JP6204172B2 - Heat dissipation board - Google Patents

Description

  The present invention relates to a heat dissipation substrate having a surface excellent in heat dissipation and conductivity.

  2. Description of the Related Art In recent years, in semiconductor elements used for electronic devices and the like, with the rapid progress of high performance such as downsizing, high density and high speed, the treatment of heat generated from the semiconductor elements has become an important issue. Yes. For heat dissipation of such semiconductor elements, metallization (metallization) is performed by bonding a metal foil or thin plate of copper, aluminum, etc. with high thermal conductivity to the surface of an insulating ceramic substrate via solder or brazing material. It has been made to process. Patent documents 1-4 are mentioned as conventional art about such metallization processing of a ceramic substrate.

JP-A-8-59375 JP-A-11-79872 JP 2006-89290 A JP 2011-14924 A JP 2007-201346 A

  However, adhesion of metal foil or thin plate using solder, brazing material, etc. requires heat treatment at a high temperature of about 800 ° C. to 1000 ° C., so undulation and warpage are caused by the difference in thermal expansion coefficient between the substrate and the metal material. There was a problem that occurred. Moreover, in order to form a metal foil or a thin plate in an arbitrary form, a complicated process such as etching once bonded to a base material with solder or a brazing material has to be performed.

On the other hand, for example, Patent Document 5 discloses a technique of forming a metallized layer by directly printing and baking a metal having high thermal conductivity on a ceramic substrate. However, according to the technique of Patent Document 5, for example, when a substrate made of a nitride ceramic is used, the difference between the thermal expansion coefficient between the nitride ceramic and the high thermal conductivity metal causes the substrate and the metallized layer to There was a problem that it was difficult to obtain sufficient adhesion. For example, the thermal expansion coefficient (25 ° C. to 500 ° C.) of nitride ceramics is about 2.6 × 10 ⁻⁶ / K (Si ₃ N ₄ ) to 4.6 × 10 ⁻⁶ / K (AlN). On the other hand, the thermal expansion coefficient (25 ° C. to 500 ° C.) of copper (Cu), which is a typical metallization layer metal, is 16 × 10 ⁻⁶ / K, which is 3 to 5 times or more different. Therefore, there is a problem that the flatness of the surface of the metallized layer is impaired or the metallized layer is easily peeled off from the substrate, particularly in an environment where the temperature changes drastically.

  The present invention has been made in view of the circumstances as described above, and an object of the present invention is to provide a heat dissipating substrate in which the metallized layer is directly integrated with the substrate with good adhesiveness. Another object of the present invention is to provide a copper paste for forming such a metallized layer by printing and a method for producing such a heat-dissipating substrate.

In order to solve the above problems, the present invention provides a heat dissipating substrate. Such a heat dissipating substrate is directly provided with a heat dissipating layer containing copper as a main component and at least one surface of a substrate made of nitride ceramics. Then, the glass component, the composition when converted to oxide, is characterized by containing Ag ₂ O at a ratio of less than 5 mol% or more 0.5 mol%.
In such a configuration, the heat dissipation layer having excellent adhesion to the substrate made of nitride ceramics is provided, and the metallized layer can be prevented from peeling off from the substrate even in an environment where the temperature changes rapidly. That is, a heat dissipating substrate having excellent heat dissipation and high reliability with respect to temperature change is provided. In the present specification, the “main component” means that the substance is contained in a proportion of 50% by mass or more, preferably 70% by mass or more, for example, 80% by mass or more.

In a preferred embodiment of the heat dissipation substrate disclosed herein, the glass component has a composition when converted to an oxide, and contains at least one of BaO and ZnO in a ratio of 60 mol% or more and 95 mol% or less in total. It is characterized by that.
With such a configuration, since the glass component has a low melting point composition, bonding at a lower temperature is possible, and thermal stress generated between the substrate and the heat dissipation layer during bonding can be reduced. Thereby, a heat dissipation board provided with a heat dissipation layer with higher surface flatness is realized.

In a preferred embodiment of the heat-dissipating substrate disclosed herein, the glass component has a composition when converted to an oxide, and contains SiO ₂ at a ratio of 1 mol% to 20 mol%.
Such a configuration is preferable because the softening point of the glass component functioning as a binder can be kept low, a heat dissipation layer can be formed at a low temperature, and it can have appropriate hardness and environmental resistance.

In a preferred embodiment of the heat-dissipating substrate disclosed herein, the glass component has a composition when converted to an oxide, and Ag ₂ O: 0.5 mol% or more and 5 mol% or less, (BaO + ZnO): 60 mol% or more and 95 mol %, SiO ₂ : 1 mol% or more and 20 mol% or less, R ₂ O: 1 mol% or more and 30 mol% or less, and Al ₂ O ₃ : 0 mol% or more and 5 mol% or less. Here, R represents one or more elements selected from Group 1A in the Periodic Table of Elements, and R ₂ O represents the sum of oxides of such Group 1A elements.
Such a configuration is preferable because the composition of the glass component as a binder having better compatibility with the substrate made of nitride ceramics is presented, and the above characteristics can be realized more suitably.

In a preferred embodiment of the heat dissipation substrate disclosed herein, the glass component has a softening point of 450 ° C. or lower.
According to such a configuration, since the glass component functioning as a binder in the heat dissipation substrate can exhibit adhesion at a lower temperature, the heat dissipation substrate can be formed at a lower temperature. Thereby, the heat dissipation board | substrate which can ensure the flatness of a heat dissipation layer more reliably is realizable.
In the present specification, the softening point of glass means a temperature at which almost any molding operation of the glass becomes impossible at a temperature lower than this, and corresponds to a viscosity of about 10 ^7.6 dPa · S. Temperature. According to JIS R 3103-1: 2001, the glass has a softening point of a glass fiber having a circular cross section having a diameter of approximately 0.65 mm and a length of 235 mm, and an upper length of 100 mm in a specified furnace ( When the temperature is raised at a rate of 5 ± 1) ° C./min, a temperature at which the glass fiber elongates by its own weight at a rate of 1 mm / min is set as the softening point.

In a preferred aspect of the heat dissipation substrate disclosed herein, the heat dissipation layer is characterized in that a glass component is contained at a ratio of 3% by mass to 15% by mass.
Such a heat dissipating substrate can keep the content of the glass component as a binder low. Thus, a heat dissipating substrate provided with a heat dissipating layer having excellent heat dissipation and electrical conductivity while having excellent adhesion is provided.

