Composite material, heat sink and semiconductor package

Abstract

The composite material has a plurality of first layers and a plurality of second layers. The number of the first layers and the number of the second layers are 5 or more in total. The first layers and the second layers are alternately stacked in a thickness direction of the composite material in a manner that the first layers are located on a first surface and a second surface. The first layers are formed of a metal material in which copper is a main component. The second layers have a molybdenum plate and a copper filler. The molybdenum plate includes end surfaces in the thickness direction, i.e., a first surface and a second surface, and a plurality of opening portions that penetrate the molybdenum plate from the first surface toward the second surface. The copper filler is disposed inside the opening portions. A thickness of the first layer located on the first surface is 0.025 mm or more and 30% or less of a thickness of the composite material. A thickness of the second layer in contact with the first layer located on the first surface is 0.05 mm or more and 35% or less of the thickness of the composite material.

Description

Technical Field

[0001] This disclosure relates to composite materials, heat sinks, and semiconductor packaging. This application claims priority to Japanese Patent Application No. 2020-133776, filed on August 6, 2020. All descriptions in that Japanese patent application are incorporated herein by reference. Background Technology

[0002] A heat dissipation substrate is described in Patent Document 1 (Japanese Patent Application Publication No. 2018-18976). 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 and second heat-conducting members are formed of copper (Cu). The core substrate has a first surface and a second surface opposite to the first surface. The first and second heat-conducting members are respectively disposed on the first and second surfaces.

[0003] The core substrate has an opening extending through it in a direction from a first surface toward a second surface. An insert is disposed inside the opening. The insert is made of copper.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-18976 Summary of the Invention

[0007] The composite material disclosed herein is plate-shaped, having a first surface and a second surface opposite to the first surface. The composite material has multiple first layers and multiple second layers. The total number of first layers and second layers is 5 or more. The first and second layers are alternately stacked along the thickness direction of the composite material, with the first layer located on the first and second surfaces. The first layer is formed of a metallic material with copper as its main component. The second layer has a molybdenum plate and copper filler. The molybdenum plate includes end faces in the thickness direction, i.e., the first and second surfaces, and multiple openings penetrating the molybdenum plate from the first surface toward 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 less than 30% 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 less than 35% of the thickness of the composite material. The number of openings is [missing information - likely a number per 1 mm of the first surface]. 2 The area is 2 or more and 12 or less. The ratio of the average of the maximum values ​​of the equivalent circle diameter of the opening to the thickness of the second layer is 0.3 or more and 5.0 or less. Attached Figure Description

[0008] [ Figure 1 ] Figure 1This is a three-dimensional view of composite material 10.

[0009] [ Figure 2 ] Figure 2 This is a cross-sectional view of composite material 10.

[0010] [ Figure 3 ] Figure 3 This is a top view of molybdenum plate 13.

[0011] [ Figure 4A ] Figure 4A The first explanatory diagram shows the steps for preparing a sample for measuring the thermal conductivity of composite material 10 in the thickness direction.

[0012] [ Figure 4B ] Figure 4B The second explanatory diagram shows the steps for preparing a sample for measuring the thermal conductivity of composite material 10 in the thickness direction.

[0013] [ Figure 4C ] Figure 4C The third explanatory diagram shows the steps for preparing a sample for measuring the thermal conductivity of composite material 10 in the thickness direction.

[0014] [ Figure 5 ] Figure 5 This is an explanatory diagram illustrating the evaluation method for the heat dissipation performance of composite material 10.

[0015] [ Figure 6 ] Figure 6 This is a cross-sectional view of the composite material 10 involved in the first modified example.

[0016] [ Figure 7 ] Figure 7 This is a cross-sectional view of the composite material 10 involved in the second variation.

[0017] [ Figure 8 ] Figure 8 This is a process diagram illustrating the manufacturing method of composite material 10.

[0018] [ Figure 9 ] Figure 9 This is an exploded perspective view of semiconductor package 100. Detailed Implementation

[0019] [The issues this disclosure aims to address]

[0020] The heat dissipation substrate described in Patent Document 1 has room for improvement in balancing a low coefficient of linear expansion and high heat dissipation.

[0021] This disclosure was made in view of the problems of the prior art as described above. More specifically, this disclosure provides a composite material that can balance a low coefficient of linear expansion and high heat dissipation.

[0022] [The effect of this disclosure]

[0023] The composite material according to this disclosure can achieve both a low coefficient of linear expansion and high heat dissipation.

