Heat dissipation plate

Abstract

A heat sink that does not require brazing to a substrate made of Al, Cu or an alloy thereof and has excellent heat dissipation properties is provided. [Solution] The above problem was solved by providing a heat sink in which at least IMC layers 304, 306 and a base layer 302 containing Cu or Al are laminated in the plate thickness direction, and the IMC layers 304, 306 are present in a matrix containing Sn and an Sn-Cu alloy, with intermetallic compound crystals containing Sn, Cu, and Bi being enclosed within the matrix.

Description

[Technical Field]

[0001] The present invention relates to a heat sink. [Background technology]

[0002] FIG. 1 is a schematic cross-sectional view for explaining a typical semiconductor device. The semiconductor device 101 includes a semiconductor element 22, bonding pads 211 provided on the semiconductor element 22, a plurality of lead terminals 50 arranged around the semiconductor element 22, a plurality of bonding wires 26 electrically connecting the semiconductor element 22 and the lead terminals 50, and a sealing resin 21 that seals these components. The planar size of the semiconductor device 101 is, for example, about 4 mm, and the thickness is, for example, 1 mm or less.

[0003] Furthermore, a heat sink 40 is generally used to efficiently dissipate heat generated from the semiconductor device 101. Since the heat sink 40 is required to have high thermal conductivity for its function, Al, Cu, or an alloy thereof has been used as the base material. The heat sink 40 is joined (reference numeral 23) to the semiconductor element 22, a circuit board, a metal package member (not shown), or the like by soldering or brazing. Conventional techniques for heat sinks are disclosed in, for example, Patent Document 1. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6233677 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional substrates made of Al, Cu or alloys thereof require brazing under heating conditions exceeding 1000°C, for example, in order to be used as heat sinks in semiconductor devices, which increases the manufacturing cost.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a heat sink that does not require brazing to a substrate made of Al, Cu or an alloy thereof and that has excellent heat dissipation properties. [Means for solving the problem]

[0007] The present invention provides a heat sink comprising at least an IMC layer and a substrate layer containing Cu or Al laminated in the plate thickness direction, wherein the IMC layer contains intermetallic compound crystals containing Sn, Cu, and Bi present in a matrix phase containing Sn and an Sn-Cu alloy. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a heat sink that does not require brazing to a substrate made of Al, Cu or an alloy thereof and has excellent heat dissipation properties. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view for explaining a general semiconductor device. [Figure 2] FIG. 2 is a cross-sectional view of a heat sink according to an embodiment of the present invention. [Figure 3] FIG. 2 is a diagram illustrating an example of a manufacturing apparatus suitable for manufacturing metal particles of the present invention. [Figure 4A] 1 is a STEM image of a cross section of a thinly cut metal particle 1 obtained in Example 1. [Figure 4B] FIG. 2 is a diagram showing the results of element mapping analysis by EDS of a thinly cut cross section of metal particle 1 obtained in Example 1. [Figure 5A] 1 is a STEM image of a cross section obtained by thinly cutting the sheet 1 obtained in Example 1. [Figure 5B] FIG. 2 is a diagram showing the results of elemental mapping analysis by EDS of a cross section obtained by thinly cutting the sheet 1 obtained in Example 1. [Figure 6]FIG. 2 is a diagram showing the cross-sectional shapes of the heat sinks (base layer made of Cu) of the present invention obtained in Examples 1 to 3. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in more detail below. First, the terminology used in this specification is as follows unless otherwise specified. (1) When we say metal, it can include not only a single metallic element but also an alloy or intermetallic compound containing multiple metallic elements. (2) When referring to a single metal element, it does not mean only a substance consisting of the metal element in its entirety, but also includes cases in which trace amounts of other substances are contained. In other words, it does not exclude substances containing trace amounts of impurities that have little effect on the properties of the metal element. For example, the term "parent phase" does not exclude a substance in which some atoms in Sn crystals are replaced by other elements (e.g., Cu). For example, the other substances or other elements may be contained in the metal particles in an amount of 0 to 0.1 mass %.

[0011] Figure 2 is a cross-sectional view of a heat sink according to one embodiment of the present invention. In Figure 2(a), heat sink 31 of the present invention is formed by laminating at least an IMC layer 304 and a base layer 302 containing Cu or Al. In Figure 2(b), heat sink 32 of the present invention is formed by laminating at least an IMC layer 304, a base layer 302 containing Cu or Al, and an IMC layer 306. The thickness of the base layer 302 is, for example, 100 μm to 300 μm, and the thickness of the IMC layers 304 and 306 is 50 μm or less, preferably 25 μm to 30 μm.

[0012] The IMC layer is a layer in which intermetallic compound crystals containing Sn, Cu, and Bi are contained in a matrix phase containing Sn and an Sn-Cu alloy, and can be produced from the following metal particles (hereinafter sometimes referred to as the metal particles of the present invention).

