Plating via without chemicals

Question

In my lab we can mill and drill double sided PCBs. Holes are not plated. To create a via we usually use little copper rivets. Electroplating is out of the question because we don’t do any chemicals here. PCBs that we make here are one-offs. No production but just prototyping.

Has anybody ever tried a different ways to create a via other than the two options above? Maybe fill it with solder paste and reflow? Maybe even other ways?

Answer 1

I've seen a few ways to do this, although the copper rivet seems like the best option which I have actually not seen before.

1. Just fill the via with solder. You could hand solder it or reflow solder it.
2. Fill the via with a wire and solder on both sides.
3. Fill the via with conductive epoxy.

You will want to check continuity on both sides of the via after filling it to make sure it worked correctly. It can be a bit tricky to get right, especially if you have more than 20 vias you're trying to fill.

Answer 2

For future reference I’ll answer my own question base on my test. As @ryan mentioned I tried 4 ways:

• filling via with solder paste leads to non-conductive vias.
• filling via with solder wire leads to non-conductive vias.
• filling via with copper works fine but is not easy to do as you’ll have to solder both sides and the wire might drop out.
• filling via with copper rivet (unsoldered) gives a some conductive via but has some contact resistance (< 1 ohm).
• Filling via with copper rivet and then solder the rivet both sides is the most trustworthy way to do it with good solid connection.