Bonding materials and methods for making same, and solder joints and methods for making same

Abstract

Provided are a joining material capable of suppressing void generation in a solder joint, a method for producing the same, and a solder joint and a method for producing the same. A joining material 1A having a base metal layer 2A and a cover layer 3A covering at least one face (Sa1 or Sa2) of the base metal layer 2A. The base metal layer 2A contains a first metal containing Sn and a second metal composed of an alloy containing Ni and Fe, and the cover layer contains a metal having a lower melting point than the second metal. The ratio of the thickness of the base metal layer to the thickness of the cover layer is 2 or more in terms of the ratio of base metal layer / cover layer.

Description

Technical Field

[0001] This invention relates to bonding materials and methods for preparing the same, as well as solder joints and methods for preparing the same. This application claims priority based on Japanese Patent Application No. 2024-008258, filed on January 23, 2024, the contents of which are incorporated herein by reference. Background Technology

[0002] In recent years, with the increasing high operating environments of power semiconductor devices using silicon carbide (SiC) and other materials, the temperature at solder joints sometimes reaches around 250-280°C. Therefore, high-temperature solders that do not melt when operating under such high-temperature conditions are required.

[0003] In the fabrication of such high-temperature solder joints, pre-formed solder is used as the welding material. Pre-formed solder refers to solder that has been processed into various shapes such as square, strip, and disc.

[0004] As such a preformed solder, for example, a preformed solder is proposed which is formed by pressing a mixture of Sn metal powder and metal powder composed of an alloy of Ni and Fe into a preformed solder (see Patent Document 1).

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent No. 7014991 Summary of the Invention The problem to be solved by the present invention As described in Patent Document 1, preformed solder can suppress voids compared to TLP paste. However, when using the preformed solder described in Patent Document 1, there are exposed areas of metal powder composed of a Ni and Fe alloy on the bonding surface of the preformed solder in contact with the bonding object. Since the Ni and Fe alloy has a high melting point and almost no wetting effect, a new problem has been discovered where voids are easily generated at the solder joint.

[0006] The present invention was made in view of the above circumstances, and its object is to provide a bonding material capable of suppressing the generation of voids in solder joints and a method for preparing the same, as well as a solder joint and a method for preparing the same.

[0007] Problem-solving methods The present invention includes the following methods.

[0008] [1] A bonding material having a base metal layer and a cover layer covering at least one side of the base metal layer, wherein the base metal layer comprises: a first metal comprising Sn and a second metal comprising an alloy comprising Ni and Fe, the cover layer comprising 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 cover layer, expressed as a base metal layer / cover layer ratio, is 2 or more.

[0009] [2] According to the bonding material described in [1], the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is 2 to 300 in terms of the substrate metal layer / cover layer ratio.

[0010] [3] According to the bonding material described in [1] or [2], wherein the thickness of the covering layer is 1 to 150 μm.

[0011] [4] The bonding material according to any one of [1] to [3], wherein both sides of the substrate metal layer are covered by the covering layer.

[0012] [5] The bonding material according to any one of [1] to [4], wherein, in the substrate metal layer, the content of the second metal is more than 1% by mass and less than 70% by mass relative to the total mass of the first metal and the second metal, in the cover layer, the content of a metal with a melting point lower than the second metal is more than 10% by mass and less than 100% by mass relative to the total mass of the cover layer, and in the cover layer, the content of the second metal is less than 15% by mass relative to the total mass of the cover layer.

[0013] [6] The bonding material according to any one of [1] to [5], wherein the substrate metal layer further comprises a third metal, the surface of which is integrally formed of a metal comprising Ni.

[0014] [7] According to the bonding material of [6], 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 metal forming 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.

[0015] [8] A bonding material having a substrate metal layer and a cover layer covering at least one side of the substrate metal layer, wherein the substrate metal layer has a metallic structure having a first phase as a continuous phase and a second phase dispersed in the first phase, the first phase being composed of a metal containing Sn, the second phase being composed of an alloy containing Ni and Fe, the cover layer having a metallic structure having a metallic phase being composed of a metal with a melting point lower than that of the alloy containing Ni and Fe, and the ratio of the thickness of the substrate metal layer to the thickness of the cover layer being 2 or more in terms of substrate metal layer / cover layer ratio.

[0016] [9] According to the bonding material of [8], wherein the bonding material is a covering material formed by pressing at least one side of the substrate metal layer with the cover layer.

[0017]

[10] A solder joint formed using any one of the bonding materials described in [1] to [9].

[0018]

[11] A method for preparing a bonding material, which is a method for preparing a bonding material having a substrate metal layer and a cover layer covering at least one side of the substrate metal layer, wherein the method includes the steps of pressing a cover sheet onto at least one side of a substrate metal sheet and covering the side with the cover layer, the substrate metal sheet comprising: a first metal comprising Sn and a second metal comprising an alloy comprising Ni and Fe, the cover sheet comprising a metal with a melting point lower than the second metal, and the ratio of the thickness of the substrate metal layer to the thickness of the cover layer being 2 or more in terms of substrate metal layer / cover layer ratio.

[0019]

[12] According to the method for preparing the bonding material described in

[11] , the substrate metal layer further comprises a third metal, the surface of which is entirely formed of a metal containing Ni.

[0020]

[13] A method for preparing a solder joint, wherein a bonding material prepared by the bonding material preparation method described in

[11] or

[12] is used to form a bonding portion between objects.

[0021] Effects of the present invention According to the present invention, a bonding material capable of suppressing voids in solder joints and a method for preparing the same, as well as a solder joint and a method for preparing the same, can be provided. Attached Figure Description

[0022] Figure 1A This is a perspective view of the bonding material 1A according to the first embodiment.

[0023] Figure 1B This is a schematic diagram showing a cross-section of the bonding material 1A in the thickness direction according to the first embodiment.

[0024] Figure 2A This is an SEM image showing a cross-section of the bonding material 1B in the thickness direction according to the second embodiment.

[0025] Figure 2B This is a schematic diagram showing a cross-section in the thickness direction of the bonding material 1D obtained by the pressing process A in one embodiment of the bonding material preparation method.

[0026] Figure 2C This is a schematic diagram illustrating the pressing process B1 in one embodiment of the method for preparing the bonding material.

[0027] Figure 2D This is a schematic diagram illustrating the pressing step B2 in one embodiment of the method for preparing the bonding material.

[0028] Figure 2E This is a schematic diagram illustrating the pressing step B3 in one embodiment of the method for preparing the bonding material.

[0029] Figure 3 This is a schematic diagram showing a cross-section of the third metal 30A in the bonding material of the third embodiment.

[0030] Figure 4 This is an SEM image showing a cross-section of the bonding material 1C in the thickness direction according to the fourth embodiment.

[0031] Figure 5 This is a schematic diagram showing a cross-section of the third metal 30B in the bonding material of the fifth embodiment. Detailed Implementation

[0032] As used herein, the terms “comprise” and “containing” are concepts that include any one of “comprise”, “consist essentially of”, and “consist of”.

[0033] In this specification, "first metal", "second metal", "third metal" and "fourth metal" refer to "particles formed by the first metal", "particles formed by the second metal", "particles formed by the third metal" and "particles formed by the fourth metal", respectively.

[0034] In this specification, "first metal powder", "second metal powder", "third metal powder" and "fourth metal powder" sometimes refer to "a particle group formed by the first metal", "a particle group formed by the second metal", "a particle group formed by the third metal" and "a particle group formed by the fourth metal", respectively.

[0035] (Bonding material: First embodiment) like Figure 1A As illustrated, the bonding material 1A in the first embodiment is square.

[0036] Figure 1B This is a schematic diagram showing a cross-section of the bonding material 1A according to the first embodiment. Figure 1B As illustrated, the bonding material 1A has a substrate metal layer 2A and a cover layer 3A that respectively covers two sides (i.e., Sa1 and Sa2) of the substrate metal layer 2A.

[0037] Figure 1B In this context, Ta2 represents the thickness of the substrate metal layer 2A, and Ta3 represents the thickness of the cover layer 3A.

[0038] The substrate metal layer comprises: a first metal containing Sn and a second metal composed of an alloy containing Ni and Fe.

[0039] The coating layer contains a metal with a lower melting point than the second metal.

[0040] The composition of the substrate metal layer is different from that of the cover layer.

[0041] [Substrate Metal Layer] The substrate metal layer comprises: a first metal containing Sn and a second metal composed of an alloy containing Ni and Fe.

[0042] First Metal The first metal contains Sn.

[0043] Because of Sn's excellent ductility, the voids between the first metals can be eliminated through plastic deformation. Furthermore, the first metal containing Sn can ensure general properties such as wettability when used as a welding material.

[0044] The first metal can also include metals other than Sn.

[0045] The first metal group can include metals other than Sn, such as Ag, Cu, In, Bi, Ni, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, and As. One or more of these metals other than Sn can be included. The group of metals other than Sn can be arbitrarily chosen from these metals.

[0046] The first metal can be either an elemental form of Sn or a metal other than Sn, or an alloy of Sn and an elemental form of a metal other than Sn.

[0047] The first metal can be, for example, Sn monomer, or a metal mixed with Sn but other than Sn, or a metal alloyed with Sn but other than Sn, or a metal mixed with an alloy containing Sn and other metals.

[0048] In addition to the metals mentioned above, the first metal may also contain unavoidable impurities. Even in the presence of unavoidable impurities, the effectiveness of the invention will not be affected.

[0049] The first metal can be one type or two or more types.

[0050] The melting point of the first metal is preferably below 300°C, but can be below 250°C or 116~200°C.

[0051] If the melting point of the first metal is below the upper limit of the above preferred range, the wettability of the solder can be easily ensured.

[0052] The "melting point of the metal to be measured or the melting point of the metal powder to be measured" mentioned in this specification refers to the melting point determined by differential scanning calorimetry (DSC). The melting point of the metal to be measured is the temperature at which the maximum heat absorption per unit time is achieved, based on the DSC measurement results. If the metal to be measured has a single peak in the DSC measurement, the melting point refers to the temperature at the top of that peak. If the metal to be measured has multiple peaks in the DSC measurement, the melting point refers to the temperature at the peak with the highest heat absorption per unit time among the multiple peaks.

[0053] The same applies to the melting point of the metal powder being measured.

[0054] The melting points of the first and fourth metals can be determined, for example, using a DSC7020 prepared by Hitachi High Technology Scientific. The melting points of the second and third metals, described later, can be determined, for example, using a DSC404-F3Pegasus prepared by NETZSCH.

[0055] The Sn content in the first metal is preferably 20% by mass or more and 100% by mass or less relative to the total mass of the first metal. In order to fully utilize the properties of Sn, the Sn content in the first metal is preferably 90% by mass or more relative to the total mass of the first metal, more preferably 95% by mass or more, and even more preferably 100% by mass.

[0056] <The Second Metal> The second metal is composed of an alloy containing Ni and Fe.

[0057] The alloy in the second metal preferably contains Ni and Fe, has a higher melting point than the first metal, and is dispersed within the substrate metal layer.

[0058] The melting point of the alloy in the second metal is preferably above 300°C, more preferably above 500°C, and even more preferably 600~1600°C.

[0059] If the melting point of the alloy in the second metal exceeds the lower limit of the above-mentioned preferred range, the shear strength of the solder joint can be easily improved even in high-temperature working environments.

[0060] The alloy of the second metal may also contain metals other than Ni and Fe. That is, the second metal may be an alloy of Ni and Fe, or an alloy of Ni, Fe and other metals, with an alloy of Ni and Fe being preferred.

[0061] The second metal can include metals other than Ni and Fe, such as Sn, Ag, Cu, In, Bi, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Mn, Zr, and As. One or more of these metals other than Ni and Fe can be included. The group of metals other than Ni and Fe can be arbitrarily chosen from these metals.

[0062] In addition to the metals mentioned above, the second metal may also contain unavoidable impurities. Even in the presence of unavoidable impurities, the effectiveness of the invention will not be affected.

[0063] The second metal can be one type or two or more types.

[0064] The Ni content in the second metal is preferably 80% by mass or more and 99% by mass or less relative to the total mass of the second metal, and more preferably 85% by mass or more and 95% by mass or less.

[0065] The Fe content in the second metal is preferably 1% by mass or more and 20% by mass or less relative to the total mass of the second metal, more preferably 5% by mass or more and 15% by mass or less.

[0066] If the Ni and Fe contents in the second metal are within the preferred range described above, intermetallic compounds can be formed at an earlier stage, suppressing the occurrence of voids.

[0067] The term "particle size of metal or particle size of metal powder" as used in this specification refers to the average particle size measured using a laser diffraction / scattering particle size distribution measuring device based on volume.

[0068] The average particle size can be determined, for example, using a laser diffraction / scattering particle size distribution measuring device (MT3300EXII) manufactured by Microtrac BEL.

[0069] The particle size of the second metal is preferably 0.1~1000μm, more preferably 1~100μm, and even more preferably 5~50μm.