[0013] The metal particles of the present invention have the same structure as the IMC layer; in other words, the IMC layer produced from the metal particles of the present invention has the same structure as the metal particles of the present invention.

[0014] The composition of the metal particles of the present invention is Cu 3~20% by mass, Bi 5~40% by mass, the balance being Sn (provided that, if unavoidable impurities are present, the unavoidable impurities are 0.1 mass% or less); The composition of the parent phase is Sn 40~96% by mass, Cu 0.05~8% by mass, Bi 0.7~57% by mass (However, if unavoidable impurities are present, the amount of the unavoidable impurities is 0.1% by mass or less.) The composition of the intermetallic compound crystal is Cu 1~30% by mass, Bi 0.05~30% by mass, The balance is Sn (however, if unavoidable impurities are present, the amount of the unavoidable impurities is 0.1 mass % or less). The proportion of intermetallic compound crystals in the metal particles of the present invention is, for example, 20 to 60 mass %, and preferably 30 to 40 mass %, based on the total mass of the metal particles. The intermetallic compound crystals are present in a state of being contained in the matrix.

[0015] The metal particles of the present invention can be produced from raw materials having a composition of, for example, 3 to 20 mass % Cu, 5 to 20 mass % Bi, and the remainder Sn by, for example, melting the raw materials, feeding them onto a dish-shaped disk rotating at high speed in a nitrogen gas atmosphere, scattering the molten metal as small droplets by centrifugal force, and cooling and solidifying them under reduced pressure.

[0016] An example of a manufacturing apparatus suitable for producing metal particles of the present invention will be described with reference to FIG. 3. The granulation chamber 1 has a cylindrical upper portion and a conical lower portion, and is fitted with a lid 2 on top. A nozzle 3 is inserted vertically into the center of the lid 2, and a dish-shaped rotating disk 4 is provided directly below the nozzle 3. Reference numeral 5 denotes a mechanism for supporting the dish-shaped rotating disk 4 so that it can move up and down. A discharge pipe 6 for the produced particles is connected to the lower end of the conical portion of the granulation chamber 1. The top of the nozzle 3 is connected to an electric furnace 7 (high-frequency furnace: conventionally, a ceramic crucible was used, but in this invention, a carbon crucible is used) for melting the metal to be granulated. Ambient gas adjusted to a predetermined composition in a mixed gas tank 8 is supplied to the interior of the granulation chamber 1 and the top of the electric furnace 7 via pipes 9 and 10, respectively. The pressure within the granulation chamber 1 is controlled by a valve 11 and an exhaust device 12, and the pressure within the electric furnace 7 is controlled by a valve 13 and an exhaust device 14, respectively. Molten metal fed from nozzle 3 onto dish-shaped rotating disk 4 is broken into fine droplets by the centrifugal force of dish-shaped rotating disk 4, which are then cooled under reduced pressure and turn into solid particles. The solid particles thus produced are fed from discharge pipe 6 to automatic filter 15 where they are separated. Reference numeral 16 denotes a fine particle recovery device.

[0017] The process of cooling and solidifying the molten metal from a high-temperature melt is important for forming the metal particles of the present invention. For example, the following conditions can be mentioned: The melting temperature of the metal in the melting furnace 7 is set to 600° C. to 800° C., and while maintaining this temperature, the molten metal is supplied from the nozzle 3 onto the dish-shaped rotating disk 4 . The dish-shaped rotating disk 4 has an inner diameter of 35 mm and a rotor thickness of 5 mm, and rotates at 80,000 to 100,000 revolutions per minute. Granulation chamber 1: 9 x 10 -2 After the pressure was reduced using a vacuum chamber capable of reducing the pressure to about 1×10 Pa, nitrogen gas at 15 to 50°C was supplied while simultaneously evacuating the gas. -1 Pa or less.

[0018] Fig. 4A is a STEM image of a cross section of a thinly cut metal particle 1 of the present invention obtained in Example 1 below. Referring to the metal particle in Fig. 4A, the metal particle has an intermetallic compound crystal (light colored portion) containing Sn, Cu, and Bi in a matrix phase (light colored portion) containing Sn and an Sn-Cu alloy. The particle diameter of the metal particle of the present invention is preferably in the range of 1 µm to 50 µm, for example.

[0019] The composition and ratio of the matrix and intermetallic compounds can be satisfied by complying with the manufacturing conditions of the metal particles.

[0020] The metal particles of the present invention are then formed into a sheet and bonded to a substrate layer containing Cu or Al, thereby obtaining the heat sink of the present invention. The metal particles of the present invention can be formed into a sheet by, for example, directly inserting the metal particles of the present invention into a rolling rotary roll heated to 100°C to 190°C and processing it, and multiple sheets of this can be stacked as needed.

