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

Abstract

This invention provides a ceramic wiring substrate that offers low cost and high design flexibility for wiring layer thickness by increasing the bonding strength between the wiring layer and the ceramic substrate. [Solution] A ceramic wiring substrate comprising a ceramic substrate and a metal wiring layer formed on the ceramic substrate, wherein the metal wiring layer comprises Cu, Mg, at least one element selected from Sn, Sb, and Bi, and at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W.

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 wiring.

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 method for manufacturing a metallized substrate including 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 forming the titanium nitride layer and the metal layer on the nitride ceramic sintered body substrate by firing the second laminate.

[0004] Further, Patent Document 2 discloses a method for manufacturing a metallized substrate including an adhesion step of attaching a conductive composition containing Ag particles, a metal component, and glass particles to a ceramic substrate, and a firing step of firing the conductive composition attached to the ceramic substrate to form a conductive portion.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] As described in Patent Document 1, using a paste (brazing material) with silver (Ag) as the main component increases the manufacturing cost of ceramic wiring boards. Furthermore, since Patent Document 1 involves stacking multiple paste layers, the process cost is also high.

[0007] Furthermore, if the ceramic substrate is an oxide such as alumina (Al2O3), it is necessary to pre-form a layer of molybdenum (Mo) or the like on the surface of the ceramic substrate to ensure adhesion between the ceramic substrate and the metal layer, which increases manufacturing costs.

[0008] Furthermore, as described in Patent Document 2, etc., when forming a wiring layer using a conductive paste containing conductive particles such as Ag or copper (Cu) and glass particles (glass frit), sufficient adhesive strength to the ceramic substrate cannot be obtained, making it difficult to increase the thickness of the wiring film to improve heat dissipation and conductivity.

[0009] The purpose of this disclosure is to provide a ceramic wiring substrate that is low-cost and offers high design flexibility for wiring layer thickness by increasing the bonding strength between the wiring layer and the ceramic substrate. [Means for solving the problem]

[0010] According to one aspect of this disclosure, Ceramic substrate and The ceramic substrate has a metal wiring layer formed on it, The aforementioned metal wiring layer is Cu and Mg and, At least one element selected from Sn, Sb, and Bi, A ceramic wiring substrate 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.

[0011] According to other aspects of this disclosure, A step of disposing a brazing filler metal for wiring, which contains Cu, Mg, and at least one first element selected from Sn, Sb, and Bi, and at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, on a ceramic substrate so as to correspond to a wiring pattern; A method for manufacturing a ceramic wiring substrate is provided, which includes a step of heating and holding the ceramic substrate on which the brazing filler metal for wiring is disposed.

[0012] <E000067>According to another aspect of the present disclosure, Cu, Mg, at least one first element selected from Sn, Sb, and Bi, and a brazing filler metal for wiring is provided, which contains at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W.

Advantages of the Invention

[0013] According to the present disclosure, it is possible to provide a ceramic wiring substrate that can be expected to have a high design freedom of the wiring layer thickness by increasing the bonding strength between the wiring layer and the ceramic substrate at a low cost.

Brief Description of the Drawings

[0014] [Figure 1] FIG. 1 is a partial cross-sectional schematic view of a ceramic wiring substrate 100 in one aspect of the present disclosure. [Figure 2] FIG. 2 is a schematic view for explaining a method of manufacturing a ceramic wiring substrate 100 in one aspect of the present disclosure. [Figure 3] FIG. 3 is a partial cross-sectional schematic view of a ceramic wiring substrate 100 in another aspect of the present disclosure. [Figure 4] FIG. 4 is an external appearance photograph of Sample 5 in an example of the present disclosure. [Figure 5] FIG. 5 is a cross-sectional SEM photograph of Sample 5 in an example of the present disclosure. <00000%2>

Embodiments for Carrying Out the Invention

[0015] <One aspect of the present disclosure> Hereinafter, one aspect of the present disclosure will be described with reference to the above-described group of 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".

[0016] (1) Wiring brazing material First, the wiring brazing material for manufacturing the ceramic wiring substrate of this embodiment will be described. The wiring brazing material of this embodiment is a Cu-Mg-based active metal brazing material having Cu as a main component (for example, the content rate of Cu is 40 at% or more, or the content of Cu is the largest among the elements constituting the brazing material). Specifically, the wiring brazing material includes copper (Cu), magnesium (Mg), and at least one first element selected from the group consisting of tin (Sn), antimony (Sb), and bismuth (Bi) (hereinafter also referred to as "Mg evaporation suppressing element"), and 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). The wiring brazing material may further include at least one second element (hereinafter also referred to as "melting point lowering element") selected from the group consisting of Ag, In, and Mn. The wiring brazing material of this embodiment preferably contains Mg, Mg evaporation suppressing element, active metal element, and inevitable impurities, and the balance is composed of Cu, and may further contain a melting point lowering element.

