Bob, 
The flux we use for SnPb and SAC is the same. 
However, the flux does not work well with SnBi. 
The solder looks good, but does not form a good bond to the Nickel (our
boards have NiAu finish).

We use a different flux that is, according to the supplier, formulated with
a lower activation temperature.
It does work better.

Guy


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Thursday, September 27, 2012 1:13 PM
To: [log in to unmask]
Subject: [TN] Flux Activation Temps

Hi,

 

I was looking though some paste datasheets which show a paste "Family"
available in different alloys. 

 

My Question:

 

Is a single flux formulation being used with these different alloys? It
seems so.

 

But the various melting point have a serious range. And I remember from my
college chemistry days that reaction rates double for every 10 C rise in
temp. (Is that still correct?) So I would expect fluxes to be relatively
"Inactive" al low leaded temps but then going super-fast at higher lead free
temps.

 

Can anyone clarify? Is it a real issue or hogwash-worthy.

 

Thanks,

Bob K.

 

 



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