After making a few of my circuits on perfboards I decided it was time to move on to printed circuit boards. Perfboards are probably the best choice for smaller circuits, but as my circuits got bigger and more complex it was difficult to wire everything and make it look neat. Also I really wanted to learn how to design printed circuit boards since PCBs are used in almost all electronic devices these days.
Of course, after you design your PCB you can get it manufactured by a PCB manufacturer, but making your PCB at home is fun and has many challenges to work through. There are many ways to make your own PCB at home. The method I am using is commonly called the UV-exposure method. And I will show you the process I use and how I solved certain hurdles along the way.
Before you decide to make your PCBs at home, there are a few things to consider.
- You will be working with chemicals and will need to take the necessary safety precautions.
- After you are done with the chemicals you need to find a proper way to dispose them. No you can’t flush them down the toilet! (This will cost more down the road)
- You may have to purchase additional equipment (see the list of things needed below)
When I was making my first PCB at home, I had to find alternative ways of doing certain steps since I didn’t want to spend a lot of money on expensive equipment like UV exposure kits. My first step is to look around the house and find a way to hack something to get what I want.
Equipment and materials needed
- A PCB layout – I am going to make my Music and Lights PCB.
- Transparency film – The type of transparency film will depend on whether you have a laser printer or a inkjet printer. Transparencies made for laser printers won’t work with inkjet printers and vice versa. I have an inkjet printer, and I found inkjet transparencies at Staples.
- Printer – A laser printer or an inkjet printer will do.
- Pre-sensitized Copper clad board – These boards have a photosensitive coating on top of the Cu layers. And they are either positive or negative acting. You will need a board that is positive acting. You can get them double-sided or single-sided. I will be using a double-sided board for my Music and Lights PCB. The boards come wrapped and you should keep it that way until ready to use.
- Two desk lamps with fluorescent light bulbs – For a double-sided PCB you need two lamps, one for each side. Regular light bulbs won’t work well (or take a really long time) since the photosensitive coating needs shorter wavelength light (near UV) to change its chemical properties.
- Photoresist Developer – These come in two flavors (but don’t even think about drinking them!) positive or negative. Since I am using a positive acting pre-sensitized board I need a positive developer. You can find these at your local electronics store.
- Etching solution – There are a few etchants you can use, but the one I am using is Ferric Chloride.
- Nail polish remover – This is used to remove the photoresist after etching is completed. If you don’t already have this your mom or sister will.
- Drill and drill bits – A hand drill won’t work unless it is a small one designed for PCBs. I use a small drill kit I found at Jameco (Part no. 2113252), which came with two drill bits and a stand. The size of drill bit you need will depend on the components on your circuit. But I find that a 1 mm drill bit works for most components.
- Plastic containers – large enough to put your board inside flat with the solutions. Metal containers will react with the solutions and should not be used.
- Sheet of glass – From a picture frame. To put over the pre-sensitized board during exposure. I will explain why this is necessary when I get to that step. Also since I have to expose both sides of the board at the same time I am using a couch table that has a glass plane in the middle. This is a hack I will explain later.
Since you are gonna be working with chemicals you also need the following safety equipment and a well ventilated area to work with
- Safety gloves – The photoresist developer (NaOH) and the etchant (FeCl3) are corrosive.
- Eye protection
- Respiratory mask – The photoresist developer produces a white powder when dried up, and the fumes of Ferric Chloride is toxic and can cause burns.
Once all the equipment is gathered, it is time to develop the PCB. This is where the fun begins, and it deserves its own post. Stay tuned!