[0017] Cu is an element that forms a solid solution mainly constituting the metal wiring layer when the wiring brazing material is heated and the wiring brazing material is joined onto the ceramic substrate. Also, Cu contributes to the ductility and malleability of the metal wiring layer.

[0018] Mg acts to lower the melting point of Cu, thereby reducing the bonding temperature of the wiring brazing material. Additionally, Mg increases the wettability of the wiring brazing material to the ceramic substrate.

[0019] Mg evaporation-inhibiting elements are elements that readily react with Mg when wiring brazing material is heated, and act to form compounds with Mg through this reaction. These compounds have a higher melting point than Mg and, although they melt at the joining temperature, they are formed as eutectic structures where the molten Mg and other components do not easily evaporate. Therefore, Mg evaporation-inhibiting elements can suppress Mg evaporation by reacting with Mg during joining. For example, when wiring brazing material is heated, Mg evaporation-inhibiting elements form ternary intermetallic compounds with Cu and Mg, and act to improve the strength of these intermetallic compounds. At least one element selected from the group consisting of Sn, Sb, and Bi can be used as the Mg evaporation-inhibiting element.

[0020] Melting point depressors act to lower the melting point of wiring brazing materials. They also contribute to improving the wettability of wiring brazing materials. As melting point depressors, at least one element selected from the group consisting of Ag, In, and Mn can be used. The melting point depressors are either solid-dissolved in Cu or diffused into the materials to be joined. Ag may exist as a single phase in the metal wiring layer. To reduce costs, it is preferable that the content of at least one melting point depressor selected from the group consisting of Ag, In, and Mn is less than that of Cu.

[0021] The active metal element reacts with the ceramic substrate when the wiring brazing material is heated to form a compound (e.g., a nitride), thereby increasing the bonding strength between the ceramic substrate and the metal wiring layer. As the active metal element, at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, etc., can be used. In particular, the use of Ti is preferred.

[0022] The content of each metal element constituting the wiring brazing material is preferably such that, for example, the Cu content is 40 to 85 at%, the Mg content is 1 to 25 at%, the total content of Mg evaporation-inhibiting elements is 1 to 25 at%, and the total content of active metal elements is 0.1 to 10 at%. Furthermore, the total content of melting point depressing elements is preferably 50 at% or less (less than 40 at% for each individual element). More preferably, the total is 35 at% or less, and even more preferably, the total is 20 at% or less.

[0023] Furthermore, when the Mg content is Xat% and the Mg evaporation-inhibiting element content is Yat%, it is preferable that X-5 ≤ Y ≤ X+5. By including each element in such proportions, it is possible to achieve a predetermined bonding strength in the metal wiring layer while lowering the bonding temperature of the wiring brazing material. Note that Y is greater than 0 and not greater than 100.

[0024] The form of the wiring brazing material is not particularly limited, but from the viewpoint of obtaining a homogeneous phase structure in the metal wiring layer described later, it is preferable that it be in the form of a paste or powder. The paste-type wiring brazing material is composed of a powder containing the above-mentioned elements, a solvent, a binder, etc.

[0025] In wiring brazing materials, the form in which each element is contained (addition form) is not particularly limited. Each element may be contained as a single powder, or as a compound powder containing each element. The following describes the forms in which each element is contained.

[0026] Mg is preferably included in the brazing material in the form of a powder containing at least one of the following: elemental Mg, Mg solid solution containing other elements, compound with Cu (MgCu2), compound with an active metal element, compound with an Mg evaporation-inhibiting element, or compound with an element that lowers the melting point (by adding the powder to the brazing material). Of these, it is preferable that at least a portion of the Mg is included in the brazing material in the form of a powder containing an intermetallic compound with an Mg evaporation-inhibiting element. For example, suitable forms of Mg include an alloy powder formed from Mg and an intermetallic compound containing an Mg evaporation-inhibiting element, or an alloy powder formed from Mg and an intermetallic compound containing an Mg evaporation-inhibiting element, and an Mg evaporation-inhibiting element. Alternatively, the alloy powder may be included in a mixed state with at least one of the above, such as Mg powder or Mg-Cu intermetallic compound powder. By pre-forming at least a portion of the Mg into an intermetallic compound with an element that suppresses Mg evaporation, the evaporation of Mg during the melting of the wiring brazing material can be more reliably suppressed. Note that alloy powder refers to a material in which each element is contained in an alloy form within a single particle, rather than a mixture of powders containing one element and powders containing another element. Furthermore, a solid solution containing other elements refers to a material in which some of the elements constituting the solid solution in the crystal are replaced by other elements, or in which other elements have penetrated into the gaps in the crystal lattice.

