Step 1: Schematic, Simulation & PCB Design
Draw your schematics. I highly recommend easyEDA as a schematic designer and PCB creator. EasyEDA is free as long as you keep your schematics public. It has a huge components library. I never had a problem finding my components. You can also design your components if you do not find one in the library.
Here’s the schematic that I etched into a PCB.
You can run simulations before you convert it to PCB. The auto-router is an amazing feature that makes drawing PCB a real breeze.
easyEDA provides for a one-click order of PCB at reasonable rates, which I think is a great feature if you are in the USA. You simply cannot match the PCB quality, but since I am in India, the shipping costs and other import restrictions make it infeasible for me.
So making my own PCB is the next best solution.
Here’s the PCB I made from the above schematic.
I recommend that you keep the track width for your PCB to at least 0.8 mm and the separation between tracks to at least 0.5 mm. I never had success below 0.6mm of track width and the above-mentioned dimensions are comfortable to work with. Dimensions less than that, makes it very difficult to get a clean toner transfer from page to the copper board.
Step 2: Process the PCB Image
There are two essential image processings required at this stage.
1) Make the image black and white. The image must be in two colours only – black & white.
2) Flip the PCB image vertically. – This is compulsory if you have placed any text on the PCB board. PCB etching forms a mirror image of the actual PCB board and not flipping it can ruin your texts.
Even if you do not have texts on your PCB, I recommend flipping the image. This is because the PCB produced from a flipped image has a one-to-one correspondence to your actual PCB board. This makes fitting the components easier.
I use GIMP which is an awesome and a free image processing software.
Step 3: Toner Ink Transfer to PCB
Take a print out of your processed image using a laser printer. Note that inkjet printer cannot be used for this purpose as its ink cannot be transferred to the PCB Board.
Cut the print out into the size of the board leaving a few inches of margin on all the sides.
Place the paper on the copper board and apply some paper glue to all the margins of the paper and fold it from all sides onto the copper board so as to secure the position of the paper on the board.
Keep a pestle handy. I borrowed it from my wife’s kitchen but just about any flat metal that can give a slight hammer would do.
Heat up your clothes iron to its highest temperature. Place the paper clad copper board on the Iron. Apply heating from the paper side so that the ink on the paper starts to melt.
It is important that you do not keep the board on the Iron for a prolonged period. Too high a temperature can actually separate the copper layer from the PCB board.
Every time you heat the board for say about a minute, put it away from the iron and slightly hammer all the parts of the paper using the pestle.
Repeat this process for 5-6 times.
Now let the paper clad board cool down.
Step 4: Put the paper clad board in a cold water can.
Once the board has cooled down, place the paper clad board in water for at least half an hour. The longer the better. Do not put the board into the water when it is hot as that will destroy the board.
Slowly pull out the paper from the corners to see of part of the ink has actually transferred to the board. At this stage, my board looks like the one shown here.
Step 5: Patch up for any broken links.
Clean the board in running water to remove any paper fibre clinging from the board. You can apply gentle pressure from your fingers at this stage.
Carefully observe the board for any broken patches. Patch out all broken tracks using a permanent marker. Use a magnifying glass if need be.
Step 6: Time to etch
Once you are satisfied that the track is thoroughly covered, place the board in ferric chloride solution. Ferric chloride reacts with water to give hydrochloric acid. So accidental contacts with ferric chloride solution can cause skin redness and mild burns. So, be careful.
Keep the board dipped in Ferric chloride solution for about half an hour. Take out your board once all unwanted copper has reacted and dissolved in ferric chloride,
Here’s how my board looked at this stage.
Step 7: Cleaning up the ink
Next, clean up the residual ink from the tracks by rubbing it with a cloth dipped in acetone (nail polish remover) to reveal the copper tracks.
Step 8: Short circuits and broken tracks
Inspect the PCB using a magnifying lens for any copper traces making wrong connections or traces having broken connections.
This may not always be visible to the naked eyes but may become apparent under a magnifying lens as seen here.
You can fix broken paths using conductive ink or liquid electrical tape. A few kinds of nail polish are also conductive so they too can be used to fix minor defects.
Next, It’s time to move on to drilling. Good Luck!