Thanks for the input anyway Bill, it is true that currently the underfill
is applied after reflow, but i'm investigating underfills that will be
preapplied, with the chip placed on it and then reflowed. This would
greatly reduce process time when compared to the current methods of
capillary underfills.
I'd appreciate any other comments on this topic by anyone in the industry.
Being new to the SMT business, its relatively difficult to fully understand
all the intricacies involved so it was great finding out about this forum
and getting comments/advice!
Best regards,
Hann
"Campbell, William (wcampbel)" <[log in to unmask]> on 12/06/2000 10:11:31
AM
To: Hann Pang/US-Corporate/3M/US@3M-Corporate
cc:
Subject: RE: [TN] Query: industry standard for pretreating PWB/PCB before
underfilling?
Hann-
I don't have any hands on experience with flip chip at the moment, but if
the underfill was applied soon after reflow, I don't imagine there would be
much outgassing, if any. Maybe I have this process backwards (ie underfill
then reflow). If so, there still shouldn't be much outgassing if the pcbs
are handled properly prior to use. Sorry I can't be of more help; I'd love
to see what all the flip chip fuss is about, but our products don't utilize
this technology yet.
Bill C
-----Original Message-----
From: Hann Pang [mailto:[log in to unmask]]
Sent: Tuesday, December 05, 2000 1:15 PM
To: [log in to unmask]
Subject: Re: [TN] Query: industry standard for pretreating PWB/PCB
before underfilling?
Hi Hans,
In the process of mounting flip chips or chip scale packages to PCBs,
there's a need to fill the gap between the chip and the board with an
adhesive to minimise the CTE mismatch between the board and the die. this
is known as underfilling. and the reason i'm asking is because reliability
of the solder joints is compromised when there is a lot of outgassing from
the board into the adhesive material while curing. If there was
pretreating of the boards in an oven, this problem would be greatly
reduced. thanks
Hann
Hans Hinners <[log in to unmask]> on 12/05/2000 12:00:15 PM
To: "'TechNet E-Mail Forum.'" <[log in to unmask]>
Hann Pang/US-Corporate/3M/US@3M-Corporate
cc:
Subject: RE: [TN] Query: industry standard for pretreating PWB/PCB before
underfilling?
Hann,
Help me out here. By underfill do you mean an application of an RTV or is
it some other process?
Hans
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hans M. Hinners
Process Engineer
Toppan Electronics, Inc.
770 Miramar Road
San Diego, CA 92126
(858) 695 - 2222 ext. 241
(858) 695 - 6823 fax
[log in to unmask]
-----Original Message-----
From: Hann Pang [mailto:[log in to unmask]]
Sent: Tuesday, December 05, 2000 9:27 AM
To: [log in to unmask]
Subject: [TN] Query: industry standard for pretreating PWB/PCB before
underfilling?
Hi
Can someone help me with the question?? Thank you very much.
I'm posting the above question as a technical marketer for 3M. We're
currently working on underfills and the question is posed in consideration
of the outgassing of the PCBs.
If there is'nt a standard, then the next question is; typically, what are
the pretreating conditions if there is any pretreating at all?
Thanks and regards,
Hann Pang
Technical Markerter
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