Microstructure and thermal properties of diamond/aluminum composites with TiC coating on diamond particles

doi:10.1016/j.matchemphys.2010.08.003

Materials Chemistry and Physics

Volume 124, Issue 1, 1 November 2010, Pages 851-855

https://doi.org/10.1016/j.matchemphys.2010.08.003 Get rights and content

Abstract

A titanium carbide coating on the surface of diamond particles was proposed to improve the interfacial bonding between diamond particles and aluminum alloy for diamond/aluminum composites. The diamond/aluminum composites with the TiC coating on diamond particles were fabricated by gas pressure infiltration. The composites were characterized with optical microscope and scanning electron microscopy and by measuring thermal properties, including thermal conductivity and coefficient of thermal expansion. The results show that the interface adhesion between the diamond particles and the aluminum matrix is strengthened due to the existence of the TiC coating, and the fracture mechanism of the composites is a combination of matrix's ductile fracture and interfacial debonding. Improvements in thermal properties, including a reduced thermal expansion and a high thermal conductivity, have been achieved by the TiC coating on diamond particles to get the good interface.

Introduction

Thermal considerations in electronic package design have become more and more important with the continuing miniaturization and integration of microelectronics, requiring ever more efficient heat removal. The thermal density of microelectronics device is further rising according to Moore's law [1]. Suitable materials must be selected as heat spreaders and heat sinks in order to dissipate the heat generated in electronic packages effectively. Heat sink materials with thermal conductivities above 300 W m⁻¹ K⁻¹ combined with a coefficient of thermal expansion (CTE) below 10 ppm K⁻¹ are required for future electronic components, such as microprocessors, LED, laser diodes or high power [2]. Traditional heat sink materials such as Mo/Cu, W/Cu or SiC/Al, however, despite featuring a low CTE mismatch, have thermal conductivities insufficiently high to exceed 200–250 W m⁻¹ K⁻¹.

Diamond is an attractive material with many outstanding properties, the highest thermal conductivity of all natural materials, very low CTE, harder than any other natural materials, the highest Young's modulus and so on. These properties make diamond an ideal filling material in metal matrix composites for electronic packaging application. The excellent thermal properties of diamond, however, can only be exploited to a large extent when an optimal interface between diamond particles and metal matrix is obtained. Thus, high adhesion strength and minimum thermal boundary resistance are the most important issues in this regard [3], [4].

The bonding between diamond particles and high conductive metals (such as Ag, Cu, Al) is generally weak. Pure liquid copper does not wet diamond and diamond/Cu composites made by powder metallurgy have been shown to feature weak interfacial bonding [5]. For the diamond–aluminum system, the aluminum matrix bonds to square {0 0 1} surfaces of the diamond, but does not stick to the hexagonal diamond faces (with {1 1 1} orientations) when the diamond surface is not specifically prepared [6], [7]. Thus, metal alloying with strong carbide forming elements and surface treatment on diamond are feasible methods to improve the interfacial bonding between diamond and metal matrix [3], [8], [9], [10].

In this work, diamond/Al composites with TiC coating on diamond particles were investigated, and the TiC coating was chosen because of its good wettability by aluminum [11], [12]. The purposes of this paper are twofold: (i) to produce diamond/Al composites with TiC coating on diamond particles and examine their microstructure and (ii) to investigate their thermal properties.

Section snippets

Materials

Aluminum alloy A356 (AlSi7Mg) was used as matrix material. Synthetic diamond particles of the MBD-4 grade were purchased from Henan Famous Industrial Diamond Co., Ltd. with designated particle diameters between 91 and 106 μm and cubo-octahedral morphology. The chemical compositions and physical properties of the diamond particles and the A356 alloy are presented in Table 1.

Coating process and gas pressure infiltration

The TiC coating on diamond particles was obtained via the chemical reaction between vacuum vapor deposited Ti and the

Coating composition

Micrographs in Fig. 2 illustrate the morphology of the coating on diamond particles, a uniform and compact coating was observed. Fig. 3 displays the phase composition of the diamond particles after coating. The TiC coating was formed by a chemical reaction between titanium and diamond via deposition processing, and the phase composition on the surface of the diamond particles at room temperature is C–TiC according to XRD analysis.

Microstructure of the composites

It is very difficult to polish the diamond/Al composites because

Conclusions

The diamond/Al composites with TiC coating on diamond particles prepared by gas pressure infiltration show a uniform microstructure in which diamond particles are distributed evenly in the matrix. The TiC coating on diamond particles improve the interfacial bonding between diamond {1 1 1} faces and Al alloy, and selective interfacial bonding in diamond–aluminum system is no longer observed. Chemical reactions take place between the TiC coating on diamond surfaces and Al alloy, which reinforces

Acknowledgement

This work has been supported by the National Natural Science Foundation of China under Grant No. 60776019.

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Microstructure and thermal properties of diamond/aluminum composites with TiC coating on diamond particles

Abstract

Introduction

Section snippets

Materials

Coating process and gas pressure infiltration

Coating composition

Microstructure of the composites

Conclusions

Acknowledgement

Mater. Sci. Eng. A

Diam. Relat. Mater.

Mater. Sci. Res. B

Compos. Sci. Technol.

Scripta Mater.

Trans. Nonferrous Met. Soc. China

J. Mater. Proc. Technol.

Composites A

J. Colloid Interface Sci.