Solder alloy, solder paste, solder ball, solder pre-form, solder joint, vehicle electronic circuit, ecu electronic circuit, vehicle electronic circuit device and ecu electronic circuit device

Description

1 / 30 Solder alloy, solder paste, solder ball, solder preform, solder joint, vehicle-mounted electronic circuit, ECU electronic circuit, vehicle-mounted electronic circuit device, and ECU electronic circuit device. TECHNICAL FIELD

[0001] The present invention relates to a solder alloy, a solder paste, a solder ball, a solder preform, a solder joint, a vehicle-mounted electronic circuit, an ECU electronic circuit, a vehicle-mounted electronic circuit device, and an ECU electronic circuit device. BACKGROUND OF THE TECHNIQUE

[0002] A vehicle is equipped with an electronic circuit in which electronic components are soldered to a printed circuit board (referred to as an “embedded electronic circuit”). Embedded electronic circuits in vehicles are used in devices that electrically control an engine, power steering, brakes, and the like, and are essential safety components for vehicle movement. In particular, an embedded electronic circuit in a vehicle called an ECU (Engine Control Unit), which is an electronic circuit that controls a vehicle via a computer to improve fuel efficiency, needs to be able to operate in a stable state without failure for a long period of time. Due to the expansion of the assembly region, such embedded electronic circuits in vehicles have come to be mounted in locations that receive various external loads, such as impact and vibration.

[0003] Since the 1980s, among the solder alloys considered for use in engine compartments, Sn-Ag based solder alloys, which are an alternative to Sn-Pb solder alloys, have been cited as an option. Sn-Ag based solder alloy is traditionally known as a highly versatile solder alloy, as evidenced by the fact that it has Petition 870260076701, dated 07 / 31 / 2026, p. 63 / 98 2 / 30 received the JIS A35 designation. However, the Sn-Ag solder alloy has been considered a basic position to replace the Sn-Pb solder alloy as a lead-free solder alloy, and further studies have been conducted.

[0004] Furthermore, when the Sn-Ag solder alloy is connected to a Cu electrode, the Cu hardly dissolves in the Sn, so the Cu diffused from the electrode and the Sn in the solder alloy form a coarse layer of CuSn intermetallic compound at the joint interface. In addition, there are several concerns regarding the solder alloy becoming brittle due to the precipitation of a large amount of Ag3Sn. Consequently, in the Sn-Ag solder alloy, a solder joint is required in which the weld joint does not break even in a severe operating environment, and several studies have been conducted to date.

[0005] Patent Document 1 studies an alloy composition in which Sb, Bi, In, Ag, and Ga are added to a Sn-Co solder alloy in order to improve the tensile strength of the solder alloy. The same document discloses a solder alloy containing Co to disperse fine CoSn and CoSn2 in an Sn matrix, thus contributing to improved tensile strength. Furthermore, the addition of an additional element, such as Sb, was studied in order to lower the melting point.

[0006] Patent Document 2 discloses a Sn-Ag-Sb-Ni-Bi-Co solder alloy that suppresses void generation and also suppresses crack generation even after a thermal cycle test. The same document describes that, when Cu is not contained, the melt viscosity can be reduced, so that void generation can be suppressed. Furthermore, the same document also reveals that, when Ni is contained, excessive diffusion of Cu is suppressed even without containing Cu, so that crack propagation is suppressed. LIST OF QUOTES PATENT DOCUMENT

[0007] Patent Document 1: Publication of Application for Petition 870260076701, dated 07 / 31 / 2026, p. 64 / 98 3 / 30 Japanese Unexamined Patent No. H06-344180 A

[0008] Patent Document 2: Publication of Unexamined Japanese Patent Application No. 2018-1179 A SUMMARY OF THE INVENTION TECHNICAL PROBLEM

[0009] As described above, in the inventions described in Patent Documents 1 and 2, the tensile strength of the solder alloy is improved, void generation is also suppressed, and thermal cycling resistance is improved. In addition, in Patent Document 1, studies were conducted to reduce the melting point.

[0010] However, these assessments, by themselves, are insufficient for a solder joint used in an embedded electronic circuit in a vehicle. For example, in an embedded electronic circuit in a vehicle, when the vehicle in which the electronic circuit is embedded travels on a rough road, stresses such as external impact or vibration are applied to the electronic circuit. Therefore, it is very important that a solder joint exhibits high shear strength so that the solder joint does not break.

[0011] Furthermore, even if a less fracture-prone weld joint is formed, the weld joint will eventually fracture when stress is continuously applied to it. It is conceivable that such continuous stress is constantly applied by exposure to an environment with sudden temperature changes. This is due to the difference in the coefficients of thermal expansion of the electrode, the intermetallic compound formed at the joint interface, and the weld body. In this case, the fracture mode representing the fractured portion should not be the joint interface. Since the joint interface is bonded to the electrode, it is not easy to relieve stress at the joint interface. However, physical and electrical loads are primarily applied at the joint interface of the weld joint. Therefore, it is considered that fracture can be suppressed by relieving stress in the weld body, which is relatively easier to deform.

[0012] However, Patent Documents 1 and 2 do not study Petition 870260076701, dated 07 / 31 / 2026, pp. 65 / 98 4 / 30 in no way does it reflect shear strength and fracture mode, making it difficult to say whether the actual operating conditions of solder joints are accurately represented. Since the solder joint electrically connects a board or similar to an electronic component or similar, fracture at the junction interface should be avoided as much as possible.

[0013] As described above, Patent Documents 1 and 2 do not in any way study shear strength and fracture mode, which are essential properties for a solder joint. A solder alloy exhibiting these properties is desired even when it does not contain Cu. However, in recent years, vehicle electrification has advanced, and the number of boards to be assembled is considered to be increasing, so it is urgent to develop a solder alloy that exhibits these properties. Furthermore, considering the thermal resistance of electronic components, it is also desirable to have a melting point similar to that of conventional solder alloys.

[0014] Therefore, an object of the present invention is to provide a solder alloy, a solder paste, a solder ball, a solder preform, a solder joint, a vehicle-embedded electronic circuit, an ECU electronic circuit, a vehicle-embedded electronic circuit device, and an ECU electronic circuit device, each of which has a low melting point, high shear strength, and a suitable fracture mode. SOLUTION TO THE PROBLEM

[0015] The present inventors re-examined the solder alloys disclosed in Patent Documents 1 and 2. Among the solder alloys disclosed in both documents, the Sn-Ag-In-Sb-Co-Ga solder alloy of Example 5 in Patent Document 1, the Sn-Ag-In-Sb-Co-Ni-Bi solder alloy of Example 19 in Patent Document 2, and the Sn-Ag-Sb-CoFe-Ni-Bi solder alloy of Example 24 in the same document all exhibit shear strength substantially equal to that of conventional solder alloys, and Petition 870260076701, dated 07 / 31 / 2026, p. 66 / 98 5 / 30 revealed that there is still room for improvement.

