Etch a Circuit Board With Kitchen Supplies

51,174

430

45

About: I like banjos, and whiskey in a jar. My favorite meal is brunch. In my free time, I make things, break things (usually trying to fix them), and play with electronics. In my day job, I'm a science journalist.

As you tinker with electronics projects, you'll quickly realize that the more complex they are, the more difficult they are to solder together. It usually means creating a rat's nest of individual wires, which can be bulky and hard to troubleshoot. Time to try making your own circuit boards at home! They're a great way to test new circuit designs, and make assembling your project a lot simpler later on—just add parts.

There's a catch, though: most of the existing kits out there use really nasty chemicals like ferric chloride or hydrochloric acid to etch the copper... so In this instructable, I'll show you a way to do it with stuff in your kitchen. Call it high-tech-low-tech circuit making, if you will..

You'll need:

  • 1 copy of Autodesk Eagle (or another board design software)
  • 1 package copper clad board (single-sided blank PCB)
  • 1 package sticker paper (important: sure backing comes off in ONE BIG PIECE - no premade cuts)
  • 1 clothes iron
  • 1 office laser printer
  • 1 bottle Acetone or nail polish
  • 1 bottle of white vinegar
  • 1 bottle hydrogen peroxide
  • 1 box cooking salt (finely ground is best)
  • 1 box Aluminum foil
  • Gloves and eye protection

Step 1: Prepare Your PCB Design

Once you've tested your circuit on a breadboard, you can start to lay out your components in software. There are lots of ways to do it - I used Autodesk Eagle, which is free, but very powerful. I won't explain how to use it here—that's way outside the scope of one Instructable. If you want to learn, though, Sparkfun.com has some really great tutorials.

No matter what software you choose, you'll need to save or export the design as a PNG file in order to etch at home. (If you used Eagle, I wrote a quick how-to below).

When you're done, use image editing software like Gimp (or even iPhoto) to flip it and make a MIRROR IMAGE. If you don't, your final PCB will come out backwards.

Getting a board image out of Eagle:

  • Click on the "layer settings" button. (looks like three multicolor squares).
  • Make sure that ONLY the traces and pads on bottom of the board are displayed. This is the stuff that you want to physically see etched on your board. Usually this will be layer 16 ("Bottom"), 17 ("Pads"), 18 ("Vias"), and 20 ("Dimension)".
  • Under the "file" menu, select "export", then "image".
  • Set resolution to 1200 dpi, and BE SURE to select "monochrome."
  • Give the file a name and save it.

Step 2: Prepare the Transfer Paper

Time to transfer your design to the copper PCB. To do this. you'll need to print it onto the sticker backing paper.

Why? By laser printing the design onto this non-stick paper, we'll be able to easily iron the toner onto the blank copper. Once it's stuck on, it forms a really nice mask—whatever copper is left exposed will be etched away; whatever is covered by printer toner will remain solid metal, forming your circuit.

First, prep the paper. Peel off all the stickers, and wipe the waxy side of the backing with some acetone. Be sure to let it dry. This will remove any oils from your fingers (or the stickers) and give you much more uniform results when you try print onto it.

Step 3: Print Your Transfer

Once the paper is ready, slide it into the "single sheet" tray of your laser printer (usually the one that folds down to accept things like envelopes). Make sure you're printing on the shiny, waxy side!!

If all goes well, you should have a print like the one shown above. If not, no worries - just wipe it off with acetone and try it again! You can usually get 2-3 uses out of a sheet before it starts getting too fragile to use.

Step 4: Transfer Design to PCB

Got a good print? Awesome. Now prep your blank copper board for the transfer.

  • Wipe it with acetone and let it dry. DO NOT touch the surface again before the next step! Oil from your fingers will prevent the design from sticking to the copper.
  • Attach the blank copper board face-up on a piece of cardboard or scrap wood. Some double-sided tape is helpful to keep it from moving.
  • Lay your newly-printed PCB design over the copper board. You can tape the edges in place to keep the sheet from sliding around.
  • Set an iron to high (Linen setting), and press down on the sticker paper covering the copper plate. Hold the iron in place, covering the whole board. NOTE: if your edges are coming out jagged or look runny, it means the toner is melting too much. Try putting the iron on a lower setting and just pressing for longer.
  • Press hard for 60 seconds, then slowly move the iron while pressing for 3-4 minutes. I found it helpful to press gently on detailed areas with the tip of the iron to make sure they fully transfer.
  • Remove heat and wait for board to cool a few minutes. While still warm (but not hot), gently peel off the transfer paper. If you did it right, your design will be stuck to the copper!
  • Use a sharpie or nail polish to fill in any areas that didn't fully transfer, or came out faintly. If any traces are too close together, you can also scrape away some of the toner with an X-acto blade or needle.

