JPH0313331A - Composite material variable in coefficient of thermal expansion and heat conductivity - Google Patents

Abstract

PURPOSE:To obtain a composite material whose coefficient of thermal expansion and heat conductivity can be aribitrarily selected corresponding to a use or purpose by integrating a high thermal expansion metal plate with a low thermal expansion metal plate having a large number of piercing holes in its thickness direction and selecting the thickness ratio of both metal plates and the surface area ratio of the exposed high and low thermal expansion metals. CONSTITUTION:A low thermal expansion metal plate having a large number of piercing holes 13 in its thickness direction, for example, a Kovar plate 12 is integrated with a high thermal expansion metal plate, for example, a copper plate 11 in a pressure contact state and the high thermal expansion metal is exposed to the surface of the low thermal expansion metal plate from the piercing holes 13 and, by appropriately selecting the thickness ratio of both metal plates or the exposed area ratio of these metal plates on a main surface, the coefficient of thermal expansion and heat conductivity can be arbitrarily changed. By rolling the high thermal expansion metal plate 11 and the low thermal expansion metal plate 12 having a large number of the piercing holes 13 in its thickness direction in a pressure contact state, an objective composite material 10 is prepared.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application This invention is applicable to materials such as metals, ceramics, S
In order to achieve both good thermal conductivity and consistency in thermal expansion coefficient with other materials such as semiconductors such as i and plastics,
This is a composite material whose thermal expansion coefficient and thermal conductivity can be arbitrarily changed. A high thermal expansion metal plate is integrated with a low thermal expansion metal plate having many through holes in the thickness direction, and the high thermal expansion metal is passed through the through holes to form a low thermal expansion metal plate. Thermal expansion coefficient and thermal conductivity can be changed arbitrarily by exposing the metal plate surface and appropriately selecting the thickness ratio of these metal plates and the exposed area ratio of these metal plates on the main surface. Concerning variable rate composite materials.

Background Art Integrated circuit chips (hereinafter referred to as chips) in semiconductor packages, especially LSIs and ULSIs for large computers,
The trend is toward higher integration and faster calculation speeds, and the amount of heat generated during operation is increasing due to increased power consumption.

In other words, chips have become larger in capacity and generate more heat, and if the coefficient of thermal expansion of the substrate material is significantly different from that of the chip material, such as silicon or gallium arsenide, there is a problem that the chip may peel off or crack. .

Along with this, the design of semiconductor packages has also begun to take heat dissipation into consideration, and the substrate on which the chip is mounted is also required to have heat dissipation, and the substrate material is required to have high thermal conductivity. There is.

Therefore, the substrate is required to have a coefficient of thermal expansion close to that of the chip and a high thermal conductivity. As a conventional semiconductor package, one having the configuration shown in FIG. 12a is known.

In other words, the Mo material (2) has a coefficient of thermal expansion close to that of the chip (1).
) and the Kovar alloy material (4), which has a thermal expansion coefficient close to that of the alumina material (3) that makes up the package substrate, are laminated together by brazing, the chip is mounted on the Mo (2) material, and the Kovar alloy material (4) is laminated.
) is connected to the package substrate via a heat dissipation fin (5).

In this configuration, the alumina material (3) and the Kovar alloy material (4) have similar coefficients of thermal expansion, so there is little risk of peeling or cracking, but the material that dominates heat dissipation is the Kovar alloy material with low thermal conductivity. (4), so the radiation fin (5
), there was a problem that sufficient heat dissipation could not be obtained.

Therefore, as a material that satisfies the conflicting demands of having consistency with the coefficient of thermal expansion of the chip and having high thermal conductivity, composite materials for heat dissipation substrates such as clad plates and Cu-Mo or Cu-W alloys have been developed. Proposed.

As the clad plate for the heat dissipation board, a material made by laminating a copper plate and an invar alloy plate is used.