In a preferred aspect of the heat-dissipating substrate disclosed herein, the nitride-based ceramic is characterized by containing silicon nitride or aluminum nitride as a main component.
According to such a configuration, the nitride is provided with excellent mechanical characteristics, a thermal expansion coefficient close to that of a semiconductor such as Si, SiC, GaN, GaAs, etc., excellent thermal conductivity (ie, heat dissipation), and high withstand voltage. A heat dissipating substrate using silicon or aluminum nitride as a substrate is provided. Such a heat dissipating substrate is also preferable in that it can be replaced with a BeO substrate containing a toxic material while having a high heat dissipating property.

In a preferred aspect of the heat dissipation substrate disclosed herein, the heat dissipation layer is provided in a region of 70% or more of at least one surface of the substrate.
Since such a heat dissipation layer can be formed by using, for example, a printing technique, it can be formed in an arbitrary form (pattern) in an arbitrary region of the surface of the substrate made of nitride ceramics. For example, it may be provided in an area of 80% or more, further 95% or more (that is, almost 100%) of at least one surface of the substrate. Thereby, for example, a heat dissipation substrate with higher heat dissipation is provided.

In a preferred aspect of the heat dissipation substrate disclosed herein, the heat dissipation layer has a total thickness of 50 μm or more and 700 μm or less.
Such a heat dissipation layer can be formed by, for example, a printing technique. Therefore, the desired thickness within the above range can be suitably controlled by printing a plurality of times. Thereby, the heat dissipation board provided with the heat dissipation layer of desired thickness, in other words, the desired heat dissipation performance is provided.

In a preferable aspect of the heat dissipation substrate disclosed herein, the heat dissipation layer has a surface roughness Ra of 1 μm or less.
Since the thermal radiation board | substrate disclosed here can suppress the thermal expansion difference of a board | substrate and a thermal radiation layer, the thermal radiation layer with high surface flatness can be provided on a board | substrate. According to such a configuration, a heat dissipating substrate including a heat dissipating layer having a desired surface and high surface accuracy is provided. According to such a heat dissipation substrate with high surface flatness, for example, when a plurality of semiconductor elements are mounted, it is not limited to wiring (electrically connecting) the plurality of elements by wire bonding. Contact can also be realized by placing plate-like electrodes.
In the present specification, the surface roughness Ra is a parameter calculated from a roughness curve, and means an arithmetic average roughness calculated in accordance with JIS B 0601: 2001.

In another aspect, the present invention provides a copper paste used for forming a heat dissipation layer on at least one surface of a substrate made of nitride ceramics. In such a copper paste, copper powder as a main component and glass powder are dispersed in an organic medium. Then, the glass powder, the composition when converted to oxide, is characterized by containing Ag ₂ O at a ratio of less than 5 mol% or more 0.5 mol%.
According to this configuration, a copper paste is provided that can form a heat dissipation layer mainly composed of copper on a substrate made of nitride ceramics while alleviating the difference in thermal expansion between the substrate and the heat dissipation layer. That is, a heat dissipation layer mainly composed of copper, which has excellent heat dissipation, can be formed with good adhesion while maintaining surface flatness. Such copper paste can be used for printing. For example, a heat dissipation layer having a desired shape can be formed by a printing technique such as screen printing or metal mask printing.

In a preferred embodiment of the copper paste disclosed herein, the glass powder is characterized in that the proportion of the total of the copper powder and the glass powder is 3% by mass or more and 15% by mass or less.
According to such a configuration, the content of the glass component as a binder contained in the heat dissipation layer can be kept low. As a result, it is possible to form a heat dissipation layer with excellent heat dissipation and electrical conductivity while having excellent adhesion.

In a preferred embodiment of the copper paste disclosed herein, the glass powder has a composition when converted to an oxide, Ag ₂ O: 0.5 mol% or more and 5 mol% or less, (BaO + ZnO): 60 mol% or more and 95 mol%. Hereinafter, SiO ₂ : 1 mol% or more and 20 mol% or less, R ₂ O: 1 mol% or more and 30 mol% or less, and Al ₂ O ₃ : 0 mol% or more and 5 mol% or less are characterized. However, the R denotes at least one element selected from Group 1A of the Periodic Table of the Elements, said R _{2 O} represents the sum of the oxides of the Group 1A element.
Such a configuration is preferable because the composition of the glass component as a binder having better compatibility with the substrate made of nitride ceramics is presented, and the above characteristics can be realized more suitably.

In a preferred embodiment of the copper paste disclosed herein, the glass powder has a softening point of 450 ° C. or lower.
According to this configuration, the heat dissipation layer can be formed on the substrate at a lower temperature, and a difference in thermal expansion between the substrate and the heat dissipation layer hardly occurs. Thereby, it is possible to realize a copper paste that can form a heat dissipation layer with a flatter surface and better adhesion.

In a preferred embodiment of the copper paste disclosed herein, the copper paste further includes a binder made of an acrylic resin.
According to such a configuration, a copper paste capable of more appropriately adjusting the dispersibility of the copper powder or the glass powder, the adhesion to the substrate, the coating property, and the like is provided.

In another aspect, the present invention provides a method for manufacturing a heat dissipation substrate. Such a manufacturing method includes preparing a substrate made of nitride ceramics, preparing a copper paste containing copper powder as a main component and containing glass powder, and applying the copper paste directly to at least one surface of the substrate. Forming a coating layer, and firing a substrate including the coating layer to form a heat dissipation layer mainly containing copper and containing a glass component on at least one surface of the substrate. Yes. Here, the glass powder contains Ag ₂ O at a ratio of 0.5 mol% or more and 5 mol% or less.
With this configuration, the heat dissipation layer can be formed directly on the substrate. Preferably, it can be formed into an arbitrary form by a technique such as printing. In addition, since the copper paste for forming the adhesion layer contains Ag ₂ O, the thermal stress between the copper, which is the main component of the heat dissipation layer, and the substrate made of nitride ceramic is suitably relaxed. Thus, it is possible to form a heat dissipation layer with better flatness and adhesion.

In a preferred embodiment of the production method disclosed herein, the baking is performed in a temperature range of 475 ° C. or higher and 700 ° C. or lower.
In order to join a metal foil or a thin plate using solder or brazing material, generally, firing at a high temperature of about 800 ° C. to 1000 ° C. is required. On the other hand, according to such a configuration, the heat radiation layer can be formed, that is, the metallization process can be performed at a lower temperature than when the metal foil or the thin plate is joined using solder or brazing material. Therefore, the thermal stress based on the thermal expansion difference between the heat dissipation layer made of copper and the substrate can be kept low, and the heat dissipation substrate including the heat dissipation layer having excellent flatness and adhesion can be manufactured.

