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Homemade PCBs

trasparentIn this article Bernard Klinc shows us his homemade PCB process. He gives step by step instructions with plenty of pictures. Bernard will receive a giveaway item of his choice from the hobby parts for articles project here at uCHobby.

We all know the fancy companies that make PCBs. The do make great quality boards but they will pretty much suck your wallet dry. Mostly they have a minimum order of 10 boards, even a single board may be expensive and it might take over a week for you to get the board. So they are a especially bad idea if you only want 1 board and you need it fast. So how to get around this problem? Well make your PCBs right at home of course!

First of all we need a few basic materials:

  • Copper boards
  • Photoresist
  • UV lamp
  • Transparent foils
  • Inkjet or laser printer
  • Developer
  • Acid
  • Acetone

Now you may be worried how much this all is going to cost. Well the copper boards can be found at A4 sheet sizes for 4 or 5 € (It will take you forever to use up such a big board) Also you can buy boards that already have the photoresist applied to them, if not you can buy photoresist on a spray can and spray it on. That photoresist spray will set you back about 5 to 10 Euro and will last very long. The acid I use is ferric III chloride. You get about 1kg of the dry stuff for 6 € (It becomes acid when mixed with water and 1kg will make a LOT of acid). And the developer is dirt cheap 1.80€ got me 250 grams of NaOH, this will give you about 2 or 3 liters or developer when mixed with water (NaOH is very strong so it needs to be mixed with a lot of water). You probably already have Acetone at home, the most popular use for it is nail polish remover and you can buy it in any drug or hardware store. As for the transparent foils you can get that at any better office supply shop

Now the UV lamp is the tough part. Most photoresist reacts on UV-A and UV-B light. The typical UV lamp or so called black light used in a night club or something will have a filter that takes out the
UV-A and UV-B part of it, this is because that part of UV is dangerous. Without the filter people sitting under that UV light would get sun burn on the skin and eye damage if looking at the light for longer periods. UV-A light is so bad it even kills microorganisms. But I found a local electronics store sell these special unfiltered bulbs as replacement bulbs for the UV exposure boxes that they sell (too bad the exposure boxes cost like 300 to over 1000€) But the UV bulbs cost only 10 to 20€. I brought me one of those and mounted it in to the case of an old broken printer (BTW ripping apart a printer is the best for getting quite strong motors). Used a florescent light ballast to light up the UV bulb.

The process:

1) Create your PCB design using one of the many PCB design programs on the web. Personally I use Cadsoft Eagle, but you can use any program you want even MS Paint (No please no, don’t do a PCB with that)

eagle

 

2) Print your design on a transparent sheet. Set your printer to a high quality setting so it applies a thick coat of ink, that will make sure no UV light can get trough.

trasparent

 

3) Apply and dry the photoresist on the board or if you have boards that already are coated then pull the protective foil off. Put your transparent sheet on top of the board and put a plane of plexy or glass on top of it all so it holds it still. Now just close your UV box and plug in the UV light. Leave it in there for about 3 to 15 minutes (Depends a lot on the photoresist you use and how powerful your lamp is, for me 10 minutes seems to work the best ) With the photoresist I use “Positive 20” the UV light makes the board turn blue but the tracks are green. Some photoresist coatings are transparent so you can’t see this.

board_after_UVuvbox

 

4) Developing the board is done in a water solution of NaOH. Basically the UV light made the photoresist weaker. So now the developer eats off the photoresist that got under UV. The developing is done when the copper is clearly visible agent. Like in the photo.

develop

 

5) Now we wash the board and throw it in to the ferric chloride that we dissolved in water. This will take about 30 minutes at room temperature. Can be shortened down to 15 minutes if you agitate it. And down to 5 minutes if you heat it up to about 40 to 50°C

acid

 

6) Now the board still has the photoresist on it making it look ugly and it’s not solderable, so we need to clean it off with acetone or a similar solvent. It comes of very easily (The clean part in the photo was done with a single gentle wipe). After cleaning the board is nicely shiny.

cleaning

 

7) Now comes drilling. For this I use a 12V mini drill. It spins at 20 000 rpm so it’s great for PCBs. You can get tiny drill bits for PCBs at electronics stores the bit currently in there is only 0,8mm.

 drilling

 

8) I can’t make a real silk screen but I can make something like the silkscreen. It’s simply printing out the component layer in eagle on a sheet of high q
uality paper and gluing it to the top of the board. Not only does the board look better it also helps you place components in the right spots

 silkscreen

9) Finally solder the components on to the board and its done. (In case you didn’t figure it out by now this is a stereo audio amplifier)0

 finished

 

Conclusion:

The PCB manufacture using this photo method may be a bit complicated but it creates incredibly precise results. It is possible to etch with the same precision your printer can print. Also it doesn’t cost a lot, you can easily get everything you need to make PCBs for under 50€. You won’t regret getting in to PCB making.

Posted in Development Tools, Discovering, Projects, Workshop Tips, Workshop Tools.

20 Responses

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  1. Eric said

    Nice tutorial!

    Some more cost cutting measures: Use Pool acid, (myriatic acid) available from any hardware store, instead of ferric chloride. It’s a lot more environmentally sound, cheaper, and easier to dispose of (you can neutralize it with heavy such as baking soda)

    With those money savings, you can go buy a small aquarium pump to agitate the liquid while you etch. It will drastically reduce the amount of time spent etching!

