Joining material and method for manufacturing the same, and solder joint and method for manufacturing the same

Abstract

Provided are: a joining material capable of suppressing generation of voids in a solder joint part; a method for manufacturing the same; a solder joint; and a method for manufacturing the same. A joining material 1A has a base metal layer 2A and a coating layer 3A covering at least one surface (Sa1 or Sa2) of the base metal layer 2A. The base metal layer 2A contains a first metal containing Sn and a second metal comprising an alloy containing Ni and Fe, and the coating layer contains a metal having a melting point lower than that of the second metal. The ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 or more as the ratio represented by the base metal layer / coating layer.

Description

Technical Field

[0001] The present invention relates to a bonding material, a method for producing the same, a solder joint, and a method for producing the same. This application claims priority based on Japanese Patent Application No. 2024-008258 filed in Japan on January 23, 2024, and the contents thereof are incorporated herein by reference.

Background Art

[0002] In recent years, with the increase in the operating temperature of power semiconductor devices using silicon carbide (SiC) or the like, the temperature at the solder joint site may reach about 250 to 280°C. Therefore, a high-temperature solder that does not melt during operation under such high-temperature conditions is required.

[0003] For the production of such high-temperature solder joints, preform solder is used as a soldering material. Preform solder is a molded product obtained by processing solder into various shapes such as a square shape, a ribbon shape, a disk shape, etc. As such preform solder, for example, a preform solder obtained by pressure molding a mixed powder of a metal powder of Sn and a metal powder composed of an alloy of Ni and Fe has been proposed (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described in Patent Document 1, preformed solder can suppress voids compared to TLP paste. However, when using preformed solder as described in Patent Document 1, there are areas on the bonding surface of the preformed solder that come into contact with the objects to be bonded where metal powder made of an alloy of Ni and Fe is exposed. Since the alloy of Ni and Fe has a high melting point and almost no wetting effect, a new problem has been discovered: voids are likely to occur at the solder joint.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a joining material and a method for manufacturing the same, as well as a solder joint and a method for manufacturing the same, which can suppress the generation of voids in solder joints. [Means for solving the problem]

[0007] The present invention includes the following embodiments. [1] A bonding material comprising a base metal layer and a coating layer covering at least one surface of the base metal layer, wherein the base metal layer contains a first metal containing Sn and a second metal consisting of an alloy containing Ni and Fe, the coating layer contains a metal with a lower melting point than the second metal, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 or more as expressed as the ratio of base metal layer / coating layer. [2] The bonding material according to [1], wherein the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 300 as expressed as the ratio of base metal layer / coating layer. [3] The bonding material according to [1] or [2], wherein the thickness of the coating layer is 1 to 150 μm. [4] The bonding material according to any one of [1] to [3], wherein both sides of the base metal layer are each covered with the coating layer. [5] The bonding material according to any one of [1] to [4], wherein the content of the second metal in the base metal layer is 1% by mass or more and 70% by mass or less with respect to the total mass of the first metal and the second metal, the content of a metal having a lower melting point than the second metal in the coating layer is 10% by mass or more and 100% by mass or less with respect to the total mass of the coating layer, and the content of the second metal in the coating layer is less than 15% by mass with respect to the total mass of the coating layer. [6] The bonding material according to any one of [1] to [5], wherein the base metal layer further contains a third metal whose entire surface is formed of a metal containing Ni. [7] The bonding material according to [6], wherein the Ni content in the Ni-containing metal forming the entire surface of the third metal is 50% by mass or more and 100% by mass or less with respect to the total mass of the metal forming the entire surface of the third metal, and the content of the third metal is 1 to 70% by mass with respect to the total mass of the first metal, the second metal and the third metal. [8] A bonding material comprising a base metal layer and a coating layer covering at least one surface of the base metal layer, wherein the base metal layer has a metal structure comprising a first phase which is a continuous phase and a second phase which is dispersed in the first phase, the first phase which is composed of a metal containing Sn, the second phase which is composed of an alloy which is composed of Ni and Fe, and the coating layer has a metal structure which comprises a metal phase which is composed of a metal which has a lower melting point than the alloy which is composed of Ni and Fe, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 or more as a ratio expressed as base metal layer / coating layer. [9] The joining material according to [8], wherein at least one surface of the base metal layer and the coating layer are pressed together. A solder joint formed using any one of the joining materials described in

[10] [1] to [9].

[11] A method for manufacturing a bonding material comprising a base metal layer and a coating layer covering at least one surface of the base metal layer, comprising the step of pressing the coating sheet onto at least one surface of a base metal sheet to cover the surface with the coating layer, wherein the base metal sheet contains a first metal containing Sn and a second metal consisting of an alloy containing Ni and Fe, the coating sheet contains a metal with a lower melting point than the second metal, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 or more as expressed as the ratio of base metal layer / coating layer.

[12] The method for manufacturing a bonding material according to

[11] , wherein the base metal layer further contains a third metal whose entire surface is formed of a metal containing Ni. A method for manufacturing a solder joint, comprising forming a joint between objects using a joining material manufactured by the method for manufacturing a joining material described in

[13] ,

[11] , or

[12] . [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a joining material and a method for manufacturing the same, as well as a solder joint and a method for manufacturing the same, which can suppress the generation of voids in solder joints. [Brief explanation of the drawing]

[0009] [Figure 1A] This is a perspective view of the bonding material 1A according to the first embodiment. [Figure 1B] This is a schematic diagram showing a cross-section in the thickness direction of the joining material 1A according to the first embodiment. [Figure 2A] This is an SEM image showing a cross-section in the thickness direction of the bonding material 1B according to the second embodiment. [Figure 2B] This is a schematic diagram showing a cross-section in the thickness direction of the joint material 1D obtained by the crimping process A in one embodiment of the method for manufacturing the joint material. [Figure 2C] This is a schematic diagram showing the crimping process B1 in one embodiment of a method for manufacturing a bonding material. [Figure 2D] This is a schematic diagram showing the crimping process B2 in one embodiment of a method for manufacturing a bonding material. [Figure 2E] In one embodiment of the method for manufacturing a bonding material, it is a schematic diagram showing the steps of the crimping step B3. [Figure 3] It is a schematic diagram showing a cross section of the third metal 30A in the bonding material according to the third embodiment. [Figure 4] It is a SEM image showing a cross section in the thickness direction of the bonding material 1C according to the fourth embodiment. [Figure 5] It is a schematic diagram showing a cross section of the third metal 30B in the bonding material according to the fifth embodiment.

Embodiments for Carrying Out the Invention

[0010] In this specification, "include" and "contain" are concepts that respectively encompass any of "comprise", "consist essentially of", and "consist of".

[0011] In this specification, "the first metal", "the second metal", "the third metal", and "the fourth metal" may each mean "particles formed of the first metal", "particles formed of the second metal", "particles formed of the third metal", and "particles formed of the fourth metal". In this specification, "the first metal powder", "the second metal powder", "the third metal powder", and "the fourth metal powder" may each mean "a group of particles formed of the first metal", "a group of particles formed of the second metal", "a group of particles formed of the third metal", and "a group of particles formed of the fourth metal". [[ID=​​​​​​​In FIG. 1B, Ta2 indicates the thickness of the base metal layer 2A, and Ta3 means the thickness of the coating layer 3A.

[0013] The base metal layer contains a first metal containing Sn and a second metal made of an alloy containing Ni and Fe. The coating layer contains a metal having a melting point lower than that of the second metal. The composition of the base metal layer is different from that of the coating layer.

[0014] [Base metal layer] The base metal layer contains a first metal containing Sn and a second metal made of an alloy containing Ni and Fe.

[0015] [First metal] The first metal contains Sn. Since Sn has excellent ductility, the first metal containing Sn can eliminate the voids between the first metals by plastic deformation. In addition, the first metal containing Sn can ensure general properties such as wettability as a soldering material.

[0016] The first metal may contain a metal other than Sn. Examples of the metal other than Sn that the first metal may contain include Ag, Cu, In, Bi, Ni, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, and As. These metals other than Sn may contain one kind or two or more kinds. The group of metals other than Sn can be arbitrarily selected from these metals.

[0017] The metal that the first metal may contain may be each simple substance of Sn and the metal other than Sn, or may be an alloy of Sn and the simple substance of the metal other than Sn.

[0018] The first metal may be, for example, simple Sn, a mixture of Sn and a metal other than Sn, an alloy of Sn and a metal other than Sn, or a mixture of an alloy containing Sn and another metal.

[0019] The first metal may contain unavoidable impurities in addition to the aforementioned metals. Even if it contains unavoidable impurities, this does not affect the effects of the present invention. The first metal may be one type or two or more types.

[0020] The melting point of the first metal is preferably 300°C or lower, but may also be 250°C or lower, or 116 to 200°C. If the melting point of the first metal is below the upper limit of the preferred range mentioned above, it becomes easier to ensure the wettability of the solder.

[0021] In this specification, "melting point of the metal to be measured, or melting point of the metal powder to be measured" refers to the melting point measured by differential scanning calorimetry (DSC). The melting point of the metal to be measured means the temperature at which the heat absorbed per unit time is highest, based on the results of the DSC measurement of the metal to be measured. If the metal to be measured has one peak in the DSC measurement, the melting point of the metal to be measured means the temperature of the top of that peak. If the metal to be measured has multiple peaks in the DSC measurement, the melting point of the metal to be measured means the temperature of the peak top with the highest heat absorbed per unit time among the multiple peak tops. The same applies to the melting point of the metal powder being measured. The melting points of the first and fourth metals can be measured using, for example, the DSC7020 manufactured by Hitachi High-Tech Science Corporation. The melting points of the second and third metals, which will be described later, can be measured using, for example, the DSC404-F3Pegasus manufactured by NETZSCH.

[0022] The Sn content in the first metal is preferably 20% by mass or more and 100% by mass or less, relative to the total mass of the first metal. For the properties of Sn to be fully exhibited, the Sn content in the first metal is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 100% by mass, relative to the total mass of the first metal.

[0023] <Second metal> The second metal consists of an alloy containing Ni and Fe. The alloy in the second metal preferably contains Ni and Fe, has a higher melting point than the first metal, and is dispersed within the base metal layer. The melting point of the alloy in the second metal is preferably above 300°C, more preferably above 500°C, and even more preferably between 600°C and 1600°C. If the melting point of the alloy in the second metal exceeds the lower limit of the preferred range mentioned above, it becomes easier to increase the shear strength of the solder joint even in high-temperature operating environments.

[0024] The alloy in the second metal may contain metals other than Ni and Fe. That is, the second metal may be an alloy of Ni and Fe, or an alloy of Ni, Fe, and other metals, and among these, an alloy of Ni and Fe is preferred.

[0025] Examples of metals other than Ni and Fe that may be included as the second metal include Sn, Ag, Cu, In, Bi, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Mn, Zr, and As. These metals other than Ni and Fe may be included individually or in combination of two or more. The group of metals other than Ni and Fe can be arbitrarily selected from these metals.

[0026] The second metal may contain unavoidable impurities in addition to the aforementioned metals. Even if it contains unavoidable impurities, this does not affect the effects of the present invention. The second metal may be one type or two or more types.

[0027] The Ni content in the second metal is preferably 80% to 99% by mass, and more preferably 85% to 95% by mass, relative to the total mass of the second metal. The Fe content in the second metal is preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, relative to the total mass of the second metal. When the Ni and Fe content in the second metal is within the preferred range described above, intermetallic compounds are formed at an earlier stage, and the generation of voids can be suppressed.

[0028] In this specification, "particle size of metal, or particle size of metal powder" refers to the average particle size measured on a volume basis using a laser diffraction / scattering particle size distribution analyzer. The average particle size can be measured, for example, using a laser diffraction / scattering particle size distribution analyzer (MT3300EXII) manufactured by Microtrac-Bell.

[0029] The second metal preferably has a particle size of 0.1 to 1000 μm, more preferably 1 to 100 μm, and even more preferably 5 to 50 μm. If the particle size of the second metal is above the lower limit of the preferred range, wettability is easier to ensure, and if it is below the upper limit of the preferred range, intermetallic compounds are more easily formed.

[0030] <Relationship between the content of primary and secondary metals> In the base metal layer of the bonding material according to the first embodiment, the content of the first metal is preferably 30% by mass, 60% by mass, 80% by mass, 90% by mass, or 97% by mass, relative to the total mass (100% by mass) of the first and second metals, and the upper and lower limits can be appropriately selected from these values. The content of the first metal may be 30 to 99% by mass or 30 to 97% by mass, based on the total mass (100% by mass) of the first and second metals.

[0031] In the base metal layer of the bonding material according to the first embodiment, the content of the second metal is preferably 3% by mass, 10% by mass, 20% by mass, 40% by mass, or 70% by mass, relative to the total mass (100% by mass) of the first metal and the second metal, and the upper and lower limits can be appropriately selected from these values. The content of the second metal may be 1 to 70% by mass or 3 to 70% by mass, relative to the total mass (100% by mass) of the first and second metals. The heat resistance of the solder joint is further improved when the content of the second metal is within the aforementioned preferred range.

[0032] In the base metal layer of the bonding material according to the first embodiment, the sum of the content of the first metal and the content of the second metal does not exceed 100% by mass.