[0070] If the particle size of the second metal is above the lower limit of the above-mentioned preferred range, wettability is easily ensured; if it is below the upper limit of the above-mentioned preferred range, intermetallic compounds are more easily formed.

[0071] <Relationship between the contents of the first and second metals> In the substrate metal layer of the bonding material in the first embodiment, the content of the first metal is preferably 30%, 60%, 80%, 90%, or 97% by mass relative to the total mass (100% by mass) of the first metal and the second metal, and the upper and lower limits can be appropriately selected from these values.

[0072] The content of the first metal relative to the total mass (100% by mass) of the first metal and the second metal can be 30-99% by mass or 30-97% by mass.

[0073] In the substrate metal layer of the bonding material in the first embodiment, the content of the second metal is preferably 3%, 10%, 20%, 40%, or 70% by mass relative to the total mass (100% by mass) of the first metal and the second metal, and the upper and lower limits can be appropriately selected from these values.

[0074] The content of the second metal relative to the total mass (100% by mass) of the first and second metals can be 1 to 70% by mass or 3 to 70% by mass.

[0075] By keeping the content of the second metal within the above-mentioned preferred range, the heat resistance of the solder joint is further improved.

[0076] In the substrate metal layer of the bonding material in the first embodiment, the total content of the first metal and the content of the second metal do not exceed 100% by mass.

[0077] In the substrate metal layer of the bonding material of the first 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 to the content of the second metal, is preferably 0.43 or 32, and the upper and lower limits can be appropriately selected from these values. The mass ratio of the content of the first metal to the content of the second metal can be 0.1 or more and 100 or less, or 0.4 or more and 35 or less.

[0078] By ensuring that the mass ratio of the first metal content to the second metal content is within the preferred range described above, it is easier to suppress voids in the solder joint, and the heat resistance of the solder joint is further improved.

[0079] In the substrate metal layer of the bonding material in the first embodiment, the total content of the first metal and the second metal relative to the total mass of the substrate metal layer is preferably 60% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, even more preferably 90% by mass or more and 100% by mass or less, and may also be 100% by mass.

[0080] The thickness of the substrate metal layer is preferably 150μm, 250μm, 290μm, 298μm, 299μm, or 1500μm, and the upper and lower limits can be appropriately selected from these values.

[0081] The thickness of the substrate metal layer can be, for example, 5~5000μm, 150~1500μm, or 150~290μm.

[0082] By making the thickness of the substrate metal layer above or above the aforementioned lower limit, it is easier to improve the heat resistance of the solder joint. By making it below or above the aforementioned upper limit, it is easier to suppress the generation of voids in the solder joint that is in contact with the object being joined.

[0083] The thickness of the substrate metal layer can be, for example, 1~5000μm, 3~5000μm, 5~5000μm, 10~5000μm, 15~5000μm, 20~5000μm, 25~5000μm, 30~5000μm, 40~5000μm, 50~5000μm, 75~5000μm, 100~5 000μm, 125~5000μm, 150~5000μm, 175~5000μm, 200~5000μm, 250~5000μm, 29 0~5000μm, 300~5000μm, 350~5000μm, 400~5000μm, 500~5000μm, 750~5000μm, 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~ 400μm, 1~350μm, 1~300μm, 1~290μm, 1~250μm, 1~200μm, 1~175μm, 1~150μm, 1 ~125μm, 1~100μm, 1~75μm, 1~50μm, 1~40μm, 1~30μm, 1~25μm, 1~20μm, 1~15μm.

[0084] By making the thickness of the substrate metal layer above or above the aforementioned lower limit, it is easier to improve the heat resistance of the solder joint. By making it below or above the aforementioned upper limit, it is easier to suppress the generation of voids in the solder joint that is in contact with the object being joined.

[0085] [Overlay] The capping layer contains a metal with a lower melting point than the Ni and Fe alloy that forms the second metal. The metal forming the capping layer forms a compound with the metal constituting the bonded object.

[0086] The melting point of the metal with a lower melting point than the second metal is preferably below 300°C, but can be below 250°C or between 78°C and 200°C.

[0087] Examples of metals with a melting point lower than the second metal include metals containing Sn and metals containing In. The capping layer may also contain metals other than Sn and In. The metals contained in the capping layer may be elemental metals other than Sn and In, or may be alloys of Sn, In, and elemental metals other than Sn or In.

[0088] The coating layer can be Sn monomer, a substance composed of Sn and a metal other than Sn, an alloy of Sn and a metal other than Sn, or a substance composed of an alloy containing Sn and a metal other than Sn.

[0089] In addition, the coating can be elemental In, a mixture of In and a metal other than In, an alloy of In and a metal other than In, or a mixture of an alloy containing In and a metal other than In.

[0090] When the capping layer contains Sn, other metals that can be included include, for example, Ag, Cu, In, Bi, Ni, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, and As. One or more metals other than Sn can be included. The group of metals other than Sn can be arbitrarily selected from these metals.

[0091] Furthermore, when the capping layer contains In, other metals that can be included besides In include, for example, Sn, Ag, Cu, Bi, Ni, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, and As. One or more metals other than In can be included. The group of metals other than In can be arbitrarily selected from these metals.

[0092] In addition to the aforementioned metals, the coating layer may also contain unavoidable impurities. Even in the presence of unavoidable impurities, the effectiveness of the invention will not be affected.

[0093] When the capping layer contains Sn, the Sn content in the capping layer is preferably 10% by mass or more and 100% by mass or less relative to the total mass of the capping layer. In order to fully utilize the characteristics of Sn, the Sn content in the solder is preferably 40% by mass or more, more preferably 60% by mass or more, particularly preferably 80% by mass or more, most preferably 90% by mass or more, and can be 95% by mass or more, or 100% by mass.

[0094] When the capping layer contains In, the In content in the capping layer is preferably 10% by mass or more and 100% by mass or less relative to the total mass of the capping layer. In order to fully utilize the characteristics of In, the In content in the solder is preferably 20% by mass or more, more preferably 40% by mass or more, particularly preferably 60% by mass or more, most preferably 80% by mass or more, and may also be 100% by mass.

[0095] The cover layer may or may not include the second metal described in the [substrate metal layer], preferably not.

[0096] When the capping layer contains a second metal, the content of the second metal in the capping layer is preferably less than 15% by mass relative to the total mass of the capping layer, more preferably less than 10% by mass, even more preferably less than 1% by mass, and particularly preferably less than 0.1% by mass.

[0097] The thickness of the capping 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, the thickness of the capping layer can be 1~150 μm, 3~100 μm, 1~75 μm, or 5~75 μm.

[0098] By making the thickness of the cover layer above or above the aforementioned lower limit, it is easier to suppress the formation of voids in the solder joint that contacts the object being joined. By making it below or below the aforementioned upper limit, it is easier to improve the heat resistance of the solder joint.

[0099] The thickness of the capping layer can be, for example, 1~150μm, 3~150μm, 5~150μm, 7.5~150μm, 10~150μm, 12.5~150μm, 15~150μm, 20~150μm, 25~150μm, 30~150μm, 40~150μm, 50~150μm, 75~150μm, 1~125μm, 1~100μm, 1~75μm, 1~50μm, 1~40μm, 1~30μm, 1~25μm, 1~20μm, 1~15μm, 1~12.5μm, 1~10μm, 1~7.5μm, 1~5μm, or 1~3μm.

[0100] By making the thickness of the cover layer above or above the aforementioned lower limit, it is easier to suppress the formation of voids in the solder joint that contacts the object being joined. By making it below or below the aforementioned upper limit, it is easier to improve the heat resistance of the solder joint.

[0101] In this specification, "thickness of the cover layer" refers to the thickness of the cover layer covering one side of the substrate metal layer. That is, even if both surfaces of the substrate metal layer are covered with a cover layer, "thickness of the cover layer" refers to the thickness of the cover layer covering one side of the substrate metal layer.

[0102] The number of layers of the cover layer covering one side of the substrate metal layer can be 1 or 2.

[0103] When there are two or more cover layers covering one side of the substrate metal layer, the thickness of the cover layer covering one side refers to the total thickness of all cover layers covering one side.

[0104] When both sides of the substrate metal layer are covered by a cover layer, the number of cover layers and the composition of the cover layer on one side can be different from those on the other side.

[0105] 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. For example, the thickness of the bonding material can be 10~5300 μm or 20~1510 μm.

[0106] The thickness of the bonding material can be, for example, 2~5300μm, 2~4000μm, 2~3000μm, 2~2000μm, 2~1750μm, 2~1510μm, 2~1200μm, 2~1000μm, 2~750μm, 2~500μm, 2~400μm, 2~300μm, 2~250μm, 2~200μm, 2~150μm, 2~100μm, 2~75μm, 2~50μm, 2~40μm, 2~30μm, 5~5300μm. m, 10~5300μm, 15~5300μm, 20~5300μm, 30~5300μm, 40~5300μm, 50~5300μm, 75~5300μm, 100~5300μm, 150~5300μm m, 200~5300μm, 250~5300μm, 300~5300μm, 400~5300μm, 500~5300μm, 750~5300μm, 1000~5300μm, 1200~5300μm.

[0107] In this specification, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is expressed as a ratio of substrate metal layer (μm) / cover layer (μm).

[0108] The ratio of the thickness of the substrate metal layer to the thickness of the cover layer, expressed as a substrate metal layer / cover layer ratio, is preferably 2, 10, 58, 298, 299, or 300, and the upper and lower limits can be appropriately selected from these values. The substrate metal layer / cover layer ratio can, for example, be 1 to 500, 2 to 300, 2 to 100, or 2 to 58.

[0109] By making the ratio of the base metal layer to the cover layer within the above range, it is easier to improve the heat resistance of the solder joint, and thus easier to suppress the generation of voids in the solder joint that is in contact with the object being joined.

[0110] The ratio of the thickness of the substrate metal layer to the thickness of the cover layer is expressed as the substrate metal layer / cover layer ratio, for example, it can be 2~500, 3~500, 5~500, 7.5~500, 10~500, 15~500, 20~500, 30~500, 50~500, 100~500, 200~500, 2~400, 2~350, 2~300, 2~250, 2~200, 2~150, 2~100, 2~75, 2~60, 2~58, 2~50, 2~30, 2~20, 2~15, 2~10, 2~7.5, 2~5, 2~3.

[0111] By ensuring the ratio of the base metal layer to the cover layer is within the aforementioned range, it is easier to improve the heat resistance of the solder joint, and consequently, easier to suppress the formation of voids in the solder joint that comes into contact with the object being joined. By setting the ratio above the lower limit of the aforementioned range, it is easier to improve the heat resistance of the solder joint. By setting the ratio below the upper limit of the aforementioned range, it is easier to suppress the formation of voids in the solder joint.

[0112] Regarding the bonding material of the first embodiment, the above-mentioned specifications regarding the thickness of the substrate metal layer and the cover layer, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer, and the content of the first metal and the second metal can be combined arbitrarily.

[0113] Hereinafter, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer refers to the ratio expressed as substrate metal layer (μm) / cover layer (μm).

[0114] In the first embodiment, the bonding material preferably has a cover layer thickness of 1 to 150 μm and a substrate metal layer thickness to cover layer thickness ratio of 2 to 300. More preferably, the cover layer thickness is 5 to 150 μm and the substrate metal layer thickness to cover layer thickness ratio is 2 to 200. Even more preferably, the cover layer thickness is 5 to 150 μm and the substrate metal layer thickness to cover layer thickness ratio is 2 to 100. Particularly preferably, the cover layer thickness is 5 to 75 μm and the substrate metal layer thickness to cover layer thickness ratio is 2 to 60.

[0115] If the thickness of the cover layer is within the above range, and the ratio of the thickness of the base metal layer to the thickness of the cover layer is within the above range, it is easier to improve the heat resistance of the solder joint and easier to suppress the generation of voids in the solder joint.

[0116] For the bonding material of the first embodiment, the thickness of the base metal layer is preferably 150 to 1500 μm, the thickness of the cover layer is preferably 1 to 150 μm, the ratio of the thickness of the base metal layer to the thickness of the cover layer is preferably 2 to 500 as expressed as base metal layer / cover layer, the content of the first metal is 30 to 97% by mass relative to the total mass (100% by mass) of the first metal and the second metal, the content of the second metal is 3 to 70% by mass relative to the total mass (100% by 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 is preferably 0.4 or more and 35 or less as expressed as the mass ratio of the content of the first metal / the content of the second metal.

[0117] For the bonding material of the first embodiment, the thickness of the substrate metal layer is preferably 150-290 μm, the thickness of the cover layer is preferably 5-100 μm, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is preferably 2-58 (substrate metal layer / cover layer), the content of the first metal is 30-97% by mass relative to the total mass (100% by mass) of the first metal and the second metal, the content of the second metal is 3-70% by mass relative to the total mass (100% by 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 is preferably 0.4 or more and 35 or less (first metal content / second metal content by mass ratio).

