JP6119912B1 - Solder alloys, solder balls and solder joints - Google Patents

Abstract

Kind Code: A1 A solder alloy having excellent wettability to prevent poor soldering, having high joint strength after soldering, suppressing breakage at the joint interface, and further suppressing EM generation. provide. In order to ensure long-term reliability after bonding as well as reliability during bonding, Bi: 0.1% or more and less than 2.0%, Cu: 0.1-1.0. %, Ni: 0.01 to 0.20%, Ge: 0.006 to 0.09%, and the balance is Sn, and the following formulas (1) and (2) are satisfied. 72 × 10 −6 ≦ Ge / Sn ≦ 920 × 10 −6 (1) 0.027 ≦ (Bi × Ge) / (Cu × Ni) ≦ 2.4 (2) Formulas (1) and (2) Among them, Bi, Ge, Cu, Ni, and Sn each represent the content (% by mass) in the solder alloy. [Selection] Figure 1

Description

  The present invention relates to a solder alloy, a solder ball, and a solder joint capable of passing a current having a high current density.

In recent years, electronic devices having solder joints such as a CPU (Central Processing Unit) have been required to be smaller and have higher performance. As a result, the current density per terminal of the semiconductor element mounted on the electronic device tends to increase. In the future, the current density is said to reach about 10 ⁴ to 10 ⁵ A / cm ² . As the current density increases, electromigration occurs at the solder joint. As electromigration proceeds, the solder joint breaks.

  Electromigration (hereinafter referred to as “EM” as appropriate) is a phenomenon as described below. First, the atoms constituting the solder joint collide with electrons that generate current, and the momentum is transmitted from the electrons to the atoms. Atoms with increased momentum move to the anode side of the solder joint along the electron flow. As atoms move to the anode side of the solder joint, a vacancy is created on the cathode side of the solder joint. Such voids gradually expand and voids are generated. As the void grows, the solder joint eventually breaks. Thus, EM is becoming a bigger problem than the recent increase in current density.

  By the way, as a conventional lead-free solder alloy, Sn-Cu solder alloy and Sn-Ag-Cu solder alloy have been widely used. Since these solder alloys have a large effective charge number of Sn as a main component, EM is likely to occur. Solder joints formed of these alloys may break when a current having a high current density is applied for a long time. In addition to these, there are several breakage factors of solder joints, but various alloys have been studied in order to suppress the breakage of solder joints.

  Patent Document 1 discloses a Sn—Bi—Cu—Ni based solder alloy containing 2% by mass or more of Bi in order to improve the tensile strength and wettability of the solder alloy and suppress breakage of the solder joint.

  In Patent Document 2, by improving the wettability, even if an aging treatment is performed after solder joining, the joint strength does not decrease, and in order to maintain high joint strength and improve reliability, Ge is added to the solder alloy. An added Sn—Cu—Ni—Bi—Ge based solder alloy is disclosed.

  Patent Document 3 also discloses a solder alloy of the same alloy type as Patent Document 2. In patent document 3, in order to suppress the fall of the impact resistance of a solder alloy, Bi content is restrained to less than 1%. Further, the solder alloy described in Patent Document 3 contains Ge at the same time as P in order to obtain excellent impact resistance of the solder joint by improving wettability.

JP 2014-097532 A International Publication No. 2015/166945 Pamphlet International Publication No. 2009/131114 Pamphlet

  However, since the solder alloy described in Patent Document 1 contains 2% or more of Bi, the strength of the solder alloy itself is too high, and breakage at the joint interface is promoted. Here, a mobile product or the like is unavoidably dropped when being carried, and when an impact or the like is applied to the joint at that time, the mobile product is destroyed at the joint interface. Therefore, even during the strength test, a fracture mode in which the fracture occurs at the bonding interface (hereinafter referred to as “breakage M” as appropriate) must be avoided. In Patent Document 1, destruction at the bonding interface is inevitable.

  The invention described in Patent Document 2 aims to improve the joint strength of the solder joint after the aging treatment, but does not aim to suppress the generation of EM. Even if the reliability of the soldered joint after the aging treatment is improved, it is difficult to say that a means for suppressing the movement of the metal atom which is the cause of EM is provided. For this reason, when a current having a high current density is passed through a solder joint using the solder alloy described in Patent Document 2, the generation of EM cannot be sufficiently suppressed even when the wettability is improved by the addition of Ge.