[0027] The alloy powder only needs to contain at least Mg and a Mg evaporation-inhibiting element, and may further contain Cu. As for the alloy powder, if the Mg evaporation-inhibiting element is Sn, for example, Mg2Sn or Cu4MgSn can be used. If the Mg evaporation-inhibiting element is Sb, Mg3Sb2 or CuMgSb can be used. If the Mg evaporation-inhibiting element is Bi, Mg3Bi2 or CuMgBi can be used.

[0028] The alloy powder may also be prepared by mixing, for example, Mg and an element that inhibits Mg evaporation, and optionally Cu and an element that lowers the melting point, dissolving them, and then atomizing the mixture to produce powders containing each element.

[0029] The content (amount added) of alloy powder containing Mg and Mg evaporation-inhibiting elements is not particularly limited, but it is preferable that the Mg content derived from the alloy powder be 40% or more of the total Mg content in the wiring brazing material. For example, when using alloy powder containing Mg and Mg evaporation-inhibiting elements in combination with at least one of the following: elemental Mg powder, Mg-active metal alloy powder, Mg-Cu intermetallic compound powder, etc., it is preferable to adjust the content of the alloy powder containing Mg and Mg evaporation-inhibiting elements so that the Mg content derived from the alloy powder is 40% or more of the total Mg content in the wiring brazing material. The content of the alloy powder may be 100% of the total Mg content in the wiring brazing material, that is, it may contain only alloy powder. By using such a content, the evaporation of Mg can be suppressed more stably.

[0030] Cu may be contained in the brazing material in the form of a powder containing at least one of the following: elemental Cu, a Cu solid solution containing other elements, an intermetallic compound with Mg (e.g., MgCu2), an intermetallic compound with an Mg evaporation-inhibiting element or a melting point-depressing element (e.g., Cu3Sn, Cu3Sb), an intermetallic compound with an active metal element (e.g., a Cu-Ti compound (Cu4Ti or Cu3Ti2)), or an alloy formed by elemental Cu, a solid solution, and an intermetallic compound formed with Cu.

[0031] The Mg evaporation-inhibiting element may be contained in the brazing material in the form of a powder containing at least one of the following: the element itself, a solid solution containing other elements, a compound formed with Mg, Cu, a melting point depressant element, and at least one of an active metal element, or an alloy formed by the element itself, a solid solution, and an intermetallic compound formed with Cu.

[0032] The melting point depressing element may be included in the brazing material in the form of a powder containing at least one of the following: an element in its elemental form, a solid solution containing other elements, a hydride, or an intermetallic compound formed with at least one of the following elements: Mg, Cu, a Mg evaporation-inhibiting element, or an active metal element.

[0033] The active metal element may be included in the brazing material in the form of a powder containing at least one of the following: an elemental element, a solid solution containing other elements, a hydride, or an intermetallic compound formed with at least one of the elements Mg, Cu, Mg evaporation-inhibiting elements, or melting point-depressing elements.

[0034] In wiring brazing materials, the particle sizes of each powder containing Cu, Mg, Mg evaporation-inhibiting elements, melting point-depressing elements, and active metal elements can be appropriately changed according to the thickness of the metal wiring layer, etc. Specifically, it is preferable that the median diameter D50 is 150 μm or less. On the other hand, there is no particular lower limit to the median diameter D50, but from the viewpoint of suppressing the effect of surface oxidation of the powder, it is preferable that the median diameter D50 is 1 μm or more. The median diameter D50 is measured, for example, using a laser diffraction particle size distribution analyzer, and represents the particle size of 50% of the volume-based integrated distribution curve.

[0035] Wiring brazing materials can be used as a paste containing metal powder as needed, and may also contain binders, solvents, surfactants, plasticizers, dispersants, etc. Examples of binders include polyvinyl alcohol, ethyl cellulose, polymethacrylic acid, and polyacrylic. Examples of solvents include alcohols such as terpineol and butanediol, and toluenes. Examples of surfactants include cationic, anionic, and nonionic surfactants.

[0036] The method for preparing the wiring brazing material is not particularly limited, and any conventionally known method may be used. Furthermore, the wiring brazing material in this embodiment is used as a conductive material for forming a conductive layer or a conductive pattern on a substrate.

[0037] (2) Configuration of ceramic wiring board Next, the configuration of the ceramic wiring substrate 100 for this embodiment will be described. Figure 1 is a schematic partial cross-sectional view of the ceramic wiring substrate 100 in this embodiment. As shown in Figure 1, the ceramic wiring substrate 100 has a ceramic substrate 10 and a metal wiring layer 20 formed on the ceramic substrate 10. The metal wiring layer 20 has a predetermined wiring pattern and contains Cu, Mg, at least one element selected from Sn, Sb, and Bi (Mg evaporation suppressing element), and at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W.

