Heat dissipation member and semiconductor unit

Abstract

The present invention ensures a simple configuration and appropriate heat dissipation of a heat dissipation member. This heat dissipation member (10) contains silicon nitride as a main component, and includes a base part (20) and a protruding part (30) protruding from one surface (20B) of the base part (20). The thickness (t) of the base part (20) is 0.5-5.0 mm inclusive.

Description

Heat dissipation member and semiconductor unit

[0001] The present invention relates to a heat dissipation member and a semiconductor unit.

[0002] In recent years, growing awareness of carbon neutrality and societal demands have accelerated the movement toward widespread adoption of electric vehicles. The widespread adoption of electric vehicles requires solving technical issues such as improving driving range and shortening charging times, and the role played by power semiconductors is becoming increasingly important. Patent Document 1 discloses a silicon nitride circuit board that has a thin substrate thickness, improved heat dissipation, and ensures insulation and high reliability. Patent Document 2 proposes a semiconductor device with a ceramic heat sink member that alleviates thermal stress and pressure on the heat sink member.

[0003] International Publication No. 2020 / 044974 Japanese Patent Application Laid-Open No. 2008-270295

[0004] However, even when a silicon nitride circuit board is used as in Patent Document 1 or a ceramic heat sink member is used as in Patent Document 2, there is room for improvement in terms of ensuring appropriate heat dissipation. Furthermore, there is a demand for a heat dissipation member that can ensure appropriate heat dissipation and has a simple configuration, and is not limited to applications such as power semiconductors.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a heat dissipation member and a semiconductor unit that can simplify the configuration of the heat dissipation member and ensure appropriate heat dissipation performance.

[0006] The heat dissipation member of the present disclosure is a heat dissipation member whose main component is silicon nitride, and includes a base portion and a protrusion protruding from one surface of the base portion, and the thickness of the base portion is 0.5 mm or more and 5.0 mm or less.

[0007] The heat dissipation member of the present disclosure is a heat dissipation member whose main component is silicon nitride, and includes a base portion and a protrusion portion protruding from one surface of the base portion, wherein the diameter Dr of the circumscribing circle of the outer periphery of the base end portion on the base portion side is larger than the diameter Dt of the circumscribing circle of the outer periphery of the tip portion on the opposite side from the base portion.

[0008] The semiconductor unit according to the present disclosure includes the heat dissipation member and a semiconductor chip provided on the other surface side.

[0009] According to the present invention, the configuration of the heat dissipation member can be simplified and heat dissipation performance can be appropriately ensured.

[0010] Fig. 1 is a schematic cross-sectional view of a semiconductor unit according to this embodiment. Fig. 2 is a schematic cross-sectional view of a heat dissipation member. Fig. 3 is a schematic view of the heat dissipation member as viewed from the Z direction side. Fig. 4 is a schematic view illustrating another example of the heat dissipation member. Fig. 5 is a flowchart illustrating an example of a method for manufacturing a heat dissipation member according to this embodiment.

[0011] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments, and when there are multiple embodiments, the present invention also includes configurations that are made by combining the respective embodiments. Furthermore, numerical values ​​include the range of rounding.

[0012] (Semiconductor Unit) Fig. 1 is a schematic cross-sectional view of a semiconductor unit according to this embodiment. The semiconductor unit 1 according to this embodiment is a semiconductor device used as a power semiconductor in an electric vehicle. However, the semiconductor unit 1 may be used for any purpose. As shown in Fig. 1, the semiconductor unit 1 has a heat dissipation member 10, a semiconductor chip 12, wiring 14, a joint 16, a joint 17, and a housing 18.

[0013] The semiconductor chip 12 is a component having a semiconductor. Although not shown in the drawings, the semiconductor chip 12 may have any configuration. For example, it may include a substrate, a semiconductor element such as a diode formed on the substrate, a top electrode provided on the top surface of the substrate (the surface opposite the heat dissipation member 10) and connected to the semiconductor element, a back electrode provided on the back surface of the substrate (the surface facing the heat dissipation member 10) and connected to the semiconductor element, and a wire connected to the wiring 14. The substrate of the semiconductor chip 12 is made of silicon carbide (SiC), and more specifically, single-crystal silicon carbide. The material of the substrate of the semiconductor chip 12 is not limited to silicon carbide and may be any material.

[0014] The semiconductor chip 12 is provided on the surface 20A of the heat dissipation member 10. More specifically, wiring 14 is provided on the surface 20A of the heat dissipation member 10 via a bonding portion 17. The semiconductor chip 12 is provided on the wiring 14 via a bonding portion 16. That is, the bonding portion 17, wiring 14, bonding portion 16, and semiconductor chip 12 are stacked in this order on the surface 20A of the heat dissipation member 10. The wiring 14 is made of a conductive material and may be made of a metal such as a copper alloy. The bonding portions 16 and 17 are members that bond the wiring 14 and the semiconductor chip 12 and may be made of, for example, solder or brazing material. Furthermore, eutectic bonding may be used to bond between the semiconductor chip 12 and the wiring 14, and between the wiring 14 and the heat dissipation member 10, and metallized layers may be formed as the bonding portions 16 and 17.

[0015] The housing 18 is a member that houses the protrusions 30 (described below) formed on the surface 20B opposite the surface 20A of the heat dissipation member 10. A cooling medium (e.g., water) is supplied inside the housing 18. When the protrusions 30 come into contact with the cooling medium, the heat dissipation member 10 transfers heat from the protrusions 30 to the cooling medium and dissipates the heat. The housing 18 may also be provided with an annular sealing member. The annular sealing member maintains the sealing between the housing 18 and the heat dissipation member 10 and can serve to relieve stress against pressing forces on the heat dissipation member 10. The configuration of the housing 18 may be arbitrary. The housing 18 is not an essential component and may not be provided in the semiconductor unit 1.

[0016] The configuration of the semiconductor unit 1 described above is an example, and any configuration may be used.

