In-circuit testing ensures proper manufacturing and quality in PCBs. The bed of nails test is the most common method, using connector pins to test for electrical problems. There are pressure and vacuum bed-of-the-nail testers, with vacuum being more efficient but expensive. The test can help find faults, but cannot test PCB contacts or durability.
An in-circuit test is a test that ensures there are no shorts, resistances, or other problems with the printed circuit boards (PCBs). It is intended to ensure proper manufacturing and quality in PCBs. The most common in-circuit testing method is the bed of nails test, where the PCB is pressed against a panel of connector pins so the pins can test for electrical problems. There are pressure and vacuum bed-of-the-nail testers, with vacuum generally considered better but also much more expensive. While this test can help manufacturers verify PCB problems, there are limitations, such as faulty master designs; even the contacts cannot be tested for quality.
Many electrical components must work simultaneously and as a team for a PCB to work. During the manufacturing process, several problems can occur that would prevent a PCB from functioning. The machines that put the PCB together may malfunction or some of the smaller components may be faulty. To verify the functionality of the circuit, an in-circuit test is performed.
The most common way to do an in-circuit test is to place the PCB on a device called a bed of nails, so called because it uses many electrical contact pins that together look like a bed of nails. To initiate the test, a PCB is placed on the device. The contacts then push power through the PCB to check for problems such as shorts, resistances, or breaks in the circuit.
Claw bed devices are classified by how they secure the PCB to the contacts. In the push-down method, the PCB is simply pushed against the nails to make contact. The vacuum version uses a vacuum seal to suck the PCB into the contacts. These two are both adept at performing an in-circuit test, but the vacuum version is more efficient and the push-down method is cheaper. Both versions tend to leave small marks on the tested PCB, but this does not affect the functionality.
Performing an in-circuit test will help manufacturers find faults with PCBs, but the process isn’t foolproof. While in-circuit testing can test the circuit to ensure that power is working properly through the PCB and that all parts of the circuit are working, it cannot test the PCB contacts, which could prevent the PCB from working in a computer. If the PCB design itself is faulty or prone to breaking easily, that too can cause problems, because testing can only ensure how well the circuit design will work, not how durable it will be.
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