Warping degree standard and test methods

According to the American IPC - 6012 (1996 edition) rigid printed circuit board > > identification and performance specification for surface installation, PCB allowable maximum warping and distortion, and other various board for 0.75% allow 1.5%.
This is better than the IPC - RB - 276 (1992) improve the surface installation requirements.
Printed circuit board At present, various electronic potential manufacturing/remanufacturing curling degrees, whether permission or multilayer, 1.6 mm double thickness, usually 0.70 ~ 0.75%, many SMT, BGA board, the requirement is 0.5%.
Part of the electronic factory is inspired to raise the standard wrpping degrees 0.3%,
Test method of GB4677.5 wrpping degrees - 84 or in accordance with 650.2.4.22 B IPC - TM -.
The JingJian PCB on the platform, set the test needle is inserted into the warp degrees biggest place to test the needle diameter, divided by the PCB collaring length, just can calculate the PCB curling degrees.