Solder alloy, joint, joint material, solder paste, joint structure and electronic control device

Abstract

A solder alloy containing Bi that can form a joint that has heat cycle resistance and drop impact resistance and suppresses the occurrence of lift-off, the solder alloy containing 35% by mass or more and 65% by mass or less of Bi, 0.1% by mass or more and 0.65% by mass or less of Sb, and 0.05% by mass or more and 2% by mass or less of Ag, with the remainder being Sn and unavoidable impurities.

Description

[Technical Field]

[0001] The present invention relates to a solder alloy, a joint, a joint material, a solder paste, a joint structure, and an electronic control device. [Background technology]

[0002] The joining conditions for joining materials (e.g., a printed wiring board and an electronic component), such as the heating temperature and heating time, are set depending on the application of the electronic device and the material and heat resistance of the components that make up the electronic device. Generally, a solder alloy that melts at or below the set heating temperature is used as the joining material. One method for lowering the melting temperature of a solder alloy (which in this specification means the "melting point" or "liquidus temperature") is to add Bi to the solder alloy. However, because Bi is hard and brittle, it reduces the ductility of the solder alloy.

[0003] Therefore, for example, the following solder alloys have been provided as Bi-containing solder alloys with improved ductility.

[0004] A solder alloy characterized by having an alloy composition consisting of, in mass %, 35 to 68% Bi, 0.1 to 2.0% Sb, 0.01 to 0.10% Ni, and the balance Sn (Patent Document 1).

[0005] A lead-free solder alloy containing 32% by mass or more and 40% by mass or less of Bi, 0.1% by mass or more and 1.0% by mass or less of Sb, 0.1% by mass or more and 1.0% by mass or less of Cu, 0.001% by mass or more and 0.1% by mass or less of Ni, with the remainder being Sn and unavoidable impurities (Patent Document 2).

[0006] A SnBiSb-based low-temperature lead-free solder characterized in that the lead-free solder consists, by mass percentage, of 32.8-56.5% Bi, 0.7-2.2% Sb, and the remainder Sn, and the mass percentages of Bi and Sb satisfy the relational expression b = 0.006a2 - 0.672a + 19.61 + c, where a represents the mass percentage of Bi, b represents the mass percentage of Sb, and the value range of c is -1.85≦c≦1.85, and further contains, by mass percentage, one or more metal elements of 0.01-2.5% Ce, 0.05-2.0% Ti, 0.5-0.8% Ag, and 0.05-1% In (Patent Document 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6477965 [Patent Document 2] Patent No. 6804126 [Patent Document 3] Patent No. 6951438 Summary of the Invention [Problem to be solved by the invention]

[0008] Depending on the type of electronic device, the bonded structure (herein, a structure in which multiple bonded materials are bonded via a bonding portion) within the electronic device may be placed in an environment where heat cycles are repeated. This heat cycle can cause thermal fatigue failure (cracks) in the bonded portion. As mentioned above, Bi reduces the ductility of the solder alloy, and therefore, the above-mentioned cracks are likely to occur in the bonded portion formed with the Bi-containing solder alloy.

[0009] Furthermore, when an electronic device is subjected to a strong impact, such as when dropped, a strong, instantaneous external force acts on the joined materials and the joint. To prevent damage to the joint due to this external force, it is necessary to improve the strength and ductility of the solder alloy in a balanced manner. However, as mentioned above, Bi reduces the ductility of the solder alloy, so that joints formed with Bi-containing solder alloys are prone to damage due to the action of the external force.

[0010] Furthermore, when an electronic component having a terminal is used as the material to be joined, a method (through-hole mounting method) is used in which a through-hole is formed in the printed wiring board, the terminal of the electronic component is inserted into the through-hole, and the two are joined together, and the terminal of the electronic component in the through-hole and the land (electrode) of the printed wiring board are joined via a joint (fillet) formed on the printed wiring board. In this joining method, the molten solder hardens from the through-hole toward the printed wiring board during cooling, which tends to concentrate residual stress on the land side of the formed joint. Furthermore, the printed wiring board also thermally shrinks in the vertical direction. Therefore, in this case, the joint is prone to peeling off from the land (lift-off). This lift-off is particularly likely to occur when joining using a solder alloy containing Bi.