[0017] (Heat Dissipation Member) The heat dissipation member 10 is a member that dissipates heat generated from the semiconductor chip 12 while insulating the semiconductor chip 12. In other words, the heat dissipation member 10 is a member that combines the functions of an insulating substrate for the semiconductor chip 12 and a heat sink. However, the heat dissipation member 10 is not limited to being provided in the semiconductor unit 1 to dissipate heat while insulating the semiconductor chip 12, and may be used to dissipate heat from any member.

[0018] 2 is a schematic cross-sectional view of the heat dissipation member 10. The heat dissipation member 10 is made of silicon nitride (Si ３ N４ ) as a main component. Here, the term "main component" may refer to a content of silicon nitride relative to the entire heat dissipation member 10 of 50 mol% or more. The content of silicon nitride in the heat dissipation member 10 is preferably 75 mol% or more and 99 mol% or less, more preferably 85 mol% or more and 98.5 mol% or less, and even more preferably 90 mol% or more and 98 mol% or less, relative to the entire heat dissipation member 10. Furthermore, the heat dissipation member 10 (a heat dissipation member having silicon nitride as a main component) is preferably a silicon nitride sintered body. A silicon nitride sintered body can be said to be a sintered body having silicon nitride as a main component. The heat dissipation member 10 may contain a secondary component that is a component other than the main component. The secondary component may be a substance containing at least one element selected from the group consisting of Group 2 (alkaline earth metals), Group 3 (rare earth elements (scandium group)), Group 4 (titanium group), Group 5 (earth metals (vanadium group)), Group 13 (boron group (earth metals)), and Group 14 (carbon group). The heat dissipation member 10 contains, as the secondary component, a rare earth oxide (RE ２ O ３Preferably, the heat dissipation member 10 contains at least one of rare earth oxide (MgO) and magnesium oxide (MgO), and more preferably contains both a rare earth oxide and magnesium oxide. The rare earth oxide content of the heat dissipation member 10 is preferably 0.1 mol % to 15 mol %, more preferably 0.2 mol % to 10 mol %, and even more preferably 0.5 mol % to 5 mol % based on the entire heat dissipation member 10. The rare earth oxide is selected from at least one selected from the group consisting of yttrium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, erbium oxide, ytterbium oxide, and lutetium oxide. The magnesium oxide content of the heat dissipation member 10 is preferably 0.1 mol % to 10 mol %, more preferably 0.2 mol % to 5 mol %, and even more preferably 0.5 mol % to 3 mol % based on the entire heat dissipation member 10. The heat dissipation member 10 preferably contains silicon oxide, zirconium oxide, and titanium oxide in a total amount of 5 mol% or less relative to the entire heat dissipation member 10 for purposes such as controlling the thickness of the crystal grain boundaries, promoting the crystallization of the grain boundary glass phase, and removing oxygen impurities contained in silicon nitride. By including these substances in an amount of 5 mol% or less, a decrease in volume resistivity, etc., can be suppressed. The total content of silicon oxide, zirconium oxide, and titanium oxide is more preferably 3 mol% or less, and even more preferably 1 mol% or less. Furthermore, the total content of silicon oxide, zirconium oxide, and titanium oxide in the heat dissipation member 10 is preferably 0.1 mol% to 5 mol%, more preferably 0.2 mol% to 3 mol%, and even more preferably 0.5 mol% to 1 mol%. By including these main and subcomponents in the above amounts, the heat dissipation performance of the heat dissipation member 10 can be improved while maintaining its mechanical properties.

[0019] The heat dissipation member 10 has a volume resistance of 1.0×10 at room temperature (for example, 20° C.). １４Preferably, the resistance is higher than Ω·cm. This ensures proper insulation. The volume resistivity can be measured by a DC three-terminal method in accordance with JIS C2141:1992. The sample for measuring the volume resistivity is, for example, a sample obtained by processing the heat dissipation member 10 into a size of 50×50×1 mm. The volume resistivity is the average value obtained by measuring two samples (n=2). The heat dissipation member 10 preferably has a thermal conductivity of 60 W / m·K or higher. This ensures heat dissipation. The thermal conductivity can be measured by a laser flash method in accordance with JIS R1611:2010. The sample for measuring the thermal conductivity is, for example, a sample obtained by processing the heat dissipation member 10 into a size of 5×5×1 mm. The thermal conductivity is the average value obtained by measuring two samples (n=2). The heat dissipation member 10 preferably has a three-point bending strength of 600 MPa or higher. This improves mechanical reliability. The three-point bending strength can be measured by a room temperature bending strength test method conforming to JIS R1601:2008. For example, a sample obtained by processing the heat dissipation member 10 into a size of 3 × 45 × 4 mm is used for measuring the three-point bending strength. The three-point bending strength is measured over a span of, for example, 30 mm. The three-point bending strength is the average value obtained by measuring 10 samples (n = 10).

[0020] 2, the heat dissipation member 10 includes a base portion 20 and a protruding portion 30 that protrudes from the surface 20B side of the base portion 20. In the heat dissipation member 10, the base portion 20 and the protruding portion 30 are integrally formed. That is, in the heat dissipation member 10, the base portion 20, which is primarily made of silicon nitride, and the protruding portion 30, which is primarily made of silicon nitride, are continuously and integrally formed, and no other member, such as a bonding layer, exists between the base portion 20 and the protruding portion 30. Furthermore, it can be said that the protruding portion 30 protrudes directly from the surface 20B of the base portion 20 without any other member interposed therebetween.

[0021] (Base) The base 20 is a plate-shaped member. Here, the term "plate-shaped" is not limited to a flat plate shape, and may refer, for example, to a shape in which the width of the main surface is greater than the thickness. A direction along the thickness direction of the base 20 is referred to as the Z direction. The surface (main surface) of the base 20 opposite the Z direction is the surface 20A on which the semiconductor chip 12 is mounted. The surface (main surface) of the base 20 on the Z direction side is the surface 20B opposite to the surface 20A. Note that the base 20 is a flat plate that is rectangular when viewed from the Z direction, but is not limited thereto and may have any shape. For example, the base 20 may be polygonal or have a curved shape (such as a circle) when viewed from the Z direction. The base 20 may not be flat, but may be curved.

