Raj S,
A couple of reasons come to mind.
1. If more than 12 layers but 1.6 mm thickness, then thinner cores will
have to be used and these cost more and have less dimensional stability-so
maybe more registration problems and yield loss.
2. Thinner cores are harder to process and the fabricators machines may
not be adapted to thin-cores.
3. To keep the thin thickness, they would have to use a single piece of
prepreg and maybe their process does not support this
Happy Holden
Mentor Graphics



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[DC] Layer stackup complexity






I am designing a board of 1.6mm thickness. When determining th
Hi All,

I am designing a board of 1.6mm thickness. When determining the layer
stack-up I was asked to keep within 12layers for a greater yield in
manufacturing. But I have seen 16layer stack-up for same thickness.
Reasons I can think which can control the stack-up are, the impedance,
placement complexity, routing requirements(delay length matching) and
power planes (at the board level). I was wondering what stops to go for
more layers if the prepreg and core with different thickness are available
in market.

Anyone has any insight what problems could rise in manufacturing on
increasing the layers?

Thanks in advance for your suggestions.
Raj.



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