What is The Method of PCBA Functional Testing?

PCBA functional testing refers to a test method that provides a simulated operating environment (excitation and load) for the test target PCBA board, so that it works in various design states, so as to obtain the parameters of each state to verify the function of the PCBA target board. Simply put, it is to load a suitable stimulus on the PCBA target board and measure whether the response of the output terminal meets the requirements. There are two methods of PCBA functional test, wired test and wireless test.

Wired test fixtures have always been the industry standard for functional test fixtures. Wired test fixtures provide an economical approach on lower probe count PCBAs or prototypes where the design may change as they avoid non-engineering (NRE) costs. The challenge with wired luminaires is that as the signal frequency increases, crosstalk and coupling issues can increase. This is due to the fact that the wires are routed under the probe card, and coupling and crosstalk increase with frequency.

Engineers developed wireless test fixtures to address the limitations of wired test fixtures. In wireless fixtures, a multi-layer PCB called a transition board (T-board) replaces the set of signal wires on the underside of a wired probe card. Automatic PCB design software is used to route circuit traces when changing wires. The double-ended probe connects the PCBA under test to the T-board.

Wireless devices are often more reliable than wired fixtures because the PCB designer can precisely control how each trace is routed on the bottom of the T-board, which can isolate troublesome signals. Repeated fixtures perform nearly identically, with very consistent electrical parameters, as there are no wires and the variations they cause. Reduced ground and crosstalk noise make the signal bounce faster, which is especially important in low voltage test applications.