PCB Surface flatness? 1

[Carlsberg73]

My question involves how to ensure the surface of a PCB maintains its flatness when its fabricated. Currently we are trying to enure that our PCB surface are as flat as possible, this is because our product that will be attached to the PCB is very sensitive to surface flatness.

Would love to get suggestions as my background is in mechanical but i need the info to assist me in designing the part that sits on the board.

Regards

 

[MacGyverS2000]

Make sure you have an even number of layers, particularly power layers (they have a lot of copper on them). In high-power areas where bus bars might be used, make sure torquing the bars down doesn't warp the board... set a spec.

Is there a specific problem you're seeing?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[VEBill]

I've seen many PCBs with "PCB stiffeners". These are either soldered in place, or mechanically attached. They're intended to ensure that a large PCB doesn't warp over time.

 

[sreid]

After soldering (say in a convection oven or reflow machine)the hot PCBs are very flexible. They must be held "Flat" while cooling.

 

[IRstuff]

If flatness is critical, you're probably better off with an interposer that has a conformal interface to the PCB. PCBs are not precision structures, and they also have fairly unconstrained thermally induced behavior.

TTFN

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