Please copy me when you send the pictures. I never realized that BGA heatsinks could cause these issues. I figures the experts that designed BGA heatsinks made sure they wouldn't decrease reliability. As a contract assembler we would assume the failed BGA was from either the BGA mfg or something in our process and therefore repair as the board under warrantee.
-------------- Original message --------------
From: Victor Hernandez <[log in to unmask]>
> Werner,
>
> Could I also get copied on the moiré pictures? Supported data as such is
> always interesting.
>
> vic.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner engelmaier
> Sent: Friday, December 05, 2008 2:11 PM
> To: [log in to unmask]
> Subject: Re: [TN] ??: Re: [TN] BGA soldering open issue
>
>
> Hi Arnaud,
> A BGA with an attached heatsink is causing the BGA to be thermally
> unsymmetrical--and you get warpage by the 'bimetallic strip' effect.
> I show some nice shadow moire pictures [courtesy Advanced Semiconductor
> Engineering Inc.] showing 9 mils of warpage fro 20 to 240°C in my workshops.
>
> Werner
>
>
>
>
>
>
>
> -----Original Message-----
> From: Arnaud Grivon
> To: Werner engelmaier
> Sent: Fri, 5 Dec 2008 9:21 am
> Subject: Re: [TN] 答复: Re: [TN] BGA soldering open issue
>
>
>
>
>
>
>
>
>
> Hello Werner,
>
>
> Could you please elaborate on your posting stating that BGAs with
> heatsinks are more prone to warpage during assembly?
>
> Are you thinking of cavity down BGA (such as SBGA), FC-PBGA, or...?
>
> Would you have any publication/article to share?
>
> I thank you in advance for your support.
>
> Best regards,
>
>
> Arnaud Grivon
>
>
> Werner engelmaier a écrit :
>
> > Nee hao Hechong,
>
> > BGAs with heatsinks have been shown to warp and thus loading the SJs in
> tension.
>
> >
>
> > Werner
>
> >
>
> >
>
> >
> >
>
> >
>
> >
> >
>
> > -----Original Message-----
>
> > From: Cong He
>
> > To: [log in to unmask]
>
> > Sent: Thu, 4 Dec 2008 10:08 pm
>
> > Subject: [TN] 答复: Re: [TN] BGA soldering open issue
>
> >
>
> >
>
> >
>
> >
>
> >
>
> >
>
> >
>
> >
>
> >
>
> >
>
> > surface fin
> ish is hasl.
> >
>
> > after analysed parts of the board, we found some balls of the bga rupture.
>
> > Could it be the material of the ball(BGA) cause the problem?
>
> >
>
> > by the way, there is a heatsink which is double size lager than the chip
> > stick on it without other fixture.
>
> > will the heatsink be the reason?
>
> >
>
> >
>
> >
>
> >
>
> >
>
> >
>
> > Hechong
>
> >
>
> >
>
> >
>
> >
>
> >
>
> > "Wenger, George M."
> > 发件人: TechNet
>
> > 2008-12-05 10:57
>
> > 请答复 给
>
> > TechNet E-Mail Forum ; 请答复 给
>
> > "Wenger, George M."
>
> >
>
> >
>
> > 收件人
>
> > [log in to unmask]
>
> > 抄送
>
> >
>
> > 主题
>
> > Re: [TN] BGA soldering open issue
>
> >
>
> >
>
> >
>
> >
>
> >
>
> >
>
> > What is the surface finish on your PCBA?
>
> >
>
> >
>
> >
>
> > Necong,
>
> >
>
> > What is the surface finish on your PCBA?
>
> >
>
> > Regards,
>
> > George
>
> > George M. Wenger
>
> > Andrew Wireless Solutions
>
> > Senior Principal FMA / Reliability Engineer
>
> > 40 Technology Drive, Warren, NJ 07059
>
> > (908) 546-4531 [Office] (732) 309-8964 [Cell]
>
> > [log in to unmask]
>
> >
> >
>
> > -----Original Message-----
>
> > From
> : TechNet [mailto:[log in to unmask]] On Behalf Of Cong He
>
> > Sent: Thursday, December 04, 2008 9:09 PM
>
> > To: [log in to unmask]
>
> > Subject: [TN] BGA soldering ope
>
> > n issue
>
> >
>
> > dear all:
>
> >
>
> > I am facing a problem of bga soldering.
>
> >
>
> > when the board have just soldered ,it pass all test.
>
> > But after sometime, maybe for a few weeks,
>
> > some of the bga balls opened. the function became normal if i press the
> > chip on the top side.
>
> >
>
> > It seems that the pcb didn't warp much,it seems even no warp at all.
>
> > Does any of you know why? And how to improve?
> >
>
> >
>
> >
>
> >
>
> >
>
> >
>
> > Hechong
>
> >
>
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