JP2021168376A - Method of manufacturing heat dissipation substrate and method of manufacturing composite substrate - Google Patents

Abstract

To provide a method of manufacturing a heat dissipation substrate, capable of increasing a heat conductive rate reduced by a thin wall treatment during the manufacturing process, and provide a method of manufacturing a composite substrate.SOLUTION: A method of manufacturing a heat dissipation substrate of the present disclosure includes the steps for: preparing a composite material containing diamond and a metal; applying a thin wall treatment to the surface of the composite material to form a processed face on the composite material; and heating the composite material by pulse conductive sintering in a state where a pressure less than 50 MPa is applied to the composite material.SELECTED DRAWING: Figure 3A

Description

The present disclosure relates to a method for manufacturing a heat radiating substrate containing diamond particles and a metal, and a method for manufacturing a composite substrate.

As the light output of a semiconductor light emitting element increases, heat dissipation of the semiconductor element has become an important issue. Heat dissipation of semiconductor elements is one of the important issues not only in semiconductor light emitting elements but also in semiconductor integrated circuit elements that execute arithmetic processing at high speed and monolithic microwave integrated circuit elements that oscillate microwaves.

In order to dissipate heat from the semiconductor element that generates heat during operation in this way, development of a heat radiating member such as a heat radiating substrate that dissipates the heat of the semiconductor element is underway. The heat radiating member is required to have high thermal conductivity. As a promising material for heat-dissipating substrates, the development of composite materials containing diamond and metal is underway. This composite material has a structure in which diamond particles having a higher thermal conductivity than that of a metal are dispersed in a metal such as copper (Cu).

Patent Document 1 discloses an example of a composite material in which diamond particles are dispersed in Cu. Patent Document 2 discloses a method of coating diamond particles with a metal layer and then sintering them with Cu powder to prepare a composite material. Patent Document 3 discloses a heat-dissipating substrate in which a plated metal layer is formed on a composite material in which diamond particles are dispersed in Cu.

Special Table 2019-502251 Japanese Unexamined Patent Publication No. 2008-248324 International Publication No. 2016/056637

The present disclosure provides a method for manufacturing a heat-dissipating substrate and a method for manufacturing a composite substrate, which can increase the thermal conductivity lowered by the thinning treatment during the manufacturing process.

In one aspect, the method for manufacturing a heat-dissipating substrate of the present disclosure includes a step of preparing a composite material containing diamond and a metal, and a step of thinning the surface of the composite material to form a processed surface on the composite material. A step of heating the composite material in a state where a pressure of less than 50 MPa is applied to the composite material by pulse energization sintering is included.

In one aspect of the method for manufacturing a composite substrate of the present disclosure, a pressure of less than 50 MPa is applied to the composite material by a step of preparing a composite material containing diamond and a metal which has been subjected to a thinning treatment and pulse energization sintering. This includes a step of heating the composite material in a state of being heated.

According to the embodiment of the present disclosure, it is possible to increase the thermal conductivity reduced by the thinning treatment during the manufacturing process by pulse energization sintering.

FIG. 1 is a graph in which the coefficient of linear expansion and thermal conductivity are plotted for materials such as diamond and Cu. FIG. 2 is a perspective view schematically showing an example of the diamond particles 10. FIG. 3A is a flowchart showing a main process in the method for manufacturing a heat radiating substrate according to the embodiment of the present disclosure. FIG. 3B is a flowchart showing the main steps in the method for producing a Cu-diamond composite material according to the embodiment of the present disclosure. FIG. 4 is a photograph showing an example of diamond particles contained in the mixed powder according to the embodiment of the present disclosure. FIG. 5 is a schematic view showing a configuration example of a sintering apparatus used in the pulse energization sintering method according to the embodiment of the present disclosure. FIG. 6 is a diagram schematically showing an example of the relationship between the passage of time from the start to the end of the pulse energization sintering step and the temperature and pressure of the mixed powder. FIG. 7A is a diagram schematically showing another example of the relationship between the passage of time from the start to the end of the pulse energization sintering step and the temperature and pressure of the mixed powder. FIG. 7B is a diagram schematically showing another example of the relationship between the passage of time from the start to the end of the pulse energization sintering step and the temperature and pressure of the mixed powder. FIG. 8 is a perspective view schematically showing the outer shape of the composite material produced according to the embodiment of the present disclosure. FIG. 9 is an enlarged sectional view schematically showing a part of the composite material produced by the embodiment of the present disclosure. FIG. 10 is an enlarged sectional view schematically showing a part of the composite material subjected to the thinning treatment in the embodiment of the present disclosure. FIG. 11 is a cross-sectional view schematically showing an enlarged part of a composite material which has been sequentially subjected to thinning treatment and pulse energization sintering in the embodiment of the present disclosure. FIG. 12 is an enlarged sectional view schematically showing a part of the composite material on which the metal layer is formed in the embodiment of the present disclosure. FIG. 13 is a diagram showing a micrograph of a cross section of a part of the composite material in the experimental example. FIG. 14 is a diagram showing a micrograph of a cross section of a part of the composite material in another experimental example. FIG. 15 is a perspective view showing an application example of the composite material.

Before explaining the embodiments of the present disclosure, the findings found by the present inventor and the technical background thereof will be described.

FIG. 1 is a graph in which the coefficient of linear expansion and thermal conductivity are plotted for materials such as diamond and Cu. The horizontal axis of the graph is the coefficient of linear expansion, and the vertical axis is the thermal conductivity. The coefficient of linear expansion is the coefficient of linear expansion per unit length, and the unit is [ ^10-6 / K]. The unit of thermal conductivity is [W / mK (Watt per meter Kelvin)].

Single crystal diamonds have the highest level of thermal conductivity of any material, ideally at extremely high values in excess of 2000 [W / mK]. The thermal conductivity of polycrystalline diamond particles is, for example, about 900 to 1800 [W / mK]. The thermal conductivity of diamond particles produced by a CVD method or the like is, for example, about 900 to 1800 [W / mK].

FIG. 2 is a perspective view schematically showing an example of the diamond particles 10. The diamond particle 10 in the example of FIG. 2 has, for example, the shape of a polyhedron having hexagonal and quadrangular faces (facets) on its surface. In the actual diamond particle, other polygonal surfaces appear on the surface or a part of the diamond particle is missing, so that the diamond particle can have a more complicated and diverse shape. The thermal conductivity of individual diamond particles can have different values depending on the presence of crystal defects or impurities present on or inside the surface or inside.

On the other hand, the thermal conductivity of Cu, which is a metal, is about 400 [W / mK], and the thermal conductivity of Ag is about 420 [W / mK]. Therefore, the thermal conductivity of the composite material in which the diamond particles are dispersed in a metal such as Cu shows an intermediate value between the thermal conductivity of the metal and the thermal conductivity of the diamond particles. The higher the volume ratio of diamond particles contained in the composite material, the higher the theoretical value of thermal conductivity of the composite material. However, in reality, the thermal conductivity of the composite material is not simply determined only by the volume ratio of diamond, and it is considered that the state of the interface between Cu and diamond particles also has an effect. The interface between Cu and diamond can fluctuate due to defects, damage, etc. that may occur in the diamond particles during the manufacturing process.

