Robert: Matte soldermask has a higher surface energy than gloss mask.
Because of this it wets more easily and holds a more uniform thicker coating
of flux than the gloss. You can use the analogy of a waxed car (low surface
energy)it does not wet and retain a coating of water, it beads up and runs off,
same thing for the gloss mask.
        Since the matte mask holds more flux, wave solder settings like
preheat/conveyor speed have to adjusted (more preheat/slower speed)to drive off
the volatiles in the heavier coating of flux before contacting the solderwave.
Also flux applicator settings, especially spray type can be adjusted to control
the amount of flux on the board.
        Glossy mask run at these same settings could dry out and create solder
webbing or bridging when run thru the wave. Glossy mask also has a greater
tendency to form solder balls which may require additional adjustments of the
the settings to minimize.
        With one standard mask your assembler will not have to do as much
process adjusting and will probably provide a more consistent product. My guess
is they would prefer the matte.

                                        Regards
                                                Michael Barmuta
                                                Staff Engineer
                                                Fluke Corp.
                                                Everett Wa.
                                                425-356-6076

On Thu, 4 Jun 1998 05:22:57 -0700 Robert Welch wrote:

> From: Robert Welch <[log in to unmask]>
> Date: Thu, 4 Jun 1998 05:22:57 -0700
> Subject: [TN] ASSEM: MATTE VS GLOSSY
> To: [log in to unmask]
>
> Hello Technetters,
>
> I've been asked to forward this inquiry for a contract assembly
> person we deal with occasionally.
> His problem is that he has to adjust his wave solder parameters (more
> or less preheat??)  when changing between "very shiny" and "very
> dull" solder mask on the same part number.  He would like some
> collaboration of this phenomena to help  justify
> requiring his supplier to keep  all the mask the same.
>
> Thanks,
> Robert E. Welch
> Process Specialist
> Email: [log in to unmask]
> Modem: 804-239-9120
> Fax:   804-237-3048
>
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