In a preferred embodiment of the production method disclosed herein, the nitride ceramic is a ceramic mainly composed of silicon nitride or aluminum nitride.
According to this configuration, the excellent heat dissipation of the substrate mainly composed of silicon nitride or aluminum nitride can be further enhanced. In addition, such a heat dissipation layer may have conductivity and can be prevented from being peeled off from the substrate even in an environment where the temperature changes drastically. As a result, silicon nitride or aluminum nitride having excellent mechanical properties, a thermal expansion coefficient close to that of a semiconductor such as Si, SiC, GaN, GaAs, etc., excellent thermal conductivity (ie, heat dissipation), and high dielectric strength can be obtained. It is possible to manufacture a heat dissipating substrate as a substrate.

In a preferred embodiment of the production method disclosed herein, the method further includes applying the copper paste on the coating layer.
According to this configuration, a heat dissipation layer having a desired thickness can be formed. Moreover, a copper paste can also be apply | coated only to the arbitrary site | parts of an application layer, for example, the thickness of a thermal radiation layer can be adjusted in order to improve the flatness of a thermal radiation layer further.

In a preferred embodiment of the manufacturing method disclosed herein, the copper paste is applied to a region of 70% or more of at least one surface of the substrate.
Since such a heat dissipation layer can be formed by a printing technique, for example, it can be formed in an arbitrary form (pattern) in an arbitrary region on the surface of the substrate made of nitride ceramic. For example, it may be provided in an area of 80% or more, further 95% or more (that is, almost 100%) of at least one surface of the substrate. Thereby, for example, a heat dissipation substrate with higher heat dissipation can be manufactured.

In a preferable aspect of the manufacturing method disclosed herein, the heat dissipation layer is formed so that the total thickness is 50 μm or more and 700 μm or less.
According to such a configuration, for example, by applying a copper paste (which may be printing) a plurality of times, a heat dissipation layer having a desired thickness within the above range can be suitably formed. Thereby, it is possible to manufacture a heat dissipating substrate having a heat dissipation layer having a desired thickness, in other words, having a desired heat dissipation performance.

In a preferred aspect of the manufacturing method disclosed herein, the amount of the copper paste applied is adjusted so that the surface roughness of the substrate is 1 μm or less.
According to this configuration, it is possible to manufacture a heat dissipation substrate with higher flatness by adjusting the thickness of the heat dissipation layer. For such a heat dissipation substrate with high surface flatness, for example, when a semiconductor element is mounted, the surface height of a plurality of semiconductor elements can be arbitrarily adjusted. Thereby, for example, instead of forming electrodes by wire bonding between a plurality of semiconductor elements, it is possible to secure conduction between the elements by placing an electrode plate on the plurality of semiconductor elements. The

It is a cross-sectional schematic diagram which shows the usage example of the thermal radiation board | substrate which concerns on one Embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings as appropriate. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. Moreover, in the following drawings, the same code | symbol is attached | subjected and demonstrated to the member and site | part which show | plays the same effect | action, and the overlapping description may be abbreviate | omitted or simplified. The embodiments shown in the drawings are modeled as necessary to clearly explain the present invention, and do not necessarily accurately reflect the dimensional relationship (length, width, thickness, etc.) of the actual heat-dissipating substrate. It was n’t.

  The heat dissipation substrate 1 disclosed here is a so-called DBC (Direct Bonded Copper) substrate in which a heat dissipation layer 20 mainly composed of copper is directly provided on at least one surface of a substrate 10. That is, the heat dissipation layer 20 is directly provided on the substrate 10 without using a bonding material such as a brazing material or solder. The heat dissipation layer 20 may be provided only on one side of the substrate 10 or may be provided on both sides as in the example of FIG. Further, the heat dissipation layer 20 may be provided over almost the entire surface of the substrate 10 or may be provided on a part of the substrate 10. Hereinafter, the copper paste for forming the heat-radiating substrate 1 and the heat-dissipating layer 20 will be described in detail while explaining the method for manufacturing the heat-radiating substrate 1.

[substrate]
As the substrate 10, a substrate made of a nitride ceramic can be considered. The nitride ceramics are not particularly limited in terms of detailed composition, shape, dimensions, etc., as long as they are ceramics mainly composed of nitrides. Specific examples of such nitride ceramics include silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), sialon (Sialon, Si ₃ N ₄ -AlN—Al ₂ O ₃ solid solution), Examples thereof include boron nitride (BN), carbon nitride (CN _x ), and titanium nitride (TiN). These nitride ceramics may be added with various elements for the purpose of obtaining desired characteristics.
Such nitride-based ceramics have strong covalent bonds, and are superior in thermal characteristics, mechanical characteristics, and chemical stability compared to oxide-based ceramics. Regarding the thermal expansion coefficient, for example, the thermal expansion coefficient from room temperature (25 ° C.) to 500 ° C. is 2.6 × 10 ⁻⁶ / K for silicon nitride, 4.6 × 10 ⁻⁶ / K for aluminum nitride, Boron nitride is relatively low at about 1.4 × 10 ⁻⁶ / K. On the other hand, it has poor bonding properties such as sinterability compared to oxide ceramics. In the technique disclosed herein, the heat dissipation layer 20 having good adhesion to the substrate 10 made of such nitride ceramics is provided.
The “thermal expansion coefficient” used herein is an average linear expansion measured in a temperature range from room temperature (25 ° C.) to 500 ° C. using a thermomechanical analyzer (TMA) unless otherwise specified. The coefficient means a value obtained by dividing the change in the length of the sample in such a temperature range by the temperature difference. This coefficient of thermal expansion can be measured according to JIS R 3102: 1995.

[Heat dissipation layer]
The heat dissipation layer 20 is mainly composed of copper and contains a glass component as a binder component. Components other than copper (Cu) and glass components may be included for the purpose of enhancing the function of the heat dissipation layer 20. Moreover, the copper which is the main component of the heat dissipation layer 20 is not limited to a material composed of a single element of copper as long as the object of the present invention is not impaired. For example, copper may contain other elements.
In the heat dissipation layer 20, the glass component has a function of, for example, bonding copper components in a granular form or combining the copper component and the substrate. In addition, as this glass component, crystallized glass other than normal amorphous glass may be sufficient. Amorphous glass is preferred.

