Low cost DIY PCB Etcher & Exposer

Tips & Tricks
1

Hi there!

Found two interesting links on low-cost but anyhow good-working Etcher and Exposer for PCBs. Unfortunately the texts are in german, but I think the pictures are saying the most stuff anyhow. btw: I found that some time ago while experimenting with small roboters (but I discontinued that meanwhile - just no time!), but forgot that again somehow. Anyway:

Low-cost PCB exposer using parts out of (!!) bank note testers (!!): http://www.pixelklecks.de/1f40e2973f0cb1401/1f40e2973f0de5381/index.html

and the low-cost Etcher using a (NOW HOLD ON!!!) old coffee-machine (BELIEVE IT OR NOT - IT WORKS!!): http://www.pixelklecks.de/1f40e2973f0cb1401/1f40e2973f0df268b/index.html

Just click the pics to have an idea what´s going on. For all those people (like me) who do not want to spend 100 Euros for a Etcher and even more for a *good* Exposer and anyway do not want to step to something like the ironing method or similar.

Just as a sidekick also found on the upper page: You CAN print PCB designs on a normal inkjet-printer, the most (not all!) printers will block the UV-light. But you should use half-transparent paper instead of foil (the same paper used in school for redrawing technical constructions with ink). With using this paper on a normal deskjet or similar you *should* be able to have the same PCB-results as with a laser-printer as the paper will help to increase the UV-contrast (90% chance anyhow - depends mainly on the printer and especially it´s ink).

Greetz!

2

Man, that etch tank is cool as sh**!  - Thanks!

That’s a perfect idea with the heater. Makes you wonder why nobody already had one. Shame I can’t read it.

I built one of those flat “ant farm” fish tank looking ones a while back, with a heater and bubblers, and am kicking myself for making the internal volume so high. I have to use about a 2 litre bottle full of etchant to get it to the “safe” line on the 10" heater. >:(

It’s prevented me from even using my new sodium persulfate crystals, because I don’t want to have to mix up a big jug just to do some small-ass board (it has a “shelf life”). I may look into that coffee thing if I can figure out what they did. I’d even settle for just  the heater part.

I think we’ve got about five retired coffee makers around here. ;D 

George

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, and am kicking myself for making the internal volume so high. I have to use about a 2 litre bottle full of etchant to get it to the “safe” line on the 10" heater. >:(

Cant you put something inert in the tank but not in contact with the PCB?

4

Good idea (hadn’t thought of that)!

You mean like a big, rectangular brick of something to hog up all the space?

Should work, but I’d have to avoid the heater which occupies a couple inches over to one side, plus my bubblers are sitting down at the very bottom. They have suction cup mounts, but I was planning to attach them to a Plexiglas plate or something easier to get out (you can’t really get an arm down into this thing).

The other problem is, as much as I love the tiny “fizz” of bubbles, it is actually a bit strong. When I first ran it, I just dropped them into the bottom with their hoses, and eventually they shook their way up a bit higher. As you may have guessed, all the bubble activity didn’t seem to be too concerned with remaining in the tank, so I ended up with this brown “mist” of Ferric Chloride floating over the tank, and didn’t notice it until there was a nice brown “cloud” on the kitchen floor, surrounding the stand I had it on.

I could probably work out a way to keep them fairly low, but I’d almost rather figure a way to drop the heater and use less liquid. The heater was cheap as dirt at the PetSmart here, so I could probably just get the 6 or 8" model for a few bucks and suspend it somehow.

The etch quality with that thing was great (even with old FeCl3), but it’s way too much trouble to set it all up and clean everything afterward. I’m really thinking a simplified version of that coffee thing would help for small stuff, even if I had to agitate by hand.

Take Care,

George

5

Guys keep in mind that any amount of heat with FECL will cause it to outgas.  When it does outgas, even though you can’t really see it, this vapor starts attacking anything metal…Heated FECL definitely belongs outdoors.

If you are using toner transfer (not photosensitive process), get some “laser foil” from Pulsar, or Paper Direct, or your local office supply.