[0022] The thickness t of the base portion 20 is preferably 0.5 mm to 5.0 mm, more preferably 0.6 mm to 3.0 mm, and even more preferably 0.8 mm to 2.0 mm. By setting the thickness t within this range, the heat dissipation performance can be improved while maintaining the mechanical properties of the heat dissipation member 10. The thickness t is the distance from the surface 20A to the surface 20B in the Z direction.

[0023] (Protrusion) Fig. 3 is a schematic diagram of the heat dissipation member as viewed from the Z direction. As shown in Fig. 2, the protrusion 30 protrudes in the Z direction from the surface 20B of the base 20. Specifically, the protrusion 30 includes a plurality of protrusions 32, each of which protrudes in the Z direction from the surface 20B. As shown in Figs. 2 and 3, the protrusions 32 are arranged in a two-dimensional matrix on the surface 20B. Below, examples of the size, shape, number, and arrangement of the protrusions 32 will be described, but the size, shape, number, and arrangement of the protrusions 32 are not limited to those described below and may be arbitrary.

[0024] Here, the terminal end of the protrusion 32 on the base portion 20 side is referred to as the base end 32A, and the diameter of the circumscribing circle of the outer periphery at the base end 32A of the protrusion 32 is referred to as the diameter Dr. The circumscribing circle of the outer periphery at the base end 32A may refer to the smallest circle (minimum inclusive circle) that includes the entire cross-section of the base end 32A of the protrusion 32. Furthermore, the tip end of the protrusion 32 opposite the base end 32A is referred to as the tip end 32B, and the diameter of the circumscribing circle of the outer periphery at the tip end 32B of the protrusion 32 is referred to as the diameter Dt. The circumscribing circle of the outer periphery at the tip end 32B may refer to the smallest circle that includes the entire cross-section of the tip end 32B of the protrusion 32.

[0025] In this case, it is preferable that the diameter Dr at the base end 32A of the protrusion 32 is larger than the diameter Dt at the tip end 32B. Having the diameter Dr larger than the diameter Dt prevents infrared rays radiated from the protrusion 32 from interfering with other protrusions 32 during radiative cooling, allowing for appropriate heat dissipation. Furthermore, it is preferable that the ratio Dr / Dt of the diameter Dt to the diameter Dt be 1.1 or greater and 100 or less. A ratio Dr / Dt of 1.1 or greater can prevent a decrease in radiative cooling capacity and a decrease in yield during the demolding process. Furthermore, a ratio Dr / Dt of 100 or less can prevent damage during the manufacturing process or mounting due to the tip of the protrusion 32 becoming too thin. The ratio Dr / Dt is more preferably 1.2 or greater and 10 or less, and even more preferably 1.5 or greater and 5 or less. Having the ratio Dr / Dt within this range allows for more appropriate heat dissipation.

[0026] The protrusion 32 does not necessarily have to have a diameter Dr greater than the diameter Dt, and may have any shape, such as a diameter Dr being equal to the diameter Dt. For example, although the protrusion 32 has a truncated cone shape in this embodiment, the shape is not limited thereto, and may be a cylindrical shape, a conical shape, a prism shape, a pyramidal shape, a polygonal truncated pyramidal shape, a solid of revolution shape having a Gaussian distribution or a Lorentz distribution, or the like.

[0027] In this embodiment, the width (cross-sectional area) of the protrusion 32 decreases from the base end 32A to the tip end 32B. In other words, the diameter of the circumscribed circle of the outer periphery of the protrusion 32 decreases from the base end 32A to the tip end 32B. In other words, the protrusion 32 has a tapered shape that gradually becomes thinner toward the tip end 32B. The tapered shape more effectively prevents infrared rays emitted from the protrusion 32 from interfering with other protrusions 32, allowing for appropriate heat dissipation and facilitating manufacturing by, for example, allowing for appropriate demolding during manufacturing.

[0028] However, the protrusion 32 is not limited to a tapered shape. FIG. 4 is a schematic diagram illustrating another example of a heat dissipation member. For example, as shown in FIG. 4 , the protrusion 32 has a diameter Dr greater than the diameter Dt, but may have a stepped shape rather than a tapered shape. That is, the protrusion 32 may have a uniform width (cross-sectional area) from the base end 32A to the intermediate portion 32C between the base end 32A and the tip end 32B, and a uniform width (cross-sectional area) from the intermediate portion 32C to the tip end 32B. The width (cross-sectional area) in the section from the base end 32A to the intermediate portion 32C may be larger than the width (cross-sectional area) in the section from the intermediate portion 32C to the tip end 32B. Although FIG. 4 illustrates a two-step shape, the protrusion 32 may have any stepped shape with three or more steps.

[0029] As shown in FIG. 2 , the length h of the protrusion 30 (protrusion 32) is preferably 1 mm or more and 50 mm or less, more preferably 2 mm or more and 30 mm or less, and even more preferably 3 mm or more and 20 mm or less. Having the length h within this range can improve heat dissipation. The length h is the distance from the base end 32A to the tip end 32B in the Z direction. The ratio h / t of the length h to the thickness t is not particularly limited, but is preferably 0.2 to 100, more preferably 0.5 to 50, and even more preferably 1.5 to 25. The ratio h / Dr of the length h to the diameter Dr is not particularly limited, but is preferably 0.2 to 100, more preferably 0.5 to 30, and even more preferably 1 to 20. Having the ratios h / t and h / Dr within these ranges can improve heat dissipation.

[0030] As shown in FIG. 3 , the average distance between the centers of adjacent protrusions 32 as viewed in the Z direction is referred to as the pitch P. The average distance between the centers of adjacent protrusions 32 refers to the average value of the distance between each pair of adjacent protrusions 32. The pitch P is not particularly limited, but is preferably 0.7 mm to 15 mm, more preferably 1 mm to 12 mm, and even more preferably 2 mm to 10 mm. Having the pitch P within this range can improve heat dissipation. The ratio P / h of the pitch P to the length h is also not particularly limited, but is preferably 0.014 to 15, more preferably 0.03 to 6, and even more preferably 0.05 to 4. The ratio P / Dr of the pitch P to the diameter Dr is also not particularly limited, but is preferably 0.04 to 80, more preferably 0.25 to 12, and even more preferably 0.6 to 3. Having the ratio P / h and the ratio P / Dr within these ranges can improve heat dissipation.

