TWI778648B - Solder alloy - Google Patents

Abstract

The present invention discloses a solder alloy. The solder alloy, in terms of mass%, has Ag: 1 to 4%, Cu: 0.5 to 1%, Bi: more than 4% and 5.5% or less, Sb: more than 1.2% and 5.5% or less, and Ni: 0.01% or more and not more than 0.1%, Co: 0.1% or less, S: more than 0.001% and 0.1% or less, and the remainder is the alloy composition of Sn. By fine-tuning the composition and type of the Bi-Sb-Ni-Co-S doped metal in the Sn-Ag-Cu series alloy body, the tensile strength of the solder alloy is improved, and the connection between the printed circuit board and the electronic parts is improved. The solder alloy has excellent vibration resistance and high reliability for automotive electronics.

Description

solder alloy

The present invention relates to a solder alloy, and particularly relates to a high strength, vibration resistant solder alloy for automotive electronics and its application.

In recent years, the electronic use of automobiles has continued to progress, gradually changing from fuel vehicles to hybrid vehicles and electric vehicles. Hybrid vehicles and electric vehicles are equipped with in-vehicle circuits, which are constructed by soldering electronic parts to printed circuit boards. In-vehicle circuits used to be located in the vehicle interior where the vibration environment is relatively mild. With the expansion of applications, they have become directly mounted in the engine compartment, the oil compartment of the transmission, and even directly mounted on the mechanical device.

In the manufacturing process of automotive circuits, electronic components or semiconductor chips need to be fixed and connected to the electronic carrier board in order to play a complete electronic product design function. The technology and process of soldering require extremely high temperatures, consume a lot of energy, and emit various greenhouse gases including carbon dioxide. The reflow soldering process has always raised different voices of reform in the industry.

In February 2003, the European Union formulated regulations to promote the Restriction of Hazardous Substances (RoHS), which came into effect on July 1, 2006, and regulates that all electronic products sold to the European Union shall not contain heavy metal lead materials. The global solder industry The chain has set off a wave of change in lead-free electronics, jointly researching and cooperating to develop solder, and gradually transforming to lead-free solder, using tin, silver and copper composites to replace lead-containing materials, which has also driven the development of electronic components, carrier boards and electronic assembly equipment. Lead-free transition.

In addition, with the expansion of the mounting area, the on-board circuit will be exposed to various external loads such as heat and cold temperature differences, shocks, and vibrations during mounting. For example, an in-vehicle circuit mounted in an engine room is exposed to a high temperature of 125°C or more when the engine is operating. On the other hand, when the engine is stopped, If it is a cold area, it will be exposed to a low temperature below -40°C. When in-vehicle circuits are exposed to such a temperature difference between cold and heat, stress is concentrated at the joints due to the difference in thermal expansion coefficients between electronic components and printed circuit boards. Therefore, when the conventional Sn-3Ag-0.5Cu solder alloy is used, there is a possibility of fracture of the joint, and a solder alloy that can suppress the fracture of the joint even in an environment with a severe temperature difference between cold and heat has been studied.

Since the commonly used lead-free solder material for solder ball joints is the tin-silver-copper alloy series (SAC family), due to its high melting point, during the reflow process (Reflow Process), it is easy to cause lead-free solder due to higher temperatures. The rapid shrinkage of the material volume, coupled with the volatilization of the flux, makes it too late for the air to escape, resulting in void defects, which in turn cause product failure due to extremely small stress during reliability testing.

Tin-based soldering technology considers factors such as reduced environmental impact and cost savings, resulting in the need for low temperature production processes. Low-temperature soldering technology reduces the peak temperature of component soldering from 250 °C to 180 °C, and the soldering temperature is reduced by about 70 degrees, reducing the problems of high heat and high energy consumption in the manufacturing process of electronic products. The entire low-temperature soldering technology test And the verification process uses low temperature solder, using existing reflow soldering equipment, effectively reducing production costs.

