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DIY Solder Mask

Xenobius

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Ok so this question is for the die hard diy out there and you must keep an open mind when/if answering.

I have been doing my own PCBs for over 15 years and I have perfected my technique and can get really fine details and smd without issues. I would now like to do solder mask. I have seen plenty of videos out there which use either a UV Curable film or UV Curable Paint and I know that these methods work so I must politely ask you not to refer to such techniques.

It is a known fact that if you spray paint over Vaseline, the paint won't stick. So with this in mind I was thinking of using the same solder paste stencil to paste the pcb with Vaseline. Than proceed to spray paint it with canned spray. Finally when it's dry you just wipe off the paint that did not stick due to the Vaseline. (On you tube this works well for doing crafts so it must work here too)

My real question before I waste time experimenting with this:
Did anyone out there think of this before? Did it work? Will the spray paint still be "flammable" after it dries? Will the spray paint help protect the copper or will it react in some way and corrode it?

Thanks
X
 

c_mitra

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The idea is good but problematic. I have not tried but think of several problems:

1. greasy materials, like vaseline, has a tendency to spread. it will not give a sharp boundary.

2. the paint is also grease-like. If the paint is applied in the form of a spray, it will try to dissolve part of the grease. In fact, a small amount of grease will not prevent paint to stick (paint will stick in spite of the grease).

3. The paint will not be flammable after it dries. The solvent is highly volatile and flammable.

4. Most paint will not corrode copper. In fact, the green solder mask widely used for solder resist is a paint.

5. Common paint will not stand the heat of a soldering process. The paint will burn (some may be more resistant).

6. How do you plan to pull off the paint from the vaseline coated area? It may peel off like a skin.
 

Xenobius

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Thanks for your reply. You make very good and valid points. I suspect if you cool down the vaseline by keeping it in a refrigereator until the last moment before you use it, it would stay consistent enough to avoid spread. Within a few minutes of spreading it on the board it should be sprayed, at which point the paint would have stained the board prior to the vaseline melting. If it does I would imagine it would go on top of the paint.

As for the paint will stick in spite of the grease - well no clue here :) you beat me!

As for heat, there is heat spray which can go beyond 450C so it should withstand most soldering. Another benefit of this spray is the speed at which it dries. Effectively before the vaseline has the chance to make any movements.

Finally, simply wiping the board with a clean cloth should be enough to remove the paint that did not stick due to the vaseline.

I'd like to try it out!
 

dick_freebird

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If it were me, I would first experiment with lacquer
and shellac, both of which have easy solvent
cleans but are hard otherwise.

Probably makes a difference whether you intend
hand soldering and only need a brief "oops protect"
or mean to do wave soldering with a longer dwell
at whole-board high temp.
 

Xenobius

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Hmm very good points too! Its really for hand soldering and protection from corrosion and oops thank god there was mask :p
 

c_mitra

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One suggestion: try a paint that is cross linking (eg epoxy type or similar) because they tend to become insoluble after some time (hardens). Most common paints (eg acrylic or latex type) melt easily and remain soluble in many common solvents. Select paints that have low metal (many pigments used in common paints are metal compounds) content (they can reduce the dielectric strength).

Also let us know how your experiment went. When I was younger, I covered the pads with adhesive tape cutouts and cover the rest of the board with paint. I had to take out the adhesive covers before the pain gets hard (when it is semi dry). The pads were with holes and pushing a pin from the other side did the trick.
 

Xenobius

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That's so cool! I'm currently rebuilding my UV box and once that's done I will def try this and let you know!!
 

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