And in the invention disclosed here, this glass component contains silver (Ag). Such Ag is characterized in that it is contained in the glass composition when converted to an oxide in a proportion of 0.5 mol% or more and 5 mol% or less as Ag ₂ O. Although it is not clear about a detailed mechanism, the adhesiveness of the thermal radiation layer 20 and the board | substrate 10 which consists of said nitride type ceramics can be improved by containing silver in a glass component. Moreover, this glass component can also express the function which relieve | moderates the thermal stress produced between the thermal radiation layer 20 and the board | substrate 10, for example. Here, although Ag ₂ O is contained even in a small amount, an effect of improving the adhesion can be obtained, but if it is too small, such an effect cannot be clearly obtained, which is not preferable. Ag ₂ O is preferably contained in a proportion of 0.8 mol% or more, and more preferably 1 mol% or more. If the ratio of Ag ₂ O is too large, the coefficient of thermal expansion becomes unnecessarily large or the price becomes undesirably high. Ag ₂ O is preferably contained in a proportion of 4 mol% or less, and more preferably 3 mol% or less. In addition, since the thermal stress between the board | substrate 10 and the thermal radiation layer 20 is reduced, generation | occurrence | production of the wrinkle and crack in the surface of the thermal radiation layer 20 is suppressed, and since the thermal radiation layer 20 with higher flatness is formed. Is preferable.

  If it demonstrates in detail about a glass component, the heat processing temperature for formation of the thermal radiation layer 20 can be lowered | hung. According to this, the thermal stress generated between the substrate 10 and the heat dissipation layer 20 when the heat dissipation layer 20 is formed can be reduced, and the heat dissipation layer 20 with good adhesion, and thus the adhesion layer 20 with high surface flatness can be reduced. Is preferable. Therefore, for example, the glass component preferably has a composition containing a glass constituent element having an effect of lowering the softening point. Examples of the glass constituent that can lower the softening point include oxides of alkaline earth metals such as MgO, CaO, SrO, BaO, and ZnO when expressed as oxides. Especially, it is preferable that they are BaO and ZnO, More preferably, it is preferable to contain at least one of these in the ratio of 60 mol% or more and 95 mol% or less in total. That is, one of BaO and ZnO may be included, or both may be included. If the total amount of BaO and ZnO is small, the softening point of the glass component cannot be lowered sufficiently, which is not preferable. The total of BaO and ZnO is preferably 65 mol% or more, and more preferably 70 mol% or more. However, if the total amount of BaO and ZnO is too large, it is difficult to adjust the thermal expansion coefficient of the glass component, or crystals are precipitated in the glass component, making it difficult to vitrify, and the function as a binder is reduced. This is not preferable because of the risk of Therefore, the total of BaO and ZnO is preferably 90 mol% or less, and more preferably 85 mol% or less.

Moreover, it is preferable that the glass component contains SiO ₂ at a ratio of 1 mol% or more and 20 mol% or less. SiO ₂ is a component that forms a glass skeleton, and has an effect of reducing a thermal expansion coefficient, and is preferable because functions such as appropriate hardness and environmental resistance can be imparted to the heat dissipation layer 20. Therefore, SiO ₂ is preferably 3 mol% or more, and more preferably 5 mol% or more. However, too much SiO ₂ is not preferable because the glass softening point cannot be kept low. SiO ₂ is preferably at most 18 mol%, more preferably at most 15 mol%.

As the above glass component, for example, the following glass composition can be cited as a preferred example. That is, in the technique disclosed herein, the glass component is a composition in terms of an oxide, and specifically, for example, the following are preferable examples.
Ag ₂ O: 0.5 mol% or more and 5 mol% or less,
(BaO + ZnO): 60 mol% or more and 95 mol% or less,
SiO ₂ : 1 mol% or more and 20 mol% or less,
R ₂ O: 1mol% or more 30 mol% or less, and Al ₂ O _3: 0mol% or more 5 mol% or less

In addition, said R means the 1 or more types of element selected from 1A group in an element periodic table. Specifically, for example, lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr) may be used. R ₂ O means the total of oxides of these 1A group elements. Specifically, for example, lithium oxide (Li ₂ O), sodium oxide (Na ₂ O), potassium oxide (K ₂ O), rubidium oxide (Rb ₂ O), cesium oxide (Cs ₂ O), francium oxide ( Fr ₂ O) and the like. For example, the softening point can be reduced to about 450 ° C. or less by setting the glass component as described above. A lower softening point of the glass component is preferable because the heating temperature when forming the heat dissipation layer 20 can be reduced. Furthermore, it is also preferable in that the thermal stress generated between the substrate 10 and the heat dissipation layer 20 can be reduced and the surface of the heat dissipation layer 20 can be suppressed from being distorted or cracked by the thermal stress. The softening point of the glass component is, for example, preferably 420 ° C. or lower, more preferably 400 ° C. or lower, for example, 380 ° C. or lower.

  In the heat dissipation layer 20 described above, the ratio of copper and glass components as main components is not strictly limited. However, considering the balance between the heat dissipation properties (thermal conductivity characteristics) and electrical conductivity of the heat dissipation layer 20 and the adhesion of the heat dissipation layer 20 to the substrate 10, for example, the total of copper and glass components is 100 mass. %, The glass component is preferably contained in a proportion of 3% by mass or more and 15% by mass or less. If the ratio of the glass component decreases, it is not preferable because good adhesion of the heat dissipation layer 20 to the substrate is difficult to be realized. The proportion of the glass component is preferably 5% by mass or more, and more preferably 8% by mass or more. Moreover, when there is too much ratio of a glass component, since the heat dissipation and electrical conductivity which can be implement | achieved with copper which is a main component are impaired more than necessary, it is unpreferable. The proportion of the glass component is preferably 13% by mass or less, and more preferably 10% by mass or less.

  Moreover, as above-mentioned, the form in particular of the thermal radiation layer 20 is not restrict | limited, For example, the surface of the board | substrate 10 can be provided with arbitrary shapes. Specifically, for example, a plurality of semiconductor elements 30 a and 30 b are connected (mounted) to the surface of the insulating substrate 10. For example, in order to improve the heat dissipation of the substrate 1, it is preferable to provide the heat dissipation layer 20 in as wide an area as possible. However, since the heat dissipation layer 20 mainly composed of copper functions as a wiring, it is configured so as to realize a desired wiring pattern in consideration of the area, size, height, interval (arrangement), etc. of the semiconductor 30 to be mounted. can do. For example, the adjacent semiconductor elements 30a and 30b can be arranged with a heat dissipation path to reduce the thermal resistance. When the adjacent semiconductor elements 30a and 30b are not electrically joined, for example, the heat dissipation layer 20 that connects the semiconductor elements 30a and the heat dissipation layer 20 that connects the semiconductor elements 30b are separated without being continuous. The independent heat dissipation layer 20 can be formed separately (for example, any of them in an island shape). Further, since the substrate 10 can be provided with a thermal via (not shown) or the like, the heat dissipation layer 20 can be formed avoiding such a thermal via. The semiconductor element 30b can be electrically connected by, for example, the bonding wire 42. For example, by adjusting the thickness of the heat dissipation layer 20 to match the height of the semiconductor element 30a, It is possible to connect using the electrode 40. The thickness of the heat dissipation layer 20 is not limited. For example, an arbitrary thickness can be realized by forming heat dissipation layers 22a and 22b having different thicknesses or a laminated structure in which a plurality of heat dissipation layers 20, 22a and 22b are stacked. can do.