[0024] [Description of the implementation of this disclosure]

[0025] First, the implementation methods of this disclosure are listed and described.

[0026] (1) One embodiment of the composite material is plate-shaped, having a first surface and a second surface opposite to the first surface. The composite material has multiple first layers and multiple second layers. The total number of first layers and second layers is 5 or more. The first and second layers are alternately stacked along the thickness direction of the composite material with the first layer located on the first and second surfaces. The first layer is formed of a metallic material with copper as the main component. The second layer has a molybdenum plate and copper filler. The molybdenum plate includes end faces in the thickness direction, namely the first and second surfaces, and multiple openings penetrating the molybdenum plate from the first surface toward 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 less than 30% 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 less than 35% of the thickness of the composite material. The number of openings is 1 mm per 1 mm of the first surface. 2 The area is 2 or more and 12 or less. The ratio of the average of the maximum values ​​of the equivalent circle diameter of the opening to the thickness of the second layer is 0.3 or more and 5.0 or less.

[0027] According to the composite material involved in (1), it is possible to achieve both a low coefficient of linear expansion and high heat dissipation.

[0028] (2) In the composite material of (1), the ratio of the average value of the maximum value of the equivalent circle diameter of the opening to the thickness of the second layer can be greater than 1.6 and less than 5.0.

[0029] (3) In the composite material of (1) or (2), the thermal conductivity in the thickness direction can be above 290 W / m·K at room temperature. The coefficient of linear expansion in the intralayer direction orthogonal to the thickness direction can be below 9.0 ppm / K when the temperature changes from room temperature to 800 °C.

[0030] (4) In the composite material of (3), the end temperature difference can be below 50°C.

[0031] (5) In the composite material of (1) or (2), the thermal conductivity in the thickness direction can be above 300 W / m·K at room temperature. The coefficient of linear expansion in the intralayer direction orthogonal to the thickness direction can be below 8.5 ppm / K when the temperature changes from room temperature to 800 °C.

[0032] (6) In the composite material of (5), the end temperature difference can be below 40°C.

[0033] (7) In the composite material of (1) to (6), the average value of the equivalent circle diameter of the opening on the first side and the average value of the equivalent circle diameter of the opening on the second side can be more than 0.05 mm and less than 0.35 mm.

[0034] (8) In the composite material of (1) to (7), the average value of the minimum opening area of ​​the opening can be more than 57% and less than 100% of the average value of the maximum opening area of ​​the opening.

[0035] (9) In the composite materials of (1) to (8), the total number of the first layer and the number of the second layer can be 9 or less.

[0036] (10) A heat sink according to one embodiment has the composite material of (1) to (9). The first surface of the composite material becomes the contact surface with the heat source.

[0037] (11) A semiconductor package according to one embodiment has the composite material of (1) to (9) and a semiconductor element disposed on a first surface of the composite material.

[0038] (12) The semiconductor package of (11) may further have a housing member formed of ceramic material. The housing member is disposed on the first surface in a manner that surrounds the semiconductor element.

[0039] [Details of the implementation of this disclosure]

[0040] Next, the detailed description of embodiments of the present disclosure will be given with reference to the accompanying drawings. In the following drawings, the same or equivalent parts will be labeled with the same reference numerals, and the description will not be repeated.

[0041] (The composition of the composite material involved in the implementation)

[0042] The composition of the composite material (hereinafter referred to as "composite material 10") involved in the embodiments will be described below.

[0043] Figure 1 This is a three-dimensional view of composite material 10. (See image below.) Figure 1 As shown, 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 faces of the composite material 10 in the thickness direction. That is, the second surface 10b is the opposite surface of the first surface 10a in the thickness direction of the composite material 10.

[0044] Figure 2 This is a cross-sectional view of composite material 10. (See diagram below.) Figure 2 As shown, the composite material 10 has multiple first layers 11 and multiple second layers 12. Figure 2 In the example shown, the number of 11 in the first layer is 4, the number of 12 in the second layer is 3, and the total number of 11 in the first layer and 12 in the second layer is 7.

[0045] The first layer 11 and the second layer 12 are alternately stacked along the thickness direction of the composite material 10, with one of the first layers 11 located on the first surface 10a and the other of the first layers 11 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 defined as thickness T1.

