my boards aren't turning out

mik3ca

Joined Feb 11, 2007
189
So I did a double sided circuit board. and after etching one side, it seems that there are multiple random cracks in my traces. It seems that in order to get my board working, I have to patch those tracks up.

At first i thought it was my old laser printer (samsung ML2510) that may be causing the problem since it did not print the tracks properly on the transparency. When I first had that printer, it was working for me perfectly, although at that time (6 months ago), I used whatever transparencies they were selling behind the counter.

Now I figure I should replace the printer, so I did. It is now a Brother. I get the same results on the transparency.

All my transparencies were purchased from Grand and Toy.

When I was looking for some transparencies, I saw ones for laser printers, ones for inkjets, and ones for photo copiers.

I'm beginning to think I should go for the photocopier transparencies, but sources claim I should be going against them.

I'm gonna continue to blame laser printers for my problem.

What do you think?

HarveyH42

Joined Jul 22, 2007
426
I don't do photoresist, so you'll probably get better advice from someone using that method. Toner is porous, won't completely block the light. Have read that inkjets are much better for this. Also, your lamp maybe too bright, maybe enough to get around the transparency a little.

There are a lot of different toners, grades, quality, melt temperature... Mostly they look great on paper, that's the goal. Using them for photoresist or toner-transfer (my favorite), is just a bonus for us. Might not be the transparencies, printer or lights, but poor quality toner. My HP cartridges are $70 new (printer cost$120...). Haven't tried refilling (got 2 years off the first one, and get good results, not worth the gamble).

How fresh are your boards? Not sure if anything has changed in the past 20 years, but there was a shelf life, and storage considerations. Maybe a bad production run, wouldn't think it easy to spot.

SgtWookie

Joined Jul 17, 2007
22,210
You probably would have been better off going with an inkjet for your transparencies.

Laserprinters have to fuse the toner to the plastic by using heat and pressure. The heat and pressure distorts the transparencies, causing minute cracks in the applied toner.

Inkjets simply spray the ink on the plastic. No heat is necessary, so the chances for distortion is minimized.

As a make-do, you could inspect your laserprinted masks using a bright light on the underside and a magnifying glass. Touch up any cracks using some flat black paint and a fine brush, or a toothpick.

n9352527

Joined Oct 14, 2005
1,198
I haven't done photoresist for a long time. Back then, I didn't use transparencies but that milky transparent paper, I think it was some kind of tracing paper with different thickness. The thicker ones were perfect for laser printer, giving homogenous black traces. Especially when the printer was set to darkest setting. The printers were old QMS and HP LJ4. It might be worth a try.

I'm now using cheap photo paper (one pound for 15 A4 sheets) printed with Samsung ML6060 and transferred with clothes iron, which gives better result, quicker and cheaper as well.

jpanhalt

Joined Jan 18, 2008
10,068
The fact that there are so many solutions, means none is trouble-free.

I have used photoresist for 10 years or so now. Never had a problem with inkjet and a very nice transparency film called Pictorico (used to be AGA, now Mitsubishi). The problem I had with older transparency films was the coarseness of the coating that keeps the ink from beading up. Pictorico is extremely fine, and its main use appears to be as an artistic medium. Well, Pictorico has become almost unavailable. The newer version is sold with the added feature of being UV opaque. Not good. Moreover, my inkjet cartridges dry up before I use anywhere near all of the black ink in them for PCBs. So, I am looking for a laser printer method to make good transparencies.

I have considered applying a secondary mask with a product used in toner transfer to make the transparency image truly opaque. Pulsar sells "GreenTRF" . There is another art product called Colormaze that some people report using in the same way. These are heat-transfer, metallic-like films (sort of like gold leaf) that stick only to the toner. You do not transfer the toner. One simply makes a laser transparency, then laminates the metallic film, peels off the film and is left with a fine lined, truly opaque transparency.

The second step in the proposed method can be done with any laminator (non-modified) or by simply placing the metallic foil against the transparency and re-passing it through the laser-printer fuser a second time. The number of people who have reported using GreenTRF or Colormaze in this way is very limited, but I think it has promise.

John

mrmeval

Joined Jun 30, 2006
833
The method used for laser printers is to print on inkjet paper then iron that onto the PC board and use water to get the paper off.

As stated if you're using the photo exposure stuff the other advice here applies.

BTW Staples had a paper that worked well, it's been a while though. YMMV

mik3ca

Joined Feb 11, 2007
189
my "lamp" is a blacklight.

I have tried inkjet before I tried laser printer. I find that both results were similar except for a few cases where the image came out nice and sharp on a laser printer. At the time (6 months ago) it was a samsung ML-2150 I had that did it right for me.

I think I should try the transparencies meant for photocopiers and see what happens.

SgtWookie

Joined Jul 17, 2007
22,210
Photocopiers generally pass the printed material through the fuser pretty quickly; they're higher speed than your ordinary laser printer. Beware that you may wind up with melted photocopier transparency plastic all in your fuser assembly.

But probably not as big a mess as you'd get if you tried the transparencies made for inkjets.

One of your high priorities should be freedom from distortion (ie: even minor changes in sizes of the transferred image). Try printing out your pattern on plain paper, and then see how closely an image printed on your laserprinter transparencies are to the plain paper printout. Then try the same experiment with the photocopy transparencies.