Thus, the heat dissipation layer 20 can be suitably realized as an arbitrary thickness within a range of, for example, a total thickness of about 50 μm to 700 μm, preferably about 50 μm to 500 μm, for example, 100 μm to 400 μm. In addition, since the said heat dissipation layer 20 can relieve | moderate the thermal stress which a glass component generate | occur | produces between the board | substrate 10 and the heat dissipation layer 20, generation | occurrence | production of a wrinkle and a crack on the surface of the heat dissipation layer 20 is suppressed, and flatness is more High heat dissipation layer 20 can be realized. Therefore, the heat dissipation layers 20, 22a, and 22b can be realized, for example, with a surface roughness Ra of 10 μm or less, typically 1 μm or less. Such surface roughness Ra can be, for example, 0.7 μm or less, and more preferably 0.5 μm or less. Such flatness of the heat dissipation layers 20, 22a, 22b can be suitably realized even when the thin heat dissipation layer 22a or the thick heat dissipation layer 22b is formed.
In the example of FIG. 1, the heat dissipating substrate 1 further includes heat dissipating fins 50 on the surface of the heat dissipating layer 20 on the side where the semiconductor element is not mounted (for example, the back surface). Thereby, heat can be effectively radiated from the back surface of the heat dissipation substrate 1 through a thermal via (not shown) or the like. Further, as shown in FIG. 1, in the heat dissipating substrate 1, the connection between the substrate 10 and the heat dissipating layers 20, 22a, 22b, the semiconductor elements 30a, 30b, the plate electrode 40, the bonding wire 42, etc. You may make it protect by the sealing member 44. FIG.

Hereinafter, a copper paste for forming the heat dissipation layer 20 and a method for manufacturing the heat dissipation substrate 1 will be described.
[Preparation of copper paste]
The copper paste for forming the heat dissipation layer 20 disclosed herein may be in a form in which copper powder as a main component of the heat dissipation layer 20 and glass powder as a binder are dispersed in an organic medium.
Copper powder is a substance that bears high electrical conductivity and heat dissipation of the heat dissipation layer 20 formed by firing a copper paste. There is no restriction | limiting in particular about the kind etc. of this copper powder, The copper powder provided with a composition, purity, a shape, etc. which are conventionally used for the target copper paste can be selected suitably, and can be used. For example, the copper powder may be a powder made of tough pitch copper, oxygen-free copper, a copper compound (for example, an alloy such as silver-containing copper or zirconium copper, or a metal oxide). In addition, various elements and the like may be added to the copper as long as the object of the present invention is not impaired.
There is no strict limitation on the shape and particle size of the copper powder. For example, typically, the average particle size is selected from the range of several nm to several tens of μm, for example, about 10 nm to 10 μm, depending on the application. Particles having an average particle size can be used. In the present specification, the “average particle size” means an integrated value of 50% in the particle size distribution measured by a particle size distribution measuring apparatus based on the laser scattering / diffraction method in the range where the average particle size is approximately 0.5 μm or more. In the range where the average particle diameter is about 0.5 μm or less, it can be obtained by observation means such as an electron microscope. It can be determined as the particle diameter at an integrated value of 50% in the particle size distribution created based on the equivalent circle diameter of a plurality of particles in the observed image to be observed. Note that there is no strict criticality in the particle size range to which these average particle size calculation methods are applied, and the calculation method can be appropriately selected according to the accuracy of the apparatus to be employed.

  The glass powder can improve the adhesive strength of the heat dissipation layer 20 formed by supplying the copper paste to the substrate 10 and baking it. Since the glass constituent component (glass composition) and the softening point constituting the glass powder can be equivalent to the glass component in the heat dissipation layer 20, detailed description thereof is omitted. In addition, it is preferable that the average particle diameter of this glass powder is typically adjusted to the magnitude | size below or equal to copper powder. Therefore, for example, glass powder having an average particle size of 3 μm or less, preferably 2 μm or less, and typically an average particle size of about 0.1 μm to 2 μm based on the laser scattering diffraction method is used as the glass powder. it can.

  Further, the ratio of the copper powder and the glass powder in the copper paste can be considered in the same manner as the configuration of the heat dissipation layer 20 described above. That is, although the ratio between the copper powder and the glass powder is not strictly limited, the balance between the heat dissipation property (thermal conductivity characteristic) and the electrical conductivity of the heat dissipation layer 20 and the adhesion of the heat dissipation layer 20 to the substrate 10 can be adjusted. Considering, for example, when the total of the copper powder and the glass powder is 100% by mass, the glass powder is preferably contained in a proportion of 3% by mass to 15% by mass. If the ratio of the glass powder decreases, it is not preferable because good adhesion of the heat dissipation layer 20 to the substrate is difficult to be realized. The ratio of the glass powder is preferably 5% by mass or more, and more preferably 8% by mass or more. Moreover, when there is too much ratio of glass powder, since the heat dissipation and electrical conductivity which can be implement | achieved with copper which is a main component are impaired more than necessary, it is unpreferable. The ratio of the glass powder is preferably 13% by mass or less, and more preferably 10% by mass or less.

A preferable example of the organic medium is a medium called a vehicle in which the copper powder and the glass powder are dispersed. Such a medium is typically composed of a binder and an organic solvent. Such a vehicle is not particularly limited as long as it can appropriately disperse copper powder and glass powder, and those used in conventional copper pastes and the like can be used without particular limitation.
Examples of the binder include those based on acrylic resin, epoxy resin, phenol resin, alkyd resin, cellulose polymer, polyvinyl alcohol, polyvinyl butyral, and the like. In the technique disclosed here, it is preferable to use a binder made of an acrylic resin having a melting point of about 250 ° C. Examples of such acrylic resins include (meth) acrylic monomers or copolymers having such monomers as main monomers. Specific examples of the (meth) acrylic monomer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl. (Meth) acrylate, s-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate , Isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (medium) ) Acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate Etc. In the present specification, (meth) acryl is a term meaning acryl and methacryl. The main monomer means that the monomer occupies 50% by mass or more with respect to 100% by mass of all monomer components, and preferably 80% by mass or more, for example, 90% by mass or more.

