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

Joining material and manufacturing method thereof, and solder joint and manufacturing method thereof

[0001] This application claims priority to Japanese Patent Application No. 2024-008258, filed on January 23, 2024, the contents of which are incorporated herein by reference.

[0002] In recent years, as the operating environment of power semiconductor elements using silicon carbide (SiC) and the like has become hotter, the temperature at solder joints can reach approximately 250 to 280°C. For this reason, there is a demand for high-temperature solder that does not melt when operating under such high-temperature conditions.

[0003] Preformed solder is used as a soldering material for producing such high-temperature solder joints. Preformed solder is a molded product obtained by processing solder into various shapes such as a square, ribbon, or disk. For example, a preformed solder has been proposed that is produced by compressing a mixed powder of Sn metal powder and a metal powder made of an alloy of Ni and Fe (see Patent Document 1).

[0004] Patent No. 7014991

[0005] As described in Patent Document 1, preformed solder can suppress voids compared to TLP paste. However, when preformed solder as described in Patent Document 1 is used, there are areas where metal powder made of an alloy of Ni and Fe is exposed on the joint surface of the preformed solder that comes into contact with the objects to be joined. A new problem has been discovered in that the alloy of Ni and Fe has a high melting point and almost no wetting action, making it prone to voids in the solder joint.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a bonding material and a manufacturing method thereof, as well as a solder joint and a manufacturing method thereof, which can suppress the occurrence of voids in solder joints.

[0007] The present invention includes the following aspects. [1] A bonding material having a base metal layer and a coating layer coating at least one surface of the base metal layer, wherein the base metal layer contains a first metal containing Sn and a second metal made of an alloy containing Ni and Fe, and the coating layer contains a metal having 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, expressed as base metal layer / coating layer, is 2 or more. [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, expressed as base metal layer / coating layer, is 2 to 300. [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 surfaces of the base metal layer are each coated 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, relative to the total mass of the first metal and the second metal; the content of the 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; and the content of the second metal in the coating layer is less than 15% by mass, relative 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 content of Ni in the Ni-containing metal that forms 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 metals that form the entire surface of the third metal, and the content of the third metal is 1 to 70% by mass, relative to the total mass of the first metal, the second metal, and the third metal.[8] A bonding material having a base metal layer and a coating layer coating at least one surface of the base metal layer, wherein the base metal layer has a metallographic structure including a first continuous phase and a second dispersed phase, the first phase being composed of a metal containing Sn, the second phase being composed of an alloy containing Ni and Fe, the coating layer having a metallographic structure including a metal phase having a lower melting point than the alloy containing Ni and Fe, and 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 2 or more. [9] The bonding material according to [8], which is a clad material in which at least one surface of the base metal layer and the coating layer are pressure-bonded.

[10] A solder joint formed using the bonding material according to any one of [1] to [9].

[11] A method for producing a bonding material having 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 coat the surface with the coating layer, wherein the base metal sheet contains a first metal containing Sn and a second metal made of an alloy containing Ni and Fe, the coating sheet contains a metal having 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, expressed as base metal layer / coating layer, is 2 or more.

[12] The method for producing the bonding material described in

[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 producing a solder joint, comprising forming a joint between objects using a bonding material produced by the method for producing a bonding material described in

[11] or

[12] .

[0008] According to the present invention, it is possible to provide a bonding material and a manufacturing method thereof, as well as a soldered joint and a manufacturing method thereof, which can suppress the occurrence of voids in a soldered joint.

[0009] FIG. 1 is a perspective view of a bonding material 1A according to the first embodiment. FIG. 2 is a schematic diagram showing a cross section in the thickness direction of the bonding material 1A according to the first embodiment. FIG. 3 is an SEM image showing a cross section in the thickness direction of the bonding material 1B according to the second embodiment. FIG. 4 is a schematic diagram showing a cross section in the thickness direction of a bonding material 1D obtained by a pressure-bonding step A in an embodiment of a method for manufacturing a bonding material. FIG. 5 is a schematic diagram showing a pressure-bonding step B1 in an embodiment of a method for manufacturing a bonding material. FIG. 6 is a schematic diagram showing a pressure-bonding step B2 in an embodiment of a method for manufacturing a bonding material. FIG. 7 is a schematic diagram showing a pressure-bonding step B3 in an embodiment of a method for manufacturing a bonding material. FIG. 8 is a schematic diagram showing a cross section of a third metal 30A in the bonding material according to the third embodiment. FIG. 9 is an SEM image showing a cross section in the thickness direction of the bonding material 1C according to the fourth embodiment. FIG. 10 is a schematic diagram showing a cross section of a third metal 30B in the bonding material according to the fifth embodiment.

[0010] In this specification, the terms "comprise" and "containing" are concepts that encompass all of "comprise," "consist essentially of," and "consist only of," respectively.

[0011] In this specification, the terms "first metal," "second metal," "third metal," and "fourth metal" may refer to "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," respectively. In this specification, the terms "first metal powder," "second metal powder," "third metal powder," and "fourth metal powder" may refer to "particle groups formed of the first metal," "particle groups formed of the second metal," "particle groups formed of the third metal," and "particle groups formed of the fourth metal," respectively.

[0012] (Bonding material: first embodiment) As illustrated in Fig. 1A, a bonding material 1A according to the first embodiment is square-shaped. Fig. 1B is a schematic diagram showing a cross section of the bonding material 1A according to the first embodiment. As illustrated in Fig. 1B, the bonding material 1A has a base metal layer 2A and coating layers 3A that respectively cover both surfaces (i.e., Sa1 and Sa2) of the base metal layer 2A. In Fig. 1B, Ta2 indicates the thickness of the base metal layer 2A, and Ta3 indicates 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 the composition 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 voids between the first metals by plastic deformation. Furthermore, the first metal containing Sn can ensure general performance such as wettability as a soldering material.

[0016] The first metal may contain a metal other than Sn. Examples of metals 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 type or two or more types. The group of metals other than Sn can be arbitrarily selected from these metals.

[0017] The metal that may be contained in the first metal may be either Sn or a metal other than Sn, or may be an alloy of Sn and a metal other than Sn.

[0018] The first metal may be, for example, Sn alone, 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.

[0019] The first metal may contain unavoidable impurities in addition to the above-mentioned metals. Even if the first metal contains unavoidable impurities, the effects of the present invention are not affected. 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, and may be 250° C. or lower, or may be 116 to 200° C. When the melting point of the first metal is equal to or lower than the upper limit of the above-mentioned preferred range, it becomes easier to ensure the wettability of the solder.

[0021] As used herein, the "melting point of the metal to be measured, or the 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 refers to the temperature at which the amount of heat absorbed per unit time is highest, based on the results of DSC measurement of the metal to be measured. If the metal to be measured has one peak in DSC measurement, the melting point of the metal to be measured refers to the temperature at the top of that peak. If the metal to be measured has multiple peaks in DSC measurement, the melting point of the metal to be measured refers to the temperature at the top of the peak with the highest amount of heat absorbed per unit time. The same applies to the melting point of the metal powder to be measured. The melting points of the first metal and the fourth metal can be measured, for example, using a DSC7020 manufactured by Hitachi High-Tech Science Corporation. The melting points of the second metal and the third metal, described below, can be measured, for example, using a DSC404-F3 Pegasus manufactured by NETZSCH.

[0022] The content of Sn in the first metal is preferably 20% by mass or more and 100% by mass or less, based on the total mass of the first metal. In order to fully exhibit the properties of Sn, the content of Sn 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, based on the total mass of the first metal.

[0023] <Second Metal> The second metal is an alloy containing Ni and Fe. The alloy in the second metal contains Ni and Fe, and preferably 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 600 to 1600°C. If the melting point of the alloy in the second metal is above the lower limit of the above-mentioned preferred range, the shear strength of the solder joint is likely to be increased even in a high-temperature operating environment.

[0024] The alloy of the second metal may contain a metal 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 a metal other than these, and among these, an alloy of Ni and Fe is preferable.

[0025] Examples of metals other than Ni and Fe that may be contained in 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 include one type or two or more types. 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 above-mentioned metals. Even if the second metal contains unavoidable impurities, the effects of the present invention are not affected. The second metal may be one type or two or more types.

[0027] The Ni content in the second metal is preferably 80% by mass or more and 99% by mass or less, more preferably 85% by mass or more and 95% by mass or less, based on 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, more preferably 5% by mass or more and 15% by mass or less, based on the total mass of the second metal. When the Ni and Fe contents in the second metal are within the above-mentioned preferred ranges, intermetallic compounds are formed at an earlier stage, and the generation of voids can be suppressed.

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

[0029] The particle size of the second metal is preferably 0.1 to 1000 μm, more preferably 1 to 100 μm, and even more preferably 5 to 50 μm. When the particle size of the second metal is equal to or greater than the lower limit of the above-mentioned preferred range, wettability is easily ensured, and when the particle size is equal to or less than the upper limit of the above-mentioned preferred range, an intermetallic compound is more easily formed.

[0030] <Relationship between the Contents of the First Metal and the Second Metal> In the base metal layer of the bonding material according to the first embodiment, the content of the first metal is preferably 30 mass%, 60 mass%, 80 mass%, 90 mass%, or 97 mass% relative to the total mass (100 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 first metal may be 30 to 99 mass%, or may be 30 to 97 mass%, relative to the total mass (100 mass%) of the first metal and the second metal.

