trouble with making boards

Design Concepts
1

Can I get some advice from someone who clearly understands how to use toner-transfer paper?  Some time ago I posted something about making a simple mixer to mix the four outputs from a Midibox FM or a quad SID to a mono output.  I entered the schematics into Geda (href="http://www.geda.seul.org) and routed the PCB traces using PCB (same page).  I exported the foil patterns to Postscript format and with LaTeX made a full sheet containing some foil patterns I want to print out on the toner-transfer paper.  The resulting PDF can be found here http://www.cs.csubak.edu/~dgriffi/stage1.pdf.  The mixer is the smaller pattern printed three times on the lower half of the page.  The top half contains two copies of a two-sided board pattern for some mods I plan to apply to my Paia Fatman.

Would someone please take a look and tell me if there’s anything wrong with the artwork.  How hard should I press?  How long?  How hot?  With or without a sheet on top?

After blowing one sheet, I found that rubbing instead of simply pressing helps get things bonded, but I still keep getting lots of broken traces.  I’m about to sell this stuff off and go back to the photographic process.

2

Davo,

You’re probably describing the technique here-

http://www.fullnet.com/u/tomg/gooteepc.htm

I’ve been using that for lack of easy alternatives, and have even considered finding one of the laser printers like he uses, so I can print my own. The ones I’ve done have come from a copy machine at my father’s office. I believe the toner is about as important as the paper. The first ones I tried came from a local Kinkos (print shop), and they all but refused to leave the paper. I started off with the “JetPrint” paper Gootee used and then grabbed a pack of the new “Staples” paper he found. The Staples stuff works well, but it leaves a “residue” on the board, which you rub off with finger pressure. The old stuff more or less falls off on it’s own after a bit of time soaking. Rubbing the traces scares me, but he swears by that new paper, and I have had the old stuff pull traces off while I was peeling.

It’s not a bad method, but does take a bit of practice (which it seems you’ve had). I did one of the Willem EPROM programmers with it, and it had a bunch of those god awful traces that squeeze between IC pins, etc. Unfortunately, the exact amount of pressure and time is difficult to log and repeat, but the messy transfers are really easy to wipe off afterward, so you don’t waste anything. It seems every time I do these things I have to spend a about a half hour remembering my previous technique and getting clean transfers, so I try to throw at least a few of the same board on each sheet and bring home at least a couple (the paper is cheap as dirt). It may also be wise to get a few small practice transfers in and then start the bigger one, but my problems are usually at the edges, plus you may get lucky and dump a nice clear one while you’re warming up using the final board for practice. I’ve found that pressing too hard over the full board, or for too long, can blur some of the traces and I now prefer to focus smaller amounts of heat, pressure, and time with the pointed tip of the iron around the entire board over a bit longer total time. I still do the initial minute or two on the full board, but I don’t press too hard. I don’t think that lighter pressure with the tip, moving to different areas for a long time can do any harm, and it may insure that everything makes it to the copper.

I would try different types of copy sources first, assuming you’ve gotten one of the papers he likes. I may have gotten lucky with the copy machine I found. I do think I used a piece of paper over the back of the board when I ironed, but I see masking tape recommended. I’ve also backed the heat down a bit from max on the iron, and the one I use now, somehow seems to do better than my previous one, so you may want to borrow a different iron to double check. You shouldn’t need to follow his exact directions to get a good copy, or even replicate your own procedure each time. The initial attempts should come out fairly close with the right combination of paper, toner, etc.

I probably don’t know enough to check your layout for circuit errors. Hopefully, someone else here could. I have found it beneficial to beef up any thin traces if they have room surrounding them. This keeps them from coming up with the paper, if that’s a problem. I noticed a few skinny ones on your PDF. I also sometimes get pinholes in my larger ground masks from the extra time I spend getting the copper from around the smaller detailed traces, but that’s an obvious “etching” issue.