[0016] These solder alloys do not have an alloy composition designed to improve shear strength. It should be understood that, in solder alloys, when the content or similar of even a single constituent component is different, the overall properties are generally different, and therefore the complete combination of alloying elements with predetermined contents is technically evaluated as an integrated whole.

[0017] Therefore, the present inventors conducted detailed studies on improving shear strength and fracture mode while suppressing the increase in melting point. Here, Patent Document 1 describes that the melting point can be reduced by adding Ag, In, Sb, and Ga to the Sn-Co solder alloy. However, since the melting point varies considerably depending on the levels of these elements, the composition described in Example 5 of Patent Document 1 is not always adequate.

[0018] Furthermore, Patent Document 1 reveals that Co is added for the purpose of improving tensile strength. However, the improvement of shear strength was not studied at all. Moreover, when the tensile strength of the weld alloy is improved beyond what is necessary, the fracture mode becomes the joint interface. Therefore, it is inferred that the addition of Co is not preferable in the Sn-Ag-In-Sb-Co-Ga weld alloy.

[0019] Patent Document 2 describes that void generation can be suppressed when Ni and Co contents are within a predetermined range. As described above, considering the description in Patent Document 2, Co can have an effect when coexisting with Ni. Therefore, according to the finding that the alloy composition of Patent Document 1 exhibits low shear strength and an inadequate fracture mode, it is inferred that the addition of Ni is also not preferable in Patent Document 2.

[0020] In addition, Patent Document 2 describes that, Petition 870260076701, dated 07 / 31 / 2026, p. 67 / 98 6 / 30 when the Bi content is equal to or less than a predetermined amount, thermal shock resistance can be maintained. However, in Patent Document 2, since Bi dissolves in Sn at approximately 3%, the tensile strength of the solder alloy increases due to the solid solution hardening of Sn, and the fracture mode becomes the joint interface.

[0021] Therefore, considering the above findings, the present inventors focused on a Sn-Ag-In-Sb solder alloy obtained by removing Ni, Co, and Bi from the elements to be added to Sn in Patent Documents 1 and 2. And, in order to improve the shear strength of the solder alloy and to make the fracture mode the body of the weld, the present inventors conducted detailed studies on the selection of additional additive elements and on the Ag, In, and Sb contents.

[0022] First, in order to make the fracture mode suitable, it is necessary to suppress the growth of the intermetallic compound at the junction interface in the weld alloy that does not contain Cu and Ni. The intermetallic compound grows by diffusion of Cu from the electrode into the weld alloy. Here, the intermetallic compound is mainly composed of a compound of Sn and Cu. And, when the layer of intermetallic compound present at the interface between the weld alloy and the electrode is coarse, the fracture mode tends to become unsuitable.

[0023] Therefore, focusing on the fact that the interface is modified by the presence of Fe, the content of the additive element was studied in detail for the Sn-Ag-In-Sb-Fe solder alloy. As a result, it was found that shear strength can be improved and the fracture mode can be optimized only when the content of the additive element is within a predetermined range. The present invention, concluded from these findings, is as follows.

[0024] (0) A solder alloy consisting, in % by mass, of Ag: 2.0 to 3.6%, In: 1.0 to 5.0%, Sb: 3.0 to 5.0%, Fe: 0.0010 to 0.0300%, and Co: 0.0000% or more and 0.0500% or less, with the remainder being Sn.

[0025] (1) A solder alloy having an alloy composition Petition 870260076701, dated 07 / 31 / 2026, pages 68 / 98 7 / 30 consisting, in % by mass, of Ag: 2.0 to 3.6%, In: 1.0 to 5.0%, Sb: 3.0 to 5.0%, Fe: 0.0010 to 0.0300%, and Co: 0% or more and 0.050% or less, the remainder being Sn.

[0026] (2) Alloy composition (welding alloy) according to (0) or (1) above, wherein, in % by mass, the alloy composition additionally contains at least one of Zr, Ge, Ga, P, As, Pb, Zn, Mg, Cr, Ti, Mo, Pt, Pd, Au, Al and Si: 0.100% or less in total.

[0027] (3) The alloy composition (weld alloy) according to any one of (0) to (2) above, wherein the alloy composition satisfies the following relations (1) and (2): the. 0.36 ^ AgxInxSbxFe ^ 1.19(1) b. 47 ^ (InxSb) / (AgxFe) ^ 319(2) c. where Ag, In, Sb and Fe in Relations (1) and (2) each represent the respective content in % by mass in the solder alloy.

[0028] (4) A solder paste having a desoldering powder consisting of the solder alloy according to any one of (0) to (2).

[0029] (5) A solder ball consisting of solder alloy according to any one of (0) to (2) above.

[0030] (6) A weld preform consisting of the weld alloy according to any one of (0) to (2) above.

[0031] (7) A weld joint having the weld alloy in accordance with any one of (0) to (2) above.

[0032] (8) An electronic circuit embedded in a vehicle having the solder alloy in accordance with any one of (0) to (2) above.

[0033] (9) An ECU electronic circuit having the solder alloy in accordance with any one of (0) to (2) above.

[0034] (10) A vehicle-mounted electronic circuit device comprising the vehicle-mounted electronic circuit according to (8) above.

[0035] (11) An ECU electronic circuit device Petition 870260076701, dated 07 / 31 / 2026, page 69 / 98 8 / 30 comprising the ECU electronic circuit according to (9) above. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows an optical microscope photograph of a sample after shear strength measurement; FIG. 1(a) shows Example 14, FIG. 1(b) shows Example 2, and FIG. 1(c) shows Comparative Example 3. DESCRIPTION OF THE MODALITIES

[0037] The present invention is described in more detail below. In this description, “%” relating to the composition of the solder alloy refers to “% by mass”, unless otherwise specified. 1. Solder Alloy (1) Ag: 2.0 to 3.6%

[0038] Ag contributes to improved shear strength, to optimized fracture mode through Ag3Sn precipitation, and to lower melting point. When the Ag content is less than 2.0%, the amount of compound precipitation is low, and shear strength decreases. In terms of the lower limit, the Ag content is 2.0% or more, preferably 2.5% or more, more preferably 2.7% or more, and even more preferably 3.0% or more.

