Browse Prior Art Database

High Efficiency, Through Card Thermal Enhancement

IP.com Disclosure Number: IPCOM000107559D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 8 page(s) / 271K

Publishing Venue

IBM

Related People

Buller, L: AUTHOR [+3]

Abstract

This article presents a high efficiency, reworkable thermal enhancement for TAB (Tape Automated Bonding) packages and other modules, such as flatpacks, when, due to packaging or other constraints, the thermal enhancement must be located on the opposite side of the second-level carrier from the TAB packages or modules.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 32% of the total text.

High Efficiency, Through Card Thermal Enhancement

       This article presents a high efficiency, reworkable
thermal enhancement for TAB (Tape Automated Bonding) packages and
other modules, such as flatpacks, when, due to packaging or other
constraints, the thermal enhancement must be located on the opposite
side of the second-level carrier from the TAB packages or modules.

      Consider a high-function circuit card containing multiple TAB
components with individual high-power dissipations.  In order to
dissipate the heat generated by this system, the card could be
mounted to a heat sink with pedestals that protrude through the card
and connect the TAB components to the heat sink.  Problems that are
encountered in this packaging scheme include: (1) attachment of the
TAB components to the heat sink, (2) attachment of a non-planar card
to a planar heat sink, and (3) reworkability of the assembly, if
required.  This article discloses a technique that can be used to
solve these three problems.
METHODOLOGY

      The thermal enhancement technique disclosed here is intended to
cool high-function TAB devices (as shown in Figure 1) and consists of
a large heat sink that has been machined or otherwise formed such
that pedestals protrude from the base of the heat sink through
openings in an associated circuit card to make contact with TAB
components, which are mounted on the top surface of the card.
Several of the problems that have been encountered with this
technique are: (1) attachment of the TAB component to the heat sink
so that rework is possible and (2) bonding the circuit card to the
heat sink so that both surfaces are planar.  Attachment and rework
are a problem because of the multiplicity of TAB components on the
card (creating a high-cost assembly) and the permanent nature of the
TAB to heat sink bond that is required for good thermal performance.
Bonding the circuit card to the heat sink has been judged to be a
problem due to the non-planarity of the circuit card.  Without
adequate bonding between the circuit card and the heat sink, the
warpage inherent in the card could be such that good thermal contact
may not be made between the TAB component and the heat sink pedestal.

      These problems can be solved using an embodiment of the device
shown pictorially in Figure 2.  Here, the pedestal that was
originally made by machining or forming the heat sink base has been
essentially replaced by a screw fitted throughout the heat sink.  As
shown, the screw device serves the purpose of (1) attaching the
circuit card to the heat sink, (2) limiting the tolerance build-up
due to card warpage, (3) providing a pedestal for bonding the TAB
component to the heat sink, and (4) establishing a technique for
reworking a single TAB component.  Each of these concepts are
described in more detail below.
1. Attachment of the Circuit Card to the Heat Sink:

      Figure 2 shows a screw-type device which threads through the
heat si...