PCB Exposure Box

date:June 10, 2010

PCB Exposure box

This summer I finaly decided to start making my own PCBs. The preferred method for making PCBs at home is photolithography. The PCBs used have a layer of photo resist, which is exposed to a source of light through a mask. The exposed areas are then removed using a special developer chemical. Lastly, the PCB is dipped into the etchant and the copper is removed from the areas unprotected by the photoresist.

The first thing I needed was a light source. I decided to build a small box for exposing my PCBs.

3D modeling

I began by creating a 3D model of the box usign Google Sketchup. This allowed me to spot any mistakes and tailor the design to suit my needs.


Bill of materials

I used the following parts to make this box:

  • Chipboard
  • Plexiglass for the window
  • Fluorescent lamp
  • Reflector from some old lamp
  • IEC socket and cable
  • Power switch
  • Latch
  • Pair of hinges
  • Sponge cloth
  • Screws, glue


Below is the picture of a test PCB. The safe limit of track width seems to be around 0.2-0.25mm. This could be influenced by the source of light. While experimenting with the timing, I got an impression that UV light could do a better job as it would allow reduced exposure times.

PCB test

Track widths from top to bottom are:

  1. 1.27mm
  2. 0.64mm
  3. 0.38mm
  4. 0.25mm
  5. 0.20mm
  6. 0.15mm
  7. 0.10mm

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