Hi Mumtaz,
Each bond results in slightly different deformation geometry of the wire which results in different degrees of stress concentration—thus, differences in the pull strength of these geometries.
What you really need to worry about is where the loading in product is coming from, what is the magnitude of the loading and whether it is steady-state or cyclic loading.

 You may want to look in the upcoming December issue of Global SMT & Packaging magazine, where I deal with wire bond fatigue in my reliability column.


 
Werner
Upcoming workshops:
November 2 & 9, SMTA Webtorial,
     “Fundamentals in Solder Joint Reliability”
December 7 & 14, SMTA Webtorial,
     “Acceleration Models, Accelerated Reliability Tests and ScreeningProcedures”

 

-----Original Message-----
From: Mumtaz Bora <[log in to unmask]>
To: [log in to unmask]
Sent: Fri, Nov 12, 2010 9:15 pm
Subject: [TN] Wire Bond Pull failures


Hello TechNetters,

 

I have some wirebonds on a Hi -Rel package that pulled below 2.0 gm

minimum  per Mil -Std -883. I have taken some SEM images of failed and

good bonds. Customer has a concern with plane of fracture of the failed

bonds even though it is break at "neck" . . It is Aluminum wire/to

Aluminum bond pad wedge bonded ultrasonically and aluminum wire to gold

plated post also bonded ultrasonic. Wire pull is post seal. I have

uploaded the file of images on the TechNet groupsite .I will appreciate

some feedback from wirebonding experts on the forum.

 

 http://ipc-technet.groupsite.com/main/summary

<http://ipc-technet.groupsite.com/main/summary> 



Thank-you, Mumtaz



Mumtaz Bora



Senior Packaging Engineer



Peregrine Semiconductor



9380 Carroll Park Drive



San Diego, CA 92121



858-795-0112-direct



858-731-9499 -fax



[log in to unmask]



 



 



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