In the prior art, in Sn-Ag-Cu-Bi-Sb-Ni-Co based solder alloys, the alloy composition of Sb: 1.5% or less or Sb: 3.0% or more and Bi: 2.7% or less can reduce voids occur. When the alloy composition of Ni: 0.1% or more or Ni: 0.04% and Bi: 3.2%, the shock resistance before and after the thermal cycle test can be enhanced. When Bi: 3.2% or less or Bi: 3.5%, and Co: 0.001% alloy composition, it can reduce the occurrence of cracks and pores in welded joints after thermal cycling. When Bi: alloy composition below 3.2%, the crack generation rate of welded joints after thermal cycling can be reduced. The alloy composition of Bi: 4.8% or less can reduce the cracking of the fillet after thermal cycle.

However, the above technologies still need to be further improved in mass production. When an in-vehicle circuit is exposed to thermal cycles, stress is applied to the joints due to differences in thermal expansion coefficients between printed circuit boards and electronic components. On the other hand, when vibration is applied to the on-board circuit, the stress is Different from the stress caused by expansion and contraction of printed circuit boards and electronic parts during thermal cycling, it should be a stress close to external shock. That is, since the thermal cycle test and the vibration test have different behaviors of the load applied to the joint, it is necessary to adopt an appropriate alloy design in order to cope with the expansion of the mounting area of the substrate. In addition, in order to prevent breakage of the junction of the in-vehicle circuit regardless of the mounting area of the in-vehicle circuit, it is necessary to increase the strength of the solder alloy itself that forms the junction. Based on this point of view, the conventional alloy composition also needs to be re-examined.

Combining the above technologies, there are still many problems to be overcome in mass production, (1) for the occurrence of voids under high temperature use; (2) for the reliability improvement after thermal cycling at low temperature process temperatures; (3) for the resistance to Improved shock and vibration resistance. In view of the above problems, it is necessary to propose a high-strength, vibration-resistant, low-temperature process solder alloy that can be used in automotive electronics and its application.

The main purpose of the present invention is to provide a solder alloy, by doping a small amount of metal Bi, Sb, Ni, Co, Ti and non-metal element S in the Sn-Ag-Cu alloy body, by fine-tuning the Sn-Ag- The element type of the Cu-based alloy main body and the composition of the Bi-Sb-Ni-Co-Ti-S doping elements are fine-tuned to improve the tensile strength of the solder alloy, so that the joint between printed circuit boards and electronic parts has excellent resistance Vibration, and high reliability of automotive electronics.

Yet another object of the present invention is to use the solder paste of the solder alloy, and the solder joint. By fine-tuning the element type of the Sn-Ag-Cu alloy main body and fine-tuning the composition of the Bi-Sb-Ni-Co-Ti-S doping element, the solder alloy can reduce the process temperature and improve the tensile strength of the solder alloy. The junction between the printed circuit board and electronic components has excellent vibration resistance and high reliability for automotive electronics.

The present invention fine-tunes the Al content and the S content for Sn-Ag-Cu-Bi-Sb-Ni-Co-Ti-S based solder alloys. As a result, it was found that within a specific range, the failure mode in the solder alloy near the intermetallic compound layer can be improved, thereby improving the reliability of the vibration resistance.

In order to achieve the above object, the present invention provides a solder alloy characterized in that, in mass %, Ag: 1-4%, Cu: 0.5-1%, Bi: more than 3% and 5.5% or less, Sb: More than 1.2% and less than 5.5%, Ni; more than 0.01% and less than 0.1%, Co: more than 0.001% and less than 0.1%, S: more than 0.001% and less than 0.1%, and the remainder is Sn alloy composition; The Ag composition includes an Ag with a nano-scale powder particle size and an Ag with a micro-scale powder particle size. When calculated by mass %, in the composition of 1~4% Ag, the nano-scale powder The particle size of Ag is more than 10%, and the rest is Ag with micron-scale powder particle size.

According to one feature of the present invention, the composition of the solder alloy satisfies the following equations (1) to (3).

