Stock material or miscellaneous articles – All metal or with adjacent metals – Laterally noncoextensive components
Reexamination Certificate
1999-04-30
2001-09-04
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Laterally noncoextensive components
C428S621000, C428S632000, C428S651000, C428S654000, C361S704000, C361S708000, C148S516000, C148S527000, C148S530000, C148S532000, C148S535000
Reexamination Certificate
active
06284389
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to composite materials constructed from a primary metallic material and having one or more secondary regions composed of a secondary material having disparate thermal conductivity properties. More specifically, composite materials are provided comprising a primary metallic material metallurgically bonded to one or more regions of secondary material having a high thermal conductivity that serves as a heat sink. In one embodiment, the primary metallic material comprises titanium and the secondary material having high thermal conductivity comprises a metallic composite material or a metal matrix material such as aluminum silicon carbide. The present invention also relates to methods of manufacturing such composite materials.
BACKGROUND OF THE INVENTION
Metallic materials are used in numerous applications where rigidity and high mechanical strength are required. For applications in which low density, lightweight metallic materials are desirable, aluminum and titanium metallic materials are generally suitable. Aluminum and titanium can be fusion welded to materials having compatible properties to provide a reliable and hermetic seal. For many applications, titanium exhibits superior properties and is a material of choice. Titanium, however, has relatively low thermal conductivity. For applications such as housings for electronic or electrical devices, where dissipation of heat from inside a three-dimensional structure or across a surface is necessary or desirable, titanium has generally not been considered as a consequence of its thermal conductivity properties.
Metal matrix composite materials, which incorporate a non-metallic reinforcing material dispersed within a metal matrix or host material, generally have desirable properties for many applications, including a low density, low CTE, high thermal conductivity and good mechanical strength. These properties may be manipulated somewhat by selecting the metal matrix material and the form, proportion and composition of the reinforcing material. Metal matrix materials comprising aluminum or aluminum alloy matrices incorporating silicon carbide reinforcing material have desirable properties for many applications.
Metal matrix composite materials have several practical disadvantages. Such materials generally cannot be machined and are provided in a three-dimensional configuration using a casting process. The use of casting techniques limits the tolerances and versatility of the three dimensional configurations available and increases the cost of producing three dimensional shapes. Metal matrix materials generally cannot be laser welded as a consequence of differences in energy absorption rates between the metal matrix material and the non-metal reinforcing material. Such materials must be joined to other components or structural materials using soldering or welding techniques, which are generally less reliable than fusion welding techniques.
It would therefore be desirable to provide a composite material in which the desirable properties of titanium and similar metals may be used advantageously, while additional desirable properties, such as high thermal conductivity, are also provided.
SUMMARY OF THE INVENTION
The present invention provides composite materials constructed from a primary metallic material metallurgically bonded to one or more secondary regions having desirable thermal conductivity properties and having a CTE that generally matches the CTE of the primary metallic material. The composite regions serve as heat sinks and provide thermal dissipation over a surface area or across a surface. The metallic material is preferably chemically reactive with a metallic constituent of the secondary region, providing a metallurgical bond between the metallic material and the one or more secondary regions. The CTE match of the secondary material with the primary metallic material and the metallurgical bond formed between the secondary material and the primary metallic material provide a composite material having reliable hermeticity and desirable mechanical strength properties.
One or more thermal coefficient of expansion property modifiers, such as one or more non-metallic reinforcing material(s), may be incorporated into the secondary material in a proportion sufficient to modify the CTE of the secondary region(s) so that it is compatible with the CTE of the primary metallic material. The metallic constituent of the secondary material preferably has a higher thermal conductivity than that of the primary metallic package material. Thus, the thermal conductivity of the secondary region(s) is different from (generally higher than) the thermal conductivity of the primary metallic material, yet the CTE of the secondary material substantially matches the CTE of the primary metallic material.
According to one embodiment, the primary metallic material comprises titanium, or a titanium alloy, and the one or more secondary regions(s) comprises a metal matrix composite material having a high thermal conductivity, such as aluminum silicon carbide (AlSiC). In this embodiment, the metallic aluminum component of the metal matrix material bonds metallurgically with the titanium component of the primary metallic material at the interface of the secondary region(s) with the primary metallic material. A desired proportion of silicon carbide material is provided in the metal matrix composite material such that the secondary region has a CTE that substantially matches the CTE of the surrounding primary metallic material. According to especially preferred embodiments, the CTE of the secondary region is slightly less than the CTE of the surrounding metallic base material.
According to another embodiment, the primary metallic electronics package material comprises titanium or a titanium alloy, and one or more secondary regions comprises a secondary material having a high thermal conductivity, such as composite metallic material. The term “composite” material, as used herein, refers to compositions composed of multiple base materials that are present in a variety of chemical and physical configurations. Composite materials thus comprehend both conventional “composite” materials, in which the constituents retain their individual chemical and structural integrity, and alloys, in which the constituents combine to form entities distinct from the individual constituents. Using this combination of primary and secondary materials, a metallurgical bond may be formed between the metallic package material and the secondary composite material. Additionally, the secondary metallic composite material has a high thermal conductivity compared to the thermal conductivity of the primary metallic material, yet the CTE of the secondary composite material substantially matches the CTE of the primary metallic package material.
This arrangement provides a composite material having desirably lightweight and low density properties that is particularly suitable for use in structural applications, such as housings, in which dissipation of heat over a surface area or across a surface is desired. The primary metallic material may be economically and conveniently formed in a two or three dimensional configuration using numerous conventional techniques, including machining, metal injection molding, casting, forging, or superplastic forming techniques. Using a primary metallic material that is machinable is desirable because machining operations achieve high tolerances and also provide versatility, since modifications to a two or three dimensional configuration may be provided simply by modifying the machining process.
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Jones Herman L.
Taylor Edward A.
Jones Deborah
Klaniecki James E.
Pacific Aerospace & Electronics, Inc.
Speckman Ann W.
Young Bryant
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