Ceramic wiring board, method for manufacturing a ceramic wiring board, and brazing material for ceramic wiring boards

Abstract

A ceramic wiring substrate comprising a ceramic substrate and a metal wiring portion formed on the ceramic substrate, wherein the metal wiring portion is a thermal conductive particle / metal composite film having thermal conductive particles containing at least one of diamond and cBN, and a metal layer containing Cu and Mg, and further containing at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, wherein the Cu content is the highest among the elements constituting the metal layer.

Description

Technical Field

[0001] The present disclosure relates to a ceramic wiring board, a method for manufacturing a ceramic wiring board, and a brazing material for a ceramic wiring board.

Background Art

[0002] A ceramic wiring board in which a metal paste is applied to the surface of a ceramic substrate and sintered to form a metal wiring is known. Such a ceramic wiring board preferably has a high thermal conductivity and excellent heat dissipation properties.

[0003] For example, Patent Document 1 discloses a step of manufacturing a first laminate by laminating a first paste layer containing copper powder and titanium hydride powder on a nitride ceramic sintered body substrate, a step of manufacturing a second laminate by laminating a second paste layer containing an alloy powder of silver and copper on the first paste layer of the first laminate, and a step of firing the second laminate to form the titanium nitride layer and the metal layer on the nitride ceramic sintered body substrate. A method for manufacturing a metallized substrate comprising the steps is disclosed. A method for manufacturing a metallized substrate comprising the steps is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present disclosure is to provide a ceramic wiring board capable of improving thermal conductivity.

Means for Solving the Problems

[0006] According to one aspect of the present disclosure, a ceramic substrate, Having a metal wiring portion formed on the ceramic substrate, The aforementioned metal wiring section is Thermally conductive particles containing at least one of diamond and cBN, A thermally conductive particle / metal composite film having a metal layer containing Cu and Mg, and further containing at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, The metal layer is provided in which the Cu content is the highest among the elements constituting the metal layer, and a ceramic wiring substrate is provided.

[0007] According to other aspects of this disclosure, A step of preparing a brazing material containing Cu and Mg, and further containing at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, wherein the Cu content is the highest among the contained elements. The process involves mixing thermally conductive particles containing at least one of diamond and cBN into the brazing material, A step of placing the brazing material containing the thermally conductive particles on a ceramic substrate, A step of heating and holding the ceramic substrate on which the brazing material is placed at a temperature above the melting point of the brazing material and below 800°C, death, In the step of preparing the brazing material, a brazing material is prepared containing 40-85 at% Cu, 1-25 at% Mg, a total of 1-25 at% of at least one element selected from Sn, Sb, and Bi, and a total of 0.1-10 at% of the active metal element. A method for manufacturing ceramic wiring boards is provided.

[0008] According to other aspects of this disclosure, Thermally conductive particles containing at least one of diamond and cBN, Cu and Mg, It comprises at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W. The aforementioned Cu is present in an amount of 40-85 at%, the aforementioned Mg in an amount of 1-25 at%, at least one element selected from Sn, Sb, and Bi in a total amount of 1-25 at%, and the aforementioned active metal element in a total amount of 0.1-10 at%, A brazing material for ceramic wiring substrates is provided, wherein the Cu content is the highest among the elements comprising Cu, Mg, and the active metal. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a ceramic wiring board whose thermal conductivity can be expected to be improved.

Brief Description of the Drawings

[0010] [Figure 1] FIG. 1 is a partial cross-sectional schematic view of a ceramic wiring board 100 in one aspect of the present disclosure. [Figure 2] FIG. 2 is a schematic view for explaining a manufacturing method of the ceramic wiring board 100 in one aspect of the present disclosure. [Figure 3] FIG. 3 is a cross-sectional SEM photograph of Sample 2 in an example of the present disclosure. [Figure 4] FIG. 4 is a cross-sectional SEM photograph of Sample 2 in an example of the present disclosure. [Figure 5] FIG. 5 is an enlarged cross-sectional SEM photograph (left side in the figure) of Sample 2 in an example of the present disclosure and the result of EDX analysis (right side in the figure).

