Air agitation worked quite well for me to move the etchant around. I
think a peristaltic pump has very low flow rate, at least the small
ones I'm familiar with (infusion pumps and the like). Apparently some
of the diaphragm pumps can be converted to no metal parts in the wet
side, not sure if it was sureflow or flowjet brand.
Another option is to make a mechanism to mechanically fan the board
back and forth. This creates a lot of flow even with quite sedate
montion. It avoids the mist generated by air agitation, which pretty
much requires a closed tank unless you work outside again, poisoning
the squirrels and pigeons. But it will lead to faster etching near the
edges, just like air does for the lower edge.
ST
On Mon, Aug 1, 2016 at 4:38 PM, Harvey White
madyn@...[Homebrew_PCBs] <
Homebrew_PCBs@yahoogroups.com> wrote:
> On Mon, 1 Aug 2016 06:50:27 +0200, you wrote:
>
>>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 may try this, it seems lots better than immersion tin. Right now,
> I'm in a software phase of development, much cheaper than making
> boards. Some boards are at the production phase, so I've got a design
> that works, I'll just possibly need more of them.
>
>>
>>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.
>
> Before I did something like that, (unlikely), I'd try to make a
> etchant system with a pump for more even etching. May end up with a
> peristaltic pump and silicone tubing.
>>
>>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.
>>
>
> Now that seems to be the simplest one, so that's on the list, too.
>
> Thanks for the suggestions:
>
> Harvey
>
>>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
>>>
>
>
>
> ------------------------------------
> Posted by: Harvey White <madyn@...>
> ------------------------------------
>
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