PCB etching just not working, noob needs help

Question

I am trying to DIY make a PCB at home following this tutorial.

There are some problems:

1. I could not order the stuff from the YouTube description because Tools & Materials:
   -) Photopositive PCB pack
   AliExpress: https://bit.ly/2WLOi0F this link lists only rubbish.
   Amazon: https://amzn.to/3bRbz5n I cannot order from Amazon in my country
   E-Gizmo: https://bit.ly/2ylwhNi this page does not even exist.
   What I now have is https://www.conrad.com/en/p/rademacher-vk-c-510-1-pcb-material-single-sided-35-m-photo-coating-positive-l-x-w-100-mm-x-50-mm-1-pc-s-1362869.html?searchType=SearchRedirect
2. I read somewhere that I can develop with sodium carbonate I use this in a mix of 10gram powder and 100ml water
3. I use this 25 watt UV lamp https://www.digitec.ch/de/s1/product/beamz-uv-lampe-fluoreszlampen-scheinwerfer-6051520?supplier=406802 My problems / questions:

• When I peel off the protective plastic layer of the photopositive PCB it just looks as if the PCB is a pure copper PCB while in the video there is a nice green layer on it. Am I using the wrong PCB?
• I printed the PCB with a toner printer, put oil on the PCB and laid the paper on it , then I put it under the UV lamp for 12 minutes.
  I washed away the oil with soap and put the board in my development solution but the traces don't show up
  I did this test with three boards now and none worked.
• I tested if there is continuity on the board and sometimes there is and sometimes not (depending on how I hold the multimeter probes I guess.)
• I also wanted to see (out of curiosity) if my failed boards would etch away completely and therefore I put them in my ferochlorid which is a "Eisen-III-Chlorid-Lösung 40 %." Even after 10 minutes of shaking none of the copper went away.

In the video tutorial it looked so easy to make a home made PCB, but dang it, it is absolutely not.

Answer 1

I could not order the stuff from the YouTube description

Good. Most of those are unreliable garbage sold by fly-by-night operations. Order from reliable distributors like Conrad, Digitec, ELFA/Distrelec, DigiKey.

But if you insist on AliExpress, just search for "presensitized pcb" or "positive pcb" or "photopositive pcb". Here's what came up in my search (among others): https://www.aliexpress.us/item/2251832660560851.html I have no idea if the product is any good though. You can't go wrong with BEL products. I have used them in the 80s, 90s, and 00s at home, and they always worked very well.

I cannot order from Amazon in my country

Amazon.de used to ship to Switzerland. Don't they anymore?

When I peel off the protective plastic layer of the photopositive PCB it just looks as if the PCB is a pure copper PCB

Scratch it at the corner with a screwdriver, you should hopefully remove the photopositive coating locally and expose the copper. The color of the coating doesn't need to be green. I've used several from BEL/Bungard over the years. The ones I have personally seen were light orange, dark red/orange, and purple.

I read somewhere that I can develop with sodium carbonate I use this in a mix of 10gram powder and 100ml water

Sodium carbonate Na₂CO₃? Not at all. You need sodium hydroxide, NaOH. I'm not sure of the concentration. Start with 10g/1L H₂O maybe and go from there. Read up on precautions when working with NaOH! Absolutely don't get any on your skin or in your eyes. Use goggles and suitable gloves that resist alkalis.

You shouldn't be making your own anyway. Buy the developer from Conrad, just as you did the pre-sensitized PCBs!

In the video tutorial it looked so easy to make a home made PCB, but dang it, it is absolutely not.

Once you get proper chemicals, it is really easy. And all of that is easily available in Switzerland. That's where all of my BEL supplies came from via Distrelec (it was a while ago!).

General notes:

• Do not waste entire boards. Cut out a fragment and test on it.
• Remove most unknowns first.

  • Take a small square, say 2x2cm. Cover some of it with a flat piece of metal or a coin. This way you don't worry about paper absorbing too much UV.

  • Expose it.

  • Develop in NaOH. This will let you adjust the concentration. The developing should take let's say 1 minute at room temperature with agitation (moving the board around in the developer solution with tongs). If it's too fast, the solution is too warm and/or too concentrated. Dilute it.

  • Rinse in water. The exposed half should have clear copper on it. The other half should have photoresist remaining.

  • Etch. It should go all right, leaving the originally non-exposed part of the board covered in copper.

Only then start adding complexity, step by step:

1. Instead of using a coin/piece of metal as the mask, use some black electrical tape.

2. Then move to toner on transparent sheets (laser-printable transparency sheets)

3. Then move to toner on paper + oil.

Answer 2

Sodium carbonate was the wrong solution. The right one is indeed sodium hydroxide. With it (6g sodium hydroxide to 500ml water) i could develop the board. The traces showed up after 30 seconds, were strong after 1 minute and already disappeared after 1:30. Unfortunately the traces are not as clearly visible like in the tutorial video (https://youtu.be/7wAer7a3tU4?si=RfrxQQDHV6P0IduG&t=359) because the material is different and the colors of the traces are different (not green on brown). I guess now it is only a case of finding out the right variables for the process. This is my current result.