John:

Do you know if the 5DX machine can pick up something like this?
I am looking for other non-destructive test method to validate the
finding.

Also how and what I should check for the BGA substrate finish? According
to the process engineer oversea, the components they used ( they still
have un-used parts in stock) appear be in normal condition.  With the
solder ball already mounted to the BGA substrate, how should the
inspection be carried out? 

Sorry to keep asking question, but I am not familiar with the IC
fabrication process. The part is ROHS btw. 

Thanks
Rudolph 




-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke
Sent: Friday, September 15, 2006 11:43 AM
To: [log in to unmask]
Subject: Re: [TN] Need help on a Dye & Pry test result

AAAAAAAAAAAAAAAAAArggggggggggghhhhhhhhhhhhhhhh

It depends............

BUT from what you describe I would check the finish on the BGA
substrate, I
have seen this a few times on enig BGA substrates caused by stress in
cooling down from reflow temperatures.

The reason for the corners is maximum stress due to longest length on
diagonal.

John

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rudolph yu
Sent: Friday, September 15, 2006 11:22 AM
To: [log in to unmask]
Subject: [TN] Need help on a Dye & Pry test result

Recently I asked an outside lab to perform the dye & pry test on couple
failure assemblies. The heatsink was not removed from the PBGA prior to
the
dye application.

According to  the result and pictures,  the corner pads of the BGA
package
from both units were covered by the dye completely .  An indication that
a
seperation was formed between the BGA package's pads and its original
solder
balls at that one corner after the SMT process.

Have anyone of you experienced this kind of defects in the past and what
could be the root cause of this phenomena?  ( Poor plating from  the IC
manufacturer? SMT reflow profile? PCB warpage? )

I have been in the industry for 10 years and have never seen thing like
this.  Is it common??

Thanks
Ryu

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