Project: How to make PCBs

Discussion in 'The Completed Projects Collection' started by Wendy, Dec 29, 2010.

  1. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    Notice: Several of the process that will be shown are very hazardous if not treated with respect. If you try to replicate these results you do so at your own risk. These process are carefully and safely performed by hobbiests all over the world, and I am not responsible for accidents.

    by..................Help with pictures by
    Wendy Marsden......Jim Marsden (AKA, TheFox)

    List of Materials
    Nitrile Gloves
    Safety Glasses
    Apron
    Paper Towels
    Muriatic Acid (swimming pool chemical, AKA hydrochloric acid)
    Hydrogen Peroxide (sold at any pharmacy or grocery store)
    Acetone
    Pure (91%) Isopropyl Alcohol
    PCB stock (copper clad printed circuit board stock)
    2 pieces of 8X11 scratch paper
    Scotch tape
    Wax Paper
    Scotch Brite scouring pads
    Tupperware container (large enough for PCB stock)
    Tupperware bowl of water
    One large glass for water (bigger the better)
    Soft sponge (disposable)
    Laser Printer (and finished print)
    Laminator
    Microwave oven (to heat water)
    Dremel Drill Press


    There are many variations on how to DIY printed circuit boards (PCBs). I am not going to recommend any method over the other, but show how I do it with pictures. One of the oldest ways is with photographic techniques. This works, but it isn't how I do it. As far as I can see, all the techniques have points where it is finicky, where it seems it can go badly wrong. Basically the hobbiest just has to keep experimenting until they solve all the various problems that come up for their own home setup.

    I use the toner transfer technique. It also works well, but only with some laser printers. I bought a laser printer specifically for this job (though it does occasionally print other jobs out too). It is a HP6P, an old but reliable workhorse of the HP laser jet series. I paid around $30 for it. I had to download a manual soon after because some of the materials I tried for the transfer medium wrapped themselves around the fuser. This means I can not use one of the favorite transfer mediums used for the job, photographic paper. The thick paper stock gets stuck in the printer (though regular paper works fine). Fortunately for me I found another medium that seems to work as well without getting stuck.

    A quick word about how laser printers work. Basically they are a off shoot of copier technology, they use a powered plastic toner that is transfered to the paper by using a drum similar to copying machines that uses high voltage to make the powder stick to the paper using electrostatic fields. A copying machine uses a selenium drum that is photosensitive, and the static charge on the drum is affected by light. I don't know what the laser printer uses, but it is a very similar process, only using a laser instead of a scanning plate. After the plastic powder is transfered to the paper it is melted in a fuser, one or two hot rollers that melt the plastic into the paper. This is what makes toner transfer possible. If the toner melts into a porous substance such as paper it is permanent, but it is possible to use materials that it will stick not quite so securely.

    A really good resource for doing this technique can be found at Tom Gootee's site. Tom is also an active member here at AAC.

    First, you need to layout the PCB in a manner that can be printed onto the laser printer. For this exercise I used ExpressPCB. This package is given away by the manufacturer for the express purpose of allowing you to design a PCB, sent them the results, and they will make the PCB for a fairly economical price. It is also useful for doing it yourself, it is extremely easy to use. I will not go through the trials I went through learning this package in the last week, but if you are interested it was pretty much covered in this thread. A company that sells a professional package also gives away a crippled version, but with all the bells and whistles I have found it hard to use. This is Eagle by CadSoft. I'm probably going to have to learn it someday, but not today.

    OK, I made the layout. I didn't like the pads, so I cleaned them up by using M/S Paint, which can manipulate the image OK but has lousy printer drivers, and Gimp, which can handle high res images and print them out at 600 dots per inch (CPI). Eventually I'm going to have to really learn Gimp, but not today. It got me to this point, this schematic has been thoroughly gone through and polished, I redid all the pads to meet my personal preferences.

    [​IMG]


    Note that both images have been flipped to mirror them. You can see this in the text for the silk screen side. This is important. If you use Express PCB to make the PCB layout be sure to do this mirrored, it is a pain otherwise. This is why I am using Gimp to print it out, I got it wrong first time.

    This is now ready to print, now I have to prepare the transfer medium. Ron H, another member of this site, suggested something I have found very handy, wax paper. It may not be the best thing for the printer fuser, but my printer has shown no bad effects to date.
     
    Last edited: Aug 7, 2015
  2. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    So I tear off a sheet of wax paper, and attach it with tape on scratch paper so it will go through the printer. I am recycling a used sheet of paper, disregard the print on the paper.

