Composite materials, heat spreaders, and semiconductor packages

Abstract

The composite material comprises a plurality of first layers and a plurality of second layers. The sum of the number of first layers and second layers is 5 or more. The first layers and second layers are alternately stacked along the thickness direction of the composite material such that the first layer is located on a first surface and a second surface. The first layer is formed of a metal material having copper as the main component. The second layer has a molybdenum plate and a copper filler. The molybdenum plate includes a first surface and a second surface which are end surfaces in the thickness direction, and a plurality of openings that penetrate the molybdenum plate from the first surface to the second surface. The copper filler is disposed inside the openings. The thickness of the first layer located on the first surface is 0.025 mm or more and is also 30 percent or less of the thickness of the composite material. The thickness of the second layer in contact with the first layer located on the first surface is 0.05 mm or more and is also 35 percent or less of the thickness of the composite material.

Description

Technology Field

[0001] The present disclosure relates to composite materials, heat spreaders, and semiconductor packages. The present application claims priority based on Japanese Patent Application No. 2020-133776, filed on August 6, 2020. All contents of the said Japanese patent application are incorporated herein by reference. Background Technology

[0002] Patent Document 1 (Japanese Patent Publication No. 2018-18976) describes a heat dissipation substrate. The heat dissipation substrate described in Patent Document 1 has a core substrate, a first heat-conducting member, and a second heat-conducting member. The core substrate is formed of molybdenum (Mo). The first heat-conducting member and the second heat-conducting member are formed of copper (Cu). The core substrate has a first surface and a second surface opposite to the first surface. The first heat-conducting member and the second heat-conducting member are each disposed on the first surface and the second surface.

[0003] The core substrate has an opening penetrating the core substrate along the direction from the first surface to the second surface. An insert is disposed inside the opening. The insert is formed of copper. Prior art literature

[0004] Patent Document 1: Japanese Patent Publication No. 2018-18976

[0005] The composite material of the present disclosure is plate-shaped and has a first surface and a second surface opposite to the first surface. The composite material has a plurality of first layers and a plurality of second layers. The sum of the number of first layers and the number of second layers is 5 or more. The first layers and second layers are alternately stacked along the thickness direction of the composite material such that the first layer is located on the first surface and the second surface. The first layer is formed of a metal material having copper as the main component. The second layer has a molybdenum plate and a copper filler. The molybdenum plate includes a first surface and a second surface which are end surfaces in the thickness direction, and a plurality of openings penetrating the molybdenum plate from the first surface to the second surface. The copper filler is disposed inside the openings. The thickness of the first layer located on the first surface is 0.025 mm or more and is also 30 percent or less of the thickness of the composite material. The thickness of the second layer in contact with the first layer located on the first surface is 0.05 mm or more and is also 35 percent or less of the thickness of the composite material. The number of openings is 1 mm² of the area of ​​the first surface. 2 The ratio of the average value of the maximum circle equivalent diameter of the opening to the thickness of the second layer is 0.3 or more and 5.0 or less. Brief explanation of the drawing

[0006] Figure 1 is a perspective view of a composite material (10). Figure 2 is a cross-sectional view of a composite material (10). Figure 3 is a plan view of a molybdenum plate (13). FIG. 4a is a first explanatory diagram illustrating the procedure for preparing a sample for measuring the thermal conductivity in the thickness direction of a composite material (10). FIG. 4b is a second explanatory diagram illustrating the procedure for preparing a sample for measuring the thermal conductivity in the thickness direction of a composite material (10). FIG. 4c is a third explanatory diagram illustrating the procedure for preparing a sample for measuring the thermal conductivity in the thickness direction of a composite material (10). FIG. 5 is an explanatory diagram of a method for evaluating the heat dissipation performance of a composite material (10). FIG. 6 is a cross-sectional view of a composite material (10) according to a first modified example. FIG. 7 is a cross-sectional view of a composite material (10) according to a second modified example. FIG. 8 is a process diagram illustrating a method for manufacturing a composite material (10). FIG. 9 is an exploded perspective view of a semiconductor package (100). Specific details for implementing the invention

[0007] [Problems to be solved by the present disclosure]

[0008] The heat dissipation substrate described in Patent Document 1 has room for improvement in the compatibility of a low linear expansion coefficient and high heat dissipation.

[0009] The present disclosure has been made in consideration of the problems of the prior art as described above. More specifically, the present disclosure provides a composite material capable of achieving both a low coefficient of linear expansion and high heat dissipation.

[0010] [Effects of the present disclosure]

[0011] According to the composite material of the present disclosure, a low coefficient of linear expansion and high heat dissipation can be achieved simultaneously.

[0012] [Description of embodiments of the present disclosure]

[0013] First, embodiments of the present disclosure will be described.

