[Questions] UV PCB transfer

[lolbou]

Hey Mike, you don't mention how you etch afterwards (chemicals?)... I'll try my setup ASAP to see if it's efficient...

Considering you do it ok with black light tubes, my guess is is will be efficient! My box might be a useful project to share?

Oh, to have better contact between pcb and transparency, I put some foam in the lid of the box, slightly emerging so that when the lid is shut, you gently press the whole assembly. I put a CD in it and shaked the box, and that's not moving a milli-inch...

[chicago_mike]

I used to etch the ammonium persulphate method...it works but I ended up mixing the stuff so strong it would take up some of the weaker traces right off the pcb.

So last time I etched I went reight back to ferric chloride and just used super hot water. I had the dry stuff you mix with water...etched the board in no time and didnt take any traces off. Clean up was easy too.

[chicago_mike]

Note: I recently tried Caustic Soda / Sodium hydroxide / rooter powder drain opener ( all the same )

The formula is way to picky to get good results. So I am going back to the little 9 dollar bottle of remover for removing the unused resist off the boards.

I'll be adding one more blacklight next week for larger boards too. I leave the bulbs on for about 17 minutes..possibly way more than I need too, but this method works great. As cheap and hill-billy as my method is.

For GOOD household chemical etchant..meraic acid 1 part, to 3 parts hydrogen peroxide. maybe a 1 to 4 ratio even. room temp or warmer peroxide.

[Kilby]

Note: I recently tried Caustic Soda / Sodium hydroxide / rooter powder drain opener ( all the same )

The formula is way to picky to get good results. So I am going back to the little 9 dollar bottle of remover for removing the unused resist off the boards.

It depends on the resist, some resists are fine when using NaOH others brands are a disaster

For the board I'm currently using (available over the counter locally) 1.5 teaspoonful of NaOH in 500ml water @ 25C works fine.

Id suggest finding a combination that works reliably and sticking with it as long as possible.

[chicago_mike]

I get my boards locally as well, they're not MG Chemicals, wich I thought they were. But some local brand, can't remember the name off hand.

But with the chemicals I buy from them everything works a treat, its just 9 bucks a bottle.

[JOHNO]

Ive been photo etching a few boards but havent done any for a while. so i expose the boards under fluro lights and stick it in the developer and some times all the resist comes off the board. Am I leaving the board in the developer to long?
Johno

Crap this is in the wrong place

[chicago_mike]

1. What is your etchant? I use a 4 to 1 or more of peroxide / muraic acid.

2. How do you develop the transfer? how close is the light source?

3. do you have a clear sheet of plexi to help hold the transfer onto the pcb and is there a gap?

and who makes the board? Ive been using mg or gc boards and they work very well.

Im going to replace my blacklights or add more as two dont give as good cover for bigger boards.

[JOHNO]

I use ferric chloride to etch the boards.
I devolop the transfer with a fluresant light about 2" above the pcb and yes there is a piece of glass over the pcb and the transfer. I use two clear tranfer sheets taped toghther so its really dark. To develop the boards i use "universal developer" from RS components. The boards are also from RS. But the problem isnt in the etching its when I drop it in the "universal developer" all the resist comes of sometime. I think Im leaving the developed board in the developer for too long, but its only in there for about 30 seconds. The develper is a powder type and i measure it out very carefully on my powder scales.

[chicago_mike]

hmmmm..

Not sure. hot water or room temp?

[JOHNO]

About 50 degrees. Too hot?

[chicago_mike]

Ferric Chloride? nah...I used steaming hot water a coup[le times and the etches came out perfect.

[JOHNO]

50 degrees is the temp of the developer not the ferric.

[chicago_mike]

doh