Browse Prior Art Database

Two Part Wirebond Package

IP.com Disclosure Number: IPCOM000112957D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 121K

Publishing Venue

IBM

Related People

Beatty, C: AUTHOR [+2]

Abstract

Large commercial die such as DRAMs are typically packaged in plastic carriers and have wire bond pads down the center of the die. Tremendous cost and performance leverage could be realized by having these devices become dual use commodities by packaging them in carriers suitable for military and space applications. Until now the location of the wire bond I/O pads down the center of the device has been a major obstacle to achieving this end. The two-part packaging approach presented in this disclosure allows these devices in their present design to be packaged into the multilayered ceramic packages required for space and military applications. This approach allows "Commercial Off The Shelf" (COTS) devices to be used in military and space applications.

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Two Part Wirebond Package

      Large commercial die such as DRAMs are typically packaged in
plastic carriers and have wire bond pads down the center of the die.
Tremendous cost and performance leverage could be realized by having
these devices become dual use commodities by packaging them in
carriers suitable for military and space applications.  Until now the
location of the wire bond I/O pads down the center of the device has
been a major obstacle to achieving this end.  The two-part packaging
approach presented in this disclosure allows these devices in their
present design to be packaged into the multilayered ceramic packages
required for space and military applications.  This approach allows
"Commercial Off The Shelf" (COTS) devices to be used in military and
space applications.

      To use large commercial chips such as high density DRAMs in
space and military applications the devices must be assembled into
hermetic packages made of ceramic and metal.  These chips because of
their specialized commercial packaging often have input/output
wirebond pads located in their center which facilitates wirebonding
techniques used in plastic packaging.  In addition to commercial
packaging considerations these die are usually so dense that wirebond
pads cannot be placed along the edge of the die where they are
commonly located on Space Class die.  Due to the large size of these
die, wirebonds cannot be made to the center of the chip without
comprising wirebond reliability.  As a result of this packaging
problem the military and space electronics industry has been unable
to take advantage of the low cost and high density of commercial
memory die.

      In order to be able to use commercial memory die with wirebonds
pads located in the center of the die a special package approach has
been developed.  To eliminate the long wirebonds that bonding to
these centers pads would create, a special two part package has been
devised.  The concept of this package is to have the wirebond layer
of the package overhang the active surface of the die out to the
point where wirebonds lengths could be kept short enough to meet mil
and space reliability requirements.  The wire bond layer would cover
the top surface of the die out to where the wire bond pads are
located where there would be a window in the layer that would allow
wire bonding down to the chip (Fig. 1).  The problem then becomes how
is the die first bonded to the base layer of the package.  The
approach presented in this disclosure facilitates this assembly step
through the use of the two part package approach.  There are two
alternatives to this packaging approach:

1.  The two ceramic layers which form the base of the package and the
    the die cavity would remain separate from the wirebond
    bond/wiring layer.  The die would be bonded to the bottom two
    layers in the normal fashion, typically using silver-glass
    a...