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Volumetric Porosity & Cracks in PCB Housing

INVESTIGATING A FAILED LED HOUSING

This LED housing has failed. It was sent to us to try to locate the point of failure, which is equivalent to finding a needle in a haystack. The point of failure is seen in one of the two images below. Can you spot it before moving to the next section of the post?

point of failure

While porosity calculations are interesting, typically an individual joint has a 20% porosity tolerance which can usually be gauged visually. Porosity is not the failure of this part.

If you look near the yellow arrow you’ll see a vertical, linear indication or fracture in the component. During evaluation the inspector uses multiple viewing directions for each component to find such small points of failure. If this crack were perpendicular to the viewing direction it likely would not have been found.