[0014] (1) A composite material according to one embodiment is plate-shaped and has a first surface and a second surface opposite to the first surface. The composite material has a plurality of first layers and a plurality of second layers. The sum of the number of first layers and the number of second layers is 5 or more. The first layers and second layers are alternately stacked along the thickness direction of the composite material such that the first layer is located on the first surface and the second surface. The first layer is formed of a metal material with copper as the main component. The second layer has a molybdenum plate and a copper filler. The molybdenum plate includes a first surface and a second surface which are end surfaces in the thickness direction, and a plurality of openings that penetrate the molybdenum plate from the first surface to the second surface. The copper filler is disposed inside the openings. The thickness of the first layer located on the first surface is 0.025 mm or more and is also 30 percent or less of the thickness of the composite material. The thickness of the second layer in contact with the first layer located on the first surface is 0.05 mm or more and is also 35 percent or less of the thickness of the composite material. The number of openings is 1 mm² of the area of ​​the first surface. 2 The ratio of the average value of the maximum circle equivalent diameter of the opening to the thickness of the second layer is 0.3 or more and 5.0 or less.

[0015] According to the composite material according to (1) above, a low linear expansion coefficient and high heat dissipation can be achieved simultaneously.

[0016] (2) In the composite material of (1) above, the ratio of the average value of the maximum value of the circle equivalent diameter of the opening to the thickness of the second layer may be 1.6 or more and less than 5.0.

[0017] (3) In the composite material of (1) or (2) above, the thermal conductivity in the thickness direction may be 290 W / m·K or higher at room temperature. The coefficient of linear expansion in the in-layer direction orthogonal to the thickness direction when the temperature changes from room temperature to 800°C may be 9.0 ppm / K or lower.

[0018] (4) In the composite material of (3) above, the end temperature difference may be 50℃ or less.

[0019] (5) In the composite material of (1) or (2) above, the thermal conductivity in the thickness direction may be 300 W / m·K or higher at room temperature. The coefficient of linear expansion in the in-layer direction orthogonal to the thickness direction when the temperature changes from room temperature to 800°C may be 8.5 ppm / K or lower.

[0020] (6) In the composite material of (5) above, the end temperature difference may be 40℃ or less.

[0021] (7) In the composite materials of (1) to (6) above, the average value of the circle-equivalent diameter of the opening in the first surface and the average value of the circle-equivalent diameter of the opening in the second surface may be 0.05 mm or more and 0.35 mm or less.

[0022] (8) In the composite materials of (1) to (7) above, the average value of the minimum opening area of ​​the opening may be 57 percent or more and 100 percent or less of the average value of the maximum opening area of ​​the opening.

[0023] (9) In the composite materials of (1) to (8) above, the sum of the number of the first layer and the number of the second layer may be 9 or less.

[0024] (10) A heat spreader according to one embodiment is provided with the composite material of (1) through (9). The first surface of the composite material is a contact surface with a heat source.

[0025] (11) A semiconductor package according to one embodiment comprises the composite material of (1) through (9) and a semiconductor element disposed on the first surface of the composite material.

[0026] (12) The semiconductor package of (11) above may further include a case member formed of a ceramic material. The case member is disposed on a first surface to surround the semiconductor element.

[0027] [Details of embodiments of the present disclosure]

[0028] Next, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following drawings, the same or equivalent parts are given the same reference numerals, and redundant descriptions are not repeated.

[0029] (Composition of composite material according to embodiment)

[0030] Below, the composition of a composite material according to an embodiment (hereinafter referred to as “composite material (10)”) is described.

[0031] FIG. 1 is a perspective view of a composite material (10). As shown in FIG. 1, the composite material (10) has a plate-like shape. The composite material (10) has a first surface (10a) and a second surface (10b). The first surface (10a) and the second surface (10b) are end surfaces in the thickness direction of the composite material (10). That is, the second surface (10b) is the opposite surface of the first surface (10a) in the thickness direction of the composite material (10).

[0032] FIG. 2 is a cross-sectional view of a composite material (10). As shown in FIG. 2, the composite material (10) has a plurality of first layers (11) and a plurality of second layers (12). In the example shown in FIG. 2, the number of first layers (11) is 4, the number of second layers (12) is 3, and the total number of first layers (11) and second layers (12) is 7.

[0033] The first layer (11) and the second layer (12) are alternately stacked along the thickness direction of the composite material (10) such that one of the first layers (11) is located on the first surface (10a) and the other of the first layers (11) is located on the second surface (10b). The second layer (12) is sandwiched between the two first layers (11) along the thickness direction of the composite material (10). The thickness of the composite material (10) is set to thickness T1.

[0034] The first layer (11) is formed from a metal material with copper as the main component. Here, "metal material with copper as the main component" refers to a metal material having a copper content of 50 mass percent or more. The metal material with copper as the main component is preferably a copper alloy containing 70 mass percent or more of copper. The first layer (11) is formed, for example, from pure copper. Here, pure copper is a metal material consisting of copper and unavoidable impurities constituting the remainder.