When a semiconductor element is used by being bonded to a heat radiating substrate, if the difference in linear expansion coefficient existing between the member in contact with the heat radiating substrate on the semiconductor element side and the heat radiating substrate is large, problems such as peeling may occur. Therefore, it is desirable that the coefficient of linear expansion of the composite material used for the heat radiating substrate is close to the coefficient of linear expansion of the member to be joined.

The composite material containing diamond particles and Cu has a higher thermal conductivity than Cu and has excellent properties close to the coefficient of linear expansion of a semiconductor. A composite material using a metal as a matrix is sometimes called a metal matrix composite (MMC). Therefore, the composite material in which diamond particles are dispersed in Cu may be referred to as "Cu-diamond MMC" in the present specification. Further, it may be simply referred to as "Cu diamond composite material" or "composite material". The metal that becomes the matrix of MMC is not limited to Cu, but Ag, Al, and the like can also be taken.

When the heat radiating substrate is bonded to the semiconductor element, it is preferable that the thickness can be adjusted as needed. However, when the present inventor performed a polishing process on the Cu-diamond MMC, the thermal conductivity of the polished Cu-diamond MMC was lower than the thermal conductivity of the Cu-diamond MMC before the polishing process. It was. It is considered that the thermal conductivity was lowered because the adhesion between the diamond and Cu in the Cu-diamond MMC was lowered by performing the polishing process.

Further, the present inventor performed polishing on the Cu-diamond composite material thus produced to damage the Cu-diamond composite material, and then performed low-temperature / low-pressure pulse energization sintering, which resulted in a decrease after the polishing process. It has been found that the thermal conductivity can be increased. In the polishing process, the surface of the Cu-diamond composite is scraped. Therefore, all or a part of the diamond particles existing near the surface of the composite material, together with the surrounding Cu, is scraped or dropped from the composite material. The removal of diamond particles from the Cu-diamond composite by polishing is called "threshing". When such shedding occurs, the smoothness of the surface of the Cu-diamond composite material is impaired. In this way, the processed surface formed on the surface of the composite material by the polishing process, that is, the polished surface is not smooth, and irregularities having a size equal to the size of the diamond particles may exist on the processed surface. Further, due to the stress applied to the diamond particles remaining in the composite material during polishing by such a polishing step, a gap may be formed at the interface between Cu and the diamond particles. As a result, the thermal conductivity of the composite material after the polishing step is lower than the thermal conductivity of the composite material before the polishing step. However, it was found that the thermal conductivity of the composite material after polishing was increased by performing pulse current sintering, which will be described later. It is considered that this is because the gap between the diamond particles and the Cu interface is repaired. Hereinafter, the pulse energization sintering performed after such a polishing step may be referred to as "repulse energization sintering" to distinguish it from the pulse energization sintering which is an example of the method for producing a composite material.

The method for manufacturing the heat radiating substrate of the present disclosure has been completed based on the above new findings. Hereinafter, embodiments of the method for manufacturing a heat radiating substrate in the present disclosure will be described. The heat dissipation substrate is an example of the composite substrate of the present disclosure.

<Embodiment>
FIG. 3A is a flowchart showing a main process in the method for manufacturing a heat radiating substrate according to the embodiment of the present disclosure. As shown in FIG. 3A, the method for manufacturing a heat radiating substrate in the present embodiment includes a step S100 of preparing a composite material containing diamond and copper, and a thinning treatment on the surface of the composite material to form a processed surface on the composite material. The step S200 of forming and the step S300 of heating the composite material in a state where a pressure of less than 50 MPa is applied to the composite material by pulse energization sintering are included.

Hereinafter, the case where the metal used for the composite material is Cu will be described. As the metal other than Cu, for example, Al or silver Ag can be used. The thermal conductivity of the metal is preferably 200 [W / mK] or more. Since the thermal conductivity of Al is about 240 [W / mK] and the thermal conductivity of Ag is about 420 [W / mK], high thermal conductivity is maintained even if a composite material with diamond is formed. can do.

First, the step S100 for preparing the composite material in the present embodiment will be described. FIG. 3B is a flowchart showing a specific example of the step S100 for preparing the composite material according to the present embodiment. As described above, the cause of the decrease in thermal conductivity of the composite material is considered to be the polishing process. Therefore, the effect of the embodiments of the present disclosure does not depend on the method of producing the composite material to be prepared. That is, in this embodiment, various composite materials produced by known methods can be used, and for example, commercially available composite materials may be used. Examples of the method for producing the composite material include a sintering method and a melting method. A preferred method for producing the composite material is a pulse current sintering method. With this method, as will be described later, a composite material can be obtained under relatively low temperature conditions as compared with the conventional method.

Hereinafter, a method for producing a composite material by a pulse energization sintering method will be described with reference to FIG. 3B. As shown in FIG. 3B, this step S100 includes a step S10 of preparing a mixed powder of diamond particles and Cu powder particles, and a pulse energization sintering method in which a pressure is applied to the mixed powder at 500 ° C. or higher and 800 ° C. or higher. It includes a step S20 of producing a composite material containing diamond and Cu from the mixed powder while keeping the temperature below ° C. This "temperature" is a "temperature" that is directly or indirectly measured by a temperature measuring device such as a radiation thermometer or a thermocouple. The “temperature” in the present disclosure is a measured value of the temperature in the die 30 of the SPS apparatus as shown in FIG. 5 described later. The sintering peak temperature Ts, which will be described later, means a temperature that is maintained at a predetermined pressure for a total of 1 minute or more among the temperatures of the die 30 measured by a radiation thermometer or a thermocouple. For example, in the case of FIG. 6, the temperature held at the highest temperature in the sintering step is called the sintering peak temperature Ts, and is distinguished from the temperature that changes transiently during the temperature rise and fall.

FIG. 4 is a photograph showing an example of diamond particles contained in the mixed powder of step S10. In certain embodiments, the average particle size of the diamond particles is 40 μm or more and 500 μm or less. The particle size distribution of the diamond particles does not have to be a single peak type with a single peak, and may have a plurality of peaks. By setting the average particle size of the diamond particles to 40 μm or more, it is possible to increase the thermal conductivity while inexpensively producing Cu-diamond MMC. By setting the average particle size of the diamond particles to 500 μm or less, the manufacturing cost of the diamond particles themselves can be reduced. Further, the particle size distribution of the diamond particles is preferably 200 μm or more and 400 μm or less. Within this range, the thermal conductivity can be further improved. In certain embodiments, the diamond particles in the mixed powder may include particles having an average particle size of 200 μm or more and 400 μm or less and particles having an average particle size of 40 μm or more and 80 μm or less. In the present specification, particles having an average particle size of 200 μm or more and 400 μm or less are referred to as “large particles”, and particles having an average particle size of 40 μm or more and 80 μm or less are referred to as “small particles”. Since particles having a relatively small average particle size can be arranged so as to fill the gaps formed by particles having a relatively large average particle size, it is possible to increase the filling amount of diamond having a higher thermal conductivity than Cu. .. Thereby, the thermal conductivity of Cu-diamond MMC can be further improved. A mixed powder having such a bimodal particle size distribution is referred to herein as a "bimodal mixed powder". In the bimodal mixed powder, the ratio of particles having an average particle size of 200 μm or more and 400 μm or less to the entire diamond particles is preferably 50% or more in terms of mass ratio. This is because the larger the average particle size, the smaller the total surface area of the diamond particles, and the smaller the contribution of thermal resistance at the interface between the diamond particles and Cu.