Examples of the organic solvent include cellulose polymers such as ethyl cellulose, ethylene glycol and diethylene glycol derivatives, high-boiling organic solvents such as toluene, xylene, mineral spirits, butyl carbitol, and terpineol, or combinations of two or more thereof. An organic vehicle containing as a component can be used.
In addition, the copper paste disclosed herein requires various additives that can impart desired properties such as viscosity suitable for constituting the paste and the ability to form a coating film (adhesive layer to the substrate). It may be included accordingly. Examples of such additives include surfactants, antifoaming agents, plasticizers, thickeners, antioxidants, dispersants, various photopolymerizable compounds and photopolymerization initiators, polymerization inhibitors, and substrates. And various coupling agents such as silicon-based, titanate-based, and aluminum-based materials for the purpose of improving adhesion to the surface.
And the copper paste disclosed here can be obtained by mixing the above copper powder and glass powder into an organic medium using a three-roll mill, and kneading well.

  The above copper paste is a viscoplastic fluid exhibiting non-Bingham flow, and for example, the viscosity can be adjusted so as to be suitably used for various types of printing. Such viscosity cannot be uniquely indicated because it depends on, for example, the printing method employed, the printing machine, the plate making, etc., but generally, a viscosity of 3 Pa · s or more can be considered, for example, 10 Pa · s. This can be done. In the copper paste disclosed here, a viscosity of about 10 Pa · s to 1000 Pa · s can be considered. The viscosity of the conductive paste can be measured with a viscometer or rheometer capable of measuring the viscosity of the viscoplastic fluid. The viscosity in the present specification is a value measured using a Brookfield viscometer of the HBT type under the condition of 10 rpm at 25 ° C.

  The above copper paste can be provided with a property that can be said to be excellent releasability or slip-through by adjusting, for example, the average particle diameter, solid content concentration, viscosity, and the like of the copper powder and glass powder. Therefore, the copper paste can be suitably used as a printing paste (sometimes referred to as slurry or ink) applied to, for example, screen printing, metal mask printing, gravure printing, offset printing, and ink jet printing. Therefore, in the present invention, the heat dissipation layer 20 can be formed by printing so that a predetermined wiring pattern can be realized.

Therefore, for example, a preferred embodiment of the heat dissipating substrate 10 disclosed herein will be described by taking as an example the case of manufacturing the heat dissipating substrate 1 having the heat dissipating layer 20 as the heat dissipating conductor circuit on the surface of the substrate 10.
[Preparation of substrate]
As the substrate 10, a substrate made of the above-mentioned nitride ceramics can be used. There is no restriction | limiting in particular about the shape of this board | substrate, a dimension (radius, thickness), etc., According to the intended use, it can select suitably and can use. For example, a substrate 10 made of aluminum nitride can be used.

  The copper paste prepared above is directly applied to at least one surface of the substrate 10 to form a coating layer. The method for applying the copper paste is not particularly limited. Such a copper paste is, for example, a substrate using various methods such as a screen printing method, a metal mask printing method, a gravure printing method, a casting method, a dip coating method, a spin coating method, an electrophoresis method, a spray method, and an ink jet method. Can be applied. Especially, since the copper paste disclosed here can be applied suitably to a printing technique, it is particularly preferable to apply the copper paste by a printing technique such as a screen printing method, a metal mask printing method, or a gravure printing method. By using such a printing technique, a coating layer of an arbitrary form can be accurately formed on the substrate 10. For example, a coating layer corresponding to a complicatedly shaped wiring pattern can be easily and accurately formed. Further, when such a printing technique is used, for example, a copper paste can be easily applied in an arbitrary form to a wide region of 70% or more of at least one surface of the substrate 10 with few steps. Depending on the desired wiring pattern, for example, the copper paste can be applied to an area of 80% or more, further 90% or more (for example, almost 100% of the entire surface) of the substrate. In addition, it is also preferable in that a relatively thick coating layer can be precisely formed by using a printing technique.

Furthermore, application | coating of this copper paste can also be performed further overlapping on the application layer formed on the board | substrate. When the copper paste is further applied on the coating layer, it may be performed continuously (that is, before the previously formed coating layer is not dried). The second application may be performed. Thereby, even if the thickness of an application layer becomes thick, a cross-sectional shape can be suitably maintained, for example in a substantially square shape, without a coating layer falling.
The thickness of the coating layer can be adjusted so that a heat dissipation layer obtained after firing, which will be described later, has a desired thickness. Therefore, for example, a copper paste may be further applied only to a part of the upper surface of the coating layer formed on the substrate. Further, for example, the copper paste may be repeatedly applied a plurality of times until the coating layer has a desired thickness. Although the thickness of the coating layer is not particularly limited, for example, the thickness can be adjusted such that the total thickness of the heat dissipation layer 20 obtained after firing can be 50 μm or more and 700 μm or less.

Next, the coating layer formed in this manner is dried, for example, and then baked, whereby a heat dissipation layer containing copper as a main component and a glass component can be formed. According to the technique disclosed here, since the softening point of the glass powder as the binder is kept low, the firing temperature can also be set to a relatively low temperature above the softening point. For example, baking can be performed in a temperature range of 475 ° C. or higher and 700 ° C. or lower. The firing atmosphere can be selected according to the firing temperature, etc., and is appropriately selected from an air atmosphere, an oxidizing atmosphere, an inert gas atmosphere (nitrogen gas, helium gas, argon gas, etc.), a reducing atmosphere, or a mixed atmosphere thereof. can do.
In order to obtain the heat dissipation layer 20 having a desired thickness, a thin paste layer is formed by applying a copper paste to the surface of the substrate once or twice or more, and then firing to form a thin heat sink layer on the thin heat sink layer. The copper paste may be applied again or fired once or twice or more. That is, when obtaining a heat dissipation layer having a desired thickness, a plurality of firings may be performed.