    [​IMG]....[​IMG]

    [​IMG]....[​IMG]

    [​IMG]....[​IMG]

    The end result is two templates and a small pile of trash, the silk screen and the main PCB. I only tape near the top, and on the other side of the fold. The idea is to drag the wax paper through with the scratch paper.

    Next step was cutting the PCB to size. I used my Dremel. Since this is pretty mundane I didn't bother to take pictures. The PCB was deliberately cut oversize, so it can be mounted with whatever scheme later. It can be with standoffs, or using wood with slits cut into them with a router to slid the board into.
     
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  3. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    The next step is to clean the PCB. If it is fairly new stock it just needs a wipe with a good solvent such as alcohol or acetone, if it is corroded then you should use Scotch Brite pads. I used to use steel wool, but I've been told it can leave bits of steel wire embedded into the copper, where it can react chemically later. Scotch Brite doesn't have this problem. If you use a chemical clean be sure to let the chemical completely dry. The idea is the plastic toner must adhere to the copper on the board.

    Next fasten down the template to the PCB with scotch tape onto ½ sheet of scratch paper, being careful not to have the tape where it will not get involved in the process. When I was using an iron I had a problem with the iron being too low wattage. This meant that I had to hold it on the template with a piece of paper between the iron and the transfer to prevent moving the transfer and smearing the image. The process took around 10-15 minutes with no guarantee the transfer would work properly. I lucked into a high quality laminator that was on sale for dirt cheap, and that has made all the difference for me. I feed the scratch paper with the PCB and transfer through the laminator 8-10 times. This thoroughly melts the toner onto the copper. Using the ½ sheet means it spends ½ the time in the laminator as it would for a full sheet. Be sure the toner is facing the copper, since you are looking through the wax paper it will appear to be in its normal orientation, text will be readable.

    [​IMG]....[​IMG]

    This particular time it did not go well, as the PCB kept getting stuck in the laminator. I used the scissors shown to help push it through. This is not too good for the laminator. Later efforts I left a 3¼" between the edge of paper and the PCB stock to help pull the total setup through the laminator, it works much better and is less likely to damage the laminator.

    At this point the former wax paper (the wax will have completely evaporated) and the PCB are glued together with the toner. You should have the tupperware (or glass) container for what comes next. The container should have extremely hot water, I get it to boiling using the microwave. Immerse the PCB/paper into the hot water, and let it soak for 5-10 minutes. You will find the paper soaks in the water instantly. After waiting for the soak gently pull as much as the paper off as you can, but at this point it will be very soft and much of it will be left behind. Gently rub the paper with your fingers and/or use a soft toothbrush to tease the paper off. It does not matter if it is on the toner, but pay special attention between the traces.

    Another method, recommended by the original author of this method, is to use pure Isopropyl Alcohol (IPA). You can buy it at hardware stores and pharmacies 91% pure. Allow the paper on the PCB to soak for 3 minutes, then start removing the paper. It does come off easier, but the traces will be a bit more delicate. I tried a combination of the two, really hot water and added some IPA. It seemed to help.

    [​IMG]....[​IMG]

    [​IMG]....[​IMG]

    At this point do an inspection. Be critical, look for flaws. If there are any present do not etch the board, but wipe it clean with acetone and start over. If there very small flaws you can touch them up with a fine point sharpie, but it will only go so far fixing things. If you try to etch a flawed board likely all you will do is waste etchant and the printed board stock without doing what you intended
     
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    Last edited: Nov 12, 2011
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  4. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    If the PCB passes muster it is ready for etching. There are many choices of chemicals, each with its own set of problems. Ferric Chloride is safe to handle, but it stains everything it touches, including skin. It eats metal, so be careful using and storing it around tools, even the fumes from a closed bottle will etch and rust tools. My solution, after seeing what it had done to a tool box, was to wrap a paper towel tightly around the lid and tape it place. Next time I went for my etchant the paper towel around the lid was brittle, but my new tools were OK. I do the same thing with my acid bottles.

    Lately I'm using a different etchant, a 2:1 mix of hydrogen peroxide (H2O2) and muriatic acid. Muriatic acid is a common swimming pool chemical, and hydrogen peroxide can be found at any grocery store. Muriatic acid is a very strong version of hydrochloric acid! Gloves and safety glasses should be worn when handling it! Acid will cause chemical burns, treat it like the dangerous substance it is. I also recommend an apron, but it is your cloths at risk. Oddly enough, it is probably much more environmentally friendly to dispose of, since all animals have hydrochloric acid as part of their digestive system. Remember though, these chemicals are designed to dissolve copper, which describes most modern plumbing. Do not pour it down the drain, even in small quantities.

