As PCBs become more complex and integrated, the need for thorough testing becomes increasingly important. Testing ensures that the PCB functions correctly and reliably, which is crucial for electronic devices. In this blog post, we will compare two popular PCB testing methods: Flying Probe and In-Circuit Testing (ICT).
Flying Probe Testing
Flying Probe Testing is a non-contact, automated PCB testing method. It uses two moving probes that scan the PCB's component pads and vias, checking for electrical integrity, shorts, and opens. The probes do not require a full test fixture (unlike ICT), which is beneficial for smaller or more complex circuit boards.
Flying Probe Testing requires a test program to be written and uploaded to the machine, which takes time and requires programming expertise. However, once the program is in place, testing time can be relatively fast - typically around 1-2 minutes per board.
In-Circuit Testing (ICT)
In-Circuit Testing is a contact-based PCB testing method that uses a test fixture with connectors fitted to the printed circuit board. This fixture allows the test equipment to access each net on the board and validate the circuit's operation.
ICT checks the function of all components and interconnects on the board, including passive components such as resistors and capacitors. Unlike Flying Probe Testing, ICT can detect faults within the analog circuitry.
ICT requires a custom test fixture to be constructed, which can be costly and time-consuming. The fixture's design and construction are often outsourced to a third-party vendor. However, once the fixture is in place, multiple boards can be tested simultaneously, making it an efficient method for large-scale production.
Comparison
Both Flying Probe and ICT have their pros and cons. In summary:
- Flying Probe Testing is faster and more cost-effective for small batch sizes or complicated boards.
- ICT is more robust, can detect faults in analog circuitry, and is faster for large batch sizes.
However, it's important to note that Flying Probe Testing is not a replacement for ICT. A PCB typically undergoes a combination of testing methods, with Flying Probe Testing performed first. ICT is then used to validate the final design and ensure that it meets the customer's specifications.
References
- United States Patent "Flying probe method for testing printed circuit boards." Patent number: 5895976, Issue date: April 20, 1999.
- Agilent Technologies "In-Circuit Test Design and debugging" Publication 5991-2341EN.
- Perfectron Corporation "Comparison between Flying Probe Test and In-Circuit Test" https://www.perfectron.com/English/news_detail.php?SID=26 Accessed on January 18, 2022.