The average particle size of Cu powder particles is, for example, 3 μm or more and 10 μm or less. The Cu powder may contain Cu fine powder having a particle size of 1 μm or less, which may be generated by pulverization or the like. Cu powder particles may contain unavoidable impurities. However, impurities such as oxygen and nitrogen cause a decrease in thermal conductivity, so it is desirable to remove them as much as possible. The content of impurities in the Cu powder particles is preferably 2% by mass or less. As such Cu powder particles, those produced by a known production method may be used. Alternatively, commercially available Cu powder particles may be used.

The "average particle size" in the present disclosure means the "median diameter" in the particle size distribution measured by the laser diffraction type particle size distribution measuring device.

In the embodiments of the present disclosure, no metal other than Cu powder particles is intentionally added in order to improve the wettability. Conventionally, since Cu and diamond have poor wettability, it has been considered necessary to improve the wettability with an additive metal, but in the embodiment of the present disclosure, such an additive metal is unnecessary. By intentionally not adding a metal other than Cu powder particles, sintering inhibition can be reduced. In certain embodiments, the amount of the metal other than Cu added in the mixed powder is 1% or less in terms of mass ratio.

Further, as described above, individual diamond particles may be coated with a metal layer such as copper for the purpose of enhancing the adhesion between the diamond particles and the Cu powder particles. However, in the embodiment of the present disclosure, diamonds are used. Do not coat the particles with a metal layer. This is because by not pre-coating the diamond particles with a metal layer such as Cu, the sintering activity can be enhanced as compared with the case where the diamond particles are pre-coated with a metal layer such as Cu. If the diamond particles are coated with a metal layer such as Cu in advance, the sintering activity is lowered, and firing at a high temperature is required as in the case of adding a metal.

In the present embodiment, the mass ratio of Cu powder particles in the mixed powder is preferably 60% or more and 85% or less, and the mass ratio of diamond particles in the mixed powder is preferably 15% or more and 40% or less, for example. In other words, the mass ratio of Cu powder particles to diamond particles is selected in the range of 60:40 to 85:15, for example 80:20. As the mass ratio of diamond particles increases, the thermal conductivity of the composite increases. By setting the mass ratio of the Cu powder particles to 60% or more and 85% or less, a sufficient amount of copper is arranged around the diamond, and gaps that hinder heat conduction are less likely to occur in the Cu-diamond MMC. In other words, if the mass ratio of the Cu powder particles is in the above range, the Cu can have a volume sufficient to be arranged around the diamond, so that it is easy to effectively fill the gaps between the diamond particles. Further, if the amount of Cu is too large, the thermal conductivity of Cu is lower than the thermal conductivity of diamond, so that the thermal conductivity of Cu-diamond MMC may decrease, but within the above range, the thermal conductivity is high. Cu-diamond MMC having the above can be produced. Further, as described later, according to the experiment of the present inventor, even if the mass ratio of the diamond particles is the same, the bimodal mixed powder is more likely to realize a higher thermal conductivity.

The pulsed energization sintering method in step S20 can be performed using, for example, a sintering apparatus 100 as shown in FIG. The pulse energization sintering method is sometimes referred to as a discharge plasma sintering method (spark plasma sintering: SPS) method. Therefore, the sintering apparatus 100 of FIG. 5 may be referred to as an “SPS apparatus”. The sintering device 100 of FIG. 5 includes a die 30 having a through hole forming the cavity 20, and an upper punch 40 and a lower punch 50 that can move up and down relatively along the through hole of the die 30. The sintering device 100 in this example can perform sintering using self-heating under vertical uniaxial pressurization. The upper punch 40 is electrically connected to the first electrode 51, and the lower punch 50 is electrically connected to the second electrode 52. The first electrode 51 and the second electrode 52 are electrically connected to the power supply unit 60.

The die 30 can be formed from a material having excellent heat resistance, for example, graphite. The upper punch 40 and the lower punch 50 can be formed from a conductive and heat resistant material such as graphite. In the thermal conductivity measurement, the flatter the sample, the more reliable the thermal diffusivity can be measured. Therefore, when it is difficult to ensure the flatness of the sintered body to be produced, a hard material is inserted between the upper punch 40 and the sample and between the lower punch 50 and the sample, and the sintered body having a flat surface is inserted. It is preferable to obtain. The hard material is preferably a cemented carbide, for example, tungsten carbide (WC) or titanium carbide (TiC). Further, the material of the upper punch 40 and the lower punch 50 may be changed to the material. The cavity 20 is a space defined by the inner wall surface of the through hole of the die 30, the lower end surface of the upper punch 40, and the upper end surface of the lower punch 50. The above-mentioned mixed powder is loaded inside the cavity 20. By moving at least one of the upper punch 40 and the lower punch 50 in the vertical direction, the distance between the upper punch 40 and the lower punch 50 is reduced, and pressure is applied to the mixed powder in the cavity 20. The upper punch 40 and the lower punch 50 are driven by, for example, a hydraulic device (not shown). The pressure applied to the mixed powder in the cavity 20 can be arbitrarily adjusted in the range of, for example, 5 MPa or more and 100 MPa or less.

In the pulse energization sintering method, pulse energization is performed between the upper punch 40 and the lower punch 50 while applying pressure to the mixed powder by the sintering apparatus 100. The pulse energization is performed by repeatedly passing a direct current pulse current from the power supply unit 60 between the first electrode 51 and the second electrode 52. Since the Cu powder particles are in contact with each other in the mixed powder pressurized by the upper punch 40 and the lower punch 50, a number of local current paths are formed in the mixed powder, and a current flows. By such pulse energization, Joule heat is generated, and the temperature of the mixed powder rises to a predetermined sintering temperature.

