1. Warping: To save time, Some Production Planner, often eliminating the hot air leveling process. directly pass pcb to E-test process, if not go through the hot air leveling process, sometimes warpage is greater than the test equipment allowable range, it will cause pseudo open in the test rest. Thus, the heat level process can not be eliminated, also SysPCB requires FQC testing staff make the warpage measurement before the flying probe testing.
2. Soldermask: According to the analysis, some product with many open issue during E-testing, it is because the through holes are blocked by soldermask. So when we make the electrical testing net for flying probe machine, the testing net should try to avoid the switching via holes.
3. Silkscreen: Many PCB manufacturers will first printing the silkscreen then arrange E-testing, if the Silkscreen position registration slightly shifted or precision of silkscreen if not good enough, small surface pad and holes may be covered by part of the silkscreen. Therefore, in order to avoid pseudo open by caused silkscreen during E-testing.
For PCB with a fine pads, small via holes (Φ <0.5), high-density fine line, we should first do the electrical test then printing silkscreen.
Advantages and disadvantages of flying probe test:
1. Test pin can be easily damaged
2. Test speed is slow
3. Can Test PCB with 0.05mm Pitch or even smaller
4. No E-test mould(Bed nail fixture) costs
5. Can not conduct HI-POT test, there is risk of testing high density multilayer PCB.