[0033] In the base metal layer of the bonding material according to the first embodiment, the ratio of the content of the first metal to the content of the second metal is preferably 0.43 and 32 as a mass ratio expressed as the content of the first metal / the content of the second metal, and the upper and lower limits can be appropriately selected from these values. The mass ratio expressed as the content of the first metal / the content of the second metal may be 0.1 or more and 100 or less, or 0.4 or more and 35 or less. When the mass ratio expressed as the content of the first metal / the content of the second metal is within the aforementioned preferred range, voids in the solder joint are more easily suppressed, and the heat resistance of the solder joint is further improved.

[0034] In the base metal layer of the bonding material according to the first embodiment, the total content of the first metal and the second metal is preferably 60% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, even more preferably 90% by mass or more and 100% by mass or less, and may be 100% by mass, based on the total mass of the base metal layer.

[0035] The thickness of the base metal layer is preferably 150 μm, 250 μm, 290 μm, 298 μm, 299 μm, or 1500 μm, and the upper and lower limits can be appropriately selected from these values. The thickness of the base metal layer may be, for example, 5 to 5000 μm, 150 to 1500 μm, or 150 to 290 μm. If the thickness of the base metal layer is greater than or equal to the lower limit, it becomes easier to improve the heat resistance of the solder joint. If it is less than or equal to the upper limit, it becomes easier to suppress the generation of voids in the solder joint that comes into contact with the object being joined.

[0036] The thickness of the base metal layer can be, for example, 1-5000 μm, 3-5000 μm, 5-5000 μm, 10-5000 μm, 15-5000 μm, 20-5000 μm, 25-5000 μm, 30-5000 μm, 40-5000 μm, 50-5000 μm, 75-5000 μm, 100-500 μm. 0μm, 125~5000μm, 150~5000μm, 175~5000μm, 200~5000μm, 250~5000μm, 290~5 000μm, 300~5000μm, 350~5000μm, 400~5000μm, 500~5000μm, 750~5000μm, 100 0~5000μm, 1200~5000μm, 1500~5000μm, 1~4000μm, 1~3500μm, 1~3000μm, 1~25 00μm, 1~2000μm, 1~1500μm, 1~1200μm, 1~1000μm, 1~750μm, 1~500μm, 1~400μm The particle sizes may also be 1-350 μm, 1-300 μm, 1-290 μm, 1-250 μm, 1-200 μm, 1-175 μm, 1-150 μm, 1-125 μm, 1-100 μm, 1-75 μm, 1-50 μm, 1-40 μm, 1-30 μm, 1-25 μm, 1-20 μm, and 1-15 μm. If the thickness of the base metal layer is greater than or equal to the lower limit, it becomes easier to improve the heat resistance of the solder joint. If it is less than or equal to the upper limit, it becomes easier to suppress the generation of voids in the solder joint that comes into contact with the object being joined.

[0037] [Coating layer] The coating layer contains a metal with a lower melting point than the alloy containing Ni and Fe that forms the secondary metal. The metal forming the coating layer forms compounds with the metals that make up the objects being joined. The melting point of the metal with a lower melting point than the second metal is preferably 300°C or lower, but may also be 250°C or lower, or 78 to 200°C.

[0038] Examples of metals with a lower melting point than the second metal include metals containing Sn and metals containing In. The coating layer may also contain metals other than Sn and In. The metals that the coating layer may contain may be elemental metals other than Sn and In, or alloys of Sn, In and elemental metals other than Sn and In.

[0039] The coating layer may be pure Sn, a mixture of Sn and a metal other than Sn, an alloy of Sn and a metal other than Sn, or a mixture of an alloy containing Sn and a metal other than Sn. Furthermore, the coating layer may be pure In, a mixture of In and a metal other than In, an alloy of In and a metal other than In, or a mixture of an alloy containing In and a metal other than In.

[0040] When the coating layer contains Sn, other metals that may be included include, for example, Ag, Cu, In, Bi, Ni, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, and As. The other metals may be included individually or in combination of two or more types. The group of metals other than Sn can be arbitrarily selected from these metals. Furthermore, if the coating layer contains In, other metals that may be included include, for example, Sn, Ag, Cu, Bi, Ni, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, and As. The other metals may be included individually or in combination of two or more. The group of metals other than In can be arbitrarily selected from these metals.

[0041] The coating layer may contain unavoidable impurities in addition to the aforementioned metals. Even if unavoidable impurities are present, this does not affect the effects of the present invention.

[0042] When the coating layer contains Sn, the Sn content in the coating layer is preferably 10% by mass or more and 100% by mass or less, relative to the total mass of the coating layer. In order for the properties of Sn to be fully exhibited, the Sn content in the solder is preferably 40% by mass or more, more preferably 60% by mass or more, particularly preferably 80% by mass or more, most preferably 90% by mass or more, and may also be 95% by mass or more, or 100% by mass. Furthermore, if the coating layer contains In, the In content in the coating layer is preferably 10% by mass or more and 100% by mass or less relative to the total mass of the coating layer. In order for the properties of In to be fully exhibited, the In content in the solder is preferably 20% by mass or more, more preferably 40% by mass or more, particularly preferably 60% by mass or more, most preferably 80% by mass or more, and may even be 100% by mass.

[0043] The coating layer may or may not contain the second metal mentioned above in the [base metal layer], and it is preferable that it does not contain it. If the coating layer contains a second metal, the content of the second metal in the coating layer is preferably less than 15% by mass, more preferably 10% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.1% by mass or less, based on the total mass of the coating layer.

[0044] The thickness of the coating layer is preferably 1 μm, 3 μm, 5 μm, 10 μm, 25 μm, 30 μm, 50 μm, 75 μm, 100 μm, or 150 μm, and the upper and lower limits can be appropriately selected from these values. The thickness of the coating layer may be, for example, 1 to 150 μm, 3 to 100 μm, 1 to 75 μm, or 5 to 75 μm. If the thickness of the coating layer is greater than or equal to the lower limit, it becomes easier to suppress the occurrence of voids in the solder joint that comes into contact with the objects being joined. If it is less than or equal to the upper limit, it becomes easier to improve the heat resistance of the solder joint.

[0045] The thickness of the coating layer may be, for example, 1-150 μm, 3-150 μm, 5-150 μm, 7.5-150 μm, 10-150 μm, 12.5-150 μm, 15-150 μm, 20-150 μm, 25-150 μm, 30-150 μm, 40-150 μm, 50-150 μm, 75-150 μm, 1-125 μm, 1-100 μm, 1-75 μm, 1-50 μm, 1-40 μm, 1-30 μm, 1-25 μm, 1-20 μm, 1-15 μm, 1-12.5 μm, 1-10 μm, 1-7.5 μm, 1-5 μm, or 1-3 μm. If the thickness of the coating layer is greater than or equal to the lower limit, it becomes easier to suppress the occurrence of voids in the solder joint that comes into contact with the objects being joined. If it is less than or equal to the upper limit, it becomes easier to improve the heat resistance of the solder joint.

[0046] In this specification, "thickness of the coating layer" means the thickness of the coating layer covering one side of the base metal layer. That is, even if both sides of the base metal layer are covered with a coating layer, "thickness of the coating layer" means the thickness of the coating layer that covers one side of the base metal layer.

[0047] The number of coating layers covering one side of the base metal layer may be one layer or two layers. If there are two or more coating layers covering one side of the base metal layer, the thickness of the coating layer covering one side refers to the sum of the thicknesses of all the coating layers covering that side.

[0048] When both sides of a base metal layer are covered with a coating layer, the number of layers and composition of the coating layer on one side may differ from the number of layers and composition of the coating layer on the other side.

[0049] The thickness of the bonding material is preferably 300 μm or 1510 μm, and the upper and lower limits can be appropriately selected from these values. The thickness of the bonding material may be, for example, 10 to 5300 μm or 20 to 1510 μm.

[0050] The thickness of the bonding material can be, for example, 2-5300μm, 2-4000μm, 2-3000μm, 2-2000μm, 2-1750μm, 2-1510μm, 2-1200μm, 2-1000μm, 2-750μm, 2-500μm, 2-400μm, 2-300μm, 2-250μm, 2-200μm, 2-150μm, 2-100μm, 2-75μm, 2-50μm, 2-40μm, 2-30μm, 5-5300μm, 10 These are examples of the following: ~5300μm, 15~5300μm, 20~5300μm, 30~5300μm, 40~5300μm, 50~5300μm, 75~5300μm, 100~5300μm, 150~5300μm, 200~5300μm, 250~5300μm, 300~5300μm, 400~5300μm, 500~5300μm, 750~5300μm, 1000~5300μm, and 1200~5300μm.

[0051] In this specification, the ratio of the thickness of the base metal layer to the thickness of the coating layer refers to the ratio expressed as base metal layer (μm) / coating layer (μm).

[0052] The ratio of the thickness of the base metal layer to the thickness of the coating layer, expressed as base metal layer / coating layer, is preferably 2, 10, 58, 298, 299, or 300, and the upper and lower limits can be appropriately selected from these values. The ratio expressed as base metal layer / coating layer may be, for example, 1 to 500, 2 to 300, 2 to 100, or 2 to 58. By keeping the ratio of the base metal layer to the coating layer within the above range, it becomes easier to improve the heat resistance of the solder joint and to further suppress the generation of voids in the solder joint that comes into contact with the object being joined.

[0053] The ratio of the thickness of the base metal layer to the thickness of the coating layer may be expressed as a ratio of base metal layer / coating layer, for example, 2-500, 3-500, 5-500, 7.5-500, 10-500, 15-500, 20-500, 30-500, 50-500, 100-500, 200-500, 2-400, 2-350, 2-300, 2-250, 2-200, 2-150, 2-100, 2-75, 2-60, 2-58, 2-50, 2-30, 2-20, 2-15, 2-10, 2-7.5, 2-5, or 2-3. When the ratio of the base metal layer to the coating layer is within the above range, it becomes easier to improve the heat resistance of the solder joint and to further suppress the generation of voids in the solder joint that is in contact with the object being joined. When it is above the lower limit of the above range, it becomes easier to improve the heat resistance of the solder joint. When it is below the upper limit of the above range, it becomes easier to suppress the generation of voids in the solder joint.

[0054] With respect to the bonding material according to the first embodiment, the above-mentioned provisions regarding the thickness of the base metal layer and the coating layer, the ratio of the thickness of the base metal layer to the thickness of the coating layer, and the content of the first metal and the second metal may be combined in any way.

[0055] Hereinafter, the ratio of the thickness of the base metal layer to the thickness of the coating layer refers to the ratio expressed as base metal layer (μm) / coating layer (μm). The bonding material according to the first embodiment preferably has a coating layer thickness of 1 to 150 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 300, more preferably has a coating layer thickness of 5 to 150 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 200, even more preferably has a coating layer thickness of 5 to 150 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 100, and particularly preferably has a coating layer thickness of 5 to 75 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 60. When the thickness of the coating layer is within the above range, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is within the above range, it becomes easier to improve the heat resistance of the solder joint and to suppress the generation of voids in the solder joint.

[0056] The bonding material according to the first embodiment preferably has a base metal layer thickness of 150 to 1500 μm, a coating layer thickness of 1 to 150 μm, a ratio of the base metal layer thickness to the coating layer thickness of 2 to 500 (expressed as base metal layer / coating layer), a first metal content of 30 to 97% by mass relative to the total mass (100% by mass) of the first and second metals, a second metal content of 3 to 70% by mass relative to the total mass (100% by mass) of the first and second metals, and a ratio of the first metal content to the second metal content of 0.4 to 35 (expressed as first metal content / second metal content). In the bonding material according to the first embodiment, the thickness of the base metal layer is preferably 150 to 290 μm, the thickness of the coating layer is 5 to 100 μm, the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 58 as expressed as base metal layer / coating layer, the content of the first metal is 30 to 97% by mass relative to the total mass (100% by mass) of the first and second metals, the content of the second metal is 3 to 70% by mass relative to the total mass (100% by mass) of the first and second metals, and the ratio of the content of the first metal to the content of the second metal is 0.4 or more and 35 or less as expressed as the mass ratio of the content of the first metal / content of the second metal.

[0057] In the bonding material according to the first embodiment, the thickness of the base metal layer is preferably 1 to 5000 μm, the thickness of the coating layer is preferably 1 to 150 μm, the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 500 as expressed as base metal layer / coating layer, the content of the first metal is 30 to 97% by mass relative to the total mass (100% by mass) of the first and second metals, the content of the second metal is 3 to 70% by mass relative to the total mass (100% by mass) of the first and second metals, and the ratio of the content of the first metal to the content of the second metal is 0.4 or more and 35 or less as expressed as the mass ratio of the content of the first metal / content of the second metal.

[0058] In the bonding material according to the first embodiment, the thickness of the base metal layer is preferably 1 to 2000 μm, the thickness of the coating layer is 1 to 100 μm, the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 500 as expressed as base metal layer / coating layer, the content of the first metal is 30 to 97% by mass relative to the total mass (100% by mass) of the first and second metals, the content of the second metal is 3 to 70% by mass relative to the total mass (100% by mass) of the first and second metals, and the ratio of the content of the first metal to the content of the second metal is 0.4 or more and 35 or less as expressed as the mass ratio of the content of the first metal / content of the second metal.

[0059] For the manufacture of the bonding material according to the first embodiment, known manufacturing methods can be used, such as hot-dip galvanizing and rolling.