FIG. 6 is a diagram schematically showing an example of how the temperature and pressure of the mixed powder change with the passage of time from the start to the end of the pulse energization sintering step. The temperature is indicated by the alternate long and short dash line, and the pressure is indicated by the solid line. The horizontal axis shows time, the left vertical axis shows temperature, and the right vertical axis shows pressure. Due to the movement of the upper punch 40 and / or the lower punch 50, the pressure reaches the sintering pressure Ps in, for example, a few seconds, and the sintering pressure Ps is maintained, for example, for 60 to 1800 seconds. Upon initiation of pulse energization, the temperature of the mixed powder rises at a rate of, for example, 10 to 150 [° C./min] or higher. After reaching a predetermined sintering peak temperature Ts, the sintering peak temperature Ts is maintained within ± 5 ° C. of the target temperature by adjusting the voltage application condition of pulse energization. The control of the sintering temperature can be performed by the feedback of the measurement by the temperature measuring device attached to the die 30 of FIG.

After a predetermined sintering time elapses and a composite material is produced from the mixed powder, the pulse energization is stopped and the temperature is lowered. Further, the movement of the upper punch 40 and / or the lower punch 50 stops the application of pressure to the composite material. After the temperature of the composite has dropped sufficiently to, for example, 50 ° C. or lower, the composite is removed from the die 30.

In FIG. 6, the temperature and pressure are shown to rise and maintain linearly over time, for the sake of clarity. Actual temperature and pressure transitions can include slight overshoots, curvilinear changes, small vibrations, and so on.

In the present embodiment, the voltage for maintaining the sintering temperature is adjusted in the range of 1.0 V or more and 3.0 V or less, and the pulse current is adjusted in the range of 400 A or more and 800 A or less. The duty ratio of the pulse current is, for example, 10 to 80%, and the pulse width is, for example, 1 to 500 milliseconds. After holding at a predetermined sintering peak temperature Ts for a predetermined time, pulse energization is stopped. These values vary depending on various conditions such as the weight of the mixed powder, the sintering temperature, and the punch material, and are not limited to the above range and can be changed as appropriate.

When the sintering temperature is set to, for example, 600 ° C., the time from room temperature to the sintering temperature is, for example, about several minutes to 20 minutes. The cavity 20 is located in a decompression chamber (not shown). The atmospheric pressure in the decompression chamber is, for example, 100 Pa or less. In this way, it is possible to prevent the powder particles from being oxidized or nitrided during the sintering process by pulse energization.

As described above, the sintering peak temperature Ts in the embodiment according to the present disclosure is 500 ° C. or higher and lower than 800 ° C. Within this range, Cu-diamond MMC having excellent thermal conductivity can be produced. The preferred sintering peak temperature Ts is 500 ° C. or higher and 750 ° C. or lower. More preferably, it is 550 ° C. or higher and 700 ° C. or lower. Particularly preferably, it is 600 ° C. or higher and 700 ° C. or lower. Within the above range, Cu-diamond MMC having even better thermal conductivity can be obtained. The range of the sintering time also depends on the sintering peak temperature Ts, and is, for example, in the range of 1 minute or more and 30 minutes or less. When the sintering peak temperature Ts is, for example, 550 ° C. or higher and 650 ° C. or lower, the sintering time can be 5 minutes or more and 20 minutes or less, for example, about 10 minutes.

The pressure applied to the mixed powder at the above sintering peak temperature Ts is 5 MPa or more and 100 MPa or less when held at a constant pressure. By setting the applied pressure to 5 MPa or more and 100 MPa or less, a Cu-diamond MMC having excellent thermal conductivity can be produced. The preferred pressure range is 10 MPa or more and 90 MPa. A more preferable pressure range is 20 MPa or more and 90 MPa or less. More preferably, it is 25 MPa or more and 75 MPa or less. Particularly preferably, it is 25 MPa or more and 50 MPa or less. Within these pressure ranges, Cu-diamond MMC having excellent thermal conductivity can be produced. As described above, applying a constant pressure at the sintering peak temperature Ts is referred to as "continuous pressurization" in the present specification.

Although the case of continuous pressurization has been described so far, the pressure does not have to be constant at all times. The applied pressure may be increased or decreased stepwise or continuously according to the progress of sintering. Further, the first pressure and the second pressure higher than the first pressure may be repeatedly applied to the mixed powder while performing pulse energization. Such a form of pressurization will be referred to as "cycle pressurization". In the cycle pressurization, a Cu-diamond MMC having a high thermal conductivity can be produced by repeatedly applying a first pressure and a second pressure higher than the first pressure. This is considered to be due to, for example, the mechanism described below.

There is a difference in the absolute value between the first pressure and the second pressure. When these pressures are repeatedly applied, there is a step of applying the first pressure after applying the second pressure. At this time, since a relatively high pressure is applied to a relatively low pressure, the diamond particles when the first pressure is applied are compared with those when the second pressure is applied. Increases the degree of freedom within the die. Therefore, it is considered that the arrangement of diamond particles or the state of the interface between Cu and diamond particles can be more advantageous for heat conduction. It is also possible that oxygen, which is present on the Cu surface and inhibits heat conduction, is removed. As a result, it is considered that the Cu-diamond MMC produced by cycle pressurization has an improved thermal diffusivity and a higher thermal conductivity as compared with the case where only the first pressure is applied.

The pressure applied to the mixture of the diamond particles and the Cu powder particles is the first pressure and the second pressure in the range of 5 MPa or more and 100 MPa or less under the condition that the second pressure is larger than the first pressure. Can be set respectively. The first pressure may be 5 MPa or more and 60 MPa or less, and the second pressure may be 20 MPa or more and 100 MPa or less. Preferably, the first pressure is 5 MPa or more and less than 20 MPa, and the second pressure is 20 MPa or more and 40 MPa or less. By setting the first pressure and the second pressure in the above ranges, the thermal conductivity can be further improved.

FIG. 7A is a diagram showing an example of "cycle pressurization" during sintering. In this example, during the sintering time, the first pressure P1 and the second pressure P2 higher than the first pressure P1 are repeatedly applied to the mixed powder. As an example, when the first pressure P1 is 10 MPa and the second pressure P2 is 40 MPa, the operation of applying the first pressure P1 for 10 seconds and then applying the second pressure P2 for 20 seconds is defined as one cycle. For example, 10 to 50 cycles of pressure application can be repeated during the sintering process. As will be described later, by varying the pressure during the sintering time, the resulting composite becomes denser and has a higher relative density. This contributes to increasing the thermal conductivity of the composite material.

FIG. 7B is a diagram showing another example of "cycle pressurization" during sintering. As shown in FIG. 7B, the first pressure and the second pressure higher than the first pressure may be repeatedly applied to the mixed powder from the stage of raising the temperature. Further, the first pressure and the second pressure can be repeatedly applied even during the holding time of the sintering peak temperature Ts.

