For today's how-to you'll need:
- Laser printer
- Staples basic gloss photo paper (Item #471861)
- Clothes iron
- Nail brush
- Safety gear (goggles, gloves, etc)
- Copper clad pc board
- PC Board Etchant
- Synthetic abrasive scrubbing pad
Before we get started, you'll want our latest zip file
. [update: the latest file is up! --Will] It contains the library, schematic and our board layout. First we'll print out our board pattern using a laser printer. We're going to use heat to transfer the laser toner from the paper to our PC board. Laser printer toner contains plastic, so it will resist etching chemicals. Make sure you know which way to insert the paper in your printer to print on the glossy side.
Load up the board in EAGLE and hit the layers button. Unselect everything and choose Top, Pads, Vias and Dimension.
Now print the board. For the top layer, we'll need to mirror the print, choose solid and black as well. Now hit layers again, deselect Top and select Bottom. Print again, but deselect the mirror option.
Now you should have the top and bottom patterns on two pieces of the gloss paper.
Cut down the PC Board to the size of the board layout. A couple quick sharpie marks are sufficient. The saw pictured is a printers saw, originally made to cut lead lettering for a printing press.
Get rid of the rough edges on the board by rubbing it on a piece of sandpaper or with a fine file.
Rub the faces of the board with a scrubbing pad. Steel wool can work but a synthetic pad is better.
Lastly wipe the board down with some acetone. Nail polish remover is mostly acetone. Let it dry and don't touch the copper surface with your fingers, handle the board by the edges.
Place the two patterns face to face. If you don't have a light table, Hold them up to a florescent light and line up the board edges. When the dock connecter appears almost solid black, you've got it right.
Cut around the patterns, leaving at least an inch or two around the edges. Double check your alignment and lay them on top of an ironing surface. An ironing board is a bit flimsy, so we use the back of a legal pad on top of the workbench.
Place your prepped pc board between the two patterns and put your preheated iron, on the setting just below steam on top of the papers and board. Let the iron heat it up for about 5 minutes, then press down firmly for 30 seconds or so. Then work the tip of the iron over the entire board to ensure good transfer. Carefully flip the board over and repeat the process for the other side.
Soak the board in soapy water for at least 15 minutes. Scrubbing the back of the paper with a nail brush can help soak it a bit faster.
Once the paper is thoroughly soaked, carefully peel it off. Don't force it, just gently pull. Soaking the remnants and further gentle scrubbing with eventually get the paper cleaned off the board.
Use a fine tip sharpie to touchup areas where the transfer didn't stick or the trace looks thin.
This is where most of our first-timers will turn away -- and where it gets interesting. We'll be working with some caustic chemicals. Safety gear is cheap, so get some. Heavy chemical resistant gloves are handy. If you want disposable, get nitrile. (Latex doesn't do any good around acids.) We snagged a new pair of sealed vent chemistry goggles at the university bookstore for $2.25 and a simple apron was a mere $5. If you decide to work with acid, keep baking soda around to neutralize any spills.
A chemical etchant is needed to remove the extra copper from the board. Ferric chloride can be bought at RadioShack, but it's opaque, and sort of slow to etch if it's not heated. We tried one of the trendier etching cocktails - hydrochloric acid and hydrogen peroxide. 3% hydrogen peroxide can be had at any grocery store. 31% hydrochloric acid is available at the hardware store under the label of muriatic acid. It's used for pool maintenance and etching concrete.
Here we're prepared to start etching. We have baking soda, water, acid, peroxide, a cereal container, a containment bucket to catch spills, an air pump to agitate the solution and our board. We drilled one mounting hole in the board and strung a strand of wire from some CAT5 through the hole. The air pump will agitate the solution during etching. The acid has some serious fumes, so we've set up shop outdoors. A folding plastic table is ideal, since it too is chemical resistant.
Carefully measure out the chemicals. The easiest mixture to use is two parts hydrogen peroxide to 1 part hydrochloric acid. For safety, pour the acid into the peroxide, not the other way around.
Once the mix is prepared, lower the board into the etching solution. It will begin to turn green almost immediately as copper is oxidized from the board.
Even thought the solution is clear, give it an inspection, here it's just a couple of minutes from completion.
When it's finished, rinse the board with water. Once it's rinsed and dried, get out your acetone again and gently scrub all the etch resistant material off the board. A gentle run down with the scrubbing pad will get everything shiny.
Carefully inspect the board and remove any shorts that may have snuck in. We used a routing bit with our dremel to remove excess copper from a few locations.
Drilling out all the pins and vias takes time, and a few sacrifical drill bits. The ringed bit is a resharpened tungsten carbide bit from Drill Bit City
Fitting each connector takes some patience and a decent collection of drill bits. The IC socket has a couple of extra pins, so we just trimmed the leads for the last two. Soldering the connectors is standard fare.
Getting the two sides of the dock to line up perfectly is a challenge. It's ok as long as they're pretty close. One side was out of alignment by almost a pad width. We added some solder to the leads, then tweazed them in place and soldered each pin individually. Be careful not to install the dock connector upside down, like we did in this photo.
Our nearly completed dock. We didn't install our MAX232 yet because our shipment of capacitors is apparently sight seeing in Singapore. The audio out from the RCA connectors sounds fantastic, even without sheilding. And at this point what you mount it in and how you fashion it is entirely up to you. Go ahead, make the hi-fi you really wanted from the Hi-Fi.