alan00463 wrote:
> --- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
> wrote:
>
>>Sounds kind of odd to want to make an entire pre etched PCB, back to
>>being conductive over its entire surface. Why not skip the etching
>
> step altogether so you have fully copper coated fiber glass material ?
>
>>Your question does not read as wanting to selectively coat the
>
> copper tracks with a conductive material since copper is already quite
> conductive.
>
>>You post is also contradictory by mentioning the use of polyurethane
>
> as being an option, becuase this is not a electrically conductive.
>
>
>>Maybe your better to explain what your goal is.
>
>
> Sure, Adam. I want to etch the copper artwork ∗before∗ I have all
> the components to populate the board with. So that is why I wanted
> some substance to cover the copper traces immediately after etching so
> they don't become oxidized. I was thinking it would be easier to
> solder the (through-hole) components in place if I used an
> electrically conductive material. Or should I use something I can
> later clean off the copper traces with solder flux when ready to
> populate the board?
>
> Anyway, I did some research this afternoon and discovered that of the
> conductive substances nickel, tin, lead, and silver.
> Nickel is a poor conductor of electricity.
> Lead is a poison as well as a poor conductor.
> Tin is also a poor conductor of electricity.
> That leaves silver, which is an excellent conductor. Stefan, you
> are right as usual. Thanks, Stefan for taking time to answer me.
>
> And yes, I realize it would have been necessary to interconnect all
> the copper traces in order to electroplate a metal onto them. That's
> an extra step that will be nice to avoid.
>
> Thanks to all who answered,
> Alan
>
Plating the copper traces with another metal would cause no measurable
increase in resistance, between an connection interface consisting of
solder/nickel/copper and that of solder/copper. Obviously you know that
solder has 12? times more resistance than copper!
Protective plating finishes are typically no more than a few microns
thick. Would you scrape of the tin from tin plated copper wires of
resistor and IC leads in order to decrease resistance ?
There are a few ways to avoid copper oxides. Simplest is to use a common
PCB lacquer that is sprayed on. this lacquer can be soldered through. I
use it all the time, and think its great.
Another approach is to tin plate the copper, with an electroless tin
formula, but these are expensive.
There is also electroless nickel formulations but difficult to get hold
of and probably even more difficult to make yourself. I've never made
any electroless solutions. Electroless plating is a solution that
deposits metal onto a metal without applying external electricity.
Electroless plating has ability to plate on its own kind so the metal
can build up continuously provided there is a supply of fresh metal
ions. Search google for electroless
You really don't have a choice to use anything else other than
electroless plating since it will be unpractical to connect each copper
trace to a power supply for a electrolytic plating bath. Electrolytic
plating is inherently simpler, cheaper and more forgiving.
Adam