[0031] 3 , the direction perpendicular to the Z direction is the X direction, and the direction perpendicular to the Z direction and the X direction is the Y direction. In this case, the arrangement of the protrusions 32 is determined in consideration of the flow rate and flow velocity of the cooling medium flowing through the heat dissipation member and the heat dissipation characteristics, and is not particularly limited. The protrusions 32 may be arranged in a lattice pattern, i.e., so that the protrusions 32 are located on each of the lattices arranged in the X direction and the Y direction, or they may be arranged in a direction intersecting the X direction, or they may be arranged so that the protrusions 32 are located only in a portion of each of the lattices arranged in the X direction and the Y direction.

[0032] Preferably, the heat dissipation member 10 satisfies at least one of the following conditions: the thickness of the base portion 20 is 0.5 mm or more and 5.0 mm or less; and the diameter Dr of the protrusion 30 is larger than the diameter Dt.

[0033] (Method for Manufacturing Heat Dissipation Member) Next, a method for manufacturing the heat dissipation member 10 described above will be described. However, the manufacturing method described below is only an example, and the heat dissipation member 10 may be manufactured by any method, such as 3D printing, injection molding, or cast molding, and the method is appropriately selected depending on the production volume and the complexity of the shape. Injection molding is particularly preferred when manufacturing a large quantity.

[0034] 5 is a flowchart illustrating an example of a method for manufacturing a heat dissipation member according to this embodiment. As shown in FIG. 5, this manufacturing method first performs a raw material mixing step (step S10). The raw material mixing step is a step of mixing a ceramic powder having a desired composition with a resin, a curing agent, and a solvent to obtain a slurry-like ceramic material (hereinafter referred to as "slurry").

[0035] The ceramic powder is a raw material of the heat dissipation member 10 and contains the components contained in the heat dissipation member 10. That is, the ceramic powder contains silicon nitride powder. The 50% particle diameter D ５０ is preferably 0.1 μm or more and less than 1.0 μm, more preferably 0.1 μm or more and 0.9 μm or less, and even more preferably 0.1 μm or more and 0.8 μm or less. By setting the particle size within this range, appropriate sintering can be achieved. ５０ The measurement method can be performed by measuring a diluted slurry containing the ceramic material using a Horiba, Ltd. LA-950V2 laser diffraction / scattering particle size distribution analyzer. The content of silicon nitride powder relative to the total ceramic powder is preferably 75 mol% to 99 mol%, more preferably 85 mol% to 98 mol%, and even more preferably 90 mol% to 98.5 mol%. This allows for the appropriate production of a heat dissipation member 10 whose main component is silicon nitride.

[0036] The ceramic powder also contains a sintering aid. The sintering aid promotes sintering. Examples of the sintering aid include sintering aids containing at least one element selected from the group consisting of Group 2 (alkaline earth metals), Group 3 (rare earth elements (scandium group)), Group 4 (titanium group), Group 5 (earth metals (vanadium group)), Group 13 (boron group (earth metals)), and Group 14 (carbon group). Examples of the sintering aid include rare earth oxides (RE ２ O ３ Preferably, the ceramic powder contains at least one of rare earth oxide (MgO) and magnesium oxide (MgO), and more preferably contains both a rare earth oxide and magnesium oxide. The ceramic powder preferably contains a rare earth oxide in an amount of 0.1 mol% to 15 mol%, more preferably 0.2 mol% to 10 mol%, and even more preferably 0.5 mol% to 5 mol% based on the total ceramic powder. The rare earth oxide is selected from at least one of yttrium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, erbium oxide, ytterbium oxide, and lutetium oxide. The ceramic powder preferably contains a magnesium oxide in an amount of 0.1 mol% to 10 mol%, more preferably 0.2 mol% to 5 mol%, and even more preferably 0.5 mol% to 3 mol% based on the total ceramic powder. The ceramic powder preferably contains silicon oxide, zirconium oxide, and titanium oxide in a total amount of 5 mol% or less relative to the entire ceramic powder for the purposes of controlling the thickness of the crystal grain boundaries, promoting the crystallization of the grain boundary glass phase, and removing oxygen impurities contained in silicon nitride. By limiting the content of these substances to 5 mol% or less, a decrease in volume resistivity, etc. can be suppressed. The total content of silicon oxide, zirconium oxide, and titanium oxide is more preferably 3 mol% or less, and even more preferably 1 mol% or less. Furthermore, the total content of silicon oxide, zirconium oxide, and titanium oxide in the ceramic powder is preferably 0.1 mol% or more and 5 mol% or less, more preferably 0.2 mol% or more and 3 mol% or less, and even more preferably 0.5 mol% or more and 1 mol% or less.

[0037] The resin is a component for forming the ceramic material into a desired shape in the curing process described below, and examples thereof include known curable resins. The resin used in this embodiment is required to have shape retention in the curing process and to form a three-dimensional network structure by polymerization reaction. The resin is preferably liquid, as it increases the fluidity of the slurry and provides good filling properties into the mold.

[0038] Furthermore, the resin must be easily removable from the ceramic molded body in a degreasing process after the curing process and before sintering. Examples of resins used in this embodiment include epoxy resins, phenolic resins, melamine resins, acrylic resins, and urethane resins. Among these, epoxy resins are preferred due to their excellent shape retention. Examples of epoxy resins include glycidyl ether epoxy resins of bisphenols such as bisphenol A and bisphenol F, phenol novolac epoxy resins, cresol novolac epoxy resins, glycidyl amine epoxy resins, glycidyl ether epoxy resins such as aliphatic epoxy resins, glycidyl ester epoxy resins, methyl glycidyl ether epoxy resins, cyclohexene oxide epoxy resins, and rubber-modified epoxy resins.