Modes for Carrying Out the Invention

[0011] <One Aspect of the Present Disclosure> Hereinafter, one aspect of the present disclosure will be described with reference to the above-described drawings. Note that the drawings used in the following description are all schematic. The dimensions and ratios of each element shown in the drawings do not necessarily match the actual ones. Also, the dimensions and ratios of each element do not necessarily match between the drawings. In this specification, “A to B” means a numerical range of “A or more and B or less”.

[0012] (1) Configuration of the Ceramic Wiring Board FIG. 1 is a schematic partial cross-sectional view of a ceramic wiring board 100 according to one aspect of the present disclosure. As shown in FIG. 1, the ceramic wiring board 100 includes a ceramic substrate 10 and a metal wiring portion 11 formed on the ceramic substrate 10. The metal wiring portion 11 is composed of a thermally conductive particle / metal composite film having a thermally conductive particle 30 containing at least one of diamond and cBN (cubic Boron Nitride), copper (Cu) and magnesium (Mg), and a metal layer 20 further containing at least one active metal element selected from the group consisting of titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), and tungsten (W). In other words, the thermally conductive particle / metal composite film is a composite film composed of the thermally conductive particle 30 and the metal layer 20.

[0013] The ceramic substrate 10 is, for example, a ceramic plate obtained by press-molding and sintering ceramic particles, and preferably a plate such as aluminum nitride (AlN), silicon nitride (Si3N4), or alumina (Al2O3) can be used. Its shape and size are not particularly limited.

[0014] The metal layer 20 is a layer responsible for conductivity in the metal wiring portion 11. For example, it contains Cu and Mg, and further contains at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W. The metal layer 20 may further contain at least one element selected from tin (Sn), antimony (Sb), and bismuth (Bi). The metal layer 20 may further contain at least one element selected from silver (Ag) and indium (In). In this aspect, the case where Ti is used as the active metal element and the metal layer 20 contains Cu, Mg, Sn (Sb, Bi), and Ti will be mainly described.

[0015] As will be described later, the metal layer 20 is formed by heat-treating a brazing material 50 containing Cu, Mg, Sn (Sb, Bi), and the aforementioned active metal element Ti in predetermined proportions. The brazing material 50 used in this embodiment is a Cu-Mg type brazing material that does not have silver (Ag) as its main component, and among the elements constituting the brazing material 50 (here, Cu, Mg, and the elements containing the active metal), the Cu content (based on at%) is the highest. Therefore, among the elements constituting the metal layer 20, the Cu content (based on at%) is the highest. For example, the brazing material 50 contains 40-85 at% Cu, 1-25 at% Mg, a total of 1-25 at% of at least one element selected from Sn, Sb, and Bi, and a total of 0.1-10 at% of the active metal element (Ti in this embodiment). By using such a brazing material 50, the heat treatment temperature when forming the metal layer 20 can be lowered (for example, to 800°C or lower), thereby suppressing thermal deformation and reliability degradation of the thermally conductive particles 30, and improving the thermal conductivity of the ceramic wiring substrate 100. The brazing material 50 used in this embodiment may further contain at least one element selected from Ag and In, from the viewpoint of further lowering the melting point. However, from the viewpoint of electrical conductivity and electromigration, it is preferable that the total content of the elements selected from Ag and In is 0 to 50 at% (less than 40 at% for each element individually). Even when at least one element selected from Ag and In is included in the brazing material 50, it is preferable that the elements selected from Ag and In are included such that at least one element selected from Ag and In is included, and the content of Cu is the highest among the elements constituting the brazing material 50; in other words, it is preferable that the content of each element, Ag and In, is lower than the content of Cu.

[0016] The thermally conductive particles 30 contain at least one of diamond and cBN, which are materials with higher thermal conductivity than Cu, the main component of the metal layer 20 (for example, with a content of more than 50 at%). The presence of such thermally conductive particles 30 in the metal wiring portion 11 improves the thermal conductivity of the ceramic wiring substrate 100.