In other words, since copper has good thermal conductivity but a large coefficient of thermal expansion, the clad plate has an invar alloy layered and pressure welded to suppress this, so that thermal expansion in the longitudinal direction of the plate is similar to that of semiconductor elements. This is to obtain consistency.

Furthermore, by adopting a sandwich structure in which invar alloy plates are laminated and pressure bonded to both sides of a copper plate, the structure prevents warping due to temperature rise.

This clad plate can be made to have almost the same coefficient of thermal expansion as the chip, but the thermal conductivity in the thickness direction is
Similar to the structure shown in FIG. 12a, since an invar alloy plate is interposed, this is not necessarily sufficient.

On the other hand, Cu-Mo and Cu-W alloy substrates are produced by sintering Mo and W powders, which have approximately the same coefficient of thermal expansion as the chip, to create a sintered body with a high porosity, and then impregnating it with molten copper. (Japanese Unexamined Patent Publication No. 59-141247), or by sintering Mo, W powder* and copper powder (Japanese Unexamined Patent Publication No. 62-294147). It is a complex of Cu.

When this composite substrate (6) is attached to a package, as shown in FIG. It has a structure in which a flange part (7) is attached and heat is radiated by a turning part.

Although the above-mentioned composite has a thermal expansion coefficient and thermal conductivity that meet practically satisfactory conditions, it is heavy due to the high density of Mo, W, etc., and must be sliced to obtain the desired dimensions. , processing costs were high and yields were poor. Furthermore, due to the structure of the composite, there were many variations in the thermal conductivity of the materials, and the mechanical formability was poor, resulting in problems in manufacturability.

Furthermore, the lead frame in a plastic package must also match the coefficient of thermal expansion with the material to which it is attached and improve its thermal conductivity.

In a resin-sealed semiconductor package as shown in Figure 13, the lead frame not only serves as a path for electrical connections to the outside of the chip, but also plays an important role as a path for the heat generated in the chip. .

That is, in a semiconductor package, a chip (94)
is placed on the island (91) formed in the center of the lead frame (90) and fixed with brazing material, adhesive, solder, etc., and the stitch (92) (inner lead part) and bonding wire ( 95), and the periphery is further sealed with resin (96).

The heat generated from the chip (94) is transferred to the island (91)
, the resin (96), and the stitches (92) to reach the lead portion (93) of the lead frame (90) and be dissipated to the outside.

Therefore, the lead frame (90) is desired to be made of a material with good thermal conductivity in order to dissipate the heat generated from the chip to the outside of the semiconductor package.

On the other hand, peeling of the adhesive interface between the chip (94) and the island (91), cracks observed in the resin (96), etc.
This occurs due to the difference in thermal expansion coefficient between the chip (94) and the resin (0).
It is essential that the thermal expansion coefficients of the lead frame (96) and the lead frame (90) match.

As mentioned above, lead frames in semiconductor packages have traditionally been made of Ni-Fe alloy, which has a low coefficient of thermal expansion such as 42% Ni-Fe alloy, in order to match the coefficient of thermal expansion with the chip.
Fe-based alloys are often used.

However, Ni--Fe alloys have poor thermal conductivity, and therefore do not have sufficient thermal grazing properties to meet current requirements.

In addition, the difference in thermal expansion between the chip and the sealing resin is very large.
Even when the lead frame and the chip have good matching in thermal expansion coefficient, the matching between the lead frame and the resin is poor, and it is difficult to completely prevent cracks from occurring in the sealing resin.

Furthermore, from the viewpoint of heat dissipation, a semiconductor package has been proposed that uses a lead frame made of a copper alloy with good thermal conductivity.

However, copper alloys have poor thermal expansion coefficient compatibility with chips, making it impossible to prevent peeling of the adhesive interface between chips and islands, making it difficult to create stable and reliable semiconductor packages for industrial-scale mass production. It has not yet been supplied.