[0060] ■Explanation of Effects■ The bonding material according to the first embodiment described above comprises a base metal layer and a coating layer that covers at least one surface of the base metal layer. The bonding material, by having a coating layer, can suppress the generation of voids at the solder joint. The reason for this effect is as follows. On the surface of a substrate metal layer containing metal powder made of an alloy of Ni and Fe, there are areas where the metal powder made of the Ni-Fe alloy is exposed. Because the Ni-Fe alloy has a high melting point and extremely low wetting properties, voids are likely to occur at solder joints. Since the coating layer covers the base metal layer so that the Ni-Fe alloy is not exposed on the surface of the base metal layer, it is possible to suppress the generation of voids at the joint when joining objects to be joined using the joining material according to the first embodiment.

[0061] (Joining material: Second embodiment) Figure 2A is an SEM image showing a cross-section in the thickness direction of an example of a bonding material according to the second embodiment. In Figure 2A, the bonding material 1B has a base metal layer 2B and a coating layer 3B that covers both surfaces of the base metal layer 2B. The substrate metal layer 2B shown in Figure 2A has a metal structure comprising a first phase 10 which is a continuous phase and a second phase 20 which is dispersed in the first phase. The coating layer 3B shown in Figure 2A has a metallic structure comprising a metallic phase composed of a metal with a lower melting point than the alloy containing Ni and Fe. The composition of the base metal layer 2B is different from the composition of the coating layer 3B.

[0062] The bonding material 1B illustrated in Figure 2A is the bonding material of Example C1 described later in the Examples. Bonding material 1B has a base metal layer thickness of 150 μm and a coating layer thickness of 75 μm. In the base metal layer 2B, the content of the first phase is 80% by mass relative to the total mass of the base metal layer, and the content of the second phase is 20% by mass relative to the total mass of the base metal layer. The Ni content in the second phase is 90% by mass relative to the total mass of the second phase, and the Fe content in the second phase is 10% by mass relative to the total mass of the second phase.

[0063] The bonding material 1B shown in Figure 2A is a clad material in which a coating layer is bonded to both sides of a base metal layer. In the clad material, an intermetallic compound may be formed in the area where the base metal layer and the coating layer are in contact. As will be described later, the joining material according to the second embodiment can be manufactured, for example, by pressing together a base metal sheet, which is the material for the base metal layer, and a coating sheet, which is the material for the coating layer.

[0064] As described later, the base metal sheet can be manufactured by methods such as rolling, using metal powder containing, for example, a first metal containing Sn and a second metal consisting of an alloy containing Ni and Fe as raw materials. The base metal sheet can also be described as preformed solder.

[0065] [Base metal layer] In the base metal layer 2B, the first phase 10 is a continuous phase and is composed of a metal containing Sn. The description of the metal containing Sn and its content is the same as that of the <first metal> in the above embodiment. Furthermore, in the first phase 10, grain boundaries may exist between the metal crystals containing Sn.

[0066] The overall melting point of the metals constituting the first phase can be measured in the same manner as the melting point of the first metal. If the first phase contains multiple types of metals, the temperature of the peak top with the highest heat absorption per unit time among the multiple peak tops that the multiple types of metals constituting the first phase may have is adopted as the overall melting point of the metals constituting the first phase. The melting point of the metal constituting the second phase as a whole is defined similarly. The melting point of the metal as a whole that forms the entire surface of the third phase is similarly defined. If the entire third phase has a uniform composition, the melting point of the metals constituting the third phase as a whole is similarly defined. If the third phase has a structure consisting of a core and a surface layer covering the core, the melting point of the metal forming the surface layer of the third phase as a whole is defined similarly, and the melting point of the metal forming the core of the third phase as a whole is also defined similarly.

[0067] The explanation for the melting point of the metal constituting the first phase as a whole is the same as the explanation for the melting point of the first metal.

[0068] In the base metal layer 2B, the second phase 20 is dispersed in the first phase 10. The second phase 20 is composed of an alloy containing Ni and Fe. The description of the alloy containing Ni and Fe, its particle size, and its content is the same as that of the <second metal> in the first embodiment.

[0069] The explanation for the melting point of the alloy constituting the second phase is the same as the explanation for the melting point of the second metal.

[0070] In this specification, the particle size of a phase can be measured and calculated from the cross-sectional structure containing that phase using an optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM), etc. The particle size of a phase can also be calculated by measuring the diameters of three or more phases and taking their average value.

[0071] The particle size of the second phase can be the particle size of the second metal powder prepared to form the second phase.

[0072] In this specification, "containment of metals constituting the phase" means "total content of metals constituting the phase."

[0073] In the base metal layer, the mixing ratio of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase is preferably 30% by mass, 60% by mass, 80% by mass, 90% by mass, or 97% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase. The upper and lower limits can be appropriately selected from these values. The content of the second metal may be 30-99% by mass or 30-97% by mass.

[0074] In the base metal layer, the content of the alloy constituting the second phase is preferably 3% by mass, 10% by mass, 20% by mass, 40% by mass, or 70% by mass, relative to the total mass (100% by mass) of the metal containing Sn constituting the first phase and the alloy containing Ni and Fe constituting the second phase. The upper and lower limits can be appropriately selected from these values. The content of the alloy constituting the second phase may be 1 to 70% by mass, or 3 to 70% by mass, relative to the total mass (100% by mass) of the metal containing Sn constituting the first phase and the alloy containing Ni and Fe constituting the second phase. The heat resistance of the solder joint is further improved by ensuring that the content of the alloy constituting the second phase is within the aforementioned preferred range.

[0075] In the base metal layer of the bonding material according to the second embodiment, the total content of the metal containing Sn that constitutes the first phase and the alloy that constitutes the second phase does not exceed 100% by mass.

[0076] In the base metal layer of the bonding material according to the second embodiment, the ratio of the content of the metal containing Sn constituting the first phase to the content of the alloy containing Ni and Fe constituting the second phase is preferably 0.43 and 32 as a mass ratio expressed as first phase / second phase, and the upper and lower limits can be appropriately selected from these values. The mass ratio expressed as first phase / second phase is preferably 0.1 or more and 100 or less, and more preferably 0.4 or more and 35 or less. When the mass ratio of the first phase to the second phase is within the aforementioned preferred range, voids in the solder joint are more easily suppressed, and the heat resistance of the solder joint is further improved.

[0077] In the base metal layer of the bonding material according to the second embodiment, the total content of the metal containing Sn that constitutes the first phase and the alloy containing Ni and Fe that constitutes the second phase is preferably 60% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, even more preferably 90% by mass or more and 100% by mass or less, and may be 100% by mass, based on the total mass of the base metal layer.

[0078] In the bonding material according to the second embodiment, the description of the thickness of the base metal layer and the coating layer is the same as in the first embodiment.

[0079] The thickness of the base metal layer of the bonding material according to the second embodiment is preferably 150 μm, 250 μm, 290 μm, 298 μm, 299 μm, or 1500 μm, and the upper and lower limits can be appropriately selected from these values. The thickness of the base metal layer may be, for example, 5 to 5000 μm, 150 to 1500 μm, or 150 to 290 μm. If the thickness of the base metal layer is greater than or equal to the lower limit, it becomes easier to improve the heat resistance of the solder joint. If it is less than or equal to the upper limit, it becomes easier to suppress the generation of voids in the solder joint that comes into contact with the object being joined.

[0080] The thickness of the base metal layer of the bonding material according to the second embodiment is, for example, 1-5000 μm, 3-5000 μm, 5-5000 μm, 10-5000 μm, 15-5000 μm, 20-5000 μm, 25-5000 μm, 30-5000 μm, 40-5000 μm, 50-5000 μm, 75-5000 μm μm, 100~5000μm, 125~5000μm, 150~5000μm, 175~5000μm, 200~5000μm, 250~5000 μm, 290~5000μm, 300~5000μm, 350~5000μm, 400~5000μm, 500~5000μm, 750~5000 μm, 1000~5000μm, 1200~5000μm, 1500~5000μm, 1~4000μm, 1~3500μm, 1~3000μm , 1~2500μm, 1~2000μm, 1~1500μm, 1~1200μm, 1~1000μm, 1~750μm, 1~500μm, 1~40 The particle sizes may also be 0 μm, 1-350 μm, 1-300 μm, 1-290 μm, 1-250 μm, 1-200 μm, 1-175 μm, 1-150 μm, 1-125 μm, 1-100 μm, 1-75 μm, 1-50 μm, 1-40 μm, 1-30 μm, 1-25 μm, 1-20 μm, and 1-15 μm. If the thickness of the base metal layer is greater than or equal to the lower limit, it becomes easier to improve the heat resistance of the solder joint. If it is less than or equal to the upper limit, it becomes easier to suppress the generation of voids in the solder joint that comes into contact with the object being joined.

[0081] [Coating layer] The coating layer 3B has a metallic structure comprising a metallic phase composed of a metal with a lower melting point than the alloy containing Ni and Fe. The description of the metal with a lower melting point than the alloy containing Ni and Fe, its content, etc., is the same as that for the metal with a lower melting point than the alloy containing Ni and Fe in the first embodiment. The metal and its content that form the coating layer in the bonding material according to the second embodiment are the same as the metal and its content that form the coating layer in the bonding material according to the first embodiment.

[0082] In the bonding material according to the second embodiment, the explanation regarding the number of coating layers and the thickness of the coating layers is the same as in the first embodiment.

[0083] The coating layer may or may not have the second phase described above in the [base metal layer], and it is preferable that it does not have the second phase. If the coating layer has a second phase, the content of the alloy containing Ni and Fe that constitutes the second phase in the coating layer is preferably less than 15% by mass, more preferably 10% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.1% by mass or less, based on the total mass of the coating layer.

[0084] The thickness of the coating layer is preferably 1 μm, 3 μm, 5 μm, 10 μm, 25 μm, 30 μm, 50 μm, 75 μm, 100 μm, or 150 μm, and the upper and lower limits can be appropriately selected from these values. For example, it may be 1 to 150 μm, 3 to 100 μm, 1 to 75 μm, or 5 to 75 μm. If the thickness of the coating layer is greater than or equal to the lower limit, it becomes easier to suppress the generation of voids in the solder joint that is in contact with the object to be joined. If it is less than or equal to the upper limit, it becomes easier to improve the heat resistance of the solder joint.

[0085] The thickness of the coating layer of the bonding material according to the second embodiment may be, for example, 1-150 μm, 3-150 μm, 5-150 μm, 7.5-150 μm, 10-150 μm, 12.5-150 μm, 15-150 μm, 20-150 μm, 25-150 μm, 30-150 μm, 40-150 μm, 50-150 μm, 75-150 μm, 1-125 μm, 1-100 μm, 1-75 μm, 1-50 μm, 1-40 μm, 1-30 μm, 1-25 μm, 1-20 μm, 1-15 μm, 1-12.5 μm, 1-10 μm, 1-7.5 μm, 1-5 μm, or 1-3 μm. If the thickness of the coating layer is greater than or equal to the lower limit, it becomes easier to suppress the occurrence of voids in the solder joint that comes into contact with the objects being joined. If it is less than or equal to the upper limit, it becomes easier to improve the heat resistance of the solder joint.

[0086] The thickness of the bonding material is preferably 300 μm or 1510 μm, and the upper and lower limits can be appropriately selected from these values. The thickness of the bonding material may be, for example, 10 to 5300 μm or 20 to 1510 μm.

[0087] The thickness of the bonding material according to the second embodiment is, for example, 2-5300 μm, 2-4000 μm, 2-3000 μm, 2-2000 μm, 2-1750 μm, 2-1510 μm, 2-1200 μm, 2-1000 μm, 2-750 μm, 2-500 μm, 2-400 μm, 2-300 μm, 2-250 μm, 2-200 μm, 2-150 μm, 2-100 μm, 2-75 μm, 2-50 μm, 2-40 μm, 2-30 μm, 5-5300 μm The microparticle sizes are as follows: μm, 10-5300 μm, 15-5300 μm, 20-5300 μm, 30-5300 μm, 40-5300 μm, 50-5300 μm, 75-5300 μm, 100-5300 μm, 150-5300 μm, 200-5300 μm, 250-5300 μm, 300-5300 μm, 400-5300 μm, 500-5300 μm, 750-5300 μm, 1000-5300 μm, and 1200-5300 μm.

[0088] The ratio of the thickness of the base metal layer to the thickness of the coating layer, expressed as base metal layer / coating layer, is preferably 2, 10, 58, 298, 299, or 300, and the upper and lower limits can be appropriately selected from these values. The ratio expressed as base metal layer / coating layer may be, for example, 1 to 500, 2 to 300, 2 to 100, or 2 to 58. By keeping the ratio of the base metal layer to the coating layer within the above range, it becomes easier to improve the heat resistance of the solder joint and to further suppress the generation of voids in the solder joint that comes into contact with the object being joined.

[0089] In the bonding material according to the second embodiment, the ratio of the thickness of the base metal layer to the thickness of the coating layer may be expressed as a ratio of base metal layer / coating layer, for example, 2-500, 3-500, 5-500, 7.5-500, 10-500, 15-500, 20-500, 30-500, 50-500, 100-500, 200-500, 300-500, 2-400, 2-350, 2-300, 2-250, 2-200, 2-150, 2-100, 2-75, 2-60, 2-58, 2-50, 2-30, 2-20, 2-15, 2-10, 2-7.5, 2-5, or 2-3. When the ratio of the base metal layer to the coating layer is within the above range, it becomes easier to improve the heat resistance of the solder joint and to further suppress the generation of voids in the solder joint that is in contact with the object being joined. When it is above the lower limit of the above range, it becomes easier to improve the heat resistance of the solder joint. When it is below the upper limit of the above range, it becomes easier to suppress the generation of voids in the solder joint.