[0035] Among the first layers (11), the one located on the first surface (10a) is designated as the first layer (11a). Among the first layers (11), the one located on the second surface (10b) is designated as the first layer (11b). The thickness of the first layer (11) is set to thickness T2. The thickness (T2) of the first layer (11a) (first layer (11b)) is 0.025 mm or more and is also 30 percent or less of the thickness (T1).

[0036] The second layer (12) has a molybdenum plate (13) and a copper filler (14). The molybdenum plate (13) is formed from a metal material with molybdenum as the main component. "Metal material with molybdenum as the main component" is a metal material having a molybdenum content of 50 mass percent or more. It is preferable that the metal material with molybdenum as the main component contains 70 mass percent or more of molybdenum. The molybdenum plate (13) is formed, for example, from pure molybdenum. Pure molybdenum is a metal material consisting of molybdenum and unavoidable impurities constituting the remainder. The copper filler (14) is formed from a metal material with copper as the main component. The copper filler (14) is formed, for example, from pure copper. The copper filler (14) is preferably formed from the same material as the first layer (11).

[0037] The molybdenum plate (13) is a plate-like body. The molybdenum plate (13) has a first surface (13a) and a second surface (13b). The first surface (13a) and the second surface (13b) are end surfaces in the thickness direction of the composite material (10). That is, the second surface (13b) is the opposite surface of the first surface (13a) in the thickness direction of the composite material (10).

[0038] The molybdenum plate (13) has a plurality of openings (13c). The openings (13c) penetrate the molybdenum plate (13) along the direction from the first surface (13a) to the second surface (13b). Area of ​​the first surface (10a) (second surface (10b)) 1 mm 2 The number of openings (13c) per opening (the value obtained by dividing the total number of openings (13c) by the area of ​​the first surface (10a) (the second surface (10b))) is between 2 and 12. Copper filler (14) is placed inside the openings (13c).

[0039] Among the second layer (12), the one in contact with the first layer (11a) is designated as the second layer (12a). Among the second layer (12), the one in contact with the first layer (11b) is designated as the second layer (12b). The thickness of the second layer (12) is set to thickness T3. The thickness (T3) of the second layer (12a) (second layer (12b)) is 0.05 mm or more and is also 35 percent or less of the thickness (T1).

[0040] FIG. 3 is a plan view of a molybdenum plate (13). As shown in FIG. 3, the opening (13c) has a circular shape when viewed in a planar view. However, the shape of the opening (13c) when viewed in a planar view is not limited to a circular shape. The opening (13c) may be any of the following shapes when viewed in a planar view:, for example, an elliptical shape, a polygonal shape, or any other shape. The diameter of the opening (13c) when viewed in a planar view is defined as the opening diameter (D). The opening diameter (D) can be obtained by calculating the square root of the value obtained by dividing the area of ​​the opening (13c) when viewed in a planar view by π / 4.

[0041] The opening diameter (D) may be constant across the first surface (13a) and the second surface (13b). The opening diameter (D) may vary between the first surface (13a) and the second surface (13b), or it may not be constant between the first surface (13a) and the second surface (13b). If the opening diameter (D) varies between the first surface (13a) and the second surface (13b), the opening diameter (D) may decrease as it extends from one side of the first surface (13a) and the second surface (13b) toward the other side of the first surface (13a) and the second surface (13b). In any one of the openings, the maximum value of the opening diameter (D) in the thickness direction is the opening diameter (D max ...does it as ).

[0042] Opening diameter (D max Average value of ) (opening diameter (D max The sum of the sum for all openings (13c) and the value obtained by dividing the sum by the total number of openings (13c) is defined as the average circle equivalent diameter. For one second layer (12), the value obtained by dividing the average circle equivalent diameter by the thickness (T3), i.e., the ratio of the average circle equivalent diameter to the thickness (T3), is 0.3 or greater and 5.0 or less. It is preferable that the ratio of the average circle equivalent diameter to the thickness (T3) is 1.6 or greater and less than 5.0.

[0043] It is preferable that the average value of the opening diameter (D) in the first surface (13a) (the sum of the opening diameter (D) in the first surface (13a) for all openings (13c) and the sum divided by the total number of openings (13c)) and the average value of the opening diameter (D) in the second surface (13b) (the sum of the opening diameter (D) in the second surface (13b) for all openings (13c) and the sum divided by the total number of openings (13c)) are each 0.05 mm or more and 0.35 mm or less.

[0044] The opening area of ​​the opening (13c) is measured on a plane parallel to the first plane (13a). The minimum opening area of ​​the opening (13c) when measured between the first plane (13a) and the second plane (13b) along the thickness direction of the molybdenum plate (13) is defined as the minimum opening area of ​​the opening (13c). The maximum opening area of ​​the opening (13c) when measured between the first plane (13a) and the second plane (13b) along the thickness direction of the molybdenum plate (13) is defined as the maximum opening area of ​​the opening (13c). It is more preferable that the average value of the minimum opening area of ​​the opening (13c) (the sum of the minimum opening areas of the opening (13c) for all openings (13c) and the sum divided by the total number of openings (13c)) is 57 percent or more and 100 percent or less of the average value of the maximum opening area of ​​the opening (13c) (the sum of the maximum opening area of ​​the opening (13c) for all openings (13c) and the sum divided by the total number of openings (13c)).