[0011] Furthermore, Patent Documents 1 to 3 do not disclose or suggest a solder alloy that has resistance to the above-mentioned cracks (hereinafter referred to in this specification as "heat cycle resistance") and resistance to the above-mentioned external forces (hereinafter referred to in this specification as "drop impact resistance") and that suppresses the occurrence of lift-off.

[0012] The object of the present invention is to solve the above-mentioned problems and to provide a solder alloy, a joining material, and a solder paste that contain Bi and are capable of forming a joint that has heat cycle resistance and drop impact resistance and suppresses the occurrence of lift-off. [Means for solving the problem]

[0013] (1) The solder alloy of the present invention contains 35% by mass or more and 65% by mass or less of Bi, 0.1% by mass or more and 0.65% by mass or less of Sb, 0.05% by mass or more and 2% by mass or less of Ag, and the remainder consisting of Sn and inevitable impurities.

[0014] (2) The solder alloy of the present invention preferably further contains at least one element selected from the group consisting of P, Ga, and Ge in a total amount of 0.001% by mass to 0.05% by mass.

[0015] (3) The solder alloy of the present invention preferably further contains one or more elements selected from the group consisting of Mn, Ti, Al, Cr, V, Fe, Mg, Pd, Pb, and Mo in a total amount of 0.001% by mass to 0.05% by mass.

[0016] (4) A bonding material of the present invention includes the solder alloy according to any one of (1) to (3) above.

[0017] (5) The solder paste of the present invention comprises a powdered solder alloy according to any one of (1) to (3) above, and a flux containing a base resin, a thixotropic agent, an activator, and a solvent.

[0018] (6) The joint of the present invention is formed from the solder alloy according to any one of (1) to (3) above.

[0019] (7) The joint of the present invention is formed from the joint material described in (4) above.

[0020] (8) The joint of the present invention is formed from the solder paste described in (5) above.

[0021] (9) The joined structure of the present invention has a first joined material, a joining portion, and a second joined material, the joining portion being a joining portion described in any one of (6) to (8) above, and the first joined material and the second joined material being joined via the joining portion.

[0022] (10) An electronic control device of the present invention has the joining structure described in (9) above. [Effects of the Invention]

[0023] The solder alloy, bonding material, and solder paste of the present invention contain Bi and are capable of forming a bonded joint that has heat cycle resistance and drop impact resistance and can suppress the occurrence of lift-off. [Brief explanation of the drawings]

[0024] [Figure 1] (1) Plan view showing the shape of the test piece used in the tensile test. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0026] 1. Solder alloy The solder alloy of this embodiment contains 35% by mass or more and 65% by mass or less of Bi, 0.1% by mass or more and 0.65% by mass or less of Sb, 0.05% by mass or more and 2% by mass or less of Ag, and the remainder being Sn and unavoidable impurities.

[0027] The solder alloy of this embodiment contains predetermined amounts of Bi, Sb, Ag, and Sn, and thus can improve the strength and ductility of the solder alloy in a balanced manner while still containing Bi.

[0028] As a result, even if a crack occurs in the joint due to repeated heat cycles and stress is concentrated in the crack, the solder alloy of this embodiment can suppress plastic deformation and slip deformation at the tip of the crack and suppress the progression of the crack.

[0029] Furthermore, as a result, the solder alloy of this embodiment can suppress damage to the joint caused by the action of a sudden, concentrated, strong external force (hereinafter simply referred to as "external force") on the joint, such as when an electronic device is dropped. As mentioned above, in order to suppress the propagation of cracks that occur in a joint, it is essential that the joint is resistant to plastic deformation and sliding deformation. On the other hand, a joint that is resistant to plastic deformation absorbs less of the impact energy generated by the action of the above-mentioned external force, and any impact energy that cannot be absorbed will damage the joint. In addition, the above-mentioned external force acts on the joint from multiple directions (at least two of tension, compression, shear, bending, and torsion). Therefore, in order to prevent damage to the joint due to the impact energy / stress associated with the external force, it is necessary to improve the strength and ductility of the solder alloy in a balanced manner, that is, to improve the yield stress, tensile stress, and fracture strain of the joint in a balanced manner. As described above, the solder alloy of this embodiment, due to its configuration, can form a joint having good balance of strength and ductility, and therefore can provide a joint having good resistance to the external force, that is, good drop impact resistance.