Purpose of the Invention As clarified in the above-mentioned example of the heat dissipation problem in semiconductor packages, the present invention provides excellent thermal expansion coefficient matching with the thermal expansion coefficient of the bonding material such as a chip or sealing resin, and a heat conductive material. The objective is to provide a composite material whose thermal expansion coefficient and thermal conductivity can be arbitrarily selected depending on the use and purpose, such as good properties.

This invention provides, for example, a heat dissipating substrate for semiconductor packages that has excellent thermal expansion coefficient consistency and high thermal conductivity when mounting a semiconductor chip, has excellent processability and manufacturability during mounting, and can be provided at a low cost. The purpose of the present invention is to provide a composite material with variable thermal expansion coefficient and thermal conductivity that can be used as a composite material.

Summary of the Invention As a result of various studies aimed at creating a metal material that can ensure consistency in thermal expansion coefficient and heat dissipation according to the mating material and has excellent manufacturability, the present invention has been developed by forming a high thermal expansion metal plate with a large number of layers in the thickness direction. Pressure-welding a low thermal expansion metal plate having a through hole, exposing a high thermal expansion metal to the surface of the low thermal expansion metal plate from the through hole,
By appropriately selecting the thickness ratio of these metal plates and the exposed area ratio of these metal plates on the main surface, the thermal expansion coefficient and thermal conductivity can be changed arbitrarily, and there are many high thermal expansion metal plates in the thickness direction. The inventors have discovered that the desired composite material can be easily produced by pressure rolling a low thermal expansion metal plate having through-holes.

That is, in the present invention, a low thermal expansion metal plate having a large number of through holes in the thickness direction is integrated with at least one main surface of a high thermal expansion metal plate, and the high thermal expansion metal is applied to the surface of the low thermal expansion metal plate from the through holes. Consisting of exposed composition.

Select the thickness ratio of these metal plates and the exposed surface area ratio of high thermal expansion metal and low thermal expansion metal, and determine the thermal expansion coefficient and! Alternatively, it is a composite material with variable thermal expansion coefficient and thermal conductivity, which is characterized by changing thermal conductivity to a required value.

For example, Ni-Fe can be applied to the bidirectional surface of a high thermal expansion metal plate such as Cu.
A low thermal expansion metal plate such as a Ni-Co-Fe alloy or a Ni-Co-Fe alloy is integrated, and a large number of through holes are provided in the thickness direction of the low thermal expansion metal plate on at least one of the principal surfaces, and the high thermal expansion metal is passed through the through holes at a low temperature. By exposing the material to the surface of the expanded metal plate, a composite material with variable thermal expansion coefficient and thermal conductivity can be obtained, such as a heat dissipating substrate for mounting a chip.

Structure of the Invention This invention integrates a high thermal expansion metal plate with a low thermal expansion metal plate having a large number of through holes in the thickness direction, and exposes the high thermal expansion metal on the surface of the low thermal expansion metal plate from the through holes. The coefficient of thermal expansion can be changed arbitrarily by selecting the thickness ratio of the plate, using a high thermal conductivity metal as the high thermal expansion metal, and appropriately selecting the area ratio of the exposed high thermal expansion metal on the surface of the low thermal expansion metal plate. The thermal conductivity can be changed arbitrarily by changing the thermal conductivity, and by selecting the materials and combinations of the high thermal expansion metal plate and the low thermal expansion metal plate, as well as selecting the thickness ratio and exposed area ratio, it can be used to suit various uses and purposes. It is possible to set the thermal expansion coefficient and thermal conductivity, and it is possible to provide a wide variety of composite materials.

The variable thermal expansion coefficient and thermal conductivity composite material according to the present invention is produced by laminating a low thermal expansion metal plate on one or both sides of a high thermal expansion metal plate or partially laminating a low thermal expansion metal plate on one or both sides. Fully or partially on both sides of a high thermal expansion metal plate in which through holes are arranged at required intervals and in a pattern, or partially on both sides of a high thermal expansion metal plate without through holes on one side of the laminated low thermal expansion metal plate, Laminate low thermal expansion metal plates made of the same or different materials. Apply coating treatment such as plating to change the hole size, pattern, etc. of the through holes in the laminated low thermal expansion metal plates on both sides of the high thermal expansion metal plate. By selecting and combining methods such as partial application, it is possible to set the thermal expansion coefficient and thermal conductivity of the whole or part of the composite material according to the application and purpose. A composite material can be obtained that is compatible with the coefficient of thermal expansion of a mating material such as a semiconductor or plastic, and has the required thermal conductivity.

