JPH01319638A - Composite material having low thermal expansion and high thermal conductivity - Google Patents

Abstract

PURPOSE:To develop the composite material having low thermal expansion and high thermal conductivity by alternately disposing the parts where fibers are compounded with a matrix and the parts which consists of only the matrix in the fiber-reinforced metal subjected to intra-surface pseudo isotropic reinforcement and disposing these parts in such a manner that the parts consisting of only the matrix intersect with each other. CONSTITUTION:Metals such as Al and Cu are used as the matrix and carbon fibers or silicon carbide fibers having, for example, 5-15mum diameter are used as reinforcing fibers. The parts 2 consisting of only the matrix metal such as Al or Cu and the parts 1 formed by compounding and incorporating 1,000-16,000 pieces of the bundles of the above-mentioned fine-diameter reinforcing fibers in the matrix metal at least at >=50% volumetric content are alternately disposed. The parts 2 consisting of only the matrix metal of the 2nd layer and the composite parts consisting of the matrix 2 and the reinforcing fibers 1 are alternately disposed into many layers in such a manner that the direction of the reinforcing fibers intersects with the direction of the reinforcing fibers of the 1st layer at 90 deg. angle. Since the parts of only the matrix contg. no fibers exist to penetrate the layers in the perpendicular direction, the thermal conductivity is high in the perpendicular direction; in addition, the composite material composed of the metal and the fibers having the small coefft. of thermal expansion by the presence of the composite fibers is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a low thermal expansion and high thermal conductivity composite material used in electronic devices and the like.

[Conventional technology]

Continuous fiber-reinforced metal can have a low coefficient of thermal expansion, and is expected to be used as a low thermal expansion and high thermal conductivity substrate material whose thermal expansion coefficient matches that of ceramic substrates or silicon. (For this technical field, for example,
It is described in Publication No. 7420. ) In particular, carbon fibers have a low coefficient of thermal expansion in the axial direction of the fibers, and can be embedded in a metal matrix to obtain a desired low thermal expansion material. Among them, aluminum reinforced with carbon fiber,
Because it has low thermal expansion, high thermal conductivity, and is lightweight, it is expected to be used as a lightweight material for use in transportation equipment such as space, aviation, and automobiles. Figure 4 shows carbon fibers of 00 and 9.
It is a characteristic diagram showing the relationship between the coefficient of thermal expansion in the in-plane direction and the fiber volume content σ) in a carbon fiber-reinforced aluminum composite material that is oriented in two directions including the 0° direction and is pseudo-isotropic in the plane.

The vertical axis represents the coefficient of thermal expansion (c), and the horizontal axis represents the fiber volume content. When used as a low thermal expansion and high thermal conductivity substrate material,
Match the thermal expansion coefficient with that of the ceramic substrate or silicon, and select an appropriate fiber volume content from Figure 4. Carbon fiber reinforced aluminum also has excellent thermal conductivity.
The in-plane thermal conductivity of the in-plane pseudo-isotropic material is 90 W-m- when the fiber volume content is 60%.

[Problem to be solved by the invention]

The drawbacks of these conventional in-plane pseudo-isotropic continuous fiber reinforced metals are:
Thermal conductivity in the direction perpendicular to the surface is poor. The cause of this can be explained from the composite side (see, for example, page 45 of Composite Materials Engineering (Japan Society of Science and Technology) edited by Takeshi Hayashi); in the direction parallel to the fiber axis, the thermal conductivity has an upper limit value due to the composite side, and the fiber axis This is due to the fact that it has a value close to the lower limit in the perpendicular direction. In carbon fiber reinforced aluminum, the carbon fiber itself has anisotropy, and the thermal conductivity in the direction perpendicular to the fiber axis is significantly lower than in the direction of the fiber axis, so the thermal conductivity in the direction perpendicular to the plane is even worse. There was a problem. This problem is particularly severe when used in a configuration as shown in the cross-sectional configuration diagram of FIG. 5, for example. Ru. In FIG. 5, (8) is a low thermal expansion and high thermal conductivity composite material, a ceramic substrate (9) is bonded to it, and an element αO is mounted on the ceramic substrate (9). The direction in which thermal expansion is desired to be kept low is the in-plane direction of the low thermal expansion and high thermal conductivity composite material (8). α]) is a heat sink, and when cooling is performed from the back side of the low thermal expansion and high thermal conductivity composite material (8) as in this configuration, the direction where high thermal conductivity is required is the low thermal expansion and high thermal conductivity composite material (8). 8)
The direction is perpendicular to the plane of For this reason, conventional in-plane pseudo-isotropic continuous field and fiber-reinforced metals have a problem of high thermal resistance.

