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September 2012

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From:
"Rivera, Raye" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Rivera, Raye
Date:
Wed, 26 Sep 2012 09:05:15 -0700
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In a past job I built some assemblies using lead paste and lead-free BGAs. Because the company was a CM I never did get any long term reliability information from our customer, but we used a lead-free profile and had no problems with ball collapse. 

I am very interested to see any information on the reliability of mixed process joints when the reflow profile is sufficiently hot to achieve complete mixing. The few studies I've read, most recently Richard Coyle's work presented at Apex, used thermal cycling and as I recall the mixed process joints performed as well or better than lead-free process. 

We are developing a product now using a BGA that is not available with tin-lead balls. Reballing would exceed the manufacturer's limit for number of heat excursions. So we seriously considered mixed-process, but in the end opted to go all lead free. The experience did leave me wondering how fact-based the mixed process concerns are. Does anyone have notable successes or failures to share?


Best regards,
Raye Rivera
 
 
QA Manager * Canoga Perkins * 818-678-3872  * [log in to unmask]

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Tuesday, September 25, 2012 5:26 PM
To: [log in to unmask]
Subject: [TN] Leaded Paste and Lead Free BGAs - Do they mix?

Hi,

 

I have a customer using leaded paste with lead free BGAs. I think they want
to have the balls NOT collapse for better optical inspection.

 

Sounds like a really bad idea to me but I have no explanation where I can
say as why.

 

Can anyone make suggestions either way?

 

Thanks,

Bob K.



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