It depends on their capability to control the reflow profile. If they can control the TAST such that they can solder to the lead-free solder balls without having any of them go into liquidus, then it may be able to be done.
Are you sure they are not speaking of Pb90 solder balls? It is a common practice to use Sn63 to solder to Pb90.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Tuesday, September 25, 2012 7:26 PM
To: [log in to unmask]
Subject: [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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