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November 2005

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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, 11 Nov 2005 08:37:42 -0800
Content-Type:
text/plain
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text/plain (113 lines)
It is possible that you have a brittle interface at the Ball to BGA carrier
interface - you will need to get some photographs of the issue and put them
up on Steve's web site for people to comment on the issue.

Kind regards,

John Burke
------------------------------------
Avanex
John Burke
Senior Manager RoHS Compliance
[log in to unmask]
40919 Encyclopedia Circle
Fremont
CA 94538
tel: 510 897 4250
fax: 510 979 0189
mobile: 510 676 6312
------------------------------------


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of WTSJ-Willis Tam
Sent: Thursday, November 10, 2005 10:31 PM
To: [log in to unmask]
Subject: [TN] urgent issue BGA fall out
Importance: High


> Dear All,
>
> Recently, we found a very strange defect with the BGA IC.
>
> Here's our process flow:  SMT---> De-panel (by V-cut machine)--->
> Functional test--->final inspection
>
> We found around 10 pcs BGA falling out either at the process of de-panel
or
> functional test, defect rate less than 0.1%. The defect only happened in 2
> days, It's very strange, all the solder balls adhere to PCB. there's no
> solder ball adhere to the BGA substrate.
>
> Investigations from our side:
> 1. We have been built the same product since April 2004. no issue before.
> 2. Since May 2005, the SMT process was converted to RoHS, BGA also has
been
> changed to green type since then, monthly output around 200K.
> 3. The BGAs were 100% baked under 110 degreeC for 24 hrs before SMT.
> 4. We use Loctite LF318 solder paste for SMT, the time between 70 degreeC
> to peak 245 degreec is around 250 seconds.
> 5. The BGA only subjected to 1 time reflow (only 1 side with components)
> 6, We have reflow fixture to support the board during reflow. there's no
> warpage issue.
> 7, Use Vcut machine to separate the units from a 6 up-panel PCB, no extra
> stress to the board.
> 8. Use pogo pin to make connection for functional test fixture, no extra
> stress.
>
> Information of BGA.
> 1. It's a solder mask defined substrate. with ENIG surface finishes.
> 2. 0.8mm pitch, pad size 0.35mm.
> 3. IC supplier apply solder ball with flux only, without solder paste.
>
> Would anybody give me some advices, what shall be the most possible root
> cause? it's a BGA IC issue or a SMT process issue? How to improve?
>
>
> Thanks
> Willis Tam
>
>
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>

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