In this article Bernard Klinc shows us his homemade PCB process. He gives step by step instructions with plenty of pictures. Bernard will receive a giveaway item of his choice from the hobby parts for articles project here at uCHobby.
We all know the fancy companies that make PCBs. The do make great quality boards but they will pretty much suck your wallet dry. Mostly they have a minimum order of 10 boards, even a single board may be expensive and it might take over a week for you to get the board. So they are a especially bad idea if you only want 1 board and you need it fast. So how to get around this problem? Well make your PCBs right at home of course!
First of all we need a few basic materials:
- Copper boards
- UV lamp
- Transparent foils
- Inkjet or laser printer
Now you may be worried how much this all is going to cost. Well the copper boards can be found at A4 sheet sizes for 4 or 5 € (It will take you forever to use up such a big board) Also you can buy boards that already have the photoresist applied to them, if not you can buy photoresist on a spray can and spray it on. That photoresist spray will set you back about 5 to 10 Euro and will last very long. The acid I use is ferric III chloride. You get about 1kg of the dry stuff for 6 € (It becomes acid when mixed with water and 1kg will make a LOT of acid). And the developer is dirt cheap 1.80€ got me 250 grams of NaOH, this will give you about 2 or 3 liters or developer when mixed with water (NaOH is very strong so it needs to be mixed with a lot of water). You probably already have Acetone at home, the most popular use for it is nail polish remover and you can buy it in any drug or hardware store. As for the transparent foils you can get that at any better office supply shop
Now the UV lamp is the tough part. Most photoresist reacts on UV-A and UV-B light. The typical UV lamp or so called black light used in a night club or something will have a filter that takes out the
UV-A and UV-B part of it, this is because that part of UV is dangerous. Without the filter people sitting under that UV light would get sun burn on the skin and eye damage if looking at the light for longer periods. UV-A light is so bad it even kills microorganisms. But I found a local electronics store sell these special unfiltered bulbs as replacement bulbs for the UV exposure boxes that they sell (too bad the exposure boxes cost like 300 to over 1000€) But the UV bulbs cost only 10 to 20€. I brought me one of those and mounted it in to the case of an old broken printer (BTW ripping apart a printer is the best for getting quite strong motors). Used a florescent light ballast to light up the UV bulb.
1) Create your PCB design using one of the many PCB design programs on the web. Personally I use Cadsoft Eagle, but you can use any program you want even MS Paint (No please no, don’t do a PCB with that)
2) Print your design on a transparent sheet. Set your printer to a high quality setting so it applies a thick coat of ink, that will make sure no UV light can get trough.
3) Apply and dry the photoresist on the board or if you have boards that already are coated then pull the protective foil off. Put your transparent sheet on top of the board and put a plane of plexy or glass on top of it all so it holds it still. Now just close your UV box and plug in the UV light. Leave it in there for about 3 to 15 minutes (Depends a lot on the photoresist you use and how powerful your lamp is, for me 10 minutes seems to work the best ) With the photoresist I use “Positive 20” the UV light makes the board turn blue but the tracks are green. Some photoresist coatings are transparent so you can’t see this.
4) Developing the board is done in a water solution of NaOH. Basically the UV light made the photoresist weaker. So now the developer eats off the photoresist that got under UV. The developing is done when the copper is clearly visible agent. Like in the photo.
5) Now we wash the board and throw it in to the ferric chloride that we dissolved in water. This will take about 30 minutes at room temperature. Can be shortened down to 15 minutes if you agitate it. And down to 5 minutes if you heat it up to about 40 to 50°C
6) Now the board still has the photoresist on it making it look ugly and it’s not solderable, so we need to clean it off with acetone or a similar solvent. It comes of very easily (The clean part in the photo was done with a single gentle wipe). After cleaning the board is nicely shiny.
7) Now comes drilling. For this I use a 12V mini drill. It spins at 20 000 rpm so it’s great for PCBs. You can get tiny drill bits for PCBs at electronics stores the bit currently in there is only 0,8mm.
I can’t make a real silk screen but I can make something like the silkscreen. It’s simply printing out the component layer in eagle on a sheet of high q
uality paper and gluing it to the top of the board. Not only does the board look better it also helps you place components in the right spots
9) Finally solder the components on to the board and its done. (In case you didn’t figure it out by now this is a stereo audio amplifier)0
The PCB manufacture using this photo method may be a bit complicated but it creates incredibly precise results. It is possible to etch with the same precision your printer can print. Also it doesn’t cost a lot, you can easily get everything you need to make PCBs for under 50€. You won’t regret getting in to PCB making.