Hi Scott!

The difference is that ceramic BGA's usually have PB90/SN10 spheres
(liquidous is WAY up there around 300 C.), they are not designed to
collapse, but to stay solid and have the connection made only from the
solder paste that is printed. The same is true for column grid arrays.

The lead free spheres ARE designed to collapse, but won't do so unless
you are at a high enough temp. You are right about reliabilty the
"backward compatibility" of lead free BGA's from everything I've read.
One such paper is:

http://www.leadfreemagazine.com/pages/pdf/Clech_APEX2004_Paper-final.pdf

Another paper I've read concludes that reflowing at the higher temps
required to ensure a "homogenous" solder joint using 63/37 paste and a
lead free solder sphere will result in more voiding:

http://www.emeraldinsight.com/Insight/ViewContentServlet?Filename=Publis
hed/EmeraldFullTextArticle/Articles/2190170202.html

-Steve Gregory-



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Scott Lefebvre
Sent: Monday, June 19, 2006 12:19 PM
To: [log in to unmask]
Subject: [TN] Ceramic BGA High Temp Ball

After reading all the articles on Lead-Free backwards capability with
Lead-Free BGA's I'm confused.   It is stated that Lead-Free BGA's are
not backwards compatible because of there high temp solder balls not
becoming liquidus when using SnPb solder, the interconnect is considered
too brittle and prone to cracking.  Isn't this true for CBGA's having
the same issue?  Why was it acceptable for CBGA's with SnPb solder but
not for PBGA's?

 

Your thought's 

 

 

 

Scott Lefebvre 


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