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Method for attachment/loading to optimize thermal interface thickness between a heatsink and a bare die

IP.com Disclosure Number: IPCOM000010219D
Publication Date: 2002-Nov-06
Document File: 6 page(s) / 71K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for attachment/loading to optimize thermal interface thickness between a heatsink and a bare die. Benefits include improved thermal performance, improved reliability, and improved ease of manufacturing.

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Method for attachment/loading to optimize thermal interface thickness between a heatsink and a bare die

Disclosed is a method for attachment/loading to optimize thermal interface thickness between a heatsink and a bare die. Benefits include improved thermal performance, improved reliability, and improved ease of manufacturing.

Background

        � � � � � The disclosed method addresses the difficulty of attaching a heatsink directly to a bare die with thermal interface material (TIM). Because the power dissipation of a chipset product keeps increasing, a thermal solution, such as a heatsink, is required to maintain the chipset and mobile products under the acceptable maximum operation temperature. Conventional heatsink attachment with a spring clip or wave solder techniques do not provide reliable thermal performance.

        � � � � � For chipset products, a wave-solder heatsink-attach technology is conventionally used (see Figure 1). The heatsink is placed on top of the bare die with TIM, such as phase-change material (PCM). The heatsink has one extended pin at the each corner of the heatsink base. These pins are inserted into the corresponding holes on the motherboard. The holes are filled with solder, and the assembly is passed through a wave-solder oven where the solder is reflowed. The heatsink is attached to the motherboard. The wave-solder heatsink attachment used by chipsets provides the end-of-line mean thermal resistance (Rj-s) of approximately 1.3°C-cm2/W, which is insufficient to meet the future chipset products with increased thermal constraints.

General description

        � � � � � The disclosed method attaches a heatsink to a bare die with TIM in between the heatsink and die without a conventional retention mechanism. The major benefits are simplicity and reduced expense of the assembly process. The disclosed method is a potential solution for chipset products.

        � � � � � The key elements of the method include:

•        � � � � Die

•        � � � � Heatsink/heat spreader

•        � � � � Loading scheme to optimize bond line thickness (BLT)

•        � � � � Epoxy

•        � � � � Epoxy dispensing equipment

•        � � � � Epoxy curing oven

        � � � � �

Advantages

        � � � � � The disclosed method provides advantages, including:

•        � � � � Improved thermal performance over wave-solder technology (an improvement of 71% in thermal resistance)

•        � � � � Improved reliability due to permanent attachment to avoid heatsink fall-off issue

•        � � � � Improved reliability due to improved resistance to mechanical shock and vibration

•        � � � � Improved reliability due to minimization of thermo-mechanical artifacts that can contribute to degradation of the thermal performance of the TIM when the units are subjected to accelerated stress

•        � � � � Improved reliability due to improved BLT control

•        � � � � Improved reliability due to improved piece-part variability

•        � � � � Improved ease of manufacturing due to a minimal number of parts

•        � � � � Improved ease of manufacturing due to i...