I have tried it once on a preprod board.. Using solder to connect
the wire is very difficult because the copper layer is too thin and oxidizes
very quickly,  and to come up with a very small tip to reach down there and
to supply enough heat to melt the solder is not easy.. The following worked
for me. Use AWG 32 wire for transformers, very thin insulation. Strip about
0.1 " from the end.  Tin the tip and allow extra solder to build up at the
end. Drill down to allow the wire to fit. Use a cold solder paste to bond
the via contact to the wire.. Bend the wire flat to the board as it comes of
the via and bond or tape it to the board. The use of a microscope to drill
and to bond the wire may be helpful.
        Good luck
        Ramon

> -----Original Message-----
> From: Carlr Ray [SMTP:[log in to unmask]]
> Sent: Thursday, January 22, 2004 1:42 PM
> To:   [log in to unmask]
> Subject:      [TN] Blind Via Rework!!!
>
> Hi All,
>  I have the unfortunate task of reworking some units from a customer.
> The rework is unusual to say the least. We have to drill down to a blind
> via, add a wire and route to another via on the surface of the pcb.
>  Has anyone ever done this before? What specifications are there that
> cover this type of rework? I could not find anything in IPC. Any
> information would be greatly appreciated!
>
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