[0039] On the other hand, when the Ag content is greater than 3.6%, since a large amount of Ag3Sn is precipitated due to the formation of a hypereutectic condition and the weld body strength is excessively increased, the fracture mode becomes the joint interface. Furthermore, the shear strength decreases due to the fracture mode becoming the joint interface. In terms of the upper limit, the Ag content is 3.6% or less, preferably 3.5% or less, and most preferably 3.4% or less. (2) In: 1.0 to 5.0%

[0040] In contributes to improved shear strength and optimized fracture mode. When the In content is Petition 870260076701, dated 07 / 31 / 2026, p. 70 / 98 9 / 30 less than 1.0%, the spreading effect due to wetting is also insufficient due to reduced wettability, and the solid solution hardening effect is insufficient, so the shear strength decreases and the fracture mode becomes inadequate. In terms of the lower limit, the In content is 1.0% or more, preferably 1.5% or more, more preferably 2.0% or more, even more preferably 2.5% or more, and particularly preferably 3.0% or more.

[0041] On the other hand, when the In content is greater than 5.0%, a large amount of the compound is precipitated and the melting point increases. In addition, the strength of the weld body increases, raising concerns about fracture at the joint interface or in the component. In terms of the upper limit, the In content is 5.0% or less, preferably 4.5% or less, more preferably 4.0% or less, and even more preferably 3.5% or less. (3) Sb: 3.0 to 5.0%

[0042] Sb contributes to improved shear strength and optimized fracture mode. When the Sb content is less than 3.0%, solid solution hardening in Sn and precipitation hardening of the Sn-Sb compound are insufficient, so shear strength decreases. In terms of the lower limit, the Sb content is 3.0% or more, preferably 3.5% or more, more preferably 3.6% or more, even more preferably 3.8% or more, particularly preferably 3.9% or more, and most preferably 4.0% or more.

[0043] On the other hand, when the Sb content is greater than 5.0%, coarse SnSb compounds are formed, so that the shear strength decreases. In addition, wettability deteriorates and the fracture mode becomes the junction interface or component fracture, making it unsuitable. In terms of the upper limit, the Sb content is 5.0% or less, preferably 4.8% or less, more preferably 4.6% or less, even more preferably 4.5% or less, particularly preferably 4.3%. Petition 870260076701, dated 07 / 31 / 2026, p. 71 / 98 10 / 30 or less, and most preferably 4.1% or less. (4) Fe: 0.0010 to 0.0300%

[0044] Fe contributes to improved shear strength and optimized fracture mode. When the Fe content is less than 0.0010%, the strengthening effect of the interface through modification of the intermetallic compound layer formed at the interface is insufficient, and therefore the shear strength decreases and the fracture mode becomes the junction interface, making it unsuitable. In terms of the lower limit, the Fe content is 0.0010% or more, preferably 0.0050% or more, more preferably 0.0100% or more, even more preferably 0.0150% or more, and particularly preferably 0.0200% or more.

[0045] On the other hand, when the Fe content is greater than 0.0300%, a compound of Sn and Fe is precipitated, and the strength of the weld body is excessively improved, so there is also a risk of fracture at the joint interface. In terms of the upper limit, the Fe content is 0.0300% or less, preferably 0.0270% or less, and more preferably 0.0250% or less. (5) Co: 0.0000% or more and 0.0500% or less

[0046] Cobalt (Co) is an optional element that contributes to suppressing an increase in the melting point, improving shear strength, and optimizing the fracture mode. In conventional solder alloys, it was considered preferable not to contain Cobalt from the point of view of improving shear strength and optimizing the fracture mode. However, when Cobalt is added, high shear strength is maintained and the fracture mode remains the weld body. In Sn-Ag-In-Sb-based solder alloys, with respect to Cobalt, CoSn and similar elements are considered to be finely dispersed. However, the structure of the Sn alloy is not refined to the point of becoming sufficiently fine. In this alloy system, since the structure of the Sn alloy becomes fine due to Fe, it is assumed that when the fine structure of CoSn and similar elements is dispersed, the entire alloy structure becomes even finer. Petition 870260076701, dated 07 / 31 / 2026, page 72 / 98 11 / 30 Therefore, in the solder alloy according to the present invention, Co can exert a synergistic effect in the presence of Fe.

[0047] Furthermore, in the solder alloy according to the present invention, Co is an optional element, and therefore, even when Co is not present, high shear strength and optimization of the fracture mode can be maintained. In terms of the lower limit, the Co content is 0.0000% or more, preferably greater than 0.0000%, more preferably 0.0010% or more, even more preferably 0.0030% or more, particularly preferably 0.0060% or more, and most preferably 0.0080% or more.

[0048] On the other hand, when the Co content is greater than 0.0500%, a Sn and Co compound is precipitated and the weld body strength is greatly increased, causing the fracture mode to become the joint interface. In addition, the melting point increases considerably due to the precipitation of a large amount of the compound, and wettability deteriorates, so that shear strength decreases. In terms of the upper limit, the Co content is 0.0500% or less, preferably 0.0300% or less, and more preferably 0.0100% or less. (6) Remaining: Sn

[0049] The remainder of the solder alloy according to the present invention is Sn. In addition to the elements described above, unavoidable impurities may be present. Even when unavoidable impurities are present, this does not affect the effects described above. It should be noted that, in the present invention, when the Sn-Ag-In-Sb-Fe solder alloy contains Ni, the SnNi compound is precipitated. As the SnNi compound precipitates using the intermetallic compound formed at the interface as a core, the intermetallic compound layer formed at the interface becomes thick. As a result, the shear strength decreases. Therefore, in the present invention, it is preferable not to contain Ni. Furthermore, when Bi coexists with In, a low-melting-point Sn-In-Bi phase is formed. Considering creep deformation, the low-melting-point phase Petition 870260076701, dated 07 / 31 / 2026, p. 73 / 98 12 / 30 of the melting point exhibits such a low melting point that an environment at room temperature constitutes a high-temperature environment, thus becoming susceptible to creep deformation, and the shear strength is reduced. Therefore, in the present invention, it is preferable not to contain Bi. (7) At least one of Zr, Ge, Ga, P, As, Pb, Zn, Mg, Cr, Ti, Mo, Pt, Pd, Au, Al and Si: 0.100% or less in total

[0050] The solder alloy according to the present invention may contain at least one of Zr, Ge, Ga, P, As, Pb, Zn, Mg, Cr, Ti, Mo, Pt, Pd, Au, Al and Si, in the range of 0.100% or less in total, as an optional element, insofar as the effect of the present invention is not impaired. Preferably, the total amount is 0.080% or less. In terms of the lower limit, the content may be 0.0001% or more, or it may be 0.001% or more, although it is not particularly limited. (8) Relations (1) and (2): 0.36 ^ AgxInxSbxFe ^ 1.19 (1) ^ (InxSb) / (AgxFe) ^ 319 (2) where Ag, In, Sb and Fe in Ratios (1) and (2) each represent the respective content in % by mass in the solder alloy.