  Moreover, although the solder alloy of patent document 3 aims at the improvement of impact resistance, since it does not aim at suppressing generation | occurrence | production of EM, it suppresses generation | occurrence | production of EM like patent document 2. No means to do it. For this reason, generation | occurrence | production of EM cannot fully be suppressed only by containing P and Ge.

  As described above, the solder alloys described in Patent Documents 1 to 3 may improve the joint strength and impact resistance at high temperatures due to the improvement of wettability. Further study is necessary to suppress the occurrence.

  An object of the present invention is to have excellent wettability in order to prevent soldering failure, to suppress breakage at the joint interface, to have high joint strength of the solder joint after soldering, and also to suppress generation of EM. Thus, it is to provide a solder alloy that can ensure long-term reliability after bonding as well as reliability during bonding.

  The inventors of the present invention have made extensive studies so that the Sn—Bi—Cu—Ni—Ge based solder alloy has high wettability and bonding strength and can suppress generation of EM.

  The inventors first attempted to optimize the contents of Cu and Ni in order to improve wettability and bonding strength.

  Then, focusing on the fact that it is necessary to limit the movement of Sn in order to suppress the generation of EM, we have conceived that it is necessary to add distortion to the Sn matrix in order to limit the movement of Sn.

  In order to embody this idea, the present inventors first attempted to optimize the Bi content dissolved in Sn. However, even if the Bi content is controlled and distortion is applied to the Sn matrix, Cu and Ni also form an intermetallic compound with Sn and some distortion occurs in the Sn matrix. For this reason, the strain of the Sn matrix cannot be controlled simply by controlling the Bi content, and a sufficient EM suppression effect cannot be exhibited. Therefore, the present inventors have further studied focusing on Ge that improves wettability.

  As a result, the addition of Ge promotes the distortion of the Sn matrix due to the addition of Bi, and the distortion that prevents the movement of Sn by controlling the ratio of the Sn content to the Ge content with high accuracy. Was found in the Sn matrix, and the knowledge that the generation of EM can be suppressed was obtained. Thus, it was found that in the Sn—Bi—Cu—Ni—Ge based solder alloy, the balance of the content of Ge and Sn is extremely important for exerting the EM suppression effect.

  Also, the product of Ge content and Bi content, which are EM suppression elements (Ba balance of Ge and Bi), and the product of Cu content and Ni content, which is a bonding strength improving element (Cu and Ni balance) In the case where the ratio of is within the predetermined range, knowledge showing high wettability and bonding strength while maintaining the EM suppression effect was obtained.

  Furthermore, it became clear that the wettability deteriorates when the balance between the Ge content and the Sn, Cu, Ni content is not appropriate and is added excessively.

  In addition to this, when all the above-mentioned knowledge is satisfied, the knowledge that the joint interface breakage, which is fatal in soldering, is suppressed was also obtained.

  As a preferable aspect, the knowledge that wettability was further improved and bonding strength was improved by adding a predetermined amount of P was obtained.

The present invention obtained from these findings is as follows.
(1) By mass%, Bi: 0.1% or more and less than 2.0%, Cu: 0.1-1.0%, Ni: 0.01-0.20%, Ge: 0.006-0. A solder alloy having an alloy composition of 09%, the balance being Sn and satisfying the following formulas (1) and (2):
72 × 10 ⁻⁶ ≦ Ge / Sn ≦ 920 × 10 ⁻⁶ (1)
0.027 ≦ (Bi × Ge) / (Cu × Ni) ≦ 2.4 (2)
In the formulas (1) and (2), Bi, Ge, Cu, Ni, and Sn each represent a content (mass%) in the solder alloy.

  (2) The solder composition according to (1), wherein the alloy composition further includes P: 0.1% or less in mass%.

(3) The solder alloy according to (1) or (2), which is used for an electronic device having a joint through which a current having a current density of 5 to 100 kA / cm ² is passed.

(4) A solder ball made of the solder alloy according to any one of (1) to (3).
(5) A solder joint having the solder alloy according to any one of (1) to (3).

FIG. 1 is a graph showing the relationship between formulas (1) and (2) in a Sn—Bi—Cu—Ni—Ge solder alloy. FIG. 2 is an enlarged graph of a portion in FIG. 1 where the range of the formula (1) is 0 to 0.500 and the range of the formula (2) is 0 to 0.000200.