[0046] The first layer 11 is formed of a metallic material with copper as its main component. Here, "metallic material with copper as its main component" refers to a metallic material with a copper content of 50% by mass or more. Preferably, the metallic material with copper as its main component is a copper alloy containing 70% by mass or more of copper. The first layer 11 is formed, for example, of pure copper. It should be noted that pure copper is a metallic material composed of copper and unavoidable impurities constituting the balance.

[0047] The layer located on the first surface 10a in the first layer 11 is designated as the first layer 11a. The layer located on the second surface 10b in the first layer 11 is designated as the first layer 11b. The thickness of the first layer 11 is designated as the thickness T2. The thickness T2 of the first layer 11a (first layer 11b) is 0.025 mm or more and less than 30% of the thickness T1.

[0048] The second layer 12 has a molybdenum plate 13 and a copper filler 14. The molybdenum plate 13 is formed of a metallic material with molybdenum as its main component. "Metallic material with molybdenum as its main component" means a metallic material with a molybdenum content of 50% by mass or more. Preferably, the metallic material with molybdenum as its main component contains 70% by mass or more of molybdenum. The molybdenum plate 13 is, for example, formed of pure molybdenum. Pure molybdenum is a metallic material consisting of molybdenum and unavoidable impurities constituting the balance. The copper filler 14 is formed of a metallic material with copper as its main component. For example, the copper filler 14 is formed of pure copper. Preferably, the copper filler 14 is formed of the same material as the first layer 11.

[0049] The molybdenum plate 13 is plate-shaped. 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 faces 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.

[0050] The molybdenum plate 13 has a plurality of openings 13c. The openings 13c penetrate the molybdenum plate 13 along a direction from the first surface 13a toward the second surface 13b. Each 1 mm of the first surface 10a (second surface 10b)... 2 The number of openings 13c (the value obtained by dividing the total number of openings 13c by the area of ​​the first surface 10a (second surface 10b)) is 2 or more and 12 or less. Copper filler 14 is disposed inside the openings 13c.

[0051] The layer in the second layer 12 that contacts the first layer 11a is designated as the second layer 12a. The layer in the second layer 12 that contacts the first layer 11b is designated as the second layer 12b. The thickness of the second layer 12 is designated as thickness T3. The thickness T3 of the second layer 12a (second layer 12b) is 0.05 mm or more and less than 35% of the thickness T1.

[0052] Figure 3 This is a top view of molybdenum plate 13. (As shown) Figure 3 As shown, the opening 13c has a circular shape when viewed from above. However, the shape of the opening 13c when viewed from above is not limited to a circular shape. The opening 13c can be, for example, an ellipse, a polygon, or any other shape when viewed from above. The equivalent circular diameter of the opening 13c when viewed from above is defined as the opening diameter D. The opening diameter D is obtained by calculating the square root of the value obtained by dividing the area of ​​the opening 13c when viewed from above by π / 4.

[0053] The opening diameter D can be constant between the first surface 13a and the second surface 13b. The opening diameter D can also vary between the first surface 13a and the second surface 13b, or it can be non-constant between the first surface 13a and the second surface 13b. When the opening diameter D varies between the first surface 13a and the second surface 13b, the opening diameter D can decrease as it moves from one of the first surface 13a and the second surface 13b towards the other. In a given opening, the maximum value of the opening diameter D in the thickness direction is defined as the opening diameter D. max .

[0054] The opening diameter D max The average value (calculate the opening diameter D of all openings 13c) max The total value of the average equivalent circle diameter (the value obtained by dividing the total value by the total number of openings 13c) is defined as the average equivalent circle diameter. For a second layer 12, the value obtained by dividing the average equivalent circle diameter by the thickness T3, i.e., the ratio of the average equivalent circle diameter to the thickness T3, is 0.3 or more and 5.0 or less. The ratio of the average equivalent circle diameter to the thickness T3 is preferably 1.6 or more and less than 5.0.

[0055] The average value of the opening diameter D of the first surface 13a (the value obtained by calculating the total value of the opening diameter D of all openings 13c of the first surface 13a and dividing the total value by the total number of openings 13c) and the average value of the opening diameter D of the second surface 13b (the value obtained by calculating the total value of the opening diameter D of all openings 13c of the second surface 13b and dividing the total value by the total number of openings 13c) are preferably 0.05 mm or more and 0.35 mm or less, respectively.

