WO2023190141A1

WO2023190141A1 - Heat dissipation member and semiconductor unit

Info

Publication number: WO2023190141A1
Application number: PCT/JP2023/011780
Authority: WO
Inventors: 達雄長嶋; 美紗子貴島; 伸広篠原; 光吉小林
Original assignee: Ａｇｃ株式会社
Priority date: 2022-03-31
Filing date: 2023-03-24
Publication date: 2023-10-05

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 members and semiconductor units

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

In recent years, the movement toward the spread of electric vehicles has been accelerating due to increasing awareness of carbon neutrality and social demands. In order to popularize electric vehicles, it is essential to solve technical issues such as improving cruising range and shortening charging time, and the role played by power semiconductors is becoming increasingly important. Patent Document 1 discloses a silicon nitride circuit board that has a reduced substrate thickness, improves heat dissipation, and also ensures insulation and high reliability. Patent Document 2 proposes a semiconductor device having a structure in which a heat sink member is made of ceramic to relieve thermal stress and pressing force on the heat sink member.

International Publication No. 2020/044974 Japanese Patent Application Publication No. 2008-270295

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 still room for improvement in terms of ensuring appropriate heat dissipation. be. In addition, there is a need for a heat dissipating member that can appropriately ensure heat dissipation and has a simple configuration, and is not limited to applications such as power semiconductors.

The present invention has been made in view of the above 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.

A heat dissipation member according to the present disclosure is a heat dissipation member containing silicon nitride as a main component, and includes a base portion and a protrusion portion protruding from one surface of the base portion, and the thickness of the base portion is It is 0.5 mm or more and 5.0 mm or less.

A heat dissipation member according to the present disclosure is a heat dissipation member containing silicon nitride as a main component, and includes a base portion and a protrusion portion protruding from one surface of the base portion, the protrusion portion being a heat dissipation member containing silicon nitride as a main component. The diameter Dr of the circumscribed circle of the outer periphery of the base end portion on the side of the base portion is larger than the diameter Dt of the circumscribed circle of the outer periphery of the tip portion on the opposite side from the base portion.

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

According to the present invention, the configuration of the heat dissipation member can be simplified and heat dissipation properties can be appropriately ensured.

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 the heat dissipation member. FIG. 3 is a schematic diagram of the heat dissipation member viewed from the Z direction side. FIG. 4 is a schematic diagram 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.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to this embodiment, and if there are multiple embodiments, the present invention may be configured by combining each embodiment. In addition, numerical values include rounding ranges.

(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 used in an electric vehicle. However, the use of the semiconductor unit 1 may be arbitrary. As shown in FIG. 1, the semiconductor unit 1 includes a heat dissipation member 10, a semiconductor chip 12, wiring 14, a joint 16, a joint 17, and a housing 18.

The semiconductor chip 12 is a member that includes a semiconductor. Although not shown, the structure of the semiconductor chip 12 may be arbitrary. For example, a substrate, a semiconductor element such as a diode formed on the substrate, an upper surface electrode provided on the upper surface of the substrate (the surface opposite to the heat dissipating member 10) and connected to the semiconductor element, and a back surface of the substrate (the surface opposite to the heat dissipating member 10). It includes a back electrode provided on the surface on the member 10 side) 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), more specifically, single crystal silicon carbide. The material of the substrate of semiconductor chip 12 is not limited to silicon carbide, but may be any material.

The semiconductor chip 12 is provided on the surface 20A side of the heat dissipation member 10. More specifically, the wiring 14 is provided on the surface 20A of the heat dissipation member 10 via the joint 17. The semiconductor chip 12 is provided on the wiring 14 via a joint 16. That is, on the surface 20A of the heat dissipation member 10, the joint 17, the wiring 14, the joint 16, and the semiconductor chip 12 are stacked in this order. The wiring 14 is made of a conductive member, and may be made of metal such as copper alloy. The

joint parts

16 and 17 are members that join the wiring 14 and the semiconductor chip 12, and may be made of solder or brazing material, for example. Further, eutectic bonding may be used for bonding between the semiconductor chip 12 and the wiring 14, and between the wiring 14 and the heat dissipating member 10, and metallized layers may be formed as the

bonding portions

16 and 17.

The housing 18 is a member that accommodates a protrusion 30 (described later) formed on the surface 20B of the heat dissipation member 10 on the opposite side to the surface 20A. A cooling medium (for example, water) is supplied inside the housing 18 . The heat dissipation member 10 transmits heat from the protrusion 30 to the cooling medium and radiates the heat when the protrusion 30 comes into contact with the cooling medium. Further, the housing 18 may be provided with an annular seal member. The annular seal member maintains the sealing property between the housing 18 and the heat radiating member 10, and can play the role of stress relaxation against the pressing force on the heat radiating 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.

Note that the configuration of the semiconductor unit 1 described above is an example, and may have any configuration.

(heat dissipation member)
The heat radiating member 10 is a member that radiates heat generated from the semiconductor chip 12 while insulating the semiconductor chip 12. That is, the heat dissipation member 10 is a member that functions as both an insulating substrate for the semiconductor chip 12 and a heat sink. However, the heat radiating member 10 is not limited to being provided in the semiconductor unit 1 to radiate heat while insulating the semiconductor chip 12, but may be used to radiate heat from any member.