[0031] In the base metal layer of the bonding material according to the first embodiment, the content of the second metal is preferably 3 mass%, 10 mass%, 20 mass%, 40 mass%, or 70 mass% relative to the total mass (100 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 mass%, or may be 3 to 70 mass%, relative to the total mass (100 mass%) of the first metal and the second metal. By having the content of the second metal within the above-mentioned preferred range, the heat resistance of the solder joint is further improved.

[0032] 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 does not exceed 100 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 or 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 above-mentioned preferred range, voids in the solder joint can be more easily suppressed, and the heat resistance of the solder joint can be 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, and even more preferably 90% by mass or more and 100% by mass or less, relative to the total mass of the base metal layer, and may be 100% by mass.

[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. When the thickness of the base metal layer is equal to or greater than the above-mentioned lower limit, the heat resistance of the solder joint can be more easily improved. When the thickness is equal to or less than the above-mentioned upper limit, the generation of voids in the solder joint that contacts the object to be joined can be more easily suppressed.

[0036] The thickness of the base metal layer is, for example, 1 to 5000 μm, 3 to 5000 μm, 5 to 5000 μm, 10 to 5000 μm, 15 to 5000 μm, 20 to 5000 μm, 25 to 5000 μm, 30 to 5000 μm, 40 to 5000 μm, 50 to 5000 μm, 75 to 5000 μm, 100 to 500 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 , 1 to 350 μm, 1 to 300 μm, 1 to 290 μm, 1 to 250 μm, 1 to 200 μm, 1 to 175 μm, 1 to 150 μm, 1 to 125 μm, 1 to 100 μm, 1 to 75 μm, 1 to 50 μm, 1 to 40 μm, 1 to 30 μm, 1 to 25 μm, 1 to 20 μm, or 1 to 15 μm. When the thickness of the base metal layer is equal to or greater than the above lower limit, the heat resistance of the soldered joint is more easily improved. When the thickness is equal to or less than the above upper limit, the generation of voids in the soldered joint that comes into contact with the object to be joined is more easily suppressed.

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

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

[0039] The coating layer may be Sn alone, 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. The coating layer may be In alone, 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, examples of metals other than Sn that may be contained include Ag, Cu, In, Bi, Ni, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, and As. The metal other than Sn may contain one type or two or more types. The group of metals other than Sn can be arbitrarily selected from these metals. Furthermore, when the coating layer contains In, examples of metals other than In that may be contained include Sn, Ag, Cu, Bi, Ni, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, and As. The metal other than In may contain one type or two or more types. 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 above-mentioned metals. Even if the coating layer contains unavoidable impurities, the effects of the present invention are not affected.

[0042] When the coating layer contains Sn, the content of Sn 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 to fully exhibit the properties of Sn, the content of Sn in the solder is preferably 40% by mass or more, more preferably 60% by mass or more, particularly preferably 80% by mass or more, and most preferably 90% by mass or more, and may be 95% by mass or more, or may be 100% by mass. Furthermore, when the coating layer contains In, the content of In 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 to fully exhibit the properties of In, the content of In in the solder is preferably 20% by mass or more, more preferably 40% by mass or more, particularly preferably 60% by mass or more, and most preferably 80% by mass or more, or may be 100% by mass.

[0043] The coating layer may or may not contain the second metal described above in the [base metal layer], and preferably does not contain it. When the coating layer contains the second metal, the content of the second metal in the coating layer is preferably less than 15 mass %, more preferably 10 mass % or less, even more preferably 1 mass % or less, and particularly preferably 0.1 mass % or less, relative to 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. When the thickness of the coating layer is equal to or greater than the above-mentioned lower limit, it is easier to suppress the occurrence of voids in the solder joint that contacts the object to be joined. When the thickness is equal to or less than the above-mentioned upper limit, it is easier to improve the heat resistance of the solder joint.

[0045] The thickness of the coating layer may be, for example, 1 to 150 μm, 3 to 150 μm, 5 to 150 μm, 7.5 to 150 μm, 10 to 150 μm, 12.5 to 150 μm, 15 to 150 μm, 20 to 150 μm, 25 to 150 μm, 30 to 150 μm, 40 to 150 μm, 50 to 150 μm, 75 to 150 μm, 1 to 125 μm, 1 to 100 μm, 1 to 75 μm, 1 to 50 μm, 1 to 40 μm, 1 to 30 μm, 1 to 25 μm, 1 to 20 μm, 1 to 15 μm, 1 to 12.5 μm, 1 to 10 μm, 1 to 7.5 μm, 1 to 5 μm, or 1 to 3 μm. When the thickness of the coating layer is equal to or greater than the lower limit, it is easier to suppress the generation of voids in the solder joint that contacts the object to be joined.When the thickness is equal to or less than the upper limit, it is easier to improve the heat resistance of the solder joint.

[0046] In this specification, the "thickness of the coating layer" refers to the thickness of the coating layer that coats one surface of the base metal layer. That is, even when both surfaces of the base metal layer are coated with coating layers, the "thickness of the coating layer" refers to the thickness of the coating layer that coats one surface of the base metal layer, out of the two coating layers.

[0047] The number of coating layers covering one surface of the base metal layer may be 1 or 2. When the number of coating layers covering one surface of the base metal layer is 2 or more, the thickness of the coating layer covering one surface means the total thickness of all the coating layers covering one surface.

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

[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 may be, for example, 2 to 5300 μm, 2 to 4000 μm, 2 to 3000 μm, 2 to 2000 μm, 2 to 1750 μm, 2 to 1510 μm, 2 to 1200 μm, 2 to 1000 μm, 2 to 750 μm, 2 to 500 μm, 2 to 400 μm, 2 to 300 μm, 2 to 250 μm, 2 to 200 μm, 2 to 150 μm, 2 to 100 μm, 2 to 75 μm, 2 to 50 μm, 2 to 40 μm, 2 to 30 μm, 5 to 5300 μm, 10 It may be up to 5300 μm, 15 to 5300 μm, 20 to 5300 μm, 30 to 5300 μm, 40 to 5300 μm, 50 to 5300 μm, 75 to 5300 μm, 100 to 5300 μm, 150 to 5300 μm, 200 to 5300 μm, 250 to 5300 μm, 300 to 5300 μm, 400 to 5300 μm, 500 to 5300 μm, 750 to 5300 μm, 1000 to 5300 μm, or 1200 to 5300 μm.

[0051] In this specification, the ratio of the thickness of the base metal layer to the thickness of the coating layer means a 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 the ratio of 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. When the ratio expressed as base metal layer / coating layer is within the above range, the heat resistance of the solder joint can be more easily improved, and further, the occurrence of voids in the solder joint in contact with the object to be joined can be more easily suppressed.

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

[0054] For the bonding material according to the first embodiment, the above-mentioned specifications regarding the thickness of the base metal layer and the coating layer, the ratio between the thickness of the base metal layer and the thickness of the coating layer, the content of the first metal and the second metal, etc. may be combined in any manner.

[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). In the bonding material according to the first embodiment, the thickness of the coating layer is preferably 1 to 150 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 300, more preferably 5 to 150 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 200, even more preferably 5 to 150 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 100, and particularly preferably 5 to 75 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 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, the heat resistance of the solder joint is more easily improved and the occurrence of voids in the solder joint is more easily suppressed.

[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 thickness of the base metal layer to the thickness of the coating layer expressed as base metal layer / coating layer of 2 to 500, a content of the first metal of 30 to 97 mass% with respect to the total mass (100 mass%) of the first metal and the second metal, a content of the second metal of 3 to 70 mass% with respect to the total mass (100 mass%) of the first metal and the second metal, and a mass ratio of the content of the first metal to the content of the second metal of 0.4 or more and 35 or less, expressed as the content of the first metal / the content of the second metal. The bonding material according to the first 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 thickness of the base metal layer to the thickness of the coating layer expressed as base metal layer / coating layer of 2 to 58, a content of the first metal of 30 to 97 mass% with respect to the total mass (100 mass%) of the first metal and the second metal, a content of the second metal of 3 to 70 mass% with respect to the total mass (100 mass%) of the first metal and the second metal, and a mass ratio of the content of the first metal to the content of the second metal of 0.4 or more and 35 or less, expressed as the content of the first metal / the content of the second metal.

[0057] The bonding material according to the first 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 thickness of the base metal layer to the thickness of the coating layer expressed as base metal layer / coating layer of 2 to 500, a content of the first metal of 30 to 97 mass% with respect to the total mass (100 mass%) of the first metal and the second metal, a content of the second metal of 3 to 70 mass% with respect to the total mass (100 mass%) of the first metal and the second metal, and a mass ratio of the content of the first metal to the content of the second metal of 0.4 or more and 35 or less, expressed as the content of the first metal / the content of the second metal.

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

[0059] The bonding material according to the first embodiment can be manufactured by a known manufacturing method, for example, a hot dip plating method or a rolling method.