[0038] The ceramic substrate 10 is, for example, a ceramic plate material obtained by pressure molding and sintering ceramic granules, and preferably a plate material such as aluminum nitride (AlN), silicon nitride (Si3N4), or alumina (Al2O3) can be used. Its shape and size are not particularly limited.

[0039] Conventionally, when a ceramic substrate is made of an oxide such as alumina, it was necessary to pre-form a layer containing Mo or the like on the surface of the ceramic substrate to ensure adhesion between the ceramic substrate and the metal wiring layer. In contrast, in the ceramic wiring substrate 100 for this invention, an interfacial reaction layer 21 containing at least one of an active metal element compound or magnesium oxide (MgO) is formed between the ceramic substrate 10 and the metal wiring layer 20. Therefore, adhesion between the ceramic substrate 10 and the metal wiring layer 20 can be ensured without pre-forming a layer containing Mo or the like. The interfacial reaction layer 21 will be described in detail later.

[0040] The metal wiring layer 20 is a layer having a predetermined wiring pattern, and 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 wiring layer 20 may also further contain at least one element selected from Sn, Sb, and Bi (an element that suppresses Mg evaporation). Furthermore, the metal wiring layer 20 may contain at least one element selected from Ag, In, and Mn (an element that lowers the melting point) in a quantity less than the Cu content. Preferably, this quantity is less than the Mg content. In this embodiment, the case in which Ti is used as the active metal element will be mainly described.

[0041] The metal wiring layer 20 is formed by heat-treating the wiring brazing material 50 described in (1). The wiring brazing material 50 used in this embodiment is a Cu-Mg type brazing material that does not have Ag as its main component. By using such wiring brazing material 50, costs can be reduced compared to when a brazing material with Ag as its main component is used. In addition, it has excellent wettability to the ceramic substrate 10 and improved strength, making it possible to increase the design flexibility of the thickness of the metal wiring layer 20. Furthermore, since the heat treatment temperature when forming the metal wiring layer 20 can be lowered, warping and residual stress due to differences in thermal expansion coefficients can be reduced. The wiring brazing material 50 used in this embodiment may further contain at least one element selected from Ag, In, and Mn (melting point depressor element) from the viewpoint of further lowering the melting point. However, from the viewpoint of electrical conductivity and electromigration, it is preferable that the content of the melting point depressor element selected from Ag, In, and Mn is 50 at% or less in total (each element individually is less than 40 at% and does not exceed the content of Cu). More preferably, the total is 35 at% or less, and even more preferably 20 at% or less. Furthermore, the content of the melting point depressant element selected from Ag, In, and Mn is preferably less than the content of Mg.

[0042] As described above, the wiring brazing material 50 contains Mg evaporation-inhibiting elements, so there is almost no significant decrease in the amount of Mg in the brazing material due to evaporation during heat treatment. Furthermore, since the wiring brazing material 50 is heat-treated without contact with other metal plates, there is almost no diffusion of metal from other metal plates into the brazing material, or from the brazing material to other metal plates. Therefore, it can be said that the content of each element in the metal wiring layer 20 and the wiring brazing material 50 is approximately equal. Specifically, in the metal wiring layer 20, it is preferable that the Cu content is the highest among the elements constituting the metal wiring layer 20, preferably 40 to 85 at%, the Mg content is preferably 0.2 to 25 at%, the total content of Mg evaporation-inhibiting elements is preferably 1 to 25 at%, and the total content of active metal elements is preferably 0.1 to 10 at%. Furthermore, even if the total content of the active metal elements is 0.1 at%, the presence of the interfacial reaction layer 21 described later between the metal wiring layer 20 and the ceramic substrate 10 can increase the bonding strength between the metal wiring layer 20 and the ceramic substrate 10. In addition, it is preferable that the total content of melting point depressing elements be 50 at% or less (each element individually not exceeding the Cu content, less than 40 at%). More preferably, the total is 35 at% or less, and even more preferably, 20 at% or less. Note that if the evaporation of Mg is suppressed from the start of heat treatment until the entire wiring brazing material 50 melts, the effects of Mg (such as void suppression) will be exerted. Afterward, even if some of the Mg evaporates and the Mg content in the metal wiring layer 20 decreases to some extent, there is no problem.

[0043] Since the metal wiring layer 20 is formed using the wiring brazing material 50 described above, the bonding strength with the ceramic substrate 10 can be improved compared to the case where a conductive paste containing conductive particles and glass frit is used, as described in Patent Document 2, etc. This makes it possible to increase the design flexibility of the thickness of the metal wiring layer 20 in order to improve heat dissipation and conductivity.