This invention was developed in order to solve the above problem σ), and it is possible to suppress the thermal expansion in the in-plane direction and at the same time increase the thermal conductivity in the direction perpendicular to the plane. The aim is to obtain a high thermal conductivity composite material.

[Means for solving problems]

The low thermal expansion and high thermal conductivity composite material of the present invention is a fiber-reinforced metal reinforced quasi-isotropically in a plane, in which portions in which fibers are combined with the matrix and portions in which only the matrix is formed are arranged alternately in the plane. The structure is such that the distribution pattern and only the parts of the squares are continuous in the direction intersecting the above-mentioned plane.

[Effect]

In this invention, since the matrix is composited with fibers, the coefficient of thermal expansion in the plane direction can be lowered.

Furthermore, since the matrix-only portion is arranged to exist in a row in a direction intersecting the plane, the thermal conductivity in the direction perpendicular to the plane can be increased.

〔Example〕

The average fiber content of the entire low thermal expansion and high thermal conductivity composite material according to the present invention is set to an amount that achieves a predetermined coefficient of thermal expansion in the in-plane direction. The composite fibers in the matrix (the matrix is mediated between the Pj fibers and the fibers and the matrix are integrated) are arranged alternately with the matrix-only parts, and from a macroscopic perspective, they are substantially uniformly distributed. Therefore, this average fiber content is the same as in the conventional configuration, that is, in the case where the fibers of one tree are almost uniformly distributed in the matrix and the matrix. In addition, it is configured so that the matrix-only part is continuous in the direction that intersects the plane (
For example, by arranging fibers), the thermal conductivity in the direction perpendicular to the plane is superior to that of fibers.It is now possible to take advantage of the high thermal conductivity of the matrix, improving the thermal conductivity in the direction perpendicular to the plane. be able to.

The part where the fiber is composited with the matrix has a content of 50% or more
It is preferable to have a fiber volume content of 7"1. If it is less than this, it will be difficult to obtain a sufficiently large cross-sectional area of only the continuous matrix, and the effect of improving thermal conductivity will be reduced. In addition, it is preferable that the cross-sectional area of the continuous matrix-only part is 0.01 f12 as a unit.If the cross-sectional area is 0.01 f12, for example, the matrix-only part can pass through a flat plate. In addition, it is preferable that this cross-sectional area is 5 m2 or less, and if it is larger than this, only the high fiber content area, matrix, and Problems arise due to the difference in coefficient of thermal expansion between the two parts, such as cracks being more likely to occur at the boundary when subjected to thermal changes, and minute irregularities being more likely to occur on the surface.

Further, as the reinforcing fibers used in this invention, for example, carbon, SiC, etc. are used, and as the matrix, for example, aluminum, copper, etc. are used.

An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1(a), 1(b), and 1(c) each show the structure of a low thermal expansion and high thermal conductivity composite material according to an embodiment of the present invention, in which (a) is a schematic perspective view, (b) is a schematic plan view, (c) is a schematic cross-sectional view. In the figure, (1) is a part where the matrix is composited with fibers, in this case a part where carbon fibers are composited with aluminum so that the fibers are oriented in one direction, and (2) is a part with only the matrix, in this case is an aluminum-only part. The first layer is a composite of fibers with fibers oriented in one direction arranged at certain intervals ( ]), and the second layer is a composite of fibers with fibers oriented in one direction. Part (1) is the first layer and 90
They are lined up at a certain distance, forming an angle. The next third layer is the same as the first layer, and the fourth layer is the same as the second layer.
They are arranged 90 degrees apart in order. Also in the same figure (1))
As shown in Figure 2, the matrix-only portions without fibers penetrate perpendicularly to the plane direction and are continuous.

