WO2019138744A1

WO2019138744A1 - Composite member, heat-radiation member, semiconductor device, and method for manufacturing composite member

Info

Publication number: WO2019138744A1
Application number: PCT/JP2018/044895
Authority: WO
Inventors: 功岩山; 山本　剛久; 小山　茂樹; 祐太井上
Original assignee: 住友電気工業株式会社; 株式会社アライドマテリアル
Priority date: 2018-01-10
Filing date: 2018-12-06
Publication date: 2019-07-18
Also published as: JP7086109B2; JPWO2019138744A1

Abstract

This composite member includes a substrate formed of a composite material which contains metal and nonmetal, the substrate being provided with: a large warpage portion which is provided on one side of the substrate and has a spherical warpage having a curvature radius R; and a small warpage portion which is partially provided on the large warpage portion and has a warpage different in size from the curvature radius R, wherein the curvature radius R is 5000-35000 mm, the thermal conductivity of the substrate is 150 W/m·K or more, and the linear expansion coefficient of the substrate is 10 ppm/K or less.

Description

Composite member, heat radiating member, semiconductor device, and method of manufacturing composite member

The present disclosure relates to a composite member, a heat dissipation member, a semiconductor device, and a method of manufacturing the composite member. This application claims priority based on Japanese Patent Application No. 2018-002166 filed on Jan. 10, 2018. The entire contents of the description of the Japanese patent application are incorporated herein by reference.

Patent Document 1 refers to a magnesium-based composite material (hereinafter referred to as Mg-SiC) in which magnesium (Mg) or a magnesium alloy and silicon carbide (SiC) are combined as a material suitable for a heat dissipation member (heat spreader) of a semiconductor element. May be disclosed.

The heat dissipation member of the semiconductor element is typically a flat plate, one surface of which is a mounting surface of the semiconductor element or the like, and the other surface of which is an installation surface which is fixed to an installation object such as a cooling device. Patent document 1 provides the curvature which the installation surface of the heat dissipation member of Mg-SiC becomes convex, presses a heat dissipation member on installation object so that this curvature may be crushed, fixes with a bolt etc. in this state, and fixes the heat dissipation member. It is disclosed that the object to be installed is brought into close contact by being brought into contact in a pressurized state.

JP 2012-197496 A

The composite member according to the present disclosure is
A substrate made of a composite material containing metal and nonmetal,
The substrate is
A large warpage portion having a spherical warpage with a radius of curvature R provided on the one surface,
And a small warpage portion partially provided in the large warpage portion and having a warpage different in size from the curvature radius R,
The curvature radius R is 5,000 mm or more and 35,000 mm or less,
The thermal conductivity of the substrate is at least 150 W / m · K,
The linear expansion coefficient of the substrate is 10 ppm / K or less.

A method of manufacturing a composite member according to the present disclosure is
Equipped with a pressing process for storing a material plate made of a composite material containing metal and nonmetal and carrying out heat pressing in a forming die,
The mold is
A large spherical surface portion having a spherical surface with a curvature radius Rb, and a small spherical surface portion partially provided on the large spherical surface portion and having a spherical surface having a curvature radius different from the curvature radius Rb;
The curvature radius Rb is 5,000 mm or more and 35,000 mm or less,
The pressing process is
A holding step of holding the heating temperature at 200 ° C. or higher and the applied pressure at 10 kPa or more for a predetermined time;
And a cooling step of cooling from the heating temperature to 100 ° C. or less while maintaining a pressurized state of 80% or more of the applied pressure.

FIG. 1 is a schematic plan view schematically showing a composite member of the embodiment. FIG. 2 is a partial cross-sectional view of the composite member of the embodiment taken along the line (II)-(II) shown in FIG. FIG. 3: is process explanatory drawing explaining the manufacturing process of the thermal radiation member of embodiment. FIG. 4 is an explanatory view for explaining the method of measuring the radius of curvature R, and shows each measurement point for drawing the contour extracted along the contour extraction straight line l _n , the approximate arc, and the distance d between the measurement point and the approximate arc. FIG. 5 is a schematic cross-sectional view schematically showing elements of the semiconductor device of the embodiment. FIG. 6 is a schematic plan view schematically showing another example of the composite member of the embodiment. FIG. 7 is a schematic plan view schematically showing still another example of the composite member of the embodiment.

[Problems to be solved by the present disclosure]
With the increase in output of electronic devices, the amount of heat generated during operation of semiconductor devices provided in electronic devices tends to increase. Therefore, it is desirable that various heat dissipating members such as a heat dissipating member of a semiconductor element and materials thereof be excellent in heat dissipating property.

Even if convex warpage is provided on the entire plate forming the heat dissipating member as described above, the heat dissipating property may be lowered. As one of the reasons, by soldering the insulating substrate which insulates between the heat radiating member and the semiconductor element to the heat radiating member, the bonding portion of the insulating substrate in the heat radiating member is locally deformed, and the convex warpage is It is conceivable to return. The curvature of the convex is less than the initial curvature (protrusion), or it is locally concave, or the curvature radius is larger than the initial curvature, or the accuracy of the spherical surface is And the like. Although the difference in linear expansion coefficient between the heat dissipation member made of a composite material such as Mg-SiC and the insulating substrate made of an insulating material such as aluminum nitride (AlN) is smaller than that when the heat dissipation member is made of metal, A slight difference is considered to cause the above-mentioned local deformation. Even if the heat dissipating member is pressed against the installation object due to this local deformation, a portion where the heat dissipating member can not be brought into close contact with the installation object is generated, which may cause a reduction in heat conductivity to the installation object and consequently a reduction in heat dissipation. .

Further, with the increase in output of electronic devices, it is conceivable to make the insulating substrate thicker in order to improve the electrical insulation between the semiconductor element and the heat dissipation member containing metal. The thicker the insulating substrate, the larger the difference in the amount of thermal expansion and contraction between the heat dissipation member and the insulating substrate, and the above-mentioned local deformation tends to occur. Furthermore, even when a solder having a higher solidus temperature is used as a bonding material for the insulating substrate, the temperature at the time of soldering becomes higher, and the difference in the amount of thermal expansion and contraction tends to be large. Therefore, even if it is a high output use, and a case where an insulating substrate is joined by higher temperature etc., the heat dissipation member which is excellent in adhesiveness with installation object, and is excellent in heat dissipation, and its material are desired.

Therefore, it is an object of the present invention to provide a composite member which is excellent in adhesion to an installation target. Another object of the present invention is to provide a method for producing a composite member capable of producing a composite member excellent in adhesion to an installation target.

Furthermore, it is another object of the present invention to provide a heat dissipating member and a semiconductor device which are excellent in adhesion to an installation object and excellent in heat dissipation.
[Effect of the present disclosure]
The above-mentioned composite member is excellent in adhesion to the installation object. The manufacturing method of said composite member can manufacture the composite member which is excellent in adhesiveness with installation object.
[Description of the embodiment of the present disclosure]
First, embodiments of the present disclosure will be listed and described.
(1) A composite member according to one aspect of the present disclosure is
A substrate made of a composite material containing metal and nonmetal,
The substrate is
A large warpage portion having a spherical warpage with a radius of curvature R provided on the one surface,
And a small warpage portion partially provided in the large warpage portion and having a warpage different in size from the curvature radius R,
The curvature radius R is 5,000 mm or more and 35,000 mm or less,
The thermal conductivity of the substrate is at least 150 W / m · K,
The linear expansion coefficient of the substrate is 10 ppm / K or less.

The spherical warpage means convex warpage.
The warpage of the small warpage portion is a convex warpage that protrudes in the same direction as the warpage of the convexity of the large warpage portion.

The small warpage portion typically has a spherical warpage having a radius of curvature smaller than the radius of curvature R.

The substrate has a form in which the above-mentioned convex warpage is provided on one side thereof, a concave warpage on the other side opposite to it, a form in which the above-mentioned convex warpage is provided on one side, and the other side is flat Etc.

The measuring method of the curvature radius R and the measuring method of the curvature amount of the small curvature part of below-mentioned (2) are mentioned later.
The above-mentioned composite member has a spherical warpage (large warpage portion) of the above-mentioned specific radius of curvature R on one surface of the substrate made of the above-mentioned composite material, and overlaps the spherical warpage portion. It has warpage (small warpage part) of different size in a part of warpage part. If this small warpage portion is used as a bonding portion of the insulating substrate, the small warpage portion locally deforms at the time of bonding of the insulating substrate, so that the substrate in a state where the insulating substrate is bonded has a spherical warpage of radius of curvature R. It is easy to hold uniformly. Even if a semiconductor element or the like is further mounted on the insulating substrate, the spherical warpage can be easily maintained. The substrate in a state in which the insulating substrate is joined and the substrate in a state in which the semiconductor element is mounted on the insulating substrate typically have substantially no small warpage portion, and a spherical surface having a specific radius of curvature R Have a uniform warpage. Therefore, the spherically curved portion is uniformly pressed against the installation object, and a stable close contact state can be secured. Therefore, the above-mentioned composite member is excellent in adhesion to the installation object, particularly after the insulating substrate and the like are joined by the bonding material such as solder. The above-mentioned composite member is provided with a substrate having high thermal conductivity and is excellent in adhesion to the installation object as described above, and therefore, can be suitably used as a heat dissipating member, particularly a heat dissipating member of a semiconductor element. This is because the linear expansion coefficient of the substrate is close to the linear expansion coefficient of the semiconductor element and peripheral parts of the semiconductor element such as the above-described insulating substrate.
(2) As an example of the above composite member,
The curvature radius R is 15000 mm or more and 25000 mm or less,
The amount of warpage of the small warpage portion may be more than 30 μm and 70 μm or less. The measuring method of curvature amount is mentioned later.

In the above embodiment, when the radius of curvature R and the amount of warpage of the small warpage portion satisfy the above-described specific range, the small warpage portion is appropriately deformed at the time of bonding of the insulating substrate, and the small warpage portion is formed on the joined substrate. It is difficult for residual local warping to remain. Therefore, in the above-described embodiment, the substrate in a state in which the insulating substrate or the like is joined is likely to uniformly have a spherical warpage, and the adhesion to the installation object is excellent.
(3) As an example of the above composite member,
The small-curvature portion includes a circular portion in plan view, and the diameter thereof is 5 mm or more and 150 mm or less.

A portion having a circular planar shape in the above embodiment can be said to be a spherical warp portion. Since the small-curvature portion in the above-described form has a spherical curvature, it easily deforms uniformly at the time of bonding of the insulating substrate. Further, if the diameter of the circular portion is within the above specific range, it is close to the outer size of the insulating substrate used for the semiconductor device, and the size of the small warpage corresponds to the size of the insulating substrate. Therefore, the small-curvature portion is more easily deformed. Therefore, in the above-described embodiment, the substrate in a state in which the insulating substrate or the like is joined is likely to uniformly have a spherical warpage, and the adhesion to the installation object is excellent.
(4) As an example of the above composite member,
The form provided with several said small curvature part is mentioned.

The said form is equipped with two or more junction_parts of an insulated substrate, and can be utilized suitably for the thermal radiation member which mounts a several semiconductor element.
(5) As an example of the above composite member,
An embodiment in which the content of the nonmetal is 55% by volume or more is mentioned.

Since the said form has much nonmetallic content, its heat conductivity is higher and it is excellent by heat dissipation. Therefore, the above-mentioned form can be suitably used for a heat dissipation member or the like of a semiconductor element.
(6) As an example of the above composite member,
The metal is magnesium, a magnesium alloy, aluminum or an aluminum alloy,
The nonmetal includes a form containing SiC.

In the above embodiment, when the substrate of Mg—SiC is provided, the heat conduction is lighter than when the substrate of aluminum (Al) or a composite material of aluminum alloy and SiC (hereinafter sometimes referred to as Al—SiC) is provided. The rate is higher and the heat dissipation is better. Moreover, when manufacturing by the manufacturing method of the composite member of the below-mentioned embodiment, the raw material board of Mg-SiC is excellent in the formability by heat press rather than the raw material board of Al-SiC, and is maintained for a relatively short time with high accuracy. Because it can be molded, it is also excellent in manufacturability.

