Homebrew PCBs

There you go again, poisoning the squirrels.

I did something much like HASL when I still made boards, what you can
do is you buy a can of plumbing solder paste (the solder bearing
kind). This is tin only solder so you don't need to worry about the
waste, and it's much cheaper than SMT solder paste for electronics.
Then you dilute it to a consistency you can paint with a brush, just
with water. Paint that on your board, heat with air gun to reflow. The
excess on bare surfaces just washes off.
This leaves a pock-marked matte surface, if you want it smooth and
shiny you can wipe off the excess with a paper towel while still hot.
Does the same as air leveling but much more practical at home.
Mind to wash the flux off well, since it is not electronics flux. It
is water soluble since it is designed for plumbing and hot water takes
it right off.

I briefly considered building a roller tinning machine, basically two
rollers between which the PCB is fed, with the lower out of metal and
immersed in a solder bath at the bottom. The whole thing is heated and
you just feed the board through. I was told it works fine but keeping
the solder bath free of dross is a bit of a pain, requiring special
flux. You can find pictures with google, they are used commercially.

That said, the vast majority of boards I simply coated in colophony
resin (rosin) flux. This is so mild it doesn't cause corrosion, and
with denatured alcohol (ethanol) it can be made into a nice laquer.
Since it is a flux it is great to solder and protects the copper from
oxidation for a long time. They even make a spray can so you don't
need to mess with the sticky paintbrush.

ST

On Mon, Aug 1, 2016 at 6:06 AM, Harvey White madyn@...
[Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:
> On Mon, 1 Aug 2016 05:45:53 +0200, you wrote:
>
>>RoHS allows 0.1% lead.
>>
>>I think this Liquid Tin is based on thiourea, something much, much worse
>>than lead. Remember to wash your hands and wear a hardhat or something ;-).
>
> I think it is.  It comes with lots of warnings, most of which involve
> the word "poison".
>
> I use gloves and tongs, and wash the boards thoroughly. Also, this is
> done quite outside the house.
>
> Wonder if I could do something like HASL....
>
>
> Harvey
>