Two sided PCB using toner method

Step 4 Etch and clean

When you are satisfied that the critical small features are ready, then put your board in a plastic or glass container and pour enough PCB etchant over it to cover it. I use the Ferric Chloride etchant sold at Radio Shack. Gently swirl the dish with the board and etchant until it is finished. Careful not to spill on anything metal and chromed since the etchant will mess up the finish with a quickness. In most cases, where the bottom layer has a few traces and a ground plane, it is not necessary to flip the PCB during etch. Just make sure to get the board moving around the container so that the bottom etches too. If you have detailed delicate features on the back, you may want to lift the board repeatedly during etching with a plastic fork in order to help the back etch without scratching it. See pic.

When the board is done etching, you need to get the board out and rinse it with lots of water. Dump the used etchant in your toilet and flush it as recommended by the manufacturer on the bottle. As you can see from the pic, you should be able to hold the board up to a light and see through the board at this point to verify the alignment of the top and bottom layers.

Cleaning off the toner is a pain in the butt. The easiest way is to use an aggressive solvent such as brake cleaner or acetone (nail polish remover) and a rag to rub the toner off. Using your preferred method, scrub the toner off the copper and get out your multimeter to test if any of the traces are shorted together. I find that long parallel traces often have small shorts between them if you don't get all the paper off prior to etching. A toothbrush helps. If you find that some traces or pads are shorted, then using an Xacto knife or similar, scrape or cut the copper until the circuit is open. Once all the circuit is verified in this manner, you can start soldering down the parts. I find that putting the fine pitch components down first is key, so that you can verify each pad as you go. Since the toner smooshes the pads of QFPs and TSSOPs and the like together, it is easy to form a solder bridge between pins. Take your time and have your solder wick handy.

Happy building!

Comments

[qwertyboy]

For cleaning, I just use some fine steel wool. It takes the toner off quickly, removes any tiny shorts, and shines everything up. After that, I usually wipe the board off with some acetone to get rid of any oils or other nasties and spray a light coat of clear onto the board. It keeps everything shiny and kind of acts as a flux.

[jmengel]

When you say clear, do you mean clear coat spray paint? It doesn't interfere with soldering at all? I've had some of the boards I've made get pretty corroded after being in use for a long time in my basement (high humidity). No failures but the corrosion is ugly. Thanks!

[qwertyboy]

Yes, clear coat spray paint. As far as I can tell, it doesn't interfere with soldering.

[lee321987]

I just did my first board. I had my design printed by Fedex Office (formally "Kinko's") on their laser printer.
Acetone (Klean-Strip brand from Home Depot) removed all the toner with VERY minimal effort.

I can't comment much on the Fedex Office paper/printer/toner because I have nothing to compare it to.

[hondaman900]

I found the best way to clean off toner is to use non-acetone (acetate) nail polish remover. Wet a wad of paper towel the same size as your PCB with the acetate, and leave it to soak on the board for about 5 minutes. It should then wipe off easily with that piece of paper towel or another wetted with the acetate.

Bigger question for homemade double-sided boards is how to solder the pins under sockets and relays on the component side of the board without a bunch of extra vias to keep the component pad connections all to the bottom layer?

[cdvs]

This is my solution: http://DiyPcbVias.com

[jmengel]

The answer is more heat and more solder.  Or you can cheat the components up from the board enough to get an iron underneath.  I prefer the first method.

[sarubin]

Great idea and good instructions. I have one suggestion with respect to improving the "alignment marks." For circuits that include small components, like ICs, it is very important to have exact alignment of the two sides of the circuit. I aided this alignment by punching small holes (pin holes actually made with a pin or needle) in some of the pads on the laser print. I made these holes around both the periphery of the circuit and particularly included a small number of holes inside the pads of the ICs (required very precise alignment because the pins were only 2 mm apart in my circuit). Then, when the two facing laser prints are held up to a window (or, in my case, I have a backlit illuminated table) the light shining through the pin holes of one side of the circuit really helps precisely align the circuit printed on the facing page.

[jmsaltzman]

Sound like a great way to line them up.  Old thread, I know, but I found it trying to figure out vias-- awesome advice re: fluxing the pads and lead!  Off to get flux in a few minutes and try...

I've had good 2-sided transfering results with this simple method:

• I put both sides of the board (one flipped) into a single pattern image, with a space between them for the thickness of the board, printing from Photoshop with "crop marks" turned on.
• I gently curl the paper over (with no creasing) to align the crop marks, then tape those edges together and press the paper together to get a soft fold.
• Then I insert a blank pcb strip at the fold, pressing it in to get a square crease to hold the edge of the final pcb.
• Folding it again at its end, perpendicular to the first fold, I end up with a nice corner pocket to drop my pcb blank into.

To laminate, I put the blank into the pocket and feed it through my laminator.  After one pass, I cut off the folded over side of the pocket (to keep the peper thickness even) and laminate another ten times or so.  I've been getting very nicely aligned layers.

[stuart57]

This has been an absolute education for me and i cannot wait to give this a bash. I do however need to know where I can purchase all of the needed equipment  mentioned, As I live in London,England the small village across the pond.  
            Hope you can help? Many thanks Stuart and Emma

[lsymms]

Question and a tip. question: I've tried acetone and it's a bear. Mostly because it evaporates so fast. Is brake cleaner easier to work with? additional tip: use avery label backs. After removing the labels, print on the glossy side of the backing. Iron as per instructable, and leave it to cool until it gets to room temp. The backing should come off leaving perfect toner traces with no residue. I've just thrown out the labels or hand written on them before using the backs but I think you should be able to print on the lables and use backs. Buy the full sheet or half sheet labels as the smaller sized ones put perferation lines in the backing.

[lsymms]

UPDATE 2: different toners react differently to acetone. My Samsung's toner comes off in one wipe with toner.

[JohnnyVegas]

Just pour a cap full or two of acetone on the board and let it sit about 10-20 seconds first. Then just wipe. All toner will be removed. If some residue still remains, do it again.

[lsymms]

Good suggestion! I'll try that next time I have problems.

[lsymms]

UPDATE: Avery changed their backing on their labels from the last time I used them. Now they have angled slices along the backing to aid in automated label affixers, which means this won't work at all (there goes $12). I'll be trying the kinkos paper on very small traces and will report back.

[jmengel]

The avery back thing sounds interesting I will have to give it a try. Brake cleaner also evaporates quickly, but it was the only hard core solvent I had handy that could remove the toner.