[0017] Here, simply introducing diamond or cBN into the metal wiring section 11 does not necessarily improve the thermal conductivity of the ceramic wiring substrate 100. For example, when diamond or cBN is mixed with an Ag-Cu-based paste (brazing material) as described in Patent Document 1, heat treatment at high temperatures exceeding 800°C is required, which can cause thermal deformation of the thermal conductive particles 30 (for example, graphitization in the case of diamond) and a decrease in the reliability of the thermal conductive particles 30 (for example, cleavage in diamond and cBN), potentially leading to a decrease in thermal conductivity. Furthermore, the use of expensive Ag may increase costs. Also, for example, if voids exist at the interface between the thermal conductive particles 30 and the metal layer 20, heat will not be easily transferred between the thermal conductive particles 30 and the metal layer 20, potentially leading to a decrease in thermal conductivity.

[0018] In contrast, in this embodiment, the use of the brazing material 50 described above allows the heat treatment temperature when forming the metal layer 20 to be lowered, so that the thermally conductive particles 30 can exist in a state that has not undergone thermal deformation (for example, if the thermally conductive particles 30 are diamond, they can exist in a state that has not been graphitized). This makes it possible to improve the thermal conductivity of the ceramic wiring substrate 100.

[0019] As shown in Figure 1, it is preferable that an interfacial reaction layer 21 containing an active metal element exists between the thermal conductive particles 30 and the metal layer 20. The interfacial reaction layer 21 is, for example, a layer formed by the reaction of a portion of the thermal conductive particles 30 and a portion of the active metal element contained in the brazing material 50. In this embodiment, where the brazing material 50 contains Ti as the active metal element, if the thermal conductive particles 30 are diamond, the layer contains TiC, and if the thermal conductive particles 30 are cBN, the layer contains at least one of TiN, TiB, or TiB2. In the case of other active metal elements, if the thermal conductive particles 30 are diamond, the interfacial reaction layer 21 contains at least one of the carbides of the active metal element, and if the thermal conductive particles 30 are cBN, the layer contains at least one of the nitrides or boron compounds of the active metal element. Other active metal elements can be active metal elements that have a low standard free energy of formation and readily react with the thermally conductive particles 30, such as carbides of active metals and nitrides or borides of active metals. In addition to Ti, at least one element selected from the group consisting of Zr, Hf, V, Nb, Ta, Cr, Mo, and W can be used. In this way, the presence of an interfacial reaction layer 21 formed by the reaction of some of the thermally conductive particles 30 and some of the active metal elements improves the thermal conductivity of the interface between the thermally conductive particles 30 and the metal layer 20. Furthermore, the wettability of the metal layer 20 to the thermally conductive particles 30 is improved, and a dense composite film can be formed.

[0020] Furthermore, as shown in Figure 1, it is preferable that an interfacial reaction layer 21 containing an active metal element is also present between the ceramic substrate 10 and the metal layer 20. This improves the thermal conductivity of the interface between the ceramic substrate 10 and the metal layer 20.

[0021] As shown in Figure 1, the metal layer 20 preferably comprises a solid solution phase 22 formed by the solid solution of other metal elements in Cu, and a compound phase 23 having at least one intermetallic compound selected from Cu4MgSn, CuMgSb, and CuMgBi.

[0022] The solid solution phase 22 mainly consists of a solid solution in which Mg is dissolved in Cu crystals, and other metal elements or active metal elements contained in the brazing material 50 may also be dissolved in it. By dissolving other metal elements in Cu, the strength of the solid solution phase 22 (the strength of the metal layer 20) can be improved through solid solution strengthening.

[0023] In the solid solution phase 22, the amounts of each metal element dissolved in Cu are preferably as follows: for example, the amount of Mg dissolved is preferably 5 at% or less, the amount of Sn dissolved is preferably 5 at% or less, the amount of Sb dissolved is preferably 4 at% or less, and the amount of Bi dissolved is preferably 1 at% or less. The amount of each metal element dissolved can be measured, for example, by energy-dispersive X-ray spectroscopy (EDX).

