Yahoo Groups archive

Homebrew PCBs

Index last updated: 2026-04-28 23:05 UTC

Message

Re: Heater for Etchant Bath

2016-11-10 by Kamen Lilov

>> Hi,
>>
>> Microwave? Heh heh that's kewl. I'll have to try that.
>>
>> 8 minutes is very reasonable.
>>
>> However, I reliably etch 6 mil traces in about 45 seconds, in a cup of hot acid using a sponge.
>>
>> We each have our own schemas, I tip my hat..

Come to think of it, I'd like to share a bit more of my process.

I don't do laser and ironing (although I have LaserJet 2100 to print on drafting paper, or for traces under 10mil I give the job to a local shop with a phototypesetter on film)

I always do UV. Works very well for double-sided boards.

I cut the PCB material with an extra centimeter around the perimeter. UV work tends to be super precise, but quality decreases around the edges. In that extra centimeter, I place three vias/holes, two of them 1mm, one 2.5mm. With these, I can achieve excellent alignment between top and bottom masks.

I tie a piece of wire in the 2.5mm hole. I use it to slosh the board around in the developer; then, cold water wash, then etching in a 50C FeCl3, tupperware container, again moving the board around by that wire. Then a good wash again.

I then score the PCB along the 'real' dimensions, preparing that 1cm extra for removal. I drill, remove the lacquer with acetone, and maybe add a chemical tinning step (only if warranted)

Next, I make 'vias9; with pieces of 0.7mm wire in 0.8mm via holes. The extra perimeter stuff still helps at this point, to hold the board in a vise.

Then, a was with soap, good drying, and I just snap the perimeter pieces off, sand the edges, and coat with flux pen.

Then it's on to component soldering, or perhaps keeping it in storage for a couple of weeks until I find the time for soldering and debugging :)

Two key lessons from the above:
* If doing UV masking, leave extra perimeter space. The masking there is always mediocre compared to what's in the center.
* A wire is probably the best way to agitate your PCB in chemicals, short of a full-blown specialized FeCl tank with heating and bubbling.

Attachments

Move to quarantaine

This moves the raw source file on disk only. The archive index is not changed automatically, so you still need to run a manual refresh afterward.