When an Al—SiC substrate is provided in the above embodiment, it is lighter than the case containing copper or silver or an alloy thereof, and is more excellent in corrosion resistance than the case containing magnesium or an alloy thereof.
(7) The heat dissipation member according to one aspect of the present disclosure is
The composite member according to any one of (1) to (6) above,
And an insulating substrate bonded to the small warpage portion via a bonding material,
The curvature radius R of the said board | substrate in the state to which the said insulated substrate was joined is 5000 mm-35000 mm.

As described above, the substrate provided in the heat dissipation member has a reduced warpage of the small warpage portion when the insulating substrate is joined, and has substantially only the large warpage portion when the insulating substrate is joined. That is, this substrate has a spherical warp with the above-mentioned specific radius of curvature R. Even if a semiconductor element or the like is further mounted on this insulating substrate, it is easy to maintain the spherical warpage of the radius of curvature R. Such a heat radiating member as described above can uniformly press the spherical warped portion against the installation object, and can ensure a stable close contact state. Therefore, the above-mentioned heat dissipation member is excellent in adhesion to the installation subject, efficiently transfers heat to the installation subject, and is excellent in heat dissipation. The above-mentioned heat dissipation member can be suitably used as a heat dissipation member of a semiconductor element from the consistency of the coefficient of linear expansion between the substrate and the semiconductor element and its peripheral parts as described above.
(8) A semiconductor device according to an aspect of the present disclosure is:
The heat dissipation member according to (7) above,
A semiconductor element mounted on the insulating substrate;
The curvature radius R of the substrate in a state where the insulating substrate on which the semiconductor element is mounted is joined is 5,000 mm or more and 35,000 mm or less.

The above semiconductor device includes the above-mentioned heat dissipation member (substrate) having a spherical warpage of the above-mentioned specific radius of curvature R when the insulating substrate on which the semiconductor element is mounted is joined, and therefore the adhesion to the installation object Excellent in heat dissipation. Examples of the above semiconductor device include semiconductor modules such as power modules.
(9) As an example of the above semiconductor device,
The spherical error of the said board | substrate in the state by which the said insulated substrate in which the said semiconductor element was mounted was joined is 10.0 micrometers or less. The method of measuring the spherical error will be described later.

The heat dissipating member (substrate) provided in the above embodiment has a spherical error of not less than 10. In addition to the spherical warp having the above-mentioned specific radius of curvature R when the insulating substrate on which the semiconductor element is mounted is joined. Small at 0 μm or less and excellent in spherical precision. So to speak, this heat dissipating member has a true spherical warp. Therefore, the above-mentioned form is more excellent in adhesion with the installation object and further excellent in heat dissipation, since the true-spherical curved portion is uniformly pressed by the installation object.
(10) As an example of the above semiconductor device,
An embodiment in which the thickness of the insulating substrate is 1 mm or more can be mentioned.

The thickness of the insulating substrate provided in the above embodiment is as large as 1 mm or more, and the electrical insulation between the semiconductor element to be heated and the heat dissipation member (substrate) containing metal can be improved. In addition, the heat dissipating member provided in the above-described form has spherical warpage with a specific radius of curvature R as described above in the state where such a thick insulating substrate is joined. Therefore, the above-mentioned form is excellent in adhesion to the installation object, excellent in heat dissipation, and also excellent in electrical insulation with the semiconductor element, and can be suitably used as a semiconductor device for high power applications and the like.
(11) A method of manufacturing a composite member according to an aspect of the present disclosure,
Equipped with a pressing process for storing a material plate made of a composite material containing metal and nonmetal and carrying out heat pressing in a forming die,
The mold is
A large spherical surface portion having a spherical surface with a curvature radius Rb, and a small spherical surface portion partially provided on the large spherical surface portion and having a spherical surface having a curvature radius different from the curvature radius Rb;
The curvature radius Rb is 5,000 mm or more and 35,000 mm or less,
The pressing process is
A holding step of holding the heating temperature at 200 ° C. or higher and the applied pressure at 10 kPa or more for a predetermined time;
And a cooling step of cooling from the heating temperature to 100 ° C. or less while maintaining a pressurized state of 80% or more of the applied pressure.

The manufacturing method of the above-mentioned composite member has a spherical surface (large spherical surface portion) having the above-mentioned specific radius of curvature Rb, and overlaps with this spherical surface, a spherical surface (small spherical surface portion) having a different curvature radius on a part of this spherical surface The heat-pressing is performed on the blank under the specific conditions described above using a mold having As described above, the heating temperature and the applied pressure at the time of heat pressing are relatively high, thereby promoting the plastic deformation of the material plate made of the above-mentioned composite material to form a plurality of warpage shapes by the large spherical portion and the small spherical portion. It can be accurately transferred to the material board. And by performing cooling from a heating temperature at the time of heat pressing to a specific temperature in a pressurized state, it is possible to suppress the shape change and the disorder of the shape that may occur in the cooling in a non-pressured state. The shape can be transferred with high accuracy. On one surface of the substrate, it has a spherical warped portion (an example of the above-mentioned large warped portion) having a radius of curvature close to the radius of curvature Rb formed by the large spherical portion and has a radius of curvature Rs formed by the small spherical portion. It is possible to manufacture a composite member in which a spherically curved portion having an approximate curvature radius (an example of the above-mentioned small-curvature portion) is locally provided, typically the composite member of the above (1). In this composite member, when the warped portion formed by the small spherical portion is used as the bonding portion of the insulating substrate, the substrate after bonding can uniformly have a spherical warpage formed by the large spherical portion. Even if a semiconductor element or the like is further mounted on the insulating substrate, the spherical warpage can be easily maintained. Such a composite member is excellent in adhesion to the installation object as described above.

Furthermore, according to the method of manufacturing a composite member described above, it is possible to release the residual stress and manufacture a composite member having a small residual stress, preferably substantially free of the residual stress. Such a composite member is excellent in adhesion to the installation object as described above, and is not easily deformed even when subjected to a cooling and heating cycle at the time of use, and easily maintains the adhesion state to the installation object. When this composite member is used as a heat dissipation member of a semiconductor element, it has excellent heat dissipation from the initial stage of use over a long period of time.
Details of Embodiments of the Present Disclosure
Hereinafter, embodiments of the present disclosure will be specifically described with reference to the drawings as appropriate.

Within the dashed circle in FIG. 1, the non-metals 22 are exaggerated for clarity. In FIG. 2 and FIG. 3, the small warpage 12 is exaggerated for the sake of easy understanding.

FIG. 2 is a cross-sectional view of the substrate 10 taken along a plane parallel to its thickness direction (a plane parallel to the short side of the substrate 10 which is rectangular here).

In FIG. 5, only the vicinity of the heat dissipation member 3 and the semiconductor element 50 provided in the semiconductor device 5 is schematically shown, and the warped shape of the heat dissipation member 3, bonding wires, packages, cooling devices (targets for installation) and the like are omitted.
[Composite member]
(Overview)
The composite member 1 of the embodiment will be described mainly with reference to FIGS. 1 and 2.

The composite member 1 of the embodiment includes a substrate 10 made of a composite material including a metal 20 and a nonmetal 22 as shown in FIG. The thermal conductivity of the substrate 10 is 150 W / m · K or more, and the linear expansion coefficient is 10 ppm / K or less. On one surface of the substrate 10, as shown in FIG. 2, a large warpage 11 having a curvature of a spherical surface having a curvature radius R of 5000 mm or more and 35000 mm or less is provided. Typically, spherical warpage with a radius of curvature R is provided over most of one surface of the substrate 10, and most of the substrate 10 forms a large warpage 11. Furthermore, on one surface of the substrate 10, a small warpage 12 having a warpage different in size from the radius of curvature R is partially provided in the large warpage 11. The large warpage 11 and the small warpage 12 project in the same direction (downward in FIG. 2), and the substrate 10 has a two-step convex warpage. In FIG. 2, the case where the small-curvature portion 12 has a spherical warpage having a curvature radius smaller than the curvature radius R is illustrated.

When an insulating substrate 52 made of AlN or the like is joined to the small-warped portion 12 with a bonding material 54 (middle view in FIG. 3), the small-warped portion 12 is locally based on the difference with the linear expansion coefficient of the insulating substrate 52, etc. To be deformed. It deforms so that the convex of the small camber 12 is reduced. Due to this local deformation, the shape of the portion where the insulating substrate 52 is joined is likely to be a shape along the large warped portion 11. Further, this local deformation hardly affects the shape of the large warpage portion 11, and the shape of the large warpage portion 11 is substantially easily maintained. As a result, one surface of the substrate 10 to which the insulating substrate 52 is bonded typically has substantially no small warpage 12 and has uniform spherical warpage with a radius of curvature R (see the lower view of FIG. 3). ). Even if the semiconductor element 50 (FIG. 5) is further bonded to the insulating substrate 52 by the bonding material 54 (FIG. 5), the spherical warpage can be easily maintained. The spherically curved portion is uniformly pressed against the installation target (not shown) of the composite member 1 so that the composite member 1 can be brought into close contact with the installation target. If such a composite member 1 is used for the heat dissipation member 3 (FIG. 3), the substrate 10 having high thermal conductivity is in close contact with the installation object, so that heat can be transmitted well to the installation object and heat dissipation is excellent. . In particular, since the substrate 10 has a linear expansion coefficient relatively close to that of the semiconductor element 50 and its peripheral components (eg, the insulating substrate 52 etc.), the substrate 10 can be suitably used as the heat dissipation member 3 of the semiconductor element 50.

A more detailed description will be given below.
(substrate)
The substrate 10 is a main component of the composite member 1 and is a molded body made of a composite material including a metal 20 and a nonmetal 22.
<Metal>
The metal 20 in the substrate 10 is, for example, a so-called pure metal selected from the group of Mg, Al, Ag, and Cu, or an alloy based on one metal element selected from the above group, etc. Can be mentioned. Magnesium alloys, aluminum alloys, silver alloys and copper alloys having known compositions can be used.
<Non-metal>
Various kinds of nonmetals 22 in the substrate 10 have excellent thermal conductivity (eg, 30 W / m · K or more, preferably 150 W / m · K or more) and a linear expansion coefficient smaller than that of the metal 20 (eg, line) Expansion coefficient: 5 ppm / K or less). Examples of the nonmetal 22 include carbides of metal elements or nonmetal elements, oxides, nitrides, borides, silicides, ceramics such as chlorides, nonmetal elements such as silicon (Si), and carbons such as diamond and graphite. Inorganic materials such as raw materials can be mentioned. Specific ceramics include SiC (eg, linear expansion coefficient of 3 to 4 ppm / K, thermal conductivity of single crystal of 390 W / m · K or more), AlN, h-BN, c-BN, B ₄ C, etc. . Multiple types of non-metals 22 can be included.

The nonmetal 22 in the substrate 10 is typically present with substantially maintained the composition, shape, size and the like of the raw material. For example, when powder is used as the raw material, it exists as powder particles in the substrate 10, and when it is used as the raw material, it is present as the molded body in the substrate 10 when it is used. The substrate 10 in which the powder particles are dispersed and present is excellent in toughness. In the substrate 10 in which the porous body is present, the nonmetal 22 is continuously formed in a mesh shape in the substrate 10 to construct a heat dissipation path, so that the heat dissipation is excellent.

The content of the nonmetal 22 in the substrate 10 can be appropriately selected. In many cases, the content tends to increase the thermal conductivity and decrease the linear expansion coefficient as the content increases, or to tend to increase the mechanical properties (eg, rigidity etc.), and thus the improvement in properties can be expected. From the viewpoint of improving the characteristics, the content is preferably 55% by volume or more. When the content is 55% by volume or more, the thermal conductivity is, for example, 150 W / m · K or more (Mg-SiC, Al-SiC, diamond composite material, etc., although it depends on the composition of the metal 20 and the nonmetal 22). Higher for diamond composites), the coefficient of linear expansion tends to satisfy 10 ppm / K or less. The content is, for example, 60% by volume or more, and further 70% by volume or more from the viewpoint of the above-described property improvement and the like. If the content is small to some extent, it is easy to fill the raw material into the mold for forming the composite material or fill the gap between the non-metals 22 with the metal 20 in a molten state, and the productivity of the composite material is excellent. From the viewpoint of manufacturability etc., the content is 90 volume% or less, further 85 volume% or less, and 80 volume% or less.
<Specific example of composite material>
Specific examples of the composite material include Mg-SiC, pure aluminum or aluminum alloy (hereinafter collectively referred to as Al or the like) mainly composed of pure magnesium or magnesium alloy (hereinafter sometimes collectively referred to as Mg etc.) and SiC. And Al—SiC etc. in which SiC is mainly compounded. Examples of the diamond composite material include silver, a silver alloy, Mg or the like, Al or the like, or a composite of copper or a copper alloy and diamond.

