[rembrant]

You should time your exposure based upon a test of exposing a long thin piece of the board 1 min at a time. Say start with a board with several pieces of tape and pull off one piece every minute and then etch. It should give you a good idea of how long you need to expose your board with whatever light source you are using. You can get UV lights at the pet store. I have seen poeple make a light table out of an old scanner body. It is delineated and already setup for accurate placement. Just strip the guts and insert your light source under the glass.

 

[linuxworks]

an old flatbed scanner! great idea.

I also saw someone build a UV box inside an ATX computer case (spare case).

in my old photo film days, we used a circle pie chart foil that you could place over the photo paper (under the enlarger) and it would be graduated degrees of grey on the transparency. you would expose for a fixed time and then simply look at the pie sector that gave the best result - and read its number from the developed print.

your tape trick is similar to this. sounds like a one-time calibration is needed and then you're all set.

 

[BrianDonegan]

I expose my boards using a standard florescent light (dual 30W bulbs). I place the board on my bench, then the film, then a sheet of glass, then suspend the light about 8 inches over it. I expose for 10 minutes, then develop quickly. works very very well.

 

[linuxworks]

brian - do you find you have to 'rush around' in a darkroom environment or can you be more relaxed in normal daylight as long as you are somewhat quick about it?

I hate darkroom work. I hoped to have left that behind when I bought my first non-film slr

 

[BrianDonegan]

I have one of those clip-on work lights that I use when doing remodelling projects, and use it with a red light bulb (about $5 total). I just use that while getting ready, but might be overkill. After exposing I casually walk into the other room with the utility sink past other lights, and develop under more florescent lights (developing takes less than a minute).

 

[rembrant]

If I had the know how I would build a small cnc machine and run my prototype boards that way. It takes the pain out of drilling through holes too. Honestly though, with houses like batch PCB, you can get some decent boards for a pretty cheap price. Certainly when you factor in your time your making out.

LumenLab has a small cnc kit available for around $500. I was thinking I would cheap out and build something with wood and a dremel tool as a cutter head. I won't be cutting any metal. Once it is built you only need boards and bits.

 

[1amigo]

Hi Fred,
With the iron set for "Cotton" (max.temp.) , should we keep the iron moving on the paper or leave it on the paper. For how much time, we have to do it, please throw some more light.
Thanks.

 

[mono]

1amigo, it's an old topic, Fred may not be monitoring it anymore.
 
I keep the iron moving but move it very slowly.  I'd assume the minimum length of time would depend on how thick your copper is and the total area you're covering... some small PCBs stay entirely under the iron during the process.  For something approx 4 x 6" or smaller, about 30 seconds total for 2 or 3 oz copper and B&W laser toner.

It should also be noted that toner from an old B&W laser tends to have the highest melting point, then a little lower is  toner from a modern B&W laser, then lowest is black toner from a color laser printer. 

Apparently they put a lot more wax or something in the color laser's toner so it has the same glossiness as the other colors.  That's also something to keep in mind when experimenting with what releases and sticks to the copper clad the best. 

I feel the color laser's black is easier but for tight spaces and delicate traces they can bleed a little.  It might also depend on the paper used, I have not done comprehensive tests of all possible combinations and I'm not very picky... often I'll touch up a pattern with a lacquer marker instead of redoing it, or even draw the whole thing with the marker if I really don't care what it looks like.

 

[Fred_fred2004]

I keep the iron moving but I use the tip of the iron this gives a much higher pressure on the pcb, so I go up and down the board pressin firmly on the tip of the iron, then I rotate the board 90 degrees and repeat I do that 4 times to ensure that I have covered the board and all the edges, if I'm doing a large board with say 10-12 circuits I take longer the trick is to get the whole board throughly hot so a small board takes only a few minutes but a large board I might take 10 minutes
 
my laser is a samsung black and white, simply because its what was on special the day I bought it and I use matt photo paper the gloss does not work as well (at least for me)
 
cheers
FRED

 

[zammykoo]

Quote:

...I use matt photo paper the gloss does not work as well (at least for me)

I have had good luck with using paper from free junk mail catalogs, especially the super thin and glossy paper like the kind used in Bed Bath & Beyond catalogs. Of course YMMV.
 
I just cut a sheet out and tape it onto a regular sheet of printer paper before printing.

 

[BenAdamson]

I have to say, photoetch is the way to go.