[0039] The curing agent is used to harden the resin and is selected depending on the resin to be used. As the curing agent, a water-soluble agent that quickly hardens the resin is preferred, and examples thereof include amine-based curing agents, acid anhydride-based curing agents, polyamide-based curing agents, etc. Amine-based curing agents are preferred because they react quickly, and acid anhydride-based curing agents are preferred because they can produce a cured product with excellent thermal shock resistance.

[0040] Examples of the amine-based curing agent include aliphatic amines, alicyclic amines, and aromatic amines, and any of monoamines, diamines, triamines, and polyamines can be used. Examples of the acid anhydride-based curing agent include methyltetrahydrophthalic anhydride and dibasic acid polyanhydrides.

[0041] The solvent adjusts the viscosity of the mixture of raw materials to make it into a slurry, and makes it easier to fill the slurry into the mold. ２ O), alcohols, and other organic solvents can be used.

[0042] The ceramic powder, resin, curing agent, and solvent are mixed to form a slurry. A dispersant or the like is added as needed. Mixing can be performed by a known method, such as a dissolver, homomixer, kneader, roll mill, sand mill, ball mill, bead mill, vibrator mill, high-speed impeller mill, ultrasonic homogenizer, shaker, planetary mill, planetary mixer, in-line mixer, or the like.

[0043] As a dispersant to be added as needed, a pH adjuster, a surfactant, a polymer dispersant, etc. can be appropriately selected and added to dissociate the aggregates of the ceramic material and further disperse it. It is preferable that the pH adjuster, surfactant, polymer dispersant, etc. do not adversely affect the gelation of the curable resin.

[0044] The viscosity of the slurry may be any viscosity that allows easy filling in the slurry injection step described below. For example, the viscosity at a shear rate of 10 [1 / s] is preferably 50 Pa·s or less, and more preferably 20 Pa·s or less. Considering handleability after filling, the viscosity of the slurry is more preferably in the range of 0.1 Pa·s to 10 Pa·s. The viscosity of the slurry can be easily adjusted by the amount of solvent used and the amount of resin added in the raw materials used. The viscosity at a shear rate of 10 [1 / s] can be measured using an MCR302 manufactured by Anton Paar. A cone plate can be used as the measurement jig.

[0045] In addition, air or the like may be entrained during mixing in the raw material mixing step, and the resulting slurry may contain gas. Therefore, if necessary, a degassing step for removing gas contained in the slurry may be performed before the subsequent slurry injection step.

[0046] (Slurry Pouring Step) Next, the slurry obtained through the raw material mixing step and, if necessary, the degassing step is poured into a forming mold (step S12). The forming mold has a shape that matches the shape of the heat dissipation member 10. Here, it is preferable to estimate the shrinkage rate of the sintered body for the ceramic composition and firing conditions of this example in advance, and to carry out a mold design that corrects for the shrinkage rate.

[0047] (Curing Step) Next, the curing step is carried out (Step S14). The curing step is a step in which the resin component contained in the slurry poured into the mold is cured to harden the ceramic material into a desired shape. In the curing step, the slurry is cured under desired curing conditions according to the characteristics of the slurry.

[0048] For example, in the case of a room temperature curing type slurry, the reaction begins as soon as the resin and curing agent are mixed, and the mixture is cured by leaving it for a predetermined time. In the case of a heat curing type slurry, the mixture is heated to a desired temperature and allowed to cure for a sufficient time.

[0049] (Molding Step) Next, the demolding step is carried out (step S16). In the demolding step, the hardened ceramic material body hardened in the hardening step is removed from the molding die.

[0050] (Drying Process) After the demolding process, a drying process is carried out (step S18). The drying process is a process in which moisture, volatile solvents, etc. are removed from the hardened body obtained in the demolding process, and the hardened body is dried to form a molded body. In the drying process, the hardened body is dried gently so as not to cause cracks, etc. in the hardened body. In other words, the hardened body is dried while preventing the occurrence of cracks, etc. due to shrinkage stress caused by the difference in drying speed between the surface and the interior of the hardened body.

[0051] The drying step is carried out under relatively mild conditions, such as 25°C to 50°C, a relative humidity of 10% to 95%, and a period of 48 hours to 7 days, to remove moisture and other substances contained in the hardened body. The drying step is preferably carried out until the moisture content of the hardened body is 20% or less of its bone-dry mass.

[0052] (Debinding Step) Next, the debinding step is carried out (Step S20). The debinding step is a step in which resin, non-volatile solvent, etc. are removed from the green body obtained in the drying step to obtain a debound body. In the debinding step, most of the components that inhibit sintering in the subsequent sintering step are removed. If a large amount of components that inhibit sintering remain, pores may be formed in the sintered body during sintering, or carbides may be generated as by-products, which may prevent the desired properties from being obtained as a final product.

[0053] The degreasing step is carried out under conditions such as slowly raising the temperature to 250°C to 800°C over a long period of time and maintaining the temperature, for a total treatment time of a relatively long period of time such as 3 to 14 days, to remove the resin components and the like contained in the compact. Here, the degreasing step, particularly for silicon nitride, is preferably carried out until the amount of carbon remaining in the compact is 900 ppm or less.

[0054] (Firing Step) Next, the firing step is carried out (step S22). The firing step is a step in which the degreased body that has been subjected to the degreasing step is fired to sinter the ceramic material, thereby obtaining a sintered body, i.e., the heat dissipation member 10. The firing step sinters the ceramic material to obtain the sintered body, i.e., the heat dissipation member 10, and a known firing method may be applied.

[0055] In the firing process, in order to improve the thermal conductivity of the sintered body and ensure its mechanical properties, to allow sufficient grain growth of silicon nitride crystal grains, and to obtain a dense sintered body without pores, it is preferable to perform firing under the following conditions: The atmosphere in the furnace is preferably a nitrogen atmosphere with an oxygen concentration of 50 ppm or less, and is also a pressurized atmosphere. The pressure in the furnace atmosphere is preferably in the range of 5 atm to 10 atm. Furthermore, the maximum firing temperature in the firing process is preferably in the range of 1800°C to 1950°C. Furthermore, the firing time is preferably in the range of 8 hours to 72 hours.