[0056] The opening area of ​​opening 13c is measured on a plane parallel to the first surface 13a. The minimum opening area of ​​opening 13c, measured along the thickness direction of molybdenum plate 13 between the first surface 13a and the second surface 13b, is taken as the minimum opening area of ​​opening 13c. The maximum opening area of ​​opening 13c, measured along the thickness direction of molybdenum plate 13 between the first surface 13a and the second surface 13b, is taken as the maximum opening area of ​​opening 13c. The average value of the minimum opening areas of opening 13c (the sum of the minimum opening areas of all openings 13c and divided by the total number of openings 13c) is further preferably 57% to 100% of the average value of the maximum opening areas of opening 13c (the sum of the maximum opening areas of all openings 13c and divided by the total number of openings 13c).

[0057] The thermal conductivity in the thickness direction of the composite material 10 is preferably 290 W / m·K or higher at room temperature. The thermal conductivity in the thickness direction of the composite material 10 is preferably 300 W / m·K or higher at room temperature. It should be noted that "room temperature" refers to 27°C.

[0058] The thermal conductivity in the thickness direction of composite material 10 was determined using the laser flash method. In the laser flash method, the thermal diffusivity of composite material 10 was measured using an LFA457 MicroFlash (manufactured by NETZSCH), and the thermal conductivity in the thickness direction of composite material 10 was calculated based on this thermal diffusivity and the volume ratio and specific heat of each constituent material. In calculating the thermal conductivity, the specific heat of each constituent material was determined based on the *Handbook of Metal Data, 4th Edition* (2004, Maruzen Publishing), edited by the Japan Society for Metals. Furthermore, before measuring the thermal conductivity of composite material 10, the thermal conductivity of a pure copper sample of the same shape was measured under the same conditions, and the results were used as a reference for correction of the measurement results.

[0059] Figure 4A The first explanatory diagram shows the sample preparation steps for determining the thickness-direction thermal conductivity of composite material 10. (See diagram for reference.) Figure 4AAs shown, a thin slice 15 is cut from the composite material 10, which is the object of measurement. The thickness, length, and width of the thin slice 15 are t (mm), B (mm), and C (mm), respectively.

[0060] Let X be the decimal part of the value obtained by dividing 2 by t and rounding down. Let Y1 be the decimal part of the value obtained by dividing 10 by B and rounding down. Let Y2 be the decimal part of the value obtained by dividing 10 by C and rounding down. Cut out a number of thin slices 15 equal to the product of X, Y1 and Y2 from the composite material 10, which is the object of measurement.

[0061] Figure 4B The second explanatory diagram shows the sample preparation steps for determining the thickness-direction thermal conductivity of composite material 10. (See diagram for reference.) Figure 4B As shown, block 16 is fabricated from X sheets 15. The thickness, length, and width of block 16 are approximately 2 mm, B mm, and C mm, respectively. In the fabrication of block 16, firstly, X sheets 15 are stacked. At this time, amorphous powder formed from pure silver with an average particle size of 4 μm is placed between adjacent sheets 15. The amount of amorphous powder placed between adjacent sheets 15 is approximately [amount missing] mm. 2 0.2g±30%.

[0062] In the fabrication of block 16, secondly, a rectangular mold (not shown) with an opening having internal dimensions of B (mm) × C (mm) is prepared, and stacked sheets 15 are arranged within this opening. The mold is made of graphite. Thirdly, the stacked sheets 15 are heat-treated under an applied load P. The load P is 4.9 N or more and 9.8 N or less. The heat treatment is performed in an inert gas atmosphere. The heat treatment is performed at a holding temperature of 900°C for a holding time of 10 minutes. Through heat treatment, the amorphous powder softens and deforms, and adjacent sheets 15 are glued together, thereby fabricating block 16.

[0063] Figure 4C The third explanatory diagram shows the sample preparation steps for determining the thickness-direction thermal conductivity of composite material 10. (See diagram for reference.) Figure 4C As shown, a test specimen 17 with a height of approximately 10 mm, a width of approximately 10 mm, and a thickness of approximately 2 mm is prepared by arranging Y1 blocks 16 longitudinally and Y2 blocks 16 laterally. When Y1 blocks 16 are arranged longitudinally and Y2 blocks 16 are arranged laterally, adjacent blocks 16 are glued together by adhesive components. As adhesive components, components capable of withstanding temperatures up to approximately 800°C, such as silver solder foil or ceramic adhesive, can be used. The blocks 16 arranged longitudinally (Y1 blocks) and Y2 arranged laterally (Y2 blocks) can be fixed by winding stainless steel wire or similar material around their outer periphery.