[0045] It is preferable that the thermal conductivity in the thickness direction of the composite material (10) be 290 W / m·K or higher at room temperature. It is preferable that the thermal conductivity in the thickness direction of the composite material (10) be 300 W / m·K or higher at room temperature. Here, "room temperature" refers to 27℃.

[0046] The thermal conductivity in the thickness direction of the composite material (10) is measured using the laser flash method. In the laser flash method, the thermal diffusion coefficient of the composite material (10) is measured using LFA457MicroFlash (manufactured by NETZSCH), and the thermal conductivity in the thickness direction of the composite material (10) is calculated based on the thermal diffusion coefficient, the volume ratio of each constituent material of the composite material (10), and the specific heat. In calculating the thermal conductivity, the specific heat of each constituent material is determined based on the "Metal Data Book 4th Edition" (2004, Maruzen Publishing) edited by the Institute of Metallurgy of Japan. In addition, prior to measuring the thermal conductivity of the composite material (10), the thermal conductivity of a pure copper sample of the same shape is measured under the same conditions, and the measurement result is corrected using the result as a reference.

[0047] FIG. 4a is a first explanatory diagram illustrating the procedure for preparing a sample for measuring the thermal conductivity in the thickness direction of a composite material (10). As shown in FIG. 4a, a thin slice (15) is cut from the composite material (10) to be measured. The thickness, length, and width of the thin slice (15) are t (mm), B (mm), and C (mm), respectively.

[0048] X is the number obtained by rounding the decimal part of the value obtained by dividing 2 by t. Y1 is the number obtained by rounding the decimal part of the value obtained by dividing 10 by B. Y2 is the number obtained by rounding the decimal part of the value obtained by dividing 10 by C. A number of thin slices (15) equal to the product of X, Y1, and Y2 are cut from the composite material (10) to be measured.

[0049] FIG. 4b is a second explanatory diagram illustrating the procedure for preparing a sample for measuring the thermal conductivity in the thickness direction of a composite material (10). As shown in FIG. 4b, a block (16) is produced from X sheets of thin slices (15). The thickness, length, and width of the block (16) are approximately 2 mm, B mm, and C mm, respectively. In producing the block (16), X sheets of thin slices (15) are first overlapped. At this time, an irregular powder formed from pure silver with an average particle size of 4 μm is placed between adjacent sheets (15). The amount of irregular powder placed between adjacent sheets (15) is 100 mm 2 It is 0.2 g ± 30 percent per gram.

[0050] In the production of the block (16), secondly, a rectangular shape (not shown) is prepared in which an opening with an eye size of B (mm) × C (mm) is formed, and an overlapping flake (15) is placed within the opening. The above shape is made of graphite. In the production of the block (16), thirdly, the overlapping flake (15) is heat-treated while a load (P) is applied. The load (P) is 4.9 N or more and 9.8 N or less. The heat treatment is carried out in an inert gas atmosphere. The heat treatment is performed at a holding temperature of 900°C and a holding time of 10 minutes. Through the heat treatment, the irregular powder is softened and deformed, and the adjacent flake (15) is bonded together to produce the block (16).

[0051] FIG. 4c is a third explanatory diagram illustrating the procedure for preparing a sample for measuring the thermal conductivity in the thickness direction of a composite material (10). As shown in FIG. 4c, by arranging blocks (16) in a vertical Y-shape and horizontal Y-shape, a measurement sample (17) with a height of approximately 10 mm, a width of approximately 10 mm, and a thickness of approximately 2 mm is produced. When arranging blocks (16) in a vertical Y-shape and horizontal Y-shape, adjacent blocks (16) are bonded to each other by an adhesive member. For the adhesive member, materials capable of withstanding temperatures up to approximately 800°C, such as silver brazing foil or ceramic adhesive, are used. The blocks (16) arranged in a vertical Y-shape and horizontal Y-shape may be fixed by wrapping a stainless steel wire or the like around their outer circumference.

[0052] It is preferable that the linear expansion coefficient in the in-layer direction (direction orthogonal to the thickness direction) of the composite material (10) when the temperature changes from room temperature to 800°C be 9.0 ppm / K or less. It is even more preferable that the linear expansion coefficient in the in-layer direction of the composite material (10) when the temperature changes from room temperature to 800°C be 8.5 ppm / K or less.

[0053] The linear expansion coefficient in the in-layer direction of the composite material (10) when the temperature changes from room temperature to 800°C is calculated by measuring the expansion displacement in the in-layer direction of the composite material (10) in the temperature range from room temperature to 800°C using a TDS5000SA (manufactured by Bruker AXS). When calculating the linear expansion coefficient in the in-layer direction of the composite material (10) when the temperature changes from room temperature to 800°C, the planar shape of the composite material (10) is a rectangular shape of 3 mm × 15 mm. The measured value is the average value for three samples.

