Thick PCB materials

[jimmykk]

Hi
We are designing 400x400mm size PCBs that Need to be 3.5mm thick. I understand that normal 1.6mm thick PCBs have thickness tolerances of +/-10% that is 0.1mm. But in our case of 3.5mm thick PCBs we cannot tolerate this 10%(0.3mm) thickness variation from batch to batch(or PCB to PCB) and can maximum tolerate 0.1mm. So i was wondering if there is any other material other than FR-4 recommended for these thick PCBs or is it more in the hands of PCB manufacturers to Control these thickness variations?

 

[KlausST]

Hi,

my recommendation: contact your PCB manufacturer. They best know what is possible.
They may control overall thickness, but they may also be able to (partly) mill down to the expected thickness.
They maybe laminate 2 x 1.6mm material with 0.3mm prepreg....
The manufacturer will tell you...

There even may be base material with standard thickness of 3.5mm. (Check modified design rules for thick material)

Klaus

 

[marce]

PCB materials have improved greatly over the 36 years I have been doing designs (especially Z axis CTE). Now you can get what you want, as Klaus says, the first stop is your PCB manufacturer. Expect to pay a bit more when you go outside the norms...
FR4 is a generic term these days, have a browse round ISOLA and other laminate manufacturers for the available choice of materials, there are many, not just variants of FR4 , but more exotic (and expensive) solutions.