Item Subject: [TN] PCB'S
     Sean,

     The residue can be caused by a couple of things. One reader mentioned
     quartz filler in his reply. I had a problem with that before. The fix
     was to lower the wash water temp to below 140 degF. At the lower temp,
     the quartz will not diffuse to the surface of the soldermask.

     In my experience, however, the usual cause of the white residue has
     been polymerized flux residue which, obviously, can occur with organic
     fluxes. The soldermask formulation and surface finish can contribute
     for the tendency of the residue to stick to the surface. Matte
     finishes are perhaps more prone to this than glossy finishes.

     I have tested white residue and found that it is only a cosmetic
     issue, not a reliability issue, even though tin and lead can complex
     with it in wave solder (tin and lead can show up in an XRF of the
     residue). If that is the problem, your choices are either to live with
     it, or to use a saponifier in your wash system. Saponifiers, such as
     Alpha (I forget the number-1156?), work well to remove the flux
     residue.

     Regards,

     Denis Mori


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Subject: [TN] PCB'S
Author:  Non-HP-Cirman ([log in to unmask]) at HP-Boise,shargw1