Kitty,
Solder mask materials come in many varieties ranging from dry film laminate to screened wet film or photoimagable liquid solder mask. Soldermask thickness ranges from 0.6 mil to 9 mils across mask types. Dry film ranges typically from 3-4 mils, photoimagable from 0.6 to 6 mils across various manufacturers, but is quite tight within a single supplier (i.e.,variations of only a mil) and wet film has the largest variation of0.6 mil to 9 mils.
I would recommend that you talk to your fabricator, and see what materials they have available for mask and what their tolerances can be and any notes they currently would recommend. Compare this against the product needs, and choose your best application material and note from there.
Karl
> Date: Tue, 15 Oct 2013 08:45:46 -0500
> From: [log in to unmask]
> Subject: [DC] Specifying max solder mask thickness
> To: [log in to unmask]
>
> Good Morning,
> I'm looking for the best way to specify solder mask thickness,
> particularly when it covers a via or pad, which causes a slight bump. This
> situation can cause excess solder paste on pads, after application using a
> 5 mil thick stencil. I've looked at the IPC-840-SM, but didn't find
> anything that looked like a NOTE, that I can add to my Fabrication
> Drawing. Or maybe I just missed it. What wording or diagram do you all
> use for this specification? I appreciate any help you can be.
> Thank You,
> Kitty
>
> Kitty Hines
> ECAD Librarian/PCB Design CID+
> Chamberlain Group, Inc.
> (630)516-6655 office
> [log in to unmask]
>
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