[0044] As shown in Figure 1, it is preferable that an interfacial reaction layer 21 containing at least one of an active metal element compound or MgO exists between the ceramic substrate 10 and the metal wiring layer 20. The interfacial reaction layer 21 is, for example, a layer formed by the reaction of a part of the ceramic substrate 10 with a part of the active metal element or Mg contained in the wiring brazing material 50. In this embodiment, where the wiring brazing material 50 contains Ti as the active metal element, if the ceramic substrate 10 contains a nitride such as AlN or Si3N4, the layer contains titanium nitride (TiN), and if the ceramic substrate 10 contains an oxide such as alumina, the layer contains MgO. The presence of the interfacial reaction layer 21 improves the adhesion of the metal wiring layer 20. In addition, heat is more easily transferred to the ceramic substrate 10, thus improving heat dissipation.

[0045] The interfacial reaction layer 21 may further contain silicides or aluminides of active metal elements. If the ceramic substrate 10 contains Si3N4, the interfacial reaction layer 21 may contain a silicide of an active metal element, such as Ti5Si3, and if the ceramic substrate 10 contains AlN, the interfacial reaction layer 21 may contain an aluminide of an active metal element, such as TiAl.

[0046] As shown in Figure 1, the metal wiring layer 20 preferably includes 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.

[0047] The solid solution phase 22 mainly consists of a solid solution in which Mg, etc., is dissolved in Cu crystals, and other metal elements or active metal elements contained in the wiring 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 wiring layer 20) can be improved through solid solution strengthening.

[0048] 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).

[0049] In the solid solution phase 22, when Mg and Sn are dissolved in Cu, it is preferable that the ratio A / B is between 0.1 and 2.0, where A is the amount of dissolved Mg and B is the amount of dissolved Sn. By dissolving Mg and Sn in Cu at such a ratio, the strength of the metal wiring layer 20 can be increased.

[0050] 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, Mg evaporation-inhibiting elements, melting point-depressing elements, and active metal elements. The presence of a trace amount of compound phase 23 in the metal wiring layer 20 can improve the strength of the metal wiring 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.

[0051] The thickness of the metal wiring layer 20 can be, for example, 5 μm or more. Since the metal wiring layer 20 is formed using the wiring brazing material 50 described above, it has excellent wettability to the ceramic substrate 10 and high bonding strength, so even a metal wiring layer thicker than 5 μm can be formed without peeling. In other words, it is possible to have a high degree of design freedom for the thickness of the metal wiring layer 20. Forming a thicker metal wiring layer 20 improves heat dissipation, making it suitable for applications that carry high currents. There is no particular upper limit to the thickness of the metal wiring layer 20, but from the viewpoint of not making the cost too high, for example it should be 300 μm or less. The thickness of the metal wiring layer 20 is more preferably 20 to 150 μm, and even more preferably 50 to 100 μm. When measuring the thickness of the metal wiring layer 20, for example, the cross-sectional structure can be observed by SEM, three points can be measured, and the average value can be taken.

[0052] The metal wiring layer 20 is formed using the wiring brazing material 50 described above, thereby suppressing the generation of voids. When using wiring brazing material containing Mg, there is a concern that the Mg contained in the wiring brazing material will evaporate, causing voids and pinholes (hereinafter collectively referred to as voids) to occur in the metal wiring layer. The presence of such voids is a factor that reduces the strength of the metal wiring layer 20. In this embodiment, by including at least one element selected from Sn, Sb, and Bi, which are elements that suppress the evaporation of Mg, in the wiring brazing material 50, the evaporation of Mg can be suppressed, and the generation of voids in the metal wiring layer 20 can be suppressed. In addition, as mentioned above, the wiring brazing material 50 has excellent wettability, which is one of the reasons why the generation of voids is suppressed in the metal wiring layer 20 formed with the wiring brazing material 50. Therefore, since the bonding strength of the metal wiring layer 20 with the ceramic substrate 10 has been improved, it is considered that a wiring brazing material 50 with a high degree of design freedom relative to the wiring layer thickness can be obtained.

[0053] Specifically, the metal wiring layer 20 in this embodiment has a cross-section of approximately 10,000 μm. 2It possesses the extremely excellent characteristic that no voids with an equivalent circular diameter of 8 μm or larger are observed within any given field of view. In other words, when the cross-section of the metal wiring 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 is less than one void per unit area, and the number of voids with an equivalent circular diameter of 4 μm or larger is 10,000 μm. 2 It is more preferable that there be less than one void per unit, and that the number of voids with an equivalent circular diameter of 1 μm or more is 10,000 μm. 2 It is even preferable that there be less than one per person.

[0054] In this embodiment, the metal wiring layer 20 is formed from the aforementioned wiring brazing material 50, resulting in high bonding strength between the metal wiring layer 20 and the ceramic substrate 10. Specifically, the shear strength of the metal wiring layer 20 in this embodiment is 20 MPa or greater. Furthermore, the tensile strength of the metal wiring layer 20 in this embodiment is 40 MPa or greater.