[0118] For the bonding material of the first embodiment, the thickness of the base metal layer is preferably 1 to 5000 μm, the thickness of the cover layer is preferably 1 to 150 μm, the ratio of the thickness of the base metal layer to the thickness of the cover layer is preferably 2 to 500 (based on the ratio of base metal layer to cover layer), the content of the first metal is 30 to 97% by mass relative to the total mass (100% by mass) of the first metal and the second metal, the content of the second metal is 3 to 70% by mass relative to the total mass (100% by 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 is preferably 0.4 or more and 35 or less (based on the mass ratio of the content of the first metal to the content of the second metal).

[0119] For the bonding material of the first embodiment, the thickness of the base metal layer is preferably 1 to 2000 μm, the thickness of the cover layer is preferably 1 to 100 μm, the ratio of the thickness of the base metal layer to the thickness of the cover layer is preferably 2 to 500 as expressed as base metal layer / cover layer, the content of the first metal is 30 to 97% by mass relative to the total mass (100% by mass) of the first metal and the second metal, the content of the second metal is 3 to 70% by mass relative to the total mass (100% by 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 is preferably 0.4 or more and 35 or less as expressed as the mass ratio of the content of the first metal / the content of the second metal.

[0120] In the preparation of the bonding material in the first embodiment, known preparation methods can be used, such as hot-dip galvanizing or calendering.

[0121] ■Explanation of Effects■ The bonding material of the first embodiment described above has a base metal layer and a cover layer covering at least one side of the base metal layer. By having a cover layer, the bonding material can suppress the formation of voids at the solder joint. The reason for this effect is as follows.

[0122] On the surface of a substrate metal layer containing metal powder composed of an alloy of Ni and Fe, there are exposed areas of the Ni and Fe alloy metal powder. The Ni and Fe alloy has a high melting point and extremely low wetting ability, thus easily creating voids at the solder joint.

[0123] Since the cover layer covers the substrate metal layer so that the Ni and Fe alloy is not exposed on the surface of the substrate metal layer, the generation of voids in the joint can be suppressed when the bonding material of the first embodiment is used to bond the bonding objects.

[0124] (Bonding material: Second embodiment) Figure 2A This is an SEM image of a cross-section in the thickness direction illustrating an example of the bonding material of the second embodiment. Figure 2A In the process, the bonding material 1B has a substrate metal layer 2B and a cover layer 3B that covers two sides of the substrate metal layer 2B respectively.

[0125] Figure 2A The substrate metal layer 2B shown has a metallic structure comprising a first phase 10 as a continuous phase and a second phase 20 dispersed in the first phase.

[0126] Figure 2A The cover layer 3B shown has a metallic structure consisting of a metallic phase composed of a metal with a melting point lower than that of the alloy containing Ni and Fe.

[0127] The composition of the substrate metal layer 2B is different from that of the cover layer 3B.

[0128] Figure 2A The illustrated bonding material 1B is the bonding material of Example C1 described later in this embodiment. The thickness of the substrate metal layer of bonding material 1B is 150 μm, and the thickness of the capping layer is 75 μm. In the substrate metal layer 2B, the content of the first phase is 80% by mass relative to the total mass of the substrate metal layer, and the content of the second phase is 20% by mass relative to the total mass of the substrate metal layer. The content of Ni in the second phase is 90% by mass relative to the total mass of the second phase, and the content of Fe in the second phase is 10% by mass relative to the total mass of the second phase.

[0129] Figure 2A The illustrated bonding material 1B is a covering material with a covering layer bonded to both sides of the substrate metal layer.

[0130] In the coating material, an intermetallic compound may be formed at the junction of the substrate metal layer and the cover layer. As described later, the bonding material of the second embodiment can be manufactured, for example, by pressing a substrate metal sheet, which serves as the substrate metal layer, and a cover sheet, which serves as the cover layer, together.

[0131] As described below, the substrate metal sheet can be prepared, for example, by a method such as rolling forming, using metal powder containing a first metal containing Sn and a second metal composed of an alloy containing Ni and Fe as raw materials.

[0132] The base metal sheet can also be a pre-formed solder.

[0133] [Substrate Metal Layer] In the substrate metal layer 2B, the first phase 10 is a continuous phase composed of a metal containing Sn. The description of the Sn-containing metal and its content is the same as that of the <first metal> in the above embodiment.

[0134] In addition, in the first phase 10, grain boundaries may exist between metal crystals containing Sn.

[0135] The melting point of the metals constituting the first phase can be determined in the same manner as the melting point of the first metal. When the first phase contains multiple metals, the melting point of the metals constituting the first phase is taken as the peak temperature of the metal with the highest heat absorption per unit time among the multiple peaks that the multiple metals constituting the first phase can have.

[0136] The melting point of the metal constituting the second phase is also defined in the same way.

[0137] The melting point of the metal that forms the surface integral of the third phase is also defined in the same way.

[0138] When the third phase is a homogeneous composition, the melting point of the metal constituting the third phase is also defined in the same way.

[0139] In the case where the third phase has a structure consisting of a core and a surface layer covering the core, the overall melting point of the metal forming the surface layer of the third phase is defined in the same way, and the overall melting point of the metal forming the core of the third phase is also defined in the same way.

[0140] The description of the melting point of the metal constituting the first phase as a whole is the same as the description of the melting point of the first metal.

[0141] In the substrate metal layer 2B, the second phase 20 is dispersed in the first phase 10.

[0142] The second phase 20 is composed of an alloy containing Ni and Fe. The description of the alloy containing Ni and Fe, its particle size, and its content is the same as that of the <second metal> in the first embodiment.

[0143] The description of the melting point of the alloy constituting the second phase as a whole is the same as the description of the melting point of the second metal.

[0144] In this specification, the grain size of a phase can be determined and calculated from the cross-sectional microstructure containing that phase using optical microscopy, SEM, transmission electron microscopy (TEM), etc. The grain size of a phase can be calculated by measuring the diameters of three or more phases and using their average value.

[0145] The particle size of the second phase can be the particle size of the second metal powder prepared to form the second phase.

[0146] In this specification, "content of metals constituting the phase" means "the total content of metals constituting the phase".

[0147] In the substrate metal layer, from the viewpoint of balancing bonding and shear strength, the mixing ratio of the Sn-containing metal constituting the first phase to the Ni and Fe-containing alloy constituting the second phase is such that, relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase, the content of the alloy constituting the first phase is preferably 30%, 60%, 80%, 90%, or 97% by mass, and the upper and lower limits can be appropriately selected from these values.

[0148] The content of the second metal can be 30-99% by mass or 30-97% by mass.

[0149] In the substrate metal layer, relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase, the content of the alloy constituting the second phase is preferably 3% by mass, 10% by mass, 20% by mass, 40% by mass and 70% by mass, and the upper and lower limits can be appropriately selected from these values.

[0150] The content of the alloy constituting the second phase can be 1 to 70% by mass or 3 to 70% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase.

[0151] When the content of the alloy constituting the second phase is within the above-mentioned preferred range, the heat resistance of the solder joint is further improved.

[0152] In the substrate metal layer of the bonding material in the second embodiment, the total content of the Sn-containing metal constituting the first phase and the content of the alloy constituting the second phase does not exceed 100% by mass.

[0153] In the substrate metal layer of the bonding material in the second embodiment, 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 preferably 0.43 or 32 in terms of the mass ratio of the first phase to the second phase, and the upper and lower limits can be appropriately selected from these values. The mass ratio of the first phase to the second phase is preferably 0.1 or more and 100 or less, more preferably 0.4 or more and 35 or less.

[0154] When the mass ratio of the first phase to the second phase is within the preferred range described above, it is easier to suppress voids in the solder joint and further improve the heat resistance of the solder joint.

[0155] In the substrate metal layer of the bonding material in the second embodiment, the total content of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase is preferably 60% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, even more preferably 90% by mass or more and 100% by mass or less, and may also be 100% by mass.

[0156] In the bonding material of the second embodiment, the description of the thickness of the substrate metal layer and the cover layer is the same as that of the first embodiment.

[0157] The thickness of the substrate metal layer of the bonding material in the second embodiment is preferably 150μm, 250μm, 290μm, 298μm, 299μm, or 1500μm, and the upper and lower limits can be appropriately selected from these values.

[0158] The thickness of the substrate metal layer can be, for example, 5~5000μm, 150~1500μm, or 150~290μm.

[0159] By making the thickness of the substrate metal layer above or above the aforementioned lower limit, it is easier to improve the heat resistance of the solder joint. By making it below or above the aforementioned upper limit, it is easier to suppress the generation of voids in the solder joint that is in contact with the object being joined.

[0160] The thickness of the substrate metal layer of the bonding material in the second embodiment can be, for example, 1~5000μm, 3~5000μm, 5~5000μm, 10~5000μm, 15~5000μm, 20~5000μm, 25~5000μm, 30~5000μm, 40~5000μm, 50~5000μm, 75~5000μm, 100~5000μm, 125~5000μm, 150~5000μm, 175~5000μm, 200~5000μm, 250~5000μm, 290~5000μm, 300~5000μm, 350~5000μm, 400~5000μm, 500~5000μm, 75 ... 000μm, 1000~5000μm, 1200~5000μm, 1500~5000μm, 1~4000μm, 1~3500μm, 1~30 00μm, 1~2500μm, 1~2000μm, 1~1500μm, 1~1200μm, 1~1000μm, 1~750μm, 1~500μm , 1~400μm, 1~350μm, 1~300μm, 1~290μm, 1~250μm, 1~200μm, 1~175μm, 1~150μm, 1~125μm, 1~100μm, 1~75μm, 1~50μm, 1~40μm, 1~30μm, 1~25μm, 1~20μm, 1~15μm.

[0161] By making the thickness of the substrate metal layer above or above the aforementioned lower limit, it is easier to improve the heat resistance of the solder joint. By making it below or above the aforementioned upper limit, it is easier to suppress the generation of voids in the solder joint that is in contact with the object being joined.

[0162] [Overlay] The capping layer 3B has a metallic structure comprising a metallic phase of a metal phase having a melting point lower than that of the alloy containing Ni and Fe. The description of the metal having a melting point lower than that of the alloy containing Ni and Fe, its content, etc., is the same as that of the metal having a melting point lower than that of the alloy containing Ni and Fe in the first embodiment.

[0163] The metal and its content in the capping layer of the bonding material forming the second embodiment are the same as the metal and its content in the capping layer of the bonding material forming the first embodiment.

[0164] In the bonding material of the second embodiment, the description of the number of layers and the thickness of the cover layer is the same as that of the first embodiment.

[0165] The capping layer may or may not have the second phase described in the [substrate metal layer], but is preferably not to have it.

[0166] When the capping layer has a second phase, the content of the alloy comprising Ni and Fe constituting the second phase in the capping layer is preferably less than 15% by mass, more preferably less than 10% by mass, even more preferably less than 1% by mass, and particularly preferably less than 0.1% by mass, relative to the total mass of the capping layer.

[0167] The thickness of the capping 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 can be 1~150 μm, 3~100 μm, 1~75 μm, or 5~75 μm. By making the thickness of the capping layer above the lower limit mentioned above, it is easier to suppress the generation of voids in the solder joint in contact with the object being joined. By making it below the upper limit mentioned above, it is easier to improve the heat resistance of the solder joint.

[0168] The thickness of the cover layer of the bonding material in the second embodiment can be, for example, 1~150μm, 3~150μm, 5~150μm, 7.5~150μm, 10~150μm, 12.5~150μm, 15~150μm, 20~150μm, 25~150μm, 30~150μm, 40~150μm, 50~150μm, 75~150μm, 1~125μm, 1~100μm, 1~75μm, 1~50μm, 1~40μm, 1~30μm, 1~25μm, 1~20μm, 1~15μm, 1~12.5μm, 1~10μm, 1~7.5μm, 1~5μm, or 1~3μm.

[0169] By making the thickness of the cover layer above or above the aforementioned lower limit, it is easier to suppress the formation of voids in the solder joint that contacts the object being joined. By making it below or below the aforementioned upper limit, it is easier to improve the heat resistance of the solder joint.

[0170] 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. For example, the thickness of the bonding material can be 10~5300 μm or 20~1510 μm.

[0171] The thickness of the bonding material in the second embodiment can be, for example, 2~5300μm, 2~4000μm, 2~3000μm, 2~2000μm, 2~1750μm, 2~1510μm, 2~1200μm, 2~1000μm, 2~750μm, 2~500μm, 2~400μm, 2~300μm, 2~250μm, 2~200μm, 2~150μm, 2~100μm, 2~75μm, 2~50μm, 2~40μm, 2~30μm, 5~5 300μm, 10~5300μm, 15~5300μm, 20~5300μm, 30~5300μm, 40~5300μm, 50~5300μm, 75~5300μm, 100~5300μm, 150~530 0μm, 200~5300μm, 250~5300μm, 300~5300μm, 400~5300μm, 500~5300μm, 750~5300μm, 1000~5300μm, 1200~5300μm.

[0172] The ratio of the thickness of the substrate metal layer to the thickness of the cover layer, expressed as substrate metal layer / cover 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 substrate metal layer / cover layer can be 1 to 500, 2 to 300, 2 to 100, or 2 to 58.

