Guenter,

the metallurgy should be OK under what conditions: SnPb soldering temperatures (210C to 220C), lead-free soldering temperatures (around 240C), or does not matter?

Besides, I have heard of another beast out there: BGAs with mixed solder balls (part of the balls are SnPb and the rest Pb-free). What can we expect from these ones?

Thanks,
Ioan

> -----Original Message-----
> From: Leadfree [SMTP:[log in to unmask]] On Behalf Of Guenter Grossmann
> Sent: Friday, November 18, 2005 8:37 AM
> To:   [log in to unmask]
> Subject:      [LF] Antw: [LF] Mixed processes and components
> 
> We published a characterisation study in Soldering and Surface Mount Technology Vol17  about LF BGAs soldered with SnPb. Well I stated that from the metallurgy side i didn't see any reason why this shouldn't work. Looking at the presentation of David (beautiful pictures by the way) I am glad to see that the rupture due to thermal cycling is not along the SnPb / LF interface. There is a rupture along the pad on the PCB.  Well, to be provocative,  somewhere the joint has to let go. Usually at the weakest point which seems to be the solder/pad interface. Does a LF BGA soldered with LF solder withstand the 2000 cycles that are mentioned as a minimum ?
> 
> Guenter
> 
> 
> EMPA
> Swiss Federal Laboratories  for Materials Testing and Research
> Centre for Reliability
> Guenter Grossmann,  Senior Engineer
> 
> 8600 Duebendorf
> Switzerland
> 
> Phone: xx41 1 823 4279
> Fax :     xx41 1 823 4054
> mail:     [log in to unmask]
> 
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