[0054] It is preferable that the temperature difference at the ends of the composite material (10) be 50°C or less. It is even more preferable that the temperature difference at the ends of the composite material (10) be 40°C or less. FIG. 5 is an explanatory diagram of a method for evaluating the heat dissipation performance of the composite material (10). FIG. 5 schematically illustrates the state of the composite material (10) viewed from one side. The composite material (10) is cut into a rectangle with a length and width of 10 mm when viewed from a direction perpendicular to the first surface (10a). A heating element (70) is in contact with the center of the first surface (10a) of the cut composite material (10). The heating element (70) is a rectangle with a length and width of 10 mm when viewed from a direction perpendicular to the first surface (10a). The heat output of the heating element (70) is 50 W.

[0055] An aluminum pin (80) is bonded to the second surface (10b) of the cut composite material (10) using silicone oil (Shin-Etsu Kagaku Co., Ltd. G-751). This bonding is achieved by applying a load of 9.8 N while the silicone oil is placed between the second surface (10b) of the cut composite material (10) and the aluminum pin (80).

[0056] The temperature at the interface between the first surface (10a) of the cut composite material (10) and the heating element (70) is set as the first temperature. The temperature at the end (corner) of the first surface (10a) of the cut composite material (10) is set as the second temperature. The temperature at the interface between the second surface (10b) of the cut composite material (10) and the aluminum fin (80) is set as the third temperature. The first temperature, the second temperature, and the third temperature are measured by a thermocouple not shown. Air cooling of the aluminum fin (80) is controlled so that the third temperature becomes 25°C ± 3°C. The ambient temperature as the measurement environment is 25°C ± 5°C.

[0057] After the heating element (70) is brought into contact with the first surface (10a) of the cut composite material (10), the difference between the first temperature and the second temperature (first temperature - second temperature) when the temperature returns to a normal state after 30 seconds or more has elapsed is the end temperature difference of the composite material (10). This end temperature difference is measured 10 times, and the average value is adopted. That is, the end temperature difference of the composite material (10) is the difference between the temperature at the part of the first surface (10a) where the heating element (70) is in contact and the temperature at the end (corner) of the first surface (10a) when the heating element (70) is in contact with the first surface (10a) and the aluminum pin (80) is attached to the second surface (10b). The smaller the end temperature difference, the better the heat conduction in the layer direction of the composite material (10).

[0058] <Variation Example>

[0059] FIG. 6 is a cross-sectional view of a composite material (10) according to a first modified example. FIG. 7 is a cross-sectional view of a composite material (10) according to a second modified example. As shown in FIG. 6, the sum of the number of the first layer (11) and the number of the second layer (12) may be 5. As shown in FIG. 7, the sum of the number of the first layer (11) and the number of the second layer (12) may be 9.

[0060] (Method for manufacturing a composite material according to an embodiment)

[0061] The method for manufacturing the composite material (10) is described below.

[0062] FIG. 8 is a process diagram illustrating a method for manufacturing a composite material (10). As shown in FIG. 8, the method for manufacturing a composite material (10) includes a preparation process S1, a drilling process S2, and a bonding process S3.

[0063] In preparation process S1, a first plate and a second plate are prepared. The first plate is a plate formed from a metal material with copper as the main component. The second plate is formed from a metal material with molybdenum as the main component.

[0064] In the hole-drilling process S2, a hole-drilling process is performed on the second plate. Through the hole-drilling process, a plurality of openings are formed in the second plate that penetrate the second plate in the thickness direction. As a result, the second plate becomes a molybdenum plate (13). The hole-drilling process on the second plate is performed, for example, by etching or laser irradiation.

[0065] In the bonding process S3, first, a first plate and a molybdenum plate (13) are alternately stacked within a mold (hereinafter, the alternately stacked first plate and molybdenum plate (13) is referred to as a laminate). The mold is formed, for example, of graphite. The stacking of the first plate and the molybdenum plate (13) is performed such that the first plate is positioned on the surface of the laminate.

[0066] In the bonding process S3, heating and pressurizing are performed on the laminate secondly. The heating temperature is below the melting point of the first plate and is also a temperature at which the first plate is sufficiently softened. The heating temperature is, for example, 1000°C. Pressurizing is performed along the thickness direction of the laminate. Pressurizing is performed at a pressure necessary to make the first plate, softened by heating, flow. Pressurizing is performed at, for example, a pressure of 50 MPa.

[0067] As a result of the first plate material flowing due to the heating and pressurization described above, the first plate material is filled into the opening (13c) of the molybdenum plate (13) and becomes a copper filler (14). Additionally, the remainder of the first plate material that is not filled into the opening (13c) becomes the first layer (11).