[0173] By making the ratio of the base metal layer to the cover layer within the above range, it is easier to improve the heat resistance of the solder joint, and thus easier to suppress the generation of voids in the solder joint that is in contact with the object being joined.

[0174] In the bonding material of the second embodiment, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is expressed as a ratio of substrate metal layer / cover layer, and for example, it can be 2~500, 3~500, 5~500, 7.5~500, 10~500, 15~500, 20~500, 30~500, 50~500, 100~500, 200~500, 300~500, 2~400, 2~350, 2~300, 2~250, 2~200, 2~150, 2~100, 2~75, 2~60, 2~58, 2~50, 2~30, 2~20, 2~15, 2~10, 2~7.5, 2~5, 2~3.

[0175] By ensuring the ratio of the base metal layer to the cover layer is within the aforementioned range, it is easier to improve the heat resistance of the solder joint, and consequently, easier to suppress the formation of voids in the solder joint that comes into contact with the object being joined. By setting the ratio above the lower limit of the aforementioned range, it is easier to improve the heat resistance of the solder joint. By setting the ratio below the upper limit of the aforementioned range, it is easier to suppress the formation of voids in the solder joint.

[0176] Regarding the bonding material of the second embodiment, the above-mentioned provisions regarding the thickness of the substrate metal layer and the cover layer, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer, the content of the Sn-containing metal constituting the first phase and the content of the Ni and Fe-containing alloy constituting the second phase can be combined arbitrarily.

[0177] Hereinafter, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer refers to the ratio expressed as substrate metal layer (μm) / cover layer (μm).

[0178] For the bonding material of the second embodiment, the thickness of the cover layer is preferably 1 to 150 μm, and the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is 2 to 300. More preferably, the thickness of the cover layer is 5 to 150 μm, and the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is 2 to 200. Even more preferably, the thickness of the cover layer is 5 to 150 μm, and the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is 2 to 100. Particularly preferably, the thickness of the cover layer is 5 to 75 μm, and the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is 2 to 60.

[0179] If the thickness of the cover layer is within the above range, and the ratio of the thickness of the base metal layer to the thickness of the cover layer is within the above range, it is easier to improve the heat resistance of the solder joint and easier to suppress the generation of voids in the solder joint.

[0180] For the bonding material of the second embodiment, the thickness of the substrate metal layer is preferably 150 to 1500 μm, the thickness of the cover layer is preferably 1 to 150 μm, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is preferably 2 to 500 (substrate metal layer / cover layer), the content of the Sn-containing metal constituting the first phase is 30 to 97% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase, the content of the Ni and Fe-containing alloy constituting the second phase is 3 to 70% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase, and the ratio of the content of the Sn-containing metal constituting the first phase to the content of the Ni and Fe-containing alloy constituting the second phase is preferably 0.4 or more and 35 or less (first metal content / second metal content).

[0181] For the bonding material of the second embodiment, it is more preferable that the thickness of the substrate metal layer is 150 to 290 μm, the thickness of the cover layer is 5 to 100 μm, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is 2 to 58 as expressed as substrate metal layer / cover layer, the content of the Sn-containing metal constituting the first phase is 30 to 97% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the alloy containing Ni and Fe constituting the second phase, the content of the Ni and Fe alloy constituting the second phase is 3 to 70% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the alloy containing Ni and Fe constituting the second phase, and the ratio of the content of the first metal to the content of the second metal is 0.4 or more and 35 or less as expressed as the mass ratio of the content of the first metal / the content of the second metal.

[0182] For the bonding material of the second embodiment, the thickness of the substrate metal layer is preferably 1 to 5000 μm, the thickness of the cover layer is preferably 1 to 150 μm, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is preferably 2 to 500 (substrate metal layer / cover layer), the content of the Sn-containing metal constituting the first phase is 30 to 97% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase, the content of the Ni and Fe-containing alloy constituting the second phase is 3 to 70% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase, and the ratio of the content of the Sn-containing metal constituting the first phase to the content of the Ni and Fe-containing alloy constituting the second phase is preferably 0.4 or more and 35 or less (first metal content / second metal content).

[0183] For the bonding material of the second embodiment, the thickness of the substrate metal layer is preferably 1 to 2000 μm, the thickness of the cover layer is preferably 1 to 100 μm, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is preferably 2 to 500 (substrate metal layer / cover layer), the content of the Sn-containing metal constituting the first phase is 30 to 97% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase, the content of the Ni and Fe-containing alloy constituting the second phase is 3 to 70% by mass relative to the total mass (100% by mass) of the Sn-containing metal constituting the first phase and the Ni and Fe-containing alloy constituting the second phase, and the ratio of the content of the Sn-containing metal constituting the first phase to the content of the Ni and Fe-containing alloy constituting the second phase is preferably 0.4 or more and 35 or less (first metal content / second metal content).

[0184] (Preparation method of bonding material) In one embodiment, the bonding material of the second embodiment can be prepared, for example, by the following preparation method.

[0185] The bonding material preparation method of this embodiment is a method for preparing a bonding material having a substrate metal layer and a cover layer covering at least two sides of the substrate metal layer.

[0186] The method for preparing the bonding material in this embodiment includes a pressing step A and any one of pressing steps B1 to B3.

[0187] <Crimping Process A> In the pressing process A, a cover sheet is pressed onto one side of the base metal sheet to cover the surface.

[0188] like Figure 2B As illustrated, a bonding material 1D having a substrate metal layer 2D and a cover layer 3D covering one surface Sd1 of the substrate metal layer 2D is obtained through a pressing process A.

[0189] The substrate metal sheet comprises: a first metal containing Sn and a second metal composed of an alloy containing Ni and Fe.

[0190] The cover sheet contains a metal with a melting point lower than that of the second metal. The cover sheet can be prepared by a known method, for example, by preparing a metal to form a cover sheet of a specified composition, processing the metal into a plate shape, rolling it to a specified thickness, and cutting it into a specified size.

[0191] In this embodiment, the description of the metal contained in the substrate metal sheet, its particle size and content, etc., is the same as that of the substrate metal layer of the bonding material.

[0192] In this embodiment, the description of the metals contained in the cover sheet and their content is the same as that of the cover layer of the bonding material.

[0193] As a pressing method, a known calendering method can be used, such as processing with a twin-roll calender. The number of calendering cycles and the calendering load applied to the base metal sheet and the cover sheet can be appropriately set according to the desired shape and thickness of the materials to be joined.

[0194] There is no particular limitation on the rolling load; for example, it can be 0.1~20kN. There is no particular limitation on the number of rolling cycles; it can be 1~10 times.

[0195] There is no particular limitation on the surface temperature of the calendering roll; for example, it can be 50~150℃.

[0196] In the bonding material obtained through the pressing process A, an intermetallic compound can be formed at the interface between the substrate metal layer and the cover layer.

[0197] The method for preparing the bonding material in this embodiment may include any one of the pressing steps B1 to B3 in the later stage of the pressing step A.

[0198] <Crimping process B1> In the crimping process B1, two bonding materials are prepared, each having a base metal layer and a cover layer covering one side of the base metal layer, obtained in the crimping process A. Hereinafter, the two bonding materials will be referred to as the first bonding material and the second bonding material, respectively.

[0199] like Figure 2C As shown, in the pressing process B1, one surface Sd2 of the substrate metal layer 2D of the first bonding material 1D is pressed together with one surface Sd2 of the substrate metal layer 2D of the second bonding material 1D.

[0200] Through the pressing process B1, a bonding material 1E is obtained having a base metal layer 2E and a cover layer 3E covering two surfaces (i.e., Se1 and Se2) of the base metal layer 2E.

[0201] The crimping method in crimping process B1 can be the same as the crimping method in crimping process A.

[0202] <Crimping process B2> In the pressing process B2, a bonding material having a base metal layer and a cover layer covering one side of the base metal layer is prepared, which is obtained in the pressing process A.

[0203] like Figure 2D As shown, in the crimping step B2, the bonding material 1D is bent and the surface Sd2 of the substrate metal layer 2D of the bonding material 1D is crimped.

[0204] Through the pressing process B2, a bonding material 1E is obtained having a base metal layer 2E and a cover layer 3E covering two surfaces (i.e., Se1 and Se2) of the base metal layer 2E.

[0205] The crimping method in crimping process B2 can be the same as the crimping method in crimping process A.

[0206] <Crimping process B3> In the pressing process B3, a bonding material having a base metal layer and a cover layer covering one side of the base metal layer is prepared, which is obtained in the pressing process A.

[0207] like Figure 2E As shown, in the pressing process B3, the cover sheet 3D' is pressed onto one surface Sd2 of the substrate metal layer 2D of the bonding material 1D.

[0208] Through the pressing process B3, a bonding material 1E is obtained having a base metal layer 2E and a cover layer 3E covering two surfaces (i.e., Se1 and Se2) of the base metal layer 2E.

[0209] The crimping method in crimping step B3 can be the same as the crimping method in crimping step A.

[0210] There are no particular limitations on the preparation method of the substrate metal sheet. For example, the substrate metal sheet can be prepared by a "powder forming process".

[0211] <Powder pressing and forming process> In the powder pressing process, a mixture of metal powders containing a first metal powder containing Sn and a second metal powder composed of an alloy containing Ni and Fe is pressed to form a base metal sheet as a preformed solder.

[0212] The first metal powder and the second metal powder are the same as the <first metal> and <second metal> mentioned above, respectively.

[0213] For the method of pressing a metal powder mixture into shape, a known calendering method can be used, such as processing with a twin-roll calender. The number of calendering cycles and the calendering load applied to the metal powder mixture can be appropriately set according to the desired shape and thickness of the substrate metal sheet.

[0214] There are no particular limitations on the rolling load; for example, it can be 15~40kN.

[0215] When using a calender, there is no particular limitation on the surface temperature of the calender rolls; for example, it can be 50~150℃.

[0216] The bonding material of the second embodiment described above is the same as that of the first embodiment, and it can suppress the generation of voids at the solder joint.

[0217] (Bonding material: Third embodiment) In the bonding material of the third embodiment, the substrate metal layer further comprises a third metal, the surface of which is entirely formed of a metal containing Ni.

[0218] The bonding material in the third embodiment is the same as that in the first embodiment, except that the substrate metal layer contains a third metal.

[0219] <The Third Metal> The surface of the third metal is entirely formed of a Ni-containing metal. That is, in the third metal, Ni is exposed on the surface.

[0220] The Ni content in the metal forming the surface of the third metal is 50% by mass or more and 100% by mass or less relative to the total mass of the metal forming the surface of the third metal.

[0221] The melting point of the metal forming the surface of the third metal is above 300°C, preferably above 500°C, and more preferably 600~1600°C.

[0222] The third metal is preferably dispersed within the substrate metal layer.

[0223] The metal that forms the surface of the third metal can be composed of only Ni, or it can contain metals other than Ni.

[0224] Examples of metals that form the surface of the third metal include Ni monomers, alloys of Ni with metals other than Ni, and metals composed of Ni-containing alloys and other metals, with Ni monomers being preferred.

[0225] Metals other than Ni, in alloys of Ni and Ni, can include, for example, 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 can be one or more. The group of metals other than Ni can be arbitrarily selected from these metals.

[0226] In addition to the metals mentioned above, the metal forming the surface of the third metal may also contain unavoidable impurities. Even in the presence of unavoidable impurities, the effectiveness of the present invention will not be affected.

[0227] The surface of the third metal can be composed of one type of metal or two or more types of metal stacked together.

[0228] When the metal forming the surface integral of the third metal is a metal including Ni and other metals, the Ni content in the metal forming the surface integral is 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, and particularly preferably 98% by mass or more, relative to the total mass of the metal forming the surface integral.

[0229] When the metal forming the surface integral of the third metal contains Fe, the Fe content in the metal forming the surface integral 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 integral of the third metal.

[0230] In the bonding material of the third embodiment, the particle size of the third metal is preferably 0.1 to 1000 μm, more preferably 1 to 300 μm, and even more preferably 10 to 100 μm.

[0231] If the particle size of the third metal is above the lower limit of the above-mentioned preferred range, the thermal conductivity of the solder joint can be easily improved.

[0232] The specific structure of the third metal is illustrated below with examples.

[0233] As explained in (1) below, the third metal can be a homogeneous composition.

[0234] Alternatively, as described in (2) below, the third metal may also have a structure with a variety of different compositions.

[0235] When the third metal is of a homogeneous composition, as explained in (1-1) below, the third metal may be a metal consisting only of Ni, or as explained in (1-2) below, the third metal may be a metal containing Ni and other metals.

[0236] Alternatively, as explained in (2) below, in the case where the third metal has a structure with a variety of different compositions, the third metal may also have a core and a surface layer.

[0237] The following is an explanation of these situations.

[0238] (1) The case where the third metal has a homogeneous composition. (1-1) The case where the third metal consists only of Ni The composition of the third metal is different from that of the first and second metals.

