Solder has a huge surface tension, which tends to pull it onto a
blob, have you seen how if you put too much paste it all pulls back
into the pad or if you put a line of solder paste across some pins it
all pulls back so there is only solder on the pins, the same thing
will happen with solder in a hole with no metal in it. It has nothing
to adhere to so surface tension pulls on it and away from the hole to
the trace where the solder is adhering.
One does not want the holes plugged up that is why a vacuum cleaner
is used to only leave a thin layer stuck on the walls, so it must be
either an exotic alloy paste or a conductor with some kind of glue
like binder to make it stick to the walls. I'm thinking that a silver
compound like the one used to repair traces might work.
At 06:33 AM 2/8/2014, you wrote:
>
>
>On Sat, 8 Feb 2014 13:05:18 +0100, you wrote:
>
> >On Sat, Feb 8, 2014 at 12:21 PM, Cecil Bayona <cbayona@...> wrote:
> >>
> >> I would think that solder paste once heated would bead away from the
> >> insulated whole just like it does on the top of the board.
> >
> >I do not know that this is true. Have you tried? Maybe it being a hole
> >makes the difference?
>
>Hasn't seemed to work when I've tried it. I normally use either
>soldered eyelets or thin wire and solder. Solder "wets" metals to
>adhere, there's nothing in there to adhere to.
> >
> >> You would need something that would really stick to the fiberglass
> >> and not let go, like conducting epoxy
> >
> >I guess following your logic it might also be a different alloy. I
> >wonder what this does to the stability of the solder in the soldered
> >assembly.
> >
>
>I think that it's a conductive epoxy, so there's a limit to how good a
>conductor it is. People have used windshield heating element repair
>compound, no idea of how well it works.
>
>I've seen graphite used, but that's before copper plating.
>
>Harvey
>
> >D.
>
--
Cecil - k5nwa
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