0.020%≦Ni+Co≦0.105% (1)

9.1%≦Sb+Bi≦10.4% (2)

0.002%≦Ti+S≦0.02% (3)

In the formulas (1) to (3), Ni, Co, Bi, Sb, Ti, and S represent the content (mass %) of each element in the solder alloy.

According to one feature of the present invention, when calculated in mass %, in the composition of Ti, the Ti with nano-scale powder particle size is more than 50%, and the rest is Ti with micro-scale powder particle size.

In order to achieve another object of the present invention, the present invention provides a solder paste characterized by having the above-described solder alloy.

In order to achieve another object of the present invention, the present invention provides a solder joint characterized by having the above-described solder alloy.

The effect of the present invention is that by doping a small amount of metal Bi, Sb, Ni, Co, Ti and non-metallic element S in the main body of the Sn-Ag-Cu alloy, the solder alloy can reduce the process temperature and improve the performance of the solder alloy. Tensile strength, resulting in excellent joints between printed circuit boards and electronic parts Vibration resistance and high reliability of automotive electronics. In particular, it is suitable for in-vehicle circuits that are exposed to an environment with a large temperature difference between hot and cold, such as an engine room.

In order to make the above-mentioned and other objects, features, and advantages of the present invention more clearly understood, several preferred embodiments are hereinafter described in detail in conjunction with the accompanying drawings.

FIG. 1 shows the X-ray diffraction results of the low-temperature solder powder for vehicle use of the present invention.

FIG. 2 is the appearance of the tin powder of the present invention magnified by a thousand times under a field emission electron microscope.

While the present invention may be embodied in various forms of embodiment, those shown in the drawings and described herein are preferred embodiments of the invention. Those skilled in the art will appreciate that the apparatus and methods specifically described herein and illustrated in the accompanying drawings are considered to be exemplary, non-limiting exemplary embodiments of the present invention, and that the scope of the present invention is limited only by the scope of the claims be defined. Features illustrated or described in connection with one exemplary embodiment may be combined with features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention. The present invention will be described in more detail below. In this specification, the "%" of the solder alloy composition refers to "% by mass" unless otherwise specified.

The present invention provides a solder alloy. The Sn-Ag-Cu alloy body is doped with a small amount of metals Bi, Sb, Ni, Co, Ti and non-metallic element S. By fine-tuning the element type of the Sn-Ag-Cu alloy main body and fine-tuning the composition of Bi-Sb-Ni-Co-Ti-S doping elements, the solder alloy can reduce the process temperature and improve the tensile strength of the solder alloy , so that the junction of the printed circuit board and electronic components has excellent vibration resistance, and has high reliability of automotive electronics. Each composition of the solder alloy of the present invention will be described below. The solder alloy is also called solder alloy.

The Ag of the solder alloy improves the wettability of the solder, and in addition, the network compound of the intermetallic compound of Ag3Sn is precipitated in the solder matrix to form a precipitation-strengthened alloy, thereby improving the tensile strength of the solder alloy. In one embodiment, the Ag content is 1-4%. When the Ag content is less than 1%, the wettability of the solder cannot be improved. The lower limit of the Ag content is preferably 2.0% or more, more preferably 3.3% or more. On the other hand, when the Ag content exceeds 4%, the coarse Ag ₃ Sn intermetallic compound crystallized in the form of primary crystals deteriorates vibration resistance. In addition, the liquidus temperature will also rise. The upper limit of the Ag content is preferably 3.7% or less, more preferably 3.5% or less.

More notably, the Sn-Ag-Cu alloy body can achieve the effect of reducing the process temperature by fine-tuning the element type, and can achieve the effect of reducing the heating temperature of the solder alloy in subsequent applications, and can effectively reduce the overall Ag content. The amount used, and the cost of one more is reduced. Wherein, in one embodiment, in order to solve the Ag ₃ Sn intermetallic compound, the composition of the 1-4% Ag includes an Ag with a nano-scale powder particle size and an Ag with a micro-scale powder particle size. When calculating %, in the composition of 1-4% Ag, the Ag with nano-scale powder particle size is 30%-50%, and the rest is Ag with micro-scale powder particle size.