                                             Hope you can get it working!  :slight_smile:

                                                                                     George

PS- If you do sort it out, see if you can get good transfers to metal substrates. I’m trying to do that for my current box, but haven’t gotten around to the label stage yet. There’s probably a combination of metal and surface prep that would work for clean black labels.

3

I’m aware of the Gootee site and I’ve been trying what I see there.  The stuff I’m using are TTS paper and GreenTRF from Pulsar.  TTS is designed specifically for this application, but is quite expensive at $1 or so per sheet.  I bought it shortly before I found Gootee’s site.  The printer I’m using is a high end Xerox Phaser of some sort used for graphic arts at the local university.

I’m considering using the stuff Gootee uses to see if that works any better.  There are not Staples places where I live, so I’ll try one of the listed substitutes.  GreenTRF is a sealer that’s ironed over the toner to give a very tough mask.  There are other TRF types such as white for doing “silk screening” for the parts side of a PCB.  There are others for other purposes.

Now for a critique of this TRF stuff.  If you look at my foil patterns, there are some very wide areas.  It might have been my technique, but there were pinholes in the green stuff on those wide areas.  For the narrower parts, where I managed to get nice and sharp edges with toner here and there, the green was nice and sharp.  It covered all the unavoidable unevenness and pinholes in the toner and looks a lot like real silk-screening.  Applying full pressure from my fingernails, I cannot scratch it either by tapping or scraping.  It’s somewhat, but not really resiliant against getting banged with 1/4" plugs and MIDI cable ground shells.  Since the green stuff was meant to be removed with acetone, that may or may not be a concern for using it on front panels.  It might complicate spraying laquer over it too.  I don’t have any other TRF types, so I can’t comment there.

4

Sorry to ask Davo,

but are you sure that Xerox Phaser is a laser printer, not a thermal wax printer?  :wink:

Bye, Moebius

5

Yes, it’s a laser.  My first try with this paper was on a Laserjet 4050.  I got much nicer results with the Xerox, however that may have been just because it was a second attempt.

6

Thanks for the tip on the TRF paper! If it works halfway for labels and is available in white, it’s well worth the extra money. I had wished I could do that with the regular transfers, but it’s black on white only. I even considered spraying white rectangles on a panel with something and doing an inverted black/white text over them to show white lettering (probably wouldn’t work). I’ve gotten pinholes and stuff with large areas of black on the Gootee method too. I usually hit them with a wide tipped marker for safety, but I’d be more happy getting all the small stuff to transfer.

I was planning to spray my own topcoat over the black on silver labels, if they come out OK. I’ve done stuff before where I had to “mist” really light coats at first to avoid blurring and eating up the ink. Trial and error with some different clear sprays would probably find a good one.

Like I mentioned, I’m not really positive that I like the new Staples paper as much as the JetPrint. I got that EPROM board done with JetPrint and it was fine. Also, the Gootee laser printer mentioned on that site wasn’t much either when I looked. It was around $45 (US) in some places, and seemed like a common home computer printer. If I have time to try to find one, it may be worth having for other fast PDF prints and stuff. (I use crappy slow inkjets here)

-George

7

GreenTRF  isn’t paper, but a pigment powder of some sort on a thin plastic carrier.  I’m looking at the docs for the transfer paper and it says that the varieties of TRF are green, white, metallic (several colors) and clear.  The clear TRF is for making soak-off and dry-rub decals.  That’s probably most appropriate for doing front panels.  With a color laser printer, the results should be very nice.  I’m now sure how to get white on such a decal though.  You could probably lay down your backgrounds directly as if you’re going to etch the front panel, then apply WhiteTRF.  Then put a decal using ClearTRF over that.  See http://www.pulsar.gs/ for more info.

I don’t see why green or white TRFs can’t be used with the Gootee method.  They adhere to toner fused to metal, which is exactly what Gootee’s method results in.  For soak-off and dry-rub decals, you need the special gluey coating that Pulsar puts on their transfer paper.  That glue is washed off when using it to make circuit boards.