  Thereby, it is possible to accurately form the heat dissipation layer 20 mainly composed of copper and containing a glass component on the substrate 10 made of nitride ceramics. In addition, since the copper paste disclosed here is used for formation of the thermal radiation layer 20, the thermal stress which generate | occur | produces between the board | substrate 10 and the thermal radiation layer 20 at the time of formation of the thermal radiation layer 20 can be relieved. Therefore, the surface of the heat dissipation layer 20 can be prevented from being bent or cracked due to the concentration of thermal stress. Moreover, the adhesiveness between the board | substrate 10 and the thermal radiation layer 20 can be maintained highly. Thereby, the heat dissipation board | substrate 1 in which the heat dissipation layer 20 excellent in surface flatness was formed in the board | substrate 10 with sufficient adhesiveness can be manufactured. In other words, a high-quality copper metallization process can be performed on a substrate made of nitride ceramics.

  In addition, the said heat radiation layer 20 can implement | achieve the surface flatness whose surface roughness Ra is 1 micrometer or less, for example by applying a printing technique. It has been confirmed that this can be realized even when the total thickness of the heat radiation layer 20 is a thick film of about 50 μm or more and 700 μm or less. That is, according to the heat dissipation substrate 1 having such a high surface flatness, for example, when a plurality of semiconductor elements 30a and 30b are mounted, the plurality of elements 30a and 30b are wired by the bonding wires 42 (electrically. For example, the contact can be realized by mounting the plate electrode 40.

  According to such a configuration, a heat dissipating substrate is provided in which a heat dissipating layer having excellent heat dissipating properties and electrical conductivity is provided with good adhesion to a substrate made of nitride ceramics. A substrate made of nitride ceramics has excellent mechanical properties, a thermal expansion coefficient close to that of a semiconductor such as Si, SiC, GaN, GaAs, etc., excellent thermal conductivity (ie, heat dissipation), and high insulation. Has pressure resistance. Therefore, according to the heat dissipation substrate, for example, a large Si chip can be directly bonded on the circuit. Further, the structure and the manufacturing process can be further simplified as compared with the conventional heat dissipation substrate, and the mounting cost and the thermal resistance can be reduced. Note that a heat dissipating substrate mainly composed of such a nitride ceramic substrate is preferable in that it can be replaced with a BeO substrate containing a toxic material while having a high heat dissipating property.

Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to the specific examples.
Copper (Cu) powder having an average particle diameter of 1 μm and glass powders having five compositions shown in Table 1 below were mixed at a mass ratio of copper powder: glass powder of 9: 1, respectively, and a binder. Copper pastes 1 to 5 for forming a metallized layer were prepared by kneading with three rollers together with an acrylic resin as a solvent and butyl diglycol acetate (BDGAC) as a solvent. In this embodiment, the binder and the amount of the solvent were adjusted so that the viscosity of the copper paste was 1000 cps (25 ° C., 1 atm) suitable for metal mask printing.
The copper paste prepared above was printed on a commercially available silicon nitride substrate (manufactured by Mitsubishi Materials) using a metal mask plate. The printing pattern was a 10 mm × 10 mm square, and the thickness of the coating film was 100 μm to 300 μm. The printed pattern thus printed was subjected to a degreasing treatment that was held at 200 ° C. to 400 ° C. in an air atmosphere, and then baked at 475 ° C. to 700 ° C. for 1 hour in a nitrogen atmosphere. Thereby, the heat dissipation board | substrates 1-5 were prepared.
For comparison, a commercially available copper metallized substrate (product of Hitachi Metals Admet Co., Ltd.) was prepared. A heat-radiating substrate 6 was prepared by bonding a copper plate having a thickness of 300 μm to a silicon nitride substrate using a brazing material and bonding the copper plate to the substrate by firing at a predetermined temperature in a nitrogen atmosphere.

About these heat dissipation board | substrates 1-6, the surface roughness of the metallization layer after a baking process was measured. The surface roughness is measured using a surface roughness measuring instrument (Tokyo Seimitsu Co., Ltd., surfcom120A), in accordance with JIS B 0601: 2001, with arithmetic mean roughness (Ra) and maximum height (Rz). It was measured. The results are shown in Table 1.
For these heat-dissipating substrates 1 to 6, after cooling from room temperature (25 ° C.) to −20 ° C. and applying 10 heat cycles to 250 ° C., a peel test was performed on the metallized layer. The heat cycle resistance was evaluated. In the peel test, the cellophane tape (manufactured by Nichiban Co., Ltd., CT-18) was applied to the surface of the metallization layer of the heat-dissipating substrate with a finger, and then pulled in the direction of 90 ° from the surface of the substrate. The presence or absence of peeling of the metallized layer was observed visually. The results are shown in Table 1.

  The surface roughness Ra and Rz after baking maintained the flatness after printing of 0.3 μm or less for the heat dissipating substrates 1 to 3, whereas the flatness after the heat dissipating substrates 4 to 6 exceeded 1 μm. It was a result that was damaged. This is considered to be because, for the heat dissipating substrates 1 to 3, the thermal stress between the metallized layer and the substrate was well relaxed by the glass powder as the binder, and the metallized layer was not deformed or cracked by the thermal stress. It is done. On the other hand, in the heat-radiating substrates 4 to 6, it is considered that the relaxation of the thermal stress is not improved and the flatness of the metallized layer is impaired. The heat dissipating substrate 6 is obtained by attaching a copper plate to a silicon nitride substrate through a brazing material. It has been confirmed that the heat dissipating substrates 1 to 3 provided by the invention disclosed herein can realize a surface having higher flatness than the heat dissipating substrate in which the heat dissipating layer is joined by the brazing material.

  Further, in the peel test after the heat cycle, the heat dissipating substrates 1 to 3 did not peel, whereas the heat dissipating substrates 4 to 6 peeled the metallized layer. Also about this, about the heat dissipation board | substrates 1-3, the thermal stress between the metallization layer and board | substrate which generate | occur | produces by a heat cycle is relieve | moderated well by the glass powder as a binder, and the adhesiveness of a metallization layer and a board | substrate is favorable. This is thought to be due to the fact that On the other hand, regarding the heat dissipating substrates 4 to 6, it is considered that thermal stress due to a heat cycle of −20 ° C. to 250 ° C. was accumulated, which led to a decrease in adhesion between the metallized layer and the substrate. From this, it has confirmed that the heat dissipation board | substrates 1-3 provided by the invention disclosed here were excellent also in heat cycle tolerance.

When examined in more detail, for example, whether the composition of the glass powder used as the binder contains Ag ₂ O from the comparison between the heat-dissipating substrates 1, 2, and 4, the flatness and adhesion of the metallized layer. It was shown to have a great influence on sex.