  The invention is described in more detail below. In this specification, “%” regarding the solder alloy composition is “% by mass” unless otherwise specified.

1. Alloy composition (1) Bi: 0.1% or more and less than 2.0%,
Bi is an element necessary for suppressing the generation of EM. Since Bi dissolves in Sn, it is possible to suppress the movement of Sn by adding strain to the Sn matrix. If the Bi content is less than 0.1%, the amount of distortion of the Sn matrix is small and the generation of EM cannot be sufficiently suppressed. For this reason, the lower limit of Bi content is 0.1% or more, preferably 0.2% or more, more preferably 0.3% or more, still more preferably 0.6% or more, Preferably it is 1.0% or more. On the other hand, if the Bi content is 2.0% or more, the solder alloy becomes too hard due to the increase in strength due to Bi, which may promote joint interface destruction. For this reason, the upper limit of Bi content is less than 2.0%, Preferably it is 1.9% or less, More preferably, it is 1.8% or less, More preferably, it is 1.7% or less.

(2) Cu: 0.1 to 1.0%
Cu is an element necessary for improving the joint strength of the solder joint. When the Cu content is less than 0.1%, the bonding strength is not sufficiently improved. For this reason, the minimum of Cu content is 0.1% or more, Preferably it is 0.3% or more, More preferably, it is 0.5% or more. On the other hand, when the Cu content exceeds 1.0%, the wettability of the solder alloy deteriorates. Further, when the wettability is deteriorated, the bonding area is decreased, the current density is increased, and the generation of EM may be promoted. For this reason, the upper limit of the Cu content is 1.0% or less, preferably 0.9% or less, and more preferably 0.8% or less.

(3) Ni: 0.01 to 0.20%
Ni, like Cu, is an element necessary for improving the joint strength of solder joints. When the Ni content is less than 0.01%, the bonding strength is not sufficiently improved. For this reason, the minimum of Ni content is 0.01% or more, Preferably it is 0.02% or more, More preferably, it is 0.03% or more. On the other hand, if the Ni content exceeds 0.20%, the wettability of the alloy deteriorates. In addition, like Cu, the generation of EM may be promoted. For this reason, the upper limit of Ni content is 0.20% or less, Preferably it is 0.15% or less, More preferably, it is 0.10% or less.

(4) Ge: 0.006 to 0.09%
Ge is an element necessary for improving the wettability of the solder alloy and suppressing the generation of EM. Ge can suppress the generation of EM by promoting the distortion of the Sn matrix due to Bi and inhibiting the movement of Sn. If the Ge content is less than 0.006%, these effects are not sufficiently exhibited. The lower limit of the Ge content is 0.006% or more, preferably 0.007% or more, and more preferably 0.008% or more. On the other hand, when the Ge content exceeds 0.09%, the wettability deteriorates. In addition, the shear strength deteriorates with this, and the joint interface may break. The upper limit of the Ge content is 0.09% or less, preferably 0.05% or less, more preferably 0.03% or less, still more preferably 0.02% or less, and particularly preferably 0. .01% or less.

(5) (1) Formula Even if the solder alloy of this invention satisfy | fills the range of above-mentioned (1)-(4), it is necessary to satisfy | fill following (1) Formula.
72 × 10 ⁻⁶ ≦ Ge / Sn ≦ 920 × 10 ⁻⁶ (1)
In the formula (1), Ge and Sn each represent a content (% by mass) in the solder alloy.

  The formula (1) represents the ratio between the Ge content and the Sn content. In the present invention, in addition to making the Ge content within the above-mentioned range with respect to the total mass of the solder alloy, the movement of Sn can be controlled by controlling the Ge content with respect to the Sn content with high accuracy. It is suppressed and the EM suppression effect can be exhibited. In the case of satisfying the formula (1) in the Sn—Bi—Cu—Ni—Ge based solder alloy, the distortion of the Sn matrix due to the addition of Bi occurs in a direction perpendicular to the direction in which electrons flow. It is presumed that the movement of Sn along can be prevented.

Therefore, even if Cu, Ni, Bi and Ge all have an alloy composition within the range described in the above (1) to (4), Ge / Sn is from 72 × 10 ^{−6 to} 920 × 10 ^−6. If it deviates even a little, the distortion applied to the Sn matrix cannot be controlled. For this reason, the formula (1) is extremely important for suppressing the generation of EM in the Sn—Bi—Cu—Ni—Ge solder alloy.

