Your industry peers that developed IPC-A-610D (listed on the
acknowledgement pages in the front) made the decision to include lead
free Hot Tear/Shrink Hole in IPC-A-610D Clause 5.2.11.

This topic had significant committee discussions and input from a number
of large EMS company participants. They provided information based on
build of millions of lead free assemblies and evaluation of the hot tear
anomalies. Their input was that they could not link any connection
failures to lead free hot tear/shrinkage cavities/shrinkage cracks,
regardless of the size of the cracks. 

This hot tear criteria was in publicly available drafts for nearly a
year and through several ballots and no other input from industry users
was provided committee review.

The 610 committee took a conservative approach in the criteria by
establishing that it is not acceptable if the bottom of the shrink hole
or hot tear is not visible or if the tear or shrink hole contacts the
lead or land.

Anyone with different data should present it to the committee for
revision consideration.


Jack Crawford, IOM
IPC Director Certification and Assembly Technology 
[log in to unmask] 
847-597-2893 
FAX  847-615-5693 
3000 Lakeside Drive, Suite 309 S
Bannockburn, IL, 60015

-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Pratap Singh
Sent: Saturday, April 30, 2005 8:43 AM
To: [log in to unmask]
Subject: Re: [LF] "New IPC Standards for Pb-free"

Dave,
What IPC has missed about Lead free solders is about time zero
'Shrinkage cavities' or shrinkage cracks. After inspecting 50 plus cards
from different products and subjecting them to thermal cycles, it is
observed that some of these shrinkage cavities/cracks grow resulting in
solder joint failures. This seems to apply mostly to pin solder joints.

Have other engineering folks similar data to share? I have not found
much information about shrinkage cavities/cracks on LF solder joints in
my search on internet. What is your experience?

--
_____________________
pratap singh
Tel./Fax: (512) 255-6820
email: [log in to unmask]
www.rampinc.com

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