[0051] Ratio (1) is a ratio in which the balance of additive elements of the solder alloy according to the present invention is taken into consideration. The solder alloy according to the present invention can exhibit a low melting point, high shear strength, and a suitable fracture mode through a synergistic effect of each constituent element. Therefore, when the balance of all constituent elements, except Sn, is further optimized, all the effects of the present invention can be further improved. In Ratio (1), the contents of Ag, In, and Sb are approximately 10 to 100 times the content of Fe. However, their contributions to the solder alloy are considered to be practically at the same level. Therefore, in order to further improve the low melting point, high shear strength, and suitable fracture mode in the present invention, simultaneously, with a Petition 870260076701, dated 07 / 31 / 2026, p. 74 / 98 13 / 30 single composition, a balanced content is preferable.

[0052] Relationship (2) is a relationship in which, between the additive elements, equilibrium is considered in the In and Sb group, in which shear strength is improved until fracture of the component occurs when the content is above the upper limit, and equilibrium in the Ag and Fe group, which remains at the interface fracture, also considering the equilibrium between both groups. When Relationship (2) is satisfied, the fracture mode can become even more suitable, depending on the alloy composition.

[0053] In terms of the lower bound of Relation (1), this is preferably 0.36 or more, more preferably 0.39 or more, even more preferably 0.42 or more, even more preferably 0.43 or more, particularly preferably 0.44 or more, and most preferably 0.52 or more, 0.53 or more, 0.60 or more, 0.656 or more, 0.66 or more, 0.70 or more, 0.75 or more, 0.78 or more, 0.79 or more, 0.84 or more, 0.87 or more, 0.88 or more. In terms of the upper bound of the Ratio (1), this is preferably 1.19 or less, more preferably 1.18 or less, even more preferably 1.09 or less, even more preferably 1.08 or less, particularly preferably 1.05 or less, and most preferably 1.02 or less, 0.91 or less, 0.92 or less, 0.90 or less.

[0054] In terms of the lower bound of Relation (2), this is preferably 47 or more, more preferably 51 or more, even more preferably 57 or more, even more preferably 68 or more, particularly preferably 69 or more, and most preferably 85 or more, 86 or more, 91 or more, 102 or more, 103 or more, 114 or more, 120 or more, 133 or more, 137 or more, 141 or more, 142 or more, 143 or more, 154 or more, or 160 or more. In terms of the upper bound of Relation (2), this is preferably 319 or less, more preferably 286 or less, even more preferably 285 or less, even more preferably 267 or less, particularly preferably 266 or less, and most preferably 257 or less, 240 or less, 229 or less, 228 or less, Petition 870260076701, dated 07 / 31 / 2026, pp. 75 / 98 14 / 30 213 or less, 206 or less, 205 or less, 200 or less, 192 or less, 183 or less, 182 or less, 171 or less.

[0055] In the calculation of Ratios (1) and (2), the numerical values ​​indicated are used as the actually measured values ​​of the alloy composition shown in Tables 1 to 3 below. That is, in the calculation of Ratios (1) and (2), all digits less than the number of significant figures in the actually measured values ​​shown in Tables 1 to 3 below are considered as 0. For example, when the Fe content is “0.0250” % by mass as the actually measured value, the Fe content used for the calculation of Ratios (1) and (2) does not have a range of 0.02495 to 0.02504%, but is treated as “0.025000...”. In Ratio (1), the number is calculated to three decimal places, and the digit in the third decimal place is rounded to obtain a number with two decimal places. In Relation (2), the number is calculated to the first decimal place, and the digit in the first decimal place is rounded to the nearest whole number.

[0056] It should be noted that when the Ratios (1) and (2) are also calculated from the alloy compositions specifically disclosed in other documents and in the patent documents cited in this specification, the same calculation method is applied.

[0057] As described above, in the alloy, all constituent elements do not function individually, but all constituent elements form a single object as a whole, so that it is rare for all excellent effects to be exerted simultaneously by only one element. Therefore, as described above, in order to present more excellent properties within the range of the ideal content of each constituent element, it is necessary to study the constituent elements as a whole. In the solder alloy according to the present invention, it is preferable to satisfy the Relationships (1) and (2) in order to simultaneously achieve low melting point, high shear strength, and suitable fracture mode, with a single composition and at a higher level. Petition 870260076701, dated 07 / 31 / 2026, pp. 76 / 98 15 / 30

[0058] It should be noted that, in the Examples described below, “Excellent” indicates that the example is particularly preferable in practical use compared to “Good”. Since “Good” is a more preferable result than the prior art, when the other evaluation results are also excellent, these fall within the scope of the present invention and are treated as examples. Since “Poor” is an insufficient result in the present invention, this is outside the scope of the present invention and is treated as a comparative example. 2. Solder Paste

[0059] A soldering paste according to the present invention is a mixture of a soldering powder consisting of the alloy composition described above and a flux. A flux to be used in the present invention is not particularly limited, provided that soldering by a common method is possible. Therefore, a flux suitably formulated with rosin, an organic acid, an activator, a thixotropic agent, as well as a solvent, all commonly used, may be employed. The mixing proportions of the metal powder component and the flux component in the present invention are preferably: metal powder component: 70 to 90% by mass, flux component: 10 to 30% by mass, although they are not particularly limited. 3. Welding Sphere

[0060] The solder alloy according to the present invention can be used as a solder ball. In the case of using the solder alloy according to the present invention as a solder ball, a solder ball can be manufactured using a drop method, which is a common method in the art. Furthermore, a weld joint can be manufactured by processing a solder ball using a common method in the art, such as mounting and joining a solder ball onto a flux-coated electrode. The particle size of the solder ball is preferably 1 μm or more, more preferably 10 μm or more, even more preferably 20 μm or more, and particularly preferably 30 μm or more. Petition 870260076701, dated 07 / 31 / 2026, pp. 77 / 98 16 / 30 μm or more. In terms of the upper limit, the particle size of the solder ball is preferably 3,000 μm or less, more preferably 1,000 μm or less, even more preferably 800 μm or less, and particularly preferably 600 μm or less. 4. Welding Preform

[0061] The solder alloy according to the present invention can be used as a solder preform. Examples of preform shapes include a washer, a ring, a pad, a disc, a ribbon, and a wire. 5. Welding Joint

[0062] A solder joint according to the present invention is preferably used to join at least two or more members to be joined. The members to be joined are not particularly limited, provided they are electrically connected by means of the solder joint according to the present invention, and examples of these include elements, plates, electronic components, printed circuit boards, insulating plates, heat sinks, lead frames, semiconductors using electrode terminals and the like, power modules, inverter products and the like.