The Cu of the solder alloy is used to improve the tensile strength of the solder alloy. The Cu content is 0.5 to 1%. When the Cu content is less than 0.5%, the tensile strength cannot be improved. The lower limit of Cu is preferably 0.6% or more, more preferably 0.65% or more. On the other hand, when the Cu content exceeds 0.8%, the coarse Cu ₆ Sn ₅ intermetallic compound crystallized in the form of primary crystals deteriorates the vibration resistance. In addition, the liquidus temperature will also rise. The upper limit of Cu is preferably 0.75% or less. In one embodiment, in order to solve the Cu ₆ Sn ₅ intermetallic compound, the composition of 0.5-1% Cu includes a Cu with nano-scale powder particle size and a Cu with micro-scale powder particle size, in mass % During calculation, in the composition of Cu, the Cu with nano-scale powder particle size is 40%-60%, and the rest is Cu with micro-scale powder particle size.

Bi in the solder alloy is an element necessary for improving the tensile strength of the solder alloy and improving the vibration resistance. In one embodiment, the Bi content is more than 3% and 5.5% or less. In addition, even if Bi is contained, the formation of the fine SnSb intermetallic compound described later is not hindered, and a precipitation-strengthened solder alloy can be maintained. When the Bi content is 4.8% or less, the above effects cannot be sufficiently exhibited. Therefore, the lower limit of the Bi content is preferably 4.9% or more. On the other hand, when the Bi content exceeds 5.5%, the ductility of the solder alloy decreases and becomes hard, and the vibration resistance deteriorates. The upper limit of the Bi content is preferably 5.3% or less, more preferably 5.2% or less.

Sb in the solder alloy is an element of the solid solution strengthening type that enters the Sn matrix, and is an element of the precipitation and dispersion strengthening type that forms fine SnSb intermetallic compounds in an amount exceeding the solid solution limit in Sn. An element necessary for improving the tensile strength of the alloy and improving the vibration resistance. In one embodiment, the Sb content is more than 1.2% and 5.5% or less. When the Sb content is 1.2% or less, the precipitation of the SnSb intermetallic compound is insufficient, and the above-mentioned effects cannot be exhibited. The lower limit of the Sb content is preferably 1.6% or more, more preferably 3.0% or more, and particularly preferably 4.8% or more. On the other hand, when the Sb content exceeds 5.5%, the solder alloy becomes hard, and there is a possibility that the vibration resistance will deteriorate. The upper limit of the Sb content is preferably 5.3% or less, more preferably 5.2% or less.

Ni in the solder alloy is uniformly dispersed in the intermetallic compound precipitated near the joint interface between the electrode and the solder alloy, and the intermetallic compound layer is modified to suppress the fracture at the joint interface between the electrode and the solder alloy. In one embodiment, the Ni content is 0.01% or more and less than 0.1%. In this way, the failure mode is transferred to the failure mode in the solder alloy near the intermetallic layer. When the Ni content is less than 0.01%, the above effects cannot be exhibited. The lower limit of the Ni content is preferably 0.02% or more, more preferably 0.03% or more. On the other hand, when the Ni content is 0.1% or more, the melting point of the solder alloy becomes high, and it is necessary to change the temperature setting at the time of solder bonding. The upper limit of the Ni content is preferably 0.09% or less, more preferably 0.05% or less.

Co in the solder alloy is an element for enhancing the effect of Ni. In one embodiment, the Co content is 0.1% or less. When the Co content is 0.001% or less, the above effects cannot be exhibited. The lower limit of the Co content is preferably 0.002% or more, more preferably 0.004% or more. On the other hand, when the Co content exceeds 0.1%, the melting point of the solder alloy becomes high, and the temperature at the time of solder bonding must be changed. degree setting. The upper limit of the Co content is preferably 0.05% or less, more preferably 0.012% or less. If Co is not added, other elements, such as Ti, can also be added to obtain suitably similar effects.

