Stock material or miscellaneous articles – All metal or with adjacent metals – Having metal particles
Reexamination Certificate
2002-02-27
2003-06-17
Jenkins, Daniel J. (Department: 1742)
Stock material or miscellaneous articles
All metal or with adjacent metals
Having metal particles
Reexamination Certificate
active
06579623
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a composite material member for a semiconductor device, and insulated and non-insulated semiconductor devices using the composite material member.
RELATED ART
Conventionally, a material member that supports a semiconductor device substrate often serves also as one electrode for a non-insulated semiconductor device. In a power transistor device with power transistor chips mounted solidly on a copper base with a Pb—Sn solder material, the copper base (metal supporting member) serves both as a collector electrode of a transistor and a supporting member. This semiconductor device allows a few or more amperes of collector current to pass, causing the transistor chip to generate heat. In order to prevent instability of properties and reduction in lifetime caused by this heat-generation, the copper base also serves as a member for dissipation of heat. In addition, in the case where semiconductor chips with pressure resistance and adaptability to high-frequency enhanced so that a large amount of current can be passed therethough are directly mounted by soldering on a copper base, the role of the copper base is increasingly important not only as an intermediate member for dissipating heat but also for providing high reliability of the soldered mount.
In addition, in an insulated semiconductor device in which all the electrodes of the semiconductor device are insulated from metal supporting members, whereby the degree of freedom in circuit application of the semiconductor device can be increased, all the electrodes are insulated by insulating members from all package members including the metal supporting member and pulled to the outside. Therefore, even in a case example in which a pair of main electrodes is isolated from ground potential on the circuit, the package can be fixed to a ground potential portion irrespective of the electrode potential, thus making it easy to implement the semiconductor device.
Also, in an insulated semiconductor device, it is needed to dissipate efficiently heat generated during operation of the semiconductor device to outside of the package for operating the semiconductor element safely and stably. This dissipation of heat is usually achieved by transferring heat to the atmosphere from a semiconductor element substrate that is a source of generated heat through each member bonded thereto. The insulated semiconductor device includes in this heat transferring path an insulator, adhesive layers used in the portion to which the semiconductor substrate is bonded, or the like, and a metal supporting member.
In addition, the larger the amount of electric power needed by the circuit including the semiconductor device, or the higher the required reliability (stability with time, humidity resistance, heat resistance, etc.), the more complete insulation quality is required. The heat resistance mentioned herein includes heat resistance when a large amount of electric power is needed by the semiconductor device and thus the amount of heat generated in the semiconductor device is increased, in addition to heat resistance when the ambient temperature of the semiconductor device is increased due to an external cause.
On the other hand, the insulated semiconductor device generally has incorporated therein a certain integrated electric circuit including the semiconductor element substrate, and therefore it is necessary to electrically insulate at least part of the circuit from a supporting member. For example, in “Semiconductor/DBS Substrate for Communication”: Electric Material (vol. 44, No. 5), p65-69 (1989) as a first prior art, is shown a power module device in which an assembly with Si chips mounted on an AlN ceramic substrate having copper plates bonded to the both faces (hereinafter referred to as copper-clad AlN substrate) is solidly attached to a copper supporting member by soldering with a solder.
In the above first prior art, the copper-clad AlN substrate has AlN-specific properties such as high thermal conductivity (190 W/m·K), low thermal expansibility (4.3 ppm/° C.) and high insulation quality (1015 &OHgr;·cm) in combination with copper-specific properties such as high thermal conductivity (403 W/m·K) and high electric conductivity (1.7×10
−6
&OHgr;·cm), and is a component effective for mounting directly by soldering an electric power semiconductor element substrate (Si: 3.5 ppm/° C.) in which current density is high and a significant amount of heat is generated to obtain a module device having excellent heat dissipation quality and reliability.
Generally, the copper-clad AlN substrate plays a role of insulating electrically from a copper supporting member a semiconductor element substrate mounted thereon by soldering or an electric circuit formed therein, and forming a heat flow pass from the semiconductor substrate to a cooling fin to enhance the dissipation effect thereof. In addition, with the copper-clad AlN substrate, a semiconductor substrate of small thermal expansivity can be mounted directly on the copper-clad AlN substrate without using a particular heat expansion control material (e.g. Mo and W), thus making it possible to reduce the number of components for the power module device and the number of integration processes.
In JP-A-8-111503 specification as a second prior art, there is disclosed a semiconductor current control device in which an assembly with Si chips mounted on a copper-clad AlN substrate is solidly attached by soldering with a solder to a supporting member composed of Mo. In this prior art, since the copper-clad AlN substrate is mounted by soldering on a Mo supporting member whose thermal expansivity (5.1 ppm/° C.) is approximately same as that of the AlN substrate, the joint between these members is highly reliable, and works effectively for preventing degradation of heat dissipation quality.
In JP-B-7-26174 specification as a third prior art there is disclosed a semiconductor module device in which an assembly with thyristor chips mounted on an alumina substrate is mounted on a supporting member composed of a composite material with SiC ceramic powders dispersed on Al or an Al alloy (hereinafter referred to as Al/SiC composite material). In this prior art, since the alumina substrate is mounted on an Al/SiC composite material supporting member whose thermal expansivity (2.13 ppm/° C.) is approximately same as that of the alumina substrate (7.5 ppm/° C.), the joint between these members is highly reliable, and works effectively for preventing degradation of heat dissipation quality.
In JP-A-9-17908 specification as a fourth prior art there is disclosed a semiconductor device in which an assembly with Si chips mounted by soldering on a copper-clad AlN substrate is solidly attached by soldering with a solder to a supporting member composed of a composite material that is plane and has Cu layers (thermal conductivity: 403 W/m·K, thermal expansivity: 16.7 ppm/° C.) and invar layers (Fe-36 wt % Ni, thermal conductivity: 15 W/m·K, thermal expansivity: 1.5 ppm/° C.) alternately deposited in its main face in such a manner as to form a stripe pattern (hereinafter referred to as striped composite material). In this prior art, since the copper-clad AlN substrate is mounted by soldering with a solder on a striped composite material supporting member whose thermal expansivity (6.1 to 9.2 ppm/° C.) is approximately same as that of the copper-clad AlN substrate, the soldered joint between these materials is highly reliable, and works effectively for preventing degradation of heat dissipation quality.
In “Clad Material CIC for Semiconductor Substrate”: Catalog of Hitachi Densen Co., Ltd. (CAT. No. B1-105), (April 1993) as a fifth prior art, is disclosed a heat sink material for power transistors for semiconductor substrates composed of a composite material with both faces of an invar layer cladded with Cu layers (hereinafter referred to as clad material, 4.0 to 10.6 ppm/° C.). In this prior art, the clad material can be used as a member supporting a copper-clad AlN substr
Fukuda Kunihiro
Kondo Yasuo
Koyama Kenji
Kurihara Yasutoshi
Morita Toshiaki
Crowell & Moring LLP
Hitachi , Ltd.
Jenkins Daniel J.
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