[OT]Homebrew PCB fabrication

From: Marvin Johnston <marvin_at_rain.org>
Date: Sun Feb 20 12:17:15 2005

There is no quick good way to "tin" homebrew PC Boards since "tin"
usually refers to solder. There is an electroless tin solution available
that will put *tin* on the board, but the shelf life for good
solderability is not very good since it is a very thin coating.

With respect to the "green protective layer", that is solder mask and is
silk screened on and baked (there are photo emulsions but I don't think
they would work well for home brew applications given the equipment
needed.) There are one part solder masks available and it would be
relatively easy to apply. The problem is making the silkscreen. For
stability, the mesh is usually stainless steel applied to a metal chase.
Using a polyester or similar mesh would make it difficult to align to
the board resulting in solder mask being applied to the traces. Making
the stencil is a photo process using a photo sensitive emulsion that
gets exposed and developed, and then applied to the mesh.

With the proper setup, a screen can be made in a matter of minutes, and
the drying time for the emulsion would probably be another 30 minutes or
so (if it is not dry, the pads will pull off when the mylar backing is
removed as they will with incorrect exposure.) SMOBC (Solder Mask Over
Bare Copper) is a good way to make the boards, and assuming the
screening capability, is quite suitable for home use. Be aware that the
solder mask *does* have a shelf life. If you know of a PC Board house,
you may be able to talk them out of enough solder mask to do the job.

> Just wanted to know what some of you folks are doing in terms of
> homebrew PCB fabrication:
> 1. What do you folks use for tinning PCB tracks? I'm still doing it
> the old-fashioned way...by hand! :-)
> 2. Is there a way to laminate PCBs (i.e. the green protective layer on
> the solder side) using home "technology"?
> /wai-sun
Received on Sun Feb 20 2005 - 12:17:15 GMT

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