FIG. 2 is a schematic cross-sectional view of the heat dissipation member. The heat dissipation member 10 has silicon nitride (Si ₃ N ₄ ) as a main component. The main component here may refer to a content rate of 50 mol% or more in the entire heat dissipating member 10. 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 90 mol% with respect to the entire heat dissipation member 10. More preferably, the content is 98 mol% or less. Moreover, it is preferable that the heat dissipation member 10 (the heat dissipation member whose main component is silicon nitride) is a silicon nitride sintered body. A silicon nitride sintered body can be said to be a sintered body whose main component is silicon nitride.
The heat dissipation member 10 may include a subcomponent that is a component other than the main component. Subcomponents include Group 2 (alkaline earth metals), Group 3 (rare earths (scandium group)), Group 4 (titanium group), Group 5 (earth metals (vanadium group)), and Group 13. (Boron group (earth metals)) and Group 14 (carbon group). The heat dissipation member 10 preferably contains at least one of rare earth oxides (RE ₂ O ₃ ) and magnesium oxide (MgO) as subcomponents, and more preferably contains both rare earth oxides and magnesium oxide. The content of the rare earth oxide in the heat dissipating member 10 is preferably 0.1 mol% or more and 15 mol% or less, more preferably 0.2 mol% or more and 10 mol% or less, based on the entire heat dissipating member 10. , more preferably 0.5 mol% or more and 5 mol% or less. Note that the rare earth oxide is selected from at least one kind selected from the group of yttrium oxide, neodymium oxide, samarium oxide, samarium oxide, europium oxide, gadolinium oxide, erbium oxide, ytterbium oxide, and lutetium oxide. The content of magnesium oxide in the heat dissipation member 10 is preferably 0.1 mol% or more and 10 mol% or less, more preferably 0.2 mol% or more and 5 mol% or less, based on the entire heat dissipation member 10. It is more preferably 0.5 mol% or more and 3 mol% or less. In addition, the heat dissipation member 10 is made of silicon oxide, zirconium oxide, etc. for the entire heat dissipation member 10 for purposes such as controlling the thickness of grain boundaries, promoting crystallization of the grain boundary glass phase, and removing impurity oxygen contained in silicon nitride. , and titanium oxide in a total amount of 5 mol % or less. 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, still more preferably 1 mol% or less. Further, in the heat dissipation member 10, the total content of silicon oxide, zirconium oxide, and titanium oxide is preferably 0.1 mol% or more and 5 mol% or less, and more preferably 0.2 mol% or more and 3 mol% or less. , more preferably 0.5 mol% or more and 1 mol% or less.
By including these main components and subcomponents in the above amounts, the heat dissipation performance can be improved while maintaining the mechanical properties of the heat dissipation member 10.

Further, it is preferable that the heat dissipating member 10 has a volume resistivity higher than 1.0×10 ¹⁴ Ω·cm at room temperature (for example, 20° C.). Thereby, insulation can be appropriately ensured. Note that the volume resistance can be measured by the DC three-probe method in accordance with JIS C2141:1992. As a sample for measuring the volume resistance, for example, a sample obtained by processing the heat dissipation member 10 into a size of 50×50×1 mm is used. The volume resistivity is an average value obtained by measuring two samples (n=2).
Moreover, it is preferable that the heat radiating member 10 has a thermal conductivity of 60 W/m·K or more. This ensures heat dissipation. Note that the thermal conductivity can be measured by a laser flash method based on JIS R1611:2010. As a sample for measuring thermal conductivity, for example, a sample obtained by processing the heat dissipation member 10 into a size of 5×5×1 mm is used. The thermal conductivity is an average value obtained by measuring two samples (n=2).
Moreover, it is preferable that the heat dissipation member 10 has a three-point bending strength of 600 MPa or more. Thereby, mechanical reliability can be improved. Note that the three-point bending strength can be measured by a room temperature bending strength test method based on JIS R1601:2008. As a sample for measuring the three-point bending strength, for example, a sample obtained by processing the heat dissipation member 10 into a size of 3 x 45 x 4 mm is used. The three-point bending strength is measured by measuring the measurement sample over a span of 30 mm, for example. The three-point bending strength is an average value obtained by measuring 10 samples (n=10).

As shown in FIG. 2, the heat dissipation member 10 includes a base portion 20 and a protrusion portion 30 that protrudes from the surface 20B side of the base portion 20. The heat dissipation member 10 includes a base portion 20 and a protrusion portion 30 that are integrally formed. That is, in the heat dissipation member 10, a base portion 20 containing silicon nitride as a main component and a protrusion portion 30 containing silicon nitride as a main component are continuously integrally formed, and the base portion 20 and the protrusion portion 30, there is no other member such as a bonding layer. Furthermore, it can be said that the protruding portion 30 directly protrudes from the surface 20B of the base portion 20 without using any other member in between.

(base part)
The base portion 20 is a plate-shaped member. The plate shape here is not limited to a flat plate shape, and may refer to, for example, one in which the width of the main surface is longer than the thickness. One direction along the thickness direction of the base portion 20 is referred to as a Z direction. The surface (principal surface) of the base portion 20 opposite to the Z direction becomes the surface 20A on which the semiconductor chip 12 is mounted. The surface (principal surface) on the Z direction side of the base portion 20 is a surface 20B opposite to the surface 20A. Although the base portion 20 has a rectangular flat plate shape when viewed from the Z direction, it is not limited thereto and may have any shape. For example, the base portion 20 may have a polygonal shape or a shape having a curved surface (such as a circular shape) when viewed from the Z direction. The base portion 20 may not be flat but may be curved.