[0030] Furthermore, as a result, the solder alloy of this embodiment is able to easily relieve residual stress that occurs within the joint when the solder solidifies, and can suppress the occurrence of cracks within the joint caused by the residual stress and the occurrence of the above-mentioned lift-off.

[0031] (1)Bi The solder alloy of this embodiment contains 35% by mass or more and 65% by mass or less of Bi, which lowers the melting temperature of the solder alloy while suppressing a decrease in the ductility of the solder alloy, and also strengthens the joint through solid solution of Bi in Sn, thereby improving the strength and ductility of the joint in a balanced manner.

[0032] On the other hand, if the Bi content is outside the above range, the strength and ductility of the solder alloy may decrease.

[0033] The Bi content is preferably 35% by mass or more and 60% by mass or less. Furthermore, the Bi content is more preferably 40% by mass or more and 59% by mass or less. The Bi content can be preferably 50% by mass or more, or 54% by mass or more, and can also be 58% by mass or less, 56.5% by mass or less, or 56% by mass or less. By keeping the Bi content within this range, the ductility and strength of the joint can be further improved.

[0034] (2) Sb The solder alloy of this embodiment contains 0.1 mass % or more and 0.65 mass % or less of Sb, which allows the Sb to dissolve in Sn, thereby strengthening the joint, and also improves the strength and ductility of the joint through the precipitation and dispersion of fine β-SnSb intermetallic compounds, thereby achieving a balanced improvement in the strength and ductility of the joint.

[0035] On the other hand, if the Sb content is less than 0.1 mass%, the joint may not be sufficiently strengthened, and if the Sb content exceeds 0.65 mass%, coarse β-SnSb intermetallic compounds are crystallized as primary crystals, which may impair the ductility of the joint.

[0036] The Sb content is preferably 0.2 mass% or more and 0.65 mass% or less. Furthermore, the Sb content is more preferably 0.3 mass% or more and 0.65 mass% or less. By setting the Sb content within this range, the ductility and strength of the joint can be further improved.

[0037] (3) Ag The solder alloy of this embodiment contains 0.05% by mass to 2% by mass of Ag, which lowers the melting temperature of the solder alloy and improves the strength and ductility of the joint through the precipitation and dispersion of fine AgSn intermetallic compounds, thereby achieving a balanced improvement in the strength and ductility of the joint.

[0038] On the other hand, if the Ag content is less than 0.05 mass%, the precipitation strengthening of the joint may be insufficient, and if the Ag content exceeds 2 mass%, the Ag3Sn intermetallic compounds may become coarse, which may impair the ductility of the joint.

[0039] The Ag content is preferably 0.1% by mass or more and 1.5% by mass or less. The Ag content can be preferably 1% by mass or less, 0.8% by mass or less, or 0.5% by mass or less. Furthermore, the Ag content is more preferably 0.2% by mass or more and 0.4% by mass or less. By setting the Ag content within this range, the ductility and strength of the joint can be further improved.

[0040] The solder alloy of this embodiment may further contain one or more elements selected from the group consisting of P, Ga, and Ge in a total amount of 0.001% by mass to 0.05% by mass. Adding one or more elements selected from the group consisting of P, Ga, and Ge to the solder alloy can suppress oxidation of the solder alloy and improve the wettability of the solder alloy, thereby making it possible to provide highly reliable joints. On the other hand, if the total content of one or more elements selected from the group consisting of P, Ga, and Ge exceeds 0.05 mass %, voids may occur in the bonded joint, possibly deteriorating the heat cycle resistance of the bonded joint.

