The PCB:

A scrap piece of 5+ year old UV sensitive PCB. The sticky black residue on the PCB is the clue from the protective foil.

The mask:

Transparent foil for laser printers. Printed on Samsung CLP-320 in greyscale mode. Single layer.

The traces:

  1. 0,1 mm with the gap of 0,1 mm
  2. 0,1 mm with the gap of 0,2 mm
  3. 0,2 mm with the gap of 0,2 mm
  4. 0,2 mm with the gap of 0,3 mm
  5. 0,2 mm with the gap of 0,4 mm
  6. 0,3 mm with the gap of 0,2 mm
  7. 0,3 mm with the gap of 0,3 mm
  8. 0,2 mm with the gap of 0,6 mm

The rest of the PCB will be used for the rectifier circuit.

The UV cycle:

  1. preheat lamps for 3 minutes
  2. exposure for 6 minutes

The developer:

DP 50 (probably 🙂 @ 20°C, no agitation

Rinse

Use running water.

After the developing, traces of 0,1/0,1 mm are seen as solid.

20150415_211149_cropBut not at the larger scale:

20150415_211158_crop

Camera
LG-D40
Focal Length
3.2mm
Aperture
f/2.4
Exposure
1/20s
ISO
200

Seem like PCB got some unintentional light on the upper left corner?

Etcher:

Sodium persulfate @ 25°C, constant manual agitation. Too cold, thus took too long to etch the copper layer.

After the etch bath:

Definitely there is a problem with the transparent exposure pad. Scratches are all over the upper traces.

20150416_002446_cropped

Camera
LG-D40
Focal Length
3.2mm
Aperture
f/2.4
Exposure
1/100s
ISO
100
Camera
LG-D40
Focal Length
3.2mm
Aperture
f/2.4
Exposure
1/100s
ISO
100
  1. traces of 0,1 / 0,1 mm are not continuous and too narrow;
  2. traces of 0,1 / 0,2 mm are not continuous and too narrow;
  3. traces of 0,2 / 0,2 mm are too narrow;
  4. traces of 0,2 / 0,3 mm are too narrow but almost perfect;
  5. traces of 0,2 / 0,4 mm are too narrow;
  6. traces of 0,3 / 0,2 mm are too narrow but of acceptable quality;
  7. traces of 0,3 / 0,3 mm are slightly “washed out” but of acceptable quality;
  8. traces of 0,3 / 0,6 mm are of different widths and slightly “washed out”;

Rants:

  1. Get rid of the current exposure plate.
  2. Preheat the developer up to 20-25°C and keep the temperature constant;
  3. Preheat the etcher up to 40-42°C and keep the temperature constant. Are there any indirect heaters available?
  4. Agitate the etcher. Need to search for magnetically coupled plastic pump on the eBay.
  5. Place a mate UV unifying media between the lamps and the PCB.
  6. Clean the PCB after removing the foil. The glue stick everywhere …
  7. Traces of 0,2/0,1 mm are worth trying. Expect them to appear as 0,15/0,15 mm on the PCB. For this i will need constant and turbulent agitation system. Laminar flow will probably overetch the parallel traces.