For example, if the coefficient of thermal expansion that matches the chip and the coefficient of thermal expansion that matches the sealing resin are different, the area occupancy factor of the high thermal expansion metal plate on the surface of the low thermal expansion metal plate where the chip is placed, or the low thermal expansion By changing the conditions such as the thickness of the metal plate and the conditions of the surface directly in contact with the sealing resin on the back side as described above, the thermal characteristics of each main surface can be approximated to the required values.

In addition, in a sandwich structure in which low thermal expansion metal plates are laminated on both sides of a high thermal expansion metal plate, the core material is a laminate of high thermal expansion metals, and the high thermal expansion metal is exposed to the surface through the through hole of the low thermal expansion metal plate. Various configurations can be taken, such as.

The difference in thermal expansion coefficient between the high thermal expansion metal plate and the low thermal expansion metal plate does not necessarily have to be large, and any metal plates can be combined depending on the purpose as long as their thermal expansion coefficients are different.

The coefficient of thermal expansion of the composite material according to the present invention is determined by the volume ratio of the high thermal expansion metal plate and the low thermal expansion metal plate, that is, the thickness ratio of the laminate. It is possible to select any value.

For example, the thermal expansion coefficient a for existing chips to be unaffected by thermal strain is 5 to 9xlO at room temperature to 900°C.
-6/'C, more preferably,
4 to 8 x 10-6/''C.

In the case of the heat dissipation board for chip mounting, the average coefficient of thermal expansion at 30°C to 200°C is 10xlO.
-6/”C or less Ni-Fe alloy, Ni-Co-Fe
Low thermal expansion metal plates such as alloys, and Cu whose average coefficient of thermal expansion at 30°C to 200°C exceeds 10xlO-6/”C
A high thermal expansion metal plate such as a Cu alloy or the like can be used in combination, and it is particularly desirable that the high thermal expansion metal plate has a thermal conductivity of 140 W/m or more at 20°C. Further, it is desirable to appropriately select the area ratio of the high thermal expansion metal plate on the surface of the low thermal expansion metal plate within a range of 20 to 80%.

Since high thermal expansion metal plates are press-fitted into through holes of low thermal expansion metal plates by pressure welding, forging, etc., materials with high malleability such as Cu, Cu alloy, AI, A1 alloy, steel, etc. should be used. is preferred.

In addition, the low expansion metal plate has a malleable MO130 to 5
Ni-Fe alloy containing 0 wt% Ni, 25-35
Ni-Co containing wt% Ni, 4-20 wt% Co
-Fe-based alloy, W, etc. can be used.

The manufacturing method includes, for example, drilling a large number of through holes in the thickness direction at desired positions of a low thermal expansion metal plate, cleaning the adhering surface, and cold-pressing the low thermal expansion metal plate and the high thermal expansion metal plate. , further improves adhesion by applying diffusion heat treatment, etc.
Known pressure welding, rolling or forging techniques can be used,
It is possible to provide a composite material with stable properties even when mass-produced on an industrial scale.

In addition, the shape and arrangement of the high thermal expansion metal exposed on the surface of the low expansion metal plate in the composite material of the present invention can take various forms depending on the purpose or manufacturing method as described above. It is advantageous to reduce product variations, and is usually 3 mm or less, preferably 1 m.
m or less, more preferably 0.5 balls or less.

In addition, in addition to mechanical processing such as press punching, chemical processing such as etching can be used to form through holes in the thickness direction of low thermal expansion metal plates. Various shapes such as a straight or tapered surface can be adopted, and when the surface is tapered, it can be easily press-fitted into the through hole and the bonding strength can be increased.