    The tupperware container should be marked before you pour the etchant in. I poured 1½ cups of water, marked the side with a sharpie, then another ¾ cup of water, and again marking the level. Put your personal protection gear on, the gloves, safety glasses, and apron. I would have paper towels already ripped off the dispenser and waiting just in case. Pour the hydrogen peroxide to the first mark (2 parts), then carefully pour the acid in to the second line (one part).

    Couple of safety tips. Don't even think of doing this without gloves that are intact and have no holes. Ditto for the safety glasses. You can replace almost anything except your eyesight, and loosing flesh to acid burns is very unpleasant. Always, ALWAYS, pour acid into water (or the H2O2 in this case)! Try this the other way and the acid could splatter everywhere, causing a real mess and presenting a real safety hazard! As it is it will heat up the liquid (a good thing) and smoke (a bad thing). Don't breath the fumes, they are unhealthy to say the least. You should do this process where there is plenty of ventilation. One last detail, I saved an old polypropylene rubbing alcohol bottle to put a small, manageable quantity of acid in. Be sure to label this bottle as filled with Muriatic Acid or Hydrochloric Acid correctly on both sides! Using a small bottle to dispense the acid will dramatically reduce the odds of an accident with large quantities of acid, but failure to do something simple as labeling a bottle could hurt or kill someone.

    [​IMG]....[​IMG]


    The peroxide/acid etch has a major advantage over Ferric Chloride, it is transparent. Gently wipe the board while it is immersed with a small sponge or paper towel, as this will dramatically speed the etching. The etchant will slowly turn green as you proceed, and should be done in under 5 minutes. As the copper slowly gives way to the board material underneath concentrate on the portions of the board where the copper is still etching away.

    [​IMG]....[​IMG]

    When the board is completely etched drop it into a bowl of water to rinse the acid off. You need to stop the chemical reaction as fast as possible. I used a large glass or water to rinse everything off outside, and don't flush any of the etchant down the drain. I threw the piece of sponge away.

    Use a paper towel wetted with acetone to wipe the toner off. At this point you have a printed circuit board. In general acetone dissolves toner, while alcohol softens it. This means you can clean the flux off the PCB later after you have soldered all the components on without damaging the silkscreen side too much.
    Acetone will remove any toner it touches.

    [​IMG]....[​IMG]

    This board turned out pretty good. No voids, nor shorts, when viewed closely. I used the high resolution image these photos were based from to do a fine inspection, while not perfect it turned out very well.
     
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  5. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    Now the new PCB needs drilled. I have a old Dremel drill press mount and old Dremel that work very well for this. I have even bought a set of drill bits very economically priced from Dan's Small Parts and Kits way back when. Since my eyes are not the best I use a magnifier in lieu of safety glasses (probably should have done that during etching).

    Drill all the holes out, making sure all the components will fit as you do a component layout. I left little holes in the pads that will work as center punches. It is very easy to miss a hole at this point, so double check your efforts after your finished.

    After you have all the holes drilled (and doublechecked) you are ready to put the silk screen side on. Basically repeat the procedure you used to put the toner on for the silk screen,including the hot water bath. The reason you drilled the PCB before applying the silk screen is the holes will give you the reference points you need to line it up.

    [​IMG]....[​IMG]

    [​IMG]....[​IMG]

    One of the problems using paper with toner is some of paper will remain fused to the toner. On the PCB side this doesn't matter much, since the toner will be removed anyhow. The toner isn't fused to the board that tightly, it can be easily scratched off with a fingernail. However, it does provide critical information as to where the parts are supposed to go. The last board is the final product, this is a finished board.

    The IPA alcohol does do a cleaner job of removing the paper, with a slightly higher risk of removing the toner. I'll keep both options open, as both seem to work.

    This PCB is now ready to be soldered.

    .
     
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  6. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Please don't forget to mention http://www.diptrace.com which is free up to a certain amount of pads and you get even more if you only use it for non profit or educational purposes. 500 and two layers will handle most anything anyone does on here.

    I liked it so much I upgraded to an increased capacity licensed version, upgraded again then went to the full version not long after I hit a board design that ended up being about 8" x 12" due to the sheer number of components on it. Remember though that I'm an old school designer that still relies on basic through hole logic ICs but the program, even the free version, will handle all the SMD you can throw at it.

    For free you can't go wrong trying it out, the libraries are somewhat limited but grow every day. As with any software there's a learning curve but they've got a forum up now where people can exchange tips and stuff although it's almost so easy you can learn it yourself as I did. I have never got a bad board out of it that wasn't due to stupidity on my own part. My main PCB manufacturer has no problem with the Gerber and NC drill files it can output when you're finally happy with something or it will send perfectly dimensioned prints to a laser which is important to me, as little as a 0.001" variation can make a toner transfer board a pain especially if you're doing SMD.