[0063] The joining method using the solder alloy according to the present invention can be carried out according to a conventional method, using, for example, a reflow method. The melting temperature of the solder alloy, in the case of reflow welding, can be approximately 20°C higher than the liquidus line temperature. Furthermore, when the joining is carried out using the solder alloy according to the present invention, the alloy structure can be further refined by considering the cooling rate during solidification. For example, the solder joint is cooled at a cooling rate of 2 to 3°C / s or more. The other joining conditions can be suitably adjusted according to the composition of the solder alloy. 6. Vehicle-Embedded Electronic Circuit, ECU Electronic Circuit, Vehicle-Embedded Electronic Circuit Device. Petition 870260076701, dated 07 / 31 / 2026, pp. 78 / 98 17 / 30 ECU Electronic Circuit Device

[0064] As evident from the description above, the solder alloy according to the present invention exhibits a suppressed increase in melting point and a suitable fracture mode. Therefore, even when used in vehicles exposed to harsh environments, i.e., in vehicle-mounted devices, the fracture of the solder joints is suppressed without variation. Consequently, since the solder alloy exhibits such particularly remarkable properties, it is found that the solder alloy according to the present invention is particularly suitable for soldering an electronic circuit mounted in a vehicle.

[0065] As described above, the solder alloy according to the present invention is used, more specifically, for soldering an electronic circuit embedded in a vehicle or for soldering an ECU electronic circuit, exhibiting excellent results.

[0066] An “electronic circuit” is a system that performs a target function as a whole, through a combination of electronic engineering of a plurality of electronic components, each with a function.

[0067] Examples of the electronic component that constitutes such an electronic circuit include a chip resistor, a multi-resistor component, QFP, QFN, a power transistor, a diode, a capacitor, etc. The electronic circuit incorporating these electronic components is arranged on a board and constitutes an electronic circuit device.

[0068] In the present invention, a board constituting such an electronic circuit device, for example, a printed circuit board, is not particularly limited. The material thereof is also not particularly limited, but a heat-resistant plastic board is exemplified (for example, FR-4, with high Tg and low CTE). The printed circuit board is preferably a printed circuit board in which the surface of the Cu ground is treated with an organic substance (OSP: Organic Surface Protection) such as an amine. Petition 870260076701, dated 07 / 31 / 2026, p. 79 / 98 18 / 30 or imidazole. 7. Others

[0069] As with the solder alloy according to the present invention, by using a low α-ray emission material as raw material, a low α-ray emission alloy can be produced. Such a low α-ray emission alloy can prevent slight error when used in the formation of solder protrusions around a memory. Examples

[0070] The present invention will be described based on the following examples; however, the present invention is not limited to the following examples.

[0071] In order to verify the effect of the present invention, the welding alloys described in Tables 1 to 3 were used to evaluate (1) melting point, (2) shear strength, (3) fracture mode. (1) Melting Point

[0072] For the solder alloys shown in Tables 1 to 3, each temperature was determined from the DSC curve. The DSC curve was obtained with a DSC (model number: 6200) manufactured by Seiko Instruments Inc., raising the temperature at 5°C / min in the atmosphere. The liquidus line temperature was determined from the obtained DSC curve and considered as the melting point. When the melting point is 232°C or lower, reflow soldering can be performed at the same temperature as in the previous technique. When the melting point is higher than 232°C, conventional reflow soldering cannot be performed, since the melting point is too high. (2) Shear Strength (2-1) Sample Fabrication

[0073] The solder alloys shown in Tables 1 to 3 were melted to prepare solder plates (diameter: 1 mm, thickness: 0.15 mm). Using the reflow furnace (SNR-615: manufactured by SENJU METAL INDUSTRY CO., LTD.), a chip resistor was soldered to the Cu-OSP electrode of Petition 870260076701, dated 07 / 31 / 2026, pages 80 / 98 19 / 30 FR-4 board. The 3216CR (CR32-114JV: manufactured by HOKURIKU ELECTRIC INDUSTRY CO., LTD.) was used as the chip resistor. The reflow profile was maintained at 220°C or higher for 40 seconds, and the peak temperature was 245°C in a nitrogen atmosphere. (2-2) Evaluation of Shear Strength

[0074] The sample thus prepared had its shear strength measured using the shear tester (STR-1000: manufactured by RHESCA) at a shear rate of 6 mm / min. When the shear strength was 84.0 N or more, it was determined as “Excellent”. When the shear strength was 70.0 N or more and less than 84.0 N, it was determined as “Good”. When the shear strength was less than 70.0 N, it was determined as “Poor”. (3) Fracture Mode

[0075] The sample evaluated in “(2) Shear Strength” above was observed for fracture mode using an optical microscope (VHX-5000: manufactured by KEYENCE Corporation). When the sample fractured in the weld body, it was determined to be “Excellent”. When the sample fractured in the weld body and in the intermetallic compound (IMC) at the junction interface, it was determined to be “Good”. When the sample fractured in the intermetallic compound at the junction interface, it was determined to be “Poor”.

[0076] The evaluation results are shown in Tables 1 to 3. Petition 870260076701, dated 07 / 31 / 2026, pp. 81 / 98 20 / 30

