Mine is a LaserJet 6P, about as basic as it can get. When it was new (to me) it would do photopaper, now it won't. It could have something to do with the plastic transparencies that jammed in the fuser. I downloaded a complete service manual and took it apart entirely to get the small chunks out.

I read about wax paper on another thread. It soaks hot water like crazy after the process, so I don't think their is too much wax left after I'm done with it.

 

OK, I am now a veteran. Sort of.

To answer your original question, a sharpie makes a good touch up on the PCB with toner on it before etching. I used it with perfect results.

I bought a ABC HeatSeal H210 Laminator for $30 while I was at Tanner's. The results are extremely good. I followed the advice given from another thread at Electrotech, and fed it through 8 or so times. I used both wax paper and high gloss magazine paper, both with good results.

One thing I found I was doing wrong is not heating the water used to remove the transfer medium. I tried a microwave, got it to almost boiling (maybe to boiling) and let the paper soak for 10 minutes at least. The idea is to soften the paper as much as possible (after going through this process there will be no wax left in the paper, and it will soak water).

I followed Mr. Gootee's advice and bought some cheese cloth also. Not sure how much help it was, but it did make it a bit easier.

The results were quite good, excellent even. Looks like I have a working process.

I also used the 2:1 Hydrogen Peroxide/Muriatic Acid. This is highly reactive. I would rate it as dangerous on the short term even though it is environmentally friendly long term. I probably threw two batches of perfectly good etch away after making a board. My boy was curious what it would do to aluminum foil, it ate it like ice in boiling water (looked like it too). The copper on the board was gone in about 3-5 minutes, I used a q-tip (several of them, it ate them too) to rub it off and speed up the process. Nitral gloves are an absolute necessity, this is acid after all. Being a clear solution it was easy to see what was happening too, another bonus.

 

I also used the 2:1 Hydrogen Peroxide/Muriatic Acid. Being a clear solution it was easy to see what was happening too, another bonus.

Agreed. Probably worth adding that Hydrogen Peroxide/Muriatic Acid etching should NOT be done indoors, and puts off noxious, flammable gas.

AMPLE fresh air is a REQUIREMENT. (And dont pour it down moms stainless steel sink)



It is quite amazing to watch the copper dissolve.

If you do this on a 90+ degree F day, you can really get a show from it.

The heat speeds up the reaction..sometimes too fast where it will start eating traces before other parts of the board are etched. Agitation and consistency is key.

 

I did it indoors. It was impressive watching the acid go into the peroxide, it smokes like a grade B Sci Fi movie. Warms the liquid nicely too. As the copper disolves into the etchant it turns a pretty green.

This is a dangerous etchant, unlike Ferric Chloride (which is merely a pain in the butt). 30% solution of Hydrochloric Acid doesn't sound like much, but it has a heck of a kick. It is a lot cheaper than Ferric Chloride too.

 

I did it indoors.

Ugg!

[smacks the forehead]

Sarge, where is that cattle prod? Batteries cost is on me!

 

I never use the muriatic/peroxide mix indoors; it's just too hazardous for that.

I'm out in the garage with the door rolled all the way up, with a big fan blowing the fumes out, and a big bucket of fresh water handy in case of an accident/spillage.

It's not worth risking your health to take chances with the stuff.

Note that you can re-use the etchant for a few days, but don't try to put it in a sealed container right after use; it will continue to heat and emit gases for at least several hours. I'd put some used muriatic/peroxide etchant in a re-marked brown peroxide bottle and screwed down the lid; next time I looked at it, it had swollen to about twice it's original size! I was lucky it didn't rupture.

 

I can give you the recipes for Injectorall

I gave the transfer method several honest tries, but it never came anywhere close to photoresist. I was lucky enough to buy a case of MG's photoresist before they stopped making it. But I'm running low so if possible, I'd like to try this formula;

 

If you have not tried different toner, that can be your entire problem.

 

That, and the temperature use to transfer toner is much more critical than it seems. If you want to send me a sample of a pattern I can try using the laminator and etchant on it ( and mail it back) so you can have a baseline. The laminator made a huge difference for me.

Since I don't use eagle or any other standard PCB software make it a standard graphics package, something I can print on my printer. This is meant to be a sample, not a project.

 

Injectorall is a slightly different resist than MG. It is a different color (sort of cinnamon color), but the big difference is that you will need a stronger alkaline developer to remove the exposed areas. I have tried relatively mild developers, such as sodium carbonate or sodium silicate (water glass), without success. For developer, I just use 0.5 molar KOH or NaOH in water. Both dry chemicals are readily available, and KOH is quite popular among the biodiesel crowd.

For KOH (MW 56), dissolve 8.4 g of KOH crystals in 300 mL of water.

For NaOH (MW 40), dissolve 6 g of NaOH crystals in 300 mL of water.

After exposure to the near UV, I immerse the PCB in the developer. It is still sensitive to UV light at that point, so do the development in a dim room or one with incandescent lights only. The UV-exposed resist will turn purple and float/wash away. I then rinse quickly in running water and use a small piece of cellulose sponge dipped in developer to go over the tracks and ensure all of the exposed material is removed. The unexposed resist is actually quite durable and development time up to a few minutes is not critical. At worse, you will see the resist getting thinner over the non-exposed areas. Note that the edges of the board my have little particles of FR4 or copper shavings from the cutting process. Be sure not to get those on your sponge, or you might scratch the resist.

After etching, the resist is removed by using a stronger alkali solution (about 1 molar). I just add a small teaspoon of NaOH or KOH to the used developer.

The greatest variable is exposure time. Once you know what you need, things go pretty flawlessly. For my first attempt years ago, I used an exposure of only a few minutes based on what I had read. That was not adequate. My exposure time runs about 12 to 15 minutes. I hold the transparency (ink side facing the board) flat with a piece of single pane glass and clips. If you use thinner glass or a vacuum hold down, your exposure time might be shorter. Window glass does absorb some of the approximately 390 nm light needed by the photoresist resin. The lamps I use are the F15T8-BL at about 6" from the PCB. I used to use just one lamp with an aluminum foil reflector resting on the bulb. That worked fine for boards up to 3" wide or so. Now I use an exposure box with three lamps that I inherited. Exposure time has not changed much, but I get a more even exposure for wider boards.

I keep lab notes out of habit, so if you need more details, let me know. John

 

If you have not tried different toner, that can be your entire problem.

The Stock toner by Brother has transfer issues, it used to not work at all, and better to assume it doesn't.

HP Original toner seems to work fine for transfer, this would cover most of the Dell Laser Printer line, as most are re-branded HPs with a few changes.

Color copiers and printers using black work also, no clue about actual colors, but the Dell color ones work fine on black output that I've used.

Most (not all, especially Brother All-in-One types) photocopiers work fine, if you print out on an ink-jet or non-compatible printer, make a copy of it onto press n peel or photo paper and iron it on.

Aftermarket toner seems to work OK. Lots of people report success by switching to an aftermarket "toner refill" on their printers that wouldn't work with stock toner (such as Brother).

 

Injectorall is a slightly different resist than MG....

much appreciated. Sounds like your procedures are very close to mine. one thing I do is print 3 copies of the art work onto mylar and stack the images on the supporting glass.

 

I have never had a problem with bleed through of the transparency, as I usually use an inkjet. For laser printer, this might be of interest to you: http://forum.allaboutcircuits.com/showthread.php?t=12474

John