Helo Frank:

It is difficult to tell without seeing or testing product. Some of the holes appear to have very low contact angles and others have granular solder. In this case, I would suggest two problems that might be linked.
1. Contaminated solder / solder paste
2. Excessive intermetallic.

The first case might lead to higher than normal soldering temperatures or extended times that may generate thick intermetallic layers.

If the bare board surface finish is suspect, we would have to look at an unsoldered board. The problem could be thin gold, thick gold ( > 0.3 microns ) or some form of contamination from the solder mask process.

All speculation without seeing the boards.

Probably not much help but I will try to do better with more information.

Regards

Charlie McMahon


Frank L Norman wrote:

>Technet,
>
>PWA's experienced solder wetting difficulties to plated through holes
>including via's during the wave solder process. PWA's are two sided
>multilayer finished with Electroless Nickel Immersion Gold (ENIG). Top
>side SMT components were reflowed and bottom side SMT and through hole
>components were wave soldered.
>
>SEE PICTURES of bottom side of PWA at this website.
>
>http://www.ripus.com/images/pwa/index.htm
>
>Does anyone know what may have caused this issue?
>
>Regards,
>Frank Norman
>Manufacturing Support Engineer
>Raytheon, Space and Airborne Systems (SAS)
>(805)879-2745
>[log in to unmask]
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