Etch a pcb

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Materials:

  • A sheet of printable transparent film 
  • 2 plastic or glass containers to hold the liquids.
  • Plastic tweezers
  • 0.8mm, 1mm, and 1.5mm drill bits
  • Water
  • Acetone
  • Any  UV-A light source
  • A blank PCB with UV photo layer
  • Hydrogen Peroxide. 35% concentration. lower is  good too
  • Hydrochloric Acid. 10 % concentration
  • Caustic soda, also known as Sodium Hydroxide.
  • The first thing you need is a design of what you want to make. There are all kinds of programs out there that  you can use . You can do it by hand too. You can use a program called EAGLE, you can find it heredownload a trial and experiment with it. As long as you have a basic understanding of electronics you will be fine. 

     When you have finished your electronic scheme, you need to print it on a sheet of transparent film. This is an important part of the process, the higher quality your printout is the better your end result will be so you have to have a good printer. Take note what your component side is, because you might need to mirror the image.

    From here on begins the actual Etching process.  First measure what size board you need and saw it off using a hacksaw. The blue plastic layer is the protection layer of the copper and photosensitive layer. If you damage the board don’t use it because it will turn out bad. Don’t remove the plastic layer until the very last moment when where going to expose it to the UV light. Remove the protective layer, and place your printout the way you want it, and again take notice that it’s mirrored.

    Exposure

    This step is just as important as the quality of your design; most likely you need to experiment with what the best exposure time with your lamps is. 

    Remember this is a trial and error kind of thing, if you don’t succeed the first time try again.  So after exposing the board to the UV-A light  it’s time to and develop it. Develop it immediately.  photolayer board needs some time to develop. The purpose of the photolayer on the board is to protect the copper. 

    After developing we need to remove that soft exposed layer, for that where going to use caustic soda, also referred to as Sodium Hydroxide.  Put a good teaspoon full in to some water and stir until all the little white balls are gone and you are left with murky water.

    Now get your pair of plastic tweezers and grab the exposed board, dip it in the solution you will see a brown purple glow oozing from the print and your cirquit should become visible. In this process wiggle the board around a bit, when all the lines or what ever you made are visible quickly rinse it with some tap water. The hardest and most crucial part is over.

    Etching 

     Time to break out the chemicals.  You can get the chemicals at your pharmacy or chemical store. There are few more ways to etch a PCB, but this is the only one where you do not need to heat the liquid, so no need to buy expensive equipment to do that.

    When making a cold etching bath, please be careful dealing with chemicals, even though these aren’t the strongest around they will leave nasty irremovable stains on your clothing.  When dealing with chemicals wear rubber gloves and safety glasses. 

    Right now, get a little plastic container or glass bowl and add about 3 to 4 bottle caps of Hydrochloric Acid (10%). To the Hydrochloric Acid we need to add the Hydrogen Peroxide, put about 1 to 1.5 bottle caps into the bowl, and stir with your plastic tweezers to properly mix the two chemicals.

    There are a few things you need to know, when Hydrogen Peroxide is mixed with an acid it will react with it. The reaction will not be harmful tough, all you get is pure oxygen. This process will continue until the Hydrogen Peroxide is gone, leaving you with the water it contained. By doing this the Hydrochloric acid will lose its strength because its slowly getting diluted with water. If the etching goes really slow add some more Hydrogen Peroxide and if that doesn’t help, you will need some new Hydrochloric acid. You can store the solution in a plastic coke bottle or a glass jar, but don’t fully close the lid because the pressure will build up and your bottle or jar could explode, the best way to prevent this from happening is to puncture the cap or lid with a nail, so the buildup air can escape.

    Now get your developed board and place it in the solution, be sure the whole board is submerged.  Continue wiggling the board every so often, for approximately 1 to 5 minutes.

    After about 1 or 2 minutes you’ll notice that you can see some board through the copper. Frequently check until all of it is gone, when the cirquit is clean and clearly visible get it out of the bowl and rinse it with water. Remember we don’t want to leave it in the solution for too long or it will begin dissolving the protected copper. Congratulations, you just made your own Printed Circuit Board.

    Finishing

    There are only two things left to do; first you need to remove the photo layer that’s still on the copper. Use some nail polish remover or acetone to remove that layer, when you’re done the copper should look shinier. Now just drill the holes you need, you can do this with a engraving tool, Dremel, or drill. The most common sizes of drill bits used in PCB’s are 0.8mm 1mm and 1.5mm so use the right sized bit for the hole you need.

    You can leave the PCB clear but it can corrode without any protection, to prevent this apply a soldering agent called flux which you can get this at the local electronics store. When you are finished you can begin placing the components and start soldering.