My adventure started with Arduino, and a book that included instructions for making your own Arduino clone board by etching the PCB at home. Arduino Robotics has a chapter dedicated to the Arduino clone he calls jduino. I want to walk with you through the process and share what I have learned. You begin with a copper clad circuit board, transfer toner to the copper and bathe the board to chemicals that will remove the copper that is not covered by toner. At a minimum you will need a black only laser printer (ink jet and color laser will not work) and a clothes iron. I purchased a Brother laser printer that was less than $100 (if you are in the US, check salescircular.com for the local weekly sales), and a non-steam iron from Amazon for $15. You can use a printer you already have access to, and although the non-steam iron works better any clothes iron will work.
Materials you need:
Tools:
Black only laser printer
Clothes iron
CadSoft Eagle PCB design software
optional – wood chopping block
optional – silicon baking sheet cover
Consumables:
Magazine with slick paper
Copper clad circuit board
Scotch Brite pad
Acetone (or Lacquer Thinner)
Paper towels – I like the Scott brand blue Shop Towels
The design process, or simply printing someone else’s design in this case is done with Eagle PCB design software from CadSoft. Eagle will permit you to enter a schematic then it will provide a physical footprint to layout the components and traces for a Printed Circuit Board (PCB). While the commercial version of Eagle is expensive, there is a limited free version that will serve most of our needs; it is limited to two layers of copper and a modest board size. The Eagle design files for the jduino are available from the publisher’s website http://www.apress.com/9781430231837 and provide a good starting place for the project.
After loading Eagle and opening the Arduino_clone.brd from the chapter 6 files, you will have a view of the copper for the traces. We are going to use the laser toner transfer method and need to hide component outlines, notes and anything that doesn’t represent copper traces. While viewing the board in Eagle, click the View menu and select “Display/hide layers…”. We want to only display layers 16 Bottom, 17 Pads and 18 Vias; the fastest way is to click the “None” button at the bottom of the new window, then click the numbers 16, 17 and 18, and click OK to apply the view. We will print the schematic to a sheet of glossy magazine paper; don’t use a magazine with newsprint quality paper as irregularities will cause problems with the transfer later. Tear a sheet from a magazine and load it into the laser printer. Back in Eagle, click File, Print and make sure the only options checked are Black and Solid, clearing Mirror, Rotate, Upside down and Caption. Click OK to print it on that magazine page…
The reason for the slick paper is to provide a poor physical bond with the toner, and most magazines use a soy based ink that will not transfer off the paper and so the original print on the page does not effect our use. Be careful not to touch the toner after printing, because the oil will prevent the toner from bonding to the copper. Trim the page down to the newly printed area and set it aside while we prepare the copper clad board.
There are many places to obtain copper clad board. Radio Shack carries a double sided pc board that will work, but tends to be more expensive and since we will only use one side it increases the time to etch without a benefit. I pass through a city with Fry’s every six months and when I am not near a Fry’s I mail order from them. They carry an 8×10 single sided copper clad pc board that works well. Just cut the board to the size required; I found I could cut the 8×10 board and get 11 jduinos. Measure for a cut, use a carpenter’s triangle and a breakaway blade to cut the surface of the board. Then you can break the board across a sharp angle similar to plexiglass. Wear eye protection and gloves.
Scrub the copper with a Scotch Brite pad to remove oxidation and to provide a more porous surface. Clean the surface with lacquer thinner or acetone to remove dust, oil and contaminants that would interfere with the toner adhering to the surface. Apply acetone to a paper towel, wipe the surface, fold it over and repeat. Clean the surface until you do not see anything on the paper towel, then clean the surface three more times. A common problem is that the surface has contaminant that isn’t visible to the eye but will prevent toner from bonding to the copper. I prefer Scott Shop Towels because they don’t fuzz up or tear while scrubbing; they are a blue thicker paper towel that is commonly sold in hardware stores. Be careful not to touch the copper after cleaning or you get to start over with the acetone.
Find a heat resistant surface that will support you leaning on to the surface with the iron. I use the kitchen counter, place a thick wood chopping block on the counter and then a silicon baking sheet cover over the block. Set the iron to the highest heat setting and let it heat up before using it. Place the PCB with the copper side up. Place the magazine paper on the PCB with the toner down, facing the copper. Place the iron on the paper and let it sit for 30 seconds. This will heat the toner and it will to adhere to the copper. Be careful not to move the paper or the iron because moving either will cause the transfer to be messed up.
[add a photo of the chopping block with silicon baking sheet cover with iron]
After the 30 seconds, lift the iron and place a piece of scrap magazine paper over the board (don’t remove the page from the copper though) and move the tip of the iron over the whole surface of the board to ensure that all parts of the paper are flat against the board (no wrinkles). Again place the iron so it covers the whole trace magazine piece and press down on the board for 3 minutes. After 3 minutes remove the iron, turn it off and let the board cool until you can safely touch it.
The toner only had a marginal hold on the magazine paper, and by heating it the toner has adhered to the copper fairly well. Soak the paper in warm water until the paper become slightly pulpy. Gently pull the paper away and use your finger tip without your finger nail to rub the paper away. While the toner is adhered to the copper, it is possible to scratch it away with your finger nail.
Before you go any further, check that the traces transferred completely. It is simple to use an etch resistant pen or fingernail polish to touch-up missing traces at this time. I’ve made some changes to the design, but here is an example of the toner on the copper. The darker circles are areas I touched up with a pen.
Next, the etching…