This testing of PCBs at the design stage can be carried out using various techniques, such as EMI, Signal Integrity and Power Integrity. This minimises design issues that could lead to problems later on. But how can you test a printed circuit board after it has been assembled to check that everything is in order? How can you be sure that there are no short circuits, that no poor solder joints have been made, or that components have not been placed incorrectly?
What is a PCB test fixture?
Generally speaking, a PCB test fixture is a device consisting of a pin bed on which a PCB (either unassembled or already assembled) can be tested. These test fixtures can be operated manually or pneumatically. With manual operation, the user must manually engage the clamping mechanism that holds the PCB in place on the pin bed so that the test can be carried out. With pneumatic operation, this action is carried out automatically.
Test fixtures are specifically designed for individual PCBs or a product line of PCBs. This testing method is taken into account in the PCB design from the outset, including by incorporating test points so that testing the PCB on the fixture can be carried out as efficiently as possible.
The different ways of implementing a PCB test fixture
A PCB test fixture can be implemented in various ways and across different phases. We briefly explain these different methods below.
A bare-board PCB test
A bare-board PCB test fixture is a test that checks boards that are (as yet) empty. This involves correctly verifying the defined circuit connections on the manufactured printed circuit board.
For example, a small voltage is applied to the board and a check is carried out to ensure the board functions correctly in terms of ‘short’ or ‘open’ circuits.
A PCB test fixture at assembly level
Assembled PCBs can also be thoroughly tested. This can be done in various ways. For example, a manual inspection can be carried out, or Automatic Test Equipment (ATE) can be used. An ATE performs a PCB test much faster than if it were carried out manually. However, an ATE is much more expensive than a manual test. For this reason, it is essential to choose the correct type that is suitable for testing the PCB.
A functional PCB test
A functional test (FCT) is the final test stage in the PCB development process. It provides a pass/fail assessment of finished PCBs before they are delivered. The aim of the FCT is to validate that the hardware is free from defects that could hinder the correct operation of the product.