FIG. 8 is a perspective view schematically showing an example of the outer shape of the composite material 80 manufactured by the present embodiment. In this example, the composite material 80 has a disk shape having a thickness of T [mm] and a radius of R [mm]. The thickness T is, for example, 0.2 mm or more and 20.0 mm or less. The radius R is, for example, 3 mm or more and 200 mm or less. The shape of the composite material 80 immediately after sintering is not limited to the disk shape, but may have the shape of a rectangular parallelepiped or another polyhedron, or has a shape having a striped groove or a regular uneven pattern on the surface. You may be. The shape of the composite material 80 in the top view immediately after sintering is defined by the shape of the axial cross section perpendicular to the cavity 20 in FIG. For example, when the die 30 of FIG. 5 has a prismatic through hole and the lower end surface of the upper punch 40 and the upper end surface of the lower punch 50 are flat rectangular surfaces, the composite material 80 taken out from the sintering apparatus 100 Can have a thin plate shape with a rectangular top view. After being taken out from the sintering apparatus 100, the composite material 80 is thinned in order to obtain an arbitrary thickness. The thinning process includes polishing processes such as cutting and polishing, and laser processing. It is also possible to separate a plurality of heat radiating members from one composite material 80.

FIG. 9 is a schematic view showing an enlarged part of a cross section of the composite material 80 thus produced. FIG. 9 is based on cross-sectional observation with an optical microscope. The composite material 80 shown in FIG. 9 contains Cu70, which is a metal matrix, and a large number of diamond particles 10 dispersed in Cu70. Cu70 is a metal body in which Cu powder particles contained in the mixed powder are sintered and integrated by pulse energization. The individual diamond particles 10 contained in the composite material 80 are the diamond particles contained in the mixed powder. Although it is possible that a part of the diamond particles 10 is chipped during the pulse energization sintering process, the plurality of diamond particles are not combined to grow into a new single particle.

According to the above-mentioned method for producing a composite material, the thermal conductivity of the composite material can be increased, for example, by producing the Cu-diamond composite material at a lower temperature and lower pressure than those of the prior arts 1 and 2. W / mK] or higher can be set. It is also possible to obtain a composite material having a thermal conductivity of 500 [W / mK] or more. Further, the value can be 600 [W / mK], preferably 690 to 710 [W / mK] or more. This suppresses the deterioration of thermal conductivity at the diamond particles or Cu / diamond interface that occurs during high-temperature and high-pressure sintering by lowering the sintering temperature to a value lower than previously considered necessary and lowering the pressure. Or it is probable that it could be avoided.

According to the above-mentioned method for producing a composite material, the temperature difference until the Cu-diamond MMC is cooled to room temperature after pulse energization sintering is smaller than that of the prior arts 1 and 2. In the first embodiment, the amount of expansion and contraction of copper and diamond depending on the difference in coefficient of linear expansion is smaller than that of the prior arts 1 and 2. That is, since copper and diamond are less likely to be separated due to the difference in linear expansion coefficient, a decrease in thermal conductivity can be reduced.

Step S200 will be described again with reference to FIG. 3A. In this step S200, the Cu-diamond composite material is thinned. The thinning process includes polishing and laser processing. The polishing process can be performed by various polishing methods such as rough polishing, fine polishing, fixed abrasive grain method (grinding), and free abrasive grain method (polishing).

The term "polishing" in the present disclosure has a meaning including "grinding" in which the surface of the composite material 80 is scraped off by abrasive grains having a high hardness such as diamond. In general, "grinding" means that the surface portion of a workpiece to be machined is scraped off by abrasive grains, and the surface formed by grinding, that is, the machined surface is not always smooth. On the other hand, "polishing" means that the surface of the workpiece to be processed is scraped off by abrasive grains and a smooth surface is formed. Since the Cu-diamond composite material contains diamond, an ideally smooth surface may not be formed even if it is polished. Since the diamond particles are missing from the surface of the composite material due to collision or friction with the abrasive grains, irregularities of about the size of the diamond particles may remain on the processed surface of the composite material even after the polishing process. Therefore, in the present disclosure, polishing and grinding are not distinguished, and "polishing process" broadly means the process of polishing and / or grinding.

FIG. 10 is a cross-sectional view schematically showing the vicinity of the processed surface 80P of the composite material 80. The reference code "80X" is attached to the portion scraped off by the thinning process. In the example of FIG. 10, the processed surface 80P has irregularities about the size of the diamond particles 10. The thickness of the composite material 80 depends on the size of the package on which the composite material is mounted. Therefore, the thinning treatment is performed until the composite material has a desired thickness. For example, when the thickness of the composite material 80 before the thinning treatment is 1 mm, the thickness of the composite material 80 after the thinning treatment can be 100 μm or more and 800 μm or less. Such a polishing step makes it possible to make the thickness of the composite material 80 immediately after pulse energization sintering sufficiently larger than the thickness of the heat radiating member finally required. According to the inventor's experiment, if the composite material 80 to be produced is too thin, the distribution of heat generated by pulsed current sintering during the sintering process becomes non-uniform, and the characteristics of the composite material 80 vary. I found out that I would do it. Therefore, if the composite material 80 thicker than the target value is formed on the premise that the thickness is adjusted to the target value by the thinning treatment, it is possible to suppress or reduce the variation in the characteristics.

However, according to a further study by the present inventor, it has been found that the thermal conductivity of the composite material 80 after the thinning treatment can be reduced to, for example, about 80% of the thermal conductivity before the polishing step. This is due to the decrease in the relative density and thermal diffusivity of the composite material 80. It is considered that the reason is that, for example, in the case of polishing, when a part of the composite material 80 is scraped off, stress is generated and the thermal resistance at the interface between the diamond particles 10 and Cu 70 increases. Further, it is considered that one of the causes is that the adhesion between diamond and Cu inside the composite material is lowered due to the vibration during the polishing process. The decrease in relative density means that a plurality of voids are generated inside the composite material 80. Further, when laser processing is performed, heat is locally applied to the composite material, and the temperature of the composite material rises. As a result, the adhesion between the diamond particles 10 and Cu 70 may decrease due to the difference in linear expansion coefficient between the diamond particles and Cu inside the composite material. The cause of the decrease in thermal conductivity that may occur due to such thinning treatment will be hereinafter referred to as "defect" or "damage" of the composite material. The decrease in thermal conductivity due to the thinning treatment as described above may occur even if the matrix of the composite material is a metal other than Cu.

In the present embodiment, as shown in FIG. 3A, after the step S200 of performing the thinning process, the step S300 of defect recovery by re-pulse energization sintering is executed. In this step S300, it is possible to alleviate the degree of defects or damage caused by the thinning process, or to restore the original state. As a result, the thermal conductivity lowered by the thinning treatment can be increased. In other words, by re-pulse energization sintering, the thermal diffusivity of the composite material 80 can be made higher than the thermal diffusivity before re-pulse energization sintering. Repulse energization sintering can be performed in a state where a pressure of less than 50 MPa is applied to the composite material. By performing re-pulse energization sintering at a pressure of less than 50 MPa, the composite material is densely sintered again, so that the thermal conductivity lowered by the thinning treatment can be effectively improved.

