Amol,
1. a) What is your main concern, drop or thermal mismatch between board and
component?
b) Talk to your underfill supplier AND your part supplier.
c) The more you can tell your potential underfill supplier about the part
and finished product use conditions, the more likely they will be able to
advise you about the best underfill. IF you use the wrong underfill, you
can actually destroy solder joints during thermal cycling or not provide
optimum protection during drop.
3.a) Not storing the underfill in the conditions advised by the supplier.
b) Using out of date material.
c) Using too much and having it spread onto other components. This is
especially a problem with ordinary, non-reworkable underfills.
4. a) Visual inspection, usually with a stereomicroscope - look for evidence
of underfill all the way around the component.
b) Cross-section horizontally instead of vertically - trickier but you get
to see under the whole component body in one go.
5. Course by Dr. Brian Toleno of Henkel. Other underfill companies may also
have on-line info of equal value.
Bev
RIM
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Mahanna
Sent: Wednesday, March 18, 2009 9:31 PM
To: [log in to unmask]
Subject: Re: [TN] Underfill Application
Amol,
Pitfall- don't assume that every implementation of underfill increases
reliability.
Inspection- In certain circumstances I believe that you will find CSAM less
than adequate. We suggest a combination of acoustics and a special
sectioning/imaging technique that we use.
Don't forget about SIR and ECM. If you make 'em mechanically sound,
sometimes those pesky ionics will sneak up the failure hierarchy.
Chris
Chris Mahanna
Robisan Laboratory Inc.
6502 E. 21st Street
Indianapolis, Indiana 46219
317-353-6249
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kane, Amol (349)
Sent: Wednesday, March 18, 2009 3:48 PM
To: [log in to unmask]
Subject: [TN] Underfill Application
Dear Technetters,
We are about the develop a process for underfilling BGAs for a high
reliability application. the underfill will be a rework able underfill. I
wanted to poll the technet on:
1. Guidance on material selection
2. most common materials being used out there and the process equipment
being used to do so.
3. Common pitfalls and things to lookout for
4. inspection techniques used to inspect the finished product
5. a good source for info on underfilling (books, papers etc.,)
Thanks in advance.
Regards,
Amol
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