Furthermore, when using the composite material of the present invention, brazing is performed to improve the properties and corrosion resistance, or to improve the adhesion of Au and Ag plating.
, plating layers of various metals such as solder can be applied to required parts.

The composite material of this invention has a unique coefficient of thermal expansion and thermal conductivity due to the above-mentioned configuration, but furthermore, the composite material of this invention having different coefficients of thermal expansion and thermal conductivity is laminated in the thickness direction, and an arbitrary Thermal expansion coefficient and thermal conductivity can be set.

In addition, after arranging a large number of through holes in the plate thickness direction in a low expansion metal plate, and after cold pressure welding the low expansion metal plate and a high thermal expansion metal plate, the high thermal expansion metal plate adhered to one side of the low expansion metal plate is When the expansion metal plate is removed by a known surface grinding method or the like, it is possible to obtain a composite material made of a plate-shaped low expansion metal in which only the through holes are filled with high thermal expansion metal plates to a large extent.

Based on the Drawings (Disclosure of the Invention) FIGS. 1 to 6 are perspective explanatory views showing embodiments of the composite material according to the present invention.

FIGS. 7 and 8 are perspective explanatory views showing one embodiment of the method for manufacturing a composite material according to the present invention.

FIG. 9 is a cross-sectional explanatory diagram illustrating the heat dissipation effect of the heat dissipation board manufactured using the composite material according to the present invention.

In the following description, a copper plate is used as a high thermal expansion metal plate, and Kovar (Fe-Co-Ni alloy) is used as a low thermal expansion metal plate.
An example using a board will be explained.

Composite materials (10), (20), (
30) are all copper plates (11), (21), (31)
Kovar plates (12), (22), and (32) having a large number of through holes in the thickness direction are pressed onto both sides of the plate.

The composite material (10) in FIG.
) are dispersed over the entire surface of the cladding material (10).

The material (20) in Fig. 2 has a structure in which the exposed surface (24) of the copper plate exposed on the surface of the Kovar plate (22) through the through hole (23) is distributed in stripes on both main surfaces of the material (20). .

The material (30) in Fig. 3 has one group of exposed surfaces (34) of the copper plate exposed on the surface of the Kovar plate (32) through the through holes (33) on both main surfaces of the material (30) in the longitudinal direction. It consists of a discontinuously distributed configuration.

In any of these configurations, the copper plates (11), (2
Kovar plate (12) pressed against both sides of 1) and (31)
, (22), and (32) and the dispersion state of the exposed surface (14) (24×34) of the exposed copper plate, etc., the thermal characteristics of each principal surface are approximated to the required characteristics. I can do that.

The configuration shown in FIGS. 2 and 3 shows a configuration in which exposed surfaces of the copper plate are distributed on the front and back sides of required portions, allowing partial heat dissipation.

The composite material (40) shown in Fig. 4 is made by pressing Kovar (42) in a strip-like manner onto the central part of both sides of a copper plate (41). ) is partially arranged.

According to this configuration, it is only necessary to consider the consistency of the coefficient of thermal expansion of the abutting portion of the mating material, and the heat dissipation of the entire material is extremely good.

The composite material (50) shown in FIG. 5 is made of Kovar plates (52a
), but one Kovar plate (52a
), and the exposed surface (54) of the copper plate is partially arranged at required locations on the main surface.

The composite material (60) shown in Fig. 6 is produced by press-welding a Kovar plate (62) having through holes (63) only on the main surface of a copper plate (61), so that the exposed surface (64) of the copper plate is completely covered at required points. This is the configuration arranged in.

The configurations shown in FIGS. 5 and 6 can further increase the difference in thermal properties between the front and back sides of the material by setting the presence or absence of the exposed surface of the copper plate and the presence or absence of the Kovar plate.

