer layers (which on very high density SMT is pretty useless for routing, anyway), you quickly end up with a total of 10 copper layers.I wonder why they get so hot that they need fans when there are no power connections. My point is it's usually possible to route a board with far fewer layers than are actually used.
Commericial products like high-end PC graphics boards routinely use 10 layers now-a-days.
Another issue is that from an economical point-of.view, it makes total sense in many low volume applications to spend less time doing smart routing, and instead go for 2 more layers. 10 and to a certain extent 12 layer PCBs have now become common and economical (from a total economy point of view). Of course, the possibility/necessity of more ground planes and better signal integrity is another argument for more layers in certain applications.
16 layers should be "enough for everyone" for some definition of 'the future'.Since I now know there are some fairly high-end-complexity users out there I will extend the copper layer support to 16 soon
Egil