[0024] In the solid solution phase 22, when Mg and Sn are solid-dissolved in Cu, it is preferable that the ratio A / B is between 0.1 and 2.0, where A is the amount of Mg and B is the amount of Sn. By solid-dissolving Mg and Sn in Cu at such a ratio, the strength of the metal layer 20 can be increased.

[0025] The compound phase 23 is composed of at least one intermetallic compound selected from, for example, Cu4MgSn, CuMgSb, and CuMgBi, which precipitates. The compound phase 23 may also contain other intermetallic compounds composed of Cu, Mg, Sn, Sb, Bi, and active metal elements. The presence of a trace amount of compound phase 23 in the metal layer 20 can improve the strength of the metal layer 20 through precipitation strengthening. From this viewpoint, it is preferable that the compound phase 23 is uniformly dispersed in the solid solution phase 22. Furthermore, the presence of an appropriate amount of compound phase 23 reduces the amount of other metal elements dissolved in Cu in the solid solution phase 22, thereby improving thermal conductivity.

[0026] The average particle size d of the thermally conductive particles 30 is preferably larger than 0.5 times the film thickness a of the metal layer 20 and smaller than 1 times the film thickness a (that is, 0.5a < d < a). As a result, as shown in FIG. 1, the thermally conductive particles 30 are likely to overlap in the thickness direction of the metal wiring portion 11, and a path of the thermally conductive particles 30 is formed, so that the thermal conductivity can be improved. Specifically, a preferable value of the average particle size d of the thermally conductive particles 30 is, for example, 10 to 50 μm, and a preferable value of the film thickness a of the metal layer 20 is, for example, 20 to 100 μm. The average particle size d is obtained by observing the cross-sectional structure by SEM, extracting 30 arbitrary thermally conductive particles 30, and averaging their major diameters.

[0027] The volume ratio of the thermally conductive particles 30 in the metal wiring portion 11 is preferably 5 to 60 vol.%. If the volume ratio of the thermally conductive particles 30 is less than 5 vol.%, it may be difficult to obtain the effect of improving the thermal conductivity. On the other hand, by setting the volume ratio of the thermally conductive particles 30 to 5 vol.% or more, the effect of improving the thermal conductivity can be easily obtained. On the other hand, when the volume ratio of the thermally conductive particles 30 exceeds 60 vol.%, it becomes difficult for the metal layer 20 to fill the spaces between the thermally conductive particles 30 without gaps. On the other hand, by setting the volume ratio of the thermally conductive particles 30 to 60 vol.% or less, the metal layer 20 can be filled without gaps, and the generation of voids can be suppressed. It is preferable to adjust the ratio of the brazing material 50 and the thermally conductive particles 30 so that the volume ratio of the thermally conductive particles 30 in the metal wiring portion 11 is within the above range.

[0028] By forming the metal layer 20 using the above-described brazing material 50, the generation of voids is suppressed. When using a brazing material containing Mg, there is a concern that voids and pinholes (hereinafter collectively referred to as voids) may occur in the metal layer due to the evaporation of Mg contained in the brazing material. The presence of such voids is a factor that reduces the strength of the metal layer 20. In this regard, in this embodiment, by containing at least one element selected from Sn, Sb, and Bi, which are elements that suppress the evaporation of Mg, in the brazing material 50, the evaporation of Mg can be suppressed, and the generation of voids in the metal layer 20 can be suppressed.

[0029] Specifically, when the cross-section of the metal layer 20 in this embodiment is observed, it is approximately 10,000 μm thick. 2 It has the extremely excellent characteristic that, within any field of view, there is one or fewer voids with an equivalent circular diameter of 8 μm or larger, and more preferably none at all. In other words, when the cross-section of the metal layer 20 is observed, the number of voids with an equivalent circular diameter of 8 μm or larger is 10,000 μm. 2 Preferably, there should be one or fewer voids per unit area, and the number of voids with an equivalent circular diameter of 4 μm or larger should be 10,000 μm. 2 It is more preferable that there be one or fewer voids per unit area, and that the number of voids with an equivalent circular diameter of 1 μm or more is 10,000 μm. 2 It is even more preferable that there be one or fewer per unit.