[0077] [Table 1] Alloy Composition (in % by mass) Ratio (1) Ratio (2) Melting Point (°C) Shear Strength (N) Fracture Mode Sn Ag In Sb Fe Co Ge P Ga Zr As Pb Zn Mg Cr Ti Mo Pt Pd Au Al Si Ni Bi Ex.1 Res. 3.5 1.0 3.0 0.025 0.26 34 222 Good Good Ex.2 Res. 3.5 1.0 4.0 0.025 0.35 46 222 Good Good Ex.3 Res. 3.5 1.0 5.0 0.025 0.44 57 222 Excellent Excellent Ex.4 Res. 3.5 1.5 3.0 0.025 0.39 51 220 Excellent Excellent Ex.5 Res. 3.5 1.5 4.0 0.025 0.53 69 220 Excellent Excellent Ex.6 Res. 3.5 1.5 5.0 0.025 0.66 86 221 Excellent Excellent Ex.7 Res. 3.5 2.0 3.0 0.025 0.53 69 219 Excellent Excellent Ex.8 Res. 3.5 2.0 4.0 0.025 0.70 91 219 Excellent Excellent Ex.9 Res. 3.5 2.0 5.0 0.025 0.88 114 220 Excellent Excellent Ex.10 Res. 3.5 2.5 3.0 0.025 0.66 86 218 Excellent Excellent Ex.11 Res. 3.5 2.5 4.0 0.025 0.88 114 218 Excellent Excellent Ex.12 Res. 3.5 2.5 5.0 0.025 1.09 143 218 Excellent Excellent Ex.13 Res. 3.5 3.0 3.0 0.025 0.79 103 216 Excellent Excellent Ex.14 Res.3.5 3.0 4.0 0.025 1.05 137 217 Excellent Excellent Ex.15 Res. 3.5 3.0 5.0 0.025 1.31 171 217 Excellent Good Ex.16 Res. 3.5 3.5 3.0 0.025 0.92 120 215 Excellent Excellent. Ex. = Example Petition 870260076701, dated 07 / 31 / 2026, p. 82 / 98 21 / 30 Table 1 (continued) Alloy Composition (in % by mass) Ratio (1) Ratio (2) Melting Point (°C) Shear Strength (N) Fracture Mode Sn Ag In Sb Fe Co Ge P Ga Zr As Pb Zn Mg Cr Ti Mo Pt Pd Au Al Si Ni Bi Ex.17 Res. 3.5 3.5 4.0 0.025 1.23 160 215 Excellent Good Ex.18 Res. 3.5 3.5 5.0 0.025 1.53 200 221 Excellent Good Ex.19 Res. 3.5 4.0 3.0 0.025 1.05 137 214 Excellent Excellent Ex.20 Res. 3.5 4.0 4.0 0.025 1.40 183 214 Excellent Good Ex.21 Res. 3.5 4.0 5.0 0.025 1.75 229 214 Excellent Good Ex.22 Res. 3.5 4.5 3.0 0.025 1.18 154 213 Excellent Excellent Ex.23 Res. 3.5 4.5 4.0 0.025 1.58 206 213 Excellent Good Ex.24 Res. 3.5 4.5 5.0 0.025 1.97 257 213 Excellent Good Ex.25 Res. 3.5 5.0 3.0 0.025 1.31 171 216 Excellent Good Ex.26 Res. 3.5 5.0 4.0 0.025 1.75 229 216 Excellent Good Ex.27 Res. 3.5 5.0 5.0 0.025 2.19 286 216 Excellent Good Ex.28 Res. 2.0 3.0 4.0 0.025 0.60 240 222 Excellent Excellent Ex.29 Res. 2.5 3.0 4.0 0.025 0.75 192 220 Excellent Excellent Ex.30 Res.3.0 3.0 4.0 0.025 0.90 160 218 Excellent Excellent Ex.31 Res. 3.6 3.0 4.0 0.025 1.08 133 216 Excellent Excellent Ex.32 Res. 3.0 4.0 4.0 0.025 1.20 213 218 Excellent Good. Ex. = Example Petition 870260076701, dated 07 / 31 / 2026, p. 83 / 98 22 / 30 Table 1 (continued) Alloy Composition (in % by mass) Ratio (1) Ratio (2) Melting Point (°C) Shear Strength (N) Fracture Mode Sn Ag In Sb Fe Co Ge P Ga Zr As Pb Zn Mg Cr Ti Mo Pt Pd Au Al Si Ni Bi Ex.33 Res. 3.0 4.5 4.0 0.025 1.35 240 223 Excellent Good Ex.34 Res. 3.0 5.0 4.0 0.025 1.50 267 226 Excellent Good Ex.35 Res. 3.5 1.0 3.0 0.025 0.0080 0.26 34 222 Good Excellent Ex.36 Res. 3.5 1.0 4.0 0.025 0.0080 0.35 46 222 Good Excellent Ex.37 Res. 3.5 1.0 5.0 0.025 0.0080 0.44 57 223 Excellent Excellent Ex.38 Res. 3.5 1.5 3.0 0.025 0.0080 0.39 51 220 Excellent Excellent Ex.39 Res. 3.5 1.5 4.0 0.025 0.0080 0.53 69 221 Excellent Excellent Ex.40 Res. 3.5 1.5 5.0 0.025 0.0080 0.66 86 221 Excellent Excellent Ex.41 Res. 3.5 2.0 3.0 0.025 0.0080 0.53 69 219 Excellent Excellent Ex.42 Res. 3.5 2.0 4.0 0.025 0.0080 0.70 91 219 Excellent Excellent Ex.43 Res. 3.5 2.0 5.0 0.025 0.0080 0.88 114 220 Excellent Excellent Ex.44 Res. 3.5 2.5 3.0 0.025 0.0080 0.66 86 222 Excellent Excellent Ex.45 Res.3.5 2.5 4.0 0.025 0.0080 0.88 114 220 Excellent Excellent Ex.46 Res. 3.5 2.5 5.0 0.025 0.0080 1.09 143 219 Excellent Excellent Ex.47 Res. 3.5 3.0 3.0 0.025 0.0080 0.79 103 217 Excellent Excellent Ex.48 Res. 3.5 3.0 4.0 0.025 0.0080 1.05 137 217 Excellent Excellent. Ex. = Example Petition 870260076701, dated 07 / 31 / 2026, p. 84 / 98 23 / 30 Table 1 (continued) Alloy Composition (in % by mass) Ratio (1) Ratio (2) Melting Point (°C) Shear Strength (N) Fracture Mode Sn Ag In Sb Fe Co Ge P Ga Zr As Pb Zn Mg Cr Ti Mo Pt Pd Au Al Si Ni Bi Ex.49 Res. 3.5 3.0 5.0 0.025 0.0080 1.31 171 220 Excellent Good Ex.50 Res. 3.5 3.5 3.0 0.025 0.0080 0.92 120 225 Excellent Excellent Ex.51 Res. 3.5 3.5 4.0 0.025 0.0080 1.23 160 223 Excellent Good Ex.52 Res. 3.5 3.5 5.0 0.025 0.0080 1.53 200 221 Excellent Good Ex.53 Res. 3.5 3.5 5.0 0.025 0.0080 1.53 200 215 Excellent Good Ex.54 Res. 3.5 4.0 3.0 0.025 0.0080 1.05 137 214 Excellent Excellent Ex.55 Res. 3.5 4.0 4.0 0.025 0.0080 1.40 183 214 Excellent Good Ex. = Example Petition 870260076701, dated 07 / 31 / 2026, pages 85 / 98 24 / 30