[0064] When the temperature changes from room temperature to 800°C, the coefficient of linear expansion in the intralayer direction (orthogonal to the thickness direction) of the composite material 10 is preferably 9.0 ppm / K or less. More preferably, the coefficient of linear expansion in the intralayer direction of the composite material 10 is 8.5 ppm / K or less when the temperature changes from room temperature to 800°C.

[0065] The coefficient of linear expansion in the intralaminar direction of composite material 10 was calculated by measuring the expansion displacement in the intralaminar direction of composite material 10 within the temperature range of room temperature to 800°C using a TDS5000SA (manufactured by Bruker AXS). When calculating the coefficient of linear expansion in the intralaminar direction of composite material 10 with a planar shape of 3 mm × 15 mm, the planar shape of composite material 10 was used. The measured value was the average of three samples.

[0066] The end temperature difference of the composite material 10 is preferably below 50°C. More preferably, the end temperature difference of the composite material 10 is below 40°C. Figure 5 This diagram illustrates the evaluation method for the heat dissipation performance of composite material 10. Figure 5 The diagram schematically illustrates the state of the composite material 10 as viewed from one side. When viewed from a direction perpendicular to the first surface 10a, the composite material 10 is cut into a rectangular shape with dimensions of 10 mm in both length and width. The heating element 70 is in contact with the center of the cut first surface 10a of the composite material 10. When viewed from a direction perpendicular to the first surface 10a, the heating element 70 is a rectangular shape with dimensions of 10 mm in both length and width. The heating element 70 has a heat output of 50 W.

[0067] The aluminum fin 80 is bonded to the second surface 10b of the cut composite material 10 using silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., G-751). This bonding is performed by applying a load of 9.8 N with the silicone oil disposed between the second surface 10b of the cut composite material 10 and the aluminum fin 80.

[0068] The temperature at the interface between the first surface 10a of the cut composite material 10 and the heating element 70 is defined as the first temperature. The temperature at the end (corner) of the first surface 10a of the cut composite material 10 is defined 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 defined as the third temperature. The first, second, and third temperatures are measured using thermocouples (not shown). The air cooling of the aluminum fin 80 is controlled to set the third temperature to 25°C ± 3°C. The ambient temperature, which serves as the measurement environment, is set to 25°C ± 5°C.

[0069] The heating element 70 is brought into contact with the first surface 10a of the cut composite material 10. After more than 30 seconds, the temperature difference between the first temperature and the second temperature when the temperature reaches a steady state (first temperature - second temperature) is taken as the end temperature difference of the composite material 10. This end temperature difference is measured 10 times, and the average value is used. That is, the end temperature difference of the composite material 10 is the temperature difference between the portion of the first surface 10a in contact with the heating element 70 and the end (corner) of the first surface 10a when the heating element 70 is in contact with the first surface 10a and the aluminum fins 80 are bonded to the second surface 10b. The smaller the end temperature difference, the better the heat conduction in the intralayer direction of the composite material 10.

[0070] <Variation Example>

[0071] Figure 6 This is a cross-sectional view of the composite material 10 involved in the first modified example. Figure 7 This is a cross-sectional view of the composite material 10 involved in the second variation. (See figure) Figure 6 As shown, the total number of items in the first layer (11) and the second layer (12) can be 5. Figure 7 As shown, the total number of 11 in the first layer and the number of 12 in the second layer can be 9.

[0072] (Method for manufacturing composite materials according to the embodiments)

[0073] The manufacturing method of composite material 10 will be described below.

[0074] Figure 8 This is a process diagram illustrating the manufacturing method of composite material 10. (Example) Figure 8 As shown, the manufacturing method of composite material 10 includes a preparation step S1, an opening step S2, and a joining step S3.

[0075] In preparation step S1, a first plate and a second plate are prepared. The first plate is formed from a metallic material with copper as the main component. The second plate is formed from a metallic material with molybdenum as the main component.

[0076] In the drilling process S2, a hole is drilled into the second plate. This drilling process creates multiple openings in the second plate that extend through its thickness. As a result, the second plate becomes a molybdenum plate 13. The drilling of the second plate can be performed, for example, by etching or laser irradiation.

[0077] In the joining process S3, the first sheet and the molybdenum plate 13 are alternately stacked in a mold (hereinafter, the structure obtained by alternately stacking the first sheet and the molybdenum plate 13 is referred to as a laminate). The mold is, for example, formed of graphite. The stacking of the first sheet and the molybdenum plate 13 is carried out in such a way that the first sheet is located on the surface of the laminate.