Step 5: Etch Your Board!

The moment of truth. Put on your gloves and eye protection, and get ready to etch! Before you do though, a word of caution:

DO NOT, I repeat, DO NOT pour any acetone into the etching solution. Acetone and hydrogen peroxide can react to cause a highly flammable and possibly explosive chemical.Given the low concentrations of hydrogen peroxide we're using (3% solution), that's unlikely, you're still better safe than sorry. Now on with the show!

  • Mix together a 1:1 ratio of vinegar and peroxide in a small tupperware container. I found it helpful to heat it in the microwave to speed up the chemical reaction.
  • Add as much salt as the solution will hold.
  • Lay the PCB with your newly-transferred design in the bin. You should hear a fizzing sound as the reaction starts to work.

  • Occasionally stir the mixture, and add more salt and peroxide as needed. Some crud will form on the surface of the copper board as it dissolves - you can speed the process by wiping it off gently with a sponge or brush.

  • After about an hour or so, your board should be done! Be sure to RINSE THE BOARD WITH WATER, then wipe the remaining toner off with acetone and let it dry.

  • Next, drill holes in the component pads with tiny bits like these (a drill press or a steady hand helps - they break really easily).

You're almost ready to start soldering! The last thing to do (and this is important), is safely clean up your mess.

Step 6: Safely Dispose of the Etchant

When you're done etching, the liquid will look blue-green. That's because the process created copper (II) acetate, which is poisonous. It's not awesome to flush it down the drain, so we're going to neutralize it.

  • Cut up about a square foot of aluminum foil into small pieces. Stir the pieces into the blue-green etch liquid, and leave outside for a few hours.
  • The liquid will turn purple, and you'll see little brown specks settling to the bottom. Congrats: you just turned that copper chloride into harmless aluminum salts and elemental copper (the brown specks).
  • Now you can dispose of it safely in your drain.


Final notes: Don't be discouraged if your board doesn't come out right the first time. It took a bit of trial and error to get mine the way I wanted them - but it's way faster and more satisfying than ordering boards from overseas!

Also: I am NOT a chemist - if you are, please weigh in on the disposal methods! For more info on this etching technique (and on disposal), there's a great discussion at Blondihacks.com. Happy building!

******

UPDATE: a few folks pointed out in the comments that my chemistry might be slightly off - with enough salt in the mix, the solution could turn green, meaning it's copper (II) chloride—the same stuff in some root killers. In that case, adding aluminum foil would just make another poisonous chemical, aluminum (II) chloride, and shouldn't be put down the drain. See discussion on stackexchange for more details.

if there's any doubt on whether or not it's safe to flush the liquid, though, you can always mix it with plaster of paris, wait for it to harden, and throw the whole thing away.

Electronics Tips & Tricks Challenge

Runner Up in the
Electronics Tips & Tricks Challenge

Share

    Recommendations

    • Paper Contest

      Paper Contest
    • Warm and Fuzzy Contest

      Warm and Fuzzy Contest
    • Organization Contest

      Organization Contest

    45 Discussions

    6
    None
    ShannonW49

    Tip 3 months ago

    I've done this for several years. Here's a couple of tips:
    -- I use thin glossy magazine paper for the transfer. Works well, and is cheaper and easier to find. It may take a try or two to get the subtle differences down, but works pretty much the same way.
    -- I use 2:1 hydrogen peroxide to 9% white vinegar. I add the board, then sprinkle the salt in. It will immediately start fizzing. When the fizzing slows, I add more salt. The salt adds ions to allow a better reaction (etching). I also add an aquarium bubbler to the mix (put hose in so it bubbles in the solution) to keep it moving around. This keeps the solution mixed (no "dead spots" of used reactant directly above the board) and keeps the gunk from building up on the board itself (to be scraped off).
    -- I have started using HCl instead of vinegar. This is hydrochloric acid, and is also know as muriatic acid. Muriatic acid is a common product available at home improvement stores for swimming pool maintenance. Comes in a big box or a gallon jug for a few dollars, and is more than you will ever need.
    ----- 2 parts H2O2, 1 part HCl - Using this has some advantages. It etches faster and can be "renewed" (you don't have to throw it away). By bubbling air through it, you cause some other reactions to happen the converts the used-up solution to drop its copper and become useful again. Just store it (safely) and you got it ready for next time. (any chemist want to explain it?).
    ----- First time you use this, it will be very fast, so be careful (fast and mean, might want to just dissolve some copper into it instead of etching a board right off). As the copper dissolves into it, it becomes cupric chloride (and turns green). This is what will do the etching later instead of the raw HCl, and it will slow down a bit. The cupric chloride is really what you want, you want it green. That is what is "renewable". You can bump the acid levels back up by adding oxygen (bubble air through the mixture).

