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November 2005

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Subject:
From:
WTSJ-Willis Tam <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, WTSJ-Willis Tam <[log in to unmask]>
Date:
Mon, 14 Nov 2005 08:24:12 +0800
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Jeffrey,



Thanks for your suggestion, but I think we are going to build with selective

OSP. 





Willis Tam



-----原始邮件-----

发件人: TechNet [mailto:[log in to unmask]]代表 Jeffrey Bush

发送时间: 2005年11月11日 21:15

收件人: [log in to unmask]

主题: Re: [TN] urgent issue BGA fall out





I would suggest testing a series of builds with Immersion Silver.





Jeffrey Bush



Director, Quality Assurance and Technical Support



76 Technology Drive - POB 1890



      Brattleboro, Vermont 05302-1890



           Tel. 802.257.4571.21 Fax. 802.257.0011



                 [log in to unmask]





                      http://www.vtcircuits.com  



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Ofer Cohen

Sent: Friday, November 11, 2005 4:38 AM

To: [log in to unmask]

Subject: Re: [TN] urgent issue BGA fall out



Willis,

Welcome to the black group of the black pads. We've experienced the

phenomena lately. The balls were left on the PCB, while the BGA,

leg-less, fell off after the soldering. Failure analysis showed clearly

balck pads phenomena on the BGA substrate.



Ofer Cohen

Siemens



> -----Original Message-----

> From: TechNet [mailto:[log in to unmask]] On Behalf Of WTSJ-Willis Tam

> Sent: Friday, November 11, 2005 08:31

> 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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