PCB Functional Testing
Functional Testing for Reliable Electronic Assemblies
We ensure every board powers up, runs, and responds the way it should before it ships.
What is functional testing (FCT)?
Functional tests examine entire printed circuit boards to verify that assemblies behave as intended in their final application.
The board is powered, key functions are exercised, and the results are checked against your requirements under realistic operating conditions.
These tests use a mix of automated equipment and software that run defined steps and capture measurements, with operators stepping in where hands-on or visual inspections are still needed.
Our functional testing process
TEST SETUP AND EQUIPMENT
PCB assemblies are placed in customer-provided fixtures and connected to test equipment such as multimeters, load switches, and specialized jigs so the functional test can mirror the final electrical environment.
FIRMWARE AND SOFTWARE LOADING
Where required, functional tests include loading and verifying firmware or software on the board, with automated software handling the test steps and measurements to reduce operator involvement.
AUTOMATED TEST EXECUTION
The automated system runs the defined test sequences, applies loads, and measures responses, ensuring consistent results from board to board across different production volumes.
TARGETED OPERATOR CHECKS
For tasks that cannot be fully automated, such as checking that LEDs or other indicators behave correctly, operators perform visual checks and verify performance.
POST-TEST INSPECTION LINK
After functional circuit testing, boards move into post-test 5% inspection, where conformal coating and other critical post-test elements are verified before product release.
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Frequently Asked Questions
PCB functional testing offers a check to ensure the complete assembly behaves like the final product. The board is powered, firmware or test software may be loaded, and defined test cases run, so you can see how the PCB’s behavior lines up with your requirements in a realistic operating environment.
Other common PCB testing methods at August focus on different stages of the build:
- 2D and 3D solder paste inspection (SPI): Checks solder paste volume, height, and alignment before individual components are placed, helping ensure joints form correctly on each pad. SPI supports early quality control in the PCB production flow so defects are caught before they affect downstream assembly or increase failure rates.
- 3D automated optical inspection (AOI): A vision-based check that verifies placement, polarity, and markings, helping catch missing components or misaligned parts as part of upstream PCB testing and quality control.
- X-ray inspection: Targets hidden features such as ball grid arrays, internal vias, and dense areas where optical tools cannot see, helping maintain product quality in more complex layouts.
- In-circuit testing (ICT): Uses test points, test pads, and fixtures to look for short circuits, opens, and incorrect electronic components before the board is fully powered. In-circuit testing focuses on ensuring structural integrity and identifying issues early in the PCB assembly process.
- Dielectric testing (HiPot): Applies high voltage to confirm insulation and electrical safety, complementing functional tests by checking safety margins under more extreme conditions.
Every project at August uses a comprehensive suite of test methods, but not every board will see every possible test. Your test plan, product risk, and volumes determine which other tests are combined with PCB FCT testing to get the coverage you need without unnecessary cost.
PCB functional testing can exercise the board under simulated operating conditions that reflect how it will run in the field, including real loads, expected operating frequency, thermal stress, and typical duty cycle on power stages or control loops. The goal is to confirm that the assembly will function correctly when it is installed in its target system.
For more complex or high-frequency boards, the test plan can focus on the signals and timing that are most sensitive to the operating environment, so the test checks the right behaviours instead of only basic overall functionality.
Functional testing takes place near the end of the electronics manufacturing process, after the PCB assembly process and earlier inspection steps are complete. It typically follows AOI, X-ray, and in-circuit testing, and happens before final packing and shipment.
If a board fails PCB testing, it is removed from the conforming population and investigated against the agreed product specifications. Technicians and quality inspectors look for issues such as incorrect voltage, short circuits, or non-responsive components, then perform root cause analysis to understand why the board did not operate correctly.
Our thorough testing reduces human error, prevents costly repairs in the field, and feeds back into quality control, allowing the overall electronics manufacturing process to be adjusted if a systemic problem is identified.