The thickness t of the base portion 20 is preferably 0.5 mm or more and 5.0 mm or less, more preferably 0.6 mm or more and 3.0 mm or less, and 0.8 mm or more and 2.0 mm or less. More preferred. When the thickness t is within this range, the heat dissipation performance can be improved while maintaining the mechanical properties of the heat dissipation member 10. Note that the thickness t is the distance from the surface 20A to the surface 20B in the Z direction.

(protrusion)
FIG. 3 is a schematic diagram of the heat dissipation member viewed from the Z direction side. As shown in FIG. 2, the protruding portion 30 protrudes from the surface 20B of the base portion 20 toward the Z direction side. Specifically, the protrusion 30 includes a plurality of protrusions 32, and each protrusion 32 protrudes from the surface 20B in the Z direction. As shown in FIGS. 2 and 3, the protrusions 32 are arranged in a two-dimensional matrix on the surface 20B. Hereinafter, examples of the size, shape, number, and arrangement of the protrusions 32 will be explained, but the size, shape, number, and arrangement of the protrusions 32 are not limited to the following description and may be arbitrary. good.

Here, the end portion of the protrusion 32 on the side of the base portion 20 is referred to as a proximal end portion 32A, and the diameter of the circumscribed circle of the outer periphery at the proximal end portion 32A of the protrusion 32 is referred to as the diameter Dr. The circumscribed circle of the outer periphery of the proximal end 32A may refer to the smallest circle (minimum enclosing circle) that includes the entire area of the cross section of the protrusion 32 at the proximal end 32A. Further, the distal end portion of the protruding body 32 opposite to the base end portion 32A is referred to as a distal end portion 32B, and the diameter of the circumscribed circle of the outer periphery of the distal end portion 32B of the protruding body 32 is defined as the diameter Dt. The circumscribed circle of the outer periphery of the tip 32B may refer to the smallest circle that includes the entire area of the cross section of the tip 32B of the protrusion 32.

In this case, it is preferable that the diameter Dr of the protruding body 32 at the base end 32A is larger than the diameter Dt at the distal end 32B. Since the diameter Dr is larger than the diameter Dt, infrared rays emitted from the protruding bodies 32 during radiation cooling are suppressed from interfering with other protruding bodies 32, and heat can be dissipated appropriately.
Furthermore, the ratio Dr/Dt of the diameter Dt to the diameter Dt is preferably 1.1 or more and 100 or less. When the ratio Dr/Dt is 1.1 or more, it is possible to suppress a decrease in radiation cooling ability and suppress a decrease in yield in the demolding process. Further, by setting the ratio Dr/Dt to 100 or less, it is possible to suppress damage during the manufacturing process or mounting due to the tip of the protruding body 32 becoming too thin. The ratio Dr/Dt is more preferably 1.2 or more and 10 or less, and even more preferably 1.5 or more and 5 or less. When the ratio Dr/Dt falls within this range, it becomes possible to dissipate heat more appropriately.

Note that the diameter Dr of the protruding body 32 is not limited to being larger than the diameter Dt, and may have any shape, for example, the diameter Dr may be the same as the diameter Dt. For example, the protruding body 32 has a truncated cone shape in this embodiment, but is not limited to this, and may have a cylindrical shape, a conical shape, a prismatic shape, a pyramid shape, a polygonal truncated pyramid shape, or a rotating body having a Gaussian distribution or a Lorentz distribution. It may be a shape or the like.

In this embodiment, the width (cross-sectional area) of the protruding body 32 decreases from the base end 32A toward the distal end 32B. It can also be said that the diameter of the circumscribed circle on the outer periphery of the protruding body 32 decreases from the base end 32A toward the distal end 32B. That is, the protrusion 32 has a tapered shape that gradually becomes thinner toward the tip 32B. By forming the tapered shape, interference of infrared rays emitted from the protruding body 32 with other protruding bodies 32 can be more appropriately suppressed, heat can be dissipated appropriately, and, for example, demolding can be appropriately performed during manufacturing. , which can be easily manufactured.

However, the protruding body 32 is not limited to having a tapered shape. FIG. 4 is a schematic diagram illustrating another example of the heat dissipation member. For example, as shown in FIG. 4, the diameter Dr of the protrusion 32 is larger than the diameter Dt, but the protrusion 32 may have a stepped shape instead of a tapered shape. That is, the protrusion 32 has a uniform width (cross-sectional area) in the section from the base end 32A to the intermediate part 32C between the base end 32A and the distal end 32B, and from the intermediate part 32C to the distal end. The width (cross-sectional area) may be uniform in the section up to 32B. The width (cross-sectional area) in the section from the base end 32A to the middle part 32C may be larger than the width (cross-sectional area) in the section from the middle part 32C to the tip 32B. Further, although the shape shown in FIG. 4 is two stages, it may be any stage shape of three or more stages.

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 preferably 3 mm or more and 20 mm or less. More preferred. When the length h falls within this range, heat dissipation can be improved. Note that the length h is the distance from the base end 32A to the distal end 32B in the Z direction.
Further, the ratio h/t of the length h to the thickness t is not particularly limited, but is preferably 0.2 or more and 100 or less, more preferably 0.5 or more and 50 or less, and even more preferably 1.5 or more and 25 or less. Further, the ratio h/Dr of the length h to the diameter Dr is not particularly limited, but is preferably 0.2 or more and 100 or less, more preferably 0.5 or more and 30 or less, and even more preferably 1 or more and 20 or less. By setting the ratio h/t and the ratio h/Dr within this range, heat dissipation can be improved.