To explain the manufacturing method of the composite material (10) having the structure shown in Fig. 1, as shown in Fig. 7, a pair of Kovar plates (12
In X12), punching is performed in advance using a press, for example, a large number of small holes are punched to form a mesh shape, and after annealing, surface treatment is performed and winding is performed into a coil.

A copper plate (11) coil having the required dimensions and thickness is unwound, and the unwound Kovar plates (12) are overlapped from above and below and rolled and joined by a rolling roll (70).

As a result of pressure welding, as shown in Figure 1, Kovar plate (12)
Copper enters into the numerous through holes (13), and the exposed surface (14) of the copper plate (11) is partially arranged and formed at a predetermined position of the Kovar plate (12).

Next, by diffusion annealing this composite material, the adhesion can be further improved.

In addition, in order to manufacture the composite material (60) in which the Kovar plate (62) is pressed only on the main surface of the copper plate (61) shown in Fig. 6, punching with a press is performed in advance as shown in Fig. 8. Kovar plate (62) and Cu unwound from above
It is preferable to overlap the plates (61) and roll them together using a rolling roll (70).

When the composite material obtained by the method shown in FIG. 7 is processed into a heat dissipating substrate (80) by a known method and a semiconductor package is assembled, the part on which the chip (1) is placed is shown in FIG. is substantially covered by the Kovar plate (82), so it has good thermal consistency, and the through hole (83) of the Kovar plate (82)
) The exposed surface (84) of the copper (81) is partially exposed through the
) can efficiently absorb heat and dissipate it to the outside of the package.

In addition, the lower surface also has a thickness of the Kovar plate (82) and an exposed surface (81) of the copper (81) in accordance with the thermal expansion coefficient of other contact materials.
By adjusting the area ratio of 4), thermal matching can be improved.

As mentioned above, the heat dissipation board using the composite material of the present invention can be obtained in the form of a plate with predetermined dimensions by rolling and pressure welding.
There is no need to use complicated processing methods such as slicing to finish to a predetermined thickness, and it has the advantage that it can be manufactured at low cost, has excellent cutting workability, and can be easily processed depending on the package substrate or chip.

Example: A pair of Kovar plates (2
9Ni-16Co-Fe alloy), each with a pore size of 1. Omm
, a large number of holes were made with a hole spacing of 1.5 mm, and 90
After annealing at 0°C, wire brushing was performed. The average coefficient of thermal expansion of Kovar plate at 30-200°C is 5.2x
It was lO-6rC.

Further, a Cu plate having a thickness of 1.2M and a width of 30mm was similarly annealed and wire brushed. 30~ of Cu board
The average coefficient of thermal expansion at 200°C is 17.2xlO-
It was 6/'C.

The Kovar plate and the Cu plate were pressure-welded using a cold pressure welding machine shown in FIG. 7 to obtain a composite material with a plate thickness of 0.7 mm. The rolling ratio was 61%.

That is, copper entered the through holes of the Kovar plate during cold welding, and a composite material as shown in FIG. 1 was obtained in which the surface of the copper plate was partially exposed at a predetermined position on the surface of the Kovar plate.

This composite material was diffusion annealed at 800° C. for 5 minutes to be joined and integrated.

The Cu exposed surface on the main surface of the obtained composite material had an elliptical shape elongated in the rolling direction, the hole interval was 1.0 dish in the rolling direction, and the ratio of the Cu exposed surface to the Kovar plate was 35%.

The thermal conductivity of the obtained material in the thickness direction is 300 w/m-K, and the coefficient of thermal expansion on each principal surface is 8.
xlO-6/''C.

This composite material was cold-rolled to a thickness of 0.25 mm, and then processed into a lead frame using a known method to fabricate a semiconductor package. There were no cracks in the resin, and good heat dissipation properties similar to those of conventional lead frames using copper alloys were obtained.

Example 2 Manufacturing was carried out in the same manner as in Example 1 using the composite material (0.7 mm) obtained in Example 1, a 36Ni-Fe alloy plate and a Mo plate as the low thermal expansion metal plate, and a Cu plate as the high thermal expansion metal plate. The thermal expansion properties of the composite materials obtained by the method were measured. The measurement results are shown in FIGS. 10a and 10b, which are graphs of the relationship between the coefficient of thermal expansion and temperature.