[0056] (Secondary Firing Step) The sintered body obtained in the firing step may be subjected to a secondary firing step in order to further obtain a sintered body having desired properties. In this secondary firing step, the sintered body obtained in the firing step (primary firing) may be further subjected to high-pressure treatment to densify the structure of the sintered body or crystallize the grain boundary glass phase, thereby further improving the thermal conductivity of the sintered body.

[0057] The high-pressure treatment in this secondary firing step can be hot isostatic pressing (HIP), gas pressure firing, hot pressing, etc. Generally, the sintered body obtained by sintering has high strength, and is preferably treated by HIP at 1500°C to 1750°C and in the range of 50 MPa to 200 MPa.

[0058] (Effects) As described above, the heat dissipation member 10 according to this embodiment includes a base portion 20 and a protruding portion 30 protruding from one surface 20B of the base portion 20, and is a member primarily composed of silicon nitride. The thickness t of the base portion 20 of the heat dissipation member 10 is preferably 0.6 mm or more and 2.0 mm or less. By setting the thickness of the base portion 20 within this range in a heat dissipation member 10 made of silicon nitride, the heat dissipation performance of the heat dissipation member 10 can be improved while maintaining its mechanical properties. Furthermore, for example, when mounting a semiconductor chip 12, if the insulating substrate and the heat sink are separate, dissimilar material joining is required to join them. In contrast, in this embodiment, the base portion 20 functioning as the insulating substrate and the protruding portion 30 functioning as the heat sink are integrated. This reduces the number of dissimilar material joints, suppresses thermal stress caused by differences in the coefficients of expansion between the dissimilar materials, and improves mechanical reliability. This also prevents the overall thickness of the semiconductor unit 1 from increasing, thereby achieving a low profile. Furthermore, there is an increasing demand for reducing noise caused by switching of power semiconductors, and therefore a need for a simpler configuration of the heat dissipation member. In response to this, the heat dissipation member 10 according to this embodiment integrates the base portion 20, which functions as an insulating substrate, and the protrusion portion 30, which functions as a heat sink, and therefore the configuration of the heat dissipation member 10 can be simplified while minimizing the number of interfacial layers between different materials.

[0059] Furthermore, it is preferable that the diameter Dr of the circumscribing circle around the outer periphery of the base end 32A of the protrusion 30 on the base 20 side is larger than the diameter Dt of the circumscribing circle around the outer periphery of the tip end 32B on the opposite side to the base 20. When the diameter Dr is larger than the diameter Dt, the radiation efficiency can be increased, and heat can be dissipated appropriately.

[0060] Furthermore, the ratio Dr / Dt of the diameter Dr to the diameter Dt is preferably 1.1 or more and 100. This allows for more efficient heat dissipation.

[0061] Furthermore, it is preferable that the width of the protrusion 30 becomes smaller from the base end 32A to the tip end 32B. By making the protrusion 30 tapered in this way, heat can be dissipated more effectively.

[0062] Preferably, the heat dissipation member 10 further contains magnesium oxide and a rare earth oxide, which allows the heat dissipation member 10 to be sintered appropriately and improves mechanical reliability.

[0063] The heat dissipation member 10 has a volume resistivity of 1.0×10 at room temperature. １４ It is preferable that the electrical resistance is higher than Ω·cm, the thermal conductivity is 60 W / m·K or more, and the three-point bending strength is 600 MPa or more. This makes it possible to appropriately ensure insulation properties, heat dissipation properties, and mechanical reliability.

[0064] The semiconductor unit 1 according to this embodiment also includes a heat dissipation member 10 and a semiconductor chip 12 provided on the front surface 20A side of the heat dissipation member 10. The semiconductor unit 1 according to this embodiment can appropriately dissipate heat from the semiconductor chip 12.

[0065] (Examples) Next, examples will be described. <Evaluation of radiative cooling performance depending on the shape of a heat dissipation member by radiative cooling simulation> Using optical simulation software (Ocean, manufactured by Eclat Digital Research), the protrusions of the heat dissipation member were fixed at Dr: 3 mm and h / Dr: 3, and the arrangement was also fixed, and the amount of radiant heat was calculated when the shape of the protrusions was changed. That is, light was emitted from the radiator with the protrusions using Lambertian approximation, and the amount of energy reaching the integrating sphere was integrated to estimate the total amount emitted. The results are shown in Table 1, where the radiant heat ratio for each shape is set to 1 for a prismatic column. When Dr / Dt was greater than 1.1, the radiant heat ratio was approximately 1.6 times. Table 2 shows the manufacturing conditions of the heat dissipation member for each example and the evaluation results for the composition constituting the member, and Tables 3 and 4 show the evaluation results for each example. Here, Examples 1 to 4 and 10 to 13 are examples, and Examples 5 to 9 are comparative examples.

[0066]

[0067] Example 1 In Example 1, a heat dissipation member was manufactured using composition C1. Specifically, in Example 1, silicon nitride powder (SN-9FWS manufactured by Denka), magnesium oxide and yttrium oxide as sintering aids, ethanol as a solvent, polycarboxylic acid as a dispersant, epoxy resin as a resin, and triethylenetetramine as a curing agent were mixed to produce a slurry. The compounding ratio of silicon nitride to sintering aid was as shown in Table 2. The resulting slurry was poured into a mold and held at 50°C for 5 hours to harden the slurry, yielding a hardened body. The hardened body was then demolded from the mold, humidified and dried at 30°C for 4 days, and then hot-air dried at 50°C to obtain a dried molded body. The dried molded body was then heated at 600°C for 3 hours to degrease it, yielding a molded body. The resulting molded body was fired (sintered) under the conditions shown in Table 2 to produce a heat dissipation member. The mold used was designed by evaluating the shrinkage of the fired body (dried green body, green body) under each firing condition in advance and correcting for the shrinkage. The resulting green body had a base size of 50 mm x 50 mm, and 120 protrusions arranged in a checkered pattern (checkered flag) within a 38 mm x 38 mm area of ​​the base.

