To x-ray or not to x-ray?

To x-ray or not to x-ray?

A lot of engineers know to come to DeltaProto when they need a second opinion.

In this case a small series of PCBAs had a low #yield and we were asked to x-ray the assemblies. Because we adjust our own stencils and use a Vapor Phase soldering process, we rarely have doubts about the solder joints, so it seemed sensible to inspect the board thoroughly first.

Nothing remarkable to be seen. So, to be honest, our first conclusion to the #engineer was: chances are the problem lies in the design or in the component interaction.

Yet the engineer remained convinced that an x-ray inspection was needed. So we re-soldered a number of boards, left a number untouched and put everything under the x-ray.

And that's when the real cause emerged.

Underneath a critical component there turned out to be irregular voiding and insufficient solder wetting — something that was virtually invisible to the eye, but that did have a direct impact on the reliability and yield of the series.

Moral of the story:

Sometimes a second opinion confirms your first hunch… and sometimes an engineer with a strong gut feeling proves exactly why extra analysis is worthwhile after all.

Especially in protos and small series, the gains often lie in collaboration, daring to keep some doubt and looking just one step further.

#PCBAProtoLabLearnings #HappyEngineering

PS: Do you know which solder joint in the photo was the culprit?