mouldy.org

It's been a week, and I don't have a tremendous amount to show for it - at least on the business side of things. The work situation is keeping me busy, and there'll be some major changes there soon.

I did my first laser toner transfer PCB today, and it went remarkably well. This is the first PCB that I've hand-made in probably eight years, and just about everything is different:

• Ammonium persulphate instead of ferric chloride
• Surface mount instead of through hole
• Laser toner instead of hand-drawn Dalo pen
• Extremely high levels of detail (0.1mm tracks) instead of, well, the crap that I can draw by hand with a Dalo pen

I used "Kodak Everyday Picture Paper for Inkjet Prints" in the 4x6 inch size. It was a clearance special at the supermarket. I figured that I probably won't be making boards larger than 4x6 inches anyway, so not using A4 paper won't be a major problem. I had to turn on the 'mirror' option when printing to keep everything properly oriented.

Some components that I'll be using: The ruler is measuring in cm, not inches

Everything went pretty much as the online guides say it does. I cut out some PCB, filed down the edges, cleaned it with a nylon scourer, put down the paper and ironed it for a few minutes. The paper is fairly thick, so I didn't get the tracks showing through the paper. I dumped it in some water, watched an episode of The Simpsons, then peeled the paper off. Just like that. There was a thin layer of paper left, so I scrubbed at it for a few minutes with my finger, and used my tiny tweezers to scrape away some tiny stubborn bits.

After peeling off the paper

I had a slight problem with the toner spreading on the pins of my IC. They'd spread enough under the ironing pressure and heat that they were now touching each other, so I scraped away a thin line between them with my tweezers. I also managed to scrape away an intentional join between pins, so I touched it up with a thin Sharpie. The touchup was just a dot - the tip of the Sharpie is as large as two of the IC pads!

Ready to etch!: My 'ultra fine' Sharpie seems neither fine nor sharp any more...

Into the ammonium persulphate, swish it around for ten minutes and watch the water turn blue. The etch went pretty evenly, except for one track which over-etched slightly. Right next to it are two component pads that are under-etched and touching a track that runs between them. Boards this fine should probably be made professionally!

I'm melting... ...melting!

Swish Lish was kind enough to bring over some acetone (ish). I cleaned up the board and coated the tracks with flux. At this point, I can begin assembly. I tried out one of the capacitors; the solder paste does seem to work pretty well if you can keep the part in the right spot. It flows under and around the parts beautifully and does indeed reposition the part if you're lucky. It's finicky stuff, though. It's not viscous enough to be able to put down accurately on pads. I don't have solder mask on this board, so shorts between tracks may be an issue. I may have to buy a tiny screwdriver to place it accurately when it comes time to do the IC. Or I could just slap it down everywhere and remove the excess with a knife.

The board, cleaned with acetone and coated with flux: Also with nail-whitening power!

Magnification would be wonderful, though. The parts are tiny, the board is tiny, and my hands aren't quite as precise as I'd like. Skillet reflow will definitely make this easier.