[0068] (Configuration of a semiconductor package according to an embodiment)

[0069] The configuration of a semiconductor package (hereinafter referred to as "semiconductor package (100)" according to an embodiment is described below.

[0070] FIG. 9 is an exploded perspective view of a semiconductor package (100). As shown in FIG. 9, the semiconductor package (100) has a composite material (10), a semiconductor element (20), a case member (30), a cover (40), a terminal (50a), and a terminal (50b).

[0071] The composite material (10) functions as a heat spreader in the semiconductor package (100). A semiconductor element (20) is disposed on a first surface (10a). A heat transfer member may be interposed between the semiconductor element (20) and the first surface (10a). The semiconductor element (20) becomes a heat source during operation.

[0072] The case member (30) is formed of, for example, a ceramic material. The ceramic material is, for example, alumina (Al2O3). The case member (30) is positioned on a first surface (10a) to surround a semiconductor device (20). The bottom of the case member (30) (the end on the side of the first surface (10a)) and the first surface (10a) are joined, for example, by soldering. The cover (40) is formed of, for example, a ceramic material or a metal material. The cover (40) closes the top side of the case member (30).

[0073] Terminals (50a) and (50b) are inserted into the case member (30). As a result, one end of terminals (50a) and (50b) is located within the space formed by the first surface (10a), the case member (30), and the cover (40), and the other end of terminals (50a) and (50b) is located outside the space. Terminals (50a) and (50b) are formed of, for example, a metal material. The metal material is, for example, cobalt.

[0074] Although not shown, one end of terminal (50a) and terminal (50b) is electrically connected to a semiconductor device (20). The semiconductor package (100) is electrically connected to a device or circuit different from the semiconductor package (100) at the other end of terminal (50a) and terminal (50b).

[0075] A heat dissipation member (60) is attached to the second surface (10b). The heat dissipation member (60) is, for example, a metal plate having a channel formed therein for refrigerant to flow. However, the heat dissipation member (60) is not limited to this. The heat dissipation member (60) may be, for example, a cooling fin. A heat transfer member may be interposed between the heat dissipation member (60) and the second surface (10b).

[0076] (Effect of composite material according to embodiment)

[0077] The effects of the composite material (10) are explained below.

[0078] In order to efficiently dissipate heat from a heat source from the first surface (10a) (second surface (10b)), it is effective to diffuse the heat from the heat source along the layer direction by increasing the thermal conductivity on the side of the first surface (10a) (second surface (10b)).

[0079] In the composite material (10), the thickness (T2) of the first layer (11a) (first layer (11b)), which has a relatively high thermal conductivity, is secured to be 0.025 mm or more. Therefore, according to the composite material (10), heat from the heat source can be efficiently dissipated from the first surface (10a) (second surface (10b)).

[0080] The composite material (10) is exposed to a high temperature (e.g., about 800°C) when, for example, a case member (30) is soldered. Therefore, the composite material (10) is required to have small thermal expansion when exposed to a high temperature. In the composite material (10), the thickness (T3) of the second layer (12a) (second layer (12b)), which has a relatively low coefficient of linear expansion, is secured to be 0.05 mm or more. In addition, in the composite material (10), by making the thickness (T2) of the first layer (11a) (first layer (11b)) 30 percent or less of the thickness (T1), the first layer (11a) (first layer (11b)), which has a relatively high coefficient of linear expansion, is not made excessively thick. Therefore, according to the composite material (10), thermal expansion when exposed to a high temperature is suppressed.

[0081] In order to improve the heat dissipation of the composite material (10), it is required to increase not only the thermal conductivity on the first surface (10a) (second surface (10b)) side, but also the overall thermal conductivity of the composite material (10). However, if the proportion of molybdenum in the composite material (10) is increased, the overall linear expansion coefficient of the composite material (10) decreases, while the overall thermal conductivity of the composite material (10) decreases.

[0082] Area of ​​the first surface (10a) (second surface (10b)) 1 mm 2 As the number of openings (13c) increases, or as the value obtained by dividing the average circular equivalent diameter of the openings (13c) by the thickness (T3) increases, the proportion of molybdenum in the composite material (10) decreases, and the thermal conductivity of the entire composite material (10) decreases. In addition, as the thickness (T3) of the second layer (12a) (second layer (12b)) increases, the proportion of molybdenum in the composite material (10) increases, and the overall thermal conductivity of the composite material (10) decreases.

[0083] In the composite material (10), the number of openings (13c) is 1 mm² of the area of ​​the first surface (10a) (second surface (10b)). 2The value is set to be between 2 and 12, and the value obtained by dividing the average circle equivalent diameter of the opening (13c) by the thickness (T3) is between 0.3 and 5.0. In addition, in the composite material (10), the thickness (T3) of the second layer (12a) (second layer (12b)) is less than or equal to 35 percent of the thickness (T1), so that the thickness (T3) of the second layer (12a) (second layer (12b)) does not become excessively thick. Therefore, according to the composite material (10), a balance between thermal conductivity and linear expansion coefficient is maintained throughout the composite material (10).