[0090] With respect to the bonding material according to the second embodiment, the above-mentioned provisions regarding the thickness of the base metal layer and the coating layer, the ratio of the thickness of the base metal layer to the thickness of the coating layer, the content of the metal containing Sn that constitutes the first phase and the alloy containing Ni and Fe that constitutes the second phase may be combined in any way.

[0091] Hereinafter, the ratio of the thickness of the base metal layer to the thickness of the coating layer refers to the ratio expressed as base metal layer (μm) / coating layer (μm). The bonding material according to the second embodiment preferably has a coating layer thickness of 1 to 150 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 300, more preferably has a coating layer thickness of 5 to 150 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 200, even more preferably has a coating layer thickness of 5 to 150 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 100, and particularly preferably has a coating layer thickness of 5 to 75 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 60. When the thickness of the coating layer is within the above range, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is within the above range, it becomes easier to improve the heat resistance of the solder joint and to suppress the generation of voids in the solder joint.

[0092] The bonding material according to the second embodiment preferably has a base metal layer thickness of 150 to 1500 μm, a coating layer thickness of 1 to 150 μm, a ratio of the base metal layer thickness to the coating layer thickness of 2 to 500 as expressed as base metal layer / coating layer, a content of Sn-containing metal constituting the first phase of 30 to 97% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase, a content of Ni and Fe-containing alloy constituting the second phase of 3 to 70% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase, and a mass ratio of 0.4 to 35 as expressed as first metal content / second metal content. In the bonding material according to the second embodiment, more preferably, the thickness of the base metal layer is 150 to 290 μm, the thickness of the coating layer is 5 to 100 μm, the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 58 as expressed as base metal layer / coating layer, the content of the metal containing Sn constituting the first phase is 30 to 97 mass% of the total mass (100 mass%) of the metal containing Sn constituting the first phase and the alloy containing Ni and Fe constituting the second phase, the content of the alloy containing Ni and Fe constituting the second phase is 3 to 70 mass% of the total mass (100 mass%) of the metal containing Sn constituting the first phase and the alloy containing Ni and Fe constituting the second phase, and the ratio of the content of the first metal to the content of the second metal is 0.4 or more and 35 or less as expressed as the mass ratio of the content of the first metal / content of the second metal.

[0093] The bonding material according to the second embodiment preferably has a base metal layer thickness of 1 to 5000 μm and a coating layer thickness of 1 to 150 μm, the ratio of the base metal layer thickness to the coating layer thickness is 2 to 500 as expressed as base metal layer / coating layer, the content of the Sn-containing metal constituting the first phase is 30 to 97% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase, the content of the Ni and Fe-containing alloy constituting the second phase is 3 to 70% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase, and the ratio of the content of the Sn-containing metal constituting the first phase to the Ni and Fe-containing alloy constituting the second phase is 0.4 or more and 35 or less as expressed as the mass ratio of the content of the first metal / content of the second metal.

[0094] In the bonding material according to the second embodiment, the thickness of the base metal layer is preferably 1 to 2000 μm, the thickness of the coating layer is 1 to 100 μm, the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 500 as expressed as base metal layer / coating layer, the content of the Sn-containing metal constituting the first phase is 30 to 97% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase, the content of the Ni and Fe-containing alloy constituting the second phase is 3 to 70% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase, and the ratio of the content of the Sn-containing metal constituting the first phase to the Ni and Fe-containing alloy constituting the second phase is 0.4 or more and 35 or less as expressed as the mass ratio of the content of the first metal / content of the second metal.

[0095] (Method of manufacturing bonding material) In one embodiment, the bonding material according to the second embodiment can be manufactured, for example, by the following manufacturing method. The method for manufacturing a bonding material according to this embodiment is a method for manufacturing a bonding material having a base metal layer and a coating layer that covers at least both surfaces of the base metal layer. The method for manufacturing the bonding material according to this embodiment comprises a crimping step A and any of the crimping steps B1 to B3.

[0096] <Crimping process A> In the crimping process A, the coating sheet is pressed onto one side of the base metal sheet, thereby covering that side with the coating layer. As illustrated in Figure 2B, the crimping process A yields a bonding material 1D having a base metal layer 2D and a coating layer 3D that covers one surface Sd1 of the base metal layer 2D.

[0097] The base metal sheet contains a first metal containing Sn and a second metal consisting of an alloy containing Ni and Fe. The coating sheet contains a metal with a lower melting point than the second metal. The method for manufacturing the coating sheet may be a known method; for example, it may be manufactured by preparing a metal having a predetermined composition to form the coating sheet, processing the metal into a sheet, rolling it to a predetermined thickness, and cutting it to a predetermined size.

[0098] In this embodiment, the description of the metal contained in the base metal sheet, its particle size, and its content is the same as that of the base metal layer of the bonding material. In this embodiment, the description of the metal contained in the coating sheet and its content is the same as that of the coating layer of the bonding material.

[0099] As for the method of compression, a known rolling method can be used, for example, by using a twin-roll rolling mill. The number of rolling passes and the rolling load applied to the base metal sheet and the coating sheet should be set appropriately according to the desired shape and thickness of the joining material. The rolling load is not particularly limited, but may be, for example, 0.1 to 20 kN. The number of rolling cycles is not particularly limited, but may be 1 to 10. The surface temperature of the rolling roll is not particularly limited, but may be, for example, 50 to 150°C.

[0100] In the bonded material obtained through the crimping process A, an intermetallic compound may be formed at the interface between the base metal layer and the coating layer.

[0101] The method for manufacturing the bonding material according to this embodiment may include any of the crimping steps B1 to B3 after the crimping step A.

[0102] <Crimping process B1> In crimping step B1, two bonding materials are prepared, each having a base metal layer obtained in crimping step A and a coating layer that covers one side of the base metal layer. Hereinafter, the two bonding materials will be referred to as the first bonding material and the second bonding material, respectively. As illustrated in Figure 2C, in the crimping process B1, one surface Sd2 of the base metal layer 2D of the first bonding material 1D and one surface Sd2 of the base metal layer 2D of the second bonding material 1D are pressed together. The crimping process B1 yields a bonding material 1E having a base metal layer 2E and a coating layer 3E that covers both sides of the base metal layer 2E (i.e., Se1 and Se2). The crimping method in crimping process B1 may be the same as the crimping method in crimping process A.

[0103] <Crimping process B2> In crimping step B2, one bonding material is prepared, which has a base metal layer obtained in crimping step A and a coating layer that covers one side of the base metal layer. As illustrated in Figure 2D, in the crimping process B2, the bonding material 1D is bent and the surfaces Sd2 of the base metal layer 2D of the bonding material 1D are pressed together. The crimping process B2 yields a bonding material 1E having a base metal layer 2E and a coating layer 3E that covers both sides of the base metal layer 2E (i.e., Se1 and Se2). The crimping method in crimping process B2 may be the same as the crimping method in crimping process A.

[0104] <Crimping process B3> In crimping step B3, one bonding material is prepared, which has a base metal layer obtained in crimping step A and a coating layer that covers one side of the base metal layer. As illustrated in Figure 2E, in the crimping process B3, the covering sheet 3D' is pressed onto one side Sd2 of the base metal layer 2D of the bonding material 1D. The crimping process B3 yields a bonding material 1E having a base metal layer 2E and a coating layer 3E that covers both sides of the base metal layer 2E (i.e., Se1 and Se2). The crimping method in crimping process B3 may be the same as the crimping method in crimping process A.

[0105] The method for manufacturing the base metal sheet is not particularly limited, but the base metal sheet may be manufactured, for example, by a "powder compaction process".

[0106] <Powder compaction process> In the powder compaction process, a metal powder mixture containing a first metal powder containing Sn and a second metal powder consisting of an alloy containing Ni and Fe is compacted to produce a base metal sheet, which is a preform solder.

[0107] The first metal powder and the second metal powder are the same as the <first metal> and <second metal> described above, respectively.

[0108] A known rolling method can be used to compact the metal powder mixture; for example, a twin-roll rolling mill can be used for processing. The number of rolling passes and the rolling load applied to the metal powder mixture can be appropriately set according to the desired shape and thickness of the target base metal sheet. The rolling load is not particularly limited, but may be, for example, 15 to 40 kN. When using a rolling mill, the surface temperature of the rolling rolls is not particularly limited, but may be, for example, 50 to 150°C.

[0109] The joining material according to the second embodiment described above can suppress the generation of voids in the solder joint, similar to the joining material according to the first embodiment.

[0110] (Joining material: Third embodiment) In the bonding material according to the third embodiment, the base metal layer further contains a third metal whose entire surface is formed of a metal containing Ni. The bonding material according to the third embodiment is the same as the bonding material according to the first embodiment, except that the base metal layer contains a third metal.

[0111] <Third metal> The entire surface of the third metal is formed of a metal containing Ni. In other words, in the third metal, Ni is exposed on the surface. The Ni content in the metal forming the entire surface of the third metal is 50% by mass or more and 100% by mass or less, relative to the total mass of the metal forming the entire surface of the third metal. The melting point of the metal forming the entire surface of the third metal is above 300°C, preferably above 500°C, and more preferably between 600°C and 1600°C. The third metal is preferably dispersed within the base metal layer.

[0112] The metal forming the entire surface of the third metal may consist solely of Ni, or it may contain metals other than Ni. Examples of metals that form the entire surface of the third metal include elemental Ni, alloys of Ni with other metals, and mixtures of Ni-containing alloys with other metals, with elemental Ni being preferred.

[0113] In alloys of Ni with metals other than Ni, examples of metals other than Ni include Ag, Cu, In, Bi, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, Sn, and As. These metals other than Ni may be present individually or in combination of two or more. The group of metals other than Ni can be arbitrarily selected from these metals.

[0114] The metal forming the entire surface of the third metal may contain unavoidable impurities in addition to the aforementioned metal. Even if unavoidable impurities are present, this does not affect the effects of the present invention. The metal forming the entire surface of the third metal may be of one type, or it may be made up of two or more types layered together.

[0115] When the metal forming the entire surface of the third metal is a metal containing Ni and a metal other than Ni, the Ni content in the metal forming the entire surface is 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more, based on the total mass of the metal forming the entire surface. When the metal forming the entire surface of the third metal contains Fe, it is preferable that the Fe content in the metal forming the entire surface of the third metal is 0% by mass or more and less than 5% by mass, relative to the total mass of the metal forming the entire surface of the third metal.

[0116] In the bonding material according to the third embodiment, the third metal preferably has a particle size of 0.1 to 1000 μm, more preferably 1 to 300 μm, and even more preferably 10 to 100 μm. When the particle size of the third metal is above the lower limit of the preferred range mentioned above, it becomes easier to improve the thermal conductivity of the solder joint.

[0117] The specific structure of the third metal will be explained below with an example. As explained in (1) below, the third metal may have a uniform composition throughout. Alternatively, as described in (2) below, the third metal may have a structure with multiple different compositions.

[0118] If the entire third metal has a uniform composition, the third metal may consist only of Ni, as described in (1-1) below, or it may contain Ni and other metals, as described in (1-2) below. Alternatively, as described in (2) below, if the third metal has a structure with multiple different compositions, the third metal may have a core and a surface layer. The following explains these cases.

[0119] (1) When the entire third metal has a uniform composition (1-1) When the third metal consists only of Ni The composition of the third metal is different from that of the first and second metals. In this case, the Ni content in the metal forming the entire surface of the third metal is 100% by mass of the total mass of the metal forming the entire surface of the third metal. The proportion of Ni on the surface of the third metal is 100% of the total surface area (100%) of the third metal. The third metal may contain unavoidable impurities in addition to Ni. Even if unavoidable impurities are present, this does not affect the effects of the present invention.

[0120] (1-2) When the third metal includes Ni and a metal other than Ni The composition of the third metal is different from that of the first and second metals. The third metal may be a mixture of Ni and a metal other than Ni, or an alloy of Ni and a metal other than Ni, or a mixture of an alloy containing Ni and a metal other than Ni.

[0121] Examples of metals other than Ni that may be included as a third metal include Ag, Cu, In, Bi, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, Sn, and As. These metals other than Ni may be included individually or in combination of two or more. The group of metals other than Ni can be arbitrarily selected from these metals.

[0122] The third metal may contain unavoidable impurities in addition to the aforementioned metals. Even if unavoidable impurities are present, this does not affect the effects of the present invention. The third metal in (1-2) may be one type or two or more types.

[0123] When the third metal is a metal containing Ni and a metal other than Ni, the Ni content in the third metal is 50% by mass or more and 100% by mass or less, preferably 70% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more, based on the total mass of the third metal. When the third metal contains Fe, the Fe content in the third metal is preferably 0% by mass or more and less than 5% by mass, relative to the total mass of the third metal.

[0124] (2) When the third metal has a structure consisting of a core portion and a surface layer covering the core portion. As illustrated in Figure 3, the third metal 30A has a core portion 301 and a surface layer 302 that covers the core portion 301. Rc represents the grain size of the core portion 301 (hereinafter, Rc may be referred to as the core diameter). Rs represents the thickness of the surface layer 302.

