Usedd components from another batch : black pads is a batch-dependent problem. Further, we are in contact with the compoent vendor to change the finish of the substrate.
Ofer Cohen
Siemens
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of WTSJ-Willis Tam
> Sent: Friday, November 11, 2005 11:47
> To: [log in to unmask]
> Subject: [TN] ??: [TN] urgent issue BGA fall out
>
> Hi Ofer,
>
> What did you do to fix the issue?
>
> Thanks
> Willis Tam
>
> -----原始邮件-----
> 发件人: TechNet [mailto:[log in to unmask]]代表 Ofer Cohen
> 发送时间: 2005年11月11日 17:38
> 收件人: [log in to unmask]
> 主题: 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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