[0041] The solder alloy of this embodiment may further contain one or more elements selected from the group consisting of Mn, Ti, Al, Cr, V, Fe, Mg, Pd, Pb, and Mo in a total amount of 0.001% by mass or more and 0.05% by mass or less. By adding one or more elements selected from the group consisting of Mn, Ti, Al, Cr, V, Fe, Mg, Pd, Pb, and Mo to a solder alloy, the intermetallic compounds in the joint become finer, which makes it possible to suppress the propagation of cracks and achieve good heat cycle resistance. On the other hand, if the total content of one or more elements selected from Mn, Ti, Al, Cr, V, Fe, Mg, Pd, Pb, and Mo exceeds 0.05 mass%, voids may occur in the joint, which may deteriorate the heat cycle resistance. Furthermore, when Fe is added to the solder alloy of this embodiment, if the Fe content exceeds 0.05 mass %, there is a risk that needle-like substances may be easily generated in the solder alloy during the manufacturing process of the solder alloy. Here, when a solder alloy containing needle-like substances is powdered into spheres, the presence of these needle-like substances may hinder the spheroidization, making it difficult to powder into spheres.

[0042] The balance of the solder alloy of this embodiment is Sn and unavoidable impurities, that is, the solder alloy of this embodiment may contain alloying elements other than the above-mentioned alloying elements as unavoidable impurities.

[0043] 2. Bonding material The bonding material of this embodiment contains the solder alloy of this embodiment and can be used in the form of a solder paste, solder ball, wire, solder preform, flux cored solder, etc., which will be described later. The form of the bonding material can be appropriately selected depending on the size, type, and application of the materials to be bonded, the solder bonding method, etc. Furthermore, by including the solder alloy of this embodiment, the joining material of this embodiment can form a joining portion that has heat cycle resistance and drop impact resistance, while lowering the melting temperature by adding Bi, and suppresses the occurrence of lift-off.

[0044] 3. Solder paste The solder paste of this embodiment contains the solder alloy of this embodiment in powder form (hereinafter referred to as "alloy powder"), and is produced, for example, by kneading the alloy powder with flux to form a paste.

[0045] <Flux> The flux may include, for example, a base resin, a thixotropic agent, an activator, and a solvent.

[0046] Examples of the base resin include rosin resins, acrylic resins obtained by polymerizing at least one monomer such as acrylic acid, methacrylic acid, various esters of acrylic acid, various esters of methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, esters of maleic acid, esters of maleic anhydride, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl chloride, and vinyl acetate, epoxy resins, and phenolic resins. These may be used alone or in combination.

[0047] Examples of the thixotropic agent include hydrogenated castor oil, hydrogenated castor oil, bisamide-based thixotropic agents (saturated fatty acid bisamide, unsaturated fatty acid bisamide, aromatic bisamide, etc.), oxyfatty acids, dimethyldibenzylidene sorbitol, etc. These can be used alone or in combination.

[0048] Examples of the activator include organic acids (monocarboxylic acids, dicarboxylic acids, and other organic acids), halogen-containing compounds, amine-based activators, etc. These can be used alone or in combination.

[0049] Examples of the solvent include alcohol-based, butyl cellosolve-based, glycol ether-based, and ester-based solvents, which can be used alone or in combination.

[0050] The flux may also contain an antioxidant, such as a hindered phenol-based antioxidant, a phenol-based antioxidant, a bisphenol-based antioxidant, or a polymer-type antioxidant. The flux may further contain additives such as a matting agent and an antifoaming agent.

[0051] When preparing the solder paste of this embodiment, the blending ratio (mass %) of the alloy powder to the flux can be set to 65:35 to 95:5 in terms of alloy powder:flux ratio. Alternatively, for example, the blending ratio can be set to 85:15 to 93:7 or 87:13 to 92:8.

[0052] The particle size of the alloy powder can be 1 μm or more and 40 μm or less. The particle size can also be 5 μm or more and 35 μm or less, or 10 μm or more and 30 μm or less. The particle size of the alloy powder can be changed as needed.

[0053] Furthermore, the solder paste of this embodiment contains the alloy powder, and thus can form a joint that has heat cycle resistance and drop impact resistance and suppresses the occurrence of lift-off, while lowering the melting temperature by adding Bi.

[0054] 4.Joint part The joint of this embodiment is formed using the solder alloy and joint material (hereinafter, unless otherwise specified, including solder paste) of this embodiment, and is used to join materials to be joined together. The method for forming the joint of this embodiment may be any method that can be formed using the solder alloy and joining material of this embodiment, such as a reflow method, a flow method, etc. The form of the joining material to be used may also be appropriately selected depending on the size, type, and application of the materials to be joined, the method for forming the joint, etc.

