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December 2008

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Subject:
Re: ç­å¤: Re: [TN] BGA soldering open issue
From:
John Goulet <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Sun, 7 Dec 2008 14:43:57 +0000
Content-Type:
text/plain
Parts/Attachments:
text/plain (427 lines) 
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. How would I look at a cutomer design relative to the heat sink used. They  pick the size and shape for heat transfer because only the customer knows what the final system and thermal transfer properties are. We just assemble the board using their required parts.

-------------- Original message -------------- 
From: Werner engelmaier <[log in to unmask]> 

> 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 
> 
> > 
> 
> > 
> 
> > 
> 
> > 
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> > 
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> > 
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> > 
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> > 
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> > 
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> > 
> 
> > 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 
> 
> > 
> 
> > 
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> > 
> 
> > 
> 
> > 
> 
> > "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 
> 
> > 
> 
> > 
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> > 
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> > 
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> > 
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> > 
> 
> > What is the surface finish on your PCBA? 
> 
> > 
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> > 
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> > 
> 
> > 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? 
> > 
> 
> > 
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> > 
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> > 
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> > 
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> > 
> 
> > Hechong 
> 
> > 
> 
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