Defects Database

Dr. Chris Hunt

Before printing, study material characteristics for resistance to slumping.

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Dr. Chris Hunt

A nickel barrier layer prevents leaching of the silver base metallization layer.

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Dr. Chris Hunt
When joints look perfect but nonetheless are failing, check the plating adhesion.

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Dr. Chris Hunt
Exhausted flux can cause incomplete reflow.

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Dr. Chris Hunt

A lack of flux or dip paste on the package can lead to post-reflow defects.
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Exposed copper coupled with silver final finish is causing opens.

Figures 1 and 2 show two images of the same problem: one x-ray, the other optical. In both cases it’s the result of sulphur corrosion on the surface of copper and silver surfaces.

Both surfaces remain exposed after a soldering operation, and in the presence of sulphur, it is possible to witness corrosion. In time it can result in an open connection, as the figures show. Figure 1, taken on a Dage x-ray system, shows different degrees of corrosion on the tracking just below the solder joint fillet. In failure investigations it’s important to see and record as much as possible without change or damage to the sample. On one joint there was an open connection on this QFP device.

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