[0125] The composition of the metal forming the surface layer is different from the composition of the metal forming the core. The composition of the third metal is different from the compositions of the first and second metals. The composition of the metal forming the surface layer of the third metal is different from the composition of the first and second metals.

[0126] ·surface The metal forming the surface layer of the third metal may consist solely of Ni, or it may be a metal containing Ni and other metals. In other words, the metal forming the surface layer of the third metal may be pure Ni, or it may be an alloy of Ni with a metal other than Ni. The metal forming the surface layer of the third metal is preferably elemental Ni.

[0127] Examples of metals other than Ni that may be included in the surface layer of the third metal include Ag, Cu, In, Bi, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, Sn, and As. These metals other than Ni may be included individually or in combination of two or more. The group of metals other than Ni can be arbitrarily selected from these metals.

[0128] The metal forming the surface layer of the third metal may contain unavoidable impurities in addition to the aforementioned metals. Even if unavoidable impurities are present, this does not affect the effects of the present invention. The metal forming the surface layer of the third metal may be one type or two or more types layered together.

[0129] When the metal forming the surface layer of the third metal contains Ni and a metal other than Ni, the Ni content in the metal forming the surface layer of the third metal is 50% by mass or more and less than 100% by mass, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 98% by mass or more, based on the total mass of the metal forming the surface layer of the third metal. When the metal forming the surface layer of the third metal contains Fe, it is preferable that the Fe content in the metal forming the surface layer of the third metal is 0% by mass or more and less than 5% by mass, relative to the total mass of the metal forming the surface layer of the third metal.

[0130] At least a portion of the surface of the core is covered by a surface layer. The surface layer may cover a portion of the core or the entire core, and it is preferable that the entire core is covered. In Figure 3, the entire surface of the core 301 is covered by the surface layer 302. The proportion of the surface area of ​​the core portion covered by the surface layer is preferably 50% to 100%, more preferably 70% to 100%, even more preferably 90% to 100%, particularly preferably 95% to 100%, and most preferably 100% of the total surface area of ​​the core portion (100%).

[0131] The surface thickness Rs of the third metal may be, for example, 0.01 μm or more and 100 μm or less. The surface thickness of the third metal may be 0.1 μm or more, 0.3 μm or more, 0.5 μm or more, 0.75 μm or more, 1 μm or more, or 2 μm or more. The surface thickness of the third metal may be 50 μm or less, 30 μm or less, 10 μm or less, 5 μm or less, or 3 μm or less.

[0132] In this specification, the thickness Rs of the surface layer of the third metal, the core diameter Rc of the core of the third metal, and the thickness Ri of the intermediate layer (described later) can be measured from the cross-sectional structure of the third metal using an optical microscope, SEM, transmission electron microscope (TEM), etc. The surface thickness Rs of the third metal can be measured using Auger electron spectroscopy.

[0133] Alternatively, the core diameter Rc of the core portion of the third metal can be measured as follows: The particle size of the metal powder prepared for use as the core portion during the production of the third metal powder can be defined as the core diameter Rc.

[0134] The surface layer of the third metal may be a plating layer formed by a plating process. Examples of plating methods include well-known electroplating and electroless plating.

[0135] The melting point of the metal forming the surface layer of the third metal is above 300°C, preferably above 500°C, and more preferably between 600°C and 1600°C.

[0136] • Core The metal forming the core of the third metal may be a single elemental metal, a mixture of two or more elemental metals, an alloy formed from two or more metallic elements, a mixture of alloys formed from two or more metallic elements, or a mixture of an alloy formed from two or more metallic elements and an elemental metal.

[0137] Examples of metals that may be included in the core of the third metal include Ag, Cu, In, Bi, Ni, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, Sn, and As. These metals may be included individually or in combination of two or more. The group of metals that may be included in the core can be arbitrarily selected from these metals.

[0138] The core of the third metal may contain unavoidable impurities in addition to the aforementioned metals. Even if unavoidable impurities are present, this does not affect the effects of the present invention. The metal forming the core of the third metal may be one type or two or more types.

[0139] The core diameter Rc of the core portion of the third metal is preferably 0.1 to 1000 μm, more preferably 3 to 800 μm, even more preferably 5 to 500 μm, particularly preferably 8 to 300 μm, and most preferably 25 to 150 μm.

[0140] The third metal 30A may be of one type or of two or more types.

[0141] <Relationship between the content of primary, secondary, and tertiary metals> In the base metal layer of the bonding material according to the third embodiment, the content of the first metal is preferably 10 to 98% by mass, more preferably 30 to 90% by mass, and even more preferably 40 to 80% by mass, based on the total mass of the first metal, the second metal, and the third metal.

[0142] In the base metal layer of the bonding material according to the third embodiment, the content of the second metal is preferably 1 to 70% by mass, and more preferably 3 to 30% by mass, based on the total mass of the first metal, the second metal, and the third metal. The heat resistance of the solder joint is further improved when the content of the second metal is within the aforementioned preferred range.

[0143] In the base metal layer of the bonding material according to the third embodiment, the content of the third metal is preferably 1 to 70% by mass, and more preferably 5 to 50% by mass, based on the total mass of the first metal, the second metal, and the third metal. By having the content of the third metal within the aforementioned preferred range, it becomes easier to further improve the thermal conductivity of the solder joint.

[0144] In the base metal layer of the bonding material according to the third embodiment, the total content of the second metal and the third metal is preferably 1 to 90% by mass, more preferably 3 to 70% by mass, and even more preferably 20 to 60% by mass, based on the total mass of the first metal, the second metal, and the third metal.

[0145] In the base metal layer of the bonding material according to the third embodiment, the total content of the first metal, the second metal, and the third metal does not exceed 100% by mass.

[0146] In the base metal layer of the bonding material according to the third embodiment, the total content of the first metal, the second metal, and the third metal is preferably 60 to 100% by mass, more preferably 80 to 100% by mass, even more preferably 90 to 100% by mass, and may be 100% by mass, based on the total mass of the base metal layer.

[0147] In the base metal layer of the bonding material according to the third embodiment, the ratio of the content of the first metal to the content of the second metal is preferably 0.1 or more and 100 or less, expressed as a mass ratio of content of the first metal / content of the second metal, more preferably 1 or more and 50 or less, and even more preferably 4 or more and 30 or less. When the mass ratio is within the aforementioned preferred range, voids in the solder joint are more easily suppressed, and the heat resistance of the solder joint is further improved.

[0148] In the base metal layer of the bonding material according to the third embodiment, the ratio of the content of the first metal to the content of the third metal is preferably 0.1 or more and 100 or less, expressed as a mass ratio of content of the first metal / content of the third metal, more preferably 0.3 or more and 20 or less, and even more preferably 1 or more and 5 or less. When the mass ratio is within the aforementioned preferred range, it becomes easier to suppress voids in the solder joint and to improve the thermal conductivity of the solder joint.

[0149] In the base metal layer of the bonding material according to the third embodiment, the ratio of the content of the second metal to the content of the third metal is preferably 0.01 or more and 100 or less, expressed as a mass ratio of the content of the third metal / content of the second metal, more preferably 0.1 or more and 50 or less, and even more preferably 1 or more and 30 or less. When the mass ratio is within the aforementioned preferred range, the heat resistance of the solder joint is more easily improved, and the thermal conductivity of the solder joint is also more easily enhanced.

[0150] In the bonding material according to the third embodiment, the description of the composition of the coating layer is the same as in the first embodiment.

[0151] In the bonding material according to the third embodiment, the description of the thickness of the base metal layer and the coating layer is the same as in the first embodiment.

[0152] In the bonding material according to the third embodiment, the thickness of the base metal layer is preferably 5 to 5000 μm, more preferably 150 to 1500 μm, and even more preferably 150 to 290 μm. In the bonding material according to the third embodiment, the thickness of the coating layer is preferably 1 to 150 μm, more preferably 3 to 100 μm, and even more preferably 5 to 75 μm. In the bonding material according to the third embodiment, the ratio of the thickness of the base metal layer to the thickness of the coating layer is expressed as a ratio of base metal layer / coating layer, and this ratio is preferably, for example, 1 to 500, more preferably 2 to 100, and even more preferably 2 to 58.

[0153] The thickness of the base metal layer of the bonding material according to the third embodiment is, for example, 1-5000 μm, 3-5000 μm, 5-5000 μm, 10-5000 μm, 15-5000 μm, 20-5000 μm, 25-5000 μm, 30-5000 μm, 40-5000 μm, 50-5000 μm, 75-5000 μm μm, 100~5000μm, 125~5000μm, 150~5000μm, 175~5000μm, 200~5000μm, 250~5000 μm, 290~5000μm, 300~5000μm, 350~5000μm, 400~5000μm, 500~5000μm, 750~5000 μm, 1000~5000μm, 1200~5000μm, 1500~5000μm, 1~4000μm, 1~3500μm, 1~3000μm , 1~2500μm, 1~2000μm, 1~1500μm, 1~1200μm, 1~1000μm, 1~750μm, 1~500μm, 1~40 The particle sizes may also be 0 μm, 1-350 μm, 1-300 μm, 1-290 μm, 1-250 μm, 1-200 μm, 1-175 μm, 1-150 μm, 1-125 μm, 1-100 μm, 1-75 μm, 1-50 μm, 1-40 μm, 1-30 μm, 1-25 μm, 1-20 μm, and 1-15 μm. If the thickness of the base metal layer is greater than or equal to the lower limit, it becomes easier to improve the heat resistance of the solder joint. If it is less than or equal to the upper limit, it becomes easier to suppress the generation of voids in the solder joint that comes into contact with the object being joined.

[0154] The thickness of the coating layer of the bonding material according to the third embodiment may be, for example, 1-150 μm, 3-150 μm, 5-150 μm, 7.5-150 μm, 10-150 μm, 12.5-150 μm, 15-150 μm, 20-150 μm, 25-150 μm, 30-150 μm, 40-150 μm, 50-150 μm, 75-150 μm, 1-125 μm, 1-100 μm, 1-75 μm, 1-50 μm, 1-40 μm, 1-30 μm, 1-25 μm, 1-20 μm, 1-15 μm, 1-12.5 μm, 1-10 μm, 1-7.5 μm, 1-5 μm, or 1-3 μm. If the thickness of the coating layer is greater than or equal to the lower limit, it becomes easier to suppress the occurrence of voids in the solder joint that comes into contact with the objects being joined. If it is less than or equal to the upper limit, it becomes easier to improve the heat resistance of the solder joint.

[0155] The thickness of the bonding material according to the third embodiment is, for example, 2-5300 μm, 2-4000 μm, 2-3000 μm, 2-2000 μm, 2-1750 μm, 2-1510 μm, 2-1200 μm, 2-1000 μm, 2-750 μm, 2-500 μm, 2-400 μm, 2-300 μm, 2-250 μm, 2-200 μm, 2-150 μm, 2-100 μm, 2-75 μm, 2-50 μm, 2-40 μm, 2-30 μm, 5-5300 μm The microparticle sizes are as follows: μm, 10-5300 μm, 15-5300 μm, 20-5300 μm, 30-5300 μm, 40-5300 μm, 50-5300 μm, 75-5300 μm, 100-5300 μm, 150-5300 μm, 200-5300 μm, 250-5300 μm, 300-5300 μm, 400-5300 μm, 500-5300 μm, 750-5300 μm, 1000-5300 μm, and 1200-5300 μm.

[0156] In the bonding material according to the third embodiment, the ratio of the thickness of the base metal layer to the thickness of the coating layer may be expressed as a ratio of base metal layer / coating layer, for example, 2-500, 3-500, 5-500, 7.5-500, 10-500, 15-500, 20-500, 30-500, 50-500, 100-500, 200-500, 2-400, 2-350, 2-300, 2-250, 2-200, 2-150, 2-100, 2-75, 2-60, 2-58, 2-50, 2-30, 2-20, 2-15, 2-10, 2-7.5, 2-5, or 2-3. When the ratio of the base metal layer to the coating layer is within the above range, it becomes easier to improve the heat resistance of the solder joint and to further suppress the generation of voids in the solder joint that is in contact with the object being joined. When it is above the lower limit of the above range, it becomes easier to improve the heat resistance of the solder joint. When it is below the upper limit of the above range, it becomes easier to suppress the generation of voids in the solder joint.

[0157] With respect to the bonding material according to the third embodiment, the above-mentioned provisions regarding the thickness of the base metal layer and the coating layer, the ratio of the thickness of the base metal layer to the thickness of the coating layer, the structure of the third metal, and the content of the first metal, second metal, and third metal may be combined in any way.

[0158] Hereinafter, the ratio of the thickness of the base metal layer to the thickness of the coating layer refers to the ratio expressed as base metal layer (μm) / coating layer (μm). The bonding material according to the third embodiment preferably has a coating layer thickness of 1 to 150 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 300, more preferably has a coating layer thickness of 5 to 150 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 200, even more preferably has a coating layer thickness of 5 to 150 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 100, and particularly preferably has a coating layer thickness of 5 to 75 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 60. When the thickness of the coating layer is within the above range, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is within the above range, it becomes easier to improve the heat resistance of the solder joint and to suppress the generation of voids in the solder joint.

