Test speed is an important factor to choose the right test device. Nail-bed test device can test thousands of point in one time, and flying probe can only test 2 or 4 points in one time. Furthermore, nail-bed test device will consume only 10-150usd for single side, it also depends on the complexity level of PCB. But flying probe will need over 1 hour or even more time to test the same of work. Shipley(1991) has ever explained that even mass production PCB manufacturer will blame flying probe test for its low processing rate, but it is a good choice for low volume and complex PCB manufacturer.

For bare board test, we have dedicated device, one more optimized way for cost is universal device, although this device originally could be more expensive than dedicated device, but it is cost can be offset by installation. Refers to universal grid, PCB with component lead and SMT stand grid is2.5mm. so the test PAD should be greater or equal to1.3mm. for1mmgrid, test PAD should be greater than0.7mm. If grid and probe is so small and fragile that easy to damage. Therefore we had better choose above2.5mmgrid. If universal device and flying probe device can be applied simultaneously, can ensure both commercial and precise measure for high density PCB, another way is conducted rubber test device, this technology can detect those points deviate grid. However, PAD height can vary after HASL which will bring trouble for test point connection.

Normally three different inspection should be committed:

1 bare board test;

2 incircuit test;

3 functional test;

Comments are closed.