The problem you describe is not uncommon with manual soldering of Au
plated pins/leads.
The only reliable method I know of is to pre tin the terminals.
Remove the Au loaded solder from the terminals and then solder to the
PCB.
I am assuming that the terminals are meant to be soldered and are not
connector terminals or meant to be mechanically attached (with screw or
rivet).
The amount of Au on the terminal and SnPb applied will affect the
characteristic of the  AuSn alloy formation which is brittle (Dendritic
Encyclic Gold Tin alloy).
A little more Gold, a little less Tin lead.....BAD JOINT!
A little less Gold, a little more Tin Lead....NOT AS BAD JOINT!
I would expect that all of the joints are risky.
The 20% found are the gross problem.
The other 80% may be little problems just ticking away..
Good Luck.


> -----Original Message-----
> From: Bruce Robertson [SMTP:[log in to unmask]]
> Sent: Thursday, June 04, 1998 6:43 PM
> To:   [log in to unmask]
> Subject:      [TN] Soldering to Gold Plated Components
>
> Hello,
>
> We have problems with manual soldering to gold plated components to a
> PCB (auxilliary connector pins and battery contacts). In approx 20% of
> the joints the bond between the solder and the gold plating is of
> unacceptable strength, with some having  failed in service under small
> loads.
> The plating is gold over  brass (pins) or berrilium copper (contacts).
> We are using a 63/37 tin lead solder at the moment. As far as I can
> see
> there is good wetting of the gold, and the serface of the solidified
> solder
> is fairly bright. I have an idea that there may be a brittle
> intermetallic being
> formed with the gold by either the tin or the lead. Does anybody know
> what the story is with Gold intermetallics?? What would be the
> solution
> to this? Will using a solder with 2% silver stop the intermetallic
> formation
> at all?
> Any information on soldering to Gold would be much appreciated.
>
> Regards
>
> Bruce Robertson
> Production Engineer
> Tait Electronics Ltd
> New Zealand
>
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