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Low Profile Heat Sink for Stacked Memory Chips

IP.com Disclosure Number: IPCOM000120175D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 52K

Publishing Venue

IBM

Related People

Agonafer, D: AUTHOR [+2]

Abstract

Plastic encapsulated semiconductor memory chips are attached to a substrate in a row and column array, as is conventional. The chips are cooled by direct immersion into a dielectric liquid. Jet impingement or other forced flow, or natural convection, or boiling heat transfer is used to cool the chips. The plastic housing encapsulating a chip is cut away to expose a portion of the back side of the chip. A low profile metal heatsink is attached to the chip through conventional bonding methods providing a low thermal resistance from chip to heatsink. A basic heatsink consists of a rectangular solid bar spanning the length of the chip, with a width dimension equal to or less than the width of the plastic body. Memory chips are now stacked one upon another to increase memory per unit area of substrate.

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Low Profile Heat Sink for Stacked Memory Chips

      Plastic encapsulated semiconductor memory chips are attached to
a substrate in a row and column array, as is conventional.  The chips
are cooled by direct immersion into a dielectric liquid.  Jet
impingement or other forced flow, or natural convection, or boiling
heat transfer is used to cool the chips.  The plastic housing
encapsulating a chip is cut away to expose a portion of the back side
of the chip. A low profile metal heatsink is attached to the chip
through conventional bonding methods providing a low thermal
resistance from chip to heatsink.  A basic heatsink consists of a
rectangular solid bar spanning the length of the chip, with a width
dimension equal to or less than the width of the plastic body.
Memory chips are now stacked one upon another to increase memory per
unit area of substrate.  The physical size of each heatsink is
determined by the cooling method employed.  For jet impingement
cooling each higher chip has a shorter extension of the heatsink so
as to not overshadow the heat sink below it, whereas for forced
convection, natural convection or boiling all heatsinks can be of the
same size.  The different sizes of heatsinks provide uniform cooling
of the memory chips regardless of position in the memory chip stack.

      The figure shows a memory chip stack with an upper chip 1 and a
lower chip 2.  The lower chip 2 has an extended low profile heat sink
3 for jet impingement or forced...