Function test (FCT) of circuit boards is one of the most important phases during manufacturing process, in which PCBA can be checked if in compliance with design.
What’s Function Test (FCT)?
The simple premise of FCT is this: to simulate the board in the environment in which it is going to work. In this printed circuit board testing the entire PCB is checked using a variety of test probes. What must be realized is that the testing cannot emulate exactly what the prospective user of the board will use it for; rather it performs tests to ensure that the board is fully functional and can be used for the intended purpose. Some parameters that FCT checks for include:
- Voltage
- Current
- Resistance
- Capacitance and inductance
- Open circuits
- Communication protocols
FCT is also the stage where final serializing of the PCB can take place: adding serial numbers, calibrating the board or other specific work on the board before it is shipped out. Function tests (FCT) check the entire intended function of a PCB. According to the intended area of use, the environment is replicated and the electrical performance of the PCB is checked.
In order to optimally fulfill the contacting requirements, various test probes are available. These differ in terms of installation height, grid size (possible distance between probes), tip style, and type of connection – see following illustration. The electrical connection is achieved either with a solder cup or wire-wrap, with or without cable (wireless).
Since PCBs differ greatly from one to another, FCT Test Benches must be configured for different printed circuit board testing. Specialized testing firmware too must be designed for the specific boards. All this adds time and cost to the assembly process, but is prerequisite for ensuring your customers receive the high quality PCB they expect.