Project: LED based UV exposure box for PCBs

jpanhalt

Joined Jan 18, 2008
11,087
You need transparencies specifically for ink jet, if that is what you are using. Cheap ones may still have a pretty coarse graininess to them.

If you can find the transparency film by Pictorico (made in Japan, Pictorico Premium OHP Transparency Film), you will notice that the texture is very different. I believe they have a microcrystalline inorganic coating -- of course details are lacking. With a pretty strong magnifier, I cannot see any beading up or cracking (HP ink). Others have reported using Vellum, if it is still available, and regular tracing paper. I have no experience with either of those media.

John
 
I hate u guys.... U are doing what I cannot. and I want to do this rather badly.

OK..I don't hate you..Love what you have done.
I cannot get wax paper, I cannot get ferric easily..

So what will be the easiest way for me to etch PCB's....I think I can buy ferric balls kinda a thing that should be added to water to make the chemical....I heard this from someone.
Some one really need to give me some heads up on what is the best method for me...
I can buy UV leds off ebay. so Mark..any pointers?
First post here.. So be gentle guys.. :)

There is a way..

Like you, I have no local source of etchant, and didn't like the sound of using glossy inkjet photo paper in a laser printer. Lots of horror stories about the printer binding up with melted plastic coating from paper it was not intended to print on.

I have no idea about the photo resist method. But I'm just starting out with toner transfer on plain copper boards, and I'm having some good results.

If it makes any difference, my printer is a Samsung ML1910, and I'm using the toner that came with it.

Usual disclaimer. Not my fault if you damage any equipment or poison yourself.

Paper...
If you can't get waxed paper locally, try glossy junk mail paper. The stuff you are looking for is about as stiff as ordinary printer paper, so it doesn't need to be taped to anything. Plenty of instructions on how to do toner transfer here and elsewhere, so I'll leave that to those who know better. Magazine paper might also work. Ignore any print on the paper. Only the toner will transfer to the board.

Put a sheet or two of ordinary paper between the transfer paper and the iron, so the coating doesn't come off on the iron.

I tried matte inkjet photo paper, and got quite good results, but the masked copper did seem to get a bit pitted. The glossy junk mail paper gave a far better result.

Etchant.. One that you can make from easily obtained supplies.. :D

Definitely works with toner as an etch resist. No idea if the photo resist works as well. It's slow, but it does work. And you should be able to find all the ingredients locally.

1 part vinegar
1 part 3% hydrogen peroxide(if the percentage is different, adjust accordingly)
A couple of spoons of salt.
A board to be etched.

Pour the peroxide in first, then the vinegar.
Add masked board.
Sprinkle with salt. Keep adding it until bubbles start to come from the board.
If the bubbles stop, add more salt.

Not 100% sure if agitation makes much difference. But heat seems to. I've only etched three small boards so far, so I haven't got it down to a fine art yet.

You should see the copper start to turn brown first. and little trails of bubbles come from the copper. Even when it is not bubbling, the etch is still working. but very slowly.

One advantage of this over ferric chloride is that it is easy to see how the board is coming along.

Be careful The ingredients are harmless by themselves, but mixed together, they etch the copper away, and would likely do the same with your plumbing. No idea what they do to skin, and I'm not brave or stupid enough to find out.
The etchant also contains copper ions, so do not drink, lick your fingers or eat while etching. Rubber gloves are also a good idea.

It turns from clear to a pretty blue colour during the etch, so make sure that any kids or pets that may be around can't get at it.

Make up as much as you need for that session, and if it stops reacting, then make a fresh batch, and pop the board in again.

A nice write up on the whole etchant process here.. Which is where I found out about it.
http://www.stephenhobley.com/blog/2...ng-with-forces-i-dont-understand-the-formula/

Ignore the twit in the comments who is claiming it's a hoax. It's not.

I can only get 6% peroxide here, so I make up 2 parts vinegar to 1 part peroxide. Like I said, slow, but it works.

Hope this helps.
 
Turned on now. I think. But I couldn't find a way to PM you.
I've messed up somehow haven't I..
Please accept my apologies. What ever rule I've broken was unintentional.
 

MarkE

Joined Jun 13, 2011
2
Hi everyone,

I have recently build my own UV exposure box using LED's after seeing a article on instructables. I found some UV led's on ebay (item id 300547643714) and made myself a board almost 5x7" with 120 led's populated running in groups of 3 with a resistor off a 12 volt supply. I have a glass sheet recovered from an old picture frame held approx 2.5 to 3 inches above the leds.

I have made a few boards with this but everywhere I look where people have built their own UV-LED box's there is mention of 5+ minutes exposure time but I currently find that the board is badly over exposed with 25+ seconds exposure. At the moment I find 15 seconds is more or less perfect each time and that is with tracks of .2mm.

Obviously I am not complaining about the time it takes but I wondered if there was a reason this is not good? ie is there an advantage to having a box that takes 5/10+ minutes to expose the board?

cheers
Mark
 

Thread Starter

Markd77

Joined Sep 7, 2009
2,806
There aren't any real advantages to a longer time. I didn't really know how long it would take when I made it, but I don't mind waiting 3 minutes. I think commercial UV tube boxes take under a minute. I suppose less time soldering the LEDs could be considered an advantage, but it wouldn't take very long to solder 120 LEDs.
 

MarkE

Joined Jun 13, 2011
2
Hi,
sorry my question was probably not asked that well.

What I am saying is that when putting a transparency and photo-resist board on my setup I find that the pcb is ready for developing after only 15 seconds of UV light.

Cheers
 
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