[0239] In this case, the Ni content in the metal forming the entire surface of the third metal is 100% by mass relative to the total mass of the metal forming the entire surface of the third metal. The proportion of Ni in the surface of the third metal is 100% relative to the total surface area (100%) of the third metal.

[0240] The third metal may contain unavoidable impurities in addition to Ni. Even in the presence of unavoidable impurities, the effectiveness of the invention will not be affected.

[0241] (1-2) Cases where the third metal includes Ni and metals other than Ni The composition of the third metal is different from that of the first and second metals.

[0242] The third metal can be a metal other than Ni mixed with Ni, a metal other than Ni alloyed with Ni, or a metal containing Ni mixed with other metals.

[0243] The third metal can include metals other than Ni, such as Ag, Cu, In, Bi, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, Sn, and As. One or more of these metals other than Ni can be included. The group of metals other than Ni can be arbitrarily chosen from these metals.

[0244] In addition to the metals mentioned above, the third metal may also contain unavoidable impurities. Even in the presence of unavoidable impurities, the effectiveness of the present invention will not be affected.

[0245] The third metal in (1-2) can be one or more.

[0246] When the third metal is a metal including Ni and other metals, the content of Ni in the third metal is 50% by mass or more and 100% by mass or less relative to the total mass of the third metal, 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.

[0247] When the third metal contains Fe, the Fe content in the third metal is preferably 0% by mass or more and less than 5% by mass relative to the total mass of the third metal.

[0248] (2) The third metal has a structure consisting of a core and a surface layer covering the core. like Figure 3 As shown, the third metal 30A has a core 301 and a surface layer 302 covering the core 301. Rc refers to the grain size of the core 301 (hereinafter, Rc is also referred to as the core diameter). Rs refers to the thickness of the surface layer 302.

[0249] The composition of the metal forming the surface layer differs from that of the metal forming the core. The composition of the third metal also differs from that of the first and second metals.

[0250] The composition of the metal forming the surface layer of the third metal is different from that of the first and second metals.

[0251] ·surface layer The metal forming the surface layer of the third metal can be composed of only Ni, or it can be a metal containing Ni and other metals.

[0252] That is, the metal forming the surface layer of the third metal can be elemental Ni, or it can be a metal other than Ni that is alloyed with Ni.

[0253] The metal that forms the surface layer of the third metal is preferably elemental Ni.

[0254] The surface layer forming the third metal can contain metals other than Ni, such as Ag, Cu, In, Bi, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, Sn, and As. One or more of these metals other than Ni can be included. The group of metals other than Ni can be arbitrarily selected from these metals.

[0255] In addition to the metals mentioned above, the surface layer forming the third metal may also contain unavoidable impurities. Even in the presence of unavoidable impurities, the effectiveness of the present invention will not be affected.

[0256] The surface layer of the third metal can be made of one type of metal or can be made of two or more types of metal.

[0257] When the metal forming the surface layer of the third metal is a metal including Ni and other metals, 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 relative to the total mass of the metal forming the surface layer of the third metal, preferably 70% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 98% by mass or more.

[0258] When the metal forming the surface layer of the third metal contains Fe, the Fe content 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.

[0259] At least a portion of the core's surface is covered by a surface layer. The surface layer may cover a portion of the core or the entire core, preferably the entire core. Figure 3 In the middle, the entire surface of the core 301 is covered by the surface layer 302.

[0260] The ratio of the area of ​​the core surface covered by the outer layer to the total surface area of ​​the core (100%) is preferably 50% or more and 100% or less, more preferably 70% or more and 100% or less, further preferably 90% or more and 100% or less, particularly preferably 95% or more and 100% or less, and most preferably 100%.

[0261] The thickness Rs of the surface layer of the third metal can be, for example, 0.01 μm or more and 100 μm or less. The thickness of the surface layer of the third metal can 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 can be less than 50 μm, less than 30 μm, less than 10 μm, less than 5 μm, or less than 3 μm.

[0262] In this specification, the thickness Rs of the surface layer of the third metal, the core diameter Rc of the core of the third metal, and the thickness Ri of the intermediate layer (described later) can be measured from the cross-sectional structure of the third metal using optical microscopes, SEM, transmission electron microscopes (TEM), etc.

[0263] The thickness Rs of the surface layer of the third metal can be determined using an Auger electron spectroscopy analyzer.

[0264] Alternatively, the core diameter Rc of the third metal core can be determined as described below. When preparing the third metal powder, the particle size of the metal powder prepared for use as the core can be the core diameter Rc.

[0265] The surface of the third metal can be a coating formed by plating.

[0266] As a plating process, well-known methods such as electroplating and electroless plating can be cited.

[0267] The metal forming the third metal surface layer has a melting point of over 300°C, preferably over 500°C, and more preferably 600~1600°C.

[0268] Core The metal forming the core of the third metal can be a single elemental metal, a mixture of two or more elemental metals, an alloy of two or more metal elements, a mixture of alloys of two or more metal elements, or a metal formed by mixing an alloy of two or more metal elements with an elemental metal.

[0269] The core, as a third metal, can contain metals such as Ag, Cu, In, Bi, Ni, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, Sn, and As. It can contain one or more of these metals. The group of metals that the core can contain can be arbitrarily selected from these metals.

[0270] In addition to the aforementioned metals, the core of the third metal may also contain unavoidable impurities. Even in the presence of unavoidable impurities, the effectiveness of the invention will not be affected.

[0271] The metal forming the core of the third metal can be one type or two or more types.

[0272] The core diameter Rc of the third metal core is preferably 0.1~1000μm, more preferably 3~800μm, even more preferably 5~500μm, particularly preferably 8~300μm, and most preferably 25~150μm.

[0273] The third metal 30A can be one type or two or more types.

[0274] <The relationship between the contents of the first, second, and third metals> In the substrate metal layer of the bonding material in the third embodiment, the content of the first metal is preferably 10 to 98% by mass, more preferably 30 to 90% by mass, and even more preferably 40 to 80% by mass, relative to the total mass of the first metal, the second metal and the third metal.

[0275] In the substrate metal layer of the bonding material in the third embodiment, the content of the second metal is preferably 1 to 70% by mass, more preferably 3 to 30% by mass, relative to the total mass of the first metal, the second metal and the third metal.

[0276] By keeping the content of the second metal within the above-mentioned preferred range, the heat resistance of the solder joint is further improved.

[0277] In the substrate metal layer of the bonding material in the third embodiment, the content of the third metal is preferably 1 to 70% by mass, more preferably 5 to 50% by mass, relative to the total mass of the first metal, the second metal and the third metal.

[0278] By keeping the content of the third metal within the above-mentioned preferred range, it is easier to improve the thermal conductivity of the solder joint.

[0279] In the substrate metal layer of the bonding material in the third embodiment, the total content of the second metal and the third metal is preferably 1 to 90% by mass, more preferably 3 to 70% by mass, and even more preferably 20 to 60% by mass, relative to the total mass of the first metal, the second metal and the third metal.

[0280] In the substrate metal layer of the bonding material in the third embodiment, the total content of the first metal, the second metal, and the third metal does not exceed 100% by mass.

[0281] In the substrate metal layer of the bonding material in the third embodiment, the total content of the first metal, the second metal and the third metal relative to the total mass of the substrate metal layer is preferably 60 to 100% by mass, more preferably 80 to 100% by mass, even more preferably 90 to 100% by mass, and may also be 100% by mass.

[0282] In the substrate metal layer of the bonding material in 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 0.1 or more and 100 or less, more preferably 1 or more and 50 or less, and even more preferably 4 or more and 30 or less.

[0283] By keeping the mass ratio within the preferred range described above, it is easier to suppress voids in the solder joint, and the heat resistance of the solder joint is further improved.

[0284] In the substrate metal layer of the bonding material in 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 0.1 or more and 100 or less, more preferably 0.3 or more and 20 or less, and even more preferably 1 or more and 5 or less.

[0285] By keeping the mass ratio within the preferred range described above, it is easier to suppress voids in the solder joint and to improve the thermal conductivity of the solder joint.

[0286] In the substrate metal layer of the bonding material in 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 to the content of the second metal, is preferably 0.01 or more and 100 or less, more preferably 0.1 or more and 50 or less, and even more preferably 1 or more and 30 or less.

[0287] By keeping the mass ratio within the above-mentioned preferred range, it is easier to improve the heat resistance of the solder joint and the thermal conductivity of the solder joint.

[0288] In the bonding material of the third embodiment, the description of the composition of the covering layer is the same as that of the first embodiment.

[0289] In the bonding material of the third embodiment, the description of the thickness of the substrate metal layer and the cover layer is the same as that of the first embodiment.

[0290] In the bonding material of the third embodiment, the thickness of the substrate metal layer is preferably 5 to 5000 μm, more preferably 150 to 1500 μm, and even more preferably 150 to 290 μm.

[0291] In the bonding material of the third embodiment, the thickness of the cover layer is preferably 1 to 150 μm, more preferably 3 to 100 μm, and even more preferably 5 to 75 μm.

[0292] In the bonding material according to the third embodiment, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is expressed as a substrate metal layer / cover layer ratio, which is preferably 1 to 500, more preferably 2 to 100, and even more preferably 2 to 58.

[0293] The thickness of the substrate metal layer of the bonding material in the third embodiment can be, for example, 1~5000μm, 3~5000μm, 5~5000μm, 10~5000μm, 15~5000μm, 20~5000μm, 25~5000μm, 30~5000μm, 40~5000μm, 50~5000μm, 75~5000μm, 100~5000μm, 125~5000μm, 150~5000μm, 175~5000μm, 200~5000μm, 250~5000μm, 290~5000μm, 300~5000μm, 350~5000μm, 400~5000μm, 500~5000μm, 75 ... 000μm, 1000~5000μm, 1200~5000μm, 1500~5000μm, 1~4000μm, 1~3500μm, 1~30 00μm, 1~2500μm, 1~2000μm, 1~1500μm, 1~1200μm, 1~1000μm, 1~750μm, 1~500μm , 1~400μm, 1~350μm, 1~300μm, 1~290μm, 1~250μm, 1~200μm, 1~175μm, 1~150μm, 1~125μm, 1~100μm, 1~75μm, 1~50μm, 1~40μm, 1~30μm, 1~25μm, 1~20μm, 1~15μm.

[0294] By making the thickness of the substrate metal layer above or above the aforementioned lower limit, it is easier to improve the heat resistance of the solder joint. By making it below or above the aforementioned upper limit, it is easier to suppress the generation of voids in the solder joint that is in contact with the object being joined.

[0295] The thickness of the cover layer of the bonding material in the third embodiment can be, for example, 1~150μm, 3~150μm, 5~150μm, 7.5~150μm, 10~150μm, 12.5~150μm, 15~150μm, 20~150μm, 25~150μm, 30~150μm, 40~150μm, 50~150μm, 75~150μm, 1~125μm, 1~100μm, 1~75μm, 1~50μm, 1~40μm, 1~30μm, 1~25μm, 1~20μm, 1~15μm, 1~12.5μm, 1~10μm, 1~7.5μm, 1~5μm, or 1~3μm.

[0296] By making the thickness of the cover layer above or above the aforementioned lower limit, it is easier to suppress the formation of voids in the solder joint that contacts the object being joined. By making it below or below the aforementioned upper limit, it is easier to improve the heat resistance of the solder joint.

[0297] The thickness of the bonding material in the third embodiment can be, for example, 2~5300μm, 2~4000μm, 2~3000μm, 2~2000μm, 2~1750μm, 2~1510μm, 2~1200μm, 2~1000μm, 2~750μm, 2~500μm, 2~400μm, 2~300μm, 2~250μm, 2~200μm, 2~150μm, 2~100μm, 2~75μm, 2~50μm, 2~40μm, 2~30μm, 5~5 300μm, 10~5300μm, 15~5300μm, 20~5300μm, 30~5300μm, 40~5300μm, 50~5300μm, 75~5300μm, 100~5300μm, 150~530 0μm, 200~5300μm, 250~5300μm, 300~5300μm, 400~5300μm, 500~5300μm, 750~5300μm, 1000~5300μm, 1200~5300μm.

[0298] In the bonding material of the third embodiment, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is expressed as a ratio of substrate metal layer / cover layer, and for example, it can be 2~500, 3~500, 5~500, 7.5~500, 10~500, 15~500, 20~500, 30~500, 50~500, 100~500, 200~500, 2~400, 2~350, 2~300, 2~250, 2~200, 2~150, 2~100, 2~75, 2~60, 2~58, 2~50, 2~30, 2~20, 2~15, 2~10, 2~7.5, 2~5, 2~3.

[0299] By ensuring the ratio of the base metal layer to the cover layer is within the aforementioned range, it is easier to improve the heat resistance of the solder joint, and consequently, easier to suppress the formation of voids in the solder joint that comes into contact with the object being joined. By setting the ratio above the lower limit of the aforementioned range, it is easier to improve the heat resistance of the solder joint. By setting the ratio below the upper limit of the aforementioned range, it is easier to suppress the formation of voids in the solder joint.

