Re: [PEDA] Board warpage?

[Harry Selfridge]

It isn't an odd number of PAIRS that causes problems - it is an odd number 
of LAYERS.  There are some advanced fab techniques that can reliably 
produce boards with odd number of planes or odd number of signal layers; 
however, there are very few fabs I would trust to do it.  You can sometimes 
get away with odd number stackups, but it will eventually bite you in the butt.

Six layers is a common balanced stackup - provided there are an even number 
of planes, and even number of signal layers with reasonably distributed copper.

At 01:56 AM 7/21/04, you wrote:
SNIP
Some say that an odd number of layer pairs can cause problems, indeed we 
had problems with 6 layers at first, though we now use 6 layers to great 
success.  Problems with that were caused by bad process control, not the 
design (though the manufacturer tried to blame design at the time!!)
SNIP 


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