Interesting to see you work with flipchip, Carey, I will come back to you in this matter. This is a warning, you still have time to shutdown your mailbox (he-he)./Ingemar
Tracy
As you know, wire bonding is a relatively old process. I, myself, was
involved in it in some detail about 10 years ago in a task force for
manufacturing problems, and that was old stuff then. As such, I've since
cleaned out my library and have little to offer you. As a starting point,
I'd look into a book "Electronic Packaging and Interconnection Handbook"
(1997) edited by Charles Harper (of IBM). From there, I'd track down the
references.
Once you have a handle on it, call some those that should know it (i.e., the
authors and hope that they are still doing it). Also, I think the company
Kulick and Soffa (spelling?, I think located in Pennsylvania) makes the
majority of wire bonding equipment. Try calling them.
But in short, wire bonding is a "mushing" together of two metals (wire and
pad, not necessarily the same metal). The ultrasonic (frequently also
heated) process breaks the interface (typically containing impurities...in
case of gold, I think it's sulfides as opposed to oxides for the rest of
most metals) and allows the grains from each metal part to be able to form
metallic bonds (i.e., without oxides) as well as crystal reorientation (to
increase the nearest atomic neighbors). While all this is scientific, it's
not too important. The point is that the breaking of a wire bond is at the
weakest location either at a) the thinnest point (i.e., the wire- I'm
ignoring large grained wire for you technical guys), b) the pad/substrate
interface, or c) the wire/pad interface because of poor metallic bonding
from not getting through the impurities (not because the wire did not go
deep enough). Because the ultrasonic process is the equivalent to a spring
pounding on the pad, the pad's elasticity (heavily dependent on thickness up
to a few microns... then it's nearly bulk and soft) effects the whole
process (as does rougness, etc.).
I've since moved onto other things (including flip chip a few years ago) and
am far from wire bonding.
Carey
-----Original Message-----
From: Tracy Black <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Friday, September 24, 1999 12:28 PM
Subject: Re: [TN] Wire bonding question
>Cary:
>
>I would like to know more about the wire bonding process. We make
innerconnects
>that often times terminate in a wire bond. Do you have any idea where I
might
>find such information?
>
>Tracy
>
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