Mg—SiC in which the metal 20 is Mg or the like and the nonmetal 22 contains SiC is lighter than the Al—SiC, and has high thermal conductivity and excellent heat dissipation. Moreover, when manufacturing the composite member 1 provided with the board | substrate 10 of Mg-SiC by the manufacturing method of the composite member of embodiment mentioned later, the raw material board of Mg-SiC has the formability by hot press rather than the raw material board of Al-SiC. Since the composite member 1 can be formed with high accuracy in a short time, the productivity of the composite member 1 is also excellent. Furthermore, since Mg and the like are easier to relieve stress than Al and the like, the residual stress can be reduced at a lower temperature and in a shorter time at the time of heat pressing, and the residual stress difference between the front and back of the substrate 10 can be easily reduced. The composite member 1 provided with the substrate 10 in which the residual stress is reduced is not easily deformed even when subjected to a cooling and heating cycle at the time of use, and it is easy to ensure a close contact with the installation object from the initial use for a long time. Al—SiC in which the metal 20 is Al or the like and the nonmetal 22 contains SiC is lighter than the case where silver, copper, or an alloy thereof is contained as the metal 20, and has better corrosion resistance than the case where Mg or the like is contained. The diamond composite material has a very high thermal conductivity and is further excellent in heat dissipation.
<Exterior>
The outer shape of the substrate 10 (here, a planar shape drawn by the outer edge of the substrate 10) is typically a rectangle. When the rectangular substrate 10 is (1) easy to manufacture a material plate, and (2) it is used for the heat dissipation member 3 of the semiconductor element 50, the installation area of the mounting components such as the semiconductor element 50 can be sufficiently secured. Have an advantage. The outer shape of the substrate 10 can be changed according to the application, the shape / number of the mounting components, the installation object, and the like. In FIG. 1, the case where the external shape of the board | substrate 10 is a rectangle is illustrated.
<Size>
The size of the substrate 10 can be appropriately selected in accordance with the application, the mounting area of the above-described mounting component, and the like. For example, it takes a rectangle containing the outer shape of the substrate 10 (if the outer shape of the substrate 10 is a rectangle, the contained rectangle substantially matches the outer shape of the substrate 10), and the long side of this rectangle is 100 mm or more If the length of the short side is 50 mm or more, the mounting area is large, and the large-sized heat dissipation member 3 can be constructed. The length of the long side may be 150 mm or more, and the length of the short side may be 120 mm or more. Even in the case of the large substrate 10, since the large warped portion 11 and the small warped portion 12 are provided, the semiconductor element 50 is mounted on the composite member 1 in which the insulating substrate 52 is joined as described above. The composite member 1 in the closed state can be closely attached to the installation target.

The thickness t (FIG. 2) of the substrate 10 can be selected as appropriate. When the composite member 1 is used for the heat dissipation member 3, the thickness t is preferably 10 mm or less, more preferably 6 mm or less, and 5 mm or less, because the thinner the thickness t, the better the heat conduction to the installation object. If the thickness t is somewhat thick, the heat dissipation is enhanced by thermal diffusion in the lateral direction (the direction orthogonal to the thickness direction), and the thicker the layer is, the easier it is to increase the strength as a structural material. It is mentioned that it is 1.5 mm or more.
<Warp>
<< large warpage part >>
In the composite member 1 according to the embodiment, a large warpage 11 having a spherical warpage with a radius of curvature R of 5000 mm (5 m) or more and 35000 mm (35 m) or less is provided on one surface of the substrate 10. As a representative example of the substrate 10, as shown in FIG. 2, a form having a convex warpage on one surface (the lower surface in FIG. 2) and a concave curvature corresponding to the other surface facing the other surface (the upper surface in FIG. 2) can be mentioned. As another board | substrate 10, it has convex curvature (The convex curvature of 2 steps | paragraphs of the large curvature part 11 and the small curvature part 12) on one surface, and the spherical surface form whose other surface is a flat surface is mentioned. In any form, when using the composite member 1 as the heat dissipation member 3 and the like of the semiconductor element 50, one surface having convex warpage is the installation surface on the installation object, and the other surface is the mounting surface of the mounting component such as the semiconductor element 50. Can be mentioned.

When the radius of curvature R satisfies the above-described specific range, the amount of warpage of the large warpage 11 is appropriate, and the amount of the warpage can be easily maintained after the bonding of the insulating substrate 52 and even after the semiconductor element 50 is mounted. . As a result, after bonding the insulating substrate 52 and the like, the warped portion is uniformly pressed against the installation object, and the substrate 10 is brought into close contact with the installation object. In addition, when the radius of curvature R satisfies the above-described specific range, the substrate 10 is less likely to be deformed with time even if it is subjected to a cooling and heating cycle at the time of use. From these viewpoints, the curvature radius R may be 6000 mm or more, further 7000 mm or more, 8000 mm or more, 34000 mm or less, 33000 mm or less, 32000 mm or less, or 25000 mm or less.

Further, it is preferable that the center of spherical warpage in the large warpage portion 11 be in the vicinity of the center of gravity G in the outer shape of the substrate 10. As described above, when the warped portion of the substrate 10 is pressed against the installation target, the pressing force can be easily applied uniformly to the substrate 10, and the substrate 10 can be easily adhered to the installation target. The center of gravity G is a point corresponding to the center of the planar shape drawn by the outer edge of the substrate 10. If the outline of the substrate 10 is rectangular as described above, the center of gravity G corresponds to the intersection of the diagonals of this rectangle.
<< Small warpage part >>
In the composite member 1 according to the embodiment, in addition to the large warpage 11 described above on one surface of the substrate 10, the small warpage 12 is provided on a part of the large warpage 11. The small warpage 12 has a size different from the radius of curvature R, and protrudes from the large warpage 11 having the radius of curvature R in the same direction as the large warpage 11 so as to project a predetermined amount (a warpage amount x described later) Have.

The small-curvature portion 12 preferably includes a spherically-shaped warped portion having a curvature radius smaller than the curvature radius R. This is because deformation is likely to occur uniformly when the insulating substrate 52 is bonded. As an example of the form in which the small-curvature part 12 includes a spherically-shaped warped part, as shown in FIG. 1, a form in which the entire small-warped part 12 has a spherical-shaped warpage can be mentioned. The small warpage 12 in this form is circular in plan view. The composite member 1 in which the small-curvature portion 12 includes a spherically-shaped warped portion can easily form the spherically-shaped warped portion with high accuracy when the method for manufacturing a composite member according to an embodiment described later is used.

As another example of the embodiment in which the small-curvature portion 12 includes the above-described spherically-shaped warped portion, the planar shape of the small-curvature portion 12 can be a shape formed by partially overlapping a plurality of circles, that is, an arc and a chord (straight line) The form etc. which are the shape which combined are mentioned are mentioned. As such a planar shape, the snowball-like illustrated in FIG. 6, the petal-like illustrated in FIG. 7, etc. are mentioned. The three-dimensional shape of the small-curvature portion 12 has a spherical surface in which a part of a plurality of spherical crowns is missing and connected. Further, the small-curvature portion 12 includes a circular portion in plan view (see a circle 120 in FIGS. 6 and 7 described later).

It can be mentioned that the diameter D of the circular portion provided in the small-curvature portion 12 is 5 mm or more and 150 mm or less in plan view (FIG. 1). If the diameter D is in this range, the outer dimension of the insulating substrate 52 used for the semiconductor device 5, for example, the long side length, the short side length, and the diagonal length of the insulating substrate 52 having a rectangular planar shape Close to at least one of the When the diameter D of the small-warped portion 12 and the outer dimension of the insulating substrate 52 are close, the small-warped portion 12 is more easily deformed at the time of bonding of the insulating substrate 52, and the substrate 10 after bonding has a spherical shape with radius of curvature R Easy to have a warp. As the diameter D is closer to the length of the diagonal of the outer dimension, the small warpage 12 is more easily deformed at the time of bonding the insulating substrate 52, which is preferable. Although depending on the size of the insulating substrate 52, the diameter D may be 10 mm or more and 70 mm or less.

Alternatively, the diameter D may be equal to or greater than the diameter of the inscribed circle inscribed in the contour line (rectangular in FIG. 1) of the planar shape of the insulating substrate 52 and equal to or less than the diameter of the circumscribed circle circumscribed to the contour line. The diameter D satisfying this range is close to the outer size of the insulating substrate 52, particularly the above-mentioned diagonal line, and the small warpage 12 is more likely to be deformed more appropriately when the insulating substrate 52 is bonded as described above. FIG. 1 illustrates the case where the diameter D is substantially equal to the diameter of the inscribed circle.

Alternatively, the outline of the small-curved portion 12 may be an arc of an inscribed circle inscribed in the outline of the insulating substrate 52 (in FIG. 1, a rectangle) or a circumscribed circle inscribed in the outline of the insulating substrate 52. And arcs of concentric circles of the inscribed circle. In plan view, the size of the small-curvature portion 12 having the contour including the above-mentioned arc is close to the outer dimension of the insulating substrate 52, particularly the length of the above-mentioned diagonal, and small warpage when bonding the insulating substrate 52 as described above. It is preferable that the portion 12 is more easily deformed. FIG. 1 shows the case where the outline of the planar shape of the small-curvature portion 12 includes the arc of the inscribed circle, in particular, the case where the contour line coincides with the inscribed circle. In FIG. 6, the case where the said outline of the small curvature part 12 contains the circular arc of the concentric circle of the said inscribed circle is shown. In FIG. 7, the case where the said outline of the small curvature part 12 includes the circular arc of the said circumscribed circle is illustrated.

The composite member 1 can include one or more small warps 12 on the substrate 10. When the composite member 1 is used for the heat dissipation member 3 of the semiconductor element, the small-curvature portion 12 is used for the bonding portion of the insulating substrate 52 on which the mounted component such as the semiconductor element 50 is mounted. Therefore, the number of the small-curvature portions 12 may be selected according to the number of the semiconductor elements 50 (the insulating substrates 52). When the composite member 1 is provided with a plurality of small warpages 12 as illustrated in FIG. 1, it can be suitably used for the heat dissipation member 3 on which a plurality of semiconductor elements are mounted. In a configuration in which a locally warped portion (curved portion) continues to the large warped portion 11 as in the above-described snowball or the like, the number of curved portions is the number of small warped portions 12. FIG. 6 illustrates the case where there are two portions in which three curved portions are connected, and a total of six small warp portions 12 are provided. FIG. 7 illustrates the case where four curved portions overlap in two vertical rows and two horizontal rows, and a total of four small warps 12 are provided.

When a plurality of small warpages 12 are provided, as illustrated in FIG. 1, the intervals between adjacent

small warpages

12 and 12 are approximately equal to the formation area of the large warpage 11 in the substrate 10, and each small warpage 12 Are uniformly disposed. In this embodiment, the insulating substrates 52 can be easily joined, and the small warpages 12 can be uniformly deformed when the insulating substrates 52 are joined, and the substrate 10 after joining has a uniform curvature of a radius of curvature R. It is expected to be easy to possess. In particular, as illustrated in FIG. 1, when the shapes and sizes (curvature radius, amount of warpage x, diameter D, etc. described later) of the respective small warpages 12 are substantially equal, the respective small warpages at the time of bonding the respective insulating substrates 52. The portion 12 is more easily deformed uniformly. Even in a configuration in which local warped portions such as a shape in which a plurality of circles are partially overlapped and juxtaposed in plan view continue as in the above-mentioned snowman-like shape, the shape and size of each small warped portion 12 are substantially When each insulating substrate 52 is joined, the small warped portions 12 are easily deformed uniformly. Furthermore, if the shape and size of each small warp portion 12 are substantially equal, when manufacturing the composite member 1 according to the method for manufacturing a composite member of the above-described embodiment, uniform pressure is applied to form the members with high accuracy. Easy to use and excellent in manufacturability. The shape and size of the small-curvature portion 12 can be made different depending on the shape and size of the insulating substrate 52.

