Electrical testing of printed circuit boards

PCB electrical testing

Electrical testing is one of the main objective methods for controlling the quality of printed circuit boards . This method allows you to determine the smallest gaps in the production process - breaks, short circuits, surface resistance inconsistencies.

Basic methods

With versatile equipment - Flying Probe

The "Flying Probe" or "Flying Probe" equipment is a specialized hardware and software system designed to test PCB circuits for wire breaks or short circuits. MDA - defect analyzer - allows using probes to determine manufacturing defects of mounted printed circuit boards.

The design of the equipment is different: there are horizontal, vertical devices with automatic loading. There are also various variations in the number of probes (from 2 to 4 on each side).

Note that in the process of checking by the "Flying probe" method, the manufacture of expensive additional equipment is not required, which significantly reduces the cost of checking the quality of the PCB. With small batches, the absence of the need to create adapters helps to reduce the time spent on electrical testing.

Using adapters

Electrical testing by the adapter method is carried out using equipment that requires additional individual equipment - analyzers created for the required specification and configuration of printed circuit boards.

This method is the most accurate, but at the same time and overhead (since it requires the creation of adapters with individual technological parameters). It is also necessary to take into account the fact that during serial production, the total time for checking one board using adapters is much less than electrical testing using the Flying Probe method.

Testing features

Electrical testing is performed at the final stage of PCB production (etching). During testing, the electrical connections of the contact areas, points of the output of circuits are checked, deformation of the conductors / vias, the possibility of a short circuit are excluded.

As a result, manufacturing defects are identified and eliminated - products in which there is no correspondence between working photomasks and spatial and electrical characteristics. Rejection is in progress.

Testing can be done within 1 day. Product inspection time will vary depending on the number of layers, optional tooling, and PCB specification.

As for the quality control method, it is defined quite simply:

• if the total area of ​​printed circuit boards is not more than 500 dm ² , then the most profitable testing method is the Flying Probe;
• if the area of ​​the boards is from 500 dm ² , then it is economically more expedient to choose the adapter method.

Advantages of PCB electrical testing

• The ability to detect damage that is not visible during visual inspection - low insulating resistance, hairline closure of the tracks, the presence of microcracks on the surface, etc.
• Reducing the overall manufacturing time of devices, by reducing the debugging processes of all their components.
• Identify electrical inhomogeneities in insulating materials and create comfortable / reliable operating conditions.
• Increase the operating life of the printed circuit board and the reliability of work.
• In addition to conductor errors, electrical testing checks the quality of the insulating layer. In this case, it is possible to test circuits by the "High-Pot" method (checking the voltage for breakdown from 500 to 3000 V), and the measured threshold of the insulating resistance can be increased to 250 megohms. As a result, there is a guarantee of the absence of dielectric breakdowns with low operating voltage during the operation of the PCB.