As shown in FIG. 3, the pitch P is the average distance between the centers of adjacent protrusions 32 when viewed from the Z direction. The average distance between the centers of adjacent protrusions 32 refers to the average value of the distances between each pair of adjacent protrusions 32. The pitch P is not particularly limited, but is preferably 0.7 mm or more and 15 mm or less, more preferably 1 mm or more and 12 mm or less, and even more preferably 2 mm or more and 10 mm or less. By setting the pitch P within this range, heat dissipation can be improved.
Further, the ratio P/h of the pitch P to the length h is not particularly limited, but is preferably 0.014 or more and 15 or less, more preferably 0.03 or more and 6 or less, and even more preferably 0.05 or more and 4 or less. Further, the ratio P/Dr of the pitch P to the diameter Dr is not particularly limited, but is preferably 0.04 or more and 80 or less, more preferably 0.25 or more and 12 or less, and even more preferably 0.6 or more and 3 or less. When the ratio P/h and the ratio P/Dr are within this range, heat dissipation can be improved.

As shown in FIG. 3, one direction perpendicular to the Z direction is the X direction, and a 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 velocity of the cooling medium flowing through the heat radiating member, and the heat radiation characteristics, and is not particularly limited. The protrusions 32 may be arranged in a grid pattern, that is, in such a way that the protrusions 32 are located on each grid arranged in the X direction and the Y direction, or they may be arranged in a direction intersecting the X direction. Alternatively, the protrusions 32 may be arranged in such a way that the protrusions 32 are located only in a part of each grid arranged in the X direction and the Y direction.

Note that it is preferable that the heat dissipation member 10 satisfy 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 protruding portion 30 is larger than the diameter Dt.

(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 just an example, and the heat dissipating member 10 may be manufactured by any method, such as 3D printing, injection molding, or cast molding, depending on the manufacturing amount and the complexity of the shape. selected. Injection molding is preferred, especially when manufacturing large quantities.

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

The ceramic powder is a raw material for the heat dissipation member 10 and contains components contained in the heat dissipation member 10. That is, the ceramic powder includes silicon nitride powder. The 50% particle size D ₅₀ of the silicon nitride powder contained in the ceramic powder 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 0.1 μm or more and 0.8 μm or less. is even more preferable. By setting the particle size within this range, appropriate sintering can be achieved. The 50% particle size D ₅₀ can be measured using a diluted slurry containing a ceramic material using a Horiba LA-950V2 laser diffraction/scattering particle size distribution measuring device.
The content of silicon nitride powder in the entire ceramic powder is preferably 75 mol% or more and 99 mol% or less, more preferably 85 mol% or more and 98 mol% or less, and 90 mol% or more and 98.5 mol% or less. is even more preferable. Thereby, the heat dissipation member 10 containing silicon nitride as a main component can be appropriately manufactured.

Further, the ceramic powder contains a sintering aid. Sintering aids promote sintering. As a sintering aid, Group 2 (alkaline earth metal), Group 3 (rare earth (scandium group)), Group 4 (titanium group), Group 5 (earth metal (vanadium group)), Group 13 Examples include sintering aids containing at least one element selected from the elements of Group 1 (Boron group (earth metals)) and Group 14 (Carbon group). The sintering aid preferably contains at least one of a rare earth oxide (RE ₂ O ₃ ) and magnesium oxide (MgO), and more preferably contains both a rare earth oxide and magnesium oxide. The content of rare earth oxides in the ceramic powder is preferably 0.1 mol% or more and 15 mol% or less, more preferably 0.2 mol% or more and 10 mol% or less, and 0.1 mol% or more and 15 mol% or less, more preferably 0.2 mol% or more and 10 mol% or less. More preferably, the content is .5 mol% or more and 5 mol% or less. The rare earth oxide is selected from at least one of the group consisting of yttrium oxide, neodymium oxide, samarium oxide, samarium oxide, europium oxide, gadolinium oxide, erbium oxide, ytterbium oxide, and lutetium oxide.
The content of magnesium oxide in the ceramic powder is preferably 0.1 mol% or more and 10 mol% or less, more preferably 0.2 mol% or more and 5 mol% or less, and 0.1 mol% or more and 5 mol% or less, based on the entire ceramic powder. It is more preferably 5 mol% or more and 3 mol% or less. Ceramic powders are also treated with silicon oxide, zirconium oxide, It is preferable that the total amount of titanium is 5 mol % or less. By controlling the content of these substances to 5 mol % or less, it is possible to suppress a decrease in volume resistivity. The total content of silicon oxide, zirconium oxide, and titanium oxide is more preferably 3 mol% or less, still more preferably 1 mol% or less. Further, 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, More preferably, it is 0.5 mol% or more and 1 mol% or less.

The resin is a component for molding the ceramic material into a desired shape in the curing process described below, and includes known curable resins. The resin used in this embodiment is required to have shape retention during the curing process, and is capable of forming a three-dimensional network structure through a polymerization reaction. It is preferable that the resin is in a liquid state because it increases the fluidity of the slurry and has good filling properties into a mold.

Additionally, the resin must be easily removed from the ceramic molded body in the degreasing process after the curing process and before sintering. Examples of the resin used in this embodiment include epoxy resin, phenol resin, melamine resin, acrylic acid resin, and urethane resin. Among them, epoxy resins are preferably used because of their good shape retention properties. Examples of the epoxy resin include glycidyl ether type epoxy resins of bisphenols such as bisphenol A type and bisphenol F type, phenol novolak type epoxy resins, cresol novolak type epoxy resins, glycidylamine type epoxy resins, and aliphatic epoxy resins. Examples include ether type epoxy resin, glycidyl ester type epoxy resin, methyl glycidyl ether type epoxy resin, cyclohexene oxide type epoxy resin, rubber-modified epoxy resin, and the like.

