In-circuit versus functional testing

Following on from our PCBA testing blog, which looked at the two most commonly used methods of ensuring the integrity of printed circuit board assemblies (PCBAs) – in-circuit and functional testing – it is also important to understand the difference between these two test methods. Although, ideally, both should be used to confirm integrity and functionality, this may not always be practical.

In-circuit

In-circuit testing is a far more comprehensive process, as each component is tested independently against a programme model based on parameters that are specific to the components and not to the overall functionality of the PCBA.  This method generally uses automatic test equipment (ATE), based on a ‘bed-of-nails’ test rig.  Potential problems with components can, therefore, be automatically identified, without requiring skilled engineering analyses.

Although this arrangement produces consistent and extremely accurate results, test rigs need to be built specifically for each assembly; this can add additional cost to the test process - although if production volumes are sufficiently high this is rarely an issue.

Functional

By comparison, functional testing applies inputs and power to the complete assembly, checking that it performs its desired functions to a certain specification under test conditions.  This method may not, however, identify problems with components that are intended to function only under emergency conditions, or that are not integral to the basic operation of the PCBA.  Additionally, if the PCBA fails a functional test, it may be a complex operation requiring engineering skills and specialised instrumentation to identify the root cause.  The advantage of functional testing, of course, is that it can be carried out without the need for customised test rigs.

Here at Offshore Electronics, our expert production and test engineers work closely with our customers to determine the most efficient and cost-effective method of validating and testing their PCBAs to their required specification.  If you’d like to learn more about in-circuit and functional testing please contact our team at [email protected].