[0068] The thermal conductivity, volume resistivity, and three-point bending strength of the heat dissipation member of Example 1 were measured. The methods for each measurement were the same as those described in the above-mentioned embodiment. Instead of directly processing the heat dissipation member of Example 1, each measurement sample was prepared by processing a 60 x 60 x 6 mm reference sample manufactured under the same conditions as the heat dissipation member of Example 1 (and simultaneously firing) to the size required for each measurement. The measurement results are shown in Table 2.

[0069] As shown in Table 3, the heat dissipation member of Example 1, as described in the above embodiment, had a base portion 20 and a protruding portion 30 integrally formed. The thickness t of the base portion 20 was 2.3 mm, the diameter Dr was greater than the diameter Dt, and the ratio Dr / Dt was 3. The size of the base portion was approximately 50 mm x 50 mm. The thickness t of the base portion 20 was adjusted using a surface grinder to ensure flatness of the heat dissipation member after firing, in order to bond it to a copper plate for the heat dissipation characteristic evaluation described below. Then, a 20 W output silicon rubber heater simulating a semiconductor chip, a copper plate (size 100 mm x 100 mm, thickness 5 mm), and a heat dissipation member were each uniformly coated with Shin-Etsu Chemical's heat dissipation silicone oil compound G-777 (thermal conductivity: 3.3 W / m K) using a squeegee. The silicone rubber heater was placed face down and the protruding portion was left to stand for 20 minutes using a 5 kg cast iron weight to bond them. That is, the number of different material interface layers is two.

[0070] (Examples 2 to 4) In Examples 2 to 4, compositions C2 to C4 were used, and heat dissipation members were manufactured in the same manner as in Example 1, except that the composition of the ceramic material and the firing conditions were changed as shown in Table 2. Measurement samples were processed from reference samples in the same manner as in Example 1. In Examples 2 to 4, the base portion 20 and the protrusions 30 were also integrally formed, and the thickness t of the base portion 20 was 1.1, 1.6, and 2.3 mm, respectively, as shown in Table 3, and the ratio Dr / Dt was 3. Furthermore, a silicon rubber heater, a copper plate, and a heat dissipation member were joined in the same manner as in Example 1. The number of interfacial layers between different materials was two.

[0071] (Example 5) In Example 5, a heat dissipation member was manufactured in the same manner as in Example 1, except that the thickness t of the base portion 20 was set to 0.4 mm. A measurement sample was processed from a reference sample in the same manner as in Example 1. When the silicon rubber heater, copper plate, and heat dissipation member were joined together and left to stand for 20 minutes with a 5 kg cast iron weight, cracks occurred in the base portion, and the heat dissipation characteristics could not be evaluated.

[0072] (Example 6) In Example 6, composition C1 was used, but only the portion corresponding to the base was produced by sintering composition C1. The resulting plate-shaped sample, measuring 50 mm x 50 mm and 1 mm thick, served as part of the base. Next, a heat dissipation member was separately prepared, with the arrangement and surface area of ​​the Al (aluminum) protrusions being approximately the same as in Example 1. The thickness of a portion of the Al base 20 was 3 mm, and the ratio Dr / Dt was 1 (the diameter Dr was the same as the diameter Dt). Similarly to Example 1, a silicone rubber heater, copper plate 1, the sintered plate-shaped sample of C1, and the Al heat dissipation member were bonded together. The sintered plate-shaped sample of C1 and the Al heat dissipation member were bonded together using a heat dissipation silicone oil compound. Therefore, the total thickness of the base 20, ignoring the bonding thickness of the heat dissipation silicone oil compound, was approximately 4 mm, and the number of dissimilar material interface layers was three.

[0073] Example 7 Example 7 was configured in the same manner as Example 6, except that only a portion corresponding to a part of the base portion was formed from the composition C5 (AlN). That is, the number of different material interface layers was three.

[0074] (Example 8) In Example 8, a conventional DCB (Direct Copper Bonding) substrate was simulated, and a copper plate 2 measuring 50 x 50 mm and 1 mm thick was added between the AlN and Al heat dissipation member of the configuration of Example 7, resulting in a silicon rubber heater, copper plate 1, AlN, copper plate 2, and Al heat dissipation member from top to bottom. The AlN and copper plate 2, and the copper plate 2 and Al heat dissipation member were bonded using a heat dissipation silicone oil compound. In other words, the number of interfacial layers between different materials was four.

[0075] (Example 9) In Example 9, only the portion corresponding to a part of the base portion was made of composition C6 (Al ２ O ３ ) was used. That is, the number of different material interface layers was three.

[0076] (Example 10) In Example 10, a heat dissipation member was manufactured in the same manner as in Example 1, except that the ratio Dr / Dt was 1 and the thickness t of the base portion 20 was 1.9 mm. The arrangement of the protrusions was the same as in Example 1. That is, the number of dissimilar material interface layers was two.

[0077] Example 11 In Example 11, a heat dissipation member was manufactured in the same manner as in Example 1, except that composition C7 was used and the thickness t of the base portion 20 was 1.5 mm. That is, the number of dissimilar material interface layers was two.

[0078] In Example 12, a heat dissipation member was manufactured in the same manner as in Example 1, except that the ratio Dr / Dt was 1.5 and the thickness t of the base portion 20 was 1.6 mm. The arrangement of the protrusions was the same as in Example 1. That is, the number of dissimilar material interface layers was two.

[0079] Example 13 In Example 13, a heat dissipation member was manufactured in the same manner as in Example 1, except that the base end 32A was an ellipse with a major axis of 3.0 mm and a minor axis of 1.5 mm, the tip end 32B was an ellipse with a major axis of 2.0 mm and a minor axis of 1.0 mm, i.e., Dr: 3.0 mm, Dt: 2.0 mm, and the ratio Dr / Dt was 1.5, and the thickness t of the base portion 20 was 1.7 mm. The arrangement of the protrusions was the same as in Example 1. That is, the number of dissimilar material interface layers was two.