[0055] 5.Joint structure The bonded structure of this embodiment includes a first material to be bonded, a bonding portion, and a second material to be bonded. The bonding portion is the bonding portion of this embodiment, and the first material to be bonded and the second material to be bonded are bonded via the bonding portion.

[0056] The first and second materials to be joined can be, for example, a substrate (a substrate whose surface is made of ceramic, metal, alloy, or resin and on which no electronic circuit is formed), a printed wiring board (a substrate on which an electronic circuit is formed but on which no electronic components are mounted), a printed circuit board (a printed wiring board on which electronic components are mounted), an electronic component, a silicon wafer, a semiconductor package, a semiconductor chip, etc. Different types of materials to be joined may be combined, or the same type of materials to be joined may be combined. Specific combinations include, for example, a printed wiring board and an electronic component, a printed wiring board and a semiconductor chip, a semiconductor package and a printed circuit board, and a printed wiring board and another printed wiring board.

[0057] The bonded structure of this embodiment is produced, for example, by the following method. When a printed wiring board is used as the first material to be joined and an electronic component is used as the second material to be joined, the joining material of this embodiment is first placed (or, in the case of solder paste, applied) at a predetermined position on the first material to be joined, for example, on an electronic circuit, and the second material to be joined is then placed on the joining material. These are then reflowed at a predetermined heating temperature, for example, a peak temperature of 200°C, to form a joint that joins the first material to be joined and the second material to be joined. This produces the joined structure (printed circuit board) of this embodiment.

[0058] When a solder preform is used as the joining material, the solder preform with flux applied to its surface is placed at a predetermined position on the first material to be joined, and the second material to be joined is placed on the solder preform and heated. Furthermore, when an electronic component with solder balls, such as a Ball Grid Array (BGA), is used as the second material to be joined, solder paste is applied to the surface of the BGA or to a predetermined position on the first material to be joined, and the second material to be joined is placed on the predetermined position on the first material to be joined and heated.

[0059] The bonded structure of this embodiment has the bonded portion of this embodiment, which allows the bonded structure of this embodiment to have heat cycle resistance and drop impact resistance, and is also less susceptible to lift-off, thereby maintaining high reliability.

[0060] 6. Electronic control unit The electronic control device of this embodiment is equipped with the joining structure of this embodiment, for example, a printed circuit board on which an electronic component and a printed wiring board are joined, which is placed inside a housing, and controls the operation of the components that make up the electronic device. The electronic control device of this embodiment includes the joining structure of this embodiment, which provides heat cycle resistance and drop impact resistance, and is less susceptible to lift-off, ensuring high reliability. [Example]

[0061] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0062] [Table 1]

[0063] [Table 2]

[0064] [Table 3]

[0065] (1) Tensile test For each of the solder alloys shown in Tables 1 to 3, a test piece 10 as shown in FIG. 1 was prepared. The test piece 10 was prepared so that the central parallel portion (between G1 and G2 in FIG. 1) was as follows. Length of the central parallel section (L in Figure 1): 12 mm Width of the central parallel part (W in Figure 1): 2 mm Thickness of central parallel part: 4mm

[0066] Then, the test piece 10 was subjected to a tensile test in the following manner. The test piece 10 was pulled in the X direction at room temperature with a stroke of 0.72 mm / min using a bench-top precision universal testing machine (product name: Autograph AG-50kNX plus, manufactured by Shimadzu Corporation) until it broke. The stroke distance when the test piece 10 broke was defined as GL1, and the length L of the central parallel part of the test piece before tension was defined as GL0. The elongation of the test piece 10 was calculated based on the following formula. Elongation rate (%) = (GL1 - GL0) / GL0 x 100 Five test pieces 10 were prepared for each solder alloy, and the elongation and average elongation values ​​for each were calculated according to the above procedure and evaluated based on the following criteria. The results are shown in Tables 4 to 6. ◎: The average elongation rate is 35% or more ○: The average elongation rate is 30% or more and less than 35% △: The average elongation rate is 25% or more and less than 30% ×: The average elongation rate is less than 25%