    Something I always do as a check step, which is not necessary in some peoples eyes, is use a neutral water rinse in between steps to not cross contaminate the chemicals in the various dips. I’m no chemistry genius by any means, but I’ve burned off nose hairs way too many times!

    Again, thanks for doing this tutorial. I always fall back on etching something when I only need one of them, and I need it quickly!

  2. Daniel said

    Can you just place the pcb under a uv light bulb? for the same affect.

  3. Great tutorial.

    From the picture with the circuit designed in Eagle i thought you are gonna show us how to make some plated vias, because i haven’t succeeded so far with doing them.

  4. Berni said

    Well for me ferric chloride is cheap enough and they say its the best for etching at home.

    The PCB has to have a coat of photoresist, UV light wont do a thing to copper.

    Well the eagle screenshot is just for a example project that comes with it. Well you can get chemicals that you simply dip the board in to and it will tin it. Other method is electroplating. I don’t tin them or even do double sided boards (tho dublesided is completely possible with this method)

  5. Joseph Yumul said

    just like to clear that ferric chloride is not an acid it’s a base :P

  6. I must be stupid, but something doesn’t make sense to me. You start with a copper plate, apply photoresist, and expose it using UV. Then the developer eats away the portions of photoresist that were exposed to UV. So doesn’t that leave you with a board that’s bare copper in the exposed areas? Basically the reverse of what you want? In fact that’s what the photos for steps 5 and 6 seem to show: nearly the whole board is exposed copper. But then in step 7 the board is lime green. What happened? What is the actual chemistry going on in steps 5-7?

  7. Joseph Yumul said

    @steve
    please read step 3 the transparency serves as the UV protection for the portion of the board to be protected with the ferric chloride then you develop it in the photoresist developer solution then you can see the result in the image in step number 5 you can see the tracks there ten you etch it int the ferric chloride you can see in step 6

  8. M said

    Your UV light is inside a printer … case?

  9. Berni said

    The pictures are a bit messed between steps(David need to fix that)

    Anyway the photoresist is weakened by UV that was not blocked by the transparent sheet. The developer eats off the UV exposed photoresist and so exposing the copper. The chloride can only eat exposed copper so it gets eaten off and so creating the PCB.

  10. GeneralFault said

    Florin,
    I have done some plated vias using conductive ink. I use 1/64″ board (the thin board makes it easier to get the ink all of the way through). After etching and drilling the board, place it on a piece of paper towel. Using a conductive ink pen, dab the ink onto the holes. The paper towel will help to pull the ink through the board. Once the ink dries, use a piece of paper towel whetted with acetone to wipe off the extra ink. Be careful not to create too large of a “pit” over the via.

  11. I think the part I was missing is that you start with a board that’s copper-plated, and that has some non-conductive material underneath, and then you eat away the copper you don’t want. Is that right? Initially I thought it was just a solid copper sheet, copper all the way through, and you covered up the areas that you didn’t want to be conductive.

  12. Berni said

    You can do it without a drill press if you use a small drill and hold it right. Use bouth hands to hold it at 90 degrees and your fine.Remember to have clamp down smaller boards it will start spining around the drill bit and break it otherwise.A crocodile clip works fine for that.

  13. Has anyone found a good source for photoresist in the USA?

  14. dfowler said

    OK I fixed the articles pictures. Sorry for the confusion.

  15. Something this particular guide seems to be skimping on is that that ferric chloride is vicious stuff. Especially with the copper dissolved in it. If this article really is new information to someone, they should really be warned about what they’re dealing with.

    As for an earlier comment, I believe it’s a salt and the solution is obviously acidic. The reaction to copper isn’t entirely due to that but you can do the etching with other suitable acids (plus peroxide IIRC).

    Do not allow it in drains or nature, it should be handled as hazardous waste and given to the waste disposal authorities just like batteries, old oils, paints etc.

    It also stains everything really badly :)

    http://en.wikipedia.org/wiki/Iron(III)_chloride

    Google for more. There’s tons of resources on pcb making and etching with lots of tricks and variations.

  16. Oh, and no metal containers obviously :-D

  17. Markham said

    I have a dead scanner that I plan to convert into a UV exposure chamber. Would the glass end up blocking the UV light? Or am I thinking of infrared?

  18. dfowler said

    Markham,

    I think you will be OK with the scanner glass but you might read more at the links below. You may have some blockage but you can adjust your exposure time to compensate. I vaguely remember that Plexiglas is not so good at passing UV but I could be wrong. The PCB exposure rigs I have used in the past did have glass.

    Plastic (Plexiglas) Transmission
    http://www.newton.dep.anl.gov/askasci/eng99/eng99272.htm

    Glass Transmission
    http://www.newton.dep.anl.gov/askasci/phy00/phy00890.htm

  19. Alan Wang said

    Iron (III) Chloride is indeed acidic when dissolved in water. It should be noted that it is very corrosive (be careful in other words)

  20. Berni said

    Well its kinda logical to be careful with something that eats metal. And yeah donut use a screwdriver or something to get the board out of the acid, because it will start to rust like crazy.(I seen a screwdriver that had this happened to it)