[0078] In the joining process S3, secondly, the laminate is heated and pressurized. The heating temperature is below the melting point of the first sheet material and at which the first sheet material is sufficiently softened. The heating temperature is, for example, 1000°C. Pressurization is performed along the thickness direction of the laminate. Pressurization is performed at the pressure required to allow the first sheet material, softened by heating, to flow. Pressurization is performed, for example, at a pressure of 50 MPa.

[0079] The heating and pressurization result in the first plate being filled into the opening 13c of the molybdenum plate 13, thus becoming copper filler 14. The remaining portion of the first plate not filled into the opening 13c becomes the first layer 11.

[0080] (The configuration of the semiconductor package involved in the implementation)

[0081] The following describes the configuration of the semiconductor package (hereinafter referred to as "semiconductor package 100") according to the embodiments.

[0082] Figure 9 This is an exploded perspective view of semiconductor package 100. (See image below.) Figure 9 As shown, the semiconductor package 100 includes a composite material 10, a semiconductor element 20, a housing component 30, a cover 40, a terminal 50a, and a terminal 50b.

[0083] The composite material 10 functions as a heat sink in the semiconductor package 100. A semiconductor element 20 is disposed on a first surface 10a. A heat transfer member may be sandwiched between the semiconductor element 20 and the first surface 10a. The semiconductor element 20 becomes a heat source during operation.

[0084] The housing member 30 is formed, for example, of a ceramic material. The ceramic material is, for example, alumina (Al₂O₃). The housing member 30 is disposed on the first surface 10a in a manner that surrounds the semiconductor element 20. The lower end (the end on the side of the first surface 10a) of the housing member 30 is bonded to the first surface 10a, for example, by brazing. The cover 40 is formed, for example, of a ceramic or metallic material. The cover 40 closes the upper end of the housing member 30.

[0085] Terminals 50a and 50b are inserted into the housing member 30. As a result, one end of terminals 50a and 50b lies within the space defined by the first surface 10a, the housing member 30, and the cover 40, while the other end lies outside that space. Terminals 50a and 50b are formed, for example, of a metallic material. The metallic material is, for example, a Kovar iron-nickel-cobalt alloy.

[0086] Although not shown, one end of terminals 50a and 50b is electrically connected to semiconductor element 20. The other end of semiconductor package 100 is electrically connected to a device or circuit different from semiconductor package 100.

[0087] A heat dissipation member 60 is mounted on the second surface 10b. The heat dissipation member 60 is, for example, a metal plate with internal flow paths for the cooling medium. However, the heat dissipation member 60 is not limited to this. The heat dissipation member 60 can, for example, be a cooling fin. A heat transfer member may also be sandwiched between the heat dissipation member 60 and the second surface 10b.

[0088] (Effects of the composite materials involved in the implementation method)

[0089] The effects of composite material 10 will be explained below.

[0090] In order to efficiently release heat from the heat source from the first surface 10a (second surface 10b), it is effective to increase the thermal conductivity on the first surface 10a (second surface 10b) side so that the heat from the heat source diffuses along the in-layer direction.

[0091] In composite material 10, the thickness T2 of the first layer 11a (first layer 11b), which has relatively high thermal conductivity, is ensured to be above 0.025 mm. Therefore, according to composite material 10, heat from the heat source can be efficiently released from the first surface 10a (second surface 10b).

[0092] The composite material 10 is exposed to high temperatures (e.g., about 800°C) during the brazing of the housing component 30. Therefore, it is required that the composite material 10 exhibits low thermal expansion when exposed to high temperatures. 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 ensured to be 0.05 mm or more. Furthermore, in the composite material 10, by making the thickness T2 of the first layer 11a (first layer 11b) less than 30% of the thickness T1, the first layer 11a (first layer 11b), which has a relatively high coefficient of linear expansion, does not become excessively thick. Therefore, according to the composite material 10, thermal expansion when exposed to high temperatures is suppressed.

[0093] To improve the heat dissipation of the composite material 10, it is necessary not only to increase the thermal conductivity of the first surface 10a (second surface 10b) but also to increase the overall thermal conductivity of the composite material 10. However, if the proportion of molybdenum in the composite material 10 is increased, the overall coefficient of linear expansion of the composite material 10 decreases, and on the other hand, the overall thermal conductivity of the composite material 10 decreases.

