PCBgogo

'So Easy' PCB

Designing and making a printed circuit board for a hobby electronics project need not be difficult. By following some simple procedures here can make a great PCB in 2 hours or less. Once you have learned what to do, you can create PCB’s almost at will. You can routinely produce quality PCB’s for all you projects.

MS Paint

MS Paint with a blank drawing area. Save the blank drawing area in .bmp format. Close MS Paint.

Software Tools

The software required is MS Paint and the image viewing software IrfanView. MS Paint is a standard on Windows based computers and IrfanView can easily be downloaded from the Internet. Since you will be using MS Paint a lot it is a good idea to download a tutorial from the Internet to learn time saving tips and tricks. The first order of business is to open MS Paint. You will see a blank drawing area. Save the blank drawing area as a .bmp file. Unfortunately MS Paint offers no way of adjusting the critical dots per inch (DPI) parameter of the .bmp file. To do that close MS Paint and open the saved .bmp file using IrfanView. From the Image menu choose Resize/Resample and select the required board size in inches. Next change the DPI parameter to 50 DPI. Save the resized image as a .bmp file again. Open the resized .bmp image using MS Paint once more. 50 DPI means that 1 pixel in MS Paint equates to a square of 20mils X 20mils on the resulting PCB (1 mil is one one thousandth of a inch).

You can check that the DPI parameter has been correctly set using the Image/Attribute menu item in MS Paint (Ctrl+E). Now you are ready to start drawing your PCB. Using the magnifying glass option to zoom in on the drawing area and then select the menu item View/Zoom/Show Grid (Ctrl+G).

It is a good idea to have at hand a steel ruler to measure up the components you intend to use for the circuit. For more complex circuits it is useful to have a redrawn circuit diagram where things like transistors are drawn as a physical outline rather than as standard symbols. That way the real component pin order is accounted for, allowing a more direct translation from the circuit diagram to the board drawing. When you are finished save the .bmp image. If you are going to use the toner transfer method to make the PCB you should select the menu item Image/Flip Rotate (Ctrl+R) and flip horizontal before saving the image. As the final step open the image again in IrfanView. Select Print from the File menu. There you will find a ‘Print size’ option. Choose ‘Original size (from image DPI)’.

IrfanView Resize

IrfanView resize dialog. Select the board size in inches and choose 50 DPI.

MS Paint Check

Check the board size and DPI from the MS Paint attributes menu option (Ctrl+E).

Design the PCB

Design the PCB. Make sure to use the magnify option. Then select the grid option from the zoom menu.

Red Grid

You can also make 5 pixel by 5 pixel (0.1 inch by 0.1 inch) template to help you lay out your PCB.

MS Paint Flip

You can flip the PCB image horizontally using MS Paint for use with the toner transfer method.

IrfanView Printout

Use IrfanView to printout the PCB image at the correct size. Use the 'Original size (from image DPI)' option.

The Toner Transfer Method

A laser printer works by fusing toner onto the surface of a sheet of paper at somewhat high temperature.

Obviously one surface of the fused toner becomes attached to the paper. If you apply heat again you can fuse the other toner surface to something else. The paper can be removed later using water. One problem with this method is that paper fibers become embedded in toner, making it less suitable as a resist for etching. Using paper with a shiny surface (even magazine paper) can reduce the problem. Fast etching can also help as it reduces the amount of time the embedded fibers have to swell in the etching solution; where the swelling disrupts the resist and causes pitting.

First things first though - you need to cut some copper clad laminate. Scoring with a sharp blade and breaking over an edge is one possible method. If you are working with phenolic board it can be cut with a scissors after being dipped in hot water or heated with a clothes iron. Once you have cut the board sand the edges and clean the copper surface. Try not to scratch the copper surface too much.

Next you need to iron on the printout. Set the iron on medium heat and press down hard for a few seconds. Once the toner has started to fuse to the copper you can move the iron about to ensure even adhesion.

Once the board under the paper has become sufficiently hot throw the board and attached paper into water. After a few minutes start peeling off the paper carefully. Try to remove any remaining paper fibers between the tracks with a sharp object.

Etching solutions

Ferric chloride solution is often used etch PCB’s but should be avoided for home use as it can cause irreversible property damage. For example permanent staining of concrete. It is best to use a copper (II) chloride based etching solution. You will need to find some hydrochloric (muriatic) acid product in a supermarket or hardware store. Some examples would be acid toilet cleaner or concrete cleaner.

Any concentration between 10% and 40% is fine. Follow all the safety directions for the product.

Quarter fill a plastic bottle with hydrochloric acid and add table salt until no more will dissolve. Push in a reasonable amount of copper wire in the form of strands into the bottle. Close the bottle, attach a warning label and place out of the reach of children. Every day or two open the bottle and allow more air in for a minute. After a few days all the copper will dissolve. Finally you should have a bright green copper (II) chloride etching solution.

Put the board in a clear lunch-box and add the etching solution. Close the lid of the box and agitate the box until the etching is complete (about 10 minutes). The solution will turn a dark olive green color as the copper (II) chloride and the exposed copper react to form copper (I) chloride.

When you have finished etching pour the etching solution back into the bottle and close it. Rinse the PCB very thoroughly in cold water. After drying the PCB you can remove the remaining toner by scrubbing or with all due care you can use nail polish remover. The etching solution can be restored to it’s bright green color by opening the bottle to the air briefly over a couple of days. Eventually the etching solution might need the addition of more hydrochloric acid and salt solution but otherwise it will last indefinitely.

Finally

PCB’s are not so difficult to make using these methods. You can easily produce good quality PCB’s for all your hobby or professional products with a little bit of effort after a light learning curve.