    1 reply
    2
    None
    wv99999

    3 months ago

    Whoever developed this etching procedure really knew his chemistry! After all, a reaction of the type Cu+2HAc=CuAc2+H2 cannot take place because copper is more noble than hydrogen (HAc I use here as a general short form for any non-oxidizing acid, whether this is hydrochloric or acetic (=vinegar) acid .
    In order to make it possible to dissolve Cu with HAc, the reaction needs to be changed to
    Cu+HAc+O=CuAc2+H2O
    This is done by adding an oxidiser. This can be H2O2 (commonly used for bleaching hair). This works because, in the presence of heavy metals such as copper or iron ions, H2O2 becomes unstable and decays into H2O (water) and O, activated oxygen, which I use here without reference to the intermediate steps. An alternative would be to use household bleach (Hypochlorite), which is just another oxidiser, or potassium permanganate, which is used in some countries as a fungicide and thus available from gardening shops / nurseries.
    But even then, the reaction would not proceed because the reaction Cu+HAc+O=CuAc2+H2O ignores the formation of compounds with very limited solubility in water (the so-called gunk), which simply isolate the copper metal from the acid. To improve that solubility, sodium chloride (common salt) is added.
    And this is where the color of the final solution comes into play, as well as good stirring. Up to now, In order to understand what happens we could afford to just take a global look and ignore the details. As soon as solubility matters, we need to look at the reaction step by step. First we need to understand valence. Since not all of you will have university level training in chemistry, I will keep it as simple as possible, i.e. you need not read and understand the Wikipedia article on it. It suffices here that aluminum has valence 3 and copper either valence 1 or 2. Valence is always expressed by writing the number in ROMAN numerals, with the numerals enclosed in round brackets, i.e. as aluminum(III), copper(I), or copper(II). Other valences we need not consider. Thus, the reference to aluminum(II) above by videoschmideo is a typo.
    Another number to understand is oxidation state. Oxidation is the removal of electrons from a chemical element, and oxidation state thus tells us how many electrons have been removed. Thus Cu+ corresponds to oxidation state +1 and valence copper(I), Cu2+ to oxidation state +2 and valence copper(II), and Al3+ to oxidation state +3 and valence aluminum(III). Unlike valence, oxidation states can also be negative numbers: -2 for oxygen in H2O and -1 for oxygen in H2O2.
    Splitting the bulk Cu+HAc+O=CuAc2+H2O into its components, we obtain
    Cu=Cu++e- (copper is oxidised from oxidation state 0 to oxidation state 1)
    Cu+=Cu2++e- (copper is oxidised from oxidation state 1 to oxidation state 2)
    H2O2+2e- = 2OH- (oxygen is reduced from oxidation state -1 to oxidation state -2)
    2HAc+2OH- = 2Ac- +H2O (the OH- ions are neutralised)
    If this were all, no salt needed to be added.
    Unfortunately, basic copper acetate Cu(OH)Ac, commonly known as verdigris (green), is poorly soluble in water, and thus forms a layer between the copper metal and the acid that effectively stops reaction progress. Similarly, copper(I)chloride CuCl (white) is poorly soluble in water, and effectively stops reaction progress. And CuCl must be formed before CuCl2 can be formed.
    Thus, another step is needed.
    We need another reaction partner, and before we can introduce it, we need to understand color.
    Color is the response of an electric charge upon stimulation by light, or, more accurately, how much energy must be contained in a single photon to be able to break an electron out of its place. This leads to selective absorption of some of the frequencies contained in white light and thus to color. How strongly the electron is bonded to copper depends to a substantial degree to the other molecules / ions that are close by. If there are a lot of NH4- ions close by, as in Cu(NH4)4Cl2, the copper(II) ion appears dark blue or purple, with water forming the bulk of its neighbors, the copper(II) ion appears just blue, and the more Cl- ions are present, it becomes increasingly green through the formation of CuCl43- ions. Anhydrous CuSO4 is colorless, but the hydrated CuSO4.2H2O is colorless / white.
    And that is what the addition of salt does: it adds chloride and thus promotes the formation of Na3CuCl4, which readily dissolves in water. And before any of you start a flame war, my source only states that solubility is drastically improved by the addition of chloride, it does not state whether there are four or six chlorine ligands, i.e. whether the ligands are arranged in a square around the copper atom, or whether they form an octahedron. These are the two configurations that Ligand Field Theory permits.