[0067] (2) Drop impact test Each solder paste was prepared by kneading a flux containing the following components with the solder alloy powder (powder particle size 20 μm to 38 μm) shown in Tables 1 to 3 in the following mixing ratios (mass %). The solder alloy powder was prepared by atomization. Solder alloy powder:flux = 89:11 <Flux composition> Hydrogenated acid-modified rosin (product name: KE-604, manufactured by Arakawa Chemical Industries, Ltd.): 49% by mass Surfactants (glutaric acid: 0.3% by mass, suberic acid: 2% by mass, malonic acid: 0.5% by mass, dodecanedioic acid: 2% by mass, dibromobutenediol: 2% by mass) Fatty acid amide (product name: Suripax ZHH, manufactured by Nippon Kasei Co., Ltd.): 6% by mass Diethylene glycol monohexyl ether: 35.2% by mass Hindered phenol antioxidant (product name: Irganox 245, manufactured by BASF Japan Ltd.): 3% by mass

[0068] The following tools were also prepared: LGA (Land Grid Array, pitch: 0.5 mm, size: 12 mm x 12 mm x 1 mm, number of terminals: 228) Glass epoxy board (base material: FR-4, surface treatment: Cu-OSP, thickness: 1.0 mm, with a pattern that can mount the above LGA) Metal mask (thickness: 100 μm, corresponding to the above pattern) For each solder paste, five of the glass epoxy substrates and 20 LGAs were used. Using the above tools and each solder paste, each test substrate was fabricated according to the following procedure, and a drop impact test was carried out.

[0069] First, solder paste was printed on the glass epoxy board using a metal mask. Four LGAs per glass epoxy board were then placed in the designated positions on the printed solder paste. The thickness of the solder paste printing film was adjusted using the metal mask. The glass epoxy board on which the LGA was mounted was then reflowed using a reflow furnace (product name: TNV-M6110CR, manufactured by Tamura Corporation) to produce a test board having an LGA, a glass epoxy board, and a joint that joins them together. The reflow soldering was performed with a preheat of 100 to 120°C, a peak temperature of 200°C, a time of 60 seconds above 150°C, and a cooling rate of 1 to 4°C / sec from the peak temperature to 100°C. The oxygen concentration was set to 200±100 ppm.

[0070] Next, the prepared test substrate was subjected to a drop impact test under the following conditions using a drop impact tester (product name: HDST-150J, Shinyei Technology Co., Ltd.). That is, in accordance with the JEDEC standard JESD22-B111, the test board was repeatedly dropped from a height that applied a shock waveform with an acceleration of 1,500 G and a width of 0.5 ms. During the drop impact test, the electrical resistance of each joint of the test board was constantly observed, and when the resistance value exceeded 1,000 Ω, it was determined that the board had broken, and the number of drops until the board broke was counted. Five test boards were prepared for each type of solder paste, and the above measurement results were plotted against a Weibull curve for a total of 20 LGAs. The number of drops at which the cumulative failure rate reached 63.2% was estimated as the characteristic life, and the results were evaluated according to the following criteria. The results are shown in Tables 4 to 6. ◎: Characteristic life is 110 times or more ○: Characteristic life is 90 times or more but less than 110 times △: Characteristic life is 70 times or more but less than 90 times ×: The characteristic life is less than 70 times

[0071] (3) Heat cycle test The following tools were prepared: Chip parts (3.2mm x 1.6mm) Glass epoxy board (base material: FR-4, surface treatment: Cu-OSP, thickness: 1.2 mm, with a pattern that can mount the above chip components) Metal mask (thickness: 120 μm, corresponding to the above pattern) For each solder paste, three of the glass epoxy substrates and 30 chip components were used. Using the above tools and each solder paste, each test substrate was fabricated according to the following procedure, and a heat cycle test was carried out.

