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Author: Subject: new way of PCB via plating
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[*] posted on 20-11-2017 at 16:02
new way of PCB via plating


In this thread I'm reporting the success of a new way of plating vias in PCBs.

For those not into electronics, the goal is to chemically deposit copper into holes of a printed circuit board to make them conductive. The hole walls are made of fiberglass, which is non conductive. Electrolytic plating is thus not possible until a way is found to deposit a first conductive layer on the hole walls.

Many ways have been proposed, including a solution using calcium hypophosphite, which is a controlled substance, and a solution using expensive palladium chloride activator and formaldehyde. This link details the known methods in greater detail

http://www.instructables.com/id/Inexpensive-method-of-indust...

Quite a while ago NurdRage has shown how to make a silver conductive ink using far less exotic chemicals, and I wondered if it could be used to deposit the first conductive layer on the PCB holes.

Today I finally tried, and it worked.

After drilling a few holes, immersing the board in a sodium hydroxide solution for cleaning, applying the conductive ink to the holes and heating the board for a few minutes, the hole sides were covered in grey silver, which looked promising.

2.jpg - 106kB

The next step was to try electroplating copper and see if the silver coating works. For this I used the formula shown in a comment to the instructables link:
100mL water
20g CuSO4*5H2O
6g H2SO4
0.1g Polyethylene glycol
1 drop of copper chloride solution
and immersed the PCB and a copper electrode. I plated for 50 minutes at 0.5A, around 250mA/cm^2.

3.jpg - 88kB

The holes were covered in copper, and the resistance is quite low, less than 0.1 ohm.

Bottom side
4.jpg - 165kB

Top side with plated copper (note that I used a single sided PCB just to more easily test the conductivity of each hole)
5.jpg - 75kB
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[*] posted on 20-11-2017 at 18:11


Did you weigh the pcb before and after to determine how much copper was plated out?



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[*] posted on 21-11-2017 at 09:01


Nice work !

It will probably be easier with a double-sided PCB.




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[*] posted on 21-11-2017 at 15:52


I have not weighed the pcb unfortunately, but I'll be doing more experiments in the next days.
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