Etching PCBs Without Photo-Resist

1. Unetched PCB: A photo-resistive PCB costs between 1.5 and 2 times as much as a non photo-resistive board.
2. Developer Solution: A bottle of developer solution costs roughly $8 to $10. You don't need developer if you draw your circuit by hand.
3. Developer Remover: Another solution is required to remove the remaining photo-resist from the board after etching. This can run you another $10 for a bottle.
4. UV Exposure Lamp: A small desktop UV exposure lamp costs about $40. You won't need this either if you etch by hand.
5. Inkjet / Laserprinter Overhead Transparencies: These can cost you between $15 and $20 for a package of 20.

1. Unetched PCB: Depending on the size, this will cost you $10 to $20.
2. Plastic Etching Tray: Any non-metalic tray large enough to fit your PCB will do. You can pick up a paint tray or something similar at a hardware store for $2 or less.
3. Ferric Chloride Etchant: The etching solution can be bought in different sized bottles. A large bottle is about $8.
4. Fine Point Permanent Marker: I recommend the Sanford Sharpie. It costs about $2 or $3.
5. Rubbing Alcohol: You'll need a bottle of pure (or nearly pure) alcohol to clean the permanent marker off after etching. This will run you about $5 at the grocery store.
6. Miscellaneous: Rubber gloves, fine steel wool or scouring pad, cotton balls or paper towels. (About $5 total.)

The Process:

1. First, you must have an idea of what your circuit layout is going to look like. Sketch it on paper and trace the component leads to make sure that they will all fit. Keep in mind that holes will need to be drilled through the traces to solder the components to. This means that you will need to make a dot larger than the normal trace width at these points.
2. Next, trace the circuit using a soft lead pencil onto the copper board. Draw lightly so as to not make a permanent mark in case you need to erase. Use a ruler, compass, or stencil if necessary.
   
   
3. Clean the copper board using the rubbing alcohol. It is important to have a board that is free from fingerprints since they can affect the etching process. It is undesirable to have a final board with a large metalic finger print shorting out several traces!
4. For the rest of the process, it will be necessary to wear the rubber gloves. Put them on before you begin retracing you pencil guideline with the permanent marker. This will prevent you from getting any more fingerprints on the board. As you draw with the permanent marker, keep in mind that everything not covered by the ink will be etched away. In other words, everything under the permanent ink will remain as copper traces after the etching process. Make sure that you draw your traces thick enough for the amount of current that will be flowing in them. I have personally vaporized traces off of circuit boards by passing too much current through them. Learn from my mistakes! Also make sure that thick dots are present where holes are to be drilled for soldering component leads. Make sure that thin traces (less than 2mm wide) are completely covered in ink. Sometimes the ink will not flow evenly onto the copper board leaving areas where the ink is partially transparent. Recoat these areas! It is also fun to imortalize your signature, name, girlfriend's name, cat's name, or a small drawing on your circuit board. I chose to immortalize my wife's name with a little heart and an arrow through it. If you think that is cheesy, I don't care! This is my App Note and you have no editorial license!
   
   
5. The next step is to prepare the acid bath. I literally used my bath for the task! I filled the tub a couple inches deep with hot water and then placed the etching tray in the tub. The reason for doing this is that the warm water transfers heat to the etching chemical which speeds up the etching process. Place the copper board in the etching tray in the tub. Make sure that you are still wearing the rubber gloves to prevent fingerprints. If the tray is floating, you may need to let a bit of water out of the tub so that the tray will lie on the bottom of the tub. This is necessary so that the solution will evenly cover the board.
   
6. Next, pour the etchant solution into the tray so that the entire copper board is covered. It is corrosive so don't splash it on your skin or in your eyes! Also, be careful not to spill it in your tub so that you won't have any tub damage. (You never know!) Also, some archaic buildings have copper drain pipes. Since this stuff eats copper, it may be a bad idea to let it go down your drain!
   
7. It will take anywhere from 10 to 30 minutes to etch your board. Monitor the progress every few minutes. Stirring the solution and scrubbing the board gently with fine steel wool or a scouring pad will ensure that the copper comes off of the board instead of lying on top of it in a silty powder. Since the etchant is somewhat opaque, you may need to remove the board from the solution periodically to determine which areas need more scrubbing and which do not. It is important to know that leaving the board in the etchant for too long can cause the finer traces to wear away from underneath the ink.
8. Once the etching is complete, pour the etchant out of the tray into another container. This etchant may still be good for another use or two but most of the time, you will not achieve as good results if you use used etchant. Store it in a cool place for another time or take it to a waste disposal facility. Remember that pouring it down your drain may be bad! It's also not very environmentally friendly.
9. Now you can rinse the board clean using water from your shower. Make sure to dilute it quite a bit before letting it down your drain. The resulting board should have all of the unwanted copper etched away and the desired traces still covered in ink as shown below:
   
10. To remove the ink, use the rubbing alcohol and some cotton balls or paper towels. Rinse with water and repeat as necessary until the copper traces are visible and clean.
    
11. Finally, if there are multiple circuits drawn on the same copper board, you can cut them apart using a hack saw or find someone with a bandsaw or a scroll saw. The university has this equipment in the project labs. The holes for the leads can be drilled with a hand drill or with a drill press if you need accuracy. I recommend using a 1/32" drill bit for most applications. There is a drill press in the EE 401 project lab in the basement.