[0078] [Table 2] Alloy Composition (in % by mass) Ratio (1) Ratio (2) Melting Point (°C) Shear Strength (N) Fracture Mode Sn Ag In Sb Fe Co Ge P Ga Zr As Pb Zn Mg Cr Ti Mo Pt Pd Au Al Si Ni Bi Ex.56 Res. 3.5 4.0 5.0 0.025 0.0080 1.75 229 214 Excellent Good Ex.57 Res. 3.5 4.5 3.0 0.025 0.0080 1.18 154 213 Excellent Excellent Ex.58 Res. 3.5 4.5 4.0 0.025 0.0080 1.58 206 213 Excellent Good Ex.59 Res. 3.5 4.5 5.0 0.025 0.0080 1.97 257 213 Excellent Good Ex.60 Res. 3.5 5.0 3.0 0.025 0.0080 1.31 171 216 Excellent Good Ex.61 Res. 3.5 5.0 4.0 0.025 0.0080 1.75 229 216 Excellent Good Ex.62 Res. 3.5 5.0 5.0 0.025 0.0080 2.19 286 216 Excellent Good Ex.63 Res. 3.5 3.0 4.0 0.001 0.0080 0.04 3429 217 Excellent Good Ex.64 Res. 3.5 3.0 4.0 0.005 0.0080 0.21 686 217 Excellent Good Ex.65 Res. 3.5 3.0 4.0 0.010 0.0080 0.42 343 217 Excellent Good Ex.66 Res. 3.5 3.0 4.0 0.020 0.0080 0.84 171 217 Excellent Excellent Ex.67 Res. 3.5 3.0 4.0 0.030 0.0080 1.26 114 217 Excellent Good Ex.68 Res.3.5 3.0 4.0 0.025 0.0010 1.05 137 217 Excellent Excellent Ex.69 Res. 3.5 3.0 4.0 0.025 0.0030 1.05 137 217 Excellent Excellent Ex.70 Res. 3.5 3.0 4.0 0.025 0.0060 1.05 137 217 Excellent Excellent Ex.71 Res. 3.4 3.0 4.0 0.025 0.0100 1.02 141 217 Excellent Excellent. Ex. = Example Petition 870260076701, dated 07 / 31 / 2026, pp. 86 / 98 25 / 30 Table 2 (continued) Alloy Composition (in % by mass) Ratio (1) Ratio (2) Melting Point (°C) Shear Strength (N) Fracture Mode Sn Ag In Sb Fe Co Ge P Ga Zr As Pb Zn Mg Cr Ti Mo Pt Pd Au Al Si Ni Bi Ex.72 Res. 3.4 3.0 4.0 0.025 0.0300 1.02 141 217 Excellent Excellent Ex.73 Res. 3.4 3.0 4.0 0.025 0.0500 1.02 141 217 Excellent Excellent Ex.74 Res. 3.0 4.0 4.0 0.025 0.0080 1.20 213 221 Excellent Good Ex.75 Res. 3.0 4.5 4.0 0.025 0.0080 1.35 240 223 Excellent Good Ex.76 Res. 3.0 5.0 4.0 0.025 0.0080 1.50 267 226 Excellent Good Ex.77 Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent Ex.78 Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent Ex.79 Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent Ex.80 Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent Ex.81 Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent Ex.82 Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent Ex.83 Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent Ex.84 Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent Ex.85 Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent Ex.86 Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent Ex.87 Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent. Ex. = Example Petition 870260076701, dated 07 / 31 / 2026, pp. 87 / 98 26 / 30 Table 2 (continued) Alloy Composition (in % by mass) Ratio (1) Ratio (2) Melting Point (°C) Shear Strength (N) Fracture Mode Sn Ag In Sb Fe Co Ge P Ga Zr As Pb Zn Mg Cr Ti Mo Pt Pd Au Al Si Ni Bi Ex.88 Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent Ex.89 Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent Ex.90 Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent Ex.91 ​​Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent Ex.92 Res. 3.0 3.0 4.0 0.025 0.01 0.90 160 217 Excellent Excellent Ex.93 Res. 3.0 3.0 4.0 0.025 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.90 160 218 Excellent Excellent Ex.94 Res. 3.0 3.0 4.0 0.025 0.0080 0.01 0.90 160 217 Excellent Excellent Ex.95 Res. 3.0 3.0 4.0 0.025 0.0080 0.01 0.90 160 217 Excellent Excellent Ex.96 Res. 3.0 3.0 4.0 0.025 0.0080 0.01 0.90 160 217 Excellent Excellent Ex.97 Res. 3.0 3.0 4.0 0.025 0.0080 0.01 0.90 160 217 Excellent Excellent Ex.98 Res.3.0 3.0 4.0 0.025 0.0080 0.01 0.90 160 217 Excellent Excellent Ex.99 Res. 3.0 3.0 4.0 0.025 0.0080 0.01 0.90 160 217 Excellent Excellent Ex.100 Res. 3.0 3.0 4.0 0.025 0.0080 0.01 0.90 160 217 Excellent Excellent Ex.101 Res. 3.0 3.0 4.0 0.025 0.0080 0.01 0.90 160 217 Excellent Excellent Ex.102 Res. 3.0 3.0 4.0 0.025 0.0080 0.01 0.90 160 217 Excellent Excellent Ex.103 Res. 3.0 3.0 4.0 0.025 0.0080 0.01 0.90 160 217 Excellent Excellent. Ex. = Example Petition 870260076701, dated 07 / 31 / 2026, pp. 88 / 98 27 / 30 Table 2 (continued) Alloy Composition (in % by mass) Ratio (1) Ratio (2) Melting Point (°C) Shear Strength (N) Fracture Mode Sn Ag In Sb Fe Co Ge P Ga Zr As Pb Zn Mg Cr Ti Mo Pt Pd Au Al Si Ni Bi Ex.104 Res. 3.0 3.0 4.0 0.025 0.0080 0.01 0.90 160 217 Excellent Excellent Ex.105 Res. 3.0 3.0 4.0 0.025 0.0080 0.01 0.90 160 217 Excellent Excellent Ex.106 Res. 3.0 3.0 4.0 0.025 0.0080 0.01 0.90 160 217 Excellent Excellent Ex.107 Res. 3.0 3.0 4.0 0.025 0.0080 0.01 0.90 160 217 Excellent Excellent Ex.108 Res. 3.0 3.0 4.0 0.025 0.0080 0.01 0.90 160 217 Excellent Excellent Ex.109 Res. 3.0 3.0 4.0 0.025 0.0080 0.01 0.0080 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.90 160 218 Excellent Excellent Ex. = Example Petition 870260076701, dated 07 / 31 / 2026, pp. 89 / 98 28 / 30 [Table 3] Alloy Composition (in % by mass) Ratio (1) Ratio (2) Melting Point (°C) Shear Strength (N) Fracture Mode Sn Ag In Sb Fe Co Ge P Ga Zr As Pb Zn Mg Cr Ti Mo Pt Pd Au Al Si Ni Bi Ex. Comp. 1 Res. 3.5 0.00 - 221 Poor Poor Ex. Comp. 2 Res. 1.5 3.0 4.0 0.025 0.45 320 223 Poor Excellent Ex. Comp. 3 Res. 4.0 3.0 4.0 0.025 1.20 120 225 Poor Poor Ex. Comp. 4 Res. 3.0 - 3.0 0.050 0.0080 0.03 3.00 - - 221 Poor Poor Ex. Comp. 5 Res. 3.0 0.5 4.0 0.025 0.15 27 225 Bad Bad Ex. Comp. 6 Res. 3.0 6.0 4.0 0.025 1.80 320 232 Good Bad Ex. Comp. 7 Res. 2.0 2.0 2.0 - 2.5000 1.50 - - 223 Bad Bad Ex. Comp. 8 Res. 3.0 2.0 2.0 0.025 0.30 53 220 Bad Good Ex. Comp. 9 Res. 3.0 3.5 6.0 0.025 1.58 280 228 Bad Bad Ex. Comp. 10 Res. 3.0 3.0 3.0 - 0.0080 0.03 3.00 - - 213 Bad Bad Ex. Comp. 11 Res. 3.0 3.0 4.0 0.0004 0.01 10000 218 Bad Bad Ex. Comp. 12 Res. 3.0 3.0 4.0 0.040 1.44 100 218 Bad Bad Ex. Comp. 13 Res. 3.0 3.0 4.0 0.025 0.1000 0.90 160 375 Bad Bad Ex. Comp. 14 Res.3.0 3.0 4.0 0.025 0.01 — 0.90 160 218 Bad Good Ex. Comp. 15 Res. 3.0 3.0 4.0 0.025 — 0.01 0.90 160 218 Bad Good. Ex. Comp. = Comparative Example, * The underline indicates that it is outside the scope of the present invention. Petition 870260076701, dated 07 / 31 / 2026, pages 90 / 98 29 / 30