[0300] Regarding the bonding material of the third embodiment, the above-mentioned provisions regarding the thickness of the base metal layer and the cover layer, the ratio of the thickness of the base metal layer to the thickness of the cover layer, the structure of the third metal, and the content of the first metal, the second metal, and the third metal can be combined arbitrarily.

[0301] Hereinafter, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer refers to the ratio expressed as substrate metal layer (μm) / cover layer (μm).

[0302] In the bonding material of the third embodiment, it is preferable that the thickness of the cover layer is 1 to 150 μm and the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is 2 to 300; more preferably, the thickness of the cover layer is 5 to 150 μm and the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is 2 to 200; even more preferably, the thickness of the cover layer is 5 to 150 μm and the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is 2 to 100; particularly preferably, the thickness of the cover layer is 5 to 75 μm and the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is 2 to 60.

[0303] If the thickness of the cover layer is within the above range, and the ratio of the thickness of the base metal layer to the thickness of the cover layer is within the above range, it is easier to improve the heat resistance of the solder joint and easier to suppress the generation of voids in the solder joint.

[0304] For the bonding material of the third embodiment, the thickness of the substrate metal layer is preferably 150-290 μm, the thickness of the cover layer is preferably 5-100 μm, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is preferably 2-58 (substrate metal layer / cover layer), the third metal is composed only of Ni, the content of the first metal relative to the total mass of the first metal, the second metal and the third metal is 30-90% by mass, the content of the second metal relative to the total mass of the first metal, the second metal and the third metal is 3-30% by mass, the content of the third metal relative to the total mass of the first metal, the second metal and the third metal is 5-50% by mass, the ratio of the content of the first metal to the content of the second metal (mass ratio of first metal content / second metal content) is 4 or more and 30 or less, the ratio of the content of the first metal to the content of the third metal (mass ratio of first metal content / third metal content) 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 (mass ratio of third metal content / second metal content) is 1 or more and 30 or less.

[0305] Alternatively, for the bonding material of the third embodiment, the thickness of the substrate metal layer is preferably 150-290 μm, the thickness of the cover layer is preferably 5-100 μm, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is 2-58 (substrate metal layer / cover layer), the third metal has a structure consisting of a core and a surface layer covering the core, the metal forming the surface layer of the third metal is composed only of Ni, the content of the first metal is 30-90% by mass relative to the total mass of the first metal, the second metal, and the third metal, and the content of the second metal is relative to the total mass of the first metal, the second metal, and the third metal. The content of the third metal is 3-30% by mass, and the content of the third metal is 5-50% by mass relative 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 the mass ratio of the content of the first metal to 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 the mass ratio of the content of the first metal to the content of the third metal, is 1 or more and 5 or less. The ratio of the content of the second metal to the content of the third metal, expressed as the mass ratio of the content of the third metal to the mass ratio of the second metal, is 1 or more and 30 or less.

[0306] For the bonding material of the third embodiment, the thickness of the substrate metal layer is preferably 1 to 5000 μm, the thickness of the cover layer is preferably 1 to 150 μm, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is preferably 2 to 500 (substrate metal layer / cover layer), the third metal is composed only of Ni, the content of the first metal relative to the total mass of the first metal, the second metal and the third metal is 30 to 90% by mass, the content of the second metal relative to the total mass of the first metal, the second metal and the third metal is 3 to 30% by mass, the content of the third metal relative to the total mass of the first metal, the second metal and the third metal is 5 to 50% by mass, the ratio of the content of the first metal to the content of the second metal (mass ratio of first metal content / second metal content) is 4 or more and 30 or less, the ratio of the content of the first metal to the content of the third metal (mass ratio of first metal content / third metal content) 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 (mass ratio of third metal content / second metal content) is 1 or more and 30 or less.

[0307] For the bonding material of the third embodiment, the thickness of the substrate metal layer is preferably 1 to 500 μm, the thickness of the cover layer is preferably 1 to 100 μm, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is preferably 2 to 500 (substrate metal layer / cover layer), the third metal is composed only of Ni, the content of the first metal relative to the total mass of the first metal, the second metal and the third metal is 30 to 90% by mass, the content of the second metal relative to the total mass of the first metal, the second metal and the third metal is 3 to 30% by mass, the content of the third metal relative to the total mass of the first metal, the second metal and the third metal is 5 to 50% by mass, the ratio of the content of the first metal to the content of the second metal (mass ratio of first metal content / second metal content) is 4 or more and 30 or less, the ratio of the content of the first metal to the content of the third metal (mass ratio of first metal content / third metal content) 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 (mass ratio of third metal content / second metal content) is 1 or more and 30 or less.

[0308] The bonding material of the third embodiment can be prepared using the same method as the bonding material of the first embodiment.

[0309] Similar to the bonding material of the first embodiment, the bonding material of the third embodiment can suppress the generation of voids in the solder joint.

[0310] Furthermore, the bonding material in the third embodiment contains a third metal through a base metal layer, which can further improve the thermal conductivity of the solder joint. Although the reason for this effect is not yet certain, it is speculated as follows.

[0311] Compared to Cu and Ni, intermetallic compounds have lower thermal conductivity. For example, the thermal conductivity of Cu and Ni is 401 W / m·K and 88.5 W / m·K, respectively, while the thermal conductivity of intermetallic compounds Cu6Sn5 (Cu3Sn) and Ni3Sn4 is 34 W / m·K and 20 W / m·K, respectively.

[0312] The surface of the third metal is entirely formed of Ni-containing metal. Ni has low reactivity with Sn, making it difficult to form Ni3Sn4. That is, because the surface of the third metal is unlikely to react with Sn in the substrate metal layer to form intermetallic compounds, the thermal conductivity of the solder joint can be improved.

[0313] (Bonding material: Fourth embodiment) The bonding material of the fourth embodiment has a substrate metal layer and a cover layer covering at least one side of the substrate metal layer.

[0314] Figure 4 This is an example of a SEM image showing a cross-section of the bonding material in the thickness direction according to the fourth embodiment. Figure 4 In the process, the bonding material 1C has a substrate metal layer 2C and a cover layer 3C covering both sides of the substrate metal layer 2C.

[0315] Figure 4 The substrate metal layer 2C shown has a metal structure comprising a first phase 10 as a continuous phase, a second phase 20 dispersed in the first phase, and a third phase 30 dispersed in the first phase.

[0316] Figure 4 In the bonding material 1C shown, the thickness of the substrate metal layer is 285 μm, and the thickness of the capping layer is 7.5 μm. In the substrate metal layer 2C, the content of the metal forming the first phase is 65% by mass relative to the total mass of the substrate metal layer, the content of the metal forming the second phase is 10% by mass relative to the total mass of the substrate metal layer, and the content of the metal forming the third phase is 35% by mass relative to the total mass of the substrate metal layer. The content of Ni in the second phase is 90% by mass relative to the total mass of the second phase, and the content of Fe in the second phase is 10% by mass relative to the total mass of the second phase.

[0317] The bonding material in the fourth embodiment is a covering material on at least one side of the substrate metal layer, to which a covering layer is attached.

[0318] The bonding material of the fourth embodiment is the same as that of the bonding material of the second embodiment, except that the substrate metal layer has a third phase.

[0319] In the substrate metal layer, the third phase 30 is dispersed in the first phase 10.

[0320] The surface of the third phase 30 is entirely composed of a metal containing Ni.

[0321] The bonding material of the fourth embodiment is the same as that of the bonding material of the second embodiment, except that the substrate metal layer has a third phase.

[0322] The description of the metal whose surface contains Ni, its grain size, and its content is the same as that of the <Third Metal> in the Third Embodiment.

[0323] The description of the overall melting point of the metal that forms the surface monolith of the third phase is the same as that of the metal that forms the surface monolith of the third metal.

[0324] The description of the metal constituting the first phase and its content is the same as that of the <first metal> in the third embodiment.

[0325] The description of the metals constituting the second phase and their content is the same as that of the <second metal> in the third embodiment.

[0326] When the third phase has a uniform composition, the overall composition of the metal constituting the third phase is different from the overall composition of the metal constituting the first phase and the overall composition of the alloy constituting the second phase.

[0327] The description of the melting point of the metal constituting the third phase as a whole is the same as the description of the melting point of the third metal.

[0328] The particle size of the third phase can be the particle size of the third metal powder prepared to form the third phase.

[0329] When the third phase has a structure consisting of a core and a surface layer covering the core, the overall composition of the metal forming the surface layer of the third phase is different from the overall composition of the metal constituting the first phase and the overall composition of the alloy constituting the second phase.

[0330] The melting point of the metal forming the third phase surface layer is the same as that of the metal forming the third metal surface layer.

[0331] The descriptions of the core diameter and surface thickness of the third phase are the same as those of the core diameter Rc and surface thickness Rs of the third metal.

[0332] In the bonding material of the fourth embodiment, the description of the composition of the covering layer is the same as that of the second embodiment.

[0333] In the bonding material of the fourth embodiment, the description of the thickness of the substrate metal layer and the cover layer is the same as that of the third embodiment.

[0334] The thickness of the substrate metal layer can be, for example, 1~5000μm, 3~5000μm, 5~5000μm, 10~5000μm, 15~5000μm, 20~5000μm, 25~5000μm, 30~5000μm, 40~5000μm, 50~5000μm, 75~5000μm, 100~5 000μm, 125~5000μm, 150~5000μm, 175~5000μm, 200~5000μm, 250~5000μm, 29 0~5000μm, 300~5000μm, 350~5000μm, 400~5000μm, 500~5000μm, 750~5000μm, 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~ 400μm, 1~350μm, 1~300μm, 1~290μm, 1~250μm, 1~200μm, 1~175μm, 1~150μm, 1 ~125μm, 1~100μm, 1~75μm, 1~50μm, 1~40μm, 1~30μm, 1~25μm, 1~20μm, 1~15μm.

[0335] By making the thickness of the substrate metal layer above or above the aforementioned lower limit, it is easier to improve the heat resistance of the solder joint. By making it below or above the aforementioned upper limit, it is easier to suppress the generation of voids in the solder joint that is in contact with the object being joined.

[0336] The thickness of the capping layer can be, for example, 1~150μm, 3~150μm, 5~150μm, 7.5~150μm, 10~150μm, 12.5~150μm, 15~150μm, 20~150μm, 25~150μm, 30~150μm, 40~150μm, 50~150μm, 75~150μm, 1~125μm, 1~100μm, 1~75μm, 1~50μm, 1~40μm, 1~30μm, 1~25μm, 1~20μm, 1~15μm, 1~12.5μm, 1~10μm, 1~7.5μm, 1~5μm, or 1~3μm.

[0337] By making the thickness of the cover layer above or above the aforementioned lower limit, it is easier to suppress the formation of voids in the solder joint that contacts the object being joined. By making it below or below the aforementioned upper limit, it is easier to improve the heat resistance of the solder joint.

[0338] The thickness of the bonding material can be, for example, 2~5300μm, 2~4000μm, 2~3000μm, 2~2000μm, 2~1750μm, 2~1510μm, 2~1200μm, 2~1000μm, 2~750μm, 2~500μm, 2~400μm, 2~300μm, 2~250μm, 2~200μm, 2~150μm, 2~100μm, 2~75μm, 2~50μm, 2~40μm, 2~30μm, 5~5300μm. m, 10~5300μm, 15~5300μm, 20~5300μm, 30~5300μm, 40~5300μm, 50~5300μm, 75~5300μm, 100~5300μm, 150~5300μm m, 200~5300μm, 250~5300μm, 300~5300μm, 400~5300μm, 500~5300μm, 750~5300μm, 1000~5300μm, 1200~5300μm.

[0339] The ratio of the thickness of the substrate metal layer to the thickness of the cover layer is expressed as the substrate metal layer / cover layer ratio, and can be, for example, 2~500, 3~500, 5~500, 7.5~500, 10~500, 15~500, 20~500, 30~500, 50~500, 100~500, 200~500, 2~400, 2~350, 2~300, 2~250, 2~200, 2~150, 2~100, 2~75, 2~60, 2~58, 2~50, 2~30, 2~20, 2~15, 2~10, 2~7.5, 2~5, 2~3.

[0340] By ensuring the ratio of the base metal layer to the cover layer is within the aforementioned range, it is easier to improve the heat resistance of the solder joint, and consequently, easier to suppress the formation of voids in the solder joint that comes into contact with the object being joined. By setting the ratio above the lower limit of the aforementioned range, it is easier to improve the heat resistance of the solder joint. By setting the ratio below the upper limit of the aforementioned range, it is easier to suppress the formation of voids in the solder joint.

[0341] Hereinafter, the ratio of the thickness of the substrate metal layer to the thickness of the cover layer refers to the ratio expressed as substrate metal layer (μm) / cover layer (μm).