As shown in FIG. 10a, it is clear that the composite material according to the invention made of 36Ni-Fe alloy and Cu plate has thermal expansion characteristics similar to that of Si.

In addition, as shown in Figure 1O, 29Ni-16Co-F
The composite material according to this invention consisting of an e-alloy plate and a Cu plate is
It is clear that it has thermal expansion characteristics similar to Al2O3. Furthermore, the composite material according to the present invention consisting of a Mo plate and a Cu plate has thermal expansion characteristics very similar to that of Mo alone, and as will be shown in Example 3, the thermal conductivity is significantly improved compared to Mo alone. are doing.

In the combination of the high thermal expansion metal plate and the low thermal expansion metal plate shown in Example 2, the hole diameter and hole interval of the through holes formed in the low thermal expansion metal plate were varied, and the surface of the low thermal expansion metal plate of each composite material was changed. The relationship between the area ratio of the Cu material and the thermal conductivity was measured. The measurement results are shown in the graph of the relationship between thermal conductivity and Cu exposed area ratio in FIG. 11.

The larger the exposed area of the high thermal expansion metal, the better the thermal conductivity can be obtained, but considering workability etc., the area ratio is 20 to 8.
It is desirable that the area ratio is within the range of 0%, and when a composite material made of a 36Ni-Fe alloy and a Cu plate is used as a heat dissipation board, the area ratio is 35% or more, and in a composite material made of a 29Ni-16Co-Fe alloy plate and a Cu plate, it is 30%. % or more is desirable.

Furthermore, as described in Example 2, the composite material according to the present invention consisting of a Mo plate and a Cu plate has thermal expansion characteristics very similar to that of Mo alone, but has significantly improved thermal conductivity.

[Brief explanation of the drawing]

1 to 6 are perspective explanatory views showing examples of the composite material according to the present invention. FIGS. 7 and 8 are perspective explanatory views showing one embodiment of the method for manufacturing a composite material according to the present invention. FIG. 9 is a cross-sectional explanatory diagram illustrating the heat dissipation effect of the heat dissipation board manufactured using the composite material according to the present invention. FIGS. 10a and 10b are graphs showing the relationship between the coefficient of thermal expansion and temperature of the composite material according to the present invention. FIG. 11 is a graph showing the relationship between the thermal conductivity and the Cu exposed area ratio of the composite material according to the present invention. FIGS. 12a and 12b are longitudinal sectional views of a package showing a conventional heat dissipation board. FIG. 13 is a schematic diagram of a semiconductor package. 1... Chip, 2... Mo material, 3... Alumina material, 4... Kovar material, 5... Radiation fin, 6...
Composite substrate, 7...7 langouse, 10, 20, 30,
40,50.60...Composite material, 11.21,31,
41,51,61...Copper plate, 12.22,32,42
, 52a, 52b, 62.82-Kovar plate, 13.2
3, 33, 43, 53, 63, 83... through hole, 14
．． 24, 34, 44, 54, 64, 84...exposed surface,
70... Rolling roll, 80... Heat dissipation board, 81...
- Copper, 90... Lead frame, 91... Island, 92... Stitch, 93... Lead part, 94... Chip, 95... Bonding wire, 96... Resin.

Claims (1)

[Scope of Claims] 1. A low thermal expansion metal plate having a large number of through holes in the thickness direction is integrated into at least one principal surface of a high thermal expansion metal plate, and the high thermal expansion metal flows from the through holes to the surface of the low thermal expansion metal plate. The thickness ratio of these metal plates and/or the surface area ratio of exposed high thermal expansion metal and low thermal expansion metal are selected to change the thermal expansion coefficient and/or thermal conductivity to a required value. A composite material with variable thermal expansion coefficient and thermal conductivity.