Begin by printing out a to-scale representation of the front and back of your boards on separate pieces of paper (1), make sure that along with each side’s copper mask you also print any Vias and or pads which need to be present. In eagle layers that would be [Top Copper, Vias, and Pads] for the “front” and [Bottom Copper, Vias, and Pads] for the “back”.

If you look at the final board layout image you’ll see that I have also strategically placed alignment marks at the 4 edges of the board, these are marks that I can line up later to ensure that the front and back layers are perfectly aligned, which is important because if they are skewed then your via’s and pads wont line up and the board will become useless.

Step 2: Prepare Substrate

Next, cut out an amount of silicone sealed laser photo paper (2) which completely covers your design(3) (refer to this pdf if you don’t know what that means), you will need one piece for each layer you are printing, make sure to leave about 1/8 to 1/4 inch extra border which will make it easier for you to insert the copper clad later and tape the edges to align them.

Step 3 Apply Dextrin:

Next we are going to coat one side of these two pieces of photo paper with dextrin adhesive(4), again if you don’t have any please refer to the how to create dextrin PDF in the previous posts. Begin by using an eye dropper to place 3-4 drops of dextrin glue on the paper (use more or less depending on the surface area you are working with, in my case 3 or 4 was the most I needed) at first the dextrin glue will tend to bead up(5)(6), that’s OK, just keep spreading using a roller or a small paint brush until it begins to get tacky at which point it will begin to adhere evenly. Obviously repeat this step again for the second layer if you are producing one.

I have had some people ask me what a coated piece of paper is supposed to look like, so for reference i have included a photo(7) where the left piece is coated with dextrin (very light yellow coating) and the right piece of paper is not coated. You’ll also notice the coated piece is slightly curled up which is OK, if you want it to flatten out then just heat it for about 30 seconds under a warm light bulb to dry it otherwise rest assured your laser printer will dry it out plenty quick.

Step 4: Print

Next, using a small amount of masking tape go ahead and tape your dextrin coated paper over the original design template that you printed out(8).
And print!(9) Remember to mirror one of your sides otherwise you’ll find its curiously hard to line up your layers in the next step…

Step 5: Align Layers

Now remove the masking tape from the dextrin paper and arrange the two layers such that they are facing one another and line them up, this step is crucial, especially if you have a complex board, once the two layers are lined up then tape them together using more masking tape(10)(11), leaving an opening in at least one side to slide the copper in after we prepare it.

Step 6: Prepare Copper Clad

Next cut out a piece of copper clad to match your board size, in my case that’s 3.5 by 2 inches, use an Xacto to score the board and then snap it or even cut it out with a good pair of scissors, either way just make sure that after you have your piece cut out that you clean it. Copper clad oxidizes(12) while it sits in storage so you need to scrub that layer off(13) with some steel wool or a pot cleaner, after you have taken the layer of oxidation off it doesn’t hurt to wipe the entire board down with some acetone or alcohol(14) to remove any dust or oils that might be present.

Notice the difference in the copper before(12) and after(13) cleaning in the images.

Step 7: Prepare for Transfer

Next you’re going to slide your freshly cleaned and dry copper clad in between your two dextrin coated copper mask layers making sure to line the board up with the edges of your mask, its hard to show this step with an image(15) but it should be fairly self explanatory what you’re doing here.

Step 8: Transfer

Next you need to apply heat and pressure to the entire sandwich in order to transfer the toner to the copper clad from the paper (hence the name toner transfer method) I use a small lamination machine(16)(17) because it applies even and consistent pressure and heat which tends to produce excellent results, I have also used a clothes iron with mixed results, if you use a lamination machine 8-10 passes through should be plenty, if you use an iron the rules vary from iron to iron so you’ll have to play with it and see what works. Generally speaking 5 minutes of solid ironing should do the trick, and make sure you put something between the transfer paper and the iron like a layer of wax paper otherwise you will burn your transfer paper.

Step 9: Dissolution

After you transfer the toner to the copper clad you need to remove the paper that the toner is also fixed to, this is where the dextrin comes into play, by soaking the entire sandwich in warm water(19) you expose the dextrin to water making it dissolve and separate the toner from the paper effortlessly.You will see wrinkles start to form in the paper(20) as the water penetrates into the dextrin layer and dissolves it.

Step 10: Separation

After letting the board and transfer paper soak for about 5 minutes its time to peal the paper off the copper clad, Be gentle and peal back slowly, if a little paper stays behind its OK but ideally the separation should be effortless due to the dextrin(21)(22)(23). If there is paper remaining simply remove it by rubbing it off, you just want to make sure its out of all the spaces between the toner because if it isn’t it will act as an etch-resist and it will cause bridging in your board.

Step 11: Corrections

After you’re satisfied that there isn’t any paper left where it shouldn’t be look over your entire board and make sure there aren’t any breaks in your traces(25)(26), if there are use a fine point sharpie and draw them back in(27)(28), the sharpie ink will act as an etch resist and prevent the breaks from actually etching out.In the image you can see some red tinted areas where I have used a sharpie to correct some gaps in toner.

Step 12: Etching

Finally we are ready to etch the board, I typically use ferric chloride(29) which takes approximately 15 minutes to complete an etch at room temperature, after the board is done etching the copper will have been removed where there was no toner or other etch-resist(30)(31), but the toner will remain, use the same steel wool or pot cleaner that you used to originally clean your copper clad to remove the toner from the now fully etched board.

Step 13: Admire Your Work

At long last you have your completed board ready to solder(33)(34)(35).

Don’t forget to recycle your etchant(32), ferric chloride can be used many many times over and isn’t bad after once use.

More images and a couple videos of a demonstration of this process can be found at http://www.phx2600.org/archive/2009/09/05/september-2009-meeting-history