Its real use is for making gold/silver letters on certificates etc… use it the same way on your PCB before etching to strengthen the resist, then you can use a small tray and a sponge -barely- soaked in FECL to gently wipe away everything but the resist.

This method is faster, even without heating, than my pro tanks that use heater/air pump or even the heated spray etch tank…

Obviously you want a throw away sponge and latex gloves, etc.

Until I started with the foil I was running a gallon every 3 months or so with the big tanks, now I’m still using the gallon I bought late 2004…and my tanks should go on eBay soon  :wink:

Best Regards

Smash

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Smash,

Thanks! Yeah, the sponge thing has been on the back burner for a while now, because I’ve been waiting on making a DigiKey order, which will have some of that green stuff on it. I’ve heard great things about the sponge, but it sounds like you’ve verified it. I was afraid it would be more for really basic boards without much detail.

The tank here is supposed  to have a top, but I just used it that once because I was excited about seeing it work. I was supposed to do the top next. I really didn’t want to do the FeCl3 in it, I just didn’t want to waste my whole new thing of Sodium Persulfate for the one board. The tank was however, able to use three really old bottles of the Ferric, even diluted with water to fill the tank, and it did really well. I guess it was the heat and the bubblers.

You done anything big with the sponge, or anything with lots of small traces or hatch patterns? Seems like it would also be good for doing double sided boards, if it doesn’t put much slop around the edges of the current side. I’ve also recently seen that the TRF is supposed to stick to Sharpie touch-ups as well. :slight_smile:

George

PS- I did my last Core with some of the Sodium Persulfate, using some “ZipLoc” bag technique I saw. It worked OK, but it took forever. The mix was sort of guesswork, so that could’ve slowed it down, plus I later read that it not only needs to sit for a week or so after mixing, and/or needs a bit of copper already in it, to get properly activated. It’s in a bottle now, so I’ll be using it again soon (maybe on a coffee maker). 

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You done anything big with the sponge,

I did an 8x10 inch board using the sponge method, no problems related to the board size.

or anything with lots of small traces or hatch patterns?

hehe, everything I etch has lots of small traces!  :slight_smile:

Seriously though I always use a 16mil wide trace if it has to go between IC pads, and I never design anything through-hole with anything smaller.  6mil traces are possible (I have done some surface mount stuff unrelated to the MIDIbox) but there are a lot of other variables in your process that will dictate the smallest possible trace width.

Yet another cool thing about the sponge method is that it’s so fast you get nice clean edges, unlike a warm bubble bath that can seep a little under the edge of an “under-bonded” (is that a word?) resist and give you a case of the jaggies.

Seems like it would also be good for doing double sided boards, if it doesn’t put much slop around the edges of the current side.

Yes.  The key to this is leaving a “gripper edge” to handle the board with, so you can hold onto it during the etch without touching resist areas with anything but the sponge.  Etch first, cut second.

I’ve also recently seen that the TRF is supposed to stick to Sharpie touch-ups as well. :slight_smile:

No.  Dunno who says that, but it’s just plain wrong…They might be talking about filling in pinholes, and some of the foils will cover a smaller hole (due to a stiffer than needed formulation/carrier)…but the green TRF does not stick to sharpie ink.  It also won’t stick very well to pnp blue transfer paper resists…but transfers using the Pulsar paper or inkjet photo paper (which wants to ruin the fuser rollers in your laser printer!) work fine.

While we are on this subject, the best toner transfers are done with a photo mounting press and a timer, followed closely by a modified laminator.  No clue how well the baby laminator Pulsar sells now works, and I’ll never know since it won’t do standard thickness boards.  But the suggested large GBC laminator (TIA?) and modification guide he has there on his site work great, and are more consistant than anything I know save directly silkscreening the solder mask to the bare copper.