[0030] By possessing these various features, this embodiment succeeds in improving the thermal conductivity of the ceramic wiring substrate 100.

[0031] (2) Method for manufacturing ceramic wiring boards Next, a method for manufacturing the ceramic wiring board 100 described above will be explained.

[0032] First, a brazing material 50 for forming the metal layer 20 is prepared. The brazing material 50 in this embodiment is a Cu-Mg type brazing material whose main component is Cu (for example, the Cu content is 40 at% or more, and Cu has the highest content among the elements constituting the brazing material 50). Specifically, the brazing material 50 contains 40 to 85 at% Cu, 1 to 25 at% Mg, a total of 1 to 25 at% of at least one element selected from Sn, Sb, and Bi, and a total of 0.1 to 10 at% of an active metal element (Ti in this embodiment). By using such a brazing material 50, the heat treatment temperature when forming the metal layer 20 can be lowered (for example, to 800°C or lower), which suppresses thermal deformation and reliability degradation of the thermally conductive particles 30 and makes it possible to improve the thermal conductivity of the ceramic wiring substrate 100. Furthermore, the brazing material 50 used in this embodiment may contain a total of 0 to 50 at% (less than 40 at% of each element individually) of elements selected from Ag and In, from the viewpoint of further lowering the melting point. Even if at least one of these elements selected from Ag and In is included in the brazing material 50, the brazing material 50 contains at least one element selected from Ag and In, and the Cu content is the highest among the elements constituting the brazing material 50.

[0033] Cu is an element that forms a solid solution that mainly constitutes the metal layer 20 when the brazing material 50 is heat-treated. Cu also contributes to the ductility and malleability of the metal layer 20.

[0034] Mg acts to lower the melting point of Cu, thereby reducing the heat treatment temperature of the brazing material 50. Additionally, Mg acts to increase the wettability of the brazing material 50 with respect to the thermally conductive particles 30.

[0035] At least one element selected from Sn, Sb, and Bi is readily reactive with Mg when the brazing material 50 is heated, forming ternary intermetallic compounds with, for example, Cu and Mg. Therefore, these elements act to suppress the evaporation of Mg.

[0036] When the brazing material 50 is heated, the active metal element reacts with some of the thermally conductive particles 30 to form a compound, which improves the thermal conductivity at the interface between the thermally conductive particles 30 and the metal layer 20. It also increases the wettability of the metal layer 20 to the thermally conductive particles 30, forming a dense composite film. Therefore, the content of the active metal element may be changed according to the amount of thermally conductive particles 30, as described later.

[0037] Each metal element constituting the brazing material 50 may be in the form of a powder containing at least one of the following: elemental form, hydride form, or intermetallic compound with other metal elements. A mixture of these powders can be used to form the brazing material. Any form is acceptable after mixing, but the details will be described later.

[0038] In the brazing material 50, the particle size of the powder containing each metal element can be appropriately changed depending on the type of ceramic substrate 10 and the thickness of the metal layer 20.

[0039] The wax material 50 may be in the form of a powder, foil, or paste. In the case of a paste, alcohols such as terpineol and butanediol, or toluenes, may be used as the main solvent; polyvinyl alcohol, ethylcellulose, polymethacrylic acid, polyacrylic, etc., may be used as the binder; and cationic, anionic, or nonionic surfactants may be used. Plasticizers and dispersants may also be included. The method for preparing the wax material 50 is not particularly limited, and known methods can be employed.