In certain embodiments, repulse energization sintering is performed under low temperature and low pressure conditions. Specifically, for example, in the sintering apparatus 100 as shown in FIG. 5, the thinned composite material 80 is loaded into the cavity 20 formed between the upper punch 40 and the lower punch 50. As the sintering device 100, a sintering device capable of performing pulse energization sintering is used. When the composite material 80 is obtained by pulse-conducting sintering of a mixed powder of Cu and diamond, a sintering device of the same or the same type as the sintering device used when producing the composite material 80 may be preferably used. good. By re-pulse energization sintering, the composite material 80 is held at a temperature of, for example, 500 ° C. or higher and lower than 800 ° C. in a state where a pressure of 5 MPa or more and 50 MPa or less is applied. The applied pressure is preferably 5 MPa or more and 40 MPa or less. The holding time depends on the holding temperature, but is, for example, 60 seconds or more and 1800 seconds or less. The pressure may be applied by the above-mentioned "cycle pressurization". The method of pulse energization sintering for increasing the thermal conductivity lowered by the thinning treatment is performed under the above conditions, for example, continuous pressurization and cycle pressurization described with reference to FIGS. 6 and 7A and 7B. Can include.

FIG. 11 is a cross-sectional view schematically showing a state of the thinned composite material 80 after repulse energization sintering. As a result of re-pulse energization sintering, the degree of defects or damage caused by the thinning treatment can be alleviated and restored to the original state. This is because the relative density of the composite material 80 increases under the temperature and pressure in the repulse energization sintering process, the thermal resistance at the interface between the diamond particles and Cu decreases, and the heat dissipation path becomes shorter to diffuse the heat. This is probably because the rate has increased.

It was also found that when re-pulse energization sintering was performed, the thermal diffusivity of the composite material became higher than the thermal diffusivity before re-pulse energization sintering. Here, there is the following relationship between the thermal conductivity and the thermal diffusivity.
Thermal conductivity [W / m · K] = thermal diffusivity [m ² / sec] x specific heat [J / K · kg] x density [kg / m ³ ]

According to the results of the experiments described later, the relative density and thermal conductivity reduced by the thinning treatment are both increased by the re-pulse energization sintering. Further, for example, according to Example 1 described later, the rate of increase in thermal conductivity was larger than the rate of increase in relative density due to repulse energization sintering. This means that the re-pulse energization sintering increases the thermal diffusivity itself of the composite material 80, which has been reduced by the thinning treatment. In other words, re-pulse energization sintering is considered to contribute not only to increasing the relative density of the composite material after the thinning treatment, but also to recovering defects and damages caused by the thinning treatment.

The re-pulse energization sintering may be performed in a state where the metal powder or the metal plate is in contact with the processed surface 80P of the composite material 80. Examples of these metals are Cu, Al, CuW, CuMo and the like. From the viewpoint of thermal conductivity and ease of handling, it is preferable to use Cu. Further, it is preferable to use CuW from the viewpoint of reducing the difference in thermal expansion with the composite material 80. The Cu powder or Cu plate is easily integrated with the Cu of the composite material 80. By re-pulse energization sintering, the metal powder can form a metal layer bonded to the processed surface 80P of the composite material 80. Further, the metal plate brought into contact with the processed surface 80P of the composite material 80 can also form a metal layer bonded to the processed surface 80P of the composite material 80 by re-pulse energization sintering. The "metal plate" does not need to have self-supporting rigidity if its thickness is sufficiently thin. Such a thin metal plate may be referred to as a thin metal or foil.

FIG. 12 is a cross-sectional view schematically showing a part of the composite material 80 having the metal layer 82 thus formed. Integral sintering is realized between the metal layer 82 formed by re-pulse energization sintering and the underlying composite material 80. In particular, when the metal layer 82 is formed of Cu, it is continuous with Cu constituting the composite material 80. According to such integral sintering, when a metal is bonded onto the processed surface 80P of the composite material 80 by a physical or chemical method, or when a metal layer is bonded to the composite material 80 via a bonding material. Compared with the above, the composite material 80 and the metal layer 82 can be bonded more firmly.

The surface of the metal layer 82 is pressed against the lower end surface of the upper punch 40 during the repulse energization sintering process, for example, in the sintering apparatus 100 shown in FIG. As described above, the pressure at this time is, for example, 5 MPa or more and 50 MPa or less, and the temperature is, for example, 500 ° C. or more and less than 800 ° C. Therefore, the softened metal can be strongly bonded to the machined surface 80P. The pressure at this time is preferably 5 MPa or more and 40 MP or less.

Since the thermal conductivity of the metal layer 82 is about 400 [W / mK] at most, if the metal layer 82 is too thick, the thermal conductivity of the heat radiating substrate in which the composite material 80 and the metal layer 82 are integrally sintered decreases. do. Therefore, the thickness of the metal layer 82 is preferably, for example, 50 μm or more and 500 μm or more.

When pulse energization sintering is performed in a state where the metal powder is in contact with the processed surface of the composite material 80 to form the metal layer 82, it is easy to improve the adhesion of the metal layer 82 to the composite material 80.

Further, when repulse energization sintering is performed in a state where the metal plate is in contact with the processed surface of the composite material 80 to form the metal layer 82, a metal plate having a predetermined thickness can be used. There is an advantage that the thickness of the metal layer 82 can be easily brought close to the target value. Further, when a metal plate is used, the thermal conductivity of the metal plate can be maintained in a state close to the thermal conductivity of the metal as the material. Therefore, by increasing the thickness of the composite material 80 to a predetermined thickness or more, it is easy to improve the thermal conductivity of the heat radiating substrate in which the composite material 80 and the metal layer 82 are integrally sintered.

Since the metal layer 82 formed in this way does not substantially contain the diamond particles 10, it is possible to form a smooth surface as compared with the processed surface 80P of the composite material 80. The smooth surface contributes to expanding the effective contact area and lowering the thermal resistance when the heat generating source such as a semiconductor light emitting element and the heat radiating member are in thermal contact. Further, since the metal layer 82 is located on the surface of the composite material 80, there is also an effect that plating or the like becomes easy.

By individualizing the composite material 80 having the metal layer 82 thus obtained, a plurality of heat radiating substrates can be obtained from the composite material 80. Further, it may be used as one heat dissipation substrate without individualization.

Further, the re-pulse energization sintering can be performed without contacting the metal powder or the metal plate on the processed surface 80P of the composite material 80. In this case, a material having a lower thermal conductivity than diamond is not added to the composite material. Therefore, the thermal conductivity of the heat-dissipating substrate after re-pulse energization sintering is improved, and the thermal conductivity of the original composite material can be approached.

<Example 1>
First, a Cu-diamond MMC composite material was prepared. The composite material was obtained by the following method. Cu powder particles having an average particle size of 5 μm and diamond particles having an average particle size of 250 μm were mixed to obtain a mixed powder. The total weight of the mixed powder was 6.24 grams. The Cu powder particles were 60% by mass, the diamond particles having an average particle size of 250 μm were 20% by mass, and the diamond particles having an average particle size of 60 μm were 20% by mass with respect to the entire mixed powder. Next, a Cu-diamond MMC having a thickness of 3 mm was produced using a sintering apparatus (model number SPS-515S) manufactured by SPS Syntex. The sintering peak temperature Ts was 670 ° C., and the applied pressure was 36 MPa. The holding time of the sintering peak temperature Ts was 10 minutes. The degree of vacuum at the start of sintering was 10 Pa. The size of the composite material was 20 mm in diameter x 2.731 mm in thickness. After obtaining the composite material, the density and thermal diffusivity were measured. Table 1 shows the production conditions of the composite material.

