When a bare PCB is subjected to an electrical test, the ultimate goal is to find out any short or gap that is present in the circuit. Openings are commonly called interruptions in the circuit that hamper performance; while shorts are unwanted connections between individual circuits or networks. Electrical test attendance is immensely useful when you have a multilayer printed circuit board to be checked.
Generally, there are two basic types of electrical tests done on a simple PCB: Flying Probe and Universal Grid.
Flying probe is test method is one of the most difficult because there are several ways to configure the machine to test the PCB. Normally, this category of electrical tests can be divided into two subcategories: Direct and Indirect.
Direct test method is applied with an explicit voltage and current to measure the applicable endpoint nodes. This is done primarily to determine the strength value. For example, if the resistance value is less than the benchmark, then a pass will be evidenced. Instead of testing one network with another, the direct isolation test will perform some kind of adjacent methodology where voltage and current are applied to a network and adjacent ones are recorded for leakage currents.
Indirect test method uses the comparison of signatures, in which each network is not checked individually, but compared to a main set of values.
Universal grid an accessory is needed to transmit the current from the machine base to the PCB node. This process produces less resistance to the connection because most universal grid machines are able to do so through the calibration process. Characteristically, the universal grid tester performs pattern scanning twice; once for continuity and once for insulation tests, which allows parametric testing. The universal grid is one of the most comprehensive and comprehensive tests because it detects all types of layers and short layer defects.
The PCB industry is constantly evolving and adapting to the latest developments in technology. As a result of these technologies, OEM requirements have also advanced. Typically, PCB manufacturing companies are informed about the specific type of electrical test that a part needs to pass. The test usually occurs during the process of ‘quotation’ or ‘acquisition’ of the printed circuit board.