In the world of electronics testing, accuracy and reliability are crucial. I recently encountered an issue with our testing setup where an Ingun probe did not make proper contact with a via on the printed circuit board assembly (PCBA). This resulted in inconsistent test results and wasted time. In this post, I’ll share how we identified and solved this problem.
During our troubleshooting process, it became important to verify that the infrared (IR) LEDs on the PCBA were working correctly. To do this, we needed to measure the IR wave emitted by the LEDs and display it on the oscilloscope. This was a crucial step in ensuring that the IR signals were functioning properly in the circuit and interacting as expected with the tester.
but instead it showed
During a routine test, I noticed that one of the tests failed intermittently. Upon closer inspection, I realized that the issue stemmed from the Ingun probe not properly contacting a via on the PCBA. This was causing signal disruptions, leading to incorrect readings in the test results.
Troubleshooting Process
- Initial Inspection: We first inspected the tester and the PCBA for any visible issues. There were no obvious defects in the via or the probe.
- Mechanical Alignment: We checked if the tester’s alignment was correct and verified that the probe should be in the correct position to touch the via. The issue still persisted.
- Probe Wear and Tear: We examined the Ingun probe for any signs of wear or damage. Probes that have been in use for a long time may lose their spring tension or suffer from tip degradation, which affects their contact pressure. In this case, the probe looked intact but slightly worn.
- Board Surface & Via Condition: After ruling out the probe, we checked the PCBA’s surface. The via was not raised enough, so the probe’s contact was minimal, especially after repeated tests.
Using Flux Green Spray to Aid Contact
As part of our troubleshooting process, we also considered using flux green spray, which can be an effective way to enhance contact between the Ingun probe and the via on the PCBA. Flux is typically used to improve solder joint reliability, but in this case, we used a flux green spray for a different purpose: ensuring better electrical contact.
- Why Use Flux Green Spray? Flux green spray helps clean and prepare the surface of the via, removing oxidation and debris that might be preventing good contact with the probe. The spray not only improves the conductivity of the contact area but also ensures that the probe tip can properly interface with the via, even if there are minor imperfections on the surface.
- Application Process:
- We first cleaned the PCBA thoroughly to remove any dust or residual contaminants.
- Then, we applied a light coat of flux green spray directly to the via and surrounding area.
- After allowing it to dry, we ran the test again to check for improvements in contact reliability.
- Results: The use of flux green spray noticeably improved the consistency of the probe’s contact with the via. The intermittent test failures we had experienced were significantly reduced, and the overall reliability of the testing process increased. This simple step provided an additional layer of assurance that our contact points were optimal.