[0021] Examples of the substrate layer containing Cu or Al include Cu alone, Al alone, Cu alloys (such as brass and phosphor bronze alloys), and Al alloys (such as Ni / Al alloys).

[0022] The IMC layer and the substrate layer can be bonded together by, for example, hot rolling under the following conditions. IMC layer thickness: 30μm~70μm Base layer thickness: 120μm~300μm Roll temperature: 150℃~100℃ Rolling pressure: about 500N Rolling speed: about 2 mm / sec Another method is to place a base material layer at the center, place IMC layers on both sides of the base material layer, and press-roll the layers together using a press-rolling machine.

[0023] The heat sink of the present invention can be used as a heat sink for a semiconductor device such as that shown in FIG. 1, and can be directly bonded to a semiconductor element without going through a process such as brazing or soldering. Examples of semiconductor elements include Si, GaN, and SiC. The heat sink of the present invention can be bonded to a semiconductor element by, for example, heat and pressure bonding, ultrasonic bonding, etc. Heat and pressure bonding can be performed by overlapping the heat sink of the present invention and the semiconductor element in an inert gas atmosphere such as nitrogen, applying a load of about 0.2 to 0.35 MPa, and heat and pressure bonding at a temperature of about 170 to 185°C for 1 to 3 minutes. As an example of ultrasonic bonding, the heat sink of the present invention and a semiconductor element are superimposed on each other and ultrasonically bonded under the following conditions. Load: 600N~1000N Amplitude: 60%~70% Time: 500ms to 1000ms [Example]

[0024] The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0025] Example 1 Using raw materials having a composition of 7.2 mass % Cu, 10 mass % Bi, and the remainder Sn, metal particles 1 having a diameter of approximately 3 to 20 μm were produced by the production apparatus shown in FIG. In this case, the following conditions were adopted: A melting crucible was placed in a melting furnace 7, and the raw materials were placed therein and melted at 650°C. While maintaining this temperature, the molten metal was supplied from the nozzle 3 onto the dish-shaped rotating disk 4. The dish-shaped rotating disk 4 used was a dish-shaped disk with a diameter of 35 mm and a rotating disk thickness of 3 to 5 mm, and was rotated at 80,000 to 100,000 revolutions per minute. Granulation chamber 1: 9 x 10 -2 After the pressure was reduced using a vacuum chamber capable of reducing the pressure to about 1×10 Pa, nitrogen gas at 15 to 50°C was supplied while simultaneously evacuating the gas. -1 Pa or less.

[0026] The obtained metal particles 1 were directly inserted into a rolling mill roll heated to 120°C to produce sheet 1. The obtained metal particles 1 had a cross section as shown in Figure 4A, and contained intermetallic compound crystals containing Sn, Cu, and Bi (light-colored areas) in a matrix phase containing Sn and an Sn-Cu alloy (light-colored areas). Figure 4B shows the results of elemental mapping analysis of metal particles 1. The obtained sheet 1 had a cross section as shown in FIG. 5A, and contained intermetallic compound crystals (dark colored parts) containing Sn, Cu, and Bi in a matrix phase (light colored parts) containing Sn and an Sn-Cu alloy. Furthermore, elemental mapping analysis of the surface of Sheet 1 by EDS (see Figure 5B) revealed that the composition of Sheet 1 was Cu 5.7~8.04% by mass, Bi 12.27~13.24% by mass, The remainder was found to be Sn. In addition, the composition of the parent phase is Sn 71~88% by mass, Cu 0.05~2.85% by mass, Bi 0.78~2.36% by mass It turned out to be. The composition of the intermetallic compound crystal is: Cu 1.49~20.11% by mass, Bi 2.36~18.54% by mass, The remainder was found to be Sn.

[0027] The intermetallic compound crystals in Sheet 1 accounted for 30 to 35 mass % of Sheet 1.

[0028] Next, sheet 1 and a substrate layer made of Cu or Al were bonded using a rolling roll at a heating temperature of 120°C and a rolling roll speed of 2 mm / sec to produce the heat sink of the present invention shown in Figure 2(b). The thickness of the IMC layers 304 and 306 made of the sheet 1 was 25 μm, and the thickness of the base material layer 302 was 200 μm. The structure of the IMC layer was confirmed by elemental mapping analysis using EDS, and was found to be the same as the structure of Sheet 1 described above. The obtained heat sink of Example 1 having a Cu substrate layer is referred to as heat sink 1, and the heat sink having an Al substrate layer is referred to as heat sink 2.

[0029] Next, the heat dissipation characteristics of the heat sinks 1 and 2 of the present invention in Example 1 were investigated. As a result, the thermal conductivity of the heat sinks 1 and 2 measured by the hot wire method was about 129.6 W / (m×K).

