What does a PCB tester do?
Unlike a function test (FKT), the PCB test is a function-independent test. This means that the actual function that the PCB will have later does not play a role here. Here, a flying probe test (FPT), for example, is used to check the physical properties in the needle bed adapter.
How can defects be found?
- Even if the produced PCB appears to be free of defects to the naked eye, it must still be subsequently checked electronically for defects. This can be done, for example, with an ICT (in-circuit test) or finger tester. Depending on the measuring device, various functions or measurements are then available. A distinction is made here between Z-diode, varistor, short-circuit and continuity measurements, impedance and inductance as well as resistance measurements.
- Another possibility to detect a placement error is the so-called analysis scanner. With this, the operator is shown a photo of the current DUT and a photo of a good template in rapid alternation. A difference between the two images can thus be quickly detected with the naked eye.
- In an automated optical test, the PCB is photographed with cameras and checked for defects via software.
- X-ray-based AXI enables the detection of solder defects at component joints. This is made possible by a higher atomic weight of the solder material compared to the other components.
New production of printed circuit boards
A printed circuit board or PCB is initially completely electrically insulated (raw circuit board made of epoxy resin and glass fabric) - copper conductor tracks are then etched onto this. In the case of multilayer printed circuit boards, individual layers are connected to each other using so-called via holes (Vertical Interconnect Access). The components are then applied to the board in the subsequent assembly process. Here a distinction is made between two processes:
- SMD (surface-mounted-device). The components are soldered directly onto the board using SMT (surface-mounting technology).
- THT (through-hole technology). The components are soldered through a hole in the board.