It is preferable that the amount x of warpage of the small warpage 12 be adjusted in accordance with the radius of curvature R of the large warpage 11. For example, the curvature radius R is 15000 mm or more and 25000 mm or less, and the amount of warpage x (FIG. 2) of the small warpage portion 12 is more than 30 μm and 70 μm or less. When the radius of curvature R and the amount of warpage x satisfy the above-mentioned range, the small warpage 12 is easily deformed at the time of bonding of the insulating substrate 52, and the board 10 after bonding uniformly has a spherical warpage of the radius of curvature R. It is easy to bring the substrate 10 into close contact with the installation target. Although depending on the curvature radius R, the warpage amount x is 35 μm to 65 μm, and further 40 μm to 60 μm.

The amount of warpage x of the small warpage portion 12 is, in addition to the curvature radius R of the large warpage portion 11, the specifications of the substrate 10 (linear expansion coefficient, Young's modulus, thickness t, etc.), the specifications of the insulating substrate 52 (linear expansion coefficient, It is more preferable to adjust in consideration of Young's modulus, thickness t _{i and the} like) and the specification of the bonding material 54 (solid phase temperature and the like). For example, it is mentioned that the warpage amount x (μm) satisfies the value ± 20% of the following formula [1]. According to the specifications of the substrate 10, the insulating substrate 52, and the bonding material 54, it is preferable to set the warpage amount x so as to satisfy the value of the following formula [1] to manufacture the composite member 1. In the following equation [1], f is a curvature coefficient that satisfies the following equation [2]. Formula [1] and Formula [2] are based on the bimetal calculation formula (form on both ends of flat plate support, one-curve formula on flat plate).
x = (f / 1000) × (Ts-25) × (L / 1000) ² / {((t _i + t) / 1000) × (1000/4)}
... expression [1]
In equation [1], the solidus temperature (° C.) of the bonding material 54 is Ts, the insulating substrate 52 is a flat plate having a rectangular planar shape, the diagonal length (mm) is L, and the thickness (mm) of the insulating substrate 52 ) Is t _i , and the thickness (mm) of the substrate 10 is t.
f = (3 × (α- α i)) / {(3 + ((1+ (ε i / ε) × (t i / t)) × (1+ (t i / t) 3 × (ε i / ε) )) / ((T _i / t) × (ε _i / ε) × (1+ (t _i / t)) ² )}
... Equation [2]
In equation [2], the linear expansion coefficient (ppm / K) of the insulating substrate 52 is α _i , and the Young's modulus (GPa) is ε _i . The linear expansion coefficient (ppm / K) of the substrate 10 is α, and the Young's modulus (GPa) is ε. The Young's modulus of Mg—SiC and the Young's modulus of Al—SiC may be about 150 GPa to 250 GPa depending on the content of SiC and the like.
"Measuring method"
A method of measuring the radius of curvature R, the amount of warpage x, and the diameter D of the substrate 10 will be described.

The curvature radius R, the amount of warpage x, the diameter D and the like of the substrate 10 may be obtained using a commercially available three-dimensional measurement device (for example, non-contact 3D measurement device manufactured by Keyence Corporation, VR 3000). A region (largely curved portion) curved in a spherical shape on the front and back surfaces which is the surface having the largest area among the outer peripheral surfaces (front and back surfaces and side surfaces) of the substrate 10 according to a three-dimensional image obtained by measuring the substrate 10 with a three-dimensional measurement device 11) and the locally curved region (small warpage 12) can be visually determined. In a commercially available three-dimensional measurement apparatus, it is possible to indicate the amount of displacement (μm) from the reference according to color, and by contouring the difference in the amount of displacement, it is possible to grasp the contour shape.

Hereinafter, the case of measurement using a three-dimensional image will be described.
(Measurement procedure of curvature radius R)
(1) Extraction of radius measurement area a (2) Extraction of outline extraction straight line l _n (n = 1 to 10, and so on)
(3) Extraction of a plurality of measurement points for drawing the outline of the warped part (4) Extraction of an approximate arc γ _n from a set of measurement points β _n (5) Calculation of the average of radius R _n of the approximate arc γ _n Then, using a three-dimensional image of the substrate 10, an area (hereinafter referred to as a radius measurement area) used to measure the radius of curvature R is extracted. A surface having a convex warpage is a main surface, an area excluding a local curved portion is extracted from the three-dimensional image of the main surface, and a radius measurement area is taken from the extracted area. When a plurality of small warpages 12 (locally curved parts) are provided separately as in the composite member 1 illustrated in FIGS. 1 and 6, the space between the adjacent

small warpages

12 and 12 An area | region is mentioned as a radius measurement area | region. In FIGS. 1 and 6, a horizontally long rectangular area extending in the left-right direction of the figure is extracted as the radius measurement area a. The long side and the short side of the rectangular radius measurement area a are substantially parallel to the long side and the short side of the rectangular substrate 10 in a plan view. In FIG. 1 and FIG. 6, the radius measurement area a is virtually shown by a dotted line.

As in the case of the composite member 1 illustrated in FIG. 7, in the case where a plurality of curved portions are all continuous and exist over substantially the entire substrate 10, the local curved portions are excluded from the three-dimensional image of the main surface It is possible to include the radius measurement area a including the possible closed area 15. The composite member 1 illustrated in FIG. 7 includes a rhombic closed region 15 surrounded by the four curved portions partially overlapping with each other as described above. In this case, for example, it is a straight line parallel to the long side of the rectangular substrate 10 in plan view, and a straight line passing through two apexes at opposing positions in the rhombus forming the closed region 15 is taken. In other words, a pair of straight lines is taken so as to sandwich the closed region 15. The pair of straight lines has a length that extends to a region of the substrate 10 that does not have a curved portion. It takes a rectangular area surrounded by the pair of straight lines and straight lines (or short sides) parallel to the short sides of the substrate 10. In FIG. 7, a rectangular region is virtually illustrated by a two-dot chain line. Both ends of the rectangle are provided to project from the intersection of the two curved portions, and the closed region 15 is located at the center of the rectangle. An area obtained by removing the curved portion from such a rectangular area may be used as the radius measurement area a. In FIG. 7, the radius measurement area a is shown with cross hatching for easy understanding. In the case where the substrate 10 includes a plurality of closed regions 15, the radius measurement region a may be taken to include the plurality of closed regions 15.

In addition, as shown in FIG. 1 and the like, the radius measurement area a is the center of gravity G of the outer shape of the substrate 10 (the intersection point of the diagonals of the rectangle forming the outer shape of the substrate 10 in FIGS. It may be taken to overlap with the intersection of the diagonals of the rectangle forming a. In addition, setting the area | region of the outer edge vicinity of the board | substrate 10 as a radius measurement area | region is mentioned. When a bolt hole or the like described later is provided in the substrate 10, an area excluding the bolt hole or the like is used as a radius measurement area.

The curvature radius R of the substrate 10 in a state in which the insulating substrate 52 is joined with respect to the heat dissipation member 3 provided in the heat dissipating member 3 and the semiconductor device 5 described later, and the insulating substrate 52 on which the semiconductor element 50 is mounted is further joined. In the case of measuring the radius measurement area, the radius measurement area can be taken including the area where the insulating substrate 52 and the like are joined.

In step (2), if the radius measurement area a is a rectangle, a total of ten contour extraction straight lines l _n including the long side of the rectangle and parallel to the long side are taken. The contour extraction straight lines l ₁ and l ₁₀ are straight lines forming the long side of the rectangle, and the contour extraction straight lines l ₂ to l ₉ are straight lines passing through points equally dividing the short side of the rectangle. When the radius measurement area a includes at least one closed area 15, as described above, a rectangle having long sides as a pair of straight lines sandwiching the closed area 15 is taken, and an outline extraction straight line l _n parallel to the long sides Take a total of 10 bottles.

In step (3), a plurality of measurement points are drawn outlining the radius measurement area a along each contour extraction straight line l _n . A set of measurement points β _n is taken for each contour extraction straight line l _n . Measurement points are taken at intervals of, for example, 1 mm for one contour extraction straight line l _n . Assuming that the value of each measurement point (typically, the displacement amount) is an average value as described below, it is considered that the smooth shape is more easily extracted because the measurement point is smoothed as compared with the case where it is used as it is. Specifically, in one contour extraction straight line l _n , a point p is taken every 1 mm, and the value of the point p and the values of the points in the vicinity thereof are averaged based on the point p. For example, assuming that the coordinates (X, Y) of the point p are (0, 0), a total of nine coordinate values are taken such that X = 0 mm, ± 1 mm, Y = 0 mm, ± 1 mm. The average of the values (displacement amounts) of these nine points is taken as the value of this point p (average displacement amount). The smoothing process for the measurement point can easily obtain an average value by setting a condition and causing the three-dimensional measurement device to perform the process.

FIG. 4 is a graph schematically showing an analysis result obtained by a commercially available three-dimensional measurement apparatus. In FIG. 4, 21 measurement points are used for easy understanding. The horizontal axis of the graph in FIG. 4 is the position of a point on a straight line parallel to the contour extraction straight line l _n , and the vertical axis is passing the above-mentioned center of gravity G and the contour extraction straight line l _n (long side direction) and short side direction The position of a point on a straight line orthogonal to both is shown. Each point on the horizontal axis substantially coincides with the position of each point on the contour extraction straight line l _n , and each point on the vertical axis indicates the amount of displacement of the contour based on the origin of this graph. The set of 20 measurement points (legends ●) shown in FIG. 4 is a set of measurement points β _n extracted based on the contour extraction straight line l _n .

In step (4), for each set of measurement points β _n , a plurality of measurement points are approximated by the least squares method to obtain an approximate arc γ _n . That is, take the approximate arc gamma _n as the distance d between the approximate arc gamma _n corresponding to the set beta _n each measurement point included in the set beta _n is minimized. Here, a total of ten approximate arcs γ _n are obtained. Then, in step (5), the average of the radii R _n of the ten approximate arcs γ _n is determined, and the average value of the radii R _n is taken as the curvature radius R. Let the average of all the calculated distances d be the spherical error described later. Even when the radius measurement area a includes at least one closed area 15, the approximate arc γ _n of the closed area 15 can be appropriately determined by approximating a plurality of measurement points by the least squares method for each set β _n . The approximate arc γ _n and the distance d can be easily obtained by using commercially available analysis software such as Excel. If the curvature radius R is 15000 mm or more and 35000 mm or less, the radius measurement region a forms the large warpage part 11, and the substrate 10 has the large warpage part 11.

Next, with reference to FIG. 2 as appropriate, a method of measuring the amount of warpage x of the substrate 10 will be described.
The amount of warpage x is measured by extracting a locally curved portion from the three-dimensional image of the main surface of the substrate 10 and using the extracted curved portion. If there are a plurality of local curved portions, the warpage amount x is measured one by one. In one local bending portion, a point P having a maximum displacement amount is extracted. Further, a plurality of measurement points that outline the local curved portion are approximated by the least square method to obtain an approximate curve. Take a boundary point between the approximate curve and a large warping unit 11 passing through the point P (the straight line shown in phantom in FIG. 2, the two-dot chain line) (in FIG. 2 the point Q _1, the point Q ₂ illustrated) plane containing the. The distance between the point P and this plane is taken as the amount of warpage x. When it is possible to extract the boundary between a spherical warped portion (large warped portion 11) with a radius of curvature R and a local warped portion (small warped portion 12) from a three-dimensional image, the plane is taken using the extracted border . When it is difficult to extract the above-mentioned boundary from a three-dimensional image, for example, the radius of curvature passes through a measurement point that outlines a region between adjacent local curved portions (typically, a region forming the large warp portion 11) An arc satisfying R is taken, and a plane including the boundary point between this arc and the approximate curve passing through the point P is taken. Using the distance between this plane and the point P as the amount of warpage x can be mentioned. The radius of curvature of the small-warped portion 12 may be determined from the approximate curve passing through the point P.

When the small-curvature portion 12 includes a circular portion in plan view, the diameter D of the circular portion can be easily measured by measurement using a three-dimensional image of the substrate 10. For example, a three-dimensional image is converted to a two-dimensional image to measure the diameter D in plan view. In addition, about the extraction method of the boundary of the large curvature part 11 and the small curvature part 12, it is as above-mentioned.

If a three-dimensional image is used, it is possible to grasp a shape in which a plurality of locally curved portions are connected, such as the above-mentioned snowman-like shape. Further, by using a three-dimensional image, it is possible to extract a point P which takes the maximum displacement amount in each curved portion. Therefore, for the substrate 10 having a shape in which local curved portions are continuous as illustrated in FIGS. 6 and 7, the amount of warpage x may be determined as follows.