[0084] According to the above, the composite material (10) can achieve both a low linear expansion coefficient and high heat dissipation.

[0085] (Experimental Example)

[0086] Samples 1 to 48 were prepared to verify the effect of the composite material (10). In samples 1 to 48, the first layer (11) was formed of pure copper. In samples 1 to 48, the molybdenum plate (13) was formed of pure molybdenum, and the copper filler (14) was formed of pure copper.

[0087] Tables 1, 2, and 3 describe the dimensions of the composite material (10) in samples 1 to 48. Since the thickness (T2) other than the first layer (11a) and the first layer (11b) is determined from the thickness (T1) of the composite material (10), the thickness (T2) of the first layer (11a) and the first layer (11b), and the thickness (T3) of the second layer (12), it is omitted from Tables 1 to 3. Additionally, in samples 27 to 48, the thickness (T3) of the second layer (12a) and the second layer (12b) is the same as the thickness (T3) of the second layer (12) other than the second layer (12a) and the second layer (12b).

[0088] Condition A is that the thickness (T1) of the first layer (11a) (first layer (11b)) is 0.025 mm or more and is also 30 percent or less of the thickness (T3). Condition B is that the thickness (T2) of the second layer (12a) (second layer (12b)) is 0.05 mm or more and is also 30 percent or less of the thickness (T3).

[0089] Area of ​​the first surface (10a) (second surface (10b)) 1 mm 2 Condition C is that the number of openings (13c) is 2 or more and 12 or less. Condition D is that the value obtained by dividing the average circular equivalent diameter of the openings (13c) by the thickness (T3) is 0.3 or more and 5.0 or less. Condition E is that the value obtained by dividing the average circular equivalent diameter of the openings (13c) by the thickness (T3) is 1.6 or more and less than 5.0.

[0090] In samples 1 to 3, sample 8, sample 12, sample 15, sample 27, sample 32, sample 39, and sample 43, at least one of conditions A to D was not satisfied. In the other samples, all of conditions A to D were satisfied.

[0091] In samples 4–7, 13, 14, 18–22, 28–31, 34, 36–38, 40–42, and 44–48, condition E was additionally satisfied.

[0092]

[0093]

[0094]

[0095] For samples 1 to 48, the thermal conductivity in the thickness direction, the coefficient of linear expansion in the layer direction when the temperature changed from room temperature to 800°C, and the end temperature difference were measured.

[0096] Tables 4, 5, and 6 show the measurement results of the thermal conductivity in the thickness direction, the coefficient of linear expansion in the in-layer direction, and the end temperature difference when the temperature is changed from room temperature to 800°C for samples 1 to 48.

[0097]

[0098]

[0099]

[0100] Condition F is defined as having a thermal conductivity in the thickness direction of 290 W / m·K or higher. Condition G is defined as having a linear expansion coefficient in the in-layer direction of 9.0 ppm / K or lower when the temperature changes from room temperature to 800°C. Condition H is defined as having an end temperature difference of 50°C or lower.

[0101] In samples 1 to 3, sample 8, sample 12, sample 15, sample 27, sample 32, sample 39, and sample 43, at least one of conditions F to H was not satisfied. On the other hand, in the other samples, all of conditions F to H were satisfied. From this comparison, it was experimentally revealed that the low linear expansion coefficient and high heat dissipation of the composite material (10) are compatible by satisfying all of conditions A to D.

[0102] Condition I is defined as having a thermal conductivity in the thickness direction of 300 W / m·K or higher. Condition J is defined as having a linear expansion coefficient in the in-layer direction of 8.5 ppm / K or lower when the temperature changes from room temperature to 800°C. Condition K is defined as having an end temperature difference of 40°C or lower.

[0103] In samples 4 to 7, samples 13, samples 14, samples 18 to 22, samples 28 to 31, samples 34, samples 36 to 38, samples 40 to 42, and samples 44 to 48, conditions I to K were additionally satisfied. From this comparison, it was experimentally revealed that the low linear expansion coefficient and high heat dissipation of the composite material (10) are compatible to an even higher level by additionally satisfying condition E.

[0104] The embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the invention is defined by the claims, not by the embodiments described above, and is intended to include all modifications within the meaning and scope equivalent to the claims. Explanation of the symbols

[0105] 10: Composite material, 10a: First surface, 10b: Second surface, 11, 11a, 11b: First layer, 12, 12a, 12b: Second layer, 13: Molybdenum plate, 13a: First surface, 13b: Second surface, 13c: Opening, 14: Copper filler, 15: Flake, 16: Block, 17: Measurement sample, 20: Semiconductor device, 30: Case member, 40: Cover, 50a, 50b: Terminal, 60: Heat dissipation member, 70: Heating element, 80: Aluminum fin, 100: Semiconductor package, D: Opening diameter, S1: Preparation process, S2: Drilling process, S3: Bonding process, T1, T2, T3: Thickness.