The lower limit of the formula (1) is preferably 81 × 10 ⁻⁶ or more, more preferably 90 × 10 ⁻⁶ or more, and particularly preferably 101 × 10 ⁻⁶ or more in order to promote the distortion of the Sn matrix. is there. The upper limit of the formula (1) is preferably 917 × 10 ⁻⁶ or less, more preferably 300 × 10 ⁻⁶ or less, and particularly preferably 103 × 10 ⁻⁶ or less in order to suppress deterioration of wettability. .

(6) (2) Formula The solder alloy of this invention needs to satisfy | fill (2) Formula, even if it is a case where the range of above-mentioned (1)-(4) is satisfy | filled.
0.027 ≦ (Bi × Ge) / (Cu × Ni) ≦ 2.4 (2)
(2) In the formula, Bi, Ge, Cu, and Ni each represent a content (% by mass) in the solder alloy.

  The expression (2) expresses the ratio of the product of Ge content and Bi content, which are EM suppressing elements, and the product of Cu content and Ni content, which are bonding strength improving elements. In the formula (2), the product of the Ge content and the Bi content represents the balance between the Ge content and the Bi content in the solder alloy. The product of the Cu content and the Ni content represents the balance between the Cu content and the Ni content in the solder alloy.

  The reason why the effect of the present invention can be exhibited when the solder alloy of the present invention satisfies the expression (2) is not clear, but is presumed as follows.

  The solder alloy of the present invention has excellent wettability, the joint strength of the solder joint after soldering is high, the fracture mode is made appropriate, and the occurrence of EM can also be suppressed. Among the constituent elements of the solder alloy of the present invention, Cu and Ni are elements that contribute to improving the bonding strength, while Bi and Ge are elements that are considered to suppress the generation of EM.

  Further, when the wettability deteriorates due to the solder alloy containing Cu and Ni in a predetermined amount or more, the bonding area with the electrode is reduced, the current density is increased, and EM is generated. Therefore, generation of EM can be suppressed indirectly by controlling the contents of Cu and Ni. On the other hand, Bi and Ge add strain to the Sn matrix and suppress the movement of Sn, so that the generation of EM can be suppressed directly. However, excessive addition of Ge deteriorates wettability and causes an excess of Bi. Addition promotes fracture at the bonding interface.

  Thus, the Cu and Ni group and the Bi and Ge group have different behaviors in the solder alloy of the present invention. In the Sn-Bi-Cu-Ni-Ge solder alloy, in order to satisfy all of the wettability, the joint strength of the solder joint, the suppression of EM generation, and the optimization of the fracture mode at the same time, as in the solder alloy of the present invention The balance of Cu and Ni in the solder alloy and the balance of Bi and Ge must be accurately controlled so as to satisfy the formula (2) as a whole of the solder alloy.

  The lower limit of the formula (2) is preferably 0.067 or more, more preferably 0.08 or more, from the viewpoint of suppressing the wettability and bonding strength deterioration due to the relative reduction of Cu and Ni, and more preferably 0.08 or more. Preferably it is 0.2 or more, Most preferably, it is 0.28 or more. The upper limit of the formula (2) is preferably 2.0 or less, more preferably 1.333 or less, from the viewpoint of suppressing deterioration of wettability and suppressing reduction in joint strength due to embrittlement of the solder alloy. More preferably, it is 0.7 or less, and particularly preferably 0.507 or less.

  As described above, the present invention makes the content of the essential element within the above-mentioned range and satisfies both the formulas (1) and (2), so that the wettability is excellent and the bonding strength is high. Generation | occurrence | production can fully be suppressed and a destruction mode can be made appropriate.

(7) P: 0.1% or less P is an optional element that can suppress oxidation of Sn and improve wettability. If the P content does not exceed 0.1%, the fluidity of the solder alloy on the solder surface is not hindered. The P content is 0.1% or less, preferably 0.01% or less, and more preferably 0.008% or less. On the other hand, in order to exert these effects, the lower limit of the P content is preferably 0.001% or more.

  The balance of the solder alloy according to the present invention is Sn. In addition to the aforementioned elements, inevitable impurities may be contained. Even when inevitable impurities are contained, the above-mentioned effects are not affected. As will be described later, even if an element not contained in the present invention is contained as an unavoidable impurity, the above-described effect is not affected.