[0055] The shear strength of the metal wiring layer 20 as used here refers to the magnitude of the shear load per unit area required to cause the metal wiring layer 20 to break (shear fracture) when stress (shear stress) is applied to the metal wiring layer 20 in such a way that it causes the metal wiring layer 20 and the ceramic substrate 10 to shift in opposite directions along a direction parallel to the joint surface. The tensile strength of the metal wiring layer 20 refers to the magnitude of the tensile load per unit area required to cause the metal wiring layer 20 to break when stress (tensile stress) is applied to the metal wiring layer 20 in such a way that it pulls the metal wiring layer 20 and the ceramic substrate 10 apart along a direction perpendicular to the joint surface.

[0056] (3) Method for manufacturing ceramic wiring boards Next, the manufacturing method for the ceramic wiring board 100 described above will be explained.

[0057] As shown in Figure 2, wiring brazing material 50 for forming the metal wiring layer 20 is arranged on the ceramic substrate 10 in accordance with a predetermined wiring pattern. The wiring brazing material 50 has been described in (1) and (2), so its description is omitted here. Known methods such as screen printing, transfer, dispensing, inkjet, spray coating, sputtering, and vapor deposition can be used to arrange the wiring brazing material 50.

[0058] In this embodiment, even when the ceramic substrate 10 is made of an oxide such as alumina, the wiring brazing material 50 can be placed on the surface of the ceramic substrate 10 without forming a layer containing Mo or the like on the surface of the ceramic substrate 10 in advance.

[0059] After placing the wiring brazing material 50, the ceramic substrate 10 and the wiring brazing material 50 are heated and held in a predetermined atmosphere. This bonds the wiring brazing material 50 to the ceramic substrate 10, forming a metal wiring layer 20. The predetermined atmosphere can be any of the following: a vacuum atmosphere (reduced pressure atmosphere), an inert gas atmosphere, or a reducing atmosphere. By introducing an inert gas such as nitrogen (N2), the oxygen concentration can be adjusted. By introducing a reducing gas such as hydrogen (H2), copper oxide can be reduced, or oxidation of brazing material components such as Cu and Mg can be suppressed.

[0060] The heat treatment temperature is preferably, for example, 600°C to 950°C, more preferably 720°C to 900°C, and even more preferably 740°C to 850°C. By setting the heat treatment temperature to 950°C or lower, warping and residual stress due to differences in thermal expansion coefficients can be reduced. Furthermore, by setting the heat treatment temperature to 600°C or higher, the diffusivity of the active metal elements is improved, making it easier to form the interfacial reaction layer 21. Known furnaces such as stationary batch furnaces, multi-chamber furnaces, belt conveyor furnaces, and roller hearth kilns can be used as the heat treatment furnaces for joining.

[0061] Other conditions during joining include the following: Oxygen concentration: 0.01 ppm or more and 1000 ppm or less (more preferably 0.01 ppm or more and 100 ppm or less, even more preferably 0.01 ppm or more and 10 ppm or less) Retention time: There are no specific restrictions, but for example, 30 minutes to 180 minutes.

[0062] 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.

[0063] <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.

[0064] For example, in the above-described embodiment, the case in which the metal wiring layer 20 is formed on only one of the main surfaces (i.e., one side) of the ceramic substrate 10 was explained. However, as shown in Figure 3, the metal wiring layer 20 may be formed on both main surfaces (i.e., both sides) of the ceramic substrate 10. In this case, through holes 30 (also called vias) may be formed in the ceramic substrate 10, and the wiring brazing material 50 may also be filled into the through holes 30 with a metal similar to the metal forming the metal wiring layer 20. This allows the metal wiring layer 20 on the surface and the metal wiring layer 20 on the back surface to be electrically connected, thereby enabling the realization of a ceramic wiring substrate 100 with a more complex wiring pattern. Here, "a metal similar to the metal forming the metal wiring layer 20" refers to a metal composed of the same materials as the metal forming the metal wiring layer. Furthermore, since the wiring brazing material 50 has high wettability with respect to the ceramic substrate 10, it is easy to fill the through holes 30. Furthermore, since the interfacial reaction layer 21 is also formed around the through-hole 30, adhesion and strength are improved, making it possible to realize a ceramic wiring substrate 100 with a high degree of design freedom in the thickness of the metal wiring layer 20. [Examples]

[0065] (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 wiring brazing material 50, a paste was made by mixing each metal element 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 to correspond to the predetermined wiring pattern shape. Subsequently, samples 1 and 2 were prepared by heat treatment for 120 minutes at the predetermined heat treatment temperature and atmosphere shown in Table 1.