[0060] ■Explanation of Effects■ The bonding material according to the first embodiment described above includes a base metal layer and a coating layer that coats at least one surface of the base metal layer. By including the coating layer, the bonding material can suppress the generation of voids in the soldered joint. The reason for this effect is as follows: On the surface of the base metal layer containing metal powder made of an alloy of Ni and Fe, there are portions where the metal powder made of the alloy of Ni and Fe is exposed. The alloy of Ni and Fe has a high melting point and extremely low wetting action, so voids are likely to occur in the soldered joint. The coating layer covers the base metal layer so that the alloy of Ni and Fe is not exposed on the surface of the base metal layer. Therefore, when objects to be bonded are bonded using the bonding material according to the first embodiment, the generation of voids in the joint can be suppressed.

[0061] (Bonding material: second embodiment) Fig. 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 Fig. 2A, a bonding material 1B has a base metal layer 2B and coating layers 3B that coat both surfaces of the base metal layer 2B. The base metal layer 2B shown in Fig. 2A has a metal structure including a first phase 10 that is a continuous phase and a second phase 20 dispersed in the first phase. The coating layer 3B shown in Fig. 2A has a metal structure including a metal phase composed of a metal that contains Ni and Fe and has a melting point lower than that of the alloy. 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 Fig. 2A is the bonding material of Example C1 described later in the Examples. In the bonding material 1B, the thickness of the base metal layer is 150 µm, and the thickness of the coating layer is 75 µm. In the base metal layer 2B, the content of the first phase is 80 mass% with respect to the total mass of the base metal layer, and the content of the second phase is 20 mass% with respect to the total mass of the base metal layer. The content of Ni in the second phase is 90 mass% with respect to the total mass of the second phase, and the content of Fe in the second phase is 10 mass% with respect to the total mass of the second phase.

[0063] The bonding material 1B illustrated in Fig. 2A is a clad material in which coating layers are bonded to both surfaces of a base metal layer. In the clad material, an intermetallic compound may be formed at the contact portion between the base metal layer and the coating layer. As will be described later, the bonding material according to the second embodiment can be produced, for example, by pressure-bonding 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 below, the base metal sheet can be manufactured by a method such as rolling forming using a metal powder containing, for example, a first metal including Sn and a second metal made of an alloy including Ni and Fe. The base metal sheet can also be said to be a solder preform.

[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, crystal grain boundaries may exist between the metal crystals containing Sn.

[0066] The melting point of the metals constituting the first phase as a whole can be measured in the same manner as the melting point of the first metal. When the first phase contains multiple types of metals, the melting point of the metals constituting the first phase as a whole is determined by 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. The melting point of the metals constituting the second phase as a whole is defined in the same manner. The melting point of the metals constituting the entire surface of the third phase is also defined in the same manner. When the entire third phase has a uniform composition, the melting point of the metals constituting the third phase as a whole is also defined in the same manner. When the third phase has a structure consisting of a core portion and a surface layer covering the core portion, the melting point of the metals constituting the surface layer of the third phase as a whole is also defined in the same manner, and the melting point of the metals constituting the core portion of the third phase as a whole is also defined in the same manner.

[0067] The explanation for the melting point of the metals 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, its content, etc. is the same as that of the <second metal> in the first embodiment.

[0069] The explanation for the melting point of the alloy as a whole that constitutes the second phase is the same as the explanation for the melting point of the second metal.

[0070] In this specification, the grain size of a phase can be measured and calculated from a cross-sectional structure containing the phase using an optical microscope, SEM, transmission electron microscope (TEM), etc. The grain size of a phase can be calculated by measuring the diameters of three or more phases and averaging these diameters.

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

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

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

[0074] In the base metal layer, the content of the alloy constituting the second phase is preferably 3 mass%, 10 mass%, 20 mass%, 40 mass%, or 70 mass% relative to the total mass (100 mass%) of the Sn-containing metal constituting the first phase and the Ni- and Fe-containing alloy constituting the second phase, and 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 mass%, or may be 3 to 70 mass%, relative to the total mass (100 mass%) of the Sn-containing metal constituting the first phase and the Ni- and Fe-containing alloy constituting the second phase. By having the content of the alloy constituting the second phase within the above-mentioned preferred range, the heat resistance of the solder joint is further improved.

[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 content of the alloy that constitutes the second phase does not exceed 100 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, expressed as a mass ratio of first phase / second phase, is preferably 0.43 or 32, and the upper and lower limits can be appropriately selected from these values. The mass ratio expressed by 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 expressed by first phase / second phase is within the above-mentioned preferred range, voids in the solder joint can be more easily suppressed and the heat resistance of the solder joint can be 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, and even more preferably 90% by mass or more and 100% by mass or less, relative to the total mass of the base metal layer, and may be 100% by mass.

[0078] In the bonding material according to the second embodiment, the explanation of the thicknesses 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. When the thickness of the base metal layer is equal to or greater than the lower limit, the heat resistance of the solder joint is more easily improved. When the thickness is equal to or less than the upper limit, the generation of voids in the solder joint that contacts the object to be joined is more easily suppressed.

[0080] The thickness of the base metal layer of the bonding material according to the second embodiment is, for example, 1 to 5000 μm, 3 to 5000 μm, 5 to 5000 μm, 10 to 5000 μm, 15 to 5000 μm, 20 to 5000 μm, 25 to 5000 μm, 30 to 5000 μm, 40 to 5000 μm, 50 to 5000 μm, 75 to 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 thickness of the base metal layer may be 0 μm, 1 to 350 μm, 1 to 300 μm, 1 to 290 μm, 1 to 250 μm, 1 to 200 μm, 1 to 175 μm, 1 to 150 μm, 1 to 125 μm, 1 to 100 μm, 1 to 75 μm, 1 to 50 μm, 1 to 40 μm, 1 to 30 μm, 1 to 25 μm, 1 to 20 μm, or 1 to 15 μm. When the thickness of the base metal layer is equal to or greater than the above lower limit, the heat resistance of the soldered joint is more easily improved. When the thickness is equal to or less than the above upper limit, the generation of voids in the soldered joint that comes into contact with the object to be joined is more easily suppressed.

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

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

[0083] The coating layer may or may not have the second phase described above in the [Base metal layer], and preferably does not have it. When the coating layer has the second phase, the content of the alloy containing Ni and Fe constituting the second phase in the coating layer is preferably less than 15 mass %, more preferably 10 mass % or less, even more preferably 1 mass % or less, and particularly preferably 0.1 mass % or less, relative to 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. When the thickness of the coating layer is equal to or greater than the lower limit, it is easier to suppress the occurrence of voids in the solder joint that contacts the object to be joined. When the thickness is equal to or less than the upper limit, it is 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 to 150 μm, 3 to 150 μm, 5 to 150 μm, 7.5 to 150 μm, 10 to 150 μm, 12.5 to 150 μm, 15 to 150 μm, 20 to 150 μm, 25 to 150 μm, 30 to 150 μm, 40 to 150 μm, 50 to 150 μm, 75 to 150 μm, 1 to 125 μm, 1 to 100 μm, 1 to 75 μm, 1 to 50 μm, 1 to 40 μm, 1 to 30 μm, 1 to 25 μm, 1 to 20 μm, 1 to 15 μm, 1 to 12.5 μm, 1 to 10 μm, 1 to 7.5 μm, 1 to 5 μm, or 1 to 3 μm. When the thickness of the coating layer is equal to or greater than the lower limit, it is easier to suppress the generation of voids in the solder joint that contacts the object to be joined.When the thickness is equal to or less than the upper limit, it is 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 to 5300 μm, 2 to 4000 μm, 2 to 3000 μm, 2 to 2000 μm, 2 to 1750 μm, 2 to 1510 μm, 2 to 1200 μm, 2 to 1000 μm, 2 to 750 μm, 2 to 500 μm, 2 to 400 μm, 2 to 300 μm, 2 to 250 μm, 2 to 200 μm, 2 to 150 μm, 2 to 100 μm, 2 to 75 μm, 2 to 50 μm, 2 to 40 μm, 2 to 30 μm, 5 to 5300 μm. μm, 10 to 5300 μm, 15 to 5300 μm, 20 to 5300 μm, 30 to 5300 μm, 40 to 5300 μm, 50 to 5300 μm, 75 to 5300 μm, 100 to 5300 μm, 150 to 5300 μm, 200 to 5300 μm, 250 to 5300 μm, 300 to 5300 μm, 400 to 5300 μm, 500 to 5300 μm, 750 to 5300 μm, 1000 to 5300 μm, or 1200 to 5300 μm.

[0088] The ratio of the thickness of the base metal layer to the thickness of the coating layer, expressed as the ratio of 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. When the ratio expressed as base metal layer / coating layer is within the above range, the heat resistance of the solder joint can be more easily improved, and further, the occurrence of voids in the solder joint in contact with the object to be joined can be more easily suppressed.

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

[0090] With regard to the bonding material according to the second embodiment, the above-mentioned specifications regarding the thickness of the base metal layer and the coating layer, the ratio between the thickness of the base metal layer and the thickness of the coating layer, the content of the metal containing Sn constituting the first phase and the alloy containing Ni and Fe constituting the second phase, etc. may be combined in any manner.