[0080] <Number of Interface Layers of Different Materials> As is clear from Tables 3 and 4, the number of interface layers of different materials in Examples 1 to 5 and 10 to 13 is two, which simplifies the configuration of the heat dissipation component. Furthermore, the number of interface layers of different materials in Examples 1 to 5 and 10 to 13 is two, which is expected to have a noise reduction effect by significantly reducing the number of interface layers of different materials compared to Example 8, which has a conventional configuration. Furthermore, from Tables 2 to 4, the volume resistivity of the samples of Examples 1 to 5 and 10 to 13 is also 1.0 x 10 １４The electrical resistivity was higher than Ω-cm, and the material functioned satisfactorily as an insulating substrate. Furthermore, improved reliability can be expected during heat cycle testing, as stress due to differences in thermal expansion between different materials can be reduced. <Mechanical Properties> The mechanical properties were evaluated in Tables 3 and 4. When the heat-dissipating silicone oil compound was applied between the interfaces of the different materials and bonded, a 5 kg cast iron weight was applied to the protruding portion and the material was left standing for 20 minutes. If cracks occurred in the heat-dissipating component, an X was given, and if no cracks occurred, an O was given. As mentioned above, Example 5, in which the thickness of the base portion 20 was less than 0.5 mm, had low reliability in terms of mechanical properties. <Heat Dissipation Evaluation> The heat dissipation properties of each heat-dissipating component were evaluated. Heat dissipation properties were evaluated using the following method. A stainless steel water tank with inner dimensions of 70 mm x 70 mm and a depth of 20 mm was prepared, and cooling water ports were provided on opposing sides. The copper plate 1 (size 100 mm x 100 mm, thickness 5 mm) was fastened to the stainless steel water tank via an O-ring and sealed so that the heat dissipation member entered the stainless steel water tank. The cooling water port was connected to an AS ONE Corporation cooling water circulation device SOC1-1100, and the cooling water temperature was set to 25°C to introduce circulating cooling water into the water tank. A TEXIO Corporation DC stabilized power supply PSW-360M160 was connected to the attached silicon rubber heater, and 20 W of power was applied, and the temperature T directly above the silicon rubber heater was measured. Ｈ and the temperature T at the center of the lower surface of the heat dissipation member base Ｌ is measured using a thermocouple. Ｈ and T Ｌ It took about 30 minutes to 1 hour for the material to reach its saturation temperature, and the average temperature over 1 to 2 hours was used for evaluation. Heat dissipation was evaluated using input power Q (20 W in this experiment) and thermal resistance R, expressed by the following formula (1), and the relative values, with Example 7 set to 1.0, are shown in Tables 3 and 4. A lower thermal resistance indicates better cooling performance as a heat dissipation component.

[0081] R = (T Ｈ -T Ｌ ) / Q (unit: ° C. / W) ... (1)

[0082] As shown in Tables 2 to 4, Examples 1-2 and 11-13, in which the base portion 20 and the protrusion portion 30 are integrally formed primarily of silicon nitride, the thickness of the base portion 20 is 0.5 mm or more and 5.0 mm or less, the diameter Dr is greater than the diameter Dt, and the thermal conductivity exceeds 60 W / m·K, show better heat dissipation than the conventional configuration of Example 8. On the other hand, Examples 3-4 have a thermal conductivity of less than 60 W / m·K, but because there are two interfacial layers, the heat dissipation performance is not significantly reduced, and an appropriate level of heat dissipation is ensured. Examples 7 and 8 show that increasing the number of interfacial layers by one reduces heat dissipation. Example 9 has a low thermal conductivity of the base portion and a large number of interfacial layers, resulting in poor heat dissipation. Furthermore, Examples 1, 10, and 12 reveal that even though the same composition C1 is used, Example 1, which has a larger ratio Dr / Dt, has better heat dissipation. By setting the ratio Dr / Dt to 1.1 or more, the yield when the slurry hardened body is demolded during production can be improved, which is preferable.

[0083] Although the embodiments and examples of the present invention have been described above, the embodiments are not limited to the contents of these embodiments and examples. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the above-described components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-described embodiments.

[0084] REFERENCE SIGNS LIST 1 semiconductor unit 10 heat dissipation member 12 semiconductor chip 20 base portion 30 protrusion portion 32 protrusion body 32A base end portion 32B tip portion

Claims

1. A heat dissipation member mainly composed of silicon nitride, A base portion and a protruding portion protruding from one surface of the base portion, The thickness of the base portion is 0.5 mm or more and 5.0 mm or less. Heat dissipation material.

2. The heat dissipation member according to claim 1 , wherein a diameter Dr of a circumscribing circle of an outer periphery of a base end portion on the base portion side of the protrusion is larger than a diameter Dt of a circumscribing circle of an outer periphery of a tip end portion on the opposite side to the base portion.

3. A heat dissipation member mainly composed of silicon nitride, A base portion and a protruding portion protruding from one surface of the base portion, The protrusion has a diameter Dr of a circumscribing circle of an outer periphery of a base end portion on the base portion side that is larger than a diameter Dt of a circumscribing circle of an outer periphery of a tip end portion on the opposite side to the base portion. Heat dissipation material.

4. The heat dissipation member according to claim 2 or 3, wherein a ratio of the diameter Dr to the diameter Dt is 1.1 or more and 100 or less.

5. The heat dissipation member according to claim 2 or 3, wherein the protrusion has a width that decreases from the base end to the tip end.

6. The heat dissipation member according to claim 1 , wherein the heat dissipation member containing silicon nitride as a main component is a silicon nitride sintered body.

7. The heat dissipation member according to claim 1 , further comprising magnesium oxide and a rare earth oxide.

8. Volume resistivity at room temperature is 1.0×10 １４ The heat dissipation member according to claim 1 , having a compressive strength of more than Ω·cm, a thermal conductivity of 60 W / m·K or more, and a three-point bending strength of 600 MPa or more.

9. A heat dissipation member according to any one of claims 1 to 3, and a semiconductor chip provided on the other surface side. Semiconductor unit.