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April 1999

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From:
Energy Technology Systems <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 9 Apr 1999 09:38:43 -0700
Content-Type:
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My company, ETS, is a manufacturere of reflow equipment. Recently our
customer, Tektronix, came to us with a problem soldering BGA's using the
older IR ovens they had. After much discussion it was decided that they
would send me a sample board so we could evaluate, test and make
recommendations. Upon receiving the board we found that there were a lot of
large components, including BGA's. Matter of fact one of the BGA's was even
reflective. Of course you are probably already using a convection oven so
that would not apply in your case. Other things we noticed during testing is
that with such high mass it is very important to ensure you have a good
profile with low delta T's. Also one should watch the cross-belt temperature
uniformity.

I suggest you look at your profiles. Attach thermocouples near the problem
areas to see exactly what is going on during reflow. Sounds like you have
some large temperature differentials near the BGA's.

If you would like to send us a sample board we would be happy to develop
profiles for it and offer our recommendations. You should also feel free to
contact us offline for further discussion.

Sincerely,

Brian Stumm
ETS, LLC
509-483-0900 (voice)
mailto:[log in to unmask]
http://www.eznet.com/~ets

>> We have recently completed a prototype build of a board with a variety
>> of BGA styles on (PBGA196, PBGA119, PBGA256, PBGA357.) We have
>> experienced a functional failure rate of 80% attributable to the one
>> PBGA357 on each PCB, no such problems  were evident on the other BGAs.
>> X-ray analysis has not revealed any blatant errors (shorts, missing
>> balls etc.) nor were there any obviously poor contact solder joints,
>> except in one instance where possible non-wetting at the edge of some
>> lands was just visible.
>>
>> I'd be interested to hear from anyone who has experience with large
>> size BGAs who can suggest means to identify cause of failure and any
>> necessary assembly process adjustments we should make. Our equipment
>> list is Dek260AF printer, Philips CSM Eclipse CE1 pick&place,
>> Conceptronics HVA60 reflow oven.
>>
>> Thanks
>>
>> Nigel Burtt
>> Production Engineering Manager
>> D - European HQ
>> Email: [log in to unmask]
>> Tel:     01793 842132
>> Fax:    01793 842101
>>
>
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