The curing agent is for curing the resin, and is selected depending on the resin used. The curing agent is preferably one that is water-soluble and can quickly harden the resin, such as amine-based curing agents, acid anhydride-based curing agents, polyamide-based curing agents, and the like. Amine-based curing agents are preferable because they react quickly, and acid anhydride-based curing agents are preferable because they yield cured products with excellent thermal shock resistance.

Examples of the amine curing agent include aliphatic amines, alicyclic amines, aromatic amines, and any of monoamines, diamines, triamines, and polyamines can be used. Examples of the acid anhydride curing agent include methyltetrahydrophthalic anhydride and dibasic acid polyanhydride.

The solvent adjusts the viscosity of the mixture of raw materials used to form a slurry, thereby facilitating filling of the slurry into the mold. As the solvent, for example, water (H ₂ O), alcohols, and other organic solvents can be used.

The above-mentioned ceramic powder, resin, curing agent, and solvent are mixed to form a slurry. Further, a dispersant or the like is added as necessary. At this time, the mixing may be carried out 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, or revolution. Examples include mixers, in-line mixers, and the like.

As the dispersant to be added as necessary, a pH adjuster, a surfactant, a polymer dispersant, etc. can be appropriately selected and added in order to dissociate the agglomeration of the ceramic material and make it more dispersed. The pH adjuster, surfactant, polymer dispersant, etc. are preferably those that do not adversely affect the gelation of the above-mentioned curable resin.

The viscosity of the slurry may be such that it can be easily filled in the slurry injection process described later. 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. preferable. Considering the handling properties 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 adjusting 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 MCR302 manufactured by Anton Paar. A cone plate can be used as the measurement jig.

Note that air and the like may be drawn in during the mixing in the raw material mixing step, and gas may be included in the resulting slurry. Therefore, if necessary, a defoaming step for removing gas contained in the slurry may be performed before the next step, the slurry injection step.

(Slurry injection process)
Next, a slurry injection step is performed in which the slurry obtained through the raw material mixing step and, if necessary, a defoaming step is injected into a mold (step S12). The mold has a shape that matches the shape of the heat radiating member 10. Here, for the mold, it is preferable to estimate the shrinkage rate of the sintered body under the ceramic composition and firing conditions of this example in advance, and then design the mold by correcting the shrinkage rate.

(Curing process)
Next, a curing process is performed (step S14). The curing step is a step of curing the resin component contained in the slurry injected into the mold to harden the ceramic material into a desired shape. In the curing step, the slurry is cured under desired curing conditions depending on the characteristics of the slurry.

For example, in the case of a room temperature curable slurry, the reaction starts and cures from the moment the resin and curing agent are mixed, so it may be left to stand for a predetermined period of time. Furthermore, in the case of a heat-curable slurry, it is sufficient to heat it to a desired temperature and ensure sufficient curing time.

(Demolding process)
Next, a demolding process is performed (step S16). The demolding process is a process of taking out the cured ceramic material cured in the curing process from the mold.

(drying process)
After the demolding process, a drying process is performed (step S18). The drying step is a step in which water, volatile solvents, etc. are removed from the cured product obtained in the demolding step, and the cured product is dried to form a molded product. In the drying step, drying is performed slowly so as not to cause cracks or the like in the cured product. That is, the cured product is dried while preventing the occurrence of cracks and the like due to shrinkage stress caused by the difference in drying speed between the surface and the inside of the cured product.

The conditions for the drying process are, for example, relatively mild conditions such as 25°C to 50°C, relative humidity 10 to 95%, and 48 hours to 7 days, to remove moisture contained in the cured product over a long period of time. do. The drying step is preferably carried out until the moisture content of the cured product becomes 20% or less based on the absolute dry mass.

(Degreasing process)
Next, a degreasing process is performed (step S20). The degreasing process is a process of removing resin, nonvolatile solvent, etc. from the molded body obtained in the drying process to obtain a degreased body. In the degreasing process, most of the components that inhibit sintering in the next sintering process are removed. If a large amount of components that inhibit sintering remain, pores may occur within the sintered body during sintering, and carbides may be produced as by-products, making it impossible to obtain the desired properties of the final product. There is a risk of

The conditions for the degreasing process include, for example, slowly increasing and holding the temperature from 250°C to 800°C, and taking a relatively long period of time, such as 3 to 14 days, to remove the content from the molded product. Remove resin components, etc. Here, in particular, the degreasing step for silicon nitride is preferably carried out until the amount of residual carbon in the compact becomes 900 ppm or less.

(Firing process)
Next, a firing process is performed (step S22). The firing process is a process of firing the degreased body that has undergone the degreasing process to sinter the ceramic material to obtain the heat dissipating member 10 which is a sintered body. The firing in the firing process is to sinter the ceramic material to form a sintered body, that is, the heat dissipating member 10, and a known firing method may be applied.

In the firing process, in order to improve the thermal conductivity of the sintered body and ensure mechanical properties, the following conditions are met in order to allow sufficient grain growth of silicon nitride crystal particles and to obtain a dense sintered body without pores. It is preferable to bake it with The atmosphere in the furnace is preferably a nitrogen atmosphere with an oxygen concentration of 50 ppm or less and a pressurized atmosphere. The atmospheric pressure in the furnace is preferably in the range of 5 atm to 10 atm. Further, the maximum firing temperature in the firing step is preferably in the range of 1800°C to 1950°C. Further, the firing time is preferably in the range of 8 hours to 72 hours.