[0040] Once the brazing material 50 is prepared, a predetermined amount of thermally conductive particles 30 (for example, diamond or cBN) is mixed into the brazing material 50 to prepare the brazing material 50 containing thermally conductive particles 30 (also called brazing material for ceramic wiring boards). Preferably, the amount of thermally conductive particles 30 mixed is such that the proportion of thermally conductive particles 30 in the brazing material 50 is 5 to 60 vol.%. The method of mixing the thermally conductive particles 30 is not particularly limited, and known methods can be used. If the brazing material 50 is in foil form, as described later, the foil-shaped brazing material 50 is placed on the ceramic substrate 10, then the thermally conductive particles 30 are sprinkled on top of the brazing material 50, and then another foil-shaped brazing material 50 is placed on top of the brazing material 50 with the thermally conductive particles 30, or a paste-like brazing material 50 is applied on top.

[0041] Once the brazing material 50 containing the thermally conductive particles 30 is prepared, the brazing material 50 is placed on the ceramic substrate 10 as shown in Figure 2. Known methods such as screen printing, transfer, dispensing, inkjet printing, spray coating, sputtering, and vapor deposition can be used to place the brazing material 50.

[0042] After placing the brazing material 50, the ceramic substrate 10 and the brazing material 50 are heated and held in a predetermined atmosphere. The predetermined atmosphere can be any of the following: a vacuum atmosphere (reduced pressure atmosphere), an inert gas atmosphere, or a reducing atmosphere. The oxygen concentration can be adjusted by introducing an inert gas such as nitrogen (N2).

[0043] The heat treatment temperature is preferably, for example, above the melting point of the brazing material 50 and below 800°C. This suppresses thermal deformation and reliability degradation of the thermally conductive particles 30. It also improves the diffusivity of the active metal elements, making it easier to form the interfacial reaction layer 21. As the heat treatment furnace used for joining the ceramic substrate 10 and the metal layer 20, known furnaces such as static batch furnaces, multi-chamber furnaces, belt conveyor furnaces, and roller hearth kilns can be used.

[0044] Other conditions during joining include the following: Oxygen concentration: 0.01 ppm / volume or higher, and 1000 ppm / volume or lower. Retention time: There are no specific restrictions, but for example, 30 minutes to 180 minutes.

[0045] After heat treatment, the ceramic substrate 10 is cooled. By following these steps, the ceramic wiring substrate 100 according to this embodiment can be manufactured.

[0046] <Other aspects of this disclosure> The aspects of this disclosure have been specifically described above. However, this disclosure is not limited to the aspects described above and can be modified in various ways without departing from its essence.

[0047] The thermally conductive particle / metal composite film described herein possesses both high conductivity and heat transfer properties, making it applicable to applications other than the metal wiring portion of ceramic wiring substrates. For example, it can be applied to heat sinks, processing tools, and the like. [Examples]

[0048] (Preparation of samples 1-5) As ceramic substrates 10, an alumina plate measuring 10 mm × 10 mm × 0.32 mm and an aluminum nitride plate measuring 10 mm × 10 mm × 0.65 mm were prepared. As thermal conductive particles, diamonds with the particle sizes shown in Table 1 were prepared. As brazing material 50, a paste was prepared by mixing each metal element and diamond in the ratios shown in Table 1. For paste formation, terpineol was used as the solvent and polyisobutyl methacrylate as the binder, with the total amount of solvent and binder in the paste being 17 mass%. This paste was applied to the ceramic substrates 10 using screen printing. Subsequently, samples 1 to 5 were prepared by heat treatment for 120 minutes at the predetermined heat treatment temperature and atmosphere shown in Table 1. The particle sizes of the thermal conductive particles in Table 1 were obtained by observing the cross-sectional structure with SEM, extracting 30 arbitrary thermal conductive particles 30, and averaging their major axes. The heat treatment temperature was higher than the melting point of each brazing material 50. Furthermore, in this embodiment, diamond, which has a higher thermal conductivity than cBN, was selected as the thermally conductive particle. However, the present invention is not limited to diamond.

