Micron and Submicron-Scale Characterization of Interfaces in Thermal Interface Material Systems

[+] Author and Article Information
Arun Gowda

 GE Global Research, One Research Circle, Niskayuna, NY 12309gowda@research.ge.com

David Esler, Sandeep Tonapi, Annita Zhong, Florian Schattenmann

 GE Global Research, One Research Circle, Niskayuna, NY 12309

K. Srihari

 Electronics Manufacturing and Research Services, Department of Systems Science and Industrial Engineering, State University of New York at Binghamton, P.O. 6000, Binghamton, NY 13902

J. Electron. Packag 128(2), 130-136 (Feb 14, 2006) (7 pages) doi:10.1115/1.2188952 History: Received January 21, 2005; Revised February 14, 2006

One of the key challenges in the thermal management of electronic packages are interfaces, such as those between the chip and heat spreader and the interface between a heat spreader and heat sink or cold plate. Typically, thermal interfaces are filled with materials such as thermal adhesives and greases. Interface materials reduce the contact resistance between the mating heat generating and heat sinking units by filling voids and grooves created by the nonsmooth surface topography of the mating surfaces, thus improving surface contact and the conduction of heat across the interface. However, micron and submicron voids and delaminations still exist at the interface between the interface material and the surfaces of the heat spreader and semiconductor device. In addition, a thermal interface material (TIM) may form a filler-depleted and resin-rich region at the interfaces. These defects, though at a small length scale, can significantly deteriorate the heat dissipation ability of a system consisting of a TIM between a heat generating surface and a heat dissipating surface. The characterization of a freestanding sample of TIM does not provide a complete understanding of its heat transfer, mechanical, and interfacial behavior. However, system-level characterization of a TIM system, which includes its freestanding behavior and its interfacial behavior, provides a more accurate understanding. While, measurement of system-level thermal resistance provides an accurate representation of the system performance of a TIM, it does not provide information regarding the physical behavior of the TIM at the interfaces. This knowledge is valuable in engineering interface materials and in developing assembly process parameters for enhanced system-level thermal performance. Characterization of an interface material between a silicon device and a metal heat spreader can be accomplished via several techniques. In this research, high-magnification radiography with computed tomography, acoustic microscopy, and scanning electron microscopy were used to characterize various TIM systems. The results of these characterization studies are presented in this paper. System-level thermal performance results are compared to physical characterization results.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Determination of interfacial or contact thermal resistance

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Figure 2

TEM image of aluminum hydroxide nanoparticles dispersed in an epoxy resin

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Figure 3

Image showing filler depleted region toward the TIM-air interface

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Figure 4

No filler depleted region at TIM-aluminum interface

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Figure 5

SEM of TIM bondline

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Figure 6

Nanometer-scale voids at TIM-aluminum interface

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Figure 7

Air gap or delamination at TIM-aluminum interface

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Figure 8

Micron voids at TIM-aluminum interface

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Figure 9

Possible voiding at TIM-aluminum interface

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Figure 10

Void at filler particle-matrix resin interface

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Figure 11

High magnification radiography image of a TIM sample

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Figure 12

X-ray intensity profile along X‐Y (in Fig. 1)

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Figure 13

CT image of TIM sample shown in Fig. 1

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Figure 14

High magnification radiography images showing voids

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Figure 15

Thermal resistance of radiography samples

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Figure 16

SAM images showing voids in TIM layer

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Figure 17

Thermal resistance vs % of voided area



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