Hi Bob - yes, not have collapse would be a very bad idea. Soldering a 
lead-free BGA in a tin/lead soldering process automatically creates a 
mixed metallurgy situation which can be a solder joint integrity issue 
depending on the product use environment.  The degree of solder joint 
microstructure mixing/uniformity has a direct impact on the solder joint 
integrity. The customer's suggestion of not having solderball collapse 
would result in the tin/lead solder paste and the lead-free solderball 
being very distinct zones in the final solder joint which would be a worst 
case scenario.

Dave Hillman
Rockwell Collins
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Robert Kondner <[log in to unmask]> 
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09/25/2012 07:26 PM
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[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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