[0094] Every 1 mm of the first surface 10a (second surface 10b) 2The more openings 13c there are, or the larger the value obtained by dividing the average equivalent circle diameter of the openings 13c by the thickness T3, the lower the proportion of molybdenum in the composite material 10, and the lower the overall thermal conductivity of the composite material 10. Furthermore, the greater the thickness T3 of the second layer 12a (second layer 12b), the higher the proportion of molybdenum in the composite material 10, and the lower the overall thermal conductivity of the composite material 10.

[0095] In composite material 10, the number of openings 13c is set to 1 mm per 1 mm on the first surface 10a (second surface 10b). 2 The area is 2 or more and 12 or less, and the value obtained by dividing the average equivalent circle diameter of the opening 13c by the thickness T3 is set to 0.3 or more and 5.0 or less. Furthermore, in the composite material 10, the thickness T3 of the second layer 12a (second layer 12b) is set to 35% or less 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 coefficient of linear expansion is maintained as a whole.

[0096] Therefore, according to composite material 10, both low coefficient of linear expansion and high heat dissipation can be achieved.

[0097] (Experimental Example)

[0098] To confirm the effectiveness of composite material 10, samples 1 to 48 were prepared. 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.

[0099] The dimensions of composite material 10 in samples 1 to 48 are shown in Tables 1, 2, and 3. The thickness T2, excluding the first layers 11a and 11b, is determined by the thickness T1 of composite material 10, the thickness T2 of the first layers 11a and 11b, and the thickness T3 of the second layer 12, and is therefore omitted from Tables 1 to 3. Furthermore, in samples 27 to 48, the thickness T3 of the second layers 12a and 12b is equal to the thickness T3 of the second layer 12 excluding the second layers 12a and 12b.

[0100] Condition A is defined as the thickness T1 of the first layer 11a (first layer 11b) being 0.025 mm or more and less than 30% of the thickness T3. Condition B is defined as the thickness T2 of the second layer 12a (second layer 12b) being 0.05 mm or more and less than 30% of the thickness T3.

[0101] Each 1 mm of the first surface 10a (second surface 10b) 2Condition C is that the number of openings 13c in the area is 2 or more and 12 or less. Condition D is that the value obtained by dividing the average equivalent circle 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 equivalent circle diameter of the openings 13c by the thickness T3 is 1.6 or more and less than 5.0.

[0102] In samples 1 through 3, 8, 12, 15, 27, 32, 39, and 43, at least one of conditions A through D was not satisfied. In all other samples, conditions A through D were satisfied.

[0103] In samples 4 to 7, 13, 14, 18 to 22, 28 to 31, 34, 36 to 38, 40 to 42, and 44 to 48, condition E is further satisfied.

[0104] [Table 1]

[0105]

[0106]

[0107]

[0108] The thermal conductivity in the thickness direction, the coefficient of linear expansion in the intralayer direction and the end temperature difference were measured for samples 1 to 48 as the temperature changed from room temperature to 800℃.

[0109] Tables 4, 5, and 6 show the results of the measurements of thermal conductivity in the thickness direction, coefficient of linear expansion in the intralayer direction, and end temperature difference for samples 1 to 48 as the temperature varied from room temperature to 800°C.

[0110] [Table 4]

[0111] Table 4

[0112]

[0113] [Table 5]

[0114] Table 5

[0115]

[0116] [Table 6]

[0117] Table 6

[0118]

[0119] Condition F is defined as a thermal conductivity of 290 W / m·K or higher in the thickness direction. Condition G is defined as a linear expansion coefficient of 9.0 ppm / K or lower in the intralayer direction when the temperature changes from room temperature to 800℃. Condition H is defined as an end temperature difference of 50℃ or lower.

[0120] In samples 1 to 3, 8, 12, 15, 27, 32, 39, and 43, at least one of conditions F to H was not satisfied. On the other hand, in all other samples, conditions F to H were satisfied. This comparison also experimentally demonstrates that by satisfying all conditions A to D, composite material 10 achieves a balance between a low coefficient of linear expansion and high heat dissipation.

[0121] Condition I is defined as a thermal conductivity in the thickness direction of 300 W / m·K or higher. Condition J is defined as a linear expansion coefficient in the intralayer direction of 8.5 ppm / K or lower when the temperature changes from room temperature to 800℃. Condition K is defined as an end temperature difference of 40℃ or lower.