[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). In the bonding material according to the second embodiment, the thickness of the coating layer is preferably 1 to 150 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 300, more preferably 5 to 150 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 200, even more preferably 5 to 150 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 100, and particularly preferably 5 to 75 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 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, the heat resistance of the solder joint is more easily improved and the occurrence of voids in the solder joint is more easily suppressed.

[0092] In the bonding material according to the second embodiment, preferably, the thickness of the base metal layer is 150 to 1500 μm, the thickness of the coating layer is 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 a ratio expressed as base metal layer / coating layer, the content of the metal containing Sn constituting the first phase is 30 to 97 mass% with respect to 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% with respect to 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 metal containing Sn constituting the first phase to the content of the alloy containing Ni and Fe constituting the second phase is 0.4 to 35 as a mass ratio expressed as the content of the first metal / the content of the second metal. 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, expressed as the ratio of base metal layer / coating layer, the content of the Sn-containing metal constituting the first phase is 30 to 97 mass% with respect to the total mass (100 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 mass% with respect to the total mass (100 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 first metal to the content of the second metal is 0.4 or more and 35 or less, expressed as the mass ratio of the content of the first metal / the content of the second metal.

[0093] In the bonding material according to the second embodiment, preferably, the thickness of the base metal layer is 1 to 5000 μm, the thickness of the coating layer is 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 a ratio expressed as base metal layer / coating layer, the content of the metal containing Sn constituting the first phase is 30 to 97 mass% with respect to 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% with respect to 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 metal containing Sn constituting the first phase to the content of the alloy containing Ni and Fe constituting the second phase is 0.4 or more and 35 or less as a mass ratio expressed as the content of the first metal / the content of the second metal.

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

[0095] (Method for 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 coats at least both surfaces of the base metal layer. The method for manufacturing a bonding material according to this embodiment includes a pressure-bonding step A and any one of pressure-bonding steps B1 to B3.

[0096] <Compression bonding process A> In the compression bonding process A, a coating sheet is pressure-bonded to one surface of a base metal sheet to cover the surface with the coating layer. As illustrated in Fig. 2B , the compression bonding process A provides 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 having a lower melting point than the second metal. The coating sheet may be manufactured by a known method, for example, by preparing a metal having a predetermined composition to form the coating sheet, processing the metal into a plate, rolling it to a predetermined thickness, and cutting it to a predetermined size.

[0098] In this embodiment, the metals contained in the base metal sheet, their particle diameters, their contents, etc. are the same as those in the base metal layer of the bonding material. In this embodiment, the metals contained in the coating sheet, their contents, etc. are the same as those in the coating layer of the bonding material.

[0099] As a method for pressure bonding, a known rolling method can be used, and for example, processing can be performed using a twin-roll rolling mill. The number of times of rolling and the rolling load applied to the base metal sheet and the covering sheet can be appropriately set depending on the desired shape and thickness of the target bonding material. The rolling load is not particularly limited, but may be, for example, 0.1 to 20 kN. The number of times of rolling is not particularly limited, but may be 1 to 10 times. The surface temperature of the rolling roll is not particularly limited, but may be, for example, 50 to 150°C.

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

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

[0102] <Bonding Process B1> In the bonding process B1, two bonding materials are prepared, each having the base metal layer obtained in the bonding process A and a coating layer covering one side of the base metal layer. Hereinafter, the two bonding materials are referred to as the first bonding material and the second bonding material, respectively. As illustrated in FIG. 2C, in the bonding process B1, one side Sd2 of the base metal layer 2D of the first bonding material 1D and one side Sd2 of the base metal layer 2D of the second bonding material 1D are bonded together by pressure. The bonding process B1 results in a bonding material 1E having a base metal layer 2E and a coating layer 3E covering both sides (i.e., Se1 and Se2) of the base metal layer 2E. The bonding method in the bonding process B1 may be the same as the bonding method in the bonding process A.

[0103] <Bonding Step B2> In the bonding step B2, one bonding material is prepared, which includes the base metal layer obtained in the bonding step A and a coating layer covering one side of the base metal layer. As illustrated in FIG. 2D , in the bonding step B2, the bonding material 1D is bent and the surfaces Sd2 of the base metal layers 2D of the bonding material 1D are bonded together by pressure. The bonding step B2 results in a bonding material 1E having a base metal layer 2E and a coating layer 3E covering both sides (i.e., Se1 and Se2) of the base metal layer 2E. The bonding method in the bonding step B2 may be the same as the bonding method in the bonding step A.

[0104] <Bonding step B3> In the bonding step B3, one bonding material is prepared, which includes the base metal layer obtained in the bonding step A and a coating layer covering one side of the base metal layer. As illustrated in FIG. 2E, in the bonding step B3, a coating sheet 3D' is pressure-bonded to one side Sd2 of the base metal layer 2D of the bonding material 1D. The bonding step B3 results in a bonding material 1E having a base metal layer 2E and a coating layer 3E covering both sides (i.e., Se1 and Se2) of the base metal layer 2E. The bonding method in the bonding step B3 may be the same as the bonding method in the bonding step A.

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

[0106] <Compression molding process> In the compression molding process, a metal powder mixture containing a first metal powder containing Sn and a second metal powder made of an alloy containing Ni and Fe is compressed to produce a base metal sheet that is a preform solder.

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

[0108] The metal powder mixture can be compacted using a known rolling method, such as a twin-roll rolling mill. The number of rolling passes and the rolling load applied to the metal powder mixture can be appropriately set depending on 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 a rolling mill is used, the surface temperature of the rolling rolls is not particularly limited, but may be, for example, 50 to 150°C.

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

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

[0111] <Third Metal> The entire surface of the third metal is formed of a metal containing Ni. That is, 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 mass % or more and 100 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 500°C or more, and more preferably 600 to 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 of only Ni, or may contain a metal other than Ni. Examples of the metal forming the entire surface of the third metal include simple Ni, an alloy of Ni with a metal other than Ni, and a mixture of an alloy containing Ni and another metal, with simple Ni being preferred.

[0113] Examples of the metal other than Ni in the alloy of Ni and a metal 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 include one type or two or more types. 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 above-mentioned metals. Even if unavoidable impurities are contained, the effects of the present invention are not affected. The metal forming the entire surface of the third metal may be one type, or two or more types may be laminated.

[0115] When the metal forming the entire surface of the third metal is a metal containing Ni and a metal other than Ni, the content of Ni in the metal forming the entire surface is 50 mass% or more, preferably 70 mass% or more, more preferably 90 mass% or more, even more preferably 95 mass% or more, and particularly preferably 98 mass% or more, relative to the total mass of the metal forming the entire surface. When the metal forming the entire surface of the third metal contains Fe, the content of Fe in the metal forming the entire surface of the third metal is preferably 0 mass% or more and less than 5 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 equal to or greater than the lower limit of the preferred range, the thermal conductivity of the solder joint is easily increased.

[0117] The specific structure of the third metal will be described below with reference to examples. As described 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 a plurality of different compositions.

[0118] When the third metal has a uniform composition throughout, the third metal may be a metal consisting only of Ni, as described in (1-1) below, or may be a metal containing Ni and a metal other than Ni, as described in (1-2) below. Alternatively, when the third metal has a structure having a plurality of different compositions, as described in (2) below, the third metal may have a core portion and a surface layer. These cases will be described below.

[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 the compositions of the first metal and the second metal. In this case, the content of Ni in the metal forming the entire surface of the third metal is 100 mass% relative to 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% relative to the entire area (100%) of the surface of the third metal. The third metal may contain inevitable impurities in addition to Ni. Even if the third metal contains inevitable impurities, the effects of the present invention are not affected.

[0120] (1-2) When the third metal contains Ni and a metal other than Ni The composition of the third metal is different from the compositions of the first metal and the second metal. The third metal may be a mixture of Ni and a metal other than Ni, 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 in 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 in one kind or in two or more kinds. The group of metals other than Ni can be arbitrarily selected from these metals.

[0122] The third metal may contain inevitable impurities in addition to the above-mentioned metals. Even if inevitable impurities are contained, the effects of the present invention are not affected. The third metal (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 content of Ni 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 content of Fe in the third metal is preferably 0% by mass or more and less than 5% by mass, based on the total mass of the third metal.

[0124] (2) Case where the third metal has a structure consisting of a core portion and a surface layer covering the core portion As illustrated in Fig. 3, the third metal 30A has a core portion 301 and a surface layer 302 covering the core portion 301. Rc means the particle diameter of the core portion 301 (hereinafter, Rc may be referred to as the core diameter). Rs means 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 portion. The composition of the third metal is different from the compositions of the first metal and the second metal. The composition of the metal forming the surface layer of the third metal is different from the compositions of the first metal and the second metal.

[0126] Surface Layer The metal forming the surface layer of the third metal may consist of only Ni, or may be a metal containing Ni and a metal other than Ni. That is, the metal forming the surface layer of the third metal may be Ni alone, or may be an alloy of Ni and a metal other than Ni. The metal forming the surface layer of the third metal is preferably Ni alone.

[0127] Examples of metals other than Ni that may be contained in the metal forming 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 include one type or two or more types. 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 above-mentioned metals. Even if unavoidable impurities are contained, the effects of the present invention are not affected. The metal forming the surface layer of the third metal may be one type, or two or more types may be laminated.