[0342] For the bonding material of the fourth embodiment, the thickness of the cover layer is preferably 1 to 150 μm, and the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is 2 to 300. More preferably, the thickness of the cover layer is 5 to 150 μm, and the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is 2 to 200. Even more preferably, the thickness of the cover layer is 5 to 150 μm, and the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is 2 to 100. Particularly preferably, the thickness of the cover layer is 5 to 75 μm, and the ratio of the thickness of the substrate metal layer to the thickness of the cover layer is 2 to 60.

[0343] If the thickness of the cover layer is within the above range, and the ratio of the thickness of the base metal layer to the thickness of the cover layer is within the above range, it is easier to improve the heat resistance of the solder joint and easier to suppress the generation of voids in the solder joint.

[0344] For the bonding material of the fourth embodiment, the thickness of the substrate metal layer is preferably 1-5000 μm, the thickness of the capping layer is preferably 1-150 μm, the ratio of the thickness of the substrate metal layer to the thickness of the capping layer is preferably 2-500 (substrate metal layer / capping layer), the metal constituting the third phase is composed only of Ni, the content of the metal constituting the first phase is 30-90% by mass relative to the total mass of the metal constituting the first phase, the alloy constituting the second phase, and the metal constituting the third phase, the content of the alloy constituting the second phase is 3-30% by mass relative to the total mass of the metal constituting the first phase, the alloy constituting the second phase, and the metal constituting the third phase, and the content of the metal constituting the third phase is relatively... The total mass of the metal, the alloy constituting the second phase, and the metal constituting the third phase is 5 to 50% by mass. The ratio of the content of the metal constituting the first phase to the content of the alloy constituting the second phase, expressed as the mass ratio of the content of the metal constituting the first phase to the content of the alloy constituting the second phase, is 4 or more and 30 or less. The ratio of the content of the metal constituting the first phase to the content of the metal constituting the third phase, expressed as the mass ratio of the content of the metal constituting the first phase to the content of the metal constituting the third phase, is 1 or more and 5 or less. The ratio of the content of the alloy constituting the second phase to the content of the metal constituting the third phase, expressed as the mass ratio of the content of the metal constituting the third phase to the content of the alloy constituting the second phase, is 1 or more and 30 or less.

[0345] For the bonding material of the fourth embodiment, the thickness of the substrate metal layer is preferably 1-500 μm, the thickness of the capping layer is preferably 1-100 μm, the ratio of the thickness of the substrate metal layer to the thickness of the capping layer is preferably 2-500 (substrate metal layer / capping layer), the metal constituting the third phase is composed only of Ni, the content of the metal constituting the first phase is 30-90% by mass relative to the total mass of the metal constituting the first phase, the alloy constituting the second phase, and the metal constituting the third phase, the content of the alloy constituting the second phase is 3-30% by mass relative to the total mass of the metal constituting the first phase, the alloy constituting the second phase, and the metal constituting the third phase, and the content of the metal constituting the third phase is relatively... The total mass of the alloy constituting the second phase and the metal constituting the third phase is 5 to 50% by mass. The ratio of the content of the metal constituting the first phase to the content of the alloy constituting the second phase, expressed as the mass ratio of the content of the metal constituting the first phase to the content of the alloy constituting the second phase, is 4 or more and 30 or less. The ratio of the content of the metal constituting the first phase to the content of the metal constituting the third phase, expressed as the mass ratio of the content of the metal constituting the first phase to the content of the metal constituting the third phase, is 1 or more and 5 or less. The ratio of the content of the alloy constituting the second phase to the content of the metal constituting the third phase, expressed as the mass ratio of the content of the metal constituting the third phase to the content of the alloy constituting the second phase, is 1 or more and 30 or less.

[0346] The bonding material of the fourth embodiment is the same as that of the bonding material of the third embodiment, which can suppress the generation of voids in the solder joint and further improve the thermal conductivity of the solder joint.

[0347] The bonding material of the fourth embodiment uses a third metal powder in addition to the first metal powder and the second metal powder, and can be prepared by the same preparation method as the bonding material of the second embodiment.

[0348] The first metal powder, the second metal powder, and the third metal powder are the same as the <first metal>, <second metal>, and <third metal> mentioned above, respectively.

[0349] The bonding material of the fourth embodiment can be prepared using the same method as the bonding material of the second embodiment.

[0350] (Bonding material: Fifth embodiment) In the bonding material of the fifth embodiment, the substrate metal layer further includes a third metal 30B, the surface of which is entirely formed of a metal containing Ni. For example... Figure 5 As shown, the third metal 30B has an intermediate layer 303 between the core 301 and the surface layer 302 covering the core 301. The intermediate layer 303 is adjacent to both the core 301 and the surface layer 302. Ri refers to the thickness of the intermediate layer 303.

[0351] The bonding material of the fifth embodiment is the same as that of the first embodiment, except that the substrate metal layer includes a third metal 30B.

[0352] The intermediate layer can cover a portion of the core's surface or the entire surface of the core, preferably covering the entire surface of the core. Figure 5 In the middle, the intermediate layer 303 covers the entire surface of the core 301.

[0353] The proportion of the surface area of ​​the core covered by the intermediate layer to the total surface area of ​​the core (100%) is preferably 50% or more and 100% or less, more preferably 70% or more and 100% or less, further preferably 90% or more and 100% or less, particularly preferably 95% or more and 100% or less, and most preferably 100%.

[0354] The composition of the metal that forms the intermediate layer is different from that of the metal that forms the core and the metal that forms the surface layer.

[0355] The intermediate layer can be one layer or two or more layers.

[0356] The metal forming the intermediate layer can be a single elemental metal or an alloy of two or more metallic elements.

[0357] Metals that can be included in the intermediate layer include, for example, Ag, Cu, In, Bi, Ni, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, Sn, and As. One or more of these metals can be included. The group of metals that can be included in the intermediate layer can be arbitrarily selected from these metals.

[0358] In addition to the aforementioned metals, the intermediate layer may also contain unavoidable impurities. Even in the presence of unavoidable impurities, the effectiveness of the invention will not be affected.

[0359] There can be one or more intermediate layers.

[0360] The thickness Ri of the intermediate layer can be, for example, greater than 0.01 μm and less than 100 μm, greater than 0.05 μm and less than 50 μm, or greater than 0.1 μm and less than 10 μm.

[0361] The intermediate layer can also be a coating formed through a plating process.

[0362] As a plating process, well-known methods such as electroplating and electroless plating can be cited.

[0363] The core 301 and surface 302 of the third metal 30B can be made of the same material as those described above in the third metal 30A.

[0364] The third metal 30B can be one type or two or more types.

[0365] The bonding material of the fifth embodiment is the same as that of the bonding material of the third embodiment, which can suppress the generation of voids in the solder joint and further improve the thermal conductivity of the solder joint.

[0366] The surface layer 302 of the third metal 30B is easily provided by having an intermediate layer 303 in the third metal 30B.

[0367] (Other implementation methods) In other embodiments of the bonding material, only one side of the substrate metal layer is covered by the cover layer. Other embodiments of the bonding material may also be a covering material formed by pressing one side of the substrate metal layer to the cover layer.

[0368] A bonding material in which only one side of the substrate metal layer is covered by a cover layer can be prepared by the <pressing step A> described above in the bonding material preparation method of the second embodiment.

[0369] Alternatively, in the bonding material of other embodiments, the substrate metal layer may have a fourth metal in addition to the first, second, and third metals described in the third embodiment. The fourth metal is a different metal from the first, second, and third metals.

[0370] The metal that forms the fourth metal can be a single elemental metal, a mixture of two or more elemental metals, an alloy formed by two or more metallic elements, a mixture of alloys formed by two or more metallic elements, or a metal formed by mixing an alloy formed by two or more metallic elements with an elemental metal.

[0371] Metals that can be included as the fourth metal include, for example, Ag, Cu, In, Bi, Ni, Ge, P, Co, Ga, Zn, Sb, Pb, Au, Al, Pt, Pd, Fe, Mn, Zr, Sn, and As. One or more of these metals can be included. The group of metals that can be included as the fourth metal can be arbitrarily chosen from these metals.

[0372] The particle size of the fourth metal powder is preferably 0.1~1000μm, more preferably 1~100μm, and even more preferably 5~50μm.

[0373] The metals constituting the fourth metal powder may include one type or two or more types.

[0374] The fourth metal powder is not limited to one type; two or more metal powders with different compositions may also be used.

[0375] Alternatively, the bonding material in other embodiments is a bonding material having a base metal layer as described in the above embodiments and a cover layer covering at least one side of the base metal layer, for example, prepared by hot-dip plating, sputtering or the like.

[0376] When using a hot-dip plating method, for example, by immersing the substrate metal layer in molten metal forming a cover layer and cooling it, at least one side of the substrate metal layer can be covered with the metal forming the cover layer, thereby obtaining the bonding material of this embodiment.

[0377] When using a sputtering method, by sputtering a metal to form a cover layer onto the substrate metal layer, and covering at least one side of the substrate metal layer with the metal forming the cover layer, the bonding material of this embodiment can be obtained.

[0378] Alternatively, the bonding material in other embodiments may be a bonding material formed by covering the substrate metal layer in the second embodiment with a coating layer using methods such as hot-dip plating or sputtering.

[0379] (Solder joint) In one embodiment of the present invention, a solder joint is formed using the bonding material described in the above embodiment. The solder joint of this embodiment does not melt even when the power semiconductor is operating at high temperatures, and can suppress the formation of voids at the solder joint.

[0380] (Preparation method of solder joint) In one embodiment of the present invention, there is a method for preparing a solder joint, which uses a bonding material prepared by the above-described (method for preparing bonding material) to form a bonding portion between objects.

[0381] There are no particular limitations on the objects to be bonded using this fabrication method. For example, by applying this fabrication method, semiconductor devices and substrates can be bonded.

[0382] Examples of semiconductor components include silicon carbide (SiC) chips and Si chips.

[0383] Examples of substrates include circuit boards, ceramic substrates, metal substrates, and DCB (Direct Copper Bonding) substrates. Electrodes on the substrate can be, for example, Cu electrodes, or Cu electrodes that have undergone any of the following treatments: Sn plating, Ni plating, Ni-Au plating, Ni-Pd plating, or Ni-Pd-Au plating.

[0384] In addition, during bonding, flux can be pre-applied to one or both sides of the bonding material that serve as the bonding surface, the bonding surface of the semiconductor element, or the bonding surface of the substrate.

[0385] The temperature at which semiconductor elements are joined to a substrate is preferably 120°C or higher and 400°C or lower, but can be 200°C or higher and 400°C or lower, or 250°C or higher and 400°C or lower. The solder joint preparation method of this embodiment is useful for joining under high temperature conditions (above 250°C).

[0386] The atmosphere at which the objects are bonded can be atmospheric, inert, such as nitrogen, or a reducing atmosphere.

[0387] In a nitrogen atmosphere, it is preferable to adjust the pressure applied during bonding to be 0.1 MPa or more and 10 MPa or less. By bonding the object under a nitrogen atmosphere, the effect of suppressing void formation can be enhanced.

[0388] In a reducing atmosphere, objects can be joined without pressure.

[0389] Using the bonding material described above, a joint can be formed between objects. The shear strength of this joint can be 12~100N, 16~50N, or 20~35N under conditions of 6.0mm / min and 250°C.

[0390] The shear strength of the joint can be measured, for example, as follows.

[0391] The bonding material of the object was cut into 5mm×5mm pieces to obtain test pieces.

[0392] Next, the test piece was mounted on a 0.5 mm thick, 50 mm × 50 mm unplated Ni Cu substrate. The surface roughness of the substrate was set to Sa = 0.31 μm and Sz = 8.53 μm. The surface roughness of the substrate could be measured, for example, using a laser microscope. A VK-X1000 (manufactured by Keyence Corporation) could be used as an example of a laser microscope.

[0393] Next, a Cu plate with a thickness of 0.5 mm and a size of 5 mm × 5 mm is mounted on the bonding material.

[0394] Next, using a curve with a peak temperature of 250°C and a cooling rate of 2°C / sec, solder joints were fabricated in a formic acid atmosphere while being pressurized and in a reflow oven.

[0395] Next, for the fabricated solder joint, the shear strength (N) of the joint was measured using a shear strength measuring device at 6.0 mm / min and 250°C. For example, the STR-1000 manufactured by Rhesca can be used as the shear strength measuring device.

[0396] Example The present invention will be described below through embodiments, but the present invention is not limited to the following embodiments.

[0397] <Preparation of Substrate Metal Sheets and Cover Sheets> Substrate metal sheets (A) to (G) are prepared by the following steps.

[0398] The base metal sheets (A) to (G) are preformed solders obtained by rolling using the following first metal powder, second metal powder, third metal powder (1), and third metal powder (2) as raw materials.

[0399] The particle size of the metal powder was determined using a laser diffraction / scattering particle size distribution measuring device (MT3300EXII) manufactured by Microtrac BEL, with the average particle size measured on a volume basis.

[0400] The melting points of the metal powders were determined by differential scanning calorimetry (DSC). For the first metal powder, the DSC7020 prepared by Hitachi High Technology Scientific was used for determination, and for the second and third metal powders, the DSC404-F3Pegasus prepared by NETZSCH was used for determination.

