How to fix bad tracks resulted from bad film transfer printing

Discussion in 'The Projects Forum' started by m.yaser, Nov 28, 2010.

  1. m.yaser

    Thread Starter New Member

    Nov 28, 2010
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    hello every body
    i am a newbie and i was trying to make a pcb
    but now i am stuck with a bad board with low connectivity tracks
    I have done some troubleshooting with the multimeter and i Know exactly what bad parts needs to be fixed
    i have tried soldering
    but no use
    any idea about fixing these tracks ???
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Unless you have unlimited time to wire in traces, make a new PC board.
     
  3. m.yaser

    Thread Starter New Member

    Nov 28, 2010
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    thank you
    making a new one will save time and effort
    but i need to learn some troubleshooting skills
    what do you mean by wiring in traces ??
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    Consider where a trace should make a path from point A to point B and does not. The cure is to use a small gauge wire to make the connection.
     
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  5. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Inspect your board really well before etching. If traces look bad, either remove original resist and reprint or if only a few bad spots, you can touch them up with a permanent marker/sharpie or even nail polish.

    Before transferring to bard make sure you clean copper surface really good. Some use a nylon scrubber pad, others use a kitchen/bath cleanser like Comet or something similar. Either of those both clean and microscopically scratch the surface so toner can bond.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    I recently perfected my ability to make a home brew PCB using toner transfer techniques. It is hard to reject a pattern that is almost close enough, but it really is the best way to do it. If it isn't perfect then wipe it off with acetone and start over.

    Took me about 10 tries with an clothes iron, but I finally made one, and etched it. Afterwords I found a high quality laminator, which has improved my results a lot.

    http://www.electro-tech-online.com/...4601-diy-toner-transfer-paper-cheap-easy.html
     
  7. m.yaser

    Thread Starter New Member

    Nov 28, 2010
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    thank you all
    but I have another question
    what are the best dimensions to use when creating a layout for toner transfer techniqes
    thanks in advance
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    The best dimensions are the smallest board with the shortest and widest traces you can come up with that will satisfy the design criteria, including mounting consderations.
     
  9. wayneh

    Expert

    Sep 9, 2010
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    Can you point to a protocol you followed? I'm interested in being able to do this, but so far I've been reluctant to climb the learning curve. This is partly because I haven't really seen an end-to-end description, so I can't gauge what I'm up against.

    To the OP, have you though about conductive glue? you can repair traces by painting it on. It's a limited fix. I wouldn't expect to cover much distance and/or carry much current, but it can be used to bridge a gap or fill a crack. My biggest complain is that it's hard to work with at small scale. A 2mm bead is easy enough, but a 1mm or less bead would be really tough.
     
  10. Wendy

    Moderator

    Mar 24, 2008
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    More like a kludge of procedures you mean. My HP LaserJet 6P will not allow thick paper, which includes photopaper, to flow through any more. One too many jams I guess. Following the suggestion of Ron on another forum, I taped a sheet of wax paper (which is dirt cheap) to a sheet of regular paper, and printed the reverse image to it.

    The iron method works, but it is extremely finicky. The backing tends to suck the heat away unevenly. The laminator, set to its highest setting, doesn't have this problem. I run the wax paper through many times (8 is the target number), usually with a sheet of paper over the pattern to help it stay in place. After doing this the pattern is fused to the copper, and removal of the paper becomes the challenge (without damaging the pattern).

    I have found if you heat water to as hot as possible (I use the microwave) it helps a lot. Soak the pattern for at least 5 minutes, maybe more. After going through all the heating processes the wax paper has very little wax left, and will readily absorb water. After 5 minutes or more (make sure the water is still hot) start peeling the paper off. I've tried a soft toothbrush, cheesecloth (available from material fabric shops), and my finger. A little paper still on the toner (which is actually a plastic) is OK, just get it off the bare copper.

    Etch the board. I've been playing with a 2:1 ratio of hydrogen peroxide (nothing special, off the shelf) and muriatic acid (a swimming pool chemical, 30% hydrochloric acid). Gloves are a must (I use nitrile types), and wide open spaces. People have given me a hard time for doing it indoors, as long as you are careful I think it is OK. Of course, this is concentrated acid we are talking about, and something about the hydrogen peroxide give it an extra kick. Gently wipe the board while it is etching to get the oxide off, this speeds up the process enormously. I use a Q tip, other people have recommended a paper towel. Do not store etchant premixed, there is a chemical reaction going on between the hydrogen peroxide and acid.

    ALWAYS, ALWAYS pour the acid into the hydrogen peroxide. Getting this wrong will cause the acid to splash out of the container, possibly into your face! Do it right and it still smokes like something out of a 50's horror movie, and the liquid gets warm. Etching takes under 5 minutes, maybe a lot less. Safety glasses and gloves are a must, and lay out a wad of paper towels to put acid covered tools onto.

    I used a piece of disposable tupperware, marking the 2 and 1 points on the sides. This etchant is not as safe as others, but it is cheap and long term biodegradable.

    After you are finished rinse the board, wipe it with acetone, and rinse again. You can repeat the procedure (minus the etching) and create a component layout on the other side, which is cool and aids assembly a lot.
     
  11. hobby16

    Active Member

    Aug 30, 2010
    30
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    I'll add some tips I use in my toner transfer process.
    - I don't have a laser printer at home so most of times, I use my inkjet printer (HP PSC1510), spill laser toner on the printed sheet asap (before the ink dries out) and dust off the excess toner with an air pump. It's nearly as good as laserprinting provided you have the right type of paper : enough glossy not to absorb ink too quickly.
    - I agree that ironing manually gives unpredictable results but I finally got consistent transfers using a small stainless stell rod (scrapped from an oven grill) between the iron and the paper. The pressure is much higher and ensure better transfer. But now, I use a laminator which much simpler and convenient.
    - Instead of 6 or 8 passes (or even > 10), I've added a triac circuit to slow down the laminator's motor. The motor is ON about 0.5s then off about 8s, so just one pass is enough for a perfect and reproducible transfer. Once the laminator has started "sucked" the PCB, the is no need for attendance so you can do other things until it's finished. But the great advantage of slowing down the laminator speed that way is the reduced risk of misalignment (with normal speed, the paper doesn't stick to the pcb in the first 1 ou 2 passes so for double sided pcb, alignment may be tricky).
     
  12. beenthere

    Retired Moderator

    Apr 20, 2004
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  13. Wendy

    Moderator

    Mar 24, 2008
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    I tried it once, never did get it to work right over several attempts. The toner worked first time.
     
  14. beenthere

    Retired Moderator

    Apr 20, 2004
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    Maybe the exposure frame helps. My only problems came from too long an etch and undercut traces.
     
  15. wayneh

    Expert

    Sep 9, 2010
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    So, the ideal situation would be to print toner directly on the board? Assuming there aren't many printers that can do that, people have devised ways to transfer the toner from something the printer can handle onto the board? I understand photo paper but I don't understand putting wax paper thru a laser printer. Doesn't the wax melt and gum up the printer? Does the toner get put onto the paper, or the wax paper?

    Sorry for the silly questions. Having lab experience, the etching process sounds like a snap. It's getting the image onto the copper that baffles me.
     
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