[0079] As shown in Table 1 and Table 2, in Examples 1 to 110, all the contents of the respective constituent elements were adequate, and thus all evaluations showed acceptable results for practical use. Furthermore, it was found that Examples 3 to 14, 16, 19, 22, 28 to 31, 37 to 48, 50, 54, 57, 66, 68 to 73, and 77 to 110, which satisfy Relations (1) and (2), showed extremely excellent results in all evaluations. Among the practically acceptable results, the excellent results showed significant differences.

[0080] On the other hand, as shown in Table 3, since Comparative Example 1 did not contain In, Sb, and Fe, the shear strength was poor, and the fracture mode was inadequate. In Comparative Example 2, the Ag content was low, and thus the shear strength was poor. In Comparative Example 3, the Ag content was high, and thus the shear strength was poor, and the fracture mode was inadequate.

[0081] In Comparative Example 4, In was not present, and in Comparative Example 5, the In content was low, and thus the shear strength was poor, and the fracture mode was inadequate. In Comparative Example 6, the In content was high, and thus the fracture mode was inadequate.

[0082] In Comparative Example 7, the Sb content was low and Fe was not included, and thus the shear strength was poor and the fracture mode was inadequate. In Comparative Example 8, the Sb content was low, and thus the shear strength was poor. In Comparative Example 9, the Sb content was high, and thus the shear strength was poor and the fracture mode was inadequate.

[0083] In Comparative Examples 10 to 12, the Fe content was inadequate, and thus the shear strength was poor and the fracture mode was inadequate. In Comparative Example 13, the Co content was high, and thus the melting point was significantly increased, the shear strength was poor, and the fracture mode was inadequate. Comparative Example 14 and Comparative Example 15 contained Ni or Bi, respectively, and thus the Petition 870260076701, dated 07 / 31 / 2026, pages 91 / 98 30 / 30 shear strength was poor.

[0084] FIG. 1 shows an optical microscope photograph of a sample after shear strength measurement. FIG. 1(a) shows Example 14, FIG. 1(b) shows Example 2, and FIG. 1(c) shows Comparative Example 3. As evident from FIG. 1, in Example 14, the weld joint was found to have fractured due to fracture in the weld body. Furthermore, in Example 2, fracture was found to have occurred in the weld body and in the intermetallic compound at the junction interface. On the other hand, in Comparative Example 3, the weld joint was found to have fractured due to fracture in the intermetallic compound at the junction interface. Therefore, in Example 14, the fracture mode was found to be adequate. This result was similar in the other Examples. Industrial Applicability

[0085] The solder according to the present invention can be used in an embedded electronic circuit in a vehicle, such as an ECU, which is an electronic circuit for controlling a vehicle by means of a computer, in order to improve fuel efficiency. On the other hand, for example, the solder according to the present invention can also be used in a consumer electronic device, such as a personal computer, showing an excellent effect. Petition 870260076701, dated 07 / 31 / 2026, pages 92 / 98

Claims

1 / 2 CLAIMS 1. Solder alloy, CHARACTERIZED by having an alloy composition consisting, in % by mass, of Ag: 2.0 to 3.6%, In: 1.0 to 5.0%, Sb: 3.0 to 5.0%, Fe: 0.0010 to 0.0300%, and Co: 0.0000% or more and 0.0500% or less, optionally at least one of Zr, Ge, Ga, P, As, Pb, Zn, Mg, Cr, Ti, Mo, Pt, Pd, Au, Al and Si: 0.100% or less in total, the remainder being Sn.

2. Solder alloy, according to claim 1, CHARACTERIZED by the alloy composition satisfying the following ratios (1) and (2): 0.36 ^ AgxInxSbxFe ^ 1.19 (1) 47 ^ (InxSb) / (AgxFe) ^ 319 (2) wherein Ag, In, Sb and Fe in ratios (1) and (2) each represent the respective content in % by mass in the solder alloy.

3. Solder paste, CHARACTERIZED by having a solder powder consisting of the solder alloy, as defined in claim 1 or 2.

4. Welding sphere, CHARACTERIZED by consisting of the welding alloy, as defined in claim 1 or 2.

5. Welding preform, CHARACTERIZED by consisting of the welding alloy, as defined in claim 1 or 2.

6. Weld joint, CHARACTERIZED by having the weld alloy as defined in claim 1 or 2.

7. Electronic circuit embedded in a vehicle, CHARACTERIZED by having the solder alloy as defined in claim 1 or 2.

8. Electronic ECU circuit, CHARACTERIZED by having the solder alloy Petition 870260077876, dated 04 / 08 / 2026, page 22 / 24 2 / 2, as defined in claim 1 or 2.

9. Vehicle-mounted electronic circuit device, CHARACTERIZED by comprising the vehicle-mounted electronic circuit as defined in claim 7.

10. ECU electronic circuit device, CHARACTERIZED by comprising the ECU electronic circuit, as defined in claim 8. Petition 870260077876, dated 04 / 08 / 2026, pp. 23 / 24

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