[0049] [Table 1]

[0050] The cross-sectional structures of samples 1-5 were observed using SEM. Cross-sectional SEM images of sample 2 are shown in Figures 3 and 4. As shown in Figures 3 and 4, it was confirmed that a thermal conductive particle / metal composite film, consisting of thermal conductive particles 30 and a metal layer 20, was formed on the ceramic substrate 10. Furthermore, it was confirmed that no significant voids with an equivalent circular diameter of 20 μm or more were present in the metal layer 20. Note that the black particles indicated by the arrows in Figure 4 are fragments of diamond that broke during cross-sectional processing and are not voids. It was also confirmed that there was no cleavage in the thermal conductive particles 30. Furthermore, Figure 5 shows a magnified SEM image of sample 2 (left side of the figure) and the results of EDX analysis (right side of the figure). As shown in Figure 5, it was confirmed that an interfacial reaction layer 21 containing an active metal element (Ti in this case) exists between the thermal conductive particles 30 and the metal layer 20. Similar findings were observed for samples 1 and 3-5. Samples in which the metal layer 20 had no noticeable voids with an equivalent circular diameter of 20 μm or more, and the thermal conductive particles 30 had no cleavage, and an interfacial reaction layer 21 was confirmed between the thermal conductive particles 30 and the metal layer 20, are indicated with a "○" in the cross-sectional structure column of Table 1.

[0051] For samples 1-5, X-ray diffraction (XRD) was used to check whether or not alteration had occurred in the thermally conductive particles 30. As a result, it was confirmed that the thermally conductive particles 30 in samples 1-5 had not undergone thermal denaturation.

[0052] Based on the above, it was confirmed that by using the brazing material 50 described above, thermal deformation of the thermally conductive particles 30 can be suppressed, and an improvement in the thermal conductivity of the ceramic wiring substrate 100 can be expected. Furthermore, it was confirmed that by forming an interfacial reaction layer 21 between the metal layer 20 and the thermally conductive particles 30, an improvement in the thermal conductivity at the interface between the thermally conductive particles 30 and the metal layer 20 can be expected.

[0053] <Preferred aspects of this disclosure> The following are preferred embodiments of this disclosure. Any combination of the technical details described below is possible and will yield useful effects.

[0054] According to one aspect of this disclosure, Ceramic substrate and Having a metal wiring portion formed on the ceramic substrate, The metal wiring portion has a thermal conductive particle / metal composite film comprising thermal conductive particles containing at least one of diamond and cBN, and a metal layer containing Cu and Mg, and further containing at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W. The metal layer is provided in which the Cu content is the highest among the elements constituting the metal layer, and a ceramic wiring substrate is provided.

[0055] Preferably, The metal layer further comprises at least one element selected from Sn, Sb, and Bi.

[0056] Preferably, The metal layer further comprises at least one element selected from Ag and In.

[0057] Preferably, An interfacial reaction layer containing the active metal element exists between the thermally conductive particles and the metal layer.

[0058] Preferably, An interfacial reaction layer containing the active metal element exists between the ceramic substrate and the metal layer.

[0059] Preferably, The metal layer comprises a solid solution phase in which other metal elements are solidly dissolved in Cu, and a compound phase having at least one intermetallic compound selected from Cu4MgSn, CuMgSb, and CuMgBi.

[0060] Preferably, The average particle size d of the thermally conductive particles is greater than 0.5 times the thickness a of the metal layer and less than 1 time the thickness a.

[0061] According to other aspects of this disclosure, A step of preparing a brazing material containing Cu and Mg, and further containing at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, wherein the Cu content is the highest among the contained elements. The process involves mixing thermally conductive particles containing at least one of diamond and cBN into the brazing material, A step of placing the brazing material containing the thermally conductive particles on a ceramic substrate, A method for manufacturing a ceramic wiring substrate is provided, comprising the step of heating and holding the ceramic substrate on which the brazing material is arranged at a temperature above the melting point of the brazing material and below 800°C.

[0062] Preferably, In the process of preparing the brazing material, a brazing material is prepared containing 40-85 at% Cu, 1-25 at% Mg, a total of 1-25 at% of at least one element selected from Sn, Sb, and Bi, and a total of 0.1-10 at% of the active metal element.