[0030] Example 2 Example 1 was repeated except that raw materials having a composition consisting of 6 mass % Cu, 20 mass % Bi, and the remainder Sn were used, to obtain a sheet 2 made of metal particles 2 of the present invention. The obtained sheet 2 has a cross section as shown in FIG. 4A. When elemental mapping analysis of the cross section of the sheet 2 was performed by EDS, the composition of the sheet 2 was Cu 4.8~5.4% by mass, Bi 19.36~21.13% by mass, The remainder was found to be Sn. In addition, the composition of the parent phase is Sn 39.97~68.32% by mass, Cu 0.05~7.85% by mass, Bi 21.18~56.01% by mass It turned out to be. The composition of the intermetallic compound crystal is: Cu 8.27~19.10% by mass, Bi 3.30~10.4% by mass, The remainder was found to be Sn. Subsequently, in the same manner as in Example 1, the sheet 2 was used to obtain a heat sink of the present invention. The structure of the IMC layer of Example 2 was confirmed by element mapping analysis using EDS, and was found to be the same as the structure of the metal particles 2 described above. The obtained heat sink having Cu as a base layer of Example 2 is referred to as heat sink 3, and the heat sink having Al as a base layer is referred to as heat sink 4. The heat dissipation characteristics of the heat sinks 3 and 4 of Example 2 were investigated. As a result, the thermal conductivity of the heat sinks 3 and 4 measured by the hot wire method was about 115.4 W / (m×K).

[0031] Example 3 Example 1 was repeated except that raw materials having a composition consisting of 5 mass % Cu, 40 mass % Bi, and the remainder Sn were used, to obtain a sheet 3 made of metal particles 3 of the present invention. The obtained sheet 3 has a cross section as shown in FIG. 4A. When elemental mapping analysis of the cross section of the sheet 3 was performed by EDS, the composition of the sheet 3 was Cu 3.19~3.43% by mass, Bi 38.64~40% by mass, The remainder was found to be Sn. In addition, the composition of the parent phase is Sn 41.63~53.44% by mass, Cu 0.05~4.68% by mass, Bi 36.83~50.34% by mass It turned out to be. The composition of the intermetallic compound crystal is: Cu 12.65~22.23% by mass, Bi 19.86~29.94% by mass, The remainder was found to be Sn. Subsequently, in the same manner as in Example 1, the sheet 3 was used to obtain a heat sink of the present invention. The structure of the IMC layer of Example 3 was confirmed by element mapping analysis using EDS, and was found to be the same as the structure of the metal particles 3 described above. The obtained heat sink having Cu as a base layer of Example 3 is referred to as heat sink 5, and the heat sink having Al as a base layer is referred to as heat sink 6. The heat dissipation characteristics of the heat sinks 5 and 6 of Example 3 were investigated. As a result, the thermal conductivity of the heat sinks 5 and 6 measured by the hot wire method was about 100.0 W / (m×K).

[0032] The cross-sectional shapes of the heat sinks (with Cu substrate layers) of the present invention obtained in Examples 1 to 3 are shown in FIG.

[0033] The present invention has been described in detail above with reference to the accompanying drawings, but the present invention is not limited to these, and it is obvious that a person skilled in the art can come up with various modifications based on the basic technical ideas and teachings thereof. [Explanation of symbols]

[0034] 1 Granulation chamber 2 lid 3 nozzles 4-plate rotating disc 5 Rotating disk support mechanism 6 Particle discharge pipe 7. Electric furnace 8 Mixed Gas Tank 9 Piping 10 Piping 11 Valve 12 Exhaust system 13 Valve 14 Exhaust system 15 Automatic Filter 16. Particle collection device 21 Sealing resin 22 Semiconductor elements 23 Brazing 26 Bonding Wire 40 Heat sink 50 Lead terminal 31 Heat sink 32 Heat sink 101 Semiconductor device 302 Base material layer 304 IMC layer 306 IMC layer

Claims

1. A heat sink plate in which at least an IMC layer and a base layer containing Cu or Al are laminated in the plate thickness direction, The IMC layer is present in such a manner that intermetallic compound crystals containing Sn, Cu, and Bi are contained in a matrix phase containing Sn and a Sn—Cu alloy, The composition of the IMC layer is Cu 3-20% by mass, Bi 5-40% by mass, The balance is Sn, The composition of the parent phase is Sn 40-96% by mass, Cu 0.05-8% by mass, Bi 0.7-57% by mass and The composition of the intermetallic compound crystal is Cu 1-30% by mass, Bi 0.05-30% by mass, The balance is Sn. Heat sink.

2. The heat sink according to claim 1 , wherein at least an IMC layer, a base layer containing Cu or Al, and an IMC layer are laminated in this order in the plate thickness direction.

3. A semiconductor device comprising the heat sink according to claim 1.

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