Making Your Own Printed Circuit Boards
Here are some instructions and notes on fabricating your own printed circuit boards (PCB). It’s a messy, time consuming job, but if you have several boards that you want, or if you just have the “DIY bug”, it can be worth the time.
Summary of the Process
The idea is that you print an image of a printed circuit board on to a copper clad fiberglass board with a print medium that is resistant to acid. Then you place the copper clad board into a warm acid bath that will eat way all the copper that is not covered and protected from the acid by the acid resistant print medium.
Dunking the board in the acid bath is commonly referred to as “etching” the PCB. When you are done etching, you rinse the acid off the board and wipe off the acid resistant covering and you have a fiberglass board with some copper trace design left on it. You can then drill holes in the pads for the part placements and you have a nice PCB. Here is a brief summary of the process, with more details later on in this document.
- Transfer the PCB mask (image of the circuit traces and pads) to copper clad board with an etch resistant material.
- Etch the PCB in a solution that will remove all the copper that is not covered with the etch resistant material.
- Drill the PCB, assuming you are using the common “hole-through” parts, where the parts are place on the non-copper side of the board and soldered on the copper trace side.
Transferring the PCB Mask to Copper Clad Board
There are three popular methods of creating PCBs at home:
- Using a photo-resist pen to hand draw the PCB mask on copper clad board
- Copy the PCB mask to a transparency sheet, then using specially sensitized PCB materials, transfer the image on to the photo sensitized PCB material with light.
- Use iron-on transfers to get the PCB mask on to copper clad board.
We have found that the best method for most home builders is option three, so we will be mostly discussing that method here. There are other internet resources that discuss option two if you are interested.
We don’t know of an easier, more reliable way to get the layout on to printed circuit board than with Techniks Press-n-Peel Blue product, information is at www.techniks.com. www.techniks.com/how_to.htm shows how to use Press-n-Peel Blue. You can order Press-n-Peel Blue online at www.techinks.com or many other outlets. It is relatively expensive, but if building PCBs is an on-going hobby, it will be worth the price. It can also be purchased from most good electronics catalogs in packages of 5 sheets. Follow the Press-n-Peel Blue instructions to get the layout onto the copper clad board.
Keep in mind that if you use a transfer method, you need to use the reverse image of the PCB mask. This is why all of the PCB images on www.generalguitargadgets.com have the PCB images in reverse.
Print out the “Ready for Transfer” board layout PDF file for the project you want a PCB. You can print on a laser printer directly to a sheet of Press-n-Peel Blue or print them out and photocopy to Press-n-Peel Blue. See the instructions that come with the Press-n-Peel and the links we’ve provided on my “Read-This-First” page to see how to do the iron on transfer.
If the Press-n-Peel does not completely transfer, which sometimes happens, we use a pen called a Speedball Painter (Fine) to touch up the areas that didn’t transfer. These are available at craft or fabric stores. They are like a pen but actually have paint in them The can draw a fine line with heavy paint that dries quickly. The perfect solution for touch ups. Sharpie pens are sometimes recommended, but we have never found them to work very well, the etchant may eat through the sharpie ink, at least to some extent.
Here are some common types of etchant solution that can be used:
- Ferric Chloride
- Ammonium Persulfate
- Sodium Persulphate
- Home-made mixture of 50% Muriatic Acid and 50% Hydrogen Peroxide.
The Ferric Chloride works very well, be careful, it leaves nasty stains on cloths and work area. These stains are permanent. The Muriatic Acid/Hydrogen Peroxide mixture is by far the least expensive alternative and works okay, but the fumes are horrible and extremely corrosive. We highly recommend that, if you use this solution, you do it outside, well away from the house or any tools. We noticed that after just one usage on the work bench, some of my tools sitting nearby had a coat of corrosion on them afterwards…just from the fumes from one session of etching! Two gallons of this mixture cost about $10.00 (Muriatic from Ace Hardware, Hydrogen Peroxide from WalMart), compared to two gallons of Ferric Chloride cost of about $30.00 (from Radio Shack). Two gallons is enough to etch about 500 or more average size stompbox boards, so quart or liter bottles of Ferric Chloride is a good choice for most home builders.
No matter which etchant you use, carefully follow the directions on the bottle and always etch in a well ventilated area.
The etchant must be warm(100 to 120 degrees Fahrenheit) to work best. We use a hot plate or a hot water bath. For the hot water bath, use two plastic containers to do the etching. One is a small container with lid (not air-tight lid) that is just big enough for one or two boards to fit in. The etchant and boards go in this container. Then get a bigger plastic container that will be used for a hot water bath. Pour the etchant into the small container, then boil some water on the stove. Pour the very hot water into the larger container (just a few inches) and place the smaller container of etchant into the hot water bath. This is a good simple way to keep the etchant very hot and makes etching go very quickly. Keep the lid on while etching, if you have a lid, it cuts down on the fumes and might keep the heat in better. If possible, place a goose-neck desk lamp, with 60 or 100 watt bulb directly over the bath to keep it all warm longer.
Be careful not to get the etchant bath too hot. It may start melting the etch resistant mask and the acid will eat way your circuit!
A drill press is highly recommended, but not entirely necessary. If you use carbide bits, be prepared to break a lot of bits unless you have a very good press and a good eye for drilling. The advantage of carbide bits over steel bits is that the carbide bits will last a lot longer before get dull and unusable. We use steel bits, they wear out faster, maybe only 200 or 300 holes per bit, but they don’t break as often as carbide, so they can be more economical. We’ve used .034″ and #66 size bits. Make sure the chuck on your drill will clamp down small enough to hold on to the bit. The steel bits were too small for the chuck on some Dremel tool chucks, so be aware of that and check the drill you plan to use.