2. Solder Joint The solder joint according to the present invention is suitable for use in connecting an IC chip in a semiconductor package and its substrate (interposer), or connecting a semiconductor package and a printed wiring board. Here, the “solder joint” refers to an electrode connection.

3. Applications The solder alloy according to the present invention can be used in the form of a preform, wire, solder paste, solder ball (also referred to as “solder ball”), and is preferably used as a solder ball. When used as a solder ball, the diameter is preferably in the range of 1 to 1000 μm.

What is necessary is just to perform the manufacturing method of the solder alloy based on this invention in accordance with a conventional method.
What is necessary is just to perform the joining method using the solder alloy which concerns on this invention according to a conventional method, for example using a reflow method. The melting temperature of the solder alloy in the case of performing flow soldering may be about 20 ° C. higher than the liquidus temperature. Moreover, when joining using the solder alloy which concerns on this invention, it is preferable from a viewpoint of refinement | miniaturization of a structure to consider the cooling rate at the time of solidification. For example, the solder 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 according to the present invention can produce a low α-ray alloy by using a low α wire as a raw material. Such a low α-ray alloy can suppress soft errors when used for forming solder bumps around the memory.

  A solder joint was formed using a solder alloy having the alloy composition shown in Table 1. The shear strength test, fracture M, and EM test of the formed solder joint were evaluated. In addition, the wettability of the solder alloy was also evaluated. Each evaluation method is as follows.

-Shear strength Cu electrode (hereinafter simply referred to as "Cu electrode") in which the solder alloy shown in Table 1 was subjected to OSP treatment of a PCB having a substrate thickness of 1.2 mm and an electrode size of 0.24 mm in diameter. And then soldered. For soldering, a solder ball having a diameter of 0.3 mm made from each solder alloy is manufactured in advance, and the water-soluble flux is applied onto the substrate using a water-soluble flux (manufactured by Senju Metal Industry Co., Ltd .: WF-6400). After application, the ball was mounted. Thereafter, soldering was performed by a reflow method with a reflow profile at a peak temperature of 245 ° C. and a cooling rate of 2 ° C./s to obtain a sample on which solder bumps were formed.

  The shear strength (N) of this sample was measured under a condition of 1000 mm / sec using a shear strength measuring device (DAGE: SERIES 4000HS). A Cu electrode having a shear strength of 3.5 N or more was judged as “◯”, and a shear strength of less than 3.5 N was judged as “X”.

・ Destruction M
The fracture surface after the shear test was observed with a stereomicroscope. When the solder bump was broken at the joint interface, the break M was x (NG), and when broken at other locations, the break M was O (OK).

・ Wettability test
Similar to the sample used in the shear strength test described above, a wetting spread test was performed in the following order of “1.” and “2.” using a solder ball having a diameter of 0.3 mm. The substrate material used is a glass epoxy substrate (FR-4) having a thickness of 1.2 mm.

  1. Using the above-mentioned substrate on which a slit-shaped Cu electrode of 0.24 mm × 16 mm was formed, flux WF-6400 manufactured by Senju Metal Industry Co., Ltd. was printed on 0.24 mmφ × 0.1 mm thickness, and solder balls were mounted. Reflow was performed under the condition that the temperature was kept for 40 seconds in a temperature range of ℃ or higher and the peak temperature was 245 ℃.

2. Using a stereomicroscope, the wet spread area was measured, and a wet spread of 0.75 mm ² or more was determined as “◯”. A wetting spread of less than 0.75 mm ² was determined as “x”.

EM test For the EM test sample, the solder balls shown in Table 1 having a diameter of 0.3 mm were used similarly to the sample used in the above-described shear strength test, and the size of 13 mm × 13 mm having a Cu electrode having a diameter of 0.24 mm was used. Reflow soldering was performed on the package substrate using a water-soluble flux to produce a package. Thereafter, a solder paste is printed on a glass epoxy substrate (FR-4) having a size of 30 mm × 120 mm and a thickness of 1.5 mm, and the package produced as described above is mounted and held at a temperature range of 220 ° C. or higher for 40 seconds, Reflow was performed under conditions where the peak temperature was 245 ° C., and a sample was prepared.

