How to prevent the PCB warping? This is the most improtant in the PCB manufacturing preocess.

1. Why is flat circuit board requirement

In the automation plug line, if PCB isn’t flat will cause mispositioning, components can not plug in to the board of the hole and surface mount pad, and even crashing automatically installed machine. After components installed on board, component pins are difficult to cut neatly. Board can not be fitted to the chassis or the machine’s outlet, so, board assembly factory is also very troubled.

2. Warpage standards and test methods

According to the U.S. IPC-6012 (1996 Edition) <<Rigid Printed Boards and performance specifications>> for the maximum allowable surface mount PCB warpage and distortion of 0.75%, other 1.5% of various board permitted. Compare to IPC-RB-276 (1992 Edition) to improve on the requirements of surface mount PCB. Currently, the electronic assembly factory agree with, regardless of double or multi, 1.6mm thickness, is usually 0.70 to 0.75%, and for SMT, BGA’s board, demand is 0.5%.
 
3. Warping board processing:

As in our factory, PCB in the final test will be 100% flatness inspection. Failure of the board who will be singled out, into the oven at 150 degrees and bake under the weight of 3 to 6 hours, and under the weight of natural cooling. And relieving the board out, check in for smoothness, this would save parts of the board, some boards need to bake for two to three times the pressure to leveling.