(Secondary firing process)
The sintered body obtained in the firing process may be subjected to a secondary firing process in order to obtain a sintered body having desired characteristics. In this secondary firing step, the sintered body obtained in the above-mentioned firing process (first firing) is further subjected to high pressure treatment to densify the structure of the sintered body and remove the grain boundary glass phase. It may be crystallized to further improve the thermal conductivity of the sintered body.

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

(effect)
As explained above, the heat dissipation member 10 according to the present embodiment includes the base portion 20 and the protrusion portion 30 protruding from one surface 20B of the base portion 20, and is made of a member mainly composed of silicon nitride. be. It is preferable that the thickness t of the base portion 20 of the heat dissipating member 10 is 0.6 mm or more and 2.0 mm or less. In the heat dissipation member 10 made of silicon nitride, by setting the thickness of the base portion 20 within this range, the heat dissipation performance can be improved while maintaining the mechanical properties of the heat dissipation member 10.
Furthermore, when mounting the semiconductor chip 12, for example, if the insulating substrate and the heat sink are separated, it becomes necessary to join different materials to join them. In contrast, in this embodiment, the base portion 20 that functions as an insulating substrate and the protrusion portion 30 that functions as a heat sink are integrated, so that the number of joints of different materials is reduced and the expansion coefficient difference between the different materials is reduced. It is possible to suppress the occurrence of thermal stress caused by this and improve mechanical reliability. Moreover, this suppresses the increase in the overall thickness of the semiconductor unit 1, and also makes it possible to achieve a lower back position.
Furthermore, there is an increasing demand for noise reduction associated with switching of power semiconductors, and a simplified structure of heat dissipation members is required. In contrast, the heat dissipation member 10 according to the present embodiment integrates the base portion 20 that functions as an insulating substrate and the protrusion portion 30 that functions as a heat sink. The number of interfacial layers can be reduced as much as possible.

Further, in the protruding portion 30, the diameter Dr of the circumscribed circle of the outer periphery of the proximal end portion 32A on the side of the base portion 20 is larger than the diameter Dt of the circumscribed circle of the outer periphery of the distal end portion 32B on the opposite side from the base portion 20. is preferred. Since the diameter Dr is larger than the diameter Dt, the radiation efficiency of radiation can be increased and heat can be dissipated appropriately.

Further, the ratio Dr/Dt of the diameter Dr to the diameter Dt is preferably 1.1 or more and 100. Thereby, heat can be dissipated more appropriately.

Furthermore, it is preferable that the width of the protrusion 30 decreases from the base end 32A toward the distal end 32B. With such a tapered shape, heat can be dissipated more appropriately.

Moreover, it is preferable that the heat dissipation member 10 further contains magnesium oxide and a rare earth oxide. Thereby, the heat dissipation member 10 is appropriately sintered, and mechanical reliability can be improved.

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

Further, the semiconductor unit 1 according to the present embodiment includes a heat dissipation member 10 and a semiconductor chip 12 provided on the surface 20A side of the heat dissipation member 10. According to the semiconductor unit 1 according to this embodiment, heat from the semiconductor chip 12 can be appropriately released.

(Example)
Next, examples will be described.
<Evaluation of radiative cooling ability based on the shape of heat dissipation member using radiative cooling simulation>
Using optical simulation software (manufactured by Eclat Digital Research: Ocean), the protrusions of the heat dissipation member are fixed at Dr: 3 mm, h/Dr: 3, and the arrangement is also fixed, and the shape of the protrusions is changed. The amount of radiant heat was calculated. That is, light was emitted from the radiator having the protruding body using Lambertian approximation, and the amount of energy that reached the integrating sphere was integrated to estimate the total amount of light emitted. The results are shown in Table 1, where the radiant heat ratio for each shape is set as 1 for the case of a prismatic shape. When Dr/Dt exceeded 1.1, the radiant heat ratio was approximately 1.6 times.
Table 2 is a table showing the evaluation results for the manufacturing conditions of the heat dissipating member and the composition constituting the member in each example, and Tables 3 and 4 are tables showing 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.

(Example 1)
In Example 1, a heat dissipation member was manufactured using composition C1. That is, in Example 1, silicon nitride powder (manufactured by Denka: SN-9FWS), magnesium oxide and yttrium oxide as sintering aids, ethanol as a solvent, polycarboxylic acid as a dispersant, and resin An epoxy resin as a compound and triethylenetetramine as a curing agent were mixed to form a slurry. The blending ratio of silicon nitride and sintering aid was as shown in Table 2.
The obtained slurry was poured into a mold and held at 50° C. for 5 hours to cure the slurry and obtain a cured product. Then, the cured product was removed from the mold, humidified and dried at 30°C for 4 days, and then dried with hot air at 50°C to obtain a dry molded product. The dried molded body was then heated at 600° C. for 3 hours to degrease it to obtain a molded body.
The obtained 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 rate of the fired body (dried molded body, molded body) under each firing condition in advance and correcting the shrinkage rate. In the obtained molded body, the size of the base part was 50 mm x 50 mm, and 120 protrusions were arranged in a checkered pattern (checkered flag) within the base part of 38 mm x 38 mm.

