Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

PCB warpage

Grace Chua


PCB warpage | 14 October, 1999

Hi there, I have quite a number of problematic bd due to warpage problem. I would like to know the method on how to measure PCB warpage, thus to decide on the dispositon of these boards. Another question, can these warp bd be rework/fix. Is there any thing I need to take note if the bd can be rework/fix for PCB and PCBA level. Thanks in advance for the advise and Best Regards, Grace

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Re: PCB warpage | 14 October, 1999

Grace, You can get the information you need from IPC. Measuring board warpage is covered in theie 610B manual. It will let you know the what can be reworked and what cannot.

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Re: PCB warpage | 14 October, 1999


As deifned in IPC 7721 Procedure 3.2 Bow and Twist Repair

"Bow and twist after soldering shall not exceed 1.5% for through hole PC boards and .75% for surface mount PC boards. The bow and twist shall not be sufficient to cause difficulties during placement, soldering and testing operations. Before dispositioning PC boards with bow and twist as scrap, keep in mind how the PC board is mounted in its final destination. Keep in mind "form, fit and function" without jeopardizing reliability."

To see a copy of the repair method you can visit

Jeff Ferry Chairman - IPC Repairability Committee

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Dennis O'Donnell


Re: PCB warpage | 14 October, 1999

With loaded boards, warpage can be removed by placing the assembly in a wave solder conveyor pallet as you would if you were going to wave solder the assembly. Place board and fixture in a Blue M forced air oven at 90 C for 30 minutes. Let cool to room temp and remove from fixture.

With bare boards, place in a heated press at 100C for 15 minutes and let cool.

Determinre the cause of the warpage. It could be from excessive heat at some point in the assembly process. If the board grain patterns were not pressed together in the right direction during fabrication, this will also cause warpage.

Go to: for solutions to your circuit board rework and repair problems.

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Mark Phinney


Re: PCB warpage | 15 October, 1999

Earliar we had problems with board warpage, Much of our problem was due to imbalances in the copper on oppisite layers in brief on a 8 layer board the copper on layer 1 should = the copper on layer 8, 2=7, 3=6, 4 = 5. We added copper to some layers to balance them and boards don't warp no more. I assume the boards you want to rework are surface mount ( including leadless parts ) I wouldn't want to use a rework that didn't allow to solder to reflow for fear of introducing stress to component connections.

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