Comprehensive Understanding Of PCB E-Testing

Flying probe E-testing, just as its name implies, uses a “flying” test probe, e.g. the test probe moves from this test point to other test point on the basis of instructions given by a specific software program written for the tested PCB. No custom fixtures are required, so if used on an assembled PCB, it can also be called fixtureless in-circuit testing. Therefore, it is high cost performance for prototypes and low-medium quantities production.
Originally, the flying probe tester was only used for prototyping PCB testing, but now it has become the regular for bare board testing (including testing the short circuit and open circuit between the copper conductor features on the bare PCB). The main different electrical parameters of resistance between the two nodes.
However, the development of FPT has been slow to measure capacitance and inductance in addition to resistance. This makes them suitable for PCB assemblies as well. Not only that, but there are several reasons to finally adopt them to test filler panels:
First, as mentioned earlier, they are more cost-effective for small batch production.
Second, they don’t present as many accessibility issues as ICT testers using pogo pins; FPT probe points are smaller compared to pogo pins and are able to reach much smaller test points than pogo pins many pads. For ICT tests, test points are specially designed, which is rarely required for FPT tests.
Third, testing content are easy to finished flexiblely as the movement of the FPT probes which controlled by a software program that can be easily transformed. Also, it is much easier to adjust for changes in probe landing position through software changes.
Fourth, since flying probes can directly access component pins through automatic probing without the need to build test points specifically, it provides better test coverage compared to traditional ICT testing.

If you want to study more about other types of inspections such as AOI, ICT and son on, pls read our post on PCB Assembly Inspection Report Formats. It includes an overview of each inspection test, process parameters and condition requirements.
The FPT is equipped with a camera for checking component polarity. They are becoming a more popular test way, especially with the ever-increasing miniaturization of electronics.

To be able to test board assemblies in FPT, we need to create an FPT program for testing. We usually create such program off line on computer,just like pick an SMT program with an SMT programming application.

Phase difference measuring device:
A phase difference measuring device (PDM) transmits a high frequency signal between one end point of the reference line and the signal line section, and measures the phase of the signal at the other end, thereby estimating its phase difference. This will reduce isolation testing within the network.
High Pressure Stress Test (HVS):
High-voltage stress testing is performed for high-resistance insulation defects not detected by PDM. We perform HVS by applying high-voltage pulses between signal lines to detect high-resistance defects.So as to do it with fast time.
Micro short circuit detection:
Next is micro-short detection. Sudden application of high voltage during isolation testing may cause burnout of parts containing micro-shorts. This failure can be avoided by gradually increasing the voltage before applying the low voltage. Sometimes high-resistance shorts between multiple layers of a circuit board have the characteristics of semiconductors and capacitors. These defects can also be detected by the reversal of the polarity of the high voltage.