[0122] In samples 4 to 7, 13, 14, 18 to 22, 28 to 31, 34, 36 to 38, 40 to 42, and 44 to 48, conditions I to K were further satisfied. This comparison also experimentally demonstrates that by further satisfying condition E, the low coefficient of linear expansion and high heat dissipation of composite material 10 are further balanced to a high level.

[0123] The embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the invention is shown by the claims rather than the foregoing embodiments and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0124] Symbol Explanation

[0125] 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 Sheet, 16 Block, 17 Test sample, 20 Semiconductor element, 30 Housing component, 40 Cover, 50a, 50b Terminals, 60 Heat dissipation component, 70 Heating element, 80 Aluminum fin, 100 Semiconductor package, D Opening diameter, S1 Preparation process, S2 Opening process, S3 Bonding process, T1, T2, T3 Thickness.

Claims

1. A composite material, said composite material being a plate-like composite material having a first surface and a second surface opposite to the first surface, wherein, The composite material has multiple first layers and multiple second layers. The total number of the first layer and the number of the second layer is 5 or more. The first layer and the second layer are alternately stacked along the thickness direction of the composite material. The layer that constitutes the first surface and the second surface is the first layer. The first layer is formed of a metallic material with copper as the main component. The second layer has a molybdenum plate and copper filler. The molybdenum plate has a plurality of openings extending through it in the thickness direction. The copper filler is configured to fill the interior of the opening. The thickness of the first layer constituting the first surface is 0.025 mm or more and less than 30% of the thickness of the composite material. The thickness of the second layer in contact with the first layer constituting the first surface is 0.05 mm or more and less than 30% of the thickness of the composite material. In any of the second layers, The number of openings is per 1 mm on the first surface 2 Areas between 2 and 12 The value obtained by dividing the average equivalent circle diameter of the opening by the thickness of the second layer is 0.3 or more and 5.0 or less.

2. The composite material as described in claim 1, wherein, The value obtained by dividing the average equivalent circle diameter of the opening by the thickness of the second layer is greater than or equal to 1.6 and less than 5.

0.

3. The composite material as described in claim 1 or claim 2, wherein, The thermal conductivity in the thickness direction is above 290 W / m·K at room temperature. The coefficient of linear expansion in the intralayer direction orthogonal to the thickness direction is less than 9.0 ppm / K when the temperature changes from room temperature to 800°C.

4. The composite material as described in claim 3, wherein, The end temperature difference of the composite material is below 50°C.

5. The composite material as described in claim 1 or claim 2, wherein, The thermal conductivity in the thickness direction is above 300 W / m·K at room temperature. The coefficient of linear expansion in the intralayer direction orthogonal to the thickness direction is less than 8.5 ppm / K when the temperature changes from room temperature to 800°C.

6. The composite material as described in claim 5, wherein, The end temperature difference of the composite material is below 40°C.

7. The composite material as described in claim 1 or claim 2, wherein, The molybdenum plate has end faces, namely a first face and a second face, in the thickness direction. The average value of the equivalent circle diameter of the opening on the first surface and the average value of the equivalent circle diameter of the opening on the second surface are 0.05 mm or more and 0.35 mm or less.

8. The composite material as described in claim 1 or claim 2, wherein, The average minimum opening area of ​​the opening is more than 57% and less than 100% of the average maximum opening area of ​​the opening.

9. The composite material as claimed in claim 1 or claim 2, wherein, The total number of the first layer and the number of the second layer is 9 or less.

10. A radiator comprising the composite material described in any one of claims 1 to 9, The first surface becomes the contact surface with the heat source.

11. A semiconductor package comprising: the composite material as described in any one of claims 1 to 9 and a semiconductor element disposed on the first surface.

12. The semiconductor package of claim 11, wherein, The semiconductor package also has a housing component formed of a ceramic material. The housing component is configured on the first surface in a manner that surrounds the semiconductor element.

13. The composite material as described in claim 1 or 2, wherein, The thermal conductivity in the thickness direction is above 290 W / m·K at room temperature. When the temperature changes from room temperature to 800°C, the coefficient of linear expansion in the intralayer direction orthogonal to the thickness direction is below 9.0 ppm / K. The molybdenum plate has end faces, namely a first face and a second face, in the thickness direction. The average value of the equivalent circle diameter of the opening on the first surface and the average value of the equivalent circle diameter of the opening on the second surface are both 0.05 mm and 0.35 mm. The average minimum opening area of ​​the opening is more than 57% and less than 100% of the average maximum opening area of ​​the opening.

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