[0401] The thickness Rs of the surface layer of the third metal powder was determined using an Auger electron spectroscopy analyzer.

[0402] First metal powder Sn Sn100% by mass metal powder (Sn100% by mass powder) with a particle size of 65μm and a melting point of 232℃ Second metal powder Ni10 Fe Metal powder composed of an alloy of 90% Ni and 10% Fe (Ni-10% Fe powder), with a particle size of 12.8 μm and a melting point of 1444℃. Third metal powder (1) Ni-plated Cu As the core of the third metal powder (1), Cu 100% by mass core balls were used. The particle size of the core (i.e., the core diameter Rc) was 100 μm.

[0403] The surface of the third metal powder (1) is a Ni 100% by mass coating. The coating thickness (i.e., the surface thickness Rs) is 2 μm.

[0404] The core ball of the third metal powder (1) is formed by covering the surface of a core ball of Cu100% mass with a Ni100% mass coating. The Ni100% mass coating is formed by electroplating.

[0405] Third metal powder (2) Ni Ni100% by mass metal powder (Ni100% by mass powder) with a particle size of 100 μm Substrate metal sheet (A) Sn-40 (Ni10Fe) Mixing steps: Mix 60 parts by mass of a first metal powder and 40 parts by mass of a second metal powder to prepare a metal powder mixture.

[0406] Rolling process: Next, the prepared metal powder mixture is fed into the hopper of a twin-roll calender, the surface temperature of the calender rolls is set to 100°C, and the calendering load reaches approximately 25 kN to obtain a strip-shaped calendered material. Then, calendering is performed to obtain a strip-shaped base metal sheet (A) of a specified thickness.

[0407] Substrate metal sheet (B) Sn-70 (Ni10Fe) Except for mixing 30 parts by mass of the first metal powder and 70 parts by mass of the second metal powder to prepare a metal powder mixture, the same method as the preparation method of the substrate metal sheet (A) is used to obtain a strip-shaped substrate metal sheet (B) of a specified thickness.

[0408] Substrate metal sheet (C) Sn-20 (Ni10Fe) Except for mixing 80 parts by mass of the first metal powder and 20 parts by mass of the second metal powder to prepare a metal powder mixture, the same method as the preparation method of the substrate metal sheet (A) is used to obtain a strip-shaped substrate metal sheet (C) of a specified thickness.

[0409] Substrate metal sheet (D) Sn-10 (Ni10Fe) Except for mixing 90 parts by mass of the first metal powder and 10 parts by mass of the second metal powder to prepare a metal powder mixture, the same method as the preparation method of the substrate metal sheet (A) is used to obtain a strip-shaped substrate metal sheet (D) of a specified thickness.

[0410] Substrate metal sheet (E) Sn-3 (Ni10Fe) Except for mixing 97 parts by mass of the first metal powder and 3 parts by mass of the second metal powder to prepare a metal powder mixture, the same method as the preparation method of the substrate metal sheet (A) is used to obtain a strip-shaped substrate metal sheet (E) of a specified thickness.

[0411] Substrate metal sheet (F) Sn-5(Ni10Fe)-35 (Ni-plated Cu) Except for mixing 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) to prepare a metal powder mixture, the same method as the preparation method of the substrate metal sheet (A) is used to obtain a strip-shaped substrate metal sheet (F) of a specified thickness.

[0412] Substrate metal sheet (G) Sn-5(Ni10Fe)-35Ni Except for mixing 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) to prepare a metal powder mixture, the same method as the preparation method of the substrate metal sheet (A) is used to obtain a strip-shaped substrate metal sheet (G) of a specified thickness.

[0413] Prepare the covering sheets (X) to (Z) in the following order.

[0414] The following Sn, Sn-3Ag-0.5Cu alloy, and Sn-5Sb alloy are used as raw materials.

[0415] Sn, melting point 232℃ Sn-3Ag-0.5Cu (Ag 3% by mass, Cu 0.5% by mass, balance Sn), melting point 220℃ Sn-5Sb (5% Sb by mass, the remainder being Sn), melting point 243℃ Covering sheet (X) Sn After Sn is processed into a plate shape, it is rolled to a specified thickness and cut into a specified size to obtain a strip-shaped covering sheet (X) of specified thickness.

[0416] Covering sheet (Y) Sn-3Ag-0.5Cu Except for using Sn-3Ag-0.5Cu alloy instead of Sn, a cover sheet (Y) of the specified thickness is obtained in the same manner as the cover sheet (X).

[0417] Covering sheet (Z) Sn-5Sb Except for using Sn-5Sb alloy instead of Sn, a cover sheet (Z) of a specified thickness is obtained by the same method as that used to prepare the cover sheet (X).

[0418] <Preparation of bonding materials> The bonding materials for each example were prepared using substrate metal sheets (A) to (G) and cover sheets (X) to (Z). The thicknesses of the substrate metal layer and the cover layer in the bonding materials of each example are shown in Tables 1 to 8.

[0419] (Example A1) A cover sheet (X) is rolled onto one side of a substrate metal sheet (A) to obtain a metal sheet. Next, the resulting metal sheet is bent so that the surfaces of the substrate metal layers are in contact with each other, and then rolled again to obtain the bonding material of Example A1, in which both sides of the substrate metal layer (A) are covered by the cover layer (X). In this bonding material, the thickness of the substrate metal layer (A) is 150 μm, and the thickness of the cover layer (X) is 75 μm.

[0420] (Examples A2~A11) As shown in Table 1, bonding materials are prepared by using a base metal sheet (A) and cover sheets (X) to (Z) in such a way that the base metal layer and the cover layer reach a specified thickness. Otherwise, the bonding materials of Examples A2 to A6 and A8 to A11 are prepared in the same manner as in Example A1.

[0421] In Example A7, the bonding material is prepared in the same manner as in Example A1, except that only one side of the substrate metal sheet (A) is covered with the cover sheet (X).

[0422] (Comparative examples A1~A7) As shown in Table 2, Comparative Examples A1 to A7 were prepared in the same manner as Example A1, except that a base metal sheet (A) was used and no cover sheet was used, and the base metal layer was formed to a specified thickness.

[0423] (Examples B1~B3, C1~C4, D1~D4, E1~E4, F1~F4, G1~G4) As shown in Tables 3-8, bonding materials are prepared by using substrate metal sheets (B) to (G) and cover sheet (X) to achieve a specified thickness of the substrate metal layer and the cover layer. Otherwise, the bonding materials of each embodiment are prepared in the same manner as in Example A1.

[0424] Figure 2 shows an SEM image of a cross-section in the thickness direction of the bonding material of embodiment C1.

[0425] (Comparative examples B1~B3, C1~C4, D1~D4, E1~E2, F1~F4, G1~G4) As shown in Tables 3-8, the bonding materials of each comparative example were prepared in the same manner as in Example A1, except that the base metal sheets (B) to (G) were used and the cover sheet was not used, and the base metal layer was formed to a specified thickness.

[0426] <Evaluation> For the prepared bonding material, a solder joint is prepared as described below, and the porosity of the joint is measured.

[0427] Preparation of Solder Joints The bonding materials for each example were cut into 5mm×5mm sizes to obtain the test pieces for each example.

[0428] The test pieces for each embodiment were mounted on a 0.5 mm thick, 50 mm × 50 mm unplated Ni Cu substrate. The surface roughness of the substrate was Sa = 0.31 μm and Sz = 8.53 μm. The surface roughness was measured using a VK-X1000 laser microscope (prepared by Keyence).

[0429] A 0.5mm thick, 5mm x 5mm Cu plate is mounted on the bonding material and then welded.

[0430] Then, using a curve with a peak temperature of 250°C and a cooling rate of 2°C / sec, solder joints were fabricated in a formic acid atmosphere while being pressurized and using a reflow oven.

[0431] Evaluation of Porosity Suppression Capability. The porosity of the joint was measured as follows. The evaluation results based on these measurements are shown in Tables 1-9.

[0432] [Determination of porosity at the joint] (1) Measurement method For the prepared solder joint, the solder joint sealed with resin was ground to expose the joint cross-section, and cross-sectional SEM images were taken using an electron microscope (JEOL Ltd., JSM-7000F). In the cross-sectional SEM images, the porosity (area %) was calculated for the parts joined by the bonding material, excluding the upper and lower components, as a whole.

[0433] The calculations used the image analysis software "Scandium" manufactured by Xihua Digital Image Co., Ltd., to calculate the content of intermetallic compounds, Sn, Bi, and In at the joint (as a percentage of area), based on the contrast.

[0434] In addition, the total of the content of intermetallic compounds, Sn, Bi, In and the area percentage of each void in the joint is taken as 100 area.

[0435] (2) Criteria for judging porosity suppression ability A. Porosity is less than 20%.

[0436] B has a porosity of 20% or more but less than 25%.

[0437] The porosity is above 25%.

[0438] Evaluation of heat resistance For solder joints prepared using the bonding materials of Examples A1, A6, and Comparative Example A7, the shear strength of the solder joints was measured and the heat resistance was evaluated as described below. These test results are shown in Table 10.

[0439] [Determination of Shear Strength] For the prepared solder joints, the shear strength (N) of the joint was measured using a shear strength measuring device (Rhesca, STR-1000) at 6.0 mm / min and 250°C. Higher shear strength indicates better heat resistance of the weld joint.

[0440] [Table 1]

[0441] [Table 2]

[0442] [Table 3]

[0443] [Table 4]

[0444] [Table 5]

[0445] [Table 6]

[0446] [Table 7]

[0447] [Table 8]

[0448] [Table 9]

[0449] [Table 10]

[0450] The results shown in Tables 1-9 confirm that, compared with the comparative examples without the covering layer, the generation of voids was suppressed in each embodiment with the covering layer.

[0451] The results shown in Tables 1-9 confirm that the embodiments with a substrate metal layer / cover layer thickness ratio of 2-58 have better void suppression capabilities.

[0452] The results shown in Table 10 confirm that, in embodiments with a substrate metal layer / cover layer thickness ratio of 2 or more, the solder joint exhibits superior heat resistance compared to the comparative example with a thickness ratio of 1.

Claims

1. A bonding material having a substrate metal layer and a cover layer covering at least one side of the substrate metal layer, wherein, The substrate metal layer comprises: a first metal containing Sn and a second metal composed of an alloy containing Ni and Fe. The coating layer contains a metal with a lower melting point than the second metal. The ratio of the thickness of the substrate metal layer to the thickness of the cover layer, expressed as a substrate metal layer / cover layer ratio, is 2 or more.

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

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

4. The bonding material according to claim 1 or 2, wherein, Both sides of the substrate metal layer are covered by the cover layer.

5. The bonding material according to claim 1 or 2, wherein, In the substrate metal layer, the content of the second metal is more than 1% by mass and less than 70% by mass relative to the total mass of the first metal and the second metal. In the coating layer, the content of a metal with a melting point lower than the second metal is 10% by mass or more and 100% by mass or less relative to the total mass of the coating layer. In the coating layer, the content of the second metal is less than 15% of the total mass of the coating layer.

6. The bonding material according to claim 1 or 2, wherein, The substrate metal layer further comprises a third metal, the surface of which is entirely formed of a metal containing Ni.

7. The bonding material according to claim 6, wherein, The Ni content 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 metal forming the entire surface of the third metal. The content of the third metal is 1 to 70% of the total mass of the first metal, the second metal, and the third metal.

8. A bonding material having a substrate metal layer and a cover layer covering at least one side of the substrate metal layer, wherein, The substrate metal layer has a metallic structure comprising 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 capping layer has a metallic structure comprising a metallic phase, the metallic phase being a metal with a lower melting point than the alloy containing Ni and Fe. The ratio of the thickness of the substrate metal layer to the thickness of the cover layer, expressed as a substrate metal layer / cover layer ratio, is 2 or more.

9. The bonding material according to claim 8, wherein, The bonding material is a covering material formed by pressing at least one side of the substrate metal layer with the cover layer.

10. A solder joint formed using the bonding material according to any one of claims 1, 2, 8 and 9.

11. A method for preparing a bonding material, comprising a method for preparing a bonding material having a substrate metal layer and a cover layer covering at least one side of the substrate metal layer, wherein, The method includes the steps of pressing a cover sheet onto at least one side of a substrate metal sheet, and covering the side with the cover layer. The substrate metal sheet comprises: a first metal containing Sn and a second metal composed of an alloy containing Ni and Fe. The covering sheet contains a metal with a lower melting point than the second metal. The ratio of the thickness of the substrate metal layer to the thickness of the cover layer, expressed as a substrate metal layer / cover layer ratio, is 2 or more.

12. The method for preparing the bonding material according to claim 11, wherein, The substrate metal layer further comprises a third metal, the surface of which is entirely formed of a metal containing Ni.

13. A method for preparing a solder joint, wherein a bonding material prepared by the bonding material preparation method of claim 11 or 12 is used to form a bonding portion between objects.

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