In addition, about the heat dissipation board | substrate 5, since the softening point of the used glass powder was comparatively high, it was anticipated that the firing temperature of 475 degreeC-700 degreeC was low with respect to glass powder at the time of joining. Therefore, when a heat radiating substrate 5 ′ having a firing temperature of 900 ° C. was newly prepared, as shown in Table 1, the surface roughness after firing was improved for both Ra and Rz. However, in the peel test after the heat cycle, the metallized layer was peeled off because the residual stress at the interface increased.
From this, it can be expected that in order to obtain a metallized layer having a high surface flatness, the glass powder may be sufficiently softened by increasing the firing temperature at the time of bonding. However, as can be seen from the heat dissipating substrates 5 and 5 ', it was found that even if a metallized layer having a high surface flatness is simply formed, the bondability between the metallized layer and the nitride ceramic substrate is not sufficient. . Thus, the flatness of the metallized layer and the adhesion between the metallized layer and the substrate are not expressed only depending on the softening point of the glass powder used as the binder, but the specific composition of the glass powder. It was confirmed that Momo contributed.

  From the above, according to the present invention, the heat dissipating substrate made of a nitride ceramic having a metallized layer having a flat surface and excellent heat cycle resistance and an excellent adhesion, a method for producing the same, and the manufacturing method thereof A copper paste for forming a metallized layer is provided. According to such a heat dissipating substrate, for example, when a plurality of semiconductor elements are mounted, instead of forming electrodes by wire bonding between the semiconductor elements, an electrode plate is placed on the semiconductor elements. It is possible to ensure conduction between the elements. In other words, the heat dissipating substrate disclosed herein can realize a new semiconductor element structure. As mentioned above, although this invention was demonstrated in detail, the said embodiment is only an illustration and what changed and modified the above-mentioned specific example is included in the invention disclosed here.

DESCRIPTION OF SYMBOLS 1 Heat dissipation board | substrate 10 board | substrate 20, 22a, 22b heat dissipation layer 30a, 30b semiconductor element 40 plate-like electrode 42 bonding wire 44 sealing member 50 heat dissipation fin

Claims (21)

On at least one surface of a substrate made of nitride ceramics, a heat dissipation layer containing copper as a main component and a glass component is directly provided,
The glass component is a composition when converted to an oxide ,
Ag ₂ O and 0.5 mol% or more 5 mol% or less, and,
60 mol% or more and 95 mol% or less in total of at least one of BaO and ZnO,
A heat-dissipating substrate that contains The glass component is a composition in which in terms of oxide, in a proportion of SiO ₂ below 1 mol% or more 20 mol%, heat dissipation substrate according to claim 1. The glass component is a composition when converted to an oxide,
Ag ₂ O: 0.5 mol% or more and 5 mol% or less,
(BaO + ZnO): 60 mol% or more and 95 mol% or less,
SiO ₂ : 1 mol% or more and 20 mol% or less,
R ₂ O: 1 mol% or more and 30 mol% or less, and Al ₂ O ₃ : 0 mol% or more and 5 mol% or less,
(However, the R means one or more elements selected from Group 1A, the R _{2 O} is.; Total of oxide of the Group 1A element) is, according to claim 1 or 2 Heat dissipation board. The heat dissipation substrate according to any one of claims 1 to 3 , wherein the glass component has a softening point of 450 ° C or lower. The heat dissipation substrate according to any one of claims 1 to 4 , wherein the heat dissipation layer contains a glass component at a ratio of 3 mass% to 15 mass%. The heat-radiating substrate according to any one of claims 1 to 5 , wherein the nitride ceramic is mainly composed of silicon nitride or aluminum nitride. The heat dissipation substrate according to any one of claims 1 to 6 , wherein the heat dissipation layer is provided in a region of 70% or more of at least one surface of the substrate. The heat dissipation layer according to any one of claims 1 to 7 , wherein the heat dissipation layer has a total thickness of not less than 50 µm and not more than 700 µm. The heat dissipation substrate according to any one of claims 1 to 8 , wherein the heat dissipation layer has a surface roughness Ra of 1 µm or less. A copper paste used to form a heat dissipation layer on at least one surface of a substrate made of nitride ceramics,
Copper powder as a main component and glass powder are dispersed in an organic medium,
The glass powder is a composition when converted to an oxide ,
Ag ₂ O and 0.5 mol% or more 5 mol% or less, and,
60 mol% or more and 95 mol% or less in total of at least one of BaO and ZnO,
Containing copper paste. The said glass powder is the copper paste of Claim 10 whose ratio which occupies for the sum total of copper powder and glass powder is 3 mass% or more and 15 mass% or less. The glass powder is a composition when converted to an oxide,
Ag ₂ O: 0.5 mol% or more and 5 mol% or less,
(BaO + ZnO): 60 mol% or more and 95 mol% or less,
SiO ₂ : 1 mol% or more and 20 mol% or less,
R ₂ O: 1 mol% or more and 30 mol% or less, and Al ₂ O ₃ : 0 mol% or more and 5 mol% or less (wherein R represents one or more elements selected from Group 1A, and R ₂ O represents the above The copper paste according to claim 10 or 11 , wherein a total of oxides of group 1A elements is indicated. The softening point of the said glass powder is a copper paste of any one of Claims 10-12 which is 450 degrees C or less. Furthermore, the copper paste of any one of Claims 10-13 containing the binder which consists of acrylic resin. Preparing a substrate made of nitride ceramics;
Preparing a copper paste mainly composed of copper powder and containing glass powder;
Coating the copper paste directly on at least one surface of the substrate to form a coating layer;
By baking a substrate provided with the coating layer, forming a heat dissipation layer mainly containing copper and containing a glass component on at least one side of the substrate;
Including
The glass powder, Ag containing ₂ O at a ratio of less than 60 mol% or more 95 mol% of at least one of them, the total of 0.5 mol% or more 5 mol% or less, and BaO and ZnO, the manufacturing method of the heat dissipation substrate. The said baking is a manufacturing method of Claim 15 performed in the temperature range of 475 degreeC or more and 700 degrees C or less. The manufacturing method according to claim 15 or 16 , wherein the nitride ceramic is a ceramic mainly composed of silicon nitride or aluminum nitride. Furthermore, the manufacturing method of any one of Claims 15-17 including apply | coating the said copper paste further on the said application layer. The manufacturing method according to any one of claims 15 to 18 , wherein the copper paste is applied to a region of 70% or more of at least one surface of the substrate. The manufacturing method of any one of Claims 15-19 which forms the said thermal radiation layer so that total thickness may be 50 micrometers or more and 700 micrometers or less. The manufacturing method of any one of Claims 15-20 which adjusts the application quantity of the said copper paste so that the surface roughness of the said board | substrate may be 1 micrometer or less.

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