[0066] [Table 1]

[0067] (Cross-sectional tissue evaluation) The cross-sectional structures of samples 1 to 5 were observed using SEM. Figure 4 shows an external photograph of sample 5, and Figure 5 shows a cross-sectional SEM photograph. As shown in Figure 5, a metal wiring layer 20 was formed on the ceramic substrate 10, and it was confirmed that no significant voids with an equivalent circular diameter of 20 μm or more were present in the metal wiring layer 20. Furthermore, it was confirmed that an interfacial reaction layer 21 containing an active metal element (Ti in this case) was present between the ceramic substrate 10 and the metal wiring layer 20. For sample 1, an interfacial reaction layer 21 containing MgO was present. Samples in which an interfacial reaction layer 21 was confirmed between the ceramic substrate 10 and the metal wiring layer 20 are indicated with a "○" in the interfacial reaction layer column of Table 1.

[0068] (Joint strength evaluation) For samples 1 to 5, the bonding strength of the metal wiring layer 20 was evaluated by shear strength testing. Specifically, the metal wiring layer 20 was processed into a cylindrical shape with a diameter of 3 mm, and the bonding surface of the surrounding ceramic material was exposed to create a test specimen. With the ceramic substrate 10 of the test specimen fixed, the cylindrical metal wiring layer 20 was pressed using a displacement jig along a direction parallel to the bonding surface, and the magnitude of the stress at which the metal wiring layer 20 fractured (shear failure) was measured. Based on this value, the shear strength of the bonding layer was calculated. The shear test position (contact height H of the displacement jig) was set at a height of 200 μm from the exposed surface of the ceramic material, and the movement speed of the displacement axis was set to 100 μm / s. The results are shown in Table 1.

[0069] As shown in Table 1, the joint strength (shear strength of the metal wiring layer 20) of samples 1 to 5 was all 20 MPa or higher, confirming that they possess high joint strength.

[0070] Based on the above, it was confirmed that by using the aforementioned wiring brazing material 50, a ceramic wiring substrate 100 can be manufactured at a lower cost compared to when using a brazing material mainly composed of Ag. Furthermore, it was confirmed that the ceramic wiring substrate 100 has high bonding strength and is expected to allow for greater design flexibility in the thickness of the metal wiring layer 20.

[0071] <Preferred aspects of this disclosure> The following are preferred embodiments of this disclosure.

[0072] According to one aspect of this disclosure, Ceramic substrate and The ceramic substrate has a metal wiring layer formed on it, The aforementioned metal wiring layer is Cu and Mg and, At least one element selected from Sn, Sb, and Bi, A ceramic wiring substrate 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.

[0073] Preferably, Among the elements constituting the aforementioned metal wiring layer, Cu has the highest content. The content here is based on at%.

[0074] Preferably, In the aforementioned metal wiring layer, the Cu content is 40-85 at%, the Mg content is 0.2-25 at%, and the total content of Sn, Sb, and Bi is 1-25 at%.

[0075] Preferably, An interfacial reaction layer containing at least one of the active metal element compound or MgO is present between the ceramic substrate and the metal wiring layer.

[0076] Preferably, The metal wiring layer further comprises at least one element selected from Ag, In, and Mn.

[0077] Preferably, The metal wiring 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.

[0078] Preferably, The thickness of the metal wiring layer is between 5 μm and 300 μm.

[0079] Preferably, When observing the cross-section of the aforementioned metal wiring layer, the number of voids with an equivalent circular diameter of 8 μm or larger is 10,000 μm. 2 There is less than one per person.

[0080] Preferably, The ceramic substrate has through holes, The through-holes are filled with a metal similar to the metal forming the metal wiring layer.

[0081] According to other aspects of this disclosure, A wiring brazing material comprising Cu, Mg, at least one first element selected from Sn, Sb, and Bi, and at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, is arranged on a ceramic substrate in accordance with the wiring pattern. A method for manufacturing a ceramic wiring substrate is provided, comprising the step of heating and holding the ceramic substrate on which the wiring brazing material is arranged. Preferably, Among the elements that make up the aforementioned wiring brazing material, Cu has the highest content.

[0082] Preferably, In the step of arranging the wiring brazing material, a wiring brazing material containing 40-85 at% Cu, 1-25 at% Mg, a total of 1-25 at% of the first element, and a total of 0.1-10 at% of the active metal element is arranged.

[0083] Preferably, In the step of arranging the wiring brazing material, the wiring brazing material containing at least one second element selected from Ag, In, and Mn is arranged.

[0084] Preferably, In the step of arranging the wiring brazing material, when the Mg content is Xat% and the first element content is Yat%, wiring brazing material is arranged such that X-5 ≤ Y ≤ X+5.

[0085] Preferably, In the step of placing the wiring brazing material, a wiring brazing material containing Cu powder and an alloy powder formed from an intermetallic compound containing at least Mg, the first element, and the active metal element, and configured in a paste-like state, is placed.