    0
    None
    mickeypop

    3 months ago

    you note to mirror the image before transfer.
    ONLY mirror the "Top layer" or the bottom layer will be backwards

    4 replies
    0
    None
    videoschmideomickeypop

    Reply 3 months ago

    That's why I stick with one sided boards on this technique - mirroring different sides and getting them all lined up makes my head hurt...

    1
    None
    mickeypopvideoschmideo

    Reply 3 months ago

    It's really not hard, all you need is cut the transfers larger than the board, around 1 inch.
    Make one a bit smaller than the other.
    Align with a light box and tape them into an envelope.

    When you slide the board into the envelope they will be aligned.
    .

    0
    None
    videoschmideomickeypop

    Reply 3 months ago

    Hadn't thought of the envelope trick! Nice idea - will have to give that a shot.

    0
    None
    mickeypopvideoschmideo

    Reply 3 months ago

    ADDENDUM
    on a least one of the printouts add the outline.
    That way when inserting the board into the envelope you know you will not miss the edge.

    0
    None
    AF6YSAJBastos

    Answer 3 months ago

    It's called a "resist" process. The toner resists the acid etch.
    Inkjet ink is transparent.

    0
    None
    AJBastosAF6YS

    Reply 3 months ago

    I would like to thank you for your valuable explanations. Thank you all!

    1
    None
    Claudio AndreHAJBastos

    Answer 3 months ago

    That is because a laser printer works by depositing fine black plastic powder (the toner) onto the paper, and that gets transferred to the board by heat and pressure. With an inkjet you just have ink, and nothing with enough substance to partially melt and transfer into the board.

    0
    None
    VincentJ2AJBastos

    Answer 3 months ago

    Ink jet printers suspend colored ink in water, heat it up to steam and spray it on to paper where it soaks in and makes a nice picture.

    Lasers use something called toner. It is a very very very fine pigmented dust coated in plastic polymer. The printer creates a magnetic surface on the paper that the toner sticks to, then rolls it through a heated drum which melts the polymer to the paper.

    It's the melting of the polymer that transfers to the copper when you iron it. Trying to do this with an ink jet will just make a mess. The printing methods are completely different.

    0
    None
    morsed2AJBastos

    Answer 3 months ago

    Basically ink is not the same as toner.
    Simplified
    Ink-jet printers use ink, and laser printers use toner.

    Ink is a liquid, with some color added, when the ink drys it leaves a residue. Ink is a liquid, wet substance.

    Toner on the other hand is made of little (I mean very little, as in tiny) plastic balls with a black pigment added. It is these plastic balls that when melted by the iron, and stick to the copper to form the traces. Toner is a solid, dry substance.

    I hope that makes sense.
    But I just had a thought, what if you used an ink-jet printer that can print on CD's or DVD's. Would that work?

    0
    None
    videoschmideomorsed2

    Reply 3 months ago

    That's what I had thought about the toner vs inkjet, but stew1950 mentioned in the comments that he's had good luck with printing inkjet on photo paper for the transfer. Worth a try! You can technically make an etch mask with just a sharpie, so I don't see any reason why indelible ink won't work. You probably won't get lines as sharp as you would with toner, which physically fuses to the board, but it's still feasible.

    0
    None
    KrisF23

    3 months ago

    Wow, I'm an artist and this process works perfectly for me. Thanks you so much. Much less expensive than the process I was using.

    1 reply
    0
    None
    videoschmideoKrisF23

    Reply 3 months ago

    That's awesome - so glad this will work for you!

    1
    None
    treyjazz

    3 months ago

    I highly recommend printing the images out on regular paper first to make sure the scale is correct. I have made many boards and have had many times where scaling occurred - sometimes caught before etching and sometimes afterwards. Don't waste time and materials! Adding a border to the images in double sided boards will help a lot in alignment. Printing should be done on the darkest setting possible to get a good layer of plastic on the board and avoid broken traces. Also, if you can get ahold of a laminator (I use a modded AL13P) it is much easier to transfer a complete image with even heat and pressure.

    1 reply
    0
    None
    videoschmideotreyjazz

    Reply 3 months ago

    These are great ideas. DEFINITELY print the circuit out on regular paper first! That'll save a lot of headaches. The border sounds really helpful, too. I originally tried to do double-sided boards with this technique, but it was just too hard to get the alignment right... with a laminator, though, it might be possible to sandwich the PCB between two printouts at the same time (one for the top side, one for the bottom) - to make sure they stay aligned? If you try it, would love to hear how it turns out.