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DIY PCB Manufacturing

In answer to the frequently asked question about how I make my Printed Circuit Boards (PCB's)

 I make almost professionally looking PCB's since years, the only thing I can't do by myself is the silkscreen mask.
The basic PCB material I use is presensibilized with a UV sensible lacquer (available in most electronic stores).
You can also use non presensibilized PCB material and treat it with Positiv20 spray from Kontakt Chemie. De-oxidate and de-grease the raw PCB material with steel wool and aceton. Atomise a FINE layer of Positiv20 onto the copper and let the PCB dry for 24 hours in ambient room temperature, or about an hour at a maximum of 70C (do not exceed! ). I do this in my hot air electric oven in the kitchen.
The drying MUST be done in complete darkness! After that the PCB can be used as normal presensibilized PCB.

All you need is:

 

Placement of the PCB material and slides:

 
Some more pictures of my UV-exposure unit:

The PIC16F84 based Timer:

View of the 4 UV-lamps:

Lamps powered on:

The used glassplate is "milky" to diffuse the UV-light from the lamps:

Slides in place onto the glassplate (with toner upwards):

PCB material in place onto the slides, ready to be exposed:

 

To determine the "best" exposure time for the UV exposure I did the following:

  1. Take a slide with a PCB layout.
  2. Put a piece of cardboard on 9/10 of the surface.
  3. Expose for 1 minute.
  4. Move the cardboard to 8/10 of the surface.
  5. Expose for 1 more minute.
  6. Move the cardboard to 7/10 of the surface.
  7. Expose for 1 more minute. And so on...
  8. Develop the exposed PCB.
  9. Examine the results and decide for the best exposure time.

In my case the best exposure time is between 5 and 6 minutes, so I decided for 5min 30secs. I didn't fail any PCB since then...

 

Some finished PCB's:
Since the copper is still covered by the UV lacquer it's protected against oxidation and moisture, and also the lacquer acts as a (not very good) solder flux when soldering the components to the PCB.
I prefer to remove the lacquer with aceton (ask your wife or girlfriend...), solder the components, and then treat the solder side with a spray varnish (I use transparent Plastic Spray 70 from Kontakt Chemie and green varnish from KF).

 

A few weeks ago I bought also a new TBM220 mini bench drill machine from Proxxon for about 250 Euro.
Not cheap but very precise:

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