The first printed circuit board I ever designed and etched.

Overview

As part of building Philly, I wanted to make a homemade Printed Circuit Board (PCB). I’d never done this, so I thought good idea to try a prototype first. I chose to make a relatively simple ATtiny26 development board. Its a mostly single-side board, with a few jumper wires routed to the top layer where necessary. Read on for a description and photos…

Special thanks go to two people, Tom Gootee and David Cook. I relied heavily upon their excellent websites for ideas, instructions, and techniques for homemade PCB fabrication. They turned a hugely intimidating project into a breeze.

ATtiny26 Dev Board Features

  1. Power Switch
  2. Battery Connector
  3. LM7805 Voltage Regulator - with decoupling & bulk capacitors
  4. Power-indicator LED
  5. ATtiny26 microcontroller - with decoupling capacitors
    • Reset pin connected to VCC with pull-up resistor
    • Momentary push-button switch to pull reset pin low - this is configurable via a 2-pin jumper connector, it can be disconnected if PB7 (reset) is to be used for regular I/O.
    • PA7 has an LED and current-limiting resistor connected to VCC (set the PB7 low to illuminate) - this is also disconnectable via a 2-pin jumper.
    • PA6 has a momentary push-button switch that can be used to pull the pin low - this is also disconnectable via a 2-pin jumper.
    • Both Port A & Port B have a 10-pin header (8 port pins, plus VCC & GND).
  6. And finally, a 6-pin header for in-system programming. I use either Atmel’s STK500 or AVRISP for programming via this port.

Schematic - plaything.sch (in ExpressSCH format) or playthingSchematic.pdf.

PCB Layout - plaything.pcb (in ExpressPCB format) or playthingPCB.gif

Photos

My first exceedingly poor experience transferring toner onto copper with Blue Press-n-Peel…

Another shot of the failure, including the Blue stuff…

Then I tried Staples Photo Paper, which was outstanding, and here I am soaking to remove all of the paper. The toothbrush helped speed the process. I scrubbed as hard as I could and there was no damage to the toner…

A close-up of some paper remaining to be removed…

Sweet looking board with toner transferred in beautiful detail and all traces perfect with no paper remaining…

The board descends into the murky depths of Ferric Chloride…

After etching is complete, and with the toner still on the board. You can see at the top a circle I drew with resist ink (aka, industrial strength sharpie marker) to test out how the marker would work. At the left you can see a trace that came out crappy so I touched it up with marker.

Final board after copper was etched and toner was removed with Acetone…

Complete board with components & battery & Atmel AVRISP, top view…

Complete board with soldering done, bottom view…

Nice view of the final board…