[0159] The bonding material according to the third embodiment preferably has a base metal layer thickness of 150 to 290 μm, a coating layer thickness of 5 to 100 μm, a ratio of the base metal layer thickness to the coating layer thickness of 2 to 58 (expressed as base metal layer / coating layer), the third metal consists only of Ni, the content of the first metal is 30 to 90% by mass relative to the total mass of the first, second, and third metals, the content of the second metal is 3 to 30% by mass relative to the total mass of the first, second, and third metals, the content of the third metal is 5 to 50% by mass relative to the total mass of the first, second, and third metals, the ratio of the content of the first metal to the content of the second metal is 4 or more and 30 or less (expressed as first metal content / second metal content), and the ratio of the content of the first metal to the content of the third metal is the mass ratio (first metal content / third metal content) The ratio is between 1 and 5, and the ratio of the content of the second metal to the content of the third metal is expressed as a mass ratio of the content of the third metal / the content of the second metal, which is between 1 and 30.

[0160] Alternatively, the bonding material according to the third embodiment preferably has a base metal layer thickness of 150 to 290 μm, a coating layer thickness of 5 to 100 μm, a ratio of the base metal layer thickness to the coating layer thickness of 2 to 58 expressed as base metal layer / coating layer, the third metal has a structure consisting of a core portion and a surface layer covering the core portion, the metal forming the surface layer of the third metal consists only of Ni, the content of the first metal is 30 to 90% by mass relative to the total mass of the first metal, second metal and third metal, and the content of the second metal The content of the first metal is 3 to 30% by mass relative to the total mass of the first, second, and third metals; the content of the third metal is 5 to 50% by mass relative to the total mass of the first, second, and third metals; the ratio of the content of the first metal to the content of the second metal is 4 to 30 as a mass ratio expressed as content of the first metal / content of the second metal; the ratio of the content of the first metal to the content of the third metal is 1 to 5 as a mass ratio expressed as content of the first metal / content of the third metal; and the ratio of the content of the second metal to the content of the third metal is 1 to 30 as a mass ratio expressed as content of the third metal / content of the second metal.

[0161] The bonding material according to the third embodiment preferably has a base metal layer thickness of 1 to 5000 μm, a coating layer thickness of 1 to 150 μm, a ratio of the base metal layer thickness to the coating layer thickness of 2 to 500 (expressed as base metal layer / coating layer), the third metal consists only of Ni, the content of the first metal is 30 to 90% by mass relative to the total mass of the first, second, and third metals, the content of the second metal is 3 to 30% by mass relative to the total mass of the first, second, and third metals, the content of the third metal is 5 to 50% by mass relative to the total mass of the first, second, and third metals, the ratio of the content of the first metal to the content of the second metal is 4 or more and 30 or less (expressed as first metal content / second metal content), and the ratio of the content of the first metal to the content of the third metal is the mass ratio (first metal content / third metal content) The ratio is between 1 and 5, and the ratio of the content of the second metal to the content of the third metal is expressed as a mass ratio of the content of the third metal / the content of the second metal, which is between 1 and 30.

[0162] The bonding material according to the third embodiment preferably has a base metal layer thickness of 1 to 500 μm, a coating layer thickness of 1 to 100 μm, a ratio of the base metal layer thickness to the coating layer thickness expressed as base metal layer / coating layer of 2 to 500, the third metal consisting only of Ni, the content of the first metal being 30 to 90% by mass relative to the total mass of the first, second, and third metals, the content of the second metal being 3 to 30% by mass relative to the total mass of the first, second, and third metals, and the content of the third metal The amount of the first metal is 5 to 50% by mass relative to the total mass of the first, second, and third metals. The ratio of the content of the first metal to the content of the second metal is expressed as a mass ratio of content of the first metal / content of the second metal, and is between 4 and 30. The ratio of the content of the first metal to the content of the third metal is expressed as a mass ratio of content of the first metal / content of the third metal, and is between 1 and 5. The ratio of the content of the second metal to the content of the third metal is expressed as a mass ratio of content of the third metal / content of the second metal, and is between 1 and 30.

[0163] The bonding material according to the third embodiment can be manufactured in the same manner as the bonding material according to the first embodiment.

[0164] The bonding material according to the third embodiment, like the bonding material according to the first embodiment, can suppress the generation of voids in the solder joint. In addition, the bonding material according to the third embodiment can further improve the thermal conductivity of the solder joint because the base metal layer contains a third metal. The reason for this effect is not clear, but it is presumed to be as follows.

[0165] Intermetallic compounds have lower thermal conductivity compared to materials like Cu and Ni. For example, the thermal conductivity of Cu and Ni is 401 W / m·K and 88.5 W / m·K, respectively, while the thermal conductivity of the intermetallic compounds Cu6Sn5 (Cu3Sn) and Ni3Sn4 is 34 W / m·K and 20 W / m·K, respectively. The entire surface of the third metal is formed of a metal containing Ni, and since Ni has low reactivity with Sn, Ni3Sn4 is unlikely to be formed. In other words, the surface of the third metal is less likely to react with Sn in the base metal layer to form intermetallic compounds, making it possible to improve the thermal conductivity of the solder joint.

[0166] (Joining material: Fourth embodiment) The bonding material according to the fourth embodiment comprises a base metal layer and a coating layer that covers at least one surface of the base metal layer. Figure 4 is an example of an SEM image showing a cross-section in the thickness direction of a bonding material according to the fourth embodiment. In Figure 4, the bonding material 1C has a base metal layer 2C and a coating layer 3C that covers both surfaces of the base metal layer 2C. The substrate metal layer 2C shown in Figure 4 has a metal structure comprising a first phase 10 which is a continuous phase, a second phase 20 dispersed in the first phase, and a third phase 30 dispersed in the first phase.

[0167] The bonding material 1C shown in Figure 4 has a base metal layer thickness of 285 μm and a coating layer thickness of 7.5 μm. In the base metal layer 2C, the content of the metal forming the first phase is 65 mass% of the total mass of the base metal layer, the content of the metal forming the second phase is 10 mass% of the total mass of the base metal layer, and the content of the metal forming the third phase is 35 mass% of the total mass of the base metal layer. The Ni content in the second phase is 90 mass% of the total mass of the second phase, and the Fe content in the second phase is 10 mass% of the total mass of the second phase.

[0168] The bonding material according to the fourth embodiment is a clad material in which a coating layer is bonded to at least one surface of a base metal layer. The bonding material according to the fourth embodiment is the same as the bonding material according to the second embodiment, except that the base metal layer has a third phase.

[0169] In the base metal layer, the third phase 30 is dispersed in the first phase 10. The third phase 30 is composed entirely of a metal containing Ni. The bonding material according to the fourth embodiment is the same as the bonding material according to the second embodiment, except that the base metal layer has a third phase. The description of the metal whose entire surface contains Ni, its particle size, and its content is the same as for the <third metal> in the third embodiment.

[0170] The description of the melting point of the metal as a whole that forms the entire surface of the third phase is similar to the description of the melting point of the metal that forms the entire surface of the third metal.

[0171] The description of the metals constituting the first phase and their content is the same as that of the <first metal> in the third embodiment. The description of the metals constituting the second phase and their content is the same as that of the <second metal> in the third embodiment.

[0172] If the entire third phase has a uniform composition, the overall composition of the metal constituting the third phase is different from the overall composition of the metal constituting the first phase and the overall composition of the alloy constituting the second phase. The explanation for the melting point of the metal constituting the third phase as a whole is the same as the explanation for the melting point of the third metal. The particle size of the third phase can be the particle size of the third metal powder prepared to form the third phase.

[0173] If the third phase has a structure consisting of a core and a surface layer covering the core, the overall composition of the metal forming the surface layer of the third phase is different from the overall composition of the metal constituting the first phase and the overall composition of the alloy constituting the second phase. The overall melting point of the metal forming the surface layer of the third phase is the same as the melting point of the metal forming the surface layer of the third metal. The description of the core diameter and surface thickness of the third phase is the same as that of the core diameter Rc and surface thickness Rs of the third metal, respectively.

[0174] In the bonding material according to the fourth embodiment, the description of the composition of the coating layer is the same as in the second embodiment.

[0175] In the bonding material according to the fourth embodiment, the description of the thickness of the base metal layer and the coating layer is the same as in the third embodiment.

[0176] The thickness of the base metal layer can be, for example, 1-5000 μm, 3-5000 μm, 5-5000 μm, 10-5000 μm, 15-5000 μm, 20-5000 μm, 25-5000 μm, 30-5000 μm, 40-5000 μm, 50-5000 μm, 75-5000 μm, 100-500 μm. 0μm, 125~5000μm, 150~5000μm, 175~5000μm, 200~5000μm, 250~5000μm, 290~5 000μm, 300~5000μm, 350~5000μm, 400~5000μm, 500~5000μm, 750~5000μm, 100 0~5000μm, 1200~5000μm, 1500~5000μm, 1~4000μm, 1~3500μm, 1~3000μm, 1~25 00μm, 1~2000μm, 1~1500μm, 1~1200μm, 1~1000μm, 1~750μm, 1~500μm, 1~400μm The particle sizes may also be 1-350 μm, 1-300 μm, 1-290 μm, 1-250 μm, 1-200 μm, 1-175 μm, 1-150 μm, 1-125 μm, 1-100 μm, 1-75 μm, 1-50 μm, 1-40 μm, 1-30 μm, 1-25 μm, 1-20 μm, and 1-15 μm. If the thickness of the base metal layer is greater than or equal to the lower limit, it becomes easier to improve the heat resistance of the solder joint. If it is less than or equal to the upper limit, it becomes easier to suppress the generation of voids in the solder joint that comes into contact with the object being joined.

[0177] The thickness of the coating layer may be, for example, 1-150 μm, 3-150 μm, 5-150 μm, 7.5-150 μm, 10-150 μm, 12.5-150 μm, 15-150 μm, 20-150 μm, 25-150 μm, 30-150 μm, 40-150 μm, 50-150 μm, 75-150 μm, 1-125 μm, 1-100 μm, 1-75 μm, 1-50 μm, 1-40 μm, 1-30 μm, 1-25 μm, 1-20 μm, 1-15 μm, 1-12.5 μm, 1-10 μm, 1-7.5 μm, 1-5 μm, or 1-3 μm. If the thickness of the coating layer is greater than or equal to the lower limit, it becomes easier to suppress the occurrence of voids in the solder joint that comes into contact with the objects being joined. If it is less than or equal to the upper limit, it becomes easier to improve the heat resistance of the solder joint.

[0178] The thickness of the bonding material can be, for example, 2-5300μm, 2-4000μm, 2-3000μm, 2-2000μm, 2-1750μm, 2-1510μm, 2-1200μm, 2-1000μm, 2-750μm, 2-500μm, 2-400μm, 2-300μm, 2-250μm, 2-200μm, 2-150μm, 2-100μm, 2-75μm, 2-50μm, 2-40μm, 2-30μm, 5-5300μm, 10 These are examples of the following: ~5300μm, 15~5300μm, 20~5300μm, 30~5300μm, 40~5300μm, 50~5300μm, 75~5300μm, 100~5300μm, 150~5300μm, 200~5300μm, 250~5300μm, 300~5300μm, 400~5300μm, 500~5300μm, 750~5300μm, 1000~5300μm, and 1200~5300μm.

[0179] The ratio of the thickness of the base metal layer to the thickness of the coating layer may be expressed as a ratio of base metal layer / coating layer, for example, 2-500, 3-500, 5-500, 7.5-500, 10-500, 15-500, 20-500, 30-500, 50-500, 100-500, 200-500, 2-400, 2-350, 2-300, 2-250, 2-200, 2-150, 2-100, 2-75, 2-60, 2-58, 2-50, 2-30, 2-20, 2-15, 2-10, 2-7.5, 2-5, or 2-3. When the ratio of the base metal layer to the coating layer is within the above range, it becomes easier to improve the heat resistance of the solder joint and to further suppress the generation of voids in the solder joint that is in contact with the object being joined. When it is above the lower limit of the above range, it becomes easier to improve the heat resistance of the solder joint. When it is below the upper limit of the above range, it becomes easier to suppress the generation of voids in the solder joint.

[0180] Hereinafter, the ratio of the thickness of the base metal layer to the thickness of the coating layer refers to the ratio expressed as base metal layer (μm) / coating layer (μm). The bonding material according to the fourth embodiment preferably has a coating layer thickness of 1 to 150 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 300, more preferably has a coating layer thickness of 5 to 150 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 200, even more preferably has a coating layer thickness of 5 to 150 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 100, and particularly preferably has a coating layer thickness of 5 to 75 μm, with a ratio of the thickness of the base metal layer to the thickness of the coating layer of 2 to 60. When the thickness of the coating layer is within the above range, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is within the above range, it becomes easier to improve the heat resistance of the solder joint and to suppress the generation of voids in the solder joint.