[0129] When the metal forming the surface layer of the third metal is a metal containing Ni and a metal other than Ni, the content of Ni 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, relative to 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, the content of Fe in the metal forming the surface layer of the third metal is preferably 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 portion is covered with a surface layer. The surface layer may cover a portion of the core portion or the entire core portion, and preferably covers the entire core portion. In Fig. 3, the entire surface of core portion 301 is covered with surface layer 302. The proportion of the surface area of ​​the core portion covered with the surface layer is preferably 50% to 100% of the total surface area (100%) of the core portion, more preferably 70% to 100%, even more preferably 90% to 100%, particularly preferably 95% to 100%, and most preferably 100%.

[0131] The thickness Rs of the surface layer of the third metal may be, for example, 0.01 μm or more and 100 μm or less. The thickness of the surface layer 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 thickness of the surface layer 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 portion of the third metal, and the thickness Ri of the intermediate layer described below can be measured from the cross-sectional structure of the third metal using an optical microscope, SEM, transmission electron microscope (TEM), etc. The thickness Rs of the surface layer of the third metal can be measured using an Auger electron spectrometer.

[0133] Alternatively, the core diameter Rc of the core portion of the third metal can be measured as follows: When producing the third metal powder, the particle size of the metal powder prepared to be used as the core portion can be taken as the core diameter Rc.

[0134] The surface layer of the third metal may be a plated layer formed by plating, for example, known electroplating or electroless plating.

[0135] The melting point of the metal forming the surface layer of the third metal is greater than 300°C, preferably 500°C or higher, and more preferably 600 to 1600°C.

[0136] Core portion The metal forming the core portion of the third metal may be one type of elemental metal, a mixture of two or more types of elemental metal, an alloy formed from two or more types of metal elements, a mixture of alloys formed from two or more types of metal elements, or a mixture of an alloy formed from two or more types of metal elements and an elemental metal.

[0137] Examples of metals that may be contained in the core portion 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 contained alone or in combination of two or more. The metal group that may be contained in the core portion can be arbitrarily selected from these metals.

[0138] The core portion of the third metal may contain inevitable impurities in addition to the above-mentioned metals. Even if inevitable impurities are contained, the effects of the present invention are not affected. The metal forming the core portion 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 one type or two or more types.

[0141] <Relationship between the contents of the first metal, the second metal, and the third metal> 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 mass %, more preferably 30 to 90 mass %, and even more preferably 40 to 80 mass %, relative to 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 mass %, more preferably 3 to 30 mass %, relative to the total mass of the first metal, the second metal, and the third metal. When the content of the second metal is within the above-mentioned preferred range, the heat resistance of the solder joint is further improved.

[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 mass %, more preferably 5 to 50 mass %, relative to the total mass of the first metal, the second metal, and the third metal. When the content of the third metal is within the above-mentioned preferred range, the thermal conductivity of the solder joint can be more easily increased.

[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 mass %, more preferably 3 to 70 mass %, and even more preferably 20 to 60 mass %, relative to 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 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 mass %, more preferably 80 to 100 mass %, even more preferably 90 to 100 mass %, and may be 100 mass %, relative to 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, expressed as a mass ratio of the content of the first metal / the content of the second metal, is preferably from 0.1 to 100, more preferably from 1 to 50, and even more preferably from 4 to 30. When the mass ratio is within the above-mentioned preferred range, voids in the solder joint can be more easily suppressed, and the heat resistance of the solder joint can be 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, expressed as a mass ratio of the content of the first metal / the content of the third metal, is preferably from 0.1 to 100, more preferably from 0.3 to 20, and even more preferably from 1 to 5. When the mass ratio is within the above-mentioned preferred range, it becomes easier to suppress voids in the solder joint and to increase 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, expressed as a mass ratio of the content of the third metal / the content of the second metal, is preferably from 0.01 to 100, more preferably from 0.1 to 50, and even more preferably from 1 to 30. When the mass ratio is within the above-mentioned preferred range, the heat resistance of the solder joint is more likely to be improved, and the thermal conductivity of the solder joint is more likely to be increased.

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

[0151] In the bonding material according to the third embodiment, the explanation of the thicknesses 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, expressed as the ratio of base metal layer / coating layer, is, for example, preferably 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 to 5000 μm, 3 to 5000 μm, 5 to 5000 μm, 10 to 5000 μm, 15 to 5000 μm, 20 to 5000 μm, 25 to 5000 μm, 30 to 5000 μm, 40 to 5000 μm, 50 to 5000 μm, 75 to 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 thickness of the base metal layer may be 0 μm, 1 to 350 μm, 1 to 300 μm, 1 to 290 μm, 1 to 250 μm, 1 to 200 μm, 1 to 175 μm, 1 to 150 μm, 1 to 125 μm, 1 to 100 μm, 1 to 75 μm, 1 to 50 μm, 1 to 40 μm, 1 to 30 μm, 1 to 25 μm, 1 to 20 μm, or 1 to 15 μm. When the thickness of the base metal layer is equal to or greater than the above lower limit, the heat resistance of the soldered joint is more easily improved. When the thickness is equal to or less than the above upper limit, the generation of voids in the soldered joint that comes into contact with the object to be joined is more easily suppressed.

[0154] The thickness of the coating layer of the bonding material according to the third embodiment may be, for example, 1 to 150 μm, 3 to 150 μm, 5 to 150 μm, 7.5 to 150 μm, 10 to 150 μm, 12.5 to 150 μm, 15 to 150 μm, 20 to 150 μm, 25 to 150 μm, 30 to 150 μm, 40 to 150 μm, 50 to 150 μm, 75 to 150 μm, 1 to 125 μm, 1 to 100 μm, 1 to 75 μm, 1 to 50 μm, 1 to 40 μm, 1 to 30 μm, 1 to 25 μm, 1 to 20 μm, 1 to 15 μm, 1 to 12.5 μm, 1 to 10 μm, 1 to 7.5 μm, 1 to 5 μm, or 1 to 3 μm. When the thickness of the coating layer is equal to or greater than the lower limit, it is easier to suppress the generation of voids in the solder joint that contacts the object to be joined.When the thickness is equal to or less than the upper limit, it is 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 to 5300 μm, 2 to 4000 μm, 2 to 3000 μm, 2 to 2000 μm, 2 to 1750 μm, 2 to 1510 μm, 2 to 1200 μm, 2 to 1000 μm, 2 to 750 μm, 2 to 500 μm, 2 to 400 μm, 2 to 300 μm, 2 to 250 μm, 2 to 200 μm, 2 to 150 μm, 2 to 100 μm, 2 to 75 μm, 2 to 50 μm, 2 to 40 μm, 2 to 30 μm, 5 to 5300 μm. μm, 10 to 5300 μm, 15 to 5300 μm, 20 to 5300 μm, 30 to 5300 μm, 40 to 5300 μm, 50 to 5300 μm, 75 to 5300 μm, 100 to 5300 μm, 150 to 5300 μm, 200 to 5300 μm, 250 to 5300 μm, 300 to 5300 μm, 400 to 5300 μm, 500 to 5300 μm, 750 to 5300 μm, 1000 to 5300 μm, or 1200 to 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, expressed as base metal layer / coating layer, may be, for example, 2 to 500, 3 to 500, 5 to 500, 7.5 to 500, 10 to 500, 15 to 500, 20 to 500, 30 to 500, 50 to 500, 100 to 500, 200 to 500, 2 to 400, 2 to 350, 2 to 300, 2 to 250, 2 to 200, 2 to 150, 2 to 100, 2 to 75, 2 to 60, 2 to 58, 2 to 50, 2 to 30, 2 to 20, 2 to 15, 2 to 10, 2 to 7.5, 2 to 5, or 2 to 3. When the ratio of base metal layer / coating layer is within the above range, it becomes easier to improve the heat resistance of the soldered joint and to further suppress the generation of voids in the soldered joint that comes into contact with the object to be joined. When the ratio is equal to or greater than the lower limit of the above range, it becomes easier to improve the heat resistance of the soldered joint. When the ratio is equal to or less than the upper limit of the above range, it becomes easier to suppress the generation of voids in the soldered joint.

[0157] For 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 between the thickness of the base metal layer and the thickness of the coating layer, the structure of the third metal, the contents of the first metal, the second metal and the third metal, etc. may be combined in any manner.

[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). In the bonding material according to the third embodiment, the thickness of the coating layer is preferably 1 to 150 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 300, more preferably 5 to 150 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 200, even more preferably 5 to 150 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 100, and particularly preferably 5 to 75 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 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, the heat resistance of the solder joint is more easily improved and the occurrence of voids in the solder joint is more easily suppressed.

[0159] In the bonding material according to the third embodiment, 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 a ratio expressed as base metal layer / coating layer, the third metal is composed only of Ni, the content of the first metal is 30 to 90 mass% with respect to the total mass of the first metal, the second metal, and the third metal, the content of the second metal is 3 to 30 mass% with respect to the total mass of the first metal, the second metal, and the third metal, the content of the third metal is 5 to 50 mass% with respect to the total mass of the first metal, the second metal, and the third metal, the ratio of the content of the first metal to the content of the second metal is 4 or more and 30 or less as a mass ratio expressed as the content of the first metal / the content of the second metal, and the ratio of the content of the first metal to the content of the third metal is a mass ratio expressed as the content of the first metal / the content of the third metal. The ratio of the content of the second metal to the content of the third metal is 1 or more and 30 or less as a mass ratio expressed as the content of the third metal / the content of the second metal.

