Hello,

We use Loctite's FP6100 wickable and supposed reworkable BGA underfill on a
few products to harden BGAs.  I have not tried removing an underfilled BGA
but Loctite says it is doable.

joe

-----Original Message-----
From: Steve Gregory [mailto:[log in to unmask]]
Sent: Friday, December 19, 2003 11:50 AM
To: [log in to unmask]
Subject: Re: [TN] BGA Underfill comments/recommendations


Hi Seppo!

I have asked the question in the past, and most of the responses told me
that
yes, underfilling does help array packages to survive shock, but it is a
complicated process that can be difficult, and does have some real
drawbacks.

One process that you might consider that will help increase shock
survivability 3-4 times more than just a soldered array package, is corner
bonding.

There was a good paper written and presented at APEX last year titled;
"Corner Bonding of CSP's; Processing and Reliability" that has a lot of data
from
drop tests done on corner bonded CSP's to show the increased reliabilty from
corner bonding.

Granted, the tests done were on CSP packages, but I asked the question if
the
same reliability gains would be realized with BGA packages and was told that
there should be....it's just that the testing was done with CSP's.

-Steve Gregory-


> Dear All,
>
> I am doing some checking into the effectiveness of BGA underfill on mobile
> handsets.
> Typically handset boards have 3-4 BGA's (0.5 to 0.8mm pitch) and have seen
> handsets with and without underfill.
> PCB thickness is 0.8mm
>
> Has anyone seen any studies, or have any comments on the reliability of
BGA
> joints wrt underfill.
> Also, any comments on what typically recommended underfill compounds are
is
> also appreciated.
>
> Thanks in advance! - and wishing you all a Merry Christmas and a Happy New
> Year !.
>
> --
> Seppo Saario
> Voxson Ltd., Core Technologies - Hardware
> Design Engineer
> Tel +61-7-3268-0745 ; Fax +61-7-3878-1370
>


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