  In the EM test, the sample prepared above is connected to a compact variable switching power supply (manufactured by Kikusui Electronics Co., Ltd .: PAK-A), and a current is passed in a silicon oil bath maintained at 150 ° C. During the current application, the electrical resistance of the sample is continuously measured, and when the initial resistance value is increased by 20%, the test is terminated, and the time until the test is terminated is “◯”, and less than 200 hours is “X”. Judged.

  The evaluation results are shown in Table 1.

  As shown in Table 1, in Examples 1-12, in order to satisfy all the requirements of the present invention in any alloy composition, generation of EM was suppressed, excellent wettability, and high shear strength were obtained. . Further, with respect to the fracture M, no fracture was observed at the bonding interface.

  On the other hand, in Comparative Example 1, the Bi content was large, the fracture at the bonding interface was observed, and the fracture M was “x”. In Comparative Example 1, although Ge / Sn is less than the lower limit of the formula (1), it is considered that EM was maintained by excessive addition of Bi.

  In Comparative Example 2, the EM was inferior because the Bi content was small. Since the comparative example 3 had much Cu content, the wettability was inferior. In Comparative Example 4, the bonding strength was poor because the Cu content was small. Since Comparative Example 5 had a high Ni content, the wettability was poor. In Comparative Example 6, since the Ni content was small, the shear strength was inferior. Since the comparative example 7 had little Ge content and Ge / Sn was less than the minimum of Formula (1), EM was inferior. In Comparative Example 8, since the Ge content was large, the wettability deteriorated, and the shear strength and fracture M were also “x”. In Comparative Example 9, EM was inferior because Ge / Sn was less than the lower limit of the formula (1). In Comparative Example 10, since Ge / Sn and (Bi × Ge) / (Cu × Ni) exceeded the upper limits of the formulas (1) and (2), the wettability was inferior.

  The results of Table 1 will be further described with reference to FIG. 1 and FIG. FIG. 1 is a graph showing the relationship between formulas (1) and (2) in a Sn—Bi—Cu—Ni—Ge solder alloy. FIG. 2 is an enlarged graph of a portion in FIG. 1 where the range of the formula (1) is 0 to 0.500 and the range of the formula (2) is 0 to 0.000200. In each figure, ● is an example that satisfies all the requirements of the present invention, and ○ is a comparative example that does not satisfy either of the requirements of the formulas (1) and (2) of the present invention.

  As is clear from FIG. 1, the present invention satisfies the formulas (1) and (2), and as shown in Table 1, excellent wettability, high bonding strength, proper destruction M and EM generation are suppressed. It became clear that I was satisfied at the same time. As is clear from FIG. 2, when Example 2 and Comparative Example 2 are compared, and Example 10 and Comparative Example 9 are compared, Comparative Example 2 and Comparative Example 9 are slightly less than the ranges of Equations (1) and (2). Therefore, as shown in Table 1, excellent wettability, high bonding strength, proper destruction M, and suppression of EM generation could not be satisfied at the same time.

  From the above, for the Sn—Bi—Cu—Ni—Ge solder alloy, making each content range an appropriate range and satisfying the formulas (1) and (2) with one alloy composition, This is extremely important for simultaneously satisfying excellent wettability, high bonding strength, proper fracture M and suppression of EM generation.

The solder alloy according to the present invention can be used not only for CPUs but also for devices that handle high voltages and large currents, such as photovoltaic power conversion devices and large current inverters for industrial motors.

Claims (5)

In mass%, Bi: 0.1% or more and less than 2.0%, Cu: 0.1 to 1.0%, Ni: 0.01 to 0.20%, Ge: 0.006 to 0.09%, A solder alloy characterized in that the balance has an alloy composition of Sn and satisfies the following formulas (1) and (2).
72 × 10 ⁻⁶ ≦ Ge / Sn ≦ 920 × 10 ⁻⁶ (1)
0.027 ≦ (Bi × Ge) / (Cu × Ni) ≦ 2.4 (2)
In the formulas (1) and (2), Bi, Ge, Cu, Ni, and Sn each represent a content (mass%) in the solder alloy.   2. The solder alloy according to claim 1, wherein the alloy composition further includes P: 0.1% or less by mass%. The solder alloy according to claim 1 or 2, which is used for an electronic device having a joint through which a current having a current density of 5 to 100 kA / cm ² is passed.   A solder ball comprising the solder alloy according to claim 1. The solder joint which has the solder alloy of any one of Claims 1-3.

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