First, the point P is extracted from each curved portion.
Next, the three-dimensional image is converted into a two-dimensional image, and overlapping regions 125 of curved portions (which are hatched in a grid shape in FIGS. 6 and 7) are generated when the external shape of each curved portion is complemented into a circle. A region obtained by removing a virtual region shown from each curved portion is taken, and from this region, the largest circle 120 (shown in phantom in FIG. 6 and FIG. 7 by a two-dot chain line) centered on the point P is extracted. In a simple manner, the largest circle centered on the point P can be extracted from each curved portion, but it is easy to measure the warpage amount x with high accuracy if the overlapping area 125 is removed as described above.

Next, from the diameter D of the extracted circle 120 and the displacement of the point P, a spherical surface passing through the point P is determined.
Then, as described above, an arc having a radius of curvature R determined using the radius measurement area a is taken, and a plane including the boundary point between this arc and an approximate curve that describes a spherical surface passing through the point P is taken. Using the distance between the point P and this plane as the amount of warpage x can be mentioned. Moreover, setting each curved part which has the point P as the small curvature part 12 is mentioned. The radius of curvature of each of the small warpages 12 may be determined from the spherical surface passing through the point P described above.

When a plurality of local curved portions are provided, the amount of warpage of adjacent curved portions is different, and when the amount of warpage of one curved portion is very small compared to the other, the curvature of one curved portion is the other curved portion There is a possibility that the warpage amount x of one curved portion can not be calculated properly. In this case, it is considered that there is no problem in ignoring the curvature of one curved portion. If the insulating substrate 52 is bonded to each of the one curved portion and the other curved portion, it is expected that the warpage of one curved portion can be absorbed by the deformation of the other curved portion having a large amount of warpage. It is.
<Thermal characteristics>
The substrate 10 has a thermal conductivity of 150 W / m · K or more and a linear expansion coefficient of 10 ppm / K or less. By adjusting the composition of the metal 20, the composition and the content of the nonmetal 22, etc., those having higher thermal conductivity and those having smaller linear expansion coefficient can be mentioned. For example, the thermal conductivity of the substrate 10 is 180 W / m · K or more, further 200 W / m · K or more, and particularly 220 W / m · K or more. Also, for example, the linear expansion coefficient of the substrate 10 is 9 ppm / K or less, and further 8 ppm / K or less. When the linear expansion coefficient of the substrate 10 is smaller, the linear expansion coefficient of the composite member 1 including the substrate 10 and the metal coating becomes smaller, preferably 10 ppm / K or less, even when the metal coating described later is provided. it can. The composite member 1 including the substrate 10 having a higher thermal conductivity and a linear expansion coefficient of about 3 ppm / K to about 10 ppm / K is excellent in heat dissipation and linear expansion with the semiconductor element 50 and its peripheral parts. It is excellent in the consistency of the coefficient, and can be suitably used for the heat dissipation member 3 of the semiconductor element 50. The linear expansion coefficient of the substrate 10 is, for example, 3 ppm / K or more, 4 ppm / K or more, and 4.5 ppm / K or more in the range in which the above-mentioned consistency is excellent.
<Others>
The composite member 1 can be provided with a metal coating (not shown) on at least a part of one side or both sides of the substrate 10. Depending on the type of metal, when the metal coating is provided, the wettability with the bonding material 54 such as solder, corrosion resistance, design and the like can be enhanced. For example, the application region of the bonding material 54 on the substrate 10 may be provided with a metal coating that is to be a base layer of the bonding material 54.

As a constituent metal of the metal coating, any of the same kind of metal as the metal 20 contained in the substrate 10 and different kinds of metals can be used. As dissimilar metals, when the metal 20 is an alloy, the base metal is the same alloy, others, pure nickel or nickel alloy, zinc or zinc alloy, pure gold or gold alloy, etc. The constituent metals of the above-mentioned base layer include pure nickel, nickel alloy, pure copper, copper alloy, pure gold, gold alloy, pure silver, silver alloy and the like. The metal coating may be either a single layer structure or a multilayer structure comprising a plurality of metal layers.

The thickness of the metal coating per one side of the substrate 10 (total thickness in the multilayer structure, the same applies hereinafter) is 100 μm or less, further 50 μm or less, particularly 20 μm or less, 15 μm or less An increase in the linear expansion coefficient can be reduced, which is preferable. When the thickness is uniform, or when the metal coating is provided on both sides of the substrate 10, local deformation due to the non-uniform thickness can be reduced if the thickness of the metal coating on each side is equal. Preferred.

The composite member 1 can include an attachment portion (not shown) to the installation target. The mounting portion includes, for example, a bolt hole or the like through which a fastening member such as a bolt is inserted. When the mounting area is the substrate 10 itself, the mounting area may be a location away from the large warpage 11 and the small warpage 12, for example, the vicinity of the outer edge of the substrate 10. Alternatively, the formation region of the attachment portion may be a metal region continuously provided on the substrate 10. The method of forming the mounting portion can be referred to a known method such as cutting, punching or molding.

When the residual stress difference between the front and back surfaces of the substrate 10 is small, the composite member 1 can easily suppress the deformation caused by the release of the residual stress even when subjected to a cooling and heating cycle at the time of use, and can easily maintain the close contact with the installation object preferable. When the composite member 1 is manufactured by the method for manufacturing a composite member according to an embodiment described later, the composite member 1 can have a small residual stress difference, preferably, substantially no difference. As described above, when the Mg—SiC substrate 10 is provided, the residual stress difference can be easily reduced.
<Major effects>
In the composite member 1 according to the embodiment, the substrate 10 has a spherical warp with a radius of curvature R particularly in a state where the insulating substrate 52 and the like are joined, and the warped portion is uniformly pressed against the installation target It can be in close contact. Since the substrate 10 has a high thermal conductivity, the composite member 1 is suitably used as the heat dissipating member 3 to which the insulating substrate 52 is bonded by the bonding material 54 such as solder, typically the heat dissipating member 3 of the semiconductor element 50 it can. The heat radiating member 3 can well transmit the heat of the heat generation target such as the semiconductor element 50 to the installation target, and is excellent in heat dissipation.

In addition, it is desirable that the composite member 1 of the embodiment has excellent thermal conductivity and a small amount of thermal expansion and contraction, and a structural material such as a member having a very small linear expansion coefficient such as the insulating substrate 52 is soldered or the like. It can be expected to be used for etc.
[Heat dissipation member]
The heat radiating member 3 of the embodiment will be described mainly with reference to FIG.

The heat dissipating member 3 of the embodiment includes the composite member 1 of the above-described embodiment and the insulating substrate 52 joined to the small warpage 12 via the bonding material 54, and the substrate in a state in which the insulating substrate 52 is joined. The curvature radius R of 10 is 5000 mm or more and 35000 mm or less. The curvature radius R of the heat dissipation member 3 is basically measured based on the above-described measurement method. However, since the heat dissipation member 3 to which the insulating substrate 52 is bonded does not substantially have the small warpage 12 as described later, the radius measurement region used for measuring the curvature radius R of the heat dissipation member 3 is the insulating substrate 52 And the radius measurement area a of the composite member 1 not provided with For example, the radius measurement area used to measure the radius of curvature R of the heat dissipation member 3 is the smallest rectangular area including the bonding portion of the insulating substrate 52 in the substrate 10 (all insulating substrates when including the plurality of insulating substrates 52) The smallest rectangular area including 52 junctions can be mentioned. In the case where a total of six insulating substrates 52 are joined to the substrate 10 as shown in FIG. 1 by being separated, a total of six bonding points of the insulating substrates 52 including the region between the adjacent insulating

substrates

52 and 52 The smallest rectangular area that includes. May be used as the radius measurement area. The radius of curvature R of the heat dissipation member 3 may be referred to as the radius of curvature R of the term of the large warpage portion described above.

As described above, the composite member 1 according to the embodiment includes the large-warped portion 11 having a spherical warpage with a radius of curvature R and the small-warped portion 12 provided locally (upper view in FIG. 3). When the insulating substrate 52 is joined to the small warpage 12 by the bonding material 54 such as solder (in the middle view of FIG. 3), the small warpage 12 is locally deformed. Typically, the small-curvature portion 12 having a radius of curvature smaller than the radius of curvature R is deformed such that the curvature is reduced (returned) and the radius of curvature is increased. Due to this deformation, the small warpage 12 is substantially eliminated, and the outer shape of the bonding portion of the insulating substrate 52 on the substrate 10 is likely to have a shape along the outer shape of the large warpage 11 (lower in FIG. 3). Typically, the heat dissipation member 3 according to the embodiment uniformly has a spherical warpage with a radius of curvature R in a state in which the insulating substrate 52 is provided. For example, when the substrate 10 is cut in a plane parallel to the thickness direction, the cross-sectional profile of the substrate 10 in any cross section describes an arc having a radius of curvature R, ie, a substantially similar arc. Alternatively, for example, when the substrate 10 is subjected to three-dimensional analysis by a three-dimensional measurement device, and the height information of the three-dimensional analysis is expressed in two dimensions as contour lines (when converted to two dimensions), the contour lines draw concentric circles.

As an example of the heat dissipation member 3, when the curvature radius R and the spherical error are measured as described above in the substrate 10 in a state where the insulating substrate 52 is joined, the spherical error is 10.0 μm or less. The spherical error can be said to be an index indicating the spherical degree of the warped portion of the substrate 10, and it can be said that the radius measurement region has a true spherical warp with a radius of curvature R as the spherical error is smaller. The heat radiation member 3 having a small spherical error as described above uniformly presses the above-described spherically curved portion against the installation object to be in close contact with the installation object, and prevents deformation due to uneven thermal expansion and contraction. Easy to do. The spherical error is preferably 9.0 μm or less, more preferably 8.5 μm or less, and ideally 0 μm from the viewpoint of adhesion, prevention of uneven deformation and the like. Since the spherical error of the heat dissipation member 3 depends on the spherical error of the large warpage 11 of the substrate 10 before bonding the insulating substrate 52, the spherical error of the large warpage 11 is also preferably 10.0 μm or less. When industrial productivity etc. are considered, it is mentioned that the spherical surface error of the large curvature part 11 or the thermal radiation member 3 is about 1.0 micrometer or more. If the radius of curvature R of the heat dissipation member 3 is within the above-described specific range and the spherical error is 10.0 μm or less, the radius of curvature R may be the above-described specific even with the semiconductor element 50 bonded on the insulating substrate 52. The spherical error is 10.0 μm or less. Therefore, if the heat dissipating member 3 having a small spherical error as described above is used as the heat dissipating member of the semiconductor element 50, the semiconductor device 50 has a spherically curved portion even in a state where the semiconductor element 50 is mounted on the insulating substrate 52 It is attached to

The shape and size of the heat dissipation member 3 can be appropriately selected as long as the object to be heated can be placed. Typically, since the shape and size of the heat dissipation member 3 depend on the shape and size of the substrate 10 of the composite member 1, the shape and size of the substrate 10 of the composite member 1 may be adjusted.

The insulating substrate 52 is used for the mounting location of the heat generation target such as the semiconductor element 50 or the like, and secures the electrical insulation with the substrate 10 including the metal 20. Such an insulating substrate 52 may be an electrically insulating material, for example, a nonmetallic inorganic material such as aluminum nitride, aluminum oxide or silicon nitride. The insulating substrate 52 made of the nonmetallic inorganic material may have a linear expansion coefficient of 7 ppm / K or less, further 5 ppm / K or less, and a Young's modulus of 200 GPa or more, further 250 GPa or more.