    [EDIT:] It sure was a blessing getting away from the ORCAD I was forced to use in the early days, talk about a pain.
    Also, looking at Eagle's website you get one heck of a lot more with DIPTrace than you do from them and it's FREE folks.
     
    Last edited: Dec 29, 2010
  7. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    No need, you just did. :D

    Thing I liked about Express is you can program custom components, and it allows you to put your favorites in a separate folder. This seems to be a major weakness with Eagle from what little I can tell. I also don't like Eagle's reliance on making you identify specific parts. I still haven't found a ¼W resistor for Crimmy's sake!
     
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  8. nigelwright7557

    Senior Member

    May 10, 2008
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    I have had bad experiences from free and cheapo pcb cad packages.
    Some of the error checking is very poor and i have had to throw out 2 lots of pcbs coz there were errors on them not caught by the software.
     
  9. Wendy

    Thread Starter Moderator

    Mar 24, 2008
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    While I sympathize, it is the users responsibility to verify the prints. I've made a lot of simple boards, this is the first I've used a CAD package with. There is a chance I've mucked this board up, but I've looked it over pretty carefully.

    Rockwell Int., later Alcatel, was not immune from basic problems either. In our CRG dept (Customer Returned Goods) we routinely revised PCBs with thin wires, and extra parts, if needed. You are not alone with your problems.

    One nice thing about DIY boards. While they aren't as good as professionally made boards, they are much cheaper. This is perfect for prototyping.

    We had a thread from some guys who didn't even build a prototype, and made 500 or more boards. It is hard to have sympathy for this kind of screw up.

    Haven't I seen you on ElectroTech?
     
    Last edited: Dec 31, 2010
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  10. marshallf3

    Well-Known Member

    Jul 26, 2010
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    I hate having to make my own components up in any program but it isn't hard in DIPTrace, the hardest thing is figuring out how to save them into your own custom library or add them to an existing one.

    1/4W resistors are simply RES400 as 0.4" is the proper lead spacing for them, they were already in there.
     
    Last edited: Dec 29, 2010
  11. marshallf3

    Well-Known Member

    Jul 26, 2010
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    What I use is very thorough in checking, I even tighten up the specs on trace spacing until I start getting a lot of errors, back off a little then adjust the few remaining traces that it doesn't like.

    You can then run your design through something like https://www.freedfm.com/!freedfmstep1.asp which will also do a professional job checking things out for free.
     
  12. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Maybe you should mention which side up on the wax paper?
     
  13. Wendy

    Thread Starter Moderator

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    Wax paper is symmetrical, there are no sides without wax. Lay wrong side up and you will know.
     
  14. spinnaker

    AAC Fanatic!

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    I never looked at it that closely. I always thought only one side was waxed. Plus I thought I saw a discussion somewhere on picking the proper side of the paper.
     
  15. Wendy

    Thread Starter Moderator

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    Trust me, after you put the transfer on, there is only one good side of the paper. Get it wrong and your iron (or what ever you are using to heat it) will end up with toner all over it. The interesting thing is, after heating the transfer there will be no wax left.
     
  16. spinnaker

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    No I am talking about what side up when printing. Is there a difference?

    I think it should be fairly obvious when applying the transfer to the PCB. :)
     
  17. Wendy

    Thread Starter Moderator

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    Depends how you attached the wax paper to the scratch paper. Since laser printers are different, your going to have to experiment and find out how your printer works. On mine the print side has to be up. I also configure the printer for a straight through shot, to help prevent jams.
     
  18. marshallf3

    Well-Known Member

    Jul 26, 2010
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    This I've got to try, may give it a shot tomorrow to see if the old Lexmark in my work area will print as well as your HP. My cheap Samsung is low on toner again and I don't feel like taking the cartridge apart and refilling it, much less the fact it's not on the network and the Lexmark is. The Samsung is just a local printer for when I put my true desktop PC back in here so I don't have to go to another room to get print output and I don't feel like running a cable from point A to point B for the Samsung.
     
  19. spinnaker

    AAC Fanatic!

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    Yes I know and an easy way to figure it out is place a mark on the top side of the paper as you put it in the printer, print something and it will be obvious which is the print side.


    But I was wondering on which zide of the wax paper to print. Believe it or not, I currently have no wax paper in the house so I can't check. But I thought one side was waxed and the other side no wax? If so, I assume you print on the no wax side?
     
  20. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    If it IS waxed on just one side, it will be the protected side which comes off facing in(toward the center of the roll). Not the outside, which is the exposed side. Just pay attention to the roll as you pull the sheet out and do it that way just to be sure.
     
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