On Sat, 19 Mar 2016 10:31:19 -0700, you wrote:
>Ancel,
>
>Thanks for the link. He has some interesting approaches. I was with him
>all the way until the Nitric Acid. Bad stuff in any concentration.
>Luckily, this works with our more conventional etchants.
>
>My issues with double sided are not registration, I use similar pins,
>but mine are the ones with the metal tops. I found those to be more
>uniform in diameter from one pin to the next.
I should probably get some drill rod and make a fixture.
>My problem has always
>been getting uniform etching on both sides. At one point, I built a
>vertical bubble etcher with a heater for ferric chloride etching. I
>arranged the bubbler such that I had coverage on both sides. The
>results was that the edge of the board closest to the bubbler became
>over etched, while the area furthest away was only beginning to etch.
Exactly what happens. I ended up monitoring the process and moving
the boards around. Since I do one side only, it's easier to monitor.
I've also been known to turn the boards upside down. It will make a
difference, but it's not a hands-free process.
I use HCL and peroxide, and that works well enough. I would like to
use sodium persulphate, and I actually found a flow tank (two aquarium
pumps and shaped plastic) to use with that etchant, but I am quite
wary about using it with anything with acid in it. It has a heater as
well.
>I envied the spray etchers my company used in their PWB production area.
Love to have one, there are some construction articles around, though.
>My best results were obtained by fully masking off one side while
>etching the other. Tedious, but it works.
it certainly does. The epoxy board method makes the process somewhat
more manageable.
Harvey
>
>(Another) Harvey
>
>On 3/19/2016 2:12 AM, AncelB mosaicmerc@... [Homebrew_PCBs] wrote:
>>
>> You may find this useful:
>> https://hackaday.io/project/7938-pcb-smt-maker-lab-home
>>
>> I do single pass toner transfer -double sided with good registration
>> permitting a single etch .
>> Ancel
>>
>>