[0086] Preferably, In the step of placing the wiring brazing material, the wiring brazing material is placed such that the Mg content derived from the alloy powder is 40% or more of the total Mg content in the wiring brazing material.

[0087] Preferably, In the heating and holding step, the heating is performed at a temperature of 600°C to 950°C.

[0088] According to other aspects of this disclosure, Cu and Mg and, A first element selected from Sn, Sb, and Bi, A wiring brazing material 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. Preferably, Among the elements that make up the aforementioned wiring brazing material, Cu has the highest content.

[0089] Preferably, It contains 40-85 at% Cu, 1-25 at% Mg, a total of 1-25 at% of the aforementioned first element, and a total of 0.1-10 at% of the aforementioned active metal element.

[0090] Preferably, It further contains at least one secondary element selected from Ag, In, and Mn. [Explanation of symbols]

[0091] 10 Ceramic substrates 20 Metal wiring layer 21 Interfacial reaction layer 22 Solid solution phase 23 Compound phase 30 Through holes 50 Brazing material for wiring 100 Ceramic Wiring Boards

Claims

1. Ceramic substrate and The ceramic substrate has a metal wiring layer formed on it, The aforementioned metal wiring layer is Cu and, Mg and, At least one element selected from Sn, Sb, and Bi, A ceramic wiring substrate comprising at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W.

2. The ceramic wiring substrate according to claim 1, wherein the Cu content is the highest among the elements constituting the metal wiring layer.

3. The ceramic wiring substrate according to claim 1, wherein the metal wiring layer has a Cu content of 40 to 85 at%, a Mg content of 0.2 to 25 at%, and a total content of Sn, Sb, and Bi of 1 to 25 at%.

4. The ceramic wiring substrate according to claim 1, wherein an interfacial reaction layer containing at least one of the active metal element compound or MgO is present between the ceramic substrate and the metal wiring layer.

5. The ceramic wiring substrate according to claim 1, wherein the metal wiring layer further comprises at least one element selected from Ag, In, and Mn.

6. The metal wiring layer comprises a solid solution phase formed by the solid solution of other metal elements in Cu, and Cu ４ A ceramic wiring substrate according to claim 1, comprising a compound phase having at least one intermetallic compound selected from MgSn, CuMgSb, and CuMgBi.

7. The ceramic wiring substrate according to claim 1, wherein the thickness of the metal wiring layer is 5 μm or more and 300 μm or less.

8. The ceramic substrate has through holes, The ceramic wiring substrate according to claim 1, wherein the through-holes are filled with a metal similar to the metal forming the metal wiring layer.

9. A wiring brazing material comprising Cu, Mg, at least one first element selected from Sn, Sb, and Bi, and at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, is arranged on a ceramic substrate in accordance with the wiring pattern. A method for manufacturing a ceramic wiring substrate, comprising the steps of heating and holding the ceramic substrate on which the wiring brazing material is arranged.

10. The method for manufacturing a ceramic wiring substrate according to claim 9, wherein the wiring brazing material has the highest Cu content among the elements constituting the wiring brazing material.

11. The method for manufacturing a ceramic wiring substrate according to claim 9, wherein in the step of arranging the wiring brazing material, a wiring brazing material containing 40 to 85 at% Cu, 1 to 25 at% Mg, a total of 1 to 25 at% of the first element, and a total of 0.1 to 10 at% of the active metal element is arranged.

12. The method for manufacturing a ceramic wiring substrate according to claim 11, wherein in the step of arranging the wiring brazing material, the wiring brazing material further contains at least one second element selected from Ag, In, and Mn.

13. The method for manufacturing a ceramic wiring substrate according to claim 9, wherein in the step of arranging the wiring brazing material, when the content of Mg is X at %, and the content of the first element is Ya at %, wiring brazing material such that X - 5 ≤ Y ≤ X + 5 is arranged.

14. The method for manufacturing a ceramic wiring substrate according to claim 9, wherein in the step of arranging the wiring brazing material, a wiring brazing material is arranged that contains Cu powder containing Cu, and an alloy powder formed from an intermetallic compound containing at least Mg, the first element, and the active metal element, and is configured in a paste-like state.

15. The method for manufacturing a ceramic wiring substrate according to claim 9, wherein the heating and holding step is performed at a temperature of 600°C or higher and 950°C or lower.

16. Cu and, Mg and, A first element selected from Sn, Sb, and Bi, A wiring brazing material comprising at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W.

17. The wiring brazing material according to claim 16, wherein the wiring brazing material has the highest Cu content among the elements constituting the wiring brazing material.

18. The wiring brazing material according to claim 16, comprising 40 to 85 at% of Cu, 1 to 25 at% of Mg, a total of 1 to 25 at% of the first element, and a total of 0.1 to 10 at% of the active metal element.

19. The wiring brazing material according to claim 18, further comprising at least one second element selected from Ag, In, and Mn.

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