My PCB Adventures...
September 13, 2012
Inspired by Birdmun's adventures in PCB's I decided to try my hand at it. I'm no guru, in fact I'm pretty noobish to this whole thing but I thought I'd share some of the things I've worked out with the help of friendly LMR'ers.
All the equipment I'm using is standard stuff that some folks may already have around:
1. Laser Printer. I had an inkjet which will work using a different method that employs special boards made for UV etching but I picked up a Brother HL-2240 for $60. It was the cheapest no-frills LP I could find.
2: Lamitaning machine. You know, the little machines with heated rollers made for laminating Identification cards and such. Mine is a Scotch brand that I found at Wal-Mart for less than $30.
3: Copper clad PCB board. Radio Shack sells 4.5" X 6.375" double-sided boards for about $5. They're OK if your jonesing to get started but poor for making single-sided boards because you have to etch A LOT of extra copper which uses up your solution and takes longer to etch.
4. Etching solution. Once again Radio Shack comes to the rescue with a 16 oz bottle of "PCB ETCHANT SOLUTION" for about $10. A better, cheaper, stronger, faster solution (Pun intended) seems to be a mixture of muriatic acid and hydrogen peroxide. When I run out of Radio Shack juice I'm going to try it.. .So far I've done 7 small boards and I still have half a bottle left.
5. Magazines. I've had success with Popular Science but feel free to raid your old porn collection. It's OK, you can still get it on the internet.
6. Some TINY drill bits and a way to drive them. Dremel, hand drill, drill press etc. I'm using a cheap-O Harbour Freight table top model that I've had for years.
Your also gonna need an image file to print. I'm using Fritzing for now but it seems to have some limitations when compared to some other programs. This project is printed from a PDF file sent to me from Birdmun. It looks like a pretty cool little standalone ATtiny 85 board. I guess I'll know when it's finished!
OK,once the PCB transfer image has been generated, checked and is finalizzed I print it out on standard copy paper. It helps me to label the paper like this:
Once the image is printed I tape a page out of a glossy magazine over the area where the PCB traces are printed onto the standard paper.:
I try to leave a 1" border around the transfer so the tape won't interfere with the print. I'm using plain old masking tape.
I'm not sure if it makes any difference but I've been running the paper through the printer once with it flipped before printing on the final transfer. I figure it may help to warm up the paper and toner before the last shot. Don't forget to set the printer to the highest resolution before hitting PRINT!
Warming the rig up:
DOH!! I forgot to set the printer on the highest resolution:
Once the transfer is printed onto the magazine paper I prep the copper clad with 400 grit sandpaper. I couldn't manage a decent picture but I just make sure that any oxidation is sanded off and the board is nice and shiny. I then follow up with a really good cleaning with regular rubbing alcohol.
Then the transfer is taped to the copper clad. Again, I'm using regular masking tape. It's probably a good idea to keep the tape off the area that will be transfered.:
Just a little side note... Here is a transfer that sat unused for a couple of weeks:
The toner just turned back to dust! It seems that toner just doesn't like sticking to magazine paper!
Then it's through the laminator:
I've been letting the laminator warm up for about 30 minutes before beginning. I run the board through a bunch of times, flipping it over, turning it around and moving from one end of the laminator to the other. The theory is that this will give you more even heat transfer from the rollers to the board. I believe that "swapping ends" of the laminator allows the rollers to re-heat some as well.. The board gets really hot after a few passes.
DOH! Hair in the board:
So, that's why those guys in the Intel commercials are wearing space suits. Keeps pubic hair on the pubes instead of the chips...
Soaking the board in warm water:
After a few minutes the magizine paper will begin to lift from the copper and, hopefully, leave the toner behind.
The paper sticks pretty well to any big swaths of copper but it doesn't seem to hurt the etching process. I try not to be very aggressive when removing the paper remnants because it's easy to scratch the toner off the board.
The wording is supposed to read "BIRDMUN FLAMINFRO". FLAMINFRO is just something goofy I thought up years ago. You know, like someone welding or working on electronics sets their afro on fire. That plus a nod to Birdmun who was the inspiration for this bit of insanity.
Say, FLAMINFRO INC or
FLAMINFRO PRODUCTIONS or
FLAMINFRO HEAVY INDUSTRIES LLC...
I thought it was funny until my daughter asked why it says "BIRDMUN FLAMINFAG!!!
I was just experimenting with lettering...
I tried several different techniques for cutting the boards. Hacksaw, tin snips, shears, dremel, bandsaw... The best I came up with is a simple straightedge and a razor. I wish I could remember who recommended this method:
You don't have to bear down much to score the thin copper. Just get the first scoring straight and make a bunch of light passes with the razor. Then score the edge of the board making witness marks for lining the ruler up on the other side. Once both sides are scored they snap pretty cleanly and easily.
Now the fun part:
Meanwhile, after much swishing of the Radio Shack double sided board in the Radio Shack etching solution...
It doesn't take a great deal of solution, just enough to cover the board. Most folks with experience say it's best to heat the solution because it works faster but a warm tub-O-acid swishing in my lap...
You can also see where the acid has undercut some of the traces, The narrow strips of copper etch away faster that the wide areas so using double clad copper probably isn't the best to use for single side boards. It takes a long time to strip the component side and I believe the acid begins to creep under the toner mask. I'd like to order some thinner single sided copper clad and see how it works out.
Then it's scrub-a-dub-dub until the toner is gone:
Some folks have suggested acetone but I found it actually softened the plastic in the board and made a greasy mess... The plastic scrubbie and abrasive cleaner seemed to work well:
I'll probably trim it down to it's intended size and leave room for mounting holes.
Tomorrow we drill!
Well, I found a tiny drill bit. I'm guessing it's around .040" .060" from looking at it. I think it would be hard but doable drilling with a dremel or something. I'm using a small table top drill press. Just set the spindle speed as fast as it'll go.
A happy accident of the process leaves a dimple in the component hole locations caused by the raised copper traces. This acts a lot like a centerpunched or centerdrilled divot! If your careful it'll (mostly) self center the bit for drilling.
The solder glob is from tinning the trace around one of the VR pins. It slopped over onto the fill :( Note BIRDMUN FLAMINFRO logo. Bitchin' huh?
I'm thinking about a scheme to do the mask...
Well, I did the "silkscreen" part:
That's a bad picture of the part soaking. It's a lot easier to line up the silkscreen with the holes drilled. I held the board up to a light and got it "about right" before running it through the laminator.
I was surprised at how well the toner stuck to the plastic:
I just cleaned it with alcohol before taping the mask in place and ran it through the laminator as before. No etching this time :)
Anyway, I just wanted to share this with some other LMR'ers. I think the toner transfer to plastic could be useful for other applications like making switch panels and such. It would probably scratch off with a fingernail but I imagine covering it with a few coats of clearcoat may hold it in place.
Next : POPULATION EXPLOSION! Well, hopefully not the latter...
Here's the finished project: