Bob,

Not only is it a bad idea based on the reduced reliability of the solder joint, it's also practically infeasible. As soon as the SnPb solder paste melts, it will start incorporating the Pb-free ball into the melt, so regardless of the reflow profile, there will be some, if not complete 'collapse' of the Pb-free ball.


Ben

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Tuesday, September 25, 2012 8:26 PM
To: [log in to unmask]
Subject: EXTERNAL: [TN] Leaded Paste and Lead Free BGAs - Do they mix?

Hi,

 

I have a customer using leaded paste with lead free BGAs. I think they want to have the balls NOT collapse for better optical inspection.

 

Sounds like a really bad idea to me but I have no explanation where I can say as why.

 

Can anyone make suggestions either way?

 

Thanks,

Bob K.



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