Homebrew PCBs

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
>>
>>