I was at the AIA-PERM meeting this past week. There there were no negative comments on the method of reballing 63/37 (replacing RoHS balls).
Many MIL/aerospace products must be reballed as lead-free reliability cannot be calculated.
Reballing (with the proper inspection techniques and removal process (air knife is one technique) is an acceptable process.
See http://www.acqp2.nasa.gov/LFS%20Reliability/Premier%20BGA%20Presentation%207-28-08.pdf
Also http://www.smta.org/knowledge/proceedings_abstract.cfm?PROC_ID=2484
Title : LEAD FREE TO SnPb BGA REBALLING PROCESS AND RELIABILITY
Author : William Beair and William Vuono
Author Company : Raytheon Company
Date : 08/17/2008 Conference : SMTA International
Abstract : As the electronics industry continues to transition to a lead free environment, component suppliers are phasing out the standard SnPb alloy process for BGA balls and termination surface finishes. High reliability products that require comprehensive product qualification may not readily transition to a “mixed” system solution (lead free components and tin-lead solder joints). As an alternative, some customers are “reballing”, or replacing lead free BGA balls with SnPb alloy balls. However, the reliability of the reballed devices is not known.
The reballing process has been characterized as to solder composition, temperature profiles required for successful reflow, shear strength of resultant solder joints, solder ball size/consistency and component physical damage resulting from reballing. Reliability has been assessed by thermal cycling, and compared to that of conventional SnPb components.
Bob Landman
H&L Instruments, LLC
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Thursday, June 10, 2010 2:36 PM
To: [log in to unmask]
Subject: Re: [TN] rohs, BGAs & assembly
Hi Paul,
I have seen no evidence that reballing produces assemblies of lesser reliability.
Werner
-----Original Message-----
From: Paul Edwards <[log in to unmask]>
To: [log in to unmask]
Sent: Thu, Jun 10, 2010 1:20 pm
Subject: Re: [TN] rohs, BGAs & assembly
I Agree with Nigel...
If the time-temperature product is high enough to produce mixing the bulk solder
joint should be good but not perfect...
However it is all a compromise anyway...If you can get only RoHS balls on BGAs
and you need to use 6337 for the connection, the process of reballing will
introduce undetectable additional defect sites in the component that will lead
to decreased reliability of the final product and you will loose the reliability
edge you are attempting to gain...
Paul
Paul Edwards
Surface Art Engineering
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Nigel Burtt
Sent: Thursday, June 10, 2010 8:33 AM
To: [log in to unmask]
Subject: Re: [TN] rohs, BGAs & assembly
Will be OK providing your assembly can withstand high enough reflow
temperature to get the RoHS balls to melt. usually problem is not with the
BGA, but with other parts that won't like to get that hot!
NPL in the UK have public domain technical papers on this which you can
download from their website
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