I think they're pretty similar Joyce.

I believe peak temperatures were within 5 degrees of each other at the 
low end of the solderability window.

Regards,

Joyce Koo wrote:
> I suspect your 2 reflow profile are different? 
> --------------------------
> Sent using BlackBerry
>
>
> ----- Original Message -----
> From: TechNet <[log in to unmask]>
> To: [log in to unmask] <[log in to unmask]>
> Sent: Mon Nov 10 08:17:09 2008
> Subject: Re: [TN] Effect of Soldering in a Ni atmosphere on BGA reliabilty
>
> Hi Stewart,
>
> As I suspected.
>
> Yes PCB substrate is exactly the same (the boards were made to the same 
> test spec) as is the substrate on the bottom of the BGA.
>
> Thanks for the advice on micro-sectioning.
>
> Regards,
>
>
>
> Administrator wrote:
>   
>> Hi Eric,
>>
>> We have examined many BGA's assembled under both N2 and air. I think
>> that any differences would likely be quite subtle. The N2 may help
>> quicker wetting and spreading to the PCB substrate, and therefore may
>> allow for some flexibility in the reflow profile which is used (perhaps
>> a shade lower peak, but aside from IMC growth rates, would have little
>> impact on IMC type). 
>>
>> Have you checked to see whether the PCB substrate is the same in your
>> customers application as compared to your tests? The metallisation on
>> the PCB can have a surprisingly strong influence over IMC type and
>> growth speed at the interface between solder ball and BGA package. What
>> is the finish on the device - electrolytic Ni? 
>>
>> Would suggest that a thorough micro-section analysis is the most
>> effective way to define the condition of the materials and learn more.
>> Would be a useful benchmarking exercise to compare your test vehicle
>> results to customer failure. 
>>
>> Kind regards,
>>
>> Stewart
>>
>> Stewart McCracken
>> MCS Ltd.
>> Centre House
>> Midlothian Innovation Centre
>> Roslin
>> Midlothian
>> EH25 9RE
>>  
>> m. +44(0)7711 541735 
>> t.   +44(0)131 440 9090
>> f.   +44(0)131 440 9085
>> e.  [log in to unmask]
>> w. www.themcsgroup.co.uk
>>
>>
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Eric CHRISTISON
>> Sent: 10 November 2008 10:01
>> To: Administrator
>> Subject: [TN] Effect of Soldering in a Ni atmosphere on BGA reliabilty
>>
>> A customer has experienced solder joint failures in a lead free BGA 
>> device which are unexpected for us.
>>
>> The test the solder joints failed was a shock test in the plane of the 
>> PWB and the joints failed at the interface between the SJ and our BGA 
>> device substrate.
>>
>> We've done similar tests without failure but when we did our trials we 
>> soldered the devices onto the boards in a hot air oven. Our customer 
>> used a nitrogen oven. Could this affect SJ strength in any way?
>>
>> Just wondering whether this is worth investigating.
>>
>> Regards,
>>
>>
>>   
>>     
>
>   

-- 
Eric Christison Msc
Mechanical Engineer
Consumer & Micro group
Imaging Division

STMicroelectronics (R&D) Ltd
33 Pinkhill
Edinburgh EH12 7BF
United Kingdom

Tel:	+44 (0)131 336 6165
Fax:	+ 44 (0)131 336 6001

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------