Ti of the solder alloy. Ti in the solder alloy is an element for enhancing the effects of Co and Ni. In one embodiment, the Ti content is 0.001% or more and 0.1% or less. When the Ti content is 0.001% or less, the above effects cannot be exhibited. The lower limit of the Ti content is preferably 0.002% or more, more preferably 0.004% or more. On the other hand, when the Ti content exceeds 0.8%, the melting point of the solder alloy becomes high, and it is necessary to change the temperature setting at the time of solder bonding. The upper limit of the Ti content is preferably 0.05% or less, more preferably 0.08% or less. Wherein, when calculated in mass %, in the composition of Ti, the Ti with nano-scale powder particle size is more than 50%, and the rest is Ti with micro-scale powder particle size.

S in the solder alloy is an element for improving the compatibility and tolerance of the process with the effects of Sb and Ni. By doping a small amount of non-metallic element S in the main body of the Sn-Ag-Cu alloy, and fine-tuning the composition of the S doping element, the process compatibility of different elements and the tolerance of process condition variation can be improved. In one embodiment, the S content is 0.001% or more and 0.1% or less. When the S content is 0.001% or less, the above effects cannot be exhibited. The lower limit of the S content is preferably 0.002% or more, more preferably 0.004% or more. On the other hand, when the S content exceeds 0.01%, the solder alloy becomes hard and there is a possibility that the vibration resistance will deteriorate. The upper limit of the S content is preferably 0.05% or less, more preferably 0.01% or less.

In this solder alloy, the composition satisfies: 0.020%≦Ni+Co≦0.10% (1)

In the above formula (1), Ni and Co represent their respective contents (mass %) in the solder alloy. In the solder alloy of the present invention, it is necessary to suppress an undesired form in the failure mode of the solder joint, that is, the fracture of the bonding interface with the electrode. In order to fully exert this effect, the lower limit of the total amount of Ni and Co is preferably 0.020% or more, more preferably 0.042% or more. The upper limit of the total amount of Ni and Co is preferably 0.105% or less, more preferably 0.098% or less, and even more preferably 0.09% or less, in order to suppress the rise in melting point and allow the formation of solder joints under conventional reflow conditions. , the best is below 0.050%.

In this solder alloy, the composition satisfies: 9%≦Sb+Bi≦10% (2)

In the above formula (2), Bi and Sb represent their respective contents (mass %) in the solder alloy. In the solder alloy of the present invention, by increasing the total amount of Sb and Bi, crack propagation in the solder alloy is suppressed, the tensile strength of the solder alloy is improved, and the vibration resistance is further improved. In order to fully exert this effect, the lower limit of the total amount of Sb and Bi is preferably 9.1% or more, more preferably 9.6% or more, still more preferably 9.7% or more, and particularly preferably more than 9.8%. The upper limit of the total amount of Sb and Bi is preferably 10% or less from the viewpoint of suppressing crack propagation in the solder alloy without making the solder alloy too hard.

In order to increase the tensile strength, the contents of Sb and Bi are increased, and since the contents of Ni and Co are relatively small, it is conceivable that the vibration resistance cannot be improved. Therefore, by adjusting the balance of Ni and Co contents for suppressing fracture at the interface between the electrodes of the printed wiring board and the solder alloy, Bi and Sb contents for suppressing crack propagation in the solder alloy, and the like, it is possible to The tensile strength and vibration resistance of the solder alloy are improved, resulting in higher reliability.

In this solder alloy, the composition satisfies 0.002%≦Ti+S≦0.02% (3)

In the above formula (3), Ti and S represent their respective contents (mass %) in the solder alloy. In the solder alloy of the present invention, the balance of tensile strength and vibration resistance can be maintained as long as the contents of Ti and S are not excessively increased from the viewpoint of more adequately responding to the expansion of the mounting area of the substrate. The contents of Ni and Co do not decrease relative to the contents of Ti and S, and the tensile strength of the solder alloy does not become too high. When the Ni and Co contents are appropriate, breakage at the interface between the electrode and the solder alloy can be suppressed, the melting point of the solder alloy can be suppressed from rising, soldering can be performed without problems, and deterioration of vibration resistance can be suppressed. In this way, the total content of Ni and Co for suppressing the increase of the melting point of the solder alloy, and for suppressing the fracture at the interface between the printed circuit board and the solder alloy, and for increasing the tensile strength and suppressing the crack propagation in the solder alloy are adjusted. The total content of Ti and S A balance of the two should result in higher reliability. Therefore, it is more desirable to satisfy the formula (3) in addition to the above-mentioned formulas (1) and (2).