[0181] The bonding material according to the fourth embodiment preferably has a base metal layer thickness of 1 to 5000 μm, a coating layer thickness of 1 to 150 μm, a ratio of the base metal layer thickness to the coating layer thickness of 2 to 500 expressed as base metal layer / coating layer, the metal constituting the third phase consists only of Ni, the content of the metal constituting the first phase is 30 to 90% by mass relative to the total mass of the metal constituting the first phase, the alloy constituting the second phase, and the metal constituting the third phase, and the content of the alloy constituting the second phase is The content of the metal constituting the third phase is 3 to 30% by mass relative to the total mass, and the content of the metal constituting the third phase is 5 to 50% by mass relative to the total mass of the metal constituting the first phase, the alloy constituting the second phase, and the metal constituting the third phase. The ratio of the content of the metal constituting the first phase to the content of the alloy constituting the second phase is a mass ratio of 4 to 30, expressed as the content of the metal constituting the first phase / the content of the alloy constituting the second phase. The ratio of the content of the metal constituting the first phase to the content of the metal constituting the third phase is a mass ratio of 1 to 5, expressed as the content of the metal constituting the first phase / the content of the metal constituting the third phase. The ratio of the content of the alloy constituting the second phase to the content of the metal constituting the third phase is a mass ratio of 1 to 30, expressed as the content of the metal constituting the third phase / the content of the alloy constituting the second phase.

[0182] The bonding material according to the fourth embodiment preferably has a base metal layer thickness of 1 to 500 μm, a coating layer thickness of 1 to 100 μm, a ratio of the base metal layer thickness to the coating layer thickness of 2 to 500 as expressed as base metal layer / coating layer, the metal constituting the third phase consists only of Ni, the content of the metal constituting the first phase is 30 to 90% by mass relative to the total mass of the metal constituting the first phase, the alloy constituting the second phase, and the metal constituting the third phase, and the content of the alloy constituting the second phase is the total mass of the metal constituting the first phase, the alloy constituting the second phase, and the metal constituting the third phase The content of the metal constituting the third phase is 3 to 30% by mass relative to the total mass, and the content of the metal constituting the third phase is 5 to 50% by mass relative to the total mass of the metal constituting the first phase, the alloy constituting the second phase, and the metal constituting the third phase. The ratio of the content of the metal constituting the first phase to the content of the alloy constituting the second phase is a mass ratio of 4 to 30, expressed as the content of the metal constituting the first phase / the content of the alloy constituting the second phase. The ratio of the content of the metal constituting the first phase to the content of the metal constituting the third phase is a mass ratio of 1 to 5, expressed as the content of the metal constituting the first phase / the content of the metal constituting the third phase. The ratio of the content of the alloy constituting the second phase to the content of the metal constituting the third phase is a mass ratio of 1 to 30, expressed as the content of the metal constituting the third phase / the content of the alloy constituting the second phase.

[0183] The bonding material according to the fourth embodiment, like the bonding material according to the third embodiment, can suppress the generation of voids in the solder joint and can further improve the thermal conductivity of the solder joint.

[0184] The bonding material according to the fourth embodiment can be manufactured by the same manufacturing method as the bonding material according to the second embodiment, except that a third metal powder is used in addition to the first metal powder and the second metal powder.

[0185] The first metal powder, the second metal powder, and the third metal powder are the same as the <first metal>, <second metal>, and <third metal> described above, respectively.

[0186] The bonding material according to the fourth embodiment can be manufactured in the same manner as the bonding material according to the second embodiment.

[0187] (Joining material: Fifth embodiment) In the bonding material according to the fifth embodiment, the base metal layer further contains a third metal 30B whose entire surface is formed of a metal containing Ni. As illustrated in Figure 5, the third metal 30B has an intermediate layer 303 between the core portion 301 and the surface layer 302 covering the core portion 301. The intermediate layer 303 is adjacent to the core portion 301 and also adjacent to the surface layer 302. Ri represents the thickness of the intermediate layer 303. The bonding material according to the fifth embodiment is the same as the bonding material according to the first embodiment, except that the base metal layer contains the third metal 30B.

[0188] The intermediate layer may cover a portion of the core surface or the entire surface of the core, with the latter being preferable. In Figure 5, the intermediate layer 303 covers the entire surface of the core 301. The proportion of the surface area of ​​the core portion covered by the intermediate layer is preferably 50% to 100%, more preferably 70% to 100%, even more preferably 90% to 100%, particularly preferably 95% to 100%, and most preferably 100% of the total surface area of ​​the core portion (100%).

[0189] The composition of the metal forming the intermediate layer is different from that of the metal forming the core and the metal forming the surface layer. The intermediate layer may consist of one layer or two or more layers.

[0190] The metal forming the intermediate layer may be a single elemental metal or an alloy formed from two or more metallic elements.

[0191] Examples of metals that may be included in the intermediate layer include Ag, Cu, In, Bi, Ni, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, Sn, and As. The intermediate layer may contain one of these metals or two or more. The group of metals that may be included in the intermediate layer can be arbitrarily selected from these metals.

[0192] The intermediate layer may contain unavoidable impurities in addition to the aforementioned metals. Even if unavoidable impurities are present, this does not affect the effects of the present invention. The middle layer may consist of one type or two or more types.

[0193] The thickness Ri of the intermediate layer may be, for example, 0.01 μm or more and 100 μm or less, 0.05 μm or more and 50 μm or less, or 0.1 μm or more and 10 μm or less.

[0194] The intermediate layer may be a plating formed by a plating process. Examples of plating methods include well-known electroplating and electroless plating.

[0195] The core portion 301 and surface layer 302 in the third metal 30B are the same as those described above for the third metal 30A. The third metal 30B may be one type or two or more types.

[0196] The bonding material according to the fifth embodiment, like the bonding material according to the third embodiment, can suppress the generation of voids in the solder joint and can further improve the thermal conductivity of the solder joint. The presence of an intermediate layer 303 in the third metal 30B makes it easier to provide a surface layer 302 for the third metal 30B.

[0197] (Other embodiments) In the joining material according to other embodiments, only one side of the base metal layer may be covered with a coating layer. The joining material according to other embodiments may be a clad material in which one side of the base metal layer and the coating layer are pressed together. A bonding material in which only one side of the base metal layer is covered with a coating layer can be manufactured by the <compression step A> described above in the manufacturing method of the bonding material of the second embodiment.

[0198] Alternatively, in a bonding material according to another embodiment, the base metal layer may have a fourth metal in addition to the first, second, and third metals described in the third embodiment. The fourth metal is a different metal from the first, second, and third metals.

[0199] The metal forming the fourth metal may be a single elemental metal, a mixture of two or more elemental metals, an alloy formed from two or more metallic elements, a mixture of alloys formed from two or more metallic elements, or a mixture of an alloy formed from two or more metallic elements and an elemental metal.

[0200] Examples of metals that may be included in the quaternary metal include Ag, Cu, In, Bi, Ni, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, Sn, and As. The quaternary metal may include one of these metals or two or more. The group of metals that may be included in the quaternary metal can be arbitrarily selected from these metals.

[0201] The fourth metal powder preferably has a particle size of 0.1 to 1000 μm, more preferably 1 to 100 μm, and even more preferably 5 to 50 μm. The fourth metal powder may contain one type of metal or two or more types of metal. The fourth metal powder is not limited to one type; two or more metal powders with different compositions may be used.

[0202] Alternatively, the bonding material according to the other embodiment is a bonding material having a base metal layer described in the above embodiment and a coating layer that covers at least one surface of the base metal layer, and is manufactured, for example, by a hot-dip plating method, a sputtering method, or the like. When using a hot-dip galvanizing method, for example, the base metal layer can be immersed in a molten metal that forms the coating layer and cooled to coat at least one surface of the base metal layer with the metal that forms the coating layer, thereby obtaining the bonding material according to this embodiment. When using the sputtering method, the bonding material according to this embodiment can be obtained by sputtering the metal that will form the coating layer onto the base metal layer, thereby coating at least one surface of the base metal layer with the metal that will form the coating layer.

[0203] Alternatively, the bonding material according to the other embodiment may be obtained by coating the base metal layer of the second embodiment with a coating layer using, for example, a hot-dip plating method or a sputtering method.

[0204] (Solder joint) In one embodiment, the present invention provides a solder joint formed using the bonding material according to the above embodiment. The solder joint of this embodiment does not melt even when the power semiconductor is operating at high temperatures, and the generation of voids at the solder joint can be suppressed.

[0205] (Method of manufacturing solder joints) In one embodiment, the present invention is a method for manufacturing a solder joint, which uses a joining material manufactured by the above-described (method for manufacturing a joining material) to form a joint between objects. The objects to be joined using this manufacturing method are not particularly limited. For example, a semiconductor element and a substrate can be joined by applying this manufacturing method. Examples of semiconductor devices include silicon carbide (SiC) chips and Si chips. Examples of substrates include circuit boards, ceramic substrates, metal substrates, and DCB (Direct Copper Bonding) substrates. The electrodes on the substrate may be, for example, Cu electrodes, or Cu electrodes that have been treated with Sn plating, Ni plating, Ni-Au plating, Ni-Pd plating, or Ni-Pd-Au plating. Furthermore, when joining, flux may be applied in advance to one or both surfaces of the joining material, the joining surface of the semiconductor element, or the joining surface of the substrate.

[0206] The temperature at which the semiconductor element and the substrate are joined is preferably, for example, 120°C to 400°C, but may also be 200°C to 400°C, or 250°C to 400°C. The solder joint manufacturing method of this embodiment is useful for joining under high-temperature conditions (250°C or higher).

[0207] The atmosphere used when joining the objects can be an atmospheric atmosphere, an inert atmosphere such as a nitrogen atmosphere, or a reducing atmosphere. In a nitrogen atmosphere, the pressure applied during joining is preferably adjusted to between 0.1 MPa and 10 MPa. By joining the objects in a nitrogen atmosphere in this way, the effect of suppressing void formation is enhanced. In a reducing atmosphere, it is possible to join objects without pressurization.

[0208] Using the joining material of the above embodiment, a joint can be formed between objects. The shear strength of this joint may be 12 to 100 N, 16 to 50 N, or 20 to 35 N under conditions of 6.0 mm / min and 250°C.

[0209] The shear strength of the joint can be measured, for example, as follows: The target bonding material is cut to a size of 5 mm x 5 mm to obtain a test specimen. Next, the test specimen is mounted on an electroless nickel-plated Cu substrate with a thickness of 0.5 mm and dimensions of 50 mm x 50 mm. The surface roughness of the substrate is set to Sa = 0.31 μm and Sz = 8.53 μm. For measuring the surface roughness of the substrate, a laser microscope can be used, for example. As a laser microscope, for example, a VK-X1000 (manufactured by Keyence) can be used. Next, a 0.5mm thick, 5mm x 5mm copper plate is mounted on top of the bonding material. Next, soldering is performed in a reflow oven under pressure in a formic acid atmosphere, using a profile with a peak temperature of 250°C and a cooling rate of 2°C / sec, to create a solder joint. Next, the shear strength (N) at the joint of the fabricated solder joint is measured using a shear strength measuring device under the conditions of 6.0 mm / min and 250°C. For example, the STR-1000 manufactured by Resca can be used as the shear strength measuring device. [Examples]

[0210] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0211] <Manufacturing of base metal sheets and coated sheets> The base metal sheets (A) to (G) were manufactured using the following procedure. The base metal sheets (A) to (G) are preform solders obtained by rolling and molding using the following raw materials: first metal powder, second metal powder, third metal powder (1), and third metal powder (2).

[0212] The particle size of the metal powder was measured using a Microtrac-Bell laser diffraction / scattering particle size distribution analyzer (MT3300EXII), with the average particle size measured on a volume basis. The melting points of the metal powders were determined by differential scanning calorimetry (DSC). The first metal powder was measured using a DSC7020 from Hitachi High-Tech Science Corporation, while the second and third metal powders were measured using a DSC404-F3Pegasus from NETZSCH GmbH. The thickness Rs of the surface layer of the third metal powder was measured using an Auger electron spectroscopy analyzer.

[0213] The first metal powder Sn Metal powder with 100% by mass of Sn (Sn 100% by mass powder), particle size 65 μm, melting point 232 °C

[0214] The second metal powder Ni10Fe Metal powder composed of an alloy of 90% by mass of Ni and 10% by mass of Fe (Ni - 10% by mass Fe powder), particle size 12.8 μm, melting point 1444 °C

[0215] The third metal powder (1) Ni-plated Cu As the core part of the third metal powder (1), a Cu 100% by mass core ball was used. The particle size of the core part (that is, the core diameter Rc of the core part) was 100 μm. The surface layer of the third metal powder (1) was plated with 100% by mass of Ni. The plating thickness (that is, the thickness Rs of the surface layer) was 2 μm. The plating core ball of the third metal powder (1) is one in which the entire surface of the Cu 100% by mass core ball is coated with 100% by mass of Ni plating. All of the 100% by mass of Ni plating was formed by electroplating.

[0216] The third metal powder (2) Ni Metal powder with 100% by mass of Ni (Ni 100% by mass powder), particle size 100 μm

[0217] Base metal sheet (A) Sn - 40 (Ni1Fe) Mixing process: 60 parts by mass of the first metal powder and 40 parts by mass of the second metal powder were stirred to prepare a metal powder mixture. Rolling process: Next, the prepared metal powder mixture was introduced into the hopper of a two-roll rolling mill, the surface temperature of the rolling rolls was set to 100 °C, and a strip-shaped rolled material was obtained such that the rolling load became approximately 25 kN. Then, it was rolled to obtain a strip-shaped base metal sheet (A) with a predetermined thickness.

[0218] Base metal sheet (B) Sn-70 (Ni10Fe) A strip-shaped base metal sheet (B) of a predetermined thickness was obtained in the same manner as the manufacturing method for base metal sheet (A), except that a metal powder mixture was prepared by stirring 30 parts by mass of first metal powder and 70 parts by mass of second metal powder.

