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September 2006

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Subject:
From:
John Burke <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, John Burke <[log in to unmask]>
Date:
Fri, 15 Sep 2006 14:33:13 -0700
Content-Type:
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text/plain (142 lines)
I can confirm 5dx is unlikely to find it as it is coplanar. I have never had
success with 5DX for this defect. The only way I have found these by testing
is to power up and vibrate..............

BGA substrate finish.........ask the manufacturer what his board finish is
on the substrate, typically this will be a 2 or 4 layer substrate, the
finish will generally be enig or entec.

I am betting you have enig. If you want to check the shear force of the ball
from the BGA you can get this done at Dage here in Fremont (bay area)I
believe you are on Milpitas blvd just around the corner from my
house................Call Evstatin Krastev at Dage 510 683 3930
[log in to unmask] and tell him you want to use the high speed shear
tester.

You will need a brand new BGA to wreck to run the trials.



John

-----Original Message-----
From: Yu, Rudolph [mailto:[log in to unmask]]
Sent: Friday, September 15, 2006 1:46 PM
To: TechNet E-Mail Forum; John Burke
Subject: RE: [TN] Need help on a Dye & Pry test result

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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