[0072] First, solder paste was printed on the glass epoxy board using a metal mask. Then, 10 chip components were placed on each glass epoxy board at predetermined positions on the printed solder paste. The thickness of the solder paste printing film was adjusted using the metal mask. The glass epoxy substrates on which the chip components were mounted were then reflowed using a reflow furnace (product name: TNV-M6110CR, manufactured by Tamura Corporation) to produce three mounting substrates each having chip components, a glass epoxy substrate, and a joint for joining them. The reflow soldering was performed with a preheat of 100 to 120°C, a peak temperature of 200°C, a time of 60 seconds above 150°C, and a cooling rate of 1 to 4°C / sec from the peak temperature to 100°C. The oxygen concentration was set to 200±100 ppm.

[0073] Next, using a thermal shock tester (product name: ES-76LMS, manufactured by Hitachi Appliances, Inc.), each mounted board was subjected to a thermal shock cycle as follows, with one cycle being set from -40°C (30 minutes) to 125°C (30 minutes), to create test boards a to c. a: Test board exposed to the above thermal shock cycle repeated 2,000 times b: Test board exposed to the above thermal shock cycle repeated 2,250 times c: Test board exposed to the above thermal shock cycle repeated 2,500 times

[0074] The target portions of each test substrate a to c were cut out and sealed with epoxy resin (product name: HERZOG Epo low viscosity resin (base and hardener), manufactured by HERZOG Japan Co., Ltd.). A wet polishing machine (product name: TegraPol-25, manufactured by Marumoto Struers K.K.) was then used to polish each test board so that the central cross section of each chip component mounted on it could be seen, and a scanning electron microscope (product name: TM-1000, manufactured by Hitachi High-Technologies Corporation) was used to observe the condition of each joint on each test board a to c, checking for the presence or absence of cracks that completely crossed the joint, and evaluating them according to the following criteria. The results are shown in Tables 4 to 6. ◎: No cracks occurred that completely crossed the joint in any of the test substrates a to c. ○: No cracks occurred that completely crossed the joint in test substrates a and b. △: No cracks occurred that completely crossed the joint in test substrate a. ×: In all test substrates a to c, cracks occurred that completely crossed the joint.

[0075] (5) Lift-off occurrence confirmation test The following tools were prepared: Connector parts (product name: S15B-EH(LF)(SN), manufactured by JST Mfg. Co., Ltd.) Glass epoxy board (base material: FR-4, surface treatment: Cu-OSP, size: 50mm x 50mm, thickness: 1.6mm, 2.5mm pitch, with 1.6mm diameter lands and 1.0mm diameter through holes) A 200μm thick metal mask with a 3mm diameter opening pattern at a 5mm pitch. Using the above tools and each solder paste, each test substrate was fabricated according to the following procedure, and a lift-off occurrence confirmation test was carried out.

[0076] First, solder paste was printed on a glass epoxy substrate using a metal mask. Then, the terminals of the connector components were inserted into the designated through-holes in the glass epoxy substrate, and reflow was performed using a reflow oven (product name: TNP-538EM, manufactured by Tamura Corporation) to produce a test substrate with a solder joint (fillet) joining the connector components to the glass epoxy substrate. The reflow was performed under the same conditions as in (2) Drop Impact Test.

[0077] Next, the target portion of each test board was cut out and sealed with epoxy resin (product name: Epomount (base and hardener), manufactured by Refine Tech Co., Ltd.). A wet polishing machine (product name: TegraPol-25, manufactured by Marumoto Struers Co., Ltd.) was used to polish the test board so that the central cross section of the terminal of each connector component mounted on the test board could be seen. The test boards were then observed using a scanning electron microscope (product name: TM-1000, manufactured by Hitachi High-Technologies Corporation) and evaluated according to the following criteria. Eight terminals were evaluated. The results are shown in Tables 4 to 6. ○: No lift-off occurred ×: Lift-off occurs