[0160] Alternatively, in the bonding material according to the third embodiment, 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 a ratio expressed as base metal layer / coating layer, the third metal has a structure consisting of a core portion and a surface layer coating the core portion, the third metal has a structure consisting of a core portion and a surface layer coating 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 mass % with respect to the total mass of the first metal, the second metal, and the third metal, and the content of the second metal is 0.01 to 0.02 The content of the third metal is 3 to 30% by mass with respect to the total mass of the first metal, the second metal, and the third metal, the content of the third metal is 5 to 50% by mass with respect to the total mass of the first metal, the second metal, and the third metal, the ratio of the content of the first metal to the content of the second metal, expressed as a mass ratio of the content of the first metal / the content of the second metal, is 4 or more and 30 or less, the ratio of the content of the first metal to the content of the third metal, expressed as a mass ratio of the content of the first metal / the content of the third metal, is 1 or more and 5 or less, and the ratio of the content of the second metal to the content of the third metal, expressed as a mass ratio of the content of the third metal / the content of the second metal, is 1 or more and 30 or less.

[0161] In the bonding material according to the third embodiment, preferably, the thickness of the base metal layer is 1 to 5000 μm, the thickness of the coating layer is 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 a ratio expressed as base metal layer / coating layer, the third metal is composed only of Ni, the content of the first metal is 30 to 90 mass% with respect to the total mass of the first metal, the second metal, and the third metal, the content of the second metal is 3 to 30 mass% with respect to the total mass of the first metal, the second metal, and the third metal, the content of the third metal is 5 to 50 mass% with respect to the total mass of the first metal, the second metal, and the third metal, the ratio of the content of the first metal to the content of the second metal is 4 or more and 30 or less as a mass ratio expressed as the content of the first metal / the content of the second metal, and the ratio of the content of the first metal to the content of the third metal is a mass ratio expressed as the content of the first metal / the content of the third metal. The ratio of the content of the second metal to the content of the third metal is 1 or more and 30 or less as a mass ratio expressed as the content of the third metal / the content of the second metal.

[0162] In the bonding material according to the third embodiment, preferably, the thickness of the base metal layer is 1 to 500 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 a ratio expressed as base metal layer / coating layer, the third metal is composed only of Ni, the content of the first metal is 30 to 90 mass% with respect to the total mass of the first metal, the second metal, and the third metal, the content of the second metal is 3 to 30 mass% with respect to the total mass of the first metal, the second metal, and the third metal, and the content of the third metal is is 5 to 50 mass% with respect to the total mass of the first metal, the second metal, and the third metal, the ratio of the content of the first metal to the content of the second metal, expressed as a mass ratio of the content of the first metal / the content of the second metal, is 4 or more and 30 or less, the ratio of the content of the first metal to the content of the third metal, expressed as a mass ratio of the content of the first metal / the content of the third metal, is 1 or more and 5 or less, and the ratio of the content of the second metal to the content of the third metal, expressed as a mass ratio of the content of the third metal / the content of the second metal, is 1 or more and 30 or less.

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

[0164] The bonding material according to the third embodiment can suppress the generation of voids in the solder joint, similar to the bonding material according to the first embodiment. In addition, the bonding material according to the third embodiment can further increase the thermal conductivity of the solder joint by containing a third metal in the base metal layer. The reason why such an effect is obtained is not clear, but is presumed to be as follows.

[0165] Compared with Cu, Ni, etc., intermetallic compounds have low thermal conductivity. For example, the thermal conductivity of Cu and Ni is 401 W / m·K and 88.5 W / m·K, respectively. ６ Sn ５ (Cu ３ Sn), Ni ３ Sn ４ The thermal conductivities of the third metal are 34 W / m·K and 20 W / m·K, respectively. The entire surface of the third metal is made of a metal containing Ni, and Ni has low reactivity with Sn, so Ni ３ Sn ４ In other words, the surface of the third metal is less likely to react with Sn in the base metal layer to form an intermetallic compound, making it possible to increase the thermal conductivity of the solder joint.

[0166] (Bonding material: fourth embodiment) A bonding material according to a fourth embodiment has a base metal layer and a coating layer that coats at least one surface of the base metal layer. Fig. 4 is an example of an SEM image showing a cross section in the thickness direction of the bonding material according to the fourth embodiment. In Fig. 4, a bonding material 1C has a base metal layer 2C and a coating layer 3C that coats both surfaces of the base metal layer 2C. The base metal layer 2C shown in Fig. 4 has a metal structure including a first phase 10 that 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% relative to the total mass of the base metal layer, the content of the metal forming the second phase is 10 mass% relative to the total mass of the base metal layer, and the content of the metal forming the third phase is 35 mass% relative to the total mass of the base metal layer. The content of Ni in the second phase is 90 mass% relative to the total mass of the second phase, and the content of Fe in the second phase is 10 mass% relative to 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 entire surface of the third phase 30 is made of a metal containing Ni. The bonding material according to the fourth embodiment is similar to the bonding material according to the second embodiment, except that the base metal layer has the third phase. The description of the metal containing Ni throughout the entire surface, its particle size, its content, etc. is the same as that of the <third metal> in the third embodiment.

[0170] The melting point of the metal forming the entire surface of the third phase as a whole is explained in the same manner as the melting point of the metal forming the entire surface of the third metal.

[0171] The metal constituting the first phase and its content are described in the same manner as in the <First metal> in the third embodiment. The metal constituting the second phase and its content are described in the same manner as in the <Second metal> in the third embodiment.

[0172] When the third phase has a uniform composition throughout, the overall composition of the metals constituting the third phase differs from the overall composition of the metals constituting the first phase and the overall composition of the alloy constituting the second phase. The explanation for the overall melting point of the metals constituting the third phase 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] When the third phase has a structure consisting of a core portion and a surface layer covering the core portion, the overall composition of the metal forming the surface layer of the third phase is different from the overall composition of the metal forming the first phase and the overall composition of the alloy forming 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 explanations for the diameter Rc of the core portion and the thickness Rs of the surface layer of the third phase are the same as those for the diameter Rc of the core portion and the thickness Rs of the surface layer 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 that in the second embodiment.

[0175] In the bonding material according to the fourth embodiment, the explanation of the thicknesses 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 is, for example, 1 to 5000 μm, 3 to 5000 μm, 5 to 5000 μm, 10 to 5000 μm, 15 to 5000 μm, 20 to 5000 μm, 25 to 5000 μm, 30 to 5000 μm, 40 to 5000 μm, 50 to 5000 μm, 75 to 5000 μm, 100 to 500 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 , 1 to 350 μm, 1 to 300 μm, 1 to 290 μm, 1 to 250 μm, 1 to 200 μm, 1 to 175 μm, 1 to 150 μm, 1 to 125 μm, 1 to 100 μm, 1 to 75 μm, 1 to 50 μm, 1 to 40 μm, 1 to 30 μm, 1 to 25 μm, 1 to 20 μm, or 1 to 15 μm. When the thickness of the base metal layer is equal to or greater than the above lower limit, the heat resistance of the soldered joint is more easily improved. When the thickness is equal to or less than the above upper limit, the generation of voids in the soldered joint that comes into contact with the object to be joined is more easily suppressed.

[0177] The thickness of the coating layer may be, for example, 1 to 150 μm, 3 to 150 μm, 5 to 150 μm, 7.5 to 150 μm, 10 to 150 μm, 12.5 to 150 μm, 15 to 150 μm, 20 to 150 μm, 25 to 150 μm, 30 to 150 μm, 40 to 150 μm, 50 to 150 μm, 75 to 150 μm, 1 to 125 μm, 1 to 100 μm, 1 to 75 μm, 1 to 50 μm, 1 to 40 μm, 1 to 30 μm, 1 to 25 μm, 1 to 20 μm, 1 to 15 μm, 1 to 12.5 μm, 1 to 10 μm, 1 to 7.5 μm, 1 to 5 μm, or 1 to 3 μm. When the thickness of the coating layer is equal to or greater than the lower limit, it is easier to suppress the generation of voids in the solder joint that contacts the object to be joined.When the thickness is equal to or less than the upper limit, it is easier to improve the heat resistance of the solder joint.

[0178] The thickness of the bonding material may be, for example, 2 to 5300 μm, 2 to 4000 μm, 2 to 3000 μm, 2 to 2000 μm, 2 to 1750 μm, 2 to 1510 μm, 2 to 1200 μm, 2 to 1000 μm, 2 to 750 μm, 2 to 500 μm, 2 to 400 μm, 2 to 300 μm, 2 to 250 μm, 2 to 200 μm, 2 to 150 μm, 2 to 100 μm, 2 to 75 μm, 2 to 50 μm, 2 to 40 μm, 2 to 30 μm, 5 to 5300 μm, 10 It may be up to 5300 μm, 15 to 5300 μm, 20 to 5300 μm, 30 to 5300 μm, 40 to 5300 μm, 50 to 5300 μm, 75 to 5300 μm, 100 to 5300 μm, 150 to 5300 μm, 200 to 5300 μm, 250 to 5300 μm, 300 to 5300 μm, 400 to 5300 μm, 500 to 5300 μm, 750 to 5300 μm, 1000 to 5300 μm, or 1200 to 5300 μm.