Except for the above-mentioned elements, the remainder of the solder alloy is Sn. The remainder of the solder alloy of the present invention is Sn, and an unavoidable smaller amount of impurities other than this element may be contained. Even if it contains unavoidable impurities, this effect will not be affected.

The solder paste of the present invention, also referred to as solder paste, is a mixture of solder powder and flux having the above-mentioned solder alloy composition. The shape of the lead-free solder of the present invention can be used not only for solder paste, but also for forming solder in the shape of balls, pellets, spacers, etc., wire solder, and flux-cored soldier. The flux used in the present invention is not particularly limited as long as it can be soldered by an ordinary method. Therefore, what is necessary is just to use what mixes rosin, an organic acid, an active agent, and a solvent suitably, which are generally used. In the present invention, the compounding ratio of the metal powder component and the flux component is not particularly limited. It is preferable that the metal powder composition of the solder alloy: 80-90 mass %, and the flux composition: 10-20 mass %. The effect of reducing the process temperature and the heating temperature of the subsequent application of the solder paste to the solder alloy can be achieved by fine-tuning the element type, and the overall usage amount of Ag can be effectively reduced, which further reduces the cost.

In one embodiment, the fabrication of a low-temperature solder alloy for automotive electronics includes: first melting 99.9% Sn at 400° C., then adding 3.50% Ag, 0.70% Cu, 3% Bi, 1.50% Sb, and 0.05% Ni in sequence element. After the alloy liquid completely dissolves all the elements, set the natural gas heating furnace to 320 ℃, and add a trace amount of antioxidants and the content of 0.002%≦Ti+S≦0.02%. After using a thermocouple to measure the liquid alloy at 320°C, pick up a small amount of liquid alloy and put it into an aluminum mold to make a tin block for spectrometer testing. The rest of the liquid alloy is slowly poured into a water-cooled mold to make tin bars and tin powder. Detected by X-ray diffractometer (Rikagu D/max-2200/PC), and then compared with the diffraction peak of JCPDS standard diffraction angle, it was found that in addition to Sn element, Ag ₄ Sn, CuTi were produced ₂ , Ag ₃ Sb and other three kinds of metal compounds. FIG. 1 shows the X-ray diffraction results of the low-temperature solder powder for vehicle use of the present invention. FIG. 2 is the appearance of the tin powder of the present invention magnified by a thousand times under a field emission electron microscope (Scanning electronic microscopy, SEM). After SEM observation, it is confirmed that most of the air-sprayed powders are in a circular shape and there is no other residue, and solder paste can be started. In the detection of the melting point of solder used in vehicles, it is estimated that the tin powder begins to melt at 208°C and completely melts before 227°C, which is lower than the melting point of 227°C of general SAC305. Mix tin powder and flux paste in different proportions, vacuumize to remove foam, and refrigerate to 0°C~10°C after removing foam. After that, it was taken out for unsplicing, and the viscosity was measured using a viscometer (PCU-205, Malcom). When mixed with 90.0% tin powder and 10.0% flux paste, the viscosity can reach 270.3 (Pa.S).

The solder joint of the present invention is suitable for the connection between the integrated circuit chip in the semiconductor package and its substrate, or the connection between the semiconductor package and the printed wiring board. Here, the "welded joint" refers to the joint portion of the electrodes. The above-mentioned solder paste was printed on a substrate using the following metal mask, and various array packages were mounted on the printed substrate. Then, welding is performed to form a welded joint.

