You are very welcome Raye,

And if you do have a problem once in a while, I'm sure we can be of 
help. After all that is what we do :-). 

Best regards,

Vladimir

On Fri, 2 Mar 2012 11:32:47 -0800, "Rivera, Raye" <[log in to unmask]> wrote:
Hi Vladimir,
>
> Thanks for the reply. Your point is well taken. Not much good having 
> robust solder joints if the device fails.  Best regards,
> Raye Rivera
>   QA Manager * Canoga Perkins * 818-678-3872  * [log in to unmask]
>
> -----Original Message-----
> From: vladimir Igoshev [mailto:[log in to unmask]] Sent: 
> Thursday, March 01, 2012 4:00 PM
> To: TechNet E-Mail Forum; Rivera, Raye
> Subject: Re: [TN] BGA Reverse Backwards Compatibility
>
> Hi Raye,
>
> From the metallurgical point of view there is not much of the 
> difference whether it's SAC BGAs with Sn-Pb or vice versa. 
>
> However!!! When one puts Sn-Pb BGA through a Pb-free profile,  long 
> term reliability of the component itself might be jeopardized. 
> Vladimir
>
> SENTEC Testing Laboratory Inc. 
> 11 Canadian Road, Unit 7. 
> Scarborough, ON M1R 5G1
> Tel: (416) 899-1882
> Fax: (905) 882-8812
> www.sentec.ca
>
> -----Original Message-----
> From: "Rivera, Raye" <[log in to unmask]>
> Sender: TechNet <[log in to unmask]>
> Date: Thu, 1 Mar 2012 12:11:12 To: <[log in to unmask]>
> Reply-To: TechNet E-Mail Forum <[log in to unmask]>,
>         "Rivera, Raye"
>  <[log in to unmask]>
> Subject: [TN] BGA Reverse Backwards Compatibility
>
> Hello TechNet Gurus. 
>
> I have seen lots of discussion and studies on the reliability of 
> using BGAs with SAC solder balls on an assembly with SnPb paste. Many 
> people are interested in this topic because of backwards 
> compatibility issues when SnPb BGAs aren't available. At the risk of 
> oversimplifying a complex topic, I understand this can be successful 
> using a backward compatibility thermal profile such as the one shown 
> on Figure 8-20 of IPC-7095B to ensure complete melting of both types 
> of solder. Of course we must take care that the profile does not 
> exceed the temperature limitations of the SnPb paste. 
>
> Is anyone aware of any study done on the reverse situation? That is, 
> SnPb BGAs used with SAC solder paste and a SAC thermal profile? I 
> would think it would be at least as reliable as the above situation. 
> We definitely get complete melting and the temperature profile is 
> correct for the SAC solder paste chemistry so we are not as concerned 
> about holding a narrow process window. 
>
> This is not just academic curiosity on my part. We have some 
> prototype boards built with SnPb BGAs SAC paste, and SAC profile. 
> They are not for sale to customers, but some of our engineers are of 
> the opinion that any mixed process joint is suspect. I'd like to find 
> some data on the topic. 
>
> I hope everyone is enjoying Apex. 
>
> Best regards,
> Raye Rivera
>
> QA Manager * Canoga Perkins
> 20600 Prairie Street * Chatsworth * CA 91311-6008
> 818-678-3872  * [log in to unmask]
>
>
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