[0179] The ratio of the thickness of the base metal layer to the thickness of the coating layer, expressed as base metal layer / coating layer, may be, for example, 2 to 500, 3 to 500, 5 to 500, 7.5 to 500, 10 to 500, 15 to 500, 20 to 500, 30 to 500, 50 to 500, 100 to 500, 200 to 500, 2 to 400, 2 to 350, 2 to 300, 2 to 250, 2 to 200, 2 to 150, 2 to 100, 2 to 75, 2 to 60, 2 to 58, 2 to 50, 2 to 30, 2 to 20, 2 to 15, 2 to 10, 2 to 7.5, 2 to 5, or 2 to 3. When the ratio of base metal layer / coating layer is within the above range, it becomes easier to improve the heat resistance of the soldered joint and to further suppress the generation of voids in the soldered joint that comes into contact with the object to be joined. When the ratio is equal to or greater than the lower limit of the above range, it becomes easier to improve the heat resistance of the soldered joint. When the ratio is equal to or less than the upper limit of the above range, it becomes easier to suppress the generation of voids in the soldered 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). In the bonding material according to the fourth embodiment, the thickness of the coating layer is preferably 1 to 150 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 300, more preferably 5 to 150 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 200, even more preferably 5 to 150 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 2 to 100, and particularly preferably 5 to 75 μm, and the ratio of the thickness of the base metal layer to the thickness of the coating layer is 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, the heat resistance of the solder joint is more easily improved and the occurrence of voids in the solder joint is more easily suppressed.

[0181] In the bonding material according to the fourth embodiment, preferably, the thickness of the base metal layer is 1 to 5000 μm, the thickness of the coating layer is 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 a ratio expressed as base metal layer / coating layer, the metal constituting the third phase is made of only Ni, the content of the metal constituting the first phase is 30 to 90 mass % with respect 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 100% by mass with respect 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 content of the metal constituting the third phase is 3 to 30 mass% with respect to the total mass, the content of the metal constituting the first phase is 5 to 50 mass% with respect 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, expressed as a mass ratio of the content of the metal constituting the first phase / the content of the alloy constituting the second phase, is 4 to 30, the ratio of the content of the metal constituting the first phase to the content of the metal constituting the third phase, expressed as a mass ratio of the content of the metal constituting the first phase / the content of the metal constituting the third phase, is 1 to 5, and the ratio of the content of the alloy constituting the second phase to the content of the metal constituting the third phase, expressed as a mass ratio of the content of the metal constituting the third phase / the content of the alloy constituting the second phase, is 1 to 30.

[0182] In the bonding material according to the fourth embodiment, preferably, the thickness of the base metal layer is 1 to 500 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 a ratio expressed as base metal layer / coating layer, the metal constituting the third phase is made of only Ni, the content of the metal constituting the first phase is 30 to 90 mass % with respect 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 30 to 90 mass % with respect 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 content of the metal constituting the third phase is 3 to 30 mass% with respect 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, expressed as a mass ratio of the content of the metal constituting the first phase / the content of the alloy constituting the second phase, is 4 to 30 inclusive; the ratio of the content of the metal constituting the first phase to the content of the metal constituting the third phase, expressed as a mass ratio of the content of the metal constituting the first phase / the content of the alloy constituting the third phase, is 1 to 5 inclusive; and the ratio of the content of the alloy constituting the second phase to the content of the metal constituting the third phase, expressed as a mass ratio of the content of the metal constituting the third phase / the content of the alloy constituting the second phase, is 1 to 30 inclusive.

[0183] Like the bonding material of the third embodiment, the bonding material of the fourth embodiment can suppress the occurrence of voids in the solder joint and can further increase the thermal conductivity of the solder joint.

[0184] The bonding material according to the fourth embodiment can be manufactured by a manufacturing method similar to that of the bonding material according to the second embodiment, except that a third metal powder is further 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 above-mentioned <first metal>, <second metal>, and <third metal>, respectively.

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

[0187] (Bonding Material: Fifth Embodiment) In a bonding material according to a 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 FIG. 5 , the third metal 30B has an intermediate layer 303 between a core portion 301 and a surface layer 302 that covers the core portion 301. The intermediate layer 303 is adjacent to the core portion 301 and also adjacent to the surface layer 302. Ri denotes the thickness of the intermediate layer 303. The bonding material according to the fifth embodiment is similar to 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 surface of the core portion, or may cover the entire surface of the core portion, and preferably covers the entire surface of the core portion. In Fig. 5, intermediate layer 303 covers the entire surface of core portion 301. The proportion of the surface area of ​​the core portion covered by the intermediate layer relative to the total surface area of ​​the core portion (100%) is preferably 50% to 100% inclusive, more preferably 70% to 100% inclusive, even more preferably 90% to 100% inclusive, particularly preferably 95% to 100% inclusive, and most preferably 100%.

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

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

[0191] Examples of metals that may be contained 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. These metals may be contained alone or in combination of two or more. The metal group that may be contained in the intermediate layer can be arbitrarily selected from these metals.

[0192] The intermediate layer may contain unavoidable impurities in addition to the above-mentioned metals. Even if the intermediate layer contains unavoidable impurities, the effects of the present invention are not affected. The intermediate layer may be of one type or of 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 formed by plating, for example, known electroplating or electroless plating.

[0195] The core portion 301 and the surface layer 302 of the third metal 30B may be 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 can suppress the generation of voids in the solder joint and can further increase the thermal conductivity of the solder joint, similar to the bonding material according to the third embodiment. Since the third metal 30B has the intermediate layer 303, it becomes easier to provide the surface layer 302 of the third metal 30B.

[0197] (Other embodiments) In the bonding material according to other embodiments, only one surface of the base metal layer may be coated with a coating layer. The bonding material according to other embodiments may be a clad material in which one surface of the base metal layer and the coating layer are pressure-bonded. The bonding material in which only one surface of the base metal layer is coated with a coating layer can be manufactured by the pressure-bonding step A described above in the manufacturing method of the bonding material according to the second embodiment.

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

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

[0200] Examples of metals that may be included in the fourth 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 alone or in combination of two or more. The metal group that may be included in the fourth 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, and metal powders of two or more different compositions may be used.

[0202] Alternatively, a bonding material according to another embodiment is a bonding material having a base metal layer as described in the above embodiment and a coating layer covering at least one surface of the base metal layer, and is manufactured by, for example, a hot-dip method, a sputtering method, or the like. When using the hot-dip method, for example, the base metal layer is immersed in a molten metal that forms the coating layer and then cooled, thereby coating 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 metal that forms the coating layer is sputtered onto the base metal layer, thereby coating 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.

[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 method, a sputtering method, or the like.

[0204] In one embodiment, the present invention provides a solder joint formed using the bonding material according to the embodiment. The solder joint of this embodiment does not melt even when a power semiconductor operates at high temperatures, and can suppress the generation of voids in the solder joint.

[0205] (Method for manufacturing a solder joint) In one embodiment, the present invention provides a method for manufacturing a solder joint, in which a joint is formed between objects using a bonding material manufactured by the above-described (Method for manufacturing a bonding material). The objects to be joined using this manufacturing method are not particularly limited. For example, this manufacturing method can be used to bond a semiconductor element to a substrate. Examples of semiconductor elements 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 electrode on the substrate may be, for example, a Cu electrode, or a Cu electrode plated with Sn, Ni, Ni—Au, Ni—Pd, or Ni—Pd—Au. During bonding, flux may be applied in advance to one or both surfaces of the bonding material that will serve as the joining surfaces, the joining surface of the semiconductor element, or the joining surface of the substrate.

[0206] The temperature when joining the semiconductor element and the substrate is preferably, for example, 120°C or higher and 400°C or lower, or may be 200°C or higher and 400°C or lower, or may be 250°C or higher and 400°C or lower, and the method for manufacturing a solder joint of this embodiment is useful for joining under high temperature conditions (250°C or higher).

[0207] The atmosphere in which the objects are bonded may be air, an inert atmosphere such as a nitrogen atmosphere, or a reducing atmosphere. In the case of a nitrogen atmosphere, the pressure applied during bonding is preferably adjusted to 0.1 MPa or more and 10 MPa or less. Bonding the objects in this nitrogen atmosphere enhances the effect of suppressing the generation of voids. In the case of a reducing atmosphere, the objects can be bonded without pressure.

[0208] The bonding material of the above embodiment can be used to form a bonded portion between objects. The shear strength of the bonded portion 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 piece. Next, the test piece is mounted on an electroless Ni-plated Cu substrate with a thickness of 0.5 mm and a size 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 example, a laser microscope can be used to measure the surface roughness of the substrate. For example, a VK-X1000 (manufactured by Keyence) can be used as the laser microscope. Next, a Cu plate with a thickness of 0.5 mm and a size of 5 mm x 5 mm is mounted on the bonding material. Next, soldering is performed in a reflow furnace under pressure in a formic acid atmosphere with a peak temperature of 250°C and a cooling rate of 2°C / sec to produce a soldered joint. Next, the shear strength (N) of the solder joint at the joint is measured using a shear strength measuring device under conditions of 6.0 mm / min and 250° C. As the shear strength measuring device, for example, STR-1000 manufactured by Rhesca Co., Ltd. can be used.