FIG. 2 is a schematic diagram showing an example of a manufacturing method for obtaining the fiber arrangement of the composite material shown in FIG. 1.

First, place thin pins (4) at appropriate intervals around the metal plate (3).
Prepare a jig with the A bundle of carbon fibers (5) is applied while applying appropriate tension to connect the opposing pins (4).
As shown in Figure 2, it is stretched back in a staggered manner. After applying the first layer, apply the second layer at right angles to the first layer. Repeat this until the desired thickness is achieved. Only matrix without fibers t17′117°
The area of 2) is determined by the thickness of the pin (4). A composite part of fibers oriented in one direction (1
) depends on the size of the fiber bundle (5). The fiber bundle (5) in this example contains 1000 to 16000 carbon fibers with a diameter of 5 to 15 μm. The fiber content can be adjusted by the tension of the fibers or by appropriately compressing them in the thickness direction after tensioning. The carbon fiber preform molded in this way is impregnated with an aluminum matrix by high-pressure solidification casting method.
A carbon fiber-reinforced aluminum composite material with low thermal expansion and high thermal conductivity according to an embodiment of the present invention was obtained.

FIG. 3 is a characteristic diagram showing the relationship between the thermal conductivity in a direction perpendicular to the surface of the low thermal expansion and high thermal conductivity composite material thus obtained and the fiber volume content. For comparison, the characteristics of a conventional composite material in which fibers are distributed almost evenly in the matrix are also described. In the figure, the vertical axis shows the thermal conductivity in the direction perpendicular to the plane, and the horizontal axis shows the fiber volume content, and the characteristic curve (6)
represents the characteristics of this embodiment, and characteristic curve (7) represents the characteristics of the conventional example. From the figure, it is clear that the lower the fiber content, the larger the difference between the two, and that the thermal conductivity of the low thermal expansion and high thermal conductivity composite material of this example is superior to the conventional material.

It can be suitably used as a substrate material for a single-child device configured to conduct heat in a direction perpendicular to the surface.

In addition, the structure of the low thermal expansion and high thermal conductivity composite material Fl of this invention,
And the manufacturing method thereof is not limited to the above embodiments, for example, the fiber orientation may be shifted by 60 degrees to make it pseudo isotropic in a plane, or two or more types of fibers may be composited, It has a similar effect.

〔Effect of the invention〕

As described above, according to the present invention, in a fiber-reinforced metal reinforced quasi-isotropically in a plane, portions in which fibers are combined with a matrix and portions consisting only of the matrix are distributed so as to be arranged alternately in a plane, In addition, since the structure is such that the portions containing only the matrix are continuous in the direction that intersects the plane, for example, with the same fiber content, the coefficient of thermal expansion in the in-plane direction can be maintained at the same low level, while the This has the effect of providing a low thermal expansion and high thermal conductivity composite material that can improve and increase the directional thermal conductivity.

[Brief explanation of the drawing]

FIG. 1 shows (a), (b), and (c) each showing the structure of a low thermal expansion and high thermal conductivity composite material according to an embodiment of the present invention.
(a) is a schematic perspective view, (b) is a schematic plan view, and (C) is a schematic cross-sectional view. FIG. 2 is a schematic diagram showing an example of a manufacturing method for obtaining a composite material according to an embodiment of the present invention, and FIG. 3 is a diagram showing the relationship between thermal conductivity and fiber content of a composite material according to an embodiment of the present invention. Figure 4 is a characteristic diagram showing the relationship between the coefficient of thermal expansion and fiber content of a conventional composite material, and Figure 5 is a diagram showing the relationship between the coefficient of thermal expansion and fiber content of a conventional composite material. FIG. In the figure, (1) is a part where fibers are combined with a matrix, and (2) is a part where only the matrix is used. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In a fiber-reinforced metal that is reinforced quasi-isotropically in a plane, parts where fibers are combined with the matrix and parts with only the matrix are distributed so as to be arranged alternately in the plane, and the parts with only the matrix intersect with the above-mentioned plane. A low thermal expansion and high thermal conductivity composite material characterized by being configured so that it exists in a continuous manner.