Next, the prepared composite material was polished to form a processed surface on the composite material. By this polishing process, the thickness was reduced by 0.184 mm. After forming the machined surface, the density and thermal diffusivity were measured.

Next, the composite material on which the machined surface was formed was subjected to pulse energization sintering using the above-mentioned sintering device to obtain a heat radiating substrate. This pulse energization sintering was performed on the composite material alone without contacting the Cu powder and the Cu plate on the processed surface of the composite material. The sintering peak temperature Ts was 660 ° C., and the applied pressure was 36 MPa. The holding time of the sintering peak temperature Ts was 10 minutes. The degree of vacuum at the start of sintering was 10 Pa. By this pulse energization sintering, the thickness of the composite material was reduced by 0.122 mm. After obtaining the heat dissipation substrate, the density and thermal diffusivity were measured.

In Example 1 and each of the examples described later, the current value while maintaining the sintering peak temperature Ts was in the range of 350 A or more and 700 A or less. The pulse width of the applied voltage was 3.3 ms.

<Example 2>
A heat radiating substrate was obtained by the same method as in Example 1 except for the following points.

In preparing the composite material, the mixing ratio of Cu powder particles and diamond particles was changed. The Cu powder particles were 65% by mass, the diamond particles having an average particle size of 250 μm were 20% by mass, and the diamond particles having an average particle size of 60 μm were 15% by mass with respect to the entire mixed powder. Pulsed current sintering was performed with the sintering peak temperature Ts set to 660 ° C. Table 1 shows the production conditions of the composite material.

After polishing the composite material to form a processed surface, re-pulse energization sintering was performed with the Cu plate in contact with the processed surface to obtain a heat-dissipating substrate. The conditions for re-pulse energization sintering are the same as the sintering conditions for preparing the composite material.

<Example 3>
A heat radiating substrate was obtained by the same method as in Example 2 except for the following points.

In preparing the composite material, the first pressure was set to 10 MPa and the second pressure was set to 36 MPa, and these were repeatedly applied. The holding time of the applied pressure was 15 seconds for the first pressure, 20 seconds for the second pressure, 50 seconds for the total pressure switching time, and 85 seconds for the total time for one cycle. The number of repeated cycles was 25. The holding time of the sintering peak temperature Ts was 20 minutes. Table 1 shows the production conditions of the composite material.

After polishing the composite material to form a processed surface, pulse energization sintering was performed with Cu powder particles in contact with the processed surface to obtain a heat-dissipating substrate. The conditions for pulse energization sintering are the same as the sintering conditions for preparing a composite material.

<Thermal conductivity>
The thermal conductivity was determined for each of Examples 1 to 3. Thermal conductivity can be calculated as the product of specific heat, density and thermal diffusivity. The specific heat was obtained by weighting the literature values of the specific heat of diamond and Cu with a mixed mass ratio. Density was measured by the Archimedes method. The thermal diffusivity was obtained by a flash method using a xenon lamp using a measuring device (model number LFA-447) manufactured by Netch Japan Co., Ltd. The measurement temperature was 25 ° C. The thickness of the composite material in Example 1 was 2.731 mm, the thickness after polishing was 2.547 mm, and the thickness after pulsed current sintering was 2.425 mm. The thickness of the composite material in Example 2 was 2.636 mm, and the thickness after polishing was 2.492 mm. The thickness of the heat radiating substrate after pulse energization sintering was 2.560 mm. The thickness of the composite material in Example 3 was 2.636 mm, and the thickness after polishing was 2.445 mm. The thickness of the heat radiating substrate after pulse energization sintering was 2.510 mm. Table 2 shows the "relative density" before polishing, after polishing, and after re-pulse energization sintering, Table 3 shows the "thermal diffusivity", and Table 4 shows the "thermal conductivity". The "relative density" in Table 2 represents the relative ratio of the actual density to the true specific gravity of the composite material. In the case of Example 2 and Example 3, since the true density after repulse energization sintering is the density of the heat radiation substrate obtained by sintering the composite material and Cu powder particles or Cu plate, the repulse energization sintering is the density. It becomes difficult to understand the effect on. Therefore, the transition of the relative density was obtained for each of "after preparing the composite material", "after forming the machined surface", and "after re-pulse energization sintering".

As can be seen from Tables 2 and 3, in each of the examples, the relative density and the thermal diffusivity were reduced by the polishing step. However, the relative densities of the heat-dissipating substrates according to Examples 1 to 3 in which re-pulse energization sintering was performed after the processed surface was formed were all higher than the relative densities after the polishing process. Similarly, the thermal conductivity after re-pulse energization sintering was higher than that after polishing.

In Examples 2 and 3, a metal layer having a thickness of about 0.2 mm is present on the surface. This metal layer is formed by performing pulse energization sintering in a state where Cu powder particles or Cu plates are in contact with the polished surface of the composite material, and is a Cu layer containing no diamond particles. On the other hand, in the first embodiment, diamond particles are also present in the surface region of the heat radiating substrate. Therefore, in the heat-dissipating substrates in Examples 2 and 3 in which the Cu layer is integrally sintered, it seems that the thermal diffusivity after pulse energization sintering does not increase, as shown in Table 3. However, considering the significant improvement in thermal conductivity in Example 1 and the presence of a layer of Cu having a thermal diffusivity smaller than that of diamond in Examples 2 and 3, the thermal diffusivity of the composite material 80 itself will eventually change. It can be concluded that this example also increases due to pulsed energization sintering.

Next, an example of a step of preparing a composite material containing diamond and Cu will be shown.

<Experimental example 1>
Cu powder particles having an average particle size of 5 μm and diamond particles having an average particle size of 250 μm were mixed to obtain a mixed powder. The total weight of the mixed powder was 6.24 grams. The Cu powder particles were 80% by mass and the diamond particles were 20% by mass with respect to the whole mixed powder. Next, a Cu-diamond MMC having a thickness of 3 mm was produced using a sintering apparatus (model number SPS-515S) manufactured by SPS Syntex. The sintering peak temperature Ts was 500 ° C., and the applied pressure was 36 MPa. The holding time of the sintering peak temperature Ts was 10 minutes. The degree of vacuum at the start of sintering was 10 Pa. Table 5 shows the production conditions and the estimated thermal conductivity.

