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Date: | Wed, 09 Apr 97 11:32:24 PST |
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My understanding of flip chip-
A method of direct chip attachment (DCA); IBM may not have developed
flip chip (?)but they probably perfected the design and manufacture of
flip chip in the late 1960's, on their humongous MCMs, dubbed "Thermal
Conduction Modules" (TCM) by IBMer's. A cutaway drawing of an IBM TCM
was the cover art on a late 60's or early 70's issue of Scientific
American.
IBM called their flip chip "C4", which I think stands for "controlled collapse
chip connection". C4 mounts the unpackaged die face down, via the reflowable C4
balls. Each ball sits on numerous metallization layers which have been deposited
at each chip I/O pad. The metallizations, their size and shape, the size of the
opening in the chip passivation around each C4 ball, ball metallurgy, and the
surface tension of the reflowed balls---all these lead to the controlled
collapse of the balls into a specific geometric form on the MCM substrate.
Flip chip requires the application of an "underfill" compound, which surrounds
the reflowed balls after substrate attachment; I think this is done to provide
reliable attachment under thermally induced cyclic loads.
Flip chip is obviously the grand-daddy of BGA, wherein the ball diameters and
pitch are smaller for flip chip, as compared to BGA.
Hope this helps.
Michael Alderete
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______________________________ Reply Separator _________________________________
Subject: what is a flip chip?
Author: [log in to unmask] at _internetcc
Date: 4/9/97 10:23 AM
Everyone -
What is a "flip chip"? I work in the PCB fabrication industry and see
this term a lot in magazine articles. I've never heard the basic
definition. Please help me increase my knowledge base.
Thanks
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