The thermal conductivity, volume resistance, and three-point bending strength of the heat dissipation member of Example 1 were measured. For each measurement method, the method described in the above embodiment was used. Each measurement sample was made from a reference sample of 60 x 60 x 6 mm, which was manufactured under the same conditions as the heat dissipation member of Example 1 (fired at the same time) without directly processing the heat dissipation member of Example 1, and was made to the size of each measurement condition. A processed sample was used. Table 2 shows the results of each measurement.

As shown in Table 3, in the heat dissipation member of Example 1, the base portion 20 and the protruding portion 30 are integrally formed, as described in the above embodiment, and the thickness t of the base portion 20 is 2. .3 mm, the diameter Dr was larger than the diameter Dt, and the ratio Dr/Dt was 3. Further, the size of the base part was approximately 50 mm x 50 mm. Note that the thickness t of the base portion 20 was adjusted using a surface grinder while maintaining the flatness of the heat dissipation member after firing in order to bond it to a copper plate for evaluation of heat dissipation characteristics described later. After that, a silicone rubber heater with an output of 20 W imitating a semiconductor chip, a copper plate (size 100 mm x 100 mm, thickness 5 mm), and a heat dissipation member were each made using Shin-Etsu Chemical's heat dissipation silicone oil compound G-777 (thermal conductivity: 3. 3 W/m·K) was applied uniformly using a squeegee, and the silicon rubber heater was placed on the lower side, and the protrusions were left standing for 20 minutes using a 5 kg cast iron weight to join. That is, the number of dissimilar material interface layers is two.

(Example 2 to Example 4)
In Examples 2 to 4, heat dissipation members were manufactured in the same manner as in Example 1 except that compositions C2 to C4 were used and the composition of the ceramic material and firing conditions were changed as shown in Table 2. The measurement sample was processed from the reference sample in the same manner as in Example 1. In Examples 2 to 4 as well, the base portion 20 and the protruding portion 30 are integrally formed, and the thickness t of the base portion 20 is 1.1, 1.6, and 2.0, respectively, as shown in Table 3. 3 mm, and the ratio Dr/Dt was 3. Further, in the same manner as in Example 1, a silicon rubber heater, a copper plate, and a heat radiation member were joined. The number of interfacial layers of different materials is two.

(Example 5)
In Example 5, a heat radiating member was manufactured in the same manner as in Example 1 except that the thickness t of the base portion 20 was 0.4 mm. The measurement sample was processed from the reference sample in the same manner as in Example 1. When the silicone rubber heater, the copper plate, and the heat dissipation member were bonded together and allowed to stand for 20 minutes using a 5 kg cast iron weight, cracks occurred in the base and the heat dissipation characteristics could not be evaluated.

(Example 6)
In Example 6, composition C1 was used, but only the part corresponding to the base was manufactured by sintering composition C1, and a plate-shaped sample of size 50 mm x 50 mm and thickness 1 mm was manufactured in this way. It was made part of the platform. Next, a heat dissipating member made of Al (aluminum) with approximately the same arrangement and surface area of protrusions as in Example 1 was separately prepared. The thickness of a portion of the base portion 20 made of Al was 3 mm, and the ratio Dr/Dt was 1 (the diameter Dr is the same as the diameter Dt). Further, in the same manner as in Example 1, a silicon rubber heater, copper plate 1, a sintered plate-shaped sample of C1, and an Al heat dissipation member were joined. The sintered plate-shaped sample of C1 and the Al heat dissipation member were joined using a heat dissipation silicone oil compound. Therefore, the total thickness of the base portion 20 is approximately 4 mm, ignoring the bonding thickness due to the silicone oil compound for heat dissipation, and the number of interfacial layers of different materials is three.

(Example 7)
In Example 7, the structure was similar to Example 6 except that only a portion corresponding to a part of the base portion was formed of composition C5 (AlN). In other words, the number of interfacial layers of different materials is three.

(Example 8)
In Example 8, a copper plate 2 with a size of 50 x 50 mm and a thickness of 1 mm was added between the AlN and Al heat dissipation members of the configuration of Example 7, imitating the conventional DCB board (Direct Copper Bonding). Then, from the top, a silicon rubber heater, a copper plate 1, an AlN plate, a copper plate 2, and an Al heat dissipation member were installed. The AlN and the copper plate 2 and the copper plate 2 and the Al heat dissipation member were bonded using a heat dissipation silicone oil compound. In other words, the number of interfacial layers of different materials is four.

(Example 9)
Example 9 was constructed in the same manner as Example 6, except that only a portion corresponding to a part of the base was formed of composition C6 (Al ₂ O ₃ ). In other words, the number of interfacial layers of different materials is three.

(Example 10)
In Example 10, a heat radiating 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 is two.

(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 is two.

(Example 12)
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 is two.