The shape and size of the insulating substrate 52 can be selected as appropriate. When the planar shape of the insulating substrate 52 is a rectangle (may be a square) as illustrated in FIGS. 1, 6 and 7 and the small warpage 12 includes a circular portion in plan view before the bonding of the insulating substrate 52 Preferably, at least one of the long side length, the short side length, and the diagonal length of the rectangle substantially corresponds to the diameter D of the circular portion. More preferably, the diagonal length substantially corresponds to the diameter D. In this case, rectangular centroid (intersection of diagonal lines) forming the outer shape of the insulating substrate 52 is an insulating substrate 52 to substantially match the center C ₁₂ of the circular portion is joined to the small warp 12 Is preferred. This is because the small warpage 12 is easily deformed uniformly when the insulating substrate 52 is bonded, and the substrate 10 after bonding easily has a spherical warpage with a radius of curvature R uniformly. 1, 6 and 7 exemplarily show the case where the center C ₁₂ and the center of gravity of the insulating substrate 52 substantially coincide with each other while the insulating substrate 52 is virtually shown by a two-dot chain line. Further, in FIG. 1, the diameter D substantially corresponds to the length of the short side of the insulating substrate 52, and in FIG. 6, the diameter D substantially corresponds to the length of the long side of the insulating substrate 52. To illustrate. Although only one insulating substrate 52 is shown in FIGS. 6 and 7 so that the small-curvature portion 12 and the circle 120 and the like can be easily understood, the insulating substrate 52 can be joined to each small-curvature portion 12 respectively.

The thickness t _i of the insulating substrate 52 can be appropriately selected as long as electrical insulation between the heat generation target such as the semiconductor element 50 and the like and the substrate 10 (in particular, the metal 20) can be secured. As the thickness t _i of the insulating substrate 52 is thicker, the electrical insulation between the object to be heated and the substrate 10 is improved, which is suitable for high-power applications, and is 0.8 mm or more, and further 1 mm or more. Be From the viewpoint of small size and thinness, the thickness t _i may be 5 mm or less, further 3 mm or less, or 2 mm or less. The number of insulating substrates 52 may be selected according to the number of objects to be heated.

As the bonding material 54, solder containing Pb (solidus temperature: about 183 ° C.), solder not containing Pb, etc. may be mentioned, and known materials can be used. Solder containing no Pb tends to have a higher solidus temperature than solder containing Pb (eg, solidus temperature: 200 ° C. or more, further 250 ° C. or more). Even when the bonding material 54 having a higher solidus temperature is used, the amount of warpage x of the small warpage portion 12 is adjusted to satisfy, for example, the value ± 20% of the above-mentioned formula [1]. The substrate 10 after bonding tends to uniformly have a spherical warpage with a radius of curvature R.

In the heat dissipating member 3 of the embodiment, the substrate 10 has a spherical warp with a radius of curvature R in a state where the insulating substrate 52 is provided as described above, and the warped portion is uniformly pressed against the installation target Can adhere to Therefore, the heat dissipating member 3 can be well transferred with the heat of the heat generating object such as the semiconductor element 50 to the installation object, and is excellent in the heat dissipating property. Such a heat dissipation member 3 can be suitably used as a heat dissipation member of the semiconductor element 50.
[Semiconductor device]
The semiconductor device 5 of the embodiment includes the heat dissipation member 3 of the embodiment and the semiconductor element 50 mounted on the insulating substrate 52 as shown in FIG. 5, and the insulating substrate 52 on which the semiconductor element 50 is mounted is joined. The curvature radius R of the substrate 10 in the state is 5000 mm or more and 35000 mm or less. One surface of the substrate 10 is a spherical warpage with the radius of curvature R and has a convex warpage (not shown), and one surface having the convex warpage is an installation surface with a cooling device (not shown). . The opposite surface is a mounting surface to which mounting components such as the semiconductor element 50 are attached via the insulating substrate 52. The semiconductor element 50 is mounted on the insulating substrate 52 via a bonding material 54 such as solder. In the semiconductor device 5 of the embodiment, since the substrate 10 in the state provided with the semiconductor element 50 and the insulating substrate 52 has the above-mentioned spherical warp, the warped portion is uniformly pressed against the installation object such as a cooling device. It can be closely attached to the installation target.

When the spherical error of the substrate 10 in the state where the insulating substrate 52 on which the semiconductor element 50 is mounted is joined satisfies 10.0 μm or less, it has a warp of a true spherical shape, It is uniformly pressed by the installation object. Therefore, the semiconductor device 5 is well transferred with the heat of the semiconductor element 50 to the installation object, and is excellent in heat dissipation. If the heat radiation member 3 having the spherical error of 10.0 μm or less is used, the heat radiation member 3 (substrate 10) provided in the semiconductor device 5 can easily satisfy the spherical error of 10.0 μm or less. The semiconductor device 5 provided with the insulating substrate 52 having a thickness t _i of 1 mm or more is also excellent in the electrical insulation between the semiconductor element 50 and the heat dissipation member 3 and is suitable for high power applications. The curvature radius R and the spherical error of the heat dissipation member 3 (substrate 10) provided in the semiconductor device 5 and the thickness t _i of the insulating substrate 52 are the curvature radius R and the spherical error of the heat dissipation member. , Thickness t _i may be referred to.

The semiconductor device 5 according to the embodiment includes various electronic devices, in particular, high frequency power devices (for example, LDMOS (Laterly Diffused Metal Oxide Semiconductor)), semiconductor laser devices, light emitting diode devices, and other central processing units (CPUs) of various computers. , Graphics Processing Unit (GPU), High Electron Mobility Transistor (HEMT), Chipset, Memory Chip etc.
[Method of manufacturing composite member]
The composite member 1 of the embodiment including the above-described large-curvature portion 11 and the small-curvature portion 12 can be manufactured, for example, by using the method for manufacturing a composite member of the following embodiment. The method of manufacturing a composite member according to the embodiment includes a pressing step of housing a material plate made of a composite material containing metal and nonmetal in a mold and performing heat pressing, and using a mold satisfying the following conditions, The pressing process comprises the following holding process and cooling process.
<Condition of mold>
A large spherical surface portion having a spherical surface with a radius of curvature Rb and a small spherical surface portion partially provided with the spherical surface and having a radius of curvature Rs different from the radius of curvature Rb are provided.

The curvature radius Rb is 5000 mm or more and 35000 mm or less.
<Conditions of press process>
<< Holding Step >> The heating temperature is set to more than 200 ° C., and the applied pressure is set to 10 kPa or more, and held for a predetermined time.
<< Cooling Step >> While maintaining a pressurized state of 80% or more of the applied pressure, cooling is performed from the heating temperature to 100 ° C. or less.

In addition, the method of manufacturing the composite member according to the embodiment includes a preparation step of preparing a material plate, a covering step of forming a metal coating, a slight surface polishing for forming an attachment portion, adjusting a surface roughness, etc. A processing step or the like may be provided.

Each step will be described below.
<Preparation process>
In this process, a material plate to be subjected to heat press is prepared. For production of the blank, a known production method for producing a composite material containing the metal 20 and the nonmetal 22 in a plate shape can be used. For example, an infiltrating method (see Patent Document 1) in which a mold is filled with powder or compact of nonmetal 22 and the like, and molten metal 20 is infiltrated, a pressure infiltration method infiltrating at high pressure, and the like Powder metallurgy methods, melting methods and the like can be mentioned. A commercially available plate made of the above composite material can also be used as a material plate.

Composition of metal 20, non-metal 22 so that the thermal conductivity and linear expansion coefficient of the substrate 10 manufactured from the material plate become desired values (typically 150 W / m · K or more and 10 ppm / K or less) Adjust the composition, content, form (powder, molding etc) of Depending on the composition of the metal 20 and the composition and form of the nonmetal 22, if the content of the nonmetal 22 in the material plate is 55% by volume or more, the thermal conductivity is high as described above and the linear expansion coefficient is small. It is easy to obtain the composite member 1 of the embodiment.

In the case of producing a composite member having a metal coating, for example, a plating method, clad rolling, a method of simultaneously forming at the time of producing a material plate (see Patent Document 1), and other known methods can be appropriately used for forming a metal coating. . The metal coating can be formed before and after hot pressing (an example of a coating process). If a material plate having a metal coating is prepared prior to heat pressing, the shape of the material plate is a simple shape having no warp, and it is easy to form the metal coating. When the metal coating is formed on the substrate 10 after the hot pressing by a plating method or the like, it is possible to prevent the variation of the warpage caused by the provision of the metal coating at the time of the hot pressing, and to easily form the predetermined warpage with high accuracy.
<Pressing process>
In this step, heat pressing is performed using a mold including a first mold having a convex surface satisfying the conditions of the above-described mold and a second mold having a concave surface corresponding to the convex surface. The raw material plate is sandwiched between the first mold and the second mold and pressurized in a heated state to transfer the spherical surface of radius of curvature Rb and the spherical surface of radius of curvature Rs onto the raw material plate. By this transfer, it has a spherical warpage (mainly the large warpage part 11) formed by a spherical face of curvature radius Rb, and is formed by a spherical face of curvature radius Rs, and typically, warpage of a warpage amount x (small warpage part 12) manufacturing a substrate 10 having locally.

The radius of curvature Rb may refer to the term of the radius of curvature R described above. The curvature radius Rs is typically a value smaller than the curvature radius Rb, and is preferably selected so as to satisfy the value ± 20% of the above-mentioned equation [1] such that the warpage amount x becomes a desired value. Can be mentioned. Specifically, a plane passing through a boundary between a spherical surface of radius of curvature Rb and a spherical surface of radius of curvature Rs on the inner peripheral surface of the mold and a point of the spherical surface of radius of curvature Rs farthest from the above plane are taken. Since the distance from the above plane to this point corresponds to the amount of warp x, the shape of the mold is adjusted so that the above distance becomes a desired value. By using a molding die having a plurality of small spherical portions, the composite member 1 having a plurality of small warpages 12 can be manufactured. When a plurality of small spherical portions are provided separately, it is possible to form a plurality of small warpages 12 whose plane shape is a circle as shown in FIG. When a plurality of small spherical portions are partially overlapped, as shown in FIGS. 6 and 7, a plurality of small warpages 12 connected in a snowball shape can be formed. The shape, size, number, position, etc. of the small spherical portion may be adjusted and provided in the mold so that the small curved portion 12 having a predetermined shape, size and number can be formed at a predetermined position of the substrate 10.

When using a material plate having a rectangular planar shape, the material plate is molded so that the center of the material plate (the intersection of the diagonals of the rectangle) coincides with the center of the spherical surface of radius of curvature Rb in the first and second molds. It can be mentioned that By doing this, it is easy to obtain a composite member having a spherical warp with a radius of curvature R centered on the center of gravity ((center of the material plate) in the outer shape of the substrate.
<< holding process >>
By setting the heating temperature (here, the heating temperature of the mold) to 200 ° C. and the applied pressure to 10 kPa or more during heat pressing, plastic deformation of the material plate including the nonmetal 22 can be promoted, and the different curvature radii Rb and Rs Can be transferred to the material plate. The higher the heating temperature, the more easily the material plate is plastically deformed. Therefore, the heating temperature can be set to more than 250 ° C., and further to 280 ° C. or more and 300 ° C. or more. The larger the applied pressure is, the more easily the material plate is plastically deformed. Therefore, the applied pressure can be set to 100 kPa or more, and further to 500 kPa or more and 700 kPa or more. The higher the heating temperature and the higher the applied pressure, the easier the residual stress is reduced. The heating temperature can be 350 ° C. or more, 380 ° C. or more, 400 ° C. or more, and the applied pressure can be 1 MPa or more, 10 MPa or more, 15 MPa or more from the viewpoint of reduction of insufficient deformation and reduction of residual stress. Depending on the composition of the material plate, the heating temperature can be 500 ° C. or more, the applied pressure can be 15 MPa or more, and further 20 MPa or more. By holding at such a relatively high temperature and relatively high pressure, the above-mentioned specific warpage can be formed with higher accuracy. The upper limit of the heating temperature is lower than the liquidus temperature of the metal 20 in the material plate, and can be selected in the range in which the metal 20 and the nonmetal 22 are not easily thermally deteriorated. The upper limit of the applied pressure can be selected in a range in which no cracking or the like occurs in the material plate.

If the material plate is also heated (preheated) in addition to the heating of the forming die, the material plate is easily plastically deformed uniformly and can be formed with high accuracy, and cracking due to the temperature difference between the forming die and the material plate is difficult to occur. To From the viewpoint of these effects, the mold temperature is within ± 20 ° C., and the mold temperature is within ± 10 ° C., preferably, the material plate is stored in the mold in a heated state equivalent to the mold temperature. Is preferred.