One of my best tricks for DS protos is to drill the bare/uncleaned/un-etched laminate on the NC drill, then lay a sheet of 1200 grit aluminum oxide sandpaper face up on a granite block (or well leveled concrete floor), then dry sand the board until it’s all shiny, moving the board not the sandpaper.  This removes any copper tearout from the drilling and levels the board out.  Makes it really easy to get the placement of the transfer papers dead-on accurate.  :)  Same method can be used without the NC drill, just make two transfers for one side (one to mark the alignment holes, then clean it off after drilling/sanding then apply both transfers)

Always wear a mask when using aluminum oxide sandpaper, two breaths of that dust is equal to years of sucking on lead in terms of memory loss.  :o

Best Regards

Smash

8

Thanks for the great tips!

The Sharpie/TRF thing (I think) was actually in the tips section or somewhere on Pulsar’s site, but I think it may have been user info.

I’ve been trying to be in a habit of leaving more space around my boards, because I’ve been having problems with poor transfers and etched through small traces near the edges. There’s really not much point in not  cutting oversize now, as I’ve got plenty of copper. :wink:

I’ve done pretty well with rough sawing with a hack or jigsaw, and burning down to my border lines with a belt sander, or sliding the board edge across a piece of sandpaper on a flat surface. Eats away pretty easily, leaving a nice edge, but ruins the heck out of the belts and paper.

I really want that laminator too. I’ve also got a 55 dollar gift certificate for Staples (they sell the GBC). There’s a whole slew of discussions on them in the Yahoo Homebrew PCB’s group these days, but that .03 thing sort of sucks to me. I don’t even own anything that thin right now, and my DS boards, believe it or not, or up in the .09x range. :o

I’m trying to look around for a larger one or something here, or anything I could maybe turn into one. Someone in the PCB group just had someone give him an industrial-sized free one, after putting up a local want ad. I think it needs a part or something, but would be well worth the repair.

If the photo mounting press is the same sort of thing a friend recommended here (some sort of T-Shirt machine), man that thing was high. I think the decent, entry-level ones were a few hundred dollars. I’ve wondered if any readily available heating appliances would work. My parents have one of those new “space age” looking George Foreman grills, with the removable plates for cleaning. With the plates out, it’s got two perfectly solid, smooth, flat heating surfaces, which press together when closed (actually, they might need thin metal spacers with the plates out, or the hinge could be adjusted). It’s also got a really fancy thermostat and timer. I wouldn’t trust myself to attempt any of that stuff without someone else documenting the procedure first. ;D

I hadn’t thought about the smoothing of the drill holes thing. I’ll usually do that after my etching, before fluxing or populating the board, but I can see the need for the DS transfers. I do it some, but not near enough (mainly to get the scratch crap off). It’s usually just with finger pressure from above. It probably needs more like you say, to get it back to smooth and flat, and the “stationary sandpaper” thing sounds good. I’ll do that on my next one.

Thanks Again,

George 

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wow this thread is a gold mine of info, thanks you guys.

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Just for everyones info, the jaytronics etching tank is $34 and includes a 1.5 gallon tank, board holder, bubbler, and heater.  just picked on up and it is a dream come true (etches in about 5 minutes)

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Just for everyones info, the jaytronics etching tank is $34 and includes a 1.5 gallon tank, board holder, bubbler, and heater.  just picked on up and it is a dream come true (etches in about 5 minutes)

Got a link to where to purchase one? I hit up Jaytronics site but was having a hard time finding it.

I currently just use a tray set in a bath of hot water, manually agitated, and it works out great. Then I use a cobbled together plastic / stainless steel double boiler to tin plate the boards. It’s a hack, but it works. (See a poorly laid out, but finished board here.)

For exposing PCBs, I use a standard 4’ two-tube fluorescant lamp set on wooden blocks 4" above a surface. Exposure is done in my laundry room, as it can be made completely dark, and I’ll use a clip-on light fitted with a red bulb for safelight-ish illumination.

-Steve

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U know, i spaced it and it is actually a philmore-datek kit.

http://www.philmore-datak.com/DATAK.htm

But Jaytronics stocks them. I also got a bunch of Datek stuff including the chemical tin plater so once i have a chance to make some boards i’ll post my results.  Their boards are designed to be exposed with a standard 100 watt lightbulb (10 min at 12") so hopefully these will work better than the GC ones i have been using