One of the challenges in testing with probes is accuracy. The level of accuracy during testing significantly impacts the final test results and plays a crucial role in determining the quality of the product produced.
I was tasked with resolving an ongoing issue with a test device, where many PCBAs consistently failed transmission testing, but the source of the problem could not be identified.
I suspected that the probe might be worn, but replacing it with a new one did not resolve the issue.
In the past, I have encountered a problem where the probe did not properly touch the designated test point, so I decided to try to check based on this.
I used flux green spray to aid contact and discovered that the test point does not properly align with the designated contact area.
As shown in the image below, the probe makes contact with the area between the two conductors (red dot), or sometimes only partially touches, resulting in incorrect measurements and failed PCBAs.
Conclusion:
The problem arose due to a change in the PCBA layout, without considering the existing probe locations. This resulted in a mismatch between the probe positions and the test points, placing them in different locations than those defined in previous versions.
The solution was to adjust the layout in subsequent versions of the board to ensure alignment with the existing test configurations.