Do you have a warm water rinse after assembly? Some of the solder resists
have a quartz type filler that doesn't return to "form" when quenched in
warm water. The problem appears to be a white residue. To test if this is
the problem, you can bake the boards at about 300 degrees F for 20-25
minutes. This will cause the filler to return to form and the board will
appear normal. If this is the case you can typically eliminate the problem
by not heating the rinse after assembly. If this isn't possible, it is a
cosmetic problem only and you may choose to accept it as is.

David Arivett

P.S. I am certain I have not explained the phenomenon completely, maybe
some of the solder resist manufacturers can explain this better.


At 04:12 AM 11/28/97 -0500, you wrote:
>Dear Sir or Madam,
>                     I have a white resiude problem after aqueous assembley,
>i know the solder resist manufacturer has changed his formulation, but I
>would like to work with the solder resist manufacturer as the resist has
>numerous advantages.
>                 Regards,
>                     Sean
>
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