Claims

Claim 1 A plate-shaped composite material having a first surface and a second surface opposite to the first surface, comprising a plurality of first layers and a plurality of second layers, wherein the sum of the number of the first layers and the number of the second layers is 5 or more, and the first layers and the second layers are alternately stacked along the thickness direction of the composite material, wherein the layer constituting the first surface and the second surface is the first layer, and the first layer is formed of a metal material having copper as a main component, and the second layer has a molybdenum plate and a copper filler, wherein the molybdenum plate has a plurality of openings penetrating the molybdenum plate in the thickness direction, and the copper filler is arranged to fill the interior of the openings, wherein the thickness of the first layer constituting the first surface is 0.025 mm or more and is also 30 percent or less of the thickness of the composite material, and the thickness of the second layer in contact with the first layer constituting the first surface is 0.05 mm or more and is also of the thickness of the composite material 35 percent or less, and in any one of the above second layers, the number of openings is an area of ​​1 mm² of the first surface 2 A composite material having a value of 2 or more and 12 or less, a value obtained by dividing the average circular equivalent diameter of the opening by the thickness of the second layer being 0.3 or more and 5.0 or less, a thermal conductivity in the thickness direction being 290 W / m·K or more at room temperature, and a linear expansion coefficient in the in-layer direction orthogonal to the thickness direction being 9.0 ppm / K or less when the temperature changes from room temperature to 800℃. Claim 2 A composite material according to claim 1, wherein the value obtained by dividing the average circle-equivalent diameter of the opening by the thickness of the second layer is 1.6 or more and less than 5.

0. Claim 3 delete Claim 4 A composite material according to claim 1, wherein the end temperature difference is 50℃ or less. Claim 5 A composite material according to claim 1, wherein the thermal conductivity in the thickness direction is 300 W / m·K or higher at room temperature, and the coefficient of linear expansion in the in-layer direction orthogonal to the thickness direction is 8.5 ppm / K or lower when the temperature changes from room temperature to 800℃. Claim 6 A composite material according to claim 5, wherein the end temperature difference is 40℃ or less. Claim 7 A composite material according to claim 1, wherein the molybdenum plate has a first surface and a second surface which are end surfaces in the thickness direction, and the average value of the circle-equivalent diameter of the opening in the first surface and the average value of the circle-equivalent diameter of the opening in the second surface are 0.05 mm or more and 0.35 mm or less. Claim 8 A composite material according to claim 1, wherein the average value of the minimum opening area of ​​the opening is 57 percent or more and 100 percent or less of the average value of the maximum opening area of ​​the opening. Claim 9 A composite material according to claim 1, wherein the sum of the number of the first layer and the number of the second layer is 9 or less. Claim 10 A heat spreader having the composite material described in any one of claims 1, 2, 4 to 9, wherein the first surface is a contact surface with a heat source. Claim 11 A semiconductor package comprising the composite material described in any one of claims 1, 2, 4 through 9, and a semiconductor element disposed on the first surface. Claim 12 A semiconductor package according to claim 11, further comprising a case member formed of a ceramic material, wherein the case member is disposed on the first surface to surround the semiconductor element. Claim 13 A plate-shaped composite material having a first surface and a second surface opposite to the first surface, comprising a plurality of first layers and a plurality of second layers, wherein the sum of the number of the first layers and the number of the second layers is 5 or more and 9 or less, wherein the first layers and the second layers are alternately stacked along the thickness direction of the composite material, wherein the layer constituting the first surface and the second surface is the first layer, wherein the first layer is formed of a metal material having copper as a main component, wherein the second layer has a molybdenum plate and a copper filler, wherein the molybdenum plate has a plurality of openings penetrating the molybdenum plate in the thickness direction, and the copper filler is arranged to fill the interior of the openings, wherein the thickness of the first layer constituting the first surface is 0.025 mm or more and is also 30 percent or less of the thickness of the composite material, and the thickness of the second layer in contact with the first layer constituting the first surface is 0.05 mm or more and also of the composite material The thickness is 35 percent or less, and in any one of the second layers, the number of openings is 1 mm² of the area of ​​the first surface. 2 A composite material having a value of 2 or more and 12 or less, a value obtained by dividing the average circular equivalent diameter of the opening by the thickness of the second layer being 0.3 or more and 5.0 or less, a thermal conductivity in the thickness direction being 290 W / m·K or more at room temperature, a coefficient of linear expansion in the in-layer direction orthogonal to the thickness direction being 9.0 ppm / K or less when the temperature changes from room temperature to 800℃, and the molybdenum plate having a first surface and a second surface which are end surfaces in the thickness direction, the average value of the circular equivalent diameter of the opening in the first surface and the average value of the circular equivalent diameter of the opening in the second surface being 0.05 mm or more and 0.35 mm or less, and the average value of the minimum opening area of ​​the opening being 57 percent or more and 100 percent or less of the average value of the maximum opening area of ​​the opening.

Images