[0078] (5) Test to confirm the generation of needle-shaped substances Solder ingots were prepared from each of the solder alloys, and solder alloy powder was prepared from each of the solder ingots under the following conditions. First, 50 g of solder ingot, 890 g of castor oil, and 10 g of hydrogenated acid-modified rosin (product name: KE-604, manufactured by Arakawa Chemical Industries, Ltd.) were placed in a 2 L stainless steel beaker, and the mixture was continuously heated using a mantle heater. When the temperature of the contents in the stainless steel beaker reached 100°C, a homogenizer (manufactured by SMT Co., Ltd.) was used to set the rotation speed to 2,000 rpm and begin stirring the contents in the stainless steel beaker. Heating by the mantle heater continued during stirring. When the temperature of the contents in the stainless steel beaker reached 200°C, heating was stopped, the rotation speed of the homogenizer was changed to 10,000 rpm, and the contents in the stainless steel beaker were then stirred for 5 minutes. After stirring was completed, the contents in the stainless steel beaker were cooled to room temperature. The solder alloy powder that had settled in the castor oil was then removed from the stainless steel beaker and washed with ethyl acetate to remove any deposits. The condition of the solder alloy powder was then observed at 200x magnification using a digital microscope. The observation results were evaluated based on the following criteria. The results are shown in Tables 4 to 6. ○: No needle-shaped material was generated in the solder alloy powder ×: Needle-shaped substances were generated in the solder alloy powder

[0079] [Table 4]

[0080] [Table 5]

[0081] [Table 6]

[0082] As described above, the solder alloy of this example contains predetermined amounts of Bi, Sb, Ag, and Sn, and thus can form a joint that exhibits good results in any of the above (1) to (4) while containing Bi. Furthermore, the solder alloy of this example can suppress the formation of needle-like substances even when Fe is added. Here, the strain rate when the car collides with the object is 10 -3 (s -1 ) to 10 3 (s -1 ) In addition, (1) in the tensile test, a test piece with a GL0 of 12 mm is pulled at a stroke of 0.72 mm / min, which, when converted to a strain rate, is 10 ―3 (s -1 ) Thus, it can be seen that the solder alloy of this example can form a joint having good resistance, i.e., good strength and ductility, even when subjected to a load comparable to the strain rate when an automobile collides with an object.

[0083] Thus, the solder alloy of this example, while containing Bi, can form a joint that has heat cycle resistance and drop impact resistance and can suppress the occurrence of lift-off. Furthermore, electronic control devices and electronic equipment having such a joint can exhibit high reliability. [Explanation of symbols]

[0084] 10 test specimens

Claims

1. A solder alloy comprising: 35% by mass or more and 65% by mass or less of Bi; 0.1% by mass or more and 0.65% by mass or less of Sb; 0.05% by mass or more and 2% by mass or less of Ag; and the remainder being Sn and unavoidable impurities.

2. The solder alloy according to claim 1 , further comprising at least one element selected from the group consisting of P, Ga, and Ge in a total amount of 0.001 mass % to 0.05 mass %.

3. 2. The solder alloy according to claim 1, further comprising one or more elements selected from the group consisting of Mn, Ti, Al, Cr, V, Fe, Mg, Pd, Pb, and Mo in a total amount of 0.001% by mass or more and 0.05% by mass or less.

4. A solder alloy as described in claim 2, further containing one or more elements selected from the group consisting of Mn, Ti, Al, Cr, V, Fe, Mg, Pd, Pb and Mo in a total amount of 0.001 mass% or more and 0.05 mass% or less.

5. A bonding material comprising the solder alloy according to any one of claims 1 to 4.

6. The solder alloy according to any one of claims 1 to 4, which is in a powder form; A solder paste comprising a flux including a base resin, a thixotropic agent, an activator, and a solvent.

7. A joint formed from the solder alloy according to any one of claims 1 to 4.

8. A joint formed from the joint material according to claim 5 .

9. A joint formed with the solder paste according to claim 6.

10. A joint having a first workpiece, a joint portion, and a second workpiece, The joint is the joint according to claim 7, A joined structure, wherein the first joined material and the second joined material are joined via the joining portion.

11. A joint having a first joined material, a joining portion, and a second joined material, The joint is the joint according to claim 8 , A joined structure, wherein the first joined material and the second joined material are joined via the joining portion.

12. A joint having a first joined material, a joining portion, and a second joined material, The joint is the joint according to claim 9 , A joined structure, wherein the first joined material and the second joined material are joined via the joining portion.

13. An electronic control device comprising the joint structure according to claim 10.

14. An electronic control device having the joint structure described in claim 11.

15. An electronic control device having the joint structure described in claim 12.