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Limits of at home pcb making?

Limits of at home pcb making?

2015-02-03 by soundmanok@...

Using 12 mil traces and 12 mil isolation on the ground plane. Dry film etch resist via wet lamination with lot,iron, and ferric chloride on a sponge. Exposing in a UV box for 1m15s. Developing in sodium carbonate and removing the resist with acetone.
http://i59.tinypic.com/33y6fec.jpg

Even at 12 mil, I get occasional microscopic bridges. Literally using a microscope to correct them.

I have a brother printer, toner transfer seems to work mediocre at best. I haven't tried it since switching off of copper chloride. The copper chloride left it super pitted and undercut.

Copper chloride I am finding has too many variables to use consistently. Was using a home made vertical bubble tank with an aquarium heater and it was taking 20-30 minutes to etch. Occasionally would add more HCl or let it rest to regenerate to that emerald green color. Only using about a little of solution, maybe more would help. Very random results. A spray tank it'd probably work amazing but those are cosrtly.

Anyway - any recommendations on avoiding bridges? It seems related to how long I spend developing. More care on that step helps a lot, mostly rubbing and rinsing. A toothbrush occasionally knocks off traces so I stopped with that. Anything better to use for developing? Should I cut exposure time down even more?

I'm getting better at the board making, but when I go to solder it I bridge everything and make a mess. Tried uv cure solder mask, which works really well, but its messy and impossible to get it to look good. Dry film solder resist seems really expensive.

And the drilling.....ugh.

I'm half tempted to just ship this off to China, dirtypcbs or something.

Any suggestions for process improvement?

Re: Limits of at home pcb making?

2015-02-04 by mbushroe@...

Dylan

   I have been using the "PCB fab in a Box" materials which use a special paper for easier toner transfer instead of dry or wet resist and UV curing. But it also includes a 'green foil', elsewhere sometimes referred to as "TRF" Toner Reactive Foil. This material goes through the same laminator that is used for toner transfer and causes the green 'foil' to get stuck on the toner. This makes the toner, which is in reality lots of little blobs mostly melted together and therefore somewhat porous into a more liquid tight trace. It is possible that the green foil can also be applied to the resist for the same function and cover and tiny gaps due to creases in the original dry or wet applied resist or dense spots in the paper or printout that shade some spots just enough to cause the resist to not fully cure.

   If the last problem is your main source of trouble, you might also try over exposing the resist to the UV until you start seeing swelling of lines and potentials for bridging, That might help the UV, and thus the cured resist 'spill over' into filling those really tiny gaps.

Hope this helps. But as I said, I have not tried resist based pcb etching, so I am only guessing there.

Mike

Re: Limits of at home pcb making?

2015-02-04 by soundmanok@...

Thanks!  Sorry, to be clear, with the UV resist method, there aren't gaps.  There are a few bridges, like the board wasn't fully clean before etching, or I didn't develop enough.  A very thin film may be left of the resist.  

James, that link is really good!  Thanks!

Re: [Homebrew_PCBs] Limits of at home pcb making?

2015-02-05 by James

Develop a bit longer, in sodium carbonate (i actually use percarbonate) 30g/L. Inspect carefully before etching, under microscope if you have it, clean up now is easier than after etching.

Etch a bit longer, inspect against strong backlight to decide when done.

To improve etch speed, use strong h202 (20-30%), add a cap to your etchant and mix before adding pcb, agitate etchant as you etch.

On Feb 4, 2015 6:08 PM, "soundmanok@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com> wrote:
 

Using 12 mil traces and 12 mil isolation on the ground plane. Dry film etch resist via wet lamination with lot,iron, and ferric chloride on a sponge. Exposing in a UV box for 1m15s. Developing in sodium carbonate and removing the resist with acetone.
http://i59.tinypic.com/33y6fec.jpg

Even at 12 mil, I get occasional microscopic bridges. Literally using a microscope to correct them.

I have a brother printer, toner transfer seems to work mediocre at best. I haven't tried it since switching off of copper chloride. The copper chloride left it super pitted and undercut.

Copper chloride I am finding has too many variables to use consistently. Was using a home made vertical bubble tank with an aquarium heater and it was taking 20-30 minutes to etch. Occasionally would add more HCl or let it rest to regenerate to that emerald green color. Only using about a little of solution, maybe more would help. Very random results. A spray tank it'd probably work amazing but those are cosrtly.

Anyway - any recommendations on avoiding bridges? It seems related to how long I spend developing. More care on that step helps a lot, mostly rubbing and rinsing. A toothbrush occasionally knocks off traces so I stopped with that. Anything better to use for developing? Should I cut exposure time down even more?

I'm getting better at the board making, but when I go to solder it I bridge everything and make a mess. Tried uv cure solder mask, which works really well, but its messy and impossible to get it to look good. Dry film solder resist seems really expensive.

And the drilling.....ugh.

I'm half tempted to just ship this off to China, dirtypcbs or something.

Any suggestions for process improvement?