[time-nuts] HP 5370B low frequency modulation

[Didier Juges]

Brooke,

Thanks Bruce for the quick response, as always.

In my business, we typically dissolve the gold by dipping the solder cup in
a hot tin pot, which is replaced regularly, before soldering the wires. This
has been blessed by the major defense contractors for military applications.

Failure to do this typically results in weakening solder joints over time,
and delayed failures, particularly when there is mechanical and/or thermal
stress applied to the joint.

Didier KO4BB

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Dr Bruce Griffiths
Sent: Monday, July 23, 2007 9:29 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] HP 5370B low frequency modulation

Brooke Clarke wrote:
> ); SAEximRunCond expanded to false
> Errors-To:
time-nuts-bounces+bruce.griffiths=xtra.co.nz+bruce.griffiths=xtra.co.nz at febo
.com
>
> Hi Didier:
>
> Would you elaborate on the comment "Gold plated connectors are a well
known 
> example."  Do you mean when soldered with Lead Tin solder instead of a
silver 
> bearing solder or something else?
>
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
> http://www.precisionclock.com
>
>
>
> Didier Juges wrote:
>   
>> ); SAEximRunCond expanded to false
>> Errors-To:
time-nuts-bounces+brooke=pacific.net+brooke=pacific.net at febo.com
>>
>> I have seen cold solder joints on thermal fuses and certain types of
>> capacitors, while the rest of the instrument was fine with no sign of
>> corrosion.
>>
>> I think it has to do with the metal used for certain component leads.
Either
>> they were never soldered well, or interface corrosion developed over
time.
>>
>> Gold plated connectors are a well known example.
>>
>> Didier KO4BB
>>     
Brooke

Gold dissolves in the solder and a gold -tin intermetallic compound is 
formed which severely reduces the joint integrity and ductility.
This can be circumvented by keeping the gold concentration in the solder 
below 4%. Tin plating over the gold before soldering is sometimes used 
to ensure this.

Bruce


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