[0063] Preferably, In the process of preparing the brazing material, a brazing material is prepared that further contains at least one element selected from Ag and In in total amount of 50 at% or less, and in which the content of Ag or In is lower than the content of Cu.

[0064] According to other aspects of this disclosure, Thermally conductive particles containing at least one of diamond and cBN, Cu and Mg A brazing material for ceramic wiring substrates is provided, comprising at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, wherein the Cu content is the highest among the elements comprising Cu, Mg, and the active metal element.

[0065] Preferably, It contains 40-85 at% Cu, 1-25 at% Mg, a total of 1-25 at% of at least one element selected from Sn, Sb, and Bi, and a total of 0.1-10 at% of the active metal element.

[0066] Preferably, It further contains at least one element selected from Ag and In in total amount of 50 at% or less, and the content of Ag or In is lower than the content of Cu. [Explanation of symbols]

[0067] 10 Base material 11 Metal wiring section 20 metal layer 21 Interfacial reaction layer 22 Solid solution phase 23 Compound phase 30 Thermally conductive particles 50 Brazing material 100 Ceramic Wiring Boards

Claims

1. Ceramic substrate and Having a metal wiring portion formed on the ceramic substrate, The aforementioned metal wiring section is Thermally conductive particles containing at least one of diamond and cBN, A thermally conductive particle / metal composite film having a metal layer containing Cu and Mg, and further containing at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, The metal layer is a ceramic wiring substrate in which Cu has the highest content among the elements constituting the metal layer.

2. The ceramic wiring substrate according to claim 1, wherein the metal layer further comprises at least one element selected from Sn, Sb, and Bi.

3. The ceramic wiring substrate according to claim 2, wherein the metal layer further comprises at least one element selected from Ag and In.

4. The ceramic wiring substrate according to claim 1, wherein an interfacial reaction layer containing the active metal element is present between the thermally conductive particles and the metal layer.

5. The ceramic wiring substrate according to claim 1, wherein an interfacial reaction layer containing the active metal element is present between the ceramic substrate and the metal layer.

6. The ceramic wiring substrate according to claim 1, wherein the average particle size d of the thermally conductive particles is greater than 0.5 times the thickness a of the metal layer and less than 1 time the thickness a.

7. A step of preparing a brazing material containing Cu and Mg, and further containing at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, wherein the Cu content is the highest among the contained elements. The process involves mixing thermally conductive particles containing at least one of diamond and cBN into the brazing material, A step of placing the brazing material containing the thermally conductive particles on a ceramic substrate, The process includes a step of heating and holding the ceramic substrate on which the brazing material is arranged at a temperature above the melting point of the brazing material and below 800°C. A method for manufacturing a ceramic wiring substrate, comprising the step of preparing the brazing material, wherein the brazing material contains 40 to 85 at% of Cu, 1 to 25 at% of Mg, a total of 1 to 25 at% of at least one element selected from Sn, Sb, and Bi, and a total of 0.1 to 10 at% of the active metal element.

8. The method for manufacturing a ceramic wiring substrate according to claim 7, wherein in the step of preparing the brazing material, the brazing material further contains a total of 50 at% or less of an element selected from Ag and In, and the content of each Ag or In is lower than the content of Cu.

9. Thermally conductive particles containing at least one of diamond and cBN, Cu and Mg, A brazing material for ceramic wiring substrates comprising at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, wherein the material contains 40 to 85 at% Cu, 1 to 25 at% Mg, a total of 1 to 25 at% of at least one element selected from Sn, Sb, and Bi, and a total of 0.1 to 10 at% of the active metal element, wherein the Cu content is the highest among the elements comprising Cu, Mg, and the active metal element.

10. The brazing material for ceramic wiring substrates according to claim 9, further containing a total of 50 at% or less of an element selected from Ag and In, wherein the content of Ag or In is lower than the content of Cu.

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