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

<Number of interfacial layers of different materials>
As is clear from Tables 3 and 4, the number of interfacial layers of different materials in Examples 1 to 5 and 10 to 13 is two, and the structure of the heat dissipation member can be simplified. In addition, the number of dissimilar material interface layers in Examples 1 to 5 and 10 to 13 is two, and a noise reduction effect can be expected by significantly reducing the number of dissimilar material interface layers compared to Example 8, which has a conventional configuration. . Further, from Tables 2 to 4, the samples of Examples 1 to 5 and 10 to 13 had a volume resistivity higher than 1.0×10 ¹⁴ Ω·cm and functioned well as an insulating substrate. Furthermore, in heat cycle tests, it is possible to reduce stress caused by differences in thermal expansion between different materials, so reliability can be expected to improve.
<Mechanical properties>
The mechanical properties were determined by applying a silicone oil compound for heat dissipation between the interfaces of dissimilar materials as described above, and when joining, a 5 kg cast iron weight was applied to the protruding part, and cracks occurred in the heat dissipation member after leaving it for 20 minutes. The cases are shown in Tables 3 and 4 with × as the case and ○ as the case where no occurrence occurred. As described above, Example 5 in which the thickness of the base portion 20 is less than 0.5 mm has low reliability in terms of mechanical properties.
<Heat dissipation evaluation>
The heat dissipation properties of the heat dissipation members of each example were evaluated. Heat dissipation was evaluated by the method shown below. A stainless steel water tank with an internal dimension of 70 mm x 70 mm and a depth of 20 mm with a cooling water port provided on the opposite side is prepared, and the copper plate 1 (size 100 mm x 100 mm, thickness 5 mm) is connected to the copper plate 1 through an O-ring for heat dissipation. Fasten and seal the stainless steel tank so that the parts fit into the stainless steel tank. The cooling water port is connected to the cooling water circulation system SOC1-1100 manufactured by As One Corporation, and the cooling water temperature is set at 25°C, and the circulating cooling water is introduced into the water tank. A DC stabilized power supply PSW-360M160 made by TEXIO is connected to the attached silicone rubber heater, and 20W of power is applied to it, and the temperature T _H directly above the silicone rubber heater and the temperature T _L at the center of the bottom surface of the heat dissipation member base are adjusted. is measured using a thermocouple. In this experimental system, it took about 30 minutes to 1 hour for T _H and T _L to reach the saturation temperature, and the average temperature over 1 hour to 2 hours was used for evaluation. The heat dissipation property was evaluated by the thermal resistance R expressed by the following formula (1) using the input power Q (20 W in this experiment), and the relative values when Example 7 is set as 1.0 are shown in Table 3 and It is shown in Table 4. The lower the thermal resistance, the higher the cooling performance as a heat dissipation member.

R = (T _H - T _L )/Q (Unit: °C/W) ... (1)

As shown in Tables 2 to 4, the base portion 20 and the protruding portion 30 are integrally formed with silicon nitride as a main component, and the thickness of the base portion 20 is 0.5 mm or more and 5.0 mm or less. It can be seen that Examples 1 to 2 and 11 to 13, in which the diameter Dr is larger than the diameter Dt and the thermal conductivity exceeds 60 W/m·K, have better heat dissipation than Example 8, which has a conventional configuration. On the other hand, in Examples 3 and 4, the thermal conductivity is less than 60 W/m・K, but because the number of interfacial layers of different materials is two, the heat dissipation performance is not significantly reduced and the heat dissipation is at an appropriate level. It can be seen that the gender is guaranteed. Examples 7 and 8 show that heat dissipation performance decreases as the number of dissimilar material interface layers increases by one. In Example 9, the thermal conductivity of the base was low and the number of interfacial layers of different materials was large, resulting in low heat dissipation. Moreover, from Examples 1, 10, and 12, it was revealed that even though the same composition C1 was used, Example 1 with a larger ratio Dr/Dt had better heat dissipation. By setting the ratio Dr/Dt to 1.1 or more, it is possible to improve the yield when demolding the slurry cured body during production, which is preferable.

Although the embodiments and examples of the present invention have been described above, the embodiments are not limited to the contents of the embodiments and examples. Furthermore, the above-mentioned components include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those that are in a so-called equivalent range. Furthermore, the aforementioned components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the constituent elements can be made without departing from the gist of the embodiments described above.

1 Semiconductor unit 10 Heat dissipation member 12 Semiconductor chip 20 Base part 30 Projection part 32 Projection body 32A Base end part 32B Tip part

Claims

A heat dissipating member mainly composed of silicon nitride,
including a base part and a protrusion part protruding from one surface of the base part,
The thickness of the base portion is 0.5 mm or more and 5.0 mm or less,
Heat dissipation member.
2. The protrusion according to claim 1, wherein a diameter Dr of a circumscribed circle of an outer periphery of a proximal end portion on the side of the base portion is larger than a diameter Dt of a circumscribed circle of an outer periphery of a distal end portion on the opposite side of the base portion. The heat dissipation member described.
A heat dissipating member mainly composed of silicon nitride,
including a base part and a protrusion part protruding from one surface of the base part,
The protruding portion has a diameter Dr of a circumscribed circle around the outer periphery of the proximal end portion on the side of the base portion, which is larger than a diameter Dt of the circumscribed circle around the outer periphery of the distal end portion on the side opposite to the base portion.
Heat dissipation member.
The heat dissipation member according to claim 2 or 3, wherein the ratio of the diameter Dr to the diameter Dt is 1.1 or more and 100 or less.
The heat dissipation member according to any one of claims 2 to 4, wherein the protrusion has a width that decreases from the base end toward the distal end.
The heat dissipation member according to any one of claims 1 to 5, wherein the heat dissipation member whose main component is silicon nitride is a silicon nitride sintered body.
The heat dissipation member according to any one of claims 1 to 6, further comprising magnesium oxide and a rare earth oxide.
Any one of claims 1 to 7, wherein the volume resistivity at room temperature is higher than 1.0 x 10 14 Ω·cm, the thermal conductivity is 60 W/m·K or more, and the three-point bending strength is 600 MPa or more. The heat dissipation member according to item 1.
comprising the heat dissipation member according to any one of claims 1 to 8 and a semiconductor chip provided on the other surface side;
semiconductor unit.