[0219] Base metal sheet (C) Sn-20 (Ni10Fe) A strip-shaped base metal sheet (C) of a predetermined thickness was obtained in the same manner as the manufacturing method for base metal sheet (A), except that a metal powder mixture was prepared by stirring 80 parts by mass of first metal powder and 20 parts by mass of second metal powder.

[0220] Base metal sheet (D) Sn-10 (Ni10Fe) A strip-shaped base metal sheet (D) of a predetermined thickness was obtained in the same manner as the manufacturing method for base metal sheet (A), except that a metal powder mixture was prepared by stirring 90 parts by mass of first metal powder and 10 parts by mass of second metal powder.

[0221] Base metal sheet (E) Sn-3 (Ni10Fe) A strip-shaped base metal sheet (E) of a predetermined thickness was obtained in the same manner as the manufacturing method for base metal sheet (A), except that a metal powder mixture was prepared by stirring 97 parts by mass of first metal powder and 3 parts by mass of second metal powder.

[0222] Base metal sheet (F) Sn-5(Ni10Fe)-35(Ni plated Cu) A strip-shaped base metal sheet (F) of a predetermined thickness was obtained in the same manner as the manufacturing method for base metal sheet (A), except that a metal powder mixture was prepared by stirring 60 parts by mass of first metal powder, 5 parts by mass of second metal powder, and 35 parts by mass of third metal powder (1).

[0223] Base metal sheet (G) Sn-5(Ni10Fe)-35Ni A strip-shaped base metal sheet (G) of a predetermined thickness was obtained in the same manner as the manufacturing method for base metal sheet (A), except that a metal powder mixture was prepared by stirring 60 parts by mass of first metal powder, 5 parts by mass of second metal powder, and 35 parts by mass of third metal powder (2).

[0224] Covering sheets (X) to (Z) were manufactured using the following procedure. The following raw materials were used: Sn, Sn-3Ag-0.5Cu alloy, and Sn-5Sb alloy.

[0225] Sn, melting point 232°C Sn-3Ag-0.5Cu (Ag3 mass%, Cu0.5 mass%, balance Sn), melting point 220℃ Sn-5Sb (5% Sb by mass, the remainder being Sn), melting point 243°C

[0226] Covering sheet (X) Sn After processing Sn into a sheet, it was rolled to a predetermined thickness and cut to a predetermined size to obtain a strip-shaped covering sheet (X) of a predetermined thickness.

[0227] Covering sheet (Y) Sn-3Ag-0.5Cu Except for using a Sn-3Ag-0.5Cu alloy instead of Sn, a coating sheet (Y) of a predetermined thickness was obtained in the same manner as the manufacturing method for the coating sheet (X).

[0228] Covering sheet (Z) Sn-5Sb Except for using a Sn-5Sb alloy instead of Sn, a coating sheet (Z) of a predetermined thickness was obtained in the same manner as the coating sheet (X) in the manufacturing method.

[0229] <Manufacturing of bonding materials> The bonding materials for each example were prepared using base metal sheets (A) to (G) and coating sheets (X) to (Z). The thicknesses of the base metal layer and the coating layer in the bonding materials for each example were as shown in Tables 1 to 8.

[0230] (Example A1) A coating sheet (X) was rolled onto one surface of a base metal sheet (A) to obtain a metal sheet. Next, the obtained single metal sheet was bent and rolled while bringing the surfaces of the base metal layer into contact with each other, to obtain a bonding material of Example A1 in which both surfaces of the base metal layer (A) were coated with the coating layer (X). In this bonding material, the thickness of the base metal layer (A) was 150 μm, and the thickness of the coating layer (X) was 75 μm.

[0231] (Examples A2 to A11) As shown in Table 1, bonding materials of Examples A2 to A6 and A8 to A11 were produced in the same manner as in Example A1, except that the bonding material was produced using the base metal sheet (A) and the coating sheets (X) to (Z) such that the base metal layer and the coating layer had predetermined thicknesses. In Example A7, a bonding material was produced in the same manner as in Example A1, except that only one surface of the base metal sheet (A) was coated with the coating sheet (X).

[0232] (Comparative Examples A1 to A7) As shown in Table 2, Comparative Examples A1 to A7 were produced in the same manner as in Example A1, except that the base metal sheet (A) was used and no coating sheet was used, and the base metal layer was formed into a shape such that it had a predetermined thickness.

[0233] (Examples B1 to B3, C1 to C4, D1 to D4, E1 to E4, F1 to F4, G1 to G4) As shown in Tables 3 to 8, bonding materials of each example were produced in the same manner as in Example A1, except that the base metal sheets (B) to (G) and the coating sheet (X) were used to produce the bonding material such that the base metal layer and the coating layer had predetermined thicknesses. An SEM image showing a cross-section in the thickness direction of the bonding material of Example C1 is shown in FIG. 2.

[0234] (Comparative Examples B1 to B3, C1 to C4, D1 to D4, E1 to E2, F1 to F4, G1 to G4) As shown in Tables 3 to 8, each comparative example was produced in the same manner as in Example A1, except that the base metal sheets (B) to (G) were used and no coating sheet was used, and the base metal layer was formed into a shape such that it had a predetermined thickness.

[0235] <Rating> Solder joints were manufactured using the fabricated joining material as described below, and the void ratio at the joint was measured.

[0236] ≪Manufacturing of Solder Joints≫ The bonding material for each example was cut to a size of 5 mm x 5 mm to obtain test specimens for each example. Each test specimen was mounted on an electroless nickel-plated copper substrate measuring 50 mm x 50 mm with a thickness of 0.5 mm. The surface roughness of the substrate was 0.31 μm for Sa and 8.53 μm for Sz. Surface roughness was measured using a laser microscope VK-X1000 (Keyence). A 0.5mm thick, 5mm x 5mm copper plate was mounted on top of the bonding material and soldered in place. Subsequently, solder joints were fabricated in a reflow oven under pressure in a formic acid atmosphere using a profile with a peak temperature of 250°C and a cooling rate of 2°C / sec.

[0237] ≪Evaluation of Void Suppression Ability≫ The void ratio at the joint of the fabricated solder joints was measured as follows. The evaluation results based on these measurements are shown in Tables 1 to 9.

[0238] [Measurement of void fraction at the joint] (1)Measurement method The fabricated solder joints were sealed with resin, polished to expose the joint cross-section, and cross-sectional SEM images were taken using an electron microscope (JEOL Ltd., JSM-7000F). From these cross-sectional SEM images, the void ratio (area %) was calculated for the entire area joined by the bonding material, excluding the upper and lower members. For the calculations, the image analysis software "Scandium" manufactured by Seika Digital Image Co., Ltd. was used to calculate the content of intermetallic compounds, Sn, Bi, and In (each in area %) at the bonding site from the contrast. The sum of the intermetallic compound content, Sn content, Bi content, In content, and void area percentages at the joint was set to 100 area percentage.

[0239] (2) Criteria for determining void fraction suppression ability A. The void ratio was less than 20%. B. The void ratio was between 20% and 25%. The void fraction of C was 25% or higher.

[0240] <<Evaluation of heat resistance>> For solder joints prepared using the bonding materials of Example A1, Example A6, and Comparative Example A7, the shear strength of the solder joint was measured as follows, and the heat resistance was evaluated. These measurement results are shown in Table 10.

[0241] [Measurement of shear strength] The shear strength (N) of the fabricated solder joints was measured at the joint area using a shear strength measuring device (STR-1000, manufactured by Resca Co., Ltd.) under conditions of 6.0 mm / min and 250°C. A higher shear strength indicates better heat resistance of the solder joint.

[0242] [Table 1]

[0243] [Table 2]

[0244] [Table 3]

[0245] [Table 4]

[0246] [Table 5]

[0247] [Table 6]

[0248] [Table 7]

[0249] [Table 8]

[0250] [Table 9]

[0251] [Table 10]

[0252] The results shown in Tables 1-9 confirm that the occurrence of voids was suppressed in each example with a coating layer compared to each comparative example without a coating layer. The results shown in Tables 1-9 confirm that the examples with a thickness ratio of 2 to 58 (represented by the base metal layer / coating layer) exhibited superior void suppression capabilities. The results shown in Table 10 confirm that the examples in which the ratio of the base metal layer to the coating layer thickness was 2 or more exhibited superior heat resistance at the solder joints compared to the comparative example in which the thickness ratio was 1.

Claims

1. A bonding material comprising a base metal layer and a coating layer covering at least one surface of the base metal layer, The aforementioned base metal layer contains a first metal containing Sn and a second metal consisting of an alloy containing Ni and Fe. The Sn content in the first metal is 20% by mass or more and 100% by mass or less, relative to the total mass of the first metal. The Ni content in the second metal is 80% by mass or more and 99% by mass or less, relative to the total mass of the second metal. The Fe content in the second metal is 1% by mass or more and 20% by mass or less, relative to the total mass of the second metal. The coating layer contains a metal with a lower melting point than the second metal. The content of a metal having a lower melting point than the second metal in the coating layer is 10% by mass or more and 100% by mass or less, relative to the total mass of the coating layer. A bonding material in which the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 or more, expressed as a ratio of base metal layer / coating layer.

2. The bonding material according to claim 1, wherein the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 300, expressed as a ratio of base metal layer / coating layer.

3. The bonding material according to claim 1 or 2, wherein the thickness of the coating layer is 1 to 150 μm.

4. The bonding material according to claim 1 or 2, wherein both sides of the base metal layer are each covered with the coating layer.

5. The content of the second metal in the base metal layer is 1% by mass or more and 70% by mass or less, based on the total mass of the first metal and the second metal. The bonding material according to claim 1 or 2, wherein the content of the second metal in the coating layer is less than 15% by mass of the total mass of the coating layer.

6. The bonding material according to claim 1 or 2, wherein the base metal layer further contains a third metal whose entire surface is formed of a metal containing Ni.

7. The Ni content in the Ni-containing metal forming the entire surface of the third metal is 50% by mass or more and 100% by mass or less, relative to the total mass of the metal forming the entire surface of the third metal. The bonding material according to claim 6, wherein the content of the third metal is 1 to 70% by mass with respect to the total mass of the first metal, the second metal, and the third metal.

8. A bonding material comprising a base metal layer and a coating layer covering at least one surface of the base metal layer, The substrate metal layer has a metal structure comprising a first phase which is a continuous phase and a second phase which is dispersed in the first phase. The first phase is composed of a metal containing Sn, The second phase is composed of an alloy containing Ni and Fe, The Sn content in the metal constituting the first phase is 20% by mass or more and 100% by mass or less, relative to the total mass of the metal constituting the first phase. The Ni content in the alloy constituting the second phase is 80% by mass or more and 99% by mass or less, relative to the total mass of the alloy constituting the second phase. The Fe content in the alloy constituting the second phase is 1% by mass or more and 20% by mass or less, relative to the total mass of the alloy constituting the second phase. The coating layer has a metallic structure comprising a metallic phase composed of a metal with a lower melting point than the alloy containing Ni and Fe. The content of the metal in the coating layer, which has a lower melting point than the alloy containing Ni and Fe, is 10% by mass or more and 100% by mass or less, relative to the total mass of the coating layer. A bonding material in which the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 or more, expressed as a ratio of base metal layer / coating layer.

9. The joining material according to claim 8, wherein at least one surface of the base metal layer and the coating layer are pressed together.

10. A solder joint formed using the joining material described in any one of claims 1, 2, 8, and 9.

11. A method for manufacturing a bonding material having a base metal layer and a coating layer that covers at least one surface of the base metal layer, The process includes pressing a coating sheet onto at least one surface of a base metal sheet to cover the surface with the coating layer, The aforementioned base metal sheet contains a first metal containing Sn and a second metal consisting of an alloy containing Ni and Fe. The Sn content in the first metal is 20% by mass or more and 100% by mass or less, relative to the total mass of the first metal. The Ni content in the second metal is 80% by mass or more and 99% by mass or less, relative to the total mass of the second metal. The Fe content in the second metal is 1% by mass or more and 20% by mass or less, relative to the total mass of the second metal. The coating sheet contains a metal with a lower melting point than the second metal. The content of a metal having a lower melting point than the second metal in the coating sheet is 10% by mass or more and 100% by mass or less, relative to the total mass of the coating sheet. A method for manufacturing a bonding material, wherein the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 or more, expressed as a ratio of base metal layer / coating layer.

12. The method for manufacturing a bonding material according to claim 11, wherein the base metal layer further contains a third metal whose entire surface is formed of a metal containing Ni.

13. A method for manufacturing a solder joint, comprising forming a joint between objects using a joining material manufactured by the method for manufacturing a joining material described in claim 11 or 12.

14. The bonding material according to claim 1, wherein the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 100, expressed as a ratio of base metal layer / coating layer.

15. The aforementioned base metal layer further contains a third metal having a structure consisting of a core portion and a surface layer covering the core portion. The composition of the metal forming the surface layer of the third metal is different from the composition of the first metal and the second metal. The metal forming the surface layer of the third metal consists only of Ni, or includes Ni and a metal other than Ni. The bonding material according to claim 1 or 2, wherein the Ni content in the metal forming the surface layer of the third metal is 50% by mass or more with respect to the total mass of the metal forming the surface layer of the third metal.

Images