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

[0211] <Production of Base Metal Sheet and Covering Sheet> Base metal sheets (A) to (G) were produced by the following procedure. Base metal sheets (A) to (G) are preformed solders obtained by rolling and molding the following first metal powder, second metal powder, third metal powder (1), and third metal powder (2) as raw materials.

[0212] The particle size of the metal powder was measured by volume using a laser diffraction / scattering particle size distribution analyzer (MT3300EXII) manufactured by Microtrac-Bell. The melting point of the metal powder was determined by differential scanning calorimetry (DSC). The first metal powder was measured using a DSC7020 manufactured by Hitachi High-Tech Science, and the second and third metal powders were measured using a DSC404-F3 Pegasus manufactured by NETZSCH. The thickness Rs of the surface layer of the third metal powder was measured using an Auger electron spectrometer.

[0213] First metal powder: Sn Metal powder of 100% Sn by mass (100% Sn powder) Particle size: 65 μm, Melting point: 232° C.

[0214] Second metal powder: Ni10Fe: Metal powder consisting 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] Third metal powder (1) Ni-plated Cu A 100% by mass Cu core ball was used as the core portion of the third metal powder (1). The particle size of the core portion (i.e., the core diameter Rc of the core portion) was 100 μm. The surface layer of the third metal powder (1) was plated with 100% by mass Ni. The plating thickness (i.e., the thickness Rs of the surface layer) was 2 μm. The plated core ball of the third metal powder (1) was a 100% by mass Cu core ball whose entire surface was coated with 100% by mass Ni plating. The 100% by mass Ni plating was formed by electroplating in all cases.

[0216] Third metal powder (2) Ni Metal powder of 100% by mass of Ni (100% by mass of Ni powder) Particle size 100 μm

[0217] Base metal sheet (A) Sn-40 (Ni10Fe) Mixing step: 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 step: Next, the prepared metal powder mixture was introduced into the hopper of a twin-roll rolling mill, the surface temperature of the rolling rolls was set to 100°C, and a rolling load of approximately 25 kN was applied to obtain a strip-shaped rolled material. Thereafter, the material was rolled to obtain a strip-shaped base metal sheet (A) of a predetermined thickness.

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

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

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

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

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

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

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

[0225] Sn, melting point 232°C Sn-3Ag-0.5Cu (Ag 3% by mass, Cu 0.5% by mass, balance Sn), melting point 220°C Sn-5Sb (Sb 5% by mass, balance Sn), melting point 243°C

[0226] Covering Sheet (X) Sn After processing Sn into a plate, 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 A covering sheet (Y) having a predetermined thickness was obtained in the same manner as in the manufacturing method of the covering sheet (X), except that a Sn-3Ag-0.5Cu alloy was used instead of Sn.

[0228] Covering Sheet (Z) Sn-5Sb A covering sheet (Z) having a predetermined thickness was obtained in the same manner as in the manufacturing method of the covering sheet (X), except that a Sn-5Sb alloy was used instead of Sn.

[0229] <Production of bonding materials> Each bonding material was produced using the base metal sheets (A) to (G) and the coating sheets (X) to (Z). In each bonding material produced, the thicknesses of the base metal layer and the coating layer were as shown in Tables 1 to 8, respectively.

[0230] (Example A1) A coating sheet (X) was rolled onto one side of a base metal sheet (A) to obtain a metal sheet. Next, the obtained one metal sheet was folded and rolled while the surfaces of the base metal layers were in contact with each other, to obtain a bonding material of Example A1 in which both sides 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) The bonding materials of Examples A2 to A6 and A8 to A11 were produced in the same manner as Example A1, except that the bonding materials were produced using the base metal sheet (A) and the coating sheets (X) to (Z) so that the base metal layer and the coating layer had predetermined thicknesses as shown in Table 1. In Example A7, the bonding material was produced in the same manner as Example A1, except that only one side of the base metal sheet (A) was covered 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 Example A1, except that the base metal sheet (A) was used, no covering sheet was used, and the base metal layer was molded to a predetermined thickness.

[0233] (Examples B1 to B3, C1 to C4, D1 to D4, E1 to E4, F1 to F4, G1 to G4) The bonding materials of each example were produced in the same manner as in Example A1, except that the bonding materials were produced using base metal sheets (B) to (G) and coating sheet (X) so that the base metal layer and coating layer had predetermined thicknesses, as shown in Tables 3 to 8. An SEM image showing a cross section in the thickness direction of the bonding material of Example C1 is shown in Figure 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 Example A1, except that the base metal sheets (B) to (G) were used and no covering sheet was used, and the base metal layer was molded to a predetermined thickness.

[0235] <Evaluation> Solder joints were produced using the prepared bonding materials as follows, and the void ratio in the bonded portion was measured.

[0236] <<Manufacturing of Solder Joints>> The bonding material of each example was cut to a size of 5 mm x 5 mm to obtain a test piece of each example. The test piece of each example was mounted on an electroless Ni-plated Cu substrate having a thickness of 0.5 mm and a size of 50 mm x 50 mm. The surface roughness of the substrate was Sa 0.31 μm and Sz 8.53 μm. The surface roughness was measured using a laser microscope VK-X1000 (manufactured by Keyence Corporation). A Cu plate having a thickness of 0.5 mm and a size of 5 mm x 5 mm was mounted on the bonding material and soldered. Then, soldering was performed in a reflow furnace under pressure in a formic acid atmosphere with a peak temperature of 250 °C and a cooling rate of 2 °C / sec to produce a solder joint.

[0237] <Evaluation of Void Suppression Ability> The void rate at the joint of each of the produced 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 joint site] (1) Measurement method The prepared solder joint was sealed with resin and polished to expose the joint cross section, and a cross-sectional SEM photograph was taken using an electron microscope (JEOL Ltd., JSM-7000F). In the cross-sectional SEM photograph, the void fraction (area %) was calculated for the entire area joined by the joining material, excluding the upper and lower members. For the calculation, image analysis software "Scandium" manufactured by Seika Digital Image Co., Ltd. was used, and the content of intermetallic compounds, Sn content, Bi content, and In content (each area %) at the joint site were calculated from the contrast. The total of the content of intermetallic compounds, Sn content, Bi content, In content, and voids at the joint site area % was set to 100 area %.

[0239] (2) Criteria for void ratio suppression ability A: The void ratio was less than 20%. B: The void ratio was 20% or more and less than 25%. C: The void ratio was 25% or more.

[0240] <Evaluation of Heat Resistance> For the soldered joints produced using the bonding materials of Example A1, Example A6, and Comparative Example A7, the shear strength of the soldered joints was measured as follows to evaluate the heat resistance. The measurement results are shown in Table 10.

[0241] [Measurement of Shear Strength] The shear strength (N) of the solder joints was measured at the joint site using a shear strength measuring device (STR-1000, manufactured by Rhesca Co., Ltd.) at 6.0 mm / min and 250° C. The higher the shear strength, the better the heat resistance of the solder joint.

[0242]

[0243]

[0244]

[0245]

[0246]

[0247]

[0248]

[0249]

[0250]

[0251]

[0252] The results shown in Tables 1 to 9 confirm that the Examples having a coating layer suppressed the generation of voids compared to the Comparative Examples not having a coating layer. The results shown in Tables 1 to 9 confirm that the Examples having a thickness ratio of base metal layer / coating layer of 2 to 58 had better void suppression ability. The results shown in Table 10 confirm that the Examples having a thickness ratio of base metal layer / coating layer of 2 or more had better heat resistance of the solder joint compared to the Comparative Example having a thickness ratio of 1.

Claims

1. A bonding material having 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 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, 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 represented by 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 as a ratio represented by 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 surfaces of the base metal layer are each covered with the coating layer.

5. In the base metal layer, the content of the second metal 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. In the coating layer, the content of the metal having a melting point lower than that of the second metal is 10% by mass or more and 100% by mass or less with respect to the total mass of the coating layer. In the coating layer, the content of the second metal is less than 15% by mass with respect to the total mass of the coating layer. The bonding material according to claim 1 or 2.

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 content of Ni in the metal containing Ni that forms 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 that forms the entire surface of the third metal. 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. The bonding material according to claim 6.

8. A bonding material having 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 including a first phase as a continuous phase and a second phase 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 coating layer has a metal structure including a metal phase having a melting point lower than that of the alloy containing 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 represented by base metal layer / coating layer.

9. The bonding material according to claim 8, which is a clad material in which at least one surface of the base metal layer and the coating layer are pressure-bonded.

10. A solder joint formed using the bonding material according to 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 covering at least one surface of the base metal layer, the method including a step of pressure-bonding a coating sheet to 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 composed of an alloy containing Ni and Fe, the coating sheet contains a metal having a melting point lower than that of 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 a ratio represented by 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, in which a bonding site is formed between objects using the bonding material manufactured by the method for manufacturing a bonding material according to claim 11 or 12.

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