Hi Paul:

Sometimes an uncured or improperly cured soldermask can cause whitish
residue on the sides that are exposed to heat such as wave solder
process.

Chetan

>Date:         Fri, 15 Jan 1999 17:04:48 -0400
>Reply-To:     "TechNet E-Mail Forum." <[log in to unmask]>,
>              Paul Wareham <[log in to unmask]>
>From:         Paul Wareham <[log in to unmask]>
>Subject:      [TN] White blistering on solder mask.
>To:           [log in to unmask]
>
>Getting alot of white blister marks on a batch of boards.  All boards =
>seem to be from the same date code of board manufacture.  The marks
seem =
>to occur over all areas, not just over copper.  There is no residue and
=
>does not scrape, it looks like it is subsurface.  To me, it looks as =
>though there is some weakness in the solder mask which was brought out
=
>under the stress of wave solder.  The marks are only on the solder
side, =
>and only seem to appear after they've been washed.  Could a defective =
>solder mask have been damaged by heat stress of the wave, then
providing =
>a home from moisture during the wash process?
>
>Any ideas?
>
>Paul Wareham
>DynaGen Systems Inc.
>


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