The production method of the solder alloy of the present invention may be carried out in accordance with the usual method. In the Sn-Ag-Cu alloy body, the effect of reducing the process temperature is achieved by fine-tuning the element type of Ag, and by doping a small amount of non-metallic element S, fine-tuning the composition of S doping elements can improve different Process compatibility of elements and tolerance for process condition variation. The bonding method using the solder alloy of the present invention may be performed according to a normal method, for example, using a reflow method. In addition, when joining using the solder alloy of the present invention, the structure can be further refined in consideration of the cooling rate during solidification. For example, the welded joint is cooled at a cooling rate of 2 to 3°C/s or more. Other joining conditions can be appropriately adjusted according to the alloy composition of the solder alloy.

The solder alloy of the present invention has high tensile strength and excellent vibration resistance, and is suitable for circuits used in vehicle-mounted circuits where vibrations are transmitted.

In order to solve the intermetallic compound, the present invention includes a metal powder with a nano-scale powder particle size and a metal powder with a micro-scale powder particle size in the composition of Ag and Cu. When calculated in mass %, in the composition of Ag, the Ag with nano-scale powder particle size is 30~50% Above, the rest is Ag with a micron-scale powder particle size. When calculated in mass %, in the composition of Cu, the Cu with nano-scale powder particle size is more than 40-60%, and the rest is Cu with micro-scale powder particle size.

Although the present invention has been disclosed by the preferred embodiment, it is not intended to limit the present invention, and any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. As explained above, various modifications and changes can be made without destroying the spirit of the invention. Therefore, the protection scope of the present invention should be determined by the scope of the appended patent application.

Claims (10)

A solder alloy comprising, in mass %, Ag: 1 to 4%, Cu: 0.5 to 1%, Bi: more than 3% and 5.5% or less, Sb: more than 1.2% and 5.5% or less, Ni : 0.01% or more and less than 0.1%, Co: 0.1% or less, Ti: 0.001% or more and 0.1% or less, S: 0.001% or more and 0.1% or less, and the remainder is an alloy composition composed of Sn; The composition of Cu includes a Cu with a nano-scale powder particle size and a Cu with a micro-scale powder particle size. In the composition of Ti, the Ti with a nano-scale powder particle size is more than 50%, and the rest It is Ti with micron-scale powder particle size. The solder alloy according to claim 1, wherein, when calculated in mass %, in the composition of Cu, the Cu with nanometer-scale powder particle size is 40%-60%, and the rest is with micron-level powder particle size of Cu. The solder alloy as claimed in claim 1, wherein the Ag composition includes an Ag having a nano-scale powder particle size and an Ag having a micro-scale powder particle size. The solder alloy according to claim 3, wherein, when calculated in mass %, in the Ag composition, the Ag with nano-scale powder particle size is 30% to 50%, and the rest is with micron-scale powder particle size of Ag. The solder alloy according to claim 1, wherein the composition of the solder alloy satisfies the following equations (1) to (2), 0.020%≦Ni+Co≦0.10% (1) 9%≦Sb+Bi≦10% (2) In the above formulas (1) to (2), Ni, Co, Bi, and Sb represent the contents (mass %) of each element in the solder alloy. The solder alloy according to claim 1, wherein the composition of the solder alloy satisfies 0.002%≦Ti+S≦0.02%. The above-mentioned Ti and S represent the content (mass %) of each element in the solder alloy. The solder alloy according to claim 1, wherein the composition of the solder alloy satisfies the following equations (1) to (3), 0.020%≦Ni+Co≦0.10% (1) 9%≦Sb+Bi≦10% (2) 0.002%≦Ti+S≦0.02% (3) In the above equations (1) to (3), Ni, Co, Bi, Sb, Ti and S represent the content (mass) of each element in the solder alloy %). A solder paste is characterized in that it has the solder alloy as described in claim 1. The solder paste according to claim 8, wherein the metal powder composition of the solder alloy: 80-90 mass %, and the flux composition: 10-20 mass %. A solder joint is characterized in that it has the solder alloy as described in claim 1.

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