Using silver loaded paint for vias?

Has anyone here tried using silver loaded conductive paint for vias on home made PCBs?

This one comes in pen form and the datasheet says it's solderable so you should be able to use it on holes with pads on both sides of the board where components need to be fitted.

It might be a neater option than soldering pieces of tinned wire to both sides of the board.

The datasheet says there's enough in one pen to do 100 feet of trace which is 30m so you should be able to do 1000s of vias with one pen. This means it probably isn't as expensive as the price tag might suggest.

**broken link removed**

It should work, but the trick may be getting it through the hole to make good contact on both sides without having to use a big glob to fill the hole. It would depend upon the diameter and length of the pen tip, and the size of your vias.

The pen tip is 1mm which should be able to plate a 1mm hole given that drill bits always cut slightly larger holes than they're specified to.

Is the tip long enough to go a least half-way through a typical pcb?

Found this

Curing: Tack-free in 3 to 5 minutes at room
temperature. Achieves electrical conductivity
within 30 minutes. Heat cure for 5 minutes at 250
to 300°F (120 to 150°C) for maximum conductivity,
durability and chemical resistance.

Soldering: Low temperature soldering is possible
to the heat-cured silver conductive traces if done at
350°F (177°C) for <5 seconds.

Click to expand...

Note: Solder iron tip temperatures are most commonly between 315-371°C (600-700°F) for Sn63Pb37 and
Sn62Pb36Ag02 alloys.

It looks like we have to use a low temp solder. SnIn20Ag2.8 may work but I have not found a source for it.

The pen comes in two tip sizes.
CW2200STP (standard tip)
CW2200MTP (micro tip)
RS and Mouser have them both.

I did not see the info on tip widths.

Currently I am drilling all holes with a .025 inch bit which is about .6 mm. Maybe it is possible to apply by coating a wire with the ink and dragging it through the hole.

I posted a similar posting on the yahoo group Homebrew_PCBs . They may have more info on this.

That special low temperature solder sounds expensive.

You can get cheaper silver paint which is not solderable. Another option would be to just use the silver paint for vias which don't need to be soldered to. This will still save a lot of messing around with soldering pieces of tinned copper.

A while back I found this website where they describe how to get true plated-through holes by using the silver-print ink to first make the via conductive, then actually plating over that with copper. Interesting read, but it seems like a load of work (and possibly money). I would be interested to see just how high quality of a board a hobbyist could produce in his or her basement like this...

Jeff

So far the methods I use are quick and produce good results.

That is a good example of what I do not want to mess with. At some point it would be better to have them made.