<Experimental Example 2 to Experimental Example 6>
As shown in Table 5 below, Experimental Examples 2 to 6 obtained Cu-diamond MMC by changing only the sintering temperature or both the sintering peak temperature Ts and the applied pressure with respect to Experimental Example 1. Further, in Experimental Example 5, diamond particles were used as a bimodal mixed powder. The diamond particles having an average particle size of 60 μm were 10% by mass and the diamond particles having an average particle size of 250 μm were 20% by mass with respect to the entire Cu-diamond MMC.

<Experimental Example 7>
A composite material was obtained by the same method as in Experimental Example 1 except for the following points. The sintering temperature was 640 ° C., the first pressure was 10 MPa, and the second pressure was 36 MPa, and these were repeatedly applied. The holding time of the applied pressure was 15 seconds for the first pressure, 20 seconds for the second pressure, 50 seconds for the total pressure switching time, and 85 seconds for the total time for one cycle. The number of repeated cycles was 25. The holding time of the sintering peak temperature Ts was 20 minutes.

<Experimental Example 8 and Experimental Example 9>
Cu-diamond MMC was obtained by changing each condition as shown in Table 5.

In the step of preparing the composite material, a mixed powder of diamond particles and copper powder particles is prepared, and a pressure of 5 MPa or more and 100 MPa or less is applied to the mixed powder by pulse energization sintering, and the temperature is 500 ° C. or higher and lower than 800 ° C. Experimental Examples 1 to 9 in which a composite material was produced from the mixed powder while being kept at a temperature were composite materials having higher thermal conductivity than Cu alone. These composite materials in Experimental Examples 1 to 9 can be used as composite materials in Examples 1 to 3 described above.

FIG. 13 is a diagram showing an optical micrograph of a cross section of a part of the composite material produced in the same manner as in Experimental Example 3 in Table 5. FIG. 14 is a diagram showing an optical micrograph of a cross section of a part of the composite material produced in the same manner as in Experimental Example 7 in Table 5. In each photograph, the region with relatively high lightness is the Cu portion, and the region with relatively low lightness is the diamond particles. In the composite material of FIG. 14, relatively small diamond particles having an average particle size of 60 μm are located in the gaps between relatively large diamond particles having an average particle size of 250 μm. Compared to the composite material of FIG. 13, in the composite material of FIG. 14, the number of diamond particles is increased, and the total area of the surface is also increased. This means that the area of the interface between Cu and diamond increases. When the area of this interface increases, the thermal resistance may increase and the thermal conductivity may decrease due to poor adhesion between diamond and Cu. However, no such phenomenon was observed in this experimental example.

As can be seen from FIGS. 13 and 14, the composite material in the experimental example is dense.

<Application example>
A configuration example of a light emitting device including the heat radiating substrate manufactured according to the embodiment of the present disclosure will be described.

FIG. 15 is a perspective view schematically showing a configuration example of a light emitting device 200 including a light emitting diode (LED) 22 and a heat radiating substrate 24 supporting the LED 22. The heat radiating substrate 24 was manufactured by the manufacturing method according to the above embodiment. An insulating layer 26 such as AlN is formed on the upper surface of the heat radiating substrate 24. A p-side wiring 28p and an n-side wiring 28n are formed on the insulating layer 26, and are electrically connected to the p-side electrode and the n-side electrode of the LED 22, respectively. The lower surface of the heat radiating substrate 24 is in thermal contact with a heat sink or a cooling device (not shown). The heat generated by the LED 22 during operation spreads in the in-plane direction by the insulating layer 26, and then quickly dissipates to the outside through the heat radiating substrate 24.

The above-mentioned configuration examples of the light emitting devices 200 and 300 are examples of semiconductor devices that utilize the composite material according to the embodiment of the present disclosure as a heat radiating member, and this composite material can be used for various purposes.

The method for manufacturing a heat radiating substrate according to the present disclosure provides a composite substrate that can be used as various heat radiating substrates. Examples of heat dissipation substrates include package substrates, submounts, heat spreaders, packages, and heat sinks that are in thermal contact with elements such as semiconductor light emitting devices, semiconductor integrated circuit devices, and monolithic microwave integrated circuit devices.

10 ... Diamond particles, 20 ... Cavity, 30 ... Die, 40 ... Upper punch, 50 ... Lower punch, 60 ... Power supply unit, 100 ... Sintering device

Claims (13)

The process of preparing a composite material containing diamond and metal,
A step of thinning the surface of the composite material to form a processed surface on the composite material.
A method for manufacturing a heat radiating substrate, which comprises a step of heating the composite material in a state where a pressure of less than 50 MPa is applied to the composite material by pulse energization sintering. The first aspect of claim 1, wherein the pulse energization sintering is performed in a state where a metal powder or a metal plate is in contact with the processed surface of the composite material to form a metal layer bonded to the processed surface. Manufacturing method of heat dissipation board. The method for manufacturing a heat radiating substrate according to claim 2, wherein the thickness of the metal layer is 50 μm or more and 500 μm or less. The method for manufacturing a heat-dissipating substrate according to claim 1, wherein the pulse energization sintering is performed without bringing a metal powder or a metal plate into contact with the processed surface of the composite material. The step of preparing the composite material is
The process of preparing a mixed powder of diamond particles and copper powder particles,
A step of producing the composite material from the mixed powder by holding the mixed powder at a temperature of 500 ° C. or higher and lower than 800 ° C. in a state where a pressure of 5 MPa or more and 100 MPa or less is applied to the mixed powder by pulse energization sintering is included. The method for manufacturing a heat radiating substrate according to any one of claims 1 to 4. The method for manufacturing a heat radiating substrate according to claim 5, wherein the amount of a metal other than copper added to the mixed powder is 1% or less in terms of mass ratio. The mass ratio of the copper powder particles in the mixed powder is 60% or more and 85% or less.
The method for manufacturing a heat radiating substrate according to claim 5 or 6, wherein the mass ratio of the diamond particles in the mixed powder is 15% or more and 40% or less. The method for manufacturing a heat radiating substrate according to any one of claims 5 to 7, wherein the average particle size of the diamond particles in the mixed powder is 200 μm or more and 400 μm or less. The heat-dissipating substrate according to any one of claims 5 to 8, wherein the diamond particles in the mixed powder include particles having an average particle size of 200 μm or more and 400 μm or less and particles having an average particle size of 40 μm or more and 80 μm or less. Manufacturing method. The method for manufacturing a heat-dissipating substrate according to any one of claims 5 to 9, wherein the pressure in the step of producing the composite material is 5 MPa or more and 50 MPa or less. The heat-dissipating substrate according to claim 10, wherein the step of producing the composite material is performed by repeatedly applying a first pressure and a second pressure higher than the first pressure and maintaining the temperature at the temperature. Production method. The method for manufacturing a heat radiating substrate according to any one of claims 5 to 11, wherein the average particle size of the copper powder particles is 3 μm or more and 10 μm or less. The process of preparing a thinned composite material containing diamond and metal,
A method for producing a composite substrate, which comprises a step of heating the composite material in a state where a pressure of less than 50 MPa is applied to the composite material by pulse energization sintering.

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