The holding time of the above-mentioned heating and pressurizing state can be suitably selected according to the composition etc. of a material board, for example, selecting from the range of 10 seconds or more and 180 minutes or less is mentioned. For example, in the case of Mg—SiC, about 1 minute to 5 minutes, and in the case of Al—SiC, about 1 minute to 100 minutes or less. When a Mg—SiC material plate is used, it may be easy to form with high accuracy even if the holding time of the heat press is short compared to the case where an Al—SiC material plate is used, and the productivity is excellent.
<< Cooling process >>
After the above-mentioned holding time has elapsed, cooling is performed from the above-described heating temperature to room temperature (eg, about 10 ° C. to about 20 ° C.). In the range from the said heating temperature in a cooling process to 100 degreeC, it cools in a pressurized state. The applied pressure in the cooling process is 80% or more of the applied pressure at the time of the above-described heat pressing. By cooling in such a specific pressurized state, it is possible to suppress deformation or the like due to local heat shrinkage accompanying non-uniform cooling, and to form the plurality of warpages described above with high accuracy. Residual stress is also easily reduced by suppressing the above-mentioned local heat contraction. The applied pressure in the cooling process may be equal to or less than the applied pressure at the time of heat pressing, because if the pressure is too high, cracking may occur or internal stress may increase with new deformation that occurs during cooling. It is preferable to adjust in the range of 100% or less of the applied pressure at the time of heat press. In the cooling process, in the range from a temperature of less than 100 ° C. to room temperature, the film can be unloaded and cooled without pressure.

In the range which cools in a specific pressurization state in the above-mentioned cooling process, it is preferred to carry out slow cooling. This is because the pressurized state in the above-described cooling process can be appropriately secured, and the above-described plurality of warps can be formed with high accuracy. In the case of rapid cooling (typically, the cooling rate is 10 ° C./min or more), the entire blank may not be uniformly cooled due to the difference in heat capacity between the mold and the blank and the difference in thermal conductivity. Therefore, the material plate is locally cooled to cause thermal stress, which may result in internal stress or deformation. Here, slow cooling includes that the cooling rate satisfies 3 ° C./min or less. The cooling rate can be 1 ° C./min or less, and further 0.5 ° C./min or less. Adjusting the ambient temperature or the like of the mold, adjusting the cooling state by the forced cooling mechanism, and the like so that the cooling rate satisfies the above range may be mentioned. When using a material plate with a high content of nonmetals 22, for example, 55% by volume or more, further 60% by volume or more, 65% by volume or more, and using a material plate with relatively high rigidity, slow cooling is preferable Conceivable.

In addition, if the above-mentioned cooling process is assumed to be cooling without pressure, for example, stress and the like due to local heat contraction accompanying non-uniform cooling from the surface of the material plate to the inside occur. It is believed that the shape transferred may be deformed.

By passing through the above-described pressing process, the substrate made of the above-mentioned composite material has a spherical warp with a radius of curvature R of 5000 mm or more and 35000 mm or less, and a warp with a different radius of curvature in a part of the spherical warp portion. A composite member having the Typically, the composite member 1 of the embodiment is obtained in which the spherically curved portion with the radius of curvature R forms the large portion 11 and the portions with different radii of curvature form the small portion 12.

If necessary, pressing can be repeated using a plurality of molds to deform the blank in stages.
<Other process>
«Heat treatment before heat press»
Heat treatment can be performed before the above-mentioned pressing process. This heat treatment may sometimes reduce or eliminate residual stress generated at the time of compounding. Although depending on the composition of the material plate, the heat treatment conditions are, for example, a heating temperature of about 350 ° C. to about 550 ° C. (eg, about 400 ° C.), and a holding time of about 30 minutes to about 720 minutes (eg, about 60 minutes) And to be mentioned.
Heat treatment after hot pressing
Heat treatment can be performed after the above-mentioned pressing process. The heat treatment may allow adjustment, reduction, or removal of residual stress applied to the substrate by the above-described pressing process. This heat treatment adjusts the conditions so that no deformation occurs after the heat treatment. Depending on the composition of the material plate, for example, when heat treatment is performed under the conditions of a heating temperature of 100 ° C. or more and 200 ° C. or less and a holding time of 100 hours or more and 1000 hours or less, residual stress is easily removed.
<Manufacture of ball missing form>
In this embodiment, for example, after the above-described pressing process, the surface on the concave side of the molded product is cut or the like to form a flat surface. Depending on the heating temperature and the applied pressure, a spherical shape may be obtained by plastic flow.
[Test Example 1]
A material plate made of Mg-SiC and a material plate made of Al-SiC are subjected to heat pressing under various conditions to produce a warped composite member, and this composite member is used as a heat radiating member of a semiconductor element to dissipate heat. Was evaluated.

The composite member of each sample does not have a metal coating, and is a substrate substantially composed of a composite material, and is produced as follows.
(Material board of Mg-SiC)
The Mg—SiC material plate is manufactured by the infiltration method described in Patent Document 1 and the like. The outline is as follows.

The raw material metal is a pure magnesium ingot in which 99.8% by mass or more is Mg and the balance is inevitable impurities. The raw material SiC powder is a coated powder having an average particle diameter of 90 μm and subjected to an oxidation treatment. The raw materials are all commercially available products.

After filling the prepared coated powder in a mold (here, a graphite mold) (the filling rate of the SiC powder to the cavity is 70% by volume), the ingot is melted and infiltrated into the coated powder filled in the mold . The infiltration conditions are an infiltration temperature of 875 ° C., an Ar atmosphere, and an atmospheric pressure of atmospheric pressure. After infiltration and cooling to solidify pure magnesium, the molded product is removed from the mold. This molded product is a plate having a length of 190 mm, a width of 140 mm, and a thickness of 5 mm, and this rectangular molded product is used as a material plate. The composition of the material plate is substantially equal to the material used, and the content of SiC in the material plate is substantially equal to the filling factor (70% by volume) to the mold (these points are made of Al-SiC The same applies to material boards).
(Material board of Al-SiC)
A material plate of Al-SiC is produced by pressure infiltration. Here, the raw material metal is changed to an ingot of pure aluminum in which 99.8% by mass or more is Al and the balance is inevitable impurities, the forming die is a metal die, and the infiltration conditions are changed. (Infiltration temperature: 750 ° C., Ar atmosphere, pressure: selected from 15 MPa to 30 MPa), and manufactured similarly to the material plate of Mg—SiC (filling ratio of SiC powder: 70 volume%). The obtained molded product is a rectangular plate having a length of 190 mm, a width of 140 mm, and a thickness of 5 mm, and this plate is used as a material plate.
(Heat press)
The material plate of each sample is housed in a mold (a first mold having a convex surface, a second mold having a concave surface) and subjected to heat pressing.
<Molding mold>
The first type is a convex large spherical surface having a spherical surface with a radius of curvature Rb of 15000 mm, and a convex having a spherical surface having a radius of curvature Rs (<Rb) different from the radius of curvature Rb. And a small spherical portion of the The second mold has a concave shape corresponding to the convex shape of the first mold. Here, molds having different curvature radii Rs are prepared, and composite members having different warpage amounts x are produced. Sample No. 101, no. 111 is manufactured using a mold having only a large spherical surface portion having a curvature radius Rb of 15000 mm without including a small spherical surface portion having a curvature radius Rs. The number of small spherical portions is six, and each small spherical portion has the same shape and the same size. The planar shape of each small spherical portion is circular, and its diameter is 45 mm. The six small spherical surface portions are arranged at predetermined intervals with respect to the large spherical surface portion in 3 columns × 2 rows.
<Heat pressing conditions>
In a sample using a Mg—SiC material plate, the heating temperature of the mold is 400 ° C., the applied pressure is 20 MPa, and the holding time is 1 minute. After this holding time has elapsed, the heating temperature is cooled to about room temperature (here, 20 ° C.). In the process of cooling from the above heating temperature to 100 ° C., while being pressurized at a pressure selected from the range of 80% to 100% of the applied pressure, slow cooling is performed at a cooling rate of 3 ° C./min or less.

In a sample using an Al—SiC material plate, the heating temperature is 550 ° C., the applied pressure is 20 MPa, and the holding time is 100 minutes. The conditions of the cooling process are the same as those of Mg—SiC (slow cooling under pressure).

Here, the material plate is preheated to the heating temperature of the forming die and hot pressing is performed. The blank is housed in the mold so that the center of the preheated blank (the intersection of the rectangular diagonals) coincides with the center of the aspheric surface in the first and second dies.

The heat-pressed product (substrate) subjected to the above-described heat-pressing is used as a composite member of each sample. The radius of curvature R (mm) of the composite member of each sample and the amount of warpage x (μm) before bonding of the insulating substrate are shown in Table 1. In Table 1, for sample nos. 1 to No. 5, no. 101 to No. The sample No. 104 is a sample provided with a substrate made of Mg-SiC. 11 to No. 15, No. 111 to No. Reference numeral 114 denotes a sample provided with a substrate made of Al-SiC.

The details of the method of measuring the radius of curvature R and the amount of warpage x are as described above. The measurement of the radius of curvature R is typically performed by arranging the composite member of each sample on a horizontal base or the like so that the main surface having a convex curvature is upward. The outline of the measurement method is described below.

The composite member of each sample is a rectangular plate of approximately 190 mm × 140 mm in plan view. The radius measurement area a is extracted from the three-dimensional image of the main surface having the convex warpage in this plate material, excluding the locally curved portion. Here, a rectangular radius measurement area a (see FIG. 1) having a long side of about 170 mm and a short side of about 20 mm is extracted such that the center of the rectangle overlaps the center of gravity G of the plate. From radius measurement region a, it is parallel to the long side of the rectangle, take l ₁₀ the short side from the contour extraction straight l ₁ through the points obtained by equally dividing. Along each contour extraction straight line l _n , a plurality of measurement points are drawn that delineate the radius measurement area a. For each set of measurement points β _n , an approximate arc γ _n is obtained by approximating a plurality of measurement points by the least square method. The average of the radii R _n of the ten approximate arcs γ _{n is taken as} the curvature radius R (mm) of the composite member of each sample. The average of the distance d between each measurement point of the set β _n and the approximate arc γ _n is a spherical error E. Note that n = 1 to 10. The spherical error of the composite member of each sample before bonding of the insulating substrate is 10 μm or less.

As the amount of warpage x (μm), a local curved portion is extracted from the three-dimensional image (here, six), and a point P having the maximum displacement (μm) in the three-dimensional image is extracted. An approximate curve is obtained by approximating a plurality of measurement points describing a local curve by the least square method. The plane is taken to include a boundary point between the approximate curve passing through the point P and the spherically curved portion of the radius of curvature R. The distance between the point P and this plane is taken as the amount of warp x (μm) of the composite member of each sample.

By using a three-dimensional image, it can be confirmed that any sample has a spherical curvature with a large radius of curvature. Also, for sample no. 101, no. In each sample except 111, it can be confirmed that the locally curved region is arranged in 3 columns × 2 rows in the spherically curved portion (a total of 6 pieces). Here, the locally curved portion is circular in plan view, and when measured using a three-dimensional image, its diameter D is 45 mm, which is equal to the diameter of the small spherical portion of the mold described above. Sample No. 101, no. 111 has spherical curvature with a large radius of curvature, and does not have the locally curved region described above.

A test piece for measurement is cut out of the composite member of each sample, and a thermal conductivity and a linear expansion coefficient are measured using a commercially available measuring instrument. The thermal conductivity is measured at room temperature (here, about 20 ° C.). The linear expansion coefficient is measured in the range of 30 ° C to 150 ° C.

Using the composite member of each sample, a heat dissipation evaluation member is manufactured as follows.
As a composite member of each sample, one having bolt holes at four corners is prepared. Sample No. 101, no. Except for 111, the insulating substrate is soldered to the concave side of the local curved portion in the composite member of each sample. Further, the semiconductor element is soldered on the insulating substrate. Sample No. 101, no. 111 bonds the insulating substrate at approximately the same position as the other samples. Here, the semiconductor element is an IGBT element. The insulating substrate is a 55 mm × 45 mm × 1 mm thick AlN sintered plate (linear expansion coefficient: 4.5 ppm / K, Young's modulus: 270 GPa), and six insulating substrates are joined. The center of the insulating substrate (intersection of diagonal lines) is bonded to each of the insulating substrate to substantially match the center of the local curvature (see C ₁₂ in FIG. 1) to each curved portion. The solidus temperature of the solder is 200.degree. The laminate of the semiconductor element, the insulating substrate, and the composite member is used as an evaluation member.

