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May 2005

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Subject:
From:
Dennis Fritz <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Wed, 11 May 2005 10:56:04 EDT
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The "matte" or "gloss" in a solder mask is set by the mask  formulator.  In
that regard, it is the same as paint.  The matte agent  is usually an inert
filler, like silica.  Gloss is a function of light  scattering by the surface.
Normally, all masks are relatively transparent,  so that you can see the
outline of the circuitry below the mask.  On the  other hand, nomenclature inks tend
to be opaque, so that they have good contrast  to the mask.

I don't recall that the IPC has ever tried to quantify "gloss"  in any of the
revisions of SM-840.  If you want to try that, I suggest you  fall back on
the paint industry standards, but I would guess that your board  supplier will
not have the equipment to measure gloss.

Jeffrey Bush has gone through the major technical  considerations in choosing
gloss versus matte - ease in cleaning, conformal coat  adhesion, nomenclature
adhesion, ease of inspection, and solder ball  formation.  The TechNet
archives may be helpful, as this topic was widely  discussed 3-5 years ago.

I would suggest you list the qualities you want in your mask  surface, and
work through your supply chain to specify the mask and vendor you  want.

Denny Fritz
MacDermid, Inc.

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