I have seen different specification given to pcb house for pcb fabrication.
What is the guidelines regarding
the thickness of copper for different layers for best performance and cost
effective.

1) For example for a 2/4 layer pcb,examples of some of the spec. are :
   2 layer pcb : a) FR4 material with 1/2 oz copper
                  b) FR4 material with 1oz copper

   4 layer pcb : c) FR4 material with 1oz copper in all layers
                  d) 1/2oz copper clad FR4 plate up 1oz, inner layer use 1oz

Any differences between a) & b)  or c) & d) ?

2) I have read from "somewhere" that it is better to use smallest distance
spacing between power & ground plane
in the inner layer for lowest power impedance. What is this smallest
distance ?

3) How about core and prepreg, do you'll usually specify their thickness
also ?

Thanks in advance for all contributions given.

Best Regards,
EILEEN ONG (R&D Dept.)
Paradise Innovations (Asia) Pte Ltd
Email : mailto:[log in to unmask]
Web: http://www.paradisemmp.com