The manufactured evaluation member is fastened with a bolt to a water-cooled cooler maintained at 30 ° C. The convex side surface of the composite member in the evaluation member is pressed against the cooler, and in this state, bolts are inserted and tightened in the bolt holes at the four corners of the composite member. After energizing the semiconductor element of the evaluation member installed in the cooler to generate heat of 100 W, energization and non-energization for a predetermined time are repeated. Here, “10 minutes of energization, 10 minutes of non-energization” is one cycle, and the cycle is repeated 2000 cycles after the generation of the heat of 100 W described above. The temperature (° C.) of the semiconductor element immediately after energization for 10 minutes in the first cycle and the temperature (° C.) of the semiconductor element immediately after energization for 10 minutes in the 2000 cycle are measured to obtain a temperature difference (° C.). In the sample provided with the substrate of Mg—SiC, sample No. In the sample provided with the temperature difference (° C.) of 3 and the substrate of Al—SiC, sample No. The temperature difference (° C.) of 13 was used as a reference, and the difference from this reference is shown in Table 1. The measurement of the temperature of the semiconductor element can be obtained, for example, from the temperature dependence of the internal resistance of the semiconductor element. In addition, a commercially available noncontact thermometer, a contact thermometer, etc. can also be utilized for the measurement of the said temperature.

The curvature radius R (mm) and the spherical error E (μm) of the composite member of each sample obtained by bonding the above six insulating substrates and the composite member of each sample obtained by further bonding the semiconductor element on the insulating substrate Measure as follows. The measurement results after joining the semiconductor elements are shown in Table 1. The measurement results after bonding of the semiconductor element substantially maintain the measurement results after bonding of the insulating substrate. The radius measurement area here is an area (about 170 mm × about 120 mm) excluding the area up to 10 mm from the outer edge of the substrate.

In a composite member including an Al—SiC substrate, the linear expansion coefficient of the substrate is 7.5 ppm / K, and the thermal conductivity of the substrate is 180 W / m · K. In the composite member including the Mg—SiC substrate, the linear expansion coefficient of the substrate is 7.5 ppm / K, the thermal conductivity of the substrate is 220 W / m · K, and is higher than that of Al—SiC. In any composite member, since the substrate contains about 70% by volume of SiC, the thermal conductivity is as high as 150 W / m · K or more, the linear expansion coefficient is as small as 10 ppm / K or less, and the linear expansion coefficient of the insulating substrate (herein Somewhat close to 4.5 ppm / K).

In the following description, the same composition of a raw material board contrasts and carries out.
As shown in Table 1, the composite members of any of the samples have spherical warpage (the above-mentioned large spherical warpage) with a radius of curvature R of 5000 mm or more and 35000 mm or less on one surface of the substrate before bonding the insulating substrate. I understand that. In addition, it can be seen that the composite members of any of the samples have a spherical warpage in which the curvature radius R in the state where the insulating substrate on which the semiconductor element is mounted is joined is 5000 mm or more and 35000 mm or less. However, even with the above-mentioned spherical warpage, there is a difference in the degree of temperature rise of the semiconductor element. Specifically, before bonding of the insulating substrate, local warpage (the above-described local warpage of a size (here, warpage amount x (μm)) different from the curvature radius R together with the spherical warpage of the curvature radius R) Sample No. 1 having a 1 to No. 5, No. 102 to No. No. 104, sample no. 11 to No. 15, No. 112 to No. Sample No. 114 of the composite member 114 (hereinafter referred to as a multi-stage warpage sample group) has a warpage amount x of 0 μm and does not substantially have warpage of a size different from the radius of curvature R described above. 101, no. It can be seen that the temperature rise of the semiconductor element can be reduced and the heat dissipation property is excellent as compared with the case of 111. In addition, here, sample No. 1 in which the warpage amount x is more than 30 μm and less than 100 μm. 1 to No. 5, no. 11 to No. Sample No. 15 (hereinafter referred to as a proper sample group) has a warp amount x outside the above range. 102 to No. No. 104, no. 112 to No. It can be seen that the temperature rise of the semiconductor element can be further reduced and the heat dissipation property is superior as compared with the sample No. 114 (hereinafter referred to as an unsuitable sample group). Sample No. 1 to No. 5, no. 11 to No. The temperature difference of the above-mentioned semiconductor element in 15 is very small within 5 ° C to a standard.

Sample No. 101, no. As one of the reasons why 111 is inferior to the above-mentioned multistage warpage sample group in heat dissipation, there is a portion (radius measurement area) where the curvature radius R satisfies the above range after bonding of the insulating substrate and the semiconductor element. It is conceivable that there is a portion deviated from the radius of curvature R, that is, a portion which does not properly have a warp before bonding of the insulating substrate. This is supported by the fact that the spherical error deviates from 10 μm or less to more than 10 μm and further more than 15 μm, and the spherical accuracy is lowered. Also, for sample no. 101, no. Sample No. 111 with local warpage. No. 104, no. This is also corroborated by the fact that the spherical error is small compared with 114, but the heat dissipation is inferior. Sample No. No. 104, no. Although it is inferior to the spherical precision, it is considered that due to the provision of local warpage, it has convex warpage even after bonding of the insulating substrate and the semiconductor element, and easily adheres to the cooler to some extent. On the other hand, sample No. 101, no. The reason is that it is considered that, due to the bonding of the insulating substrate, the warpage before bonding is partially returned by the bonding of the insulating substrate to cause a recess or the like, and the recess or the like makes it difficult to closely adhere to the cooler.

In the multi-stage warpage sample group having the above-described local warpage, the local warpage portion is deformed at the time of bonding of the insulating substrate, so that spherical warpage with a radius of curvature R uniformly occurs after bonding of the insulating board. It is considered easy to do. In addition, even after the semiconductor element is mounted on this insulating substrate, it is considered that spherical warpage with a radius of curvature R is likely to be uniform. As a result, the above-mentioned spherical portion is uniformly pressed against the cooler, and the substrate can be closely attached to the cooler, which is considered to be excellent in heat dissipation. In particular, the above-mentioned appropriate sample group has a spherical warpage (corresponding to a large warpage portion) of the above-mentioned radius of curvature R and a local warpage (corresponding to a small warpage portion) provided in part of the spherical warpage portion. Further, it is considered that the warpage of the curvature radius R can be more reliably prevented from being returned or reduced when the insulating substrate is joined, by further providing the warpage amount x satisfying the above-mentioned specific range. . This is supported by the fact that the appropriate sample group has a spherical error E as small as 10.0 μm or less, further 8.5 μm or less as compared with the non-appropriate sample group, and is closer to a true spherical shape. After the bonding of the insulating substrate and the mounting of the semiconductor element by the prevention of the above-mentioned warpage, the spherical warpage of the radius of curvature R is uniformly provided substantially over the whole of the board, and this spherical warpage portion Is considered to be more excellent in heat dissipation because it is in close contact with the cooler.

In addition, the following can be understood from this test.
(A) When the warpage amount x satisfies the value of the above-mentioned equation [1] (sample No. 3 and No. 13) or the value of the above-mentioned equation [1] is close to (here, It is easy to uniformly have a spherical warpage with a radius of curvature R uniformly after bonding the appropriate samples (other than samples No. 3 and 13) satisfying ± 20% and the insulating substrate (suitable samples and unreasonable samples) And compare and see).
(B) The above-described local warpage has a circular portion in plan view, and the diameter D of this circular portion and the outer dimension of the insulating substrate (here, the length of the short side) are substantially equal, At the time of bonding of the substrate, the above-mentioned local warpage part is easily deformed properly, and after bonding, it is easy to uniformly have a spherical warpage of radius of curvature R.
(C) If the curvature radius R is 15000 mm or more and 25000 mm or less and the warpage amount x is more than 30 μm and 70 μm or less, spherical warpage with a curvature radius R can be uniformly uniform after bonding of an insulating substrate or the like.
(D) When the substrate of Mg—SiC is provided, the heat dissipation is excellent as compared with the case of providing the substrate of Al—SiC (compare the above-described thermal conductivity).
(E) If a substrate with a radius of curvature R of 5000 mm to 35000 mm and a spherical error E of 10.0 μm or less in a state in which the insulating substrate is joined is used, the radius of curvature is 5000 mm to 35000 mm even after joining the semiconductor elements. And spherical error satisfies 10.0 micrometers or less, and is excellent in heat dissipation.
(A) A composite member having the above-mentioned spherical warpage of the radius of curvature R and a plurality of warps of local warpage different in size from the radius of curvature R comprises the above-mentioned large spherical portion and the small spherical portion It can manufacture by performing a heat press which shape | molds with a specific heating temperature and a specific applied pressure using the provided shaping | molding die, and cooling by a specific pressurized state. By performing such a specific heat press, it is considered that a residual stress can also be relaxed, and a composite member that is resistant to deformation even when subjected to a thermal cycle can be obtained.
(B) When a Mg-SiC material plate is used, the composite member having a plurality of warps as described above is obtained even if the holding time at the time of hot pressing is further shortened as compared with the case where an Al-SiC material plate is used. It can be manufactured and is excellent in manufacturability.

The present invention is not limited to these exemplifications, is shown by the claims, and is intended to include all modifications within the scope and meaning equivalent to the claims.

For example, in the test example 1 described above, the composition of the substrate, the planar shape, the specifications (size, number, formation position, etc.) of the small warpage portion, the size (length, width, thickness, radius of curvature R, warpage amount x ), Heat press conditions, conditions at the time of combining, and the like can be appropriately changed. In addition, the substrate can be formed in a spherical shape.

DESCRIPTION OF SYMBOLS 1 composite member, 10 board | substrates, 11 large curvature parts, 12 small curvature parts, 120 yen, 125 overlapping area of curved parts, 15 closed area, 20 metal, 22 nonmetals, 3 heat dissipation members, 5 semiconductor devices, 50 semiconductor elements , 52 insulating substrate, 54 bonding material.

Claims

A substrate made of a composite material containing metal and nonmetal,
The substrate is
A large warpage portion having a spherical warpage with a radius of curvature R provided on the one surface,
And a small warpage portion partially provided in the large warpage portion and having a warpage different in size from the curvature radius R,
The curvature radius R is 5,000 mm or more and 35,000 mm or less,
The thermal conductivity of the substrate is at least 150 W / m · K,
The composite member whose linear expansion coefficient of the said board | substrate is 10 ppm / K or less.
The curvature radius R is 15000 mm or more and 25000 mm or less,
The composite member according to claim 1, wherein the amount of warpage of the small warpage portion is more than 30 μm and 70 μm or less.
The composite member according to claim 1, wherein the small warpage portion includes a circular portion in a plan view, and a diameter thereof is 5 mm or more and 150 mm or less.
The composite member according to any one of claims 1 to 3, comprising a plurality of the small warpage portions.
The composite member according to any one of claims 1 to 4, wherein the content of the nonmetal is 55% by volume or more.
The metal is magnesium, a magnesium alloy, aluminum or an aluminum alloy,
The composite member according to any one of claims 1 to 5, wherein the nonmetal includes SiC.
A composite member according to any one of claims 1 to 6,
And an insulating substrate bonded to the small warpage portion via a bonding material,
The heat radiating member whose curvature radius R of the said board | substrate in the state to which the said insulated substrate was joined is 5000 mm-35000 mm.
The heat dissipation member according to claim 7;
A semiconductor element mounted on the insulating substrate;
The semiconductor device whose curvature radius R of the said board | substrate in the state to which the said insulated substrate by which the said semiconductor element was mounted was joined is 5000 mm-35000 mm.
9. The semiconductor device according to claim 8, wherein a spherical error of the substrate in a state where the insulating substrate on which the semiconductor element is mounted is joined is 10.0 μm or less.
The semiconductor device according to claim 8, wherein a thickness of the insulating substrate is 1 mm or more.
Equipped with a pressing process for storing a material plate made of a composite material containing metal and nonmetal and carrying out heat pressing in a forming die,
The mold is
A large spherical surface portion having a spherical surface with a curvature radius Rb, and a small spherical surface portion partially provided on the large spherical surface portion and having a spherical surface having a curvature radius different from the curvature radius Rb;
The curvature radius Rb is 5,000 mm or more and 35,000 mm or less,
The pressing process is
A holding step of holding the heating temperature at 200 ° C. or higher and the applied pressure at 10 kPa or more for a predetermined time;
A cooling step of cooling from the heating temperature to 100 ° C. or less while maintaining a pressurized state of 80% or more of the applied pressure.