Time to start making the I2C Relay IO board I designed up a month ago. It’s taken me this long to get around to production because I have had to get a few things together to make this happen!
So for PCB production here is my list of things you’ll need:
- Artwork (KiCAD will give you PS or SVG)
- Artwork printed onto OHP film with either a laser or inkjet printer
- A light box/UV exposure box
- Photoresist developer (I’m using Electrolube PDN, 1 part to 4 water by vol.)
- Etch solution (either Ferric Choride or Sodium Persulphate)
- A selection of glassware
- Rubber gloves and eye protection (all very “Breaking Bad” sounding!)
The artwork needs to be printed out on clear overhead projector film. I always print two copies and tape the two together to get an extra dark image.
I don’t yet have a UV source so I used the sun.. works fine, 5 minutes exposure and into the developer. The developer is spec’ed at 20C but I turned up the heat to about 28C as it was taking all day to do anything!
Once the image was good and clear time to take it out of the developer and rinse with water, at this point the copper should be shiny. This takes about 5 to 7 minutes.
Into an etch bath at about 50C..
5 minutes later we have some action, the last of the copper is being removed.
Rinse again under water and dry. The resist comes off with wire-wool or nail polish remover.
Dremel at the ready, with diameter 0.8, 1.0 and 1.2mm bits. Forget HSS bits, drop some more cash and get solid-carbide drills, they last much better!
Mount up the parts.. and I’m very happy, worked first time!
Here is a close up of the tracks: