Solder alloys, solder balls and solder joints

Abstract

The present invention employs a lead-free and antimony-free solder alloy having an alloy composition comprising Ag: 1.0 to 4.0 wt%, Cu: 0.1 to 1.0 wt%, Bi: 0.1 to 9.0 wt%, Ni: 0.005 to 0.3 wt%, Ge: 0.001 to 0.015 wt%, and the remainder being Sn.

Description

Technical Field

[0001] The present invention relates to a lead-free and antimony-free solder alloy, solder ball, and solder joint. This application claims priority based on U.S. Provisional Patent Application No. 63 / 115,611 filed in the United States on November 19, 2020, the contents of which are incorporated herein by reference. Prior Art

[0002] In recent years, electronic equipment has been required to be more integrated, larger in capacity, and faster in speed. For example, semiconductor packages such as QFP (Quad Flat Package) are being used, and the pursuit of higher integration and functionality at the semiconductor chip level is underway. The manufacturing system of QFP adopts a packaging process, which is to bond the silicon chip die cut from the silicon wafer to the lead frame.

[0003] In a QFP package, which is obtained by bonding tiny electrodes such as a BGA (Ball Grid Array), a silicon chip and a lead frame are bonded with solder alloy grains to form a solder joint. Solder bumps are formed on tiny electrodes in BGAs using solder balls. To use solder balls, adhesive flux is applied to the tiny electrodes, and the solder balls are placed on the flux-coated electrodes. The solder balls are then heated in a reflow oven to melt the solder balls. The molten solder wets the tiny electrodes, forming solder bumps on the tiny electrodes.

[0004] However, in the past, Sn-Ag-Cu solder alloy has been widely used, and is used in the form of solder balls and also for die bonding. When using this solder alloy, recent demands have necessitated improvements in heat cycle resistance, impact resistance, and discoloration resistance. Therefore, various studies have been conducted to improve these properties of the widely used Sn-Ag-Cu solder alloy.

[0005] For example, Patent Document 1 discloses a solder alloy comprising a Sn-Ag-Cu solder alloy containing Ni and Ge as optional elements. This solder alloy exhibits heat cycle resistance when Ni is present, and exhibits impact resistance or discoloration resistance when Ge is present. [Prior Art Literature] [Patent Document]

[0006] [Patent Document 1] Japanese Patent Publication No. 4144415 Summary of the Invention Problems to be Solved by the Invention

[0007] As described above, the solder alloy (Sn-Ag-Cu-Ni-Ge solder alloy) disclosed in Patent Document 1 is an excellent alloy that can simultaneously exhibit three effects: impact resistance, discoloration resistance, and heat cycle resistance. However, it is considered that there is room for further improvement in alloy design.

[0008] Although each element in the solder alloy has an inherent addition meaning, the solder alloy is an integral combination of all constituent elements. Since the constituent elements affect each other, the constituent elements must be contained with good overall balance. In the solder alloy described in Patent Document 1, the contents of each constituent element are individually optimized. At the time of filing the application for Patent Document 1, it was considered to be a sufficient alloy composition to obtain the effects described in Patent Document 1. However, in solder alloys having the same constituent elements, in order to meet recent requirements and improve other characteristics, the contents of each constituent element must be further individually optimized and then contained with good overall balance.

[0009] The invention described in Patent Document 1 presupposes alloy design when placing solder balls on microelectrodes such as BGA. Therefore, when using the Sn-Ag-Cu-Ni-Ge solder alloy for welding, an increase in mechanical strength is required. Also, in this specification, mechanical strength is sometimes described as shear strength and tensile strength.

[0010] Thus, in recent high-integration, high-capacity, and high-speed electronic devices, a solder alloy suitable for die bonding used not only for BGA but also for QFP is required.

[0011] Therefore, an object of the present invention is to provide a lead-free and antimony-free solder alloy, solder ball, and solder joint having a melting point near 230°C and a tensile strength of 50 MPa or more. Means for Solving the Problems

[0012] Solder alloys are composed of two or more elements, and sometimes the effects of each element individually affect the overall properties of the solder alloy. However, as mentioned above, since all the constituent elements are integrated, the constituent elements are interrelated. The present inventors have focused on designing an alloy with improved shear strength. This alloy design is applicable not only to BGA but also to QFP even if it uses the same constituent elements as the solder alloy described in Patent Document 1.

[0013] In the past, when discarded substrates containing lead (Pb) were disused, acid rain sometimes leached the Pb from the substrates and caused it to flow into groundwater. Furthermore, Pb could accumulate in livestock and humans from groundwater, potentially harming them. Therefore, Pb has been designated as a regulated substance under the RoHS Directive. Furthermore, in recent years, due to environmental and health concerns, there has been a growing demand to avoid not only Pb but also Sb, which improves the thermal cycling resistance of Sn-based solder alloys. Consequently, research has been conducted to achieve the desired properties without lead or antimony.

[0014] In a QFP, which is made by joining tiny electrodes such as a BGA (Ball Grid Array), a solder joint is formed by bonding the silicon wafer and the lead frame grains with a solder alloy. In order to improve the wettability with solder and enhance the adhesion strength of the silicon wafer, for example, a backing metal having a Ni layer is formed on the outermost layer. When the outermost Ni layer comes into contact with molten solder, it melts in the molten solder, causing Ni corrosion. To prevent Ni from diffusing into the silicon wafer, a barrier layer, such as Ti, is typically formed on the backing metal to prevent it from diffusing. If Ni corrosion continues and the Ti layer is exposed, the solder alloy's wettability to Ti becomes extremely poor, and the backing metal repels the molten solder. Furthermore, even if a small amount of Ni remains, Ni atoms diffuse into the molten solder, while Ti hardly diffuses into Ni. Consequently, pores at the interface between the Ti layer (which serves as a barrier layer) and the Ni layer increase at the atomic level, significantly reducing the adhesion strength at the interface between the remaining Ni layer and the Ti layer. As a result, the impact resistance and thermal cycling resistance of the joint after die bonding may deteriorate. Therefore, maintaining a residual Ni layer on the backing metal is crucial for die bonding.

[0015] In the present invention, the inventors further studied the significance of adding each constituent element and considered the balance of each constituent element to conduct detailed composition exploration. In the present invention, the inventors have discovered that if the contents of Ag, Cu, Bi, and Ni are appropriate and correct, the difference between the liquidus temperature and the solidus temperature of the solder alloy (hereinafter sometimes referred to as ΔT) will fall within an appropriate range.

[0016] In the present invention, the inventors have also conducted research on miniaturization of intermetallic compounds formed at the bonding interface in order to improve the bonding strength of solder joints. In order to form a compound of Cu and Sn at the bonding interface, the content ratio of Cu and Sn must be within a predetermined range. Furthermore, in the compound of Cu and Sn, it is noted that the miniaturization of the compound can be achieved by substituting part of Cu with Ni. Furthermore, the liquidus temperature of the solder alloy varies significantly depending on the Cu and Ni content. Therefore, research was conducted to control the viscosity during melting and inhibit the growth of Sn compounds to prevent ΔT from becoming too large. The results provide the following insights: By having a well-balanced content of Sn, Cu, and Ni in the Sn-Ag-Cu-Bi-Ni-Ge solder alloy, ΔT can be controlled, resulting in finer intermetallic compounds formed at the bonding interface, and improved shear strength and reliability.

[0017] Furthermore, in the present invention, the inventors have obtained the following knowledge and insights: by adjusting the Ag content within a predetermined range, the precipitation of coarse Ag3Sn can be suppressed, and fine Ag3Sn can be precipitated in the grain boundaries, thereby improving the tensile strength and reliability.

[0018] Furthermore, in the present invention, the inventors have obtained the following knowledge: by adjusting the Bi content to a predetermined range, the optimal mechanical strength for the solder ball can be obtained. Furthermore, the inventors have obtained the following knowledge: if Bi is excessively added, the liquidus temperature is lowered, ΔT is increased, and mechanical strength and the like are reduced due to segregation.

[0019] Furthermore, the present inventors have obtained the following knowledge and insight: by adjusting the Co content to a predetermined range, ΔT can be reduced, the tensile strength can be increased to 50 MPa or more, and the elongation, Poisson's ratio, and linear expansion coefficient can be improved.

[0020] In order to solve the above-mentioned problems, the present invention adopts the following structure. [1] A lead-free and antimony-free solder alloy having an alloy composition comprising 1.0 to 4.0 mass % of Ag, 0.1 to 1.0 mass % of Cu, 0.1 to 9.0 mass % of Bi, 0.005 to 0.3 mass % of Ni, 0.001 to 0.015 mass % of Ge, and the remainder being Sn.

[0021] [2] The solder alloy as described in [1], wherein the alloy composition is Ag: 1.0 to 3.5 mass %. [3] The solder alloy as described in [1] or [2], wherein the alloy composition is Ag: 2.0 to 3.5 mass%. [4] The solder alloy as described in any one of [1] to [3], wherein the alloy composition is Ag: 3.0 to 3.5 mass %. [5] The solder alloy as described in any one of [1] to [4], wherein the alloy composition is Cu: 0.5 to 0.85 mass %. [6] The solder alloy as described in any one of [1] to [5], wherein the alloy composition is Cu: 0.7 to 0.8 mass %. [7] The solder alloy as described in any one of [1] to [6], wherein the alloy composition is Cu: 0.75 to 0.8 mass %. [8] The solder alloy as described in any one of [1] to [7], wherein the alloy composition is Bi: 0.2 to 5.0 mass%. [9] The solder alloy as described in any one of [1] to [8], wherein the alloy composition is Bi: 0.5 to 4.0 mass%.

[10] The solder alloy as described in any one of [1] to [9], wherein the alloy composition is Bi: 1.0 to 3.0 mass%.

[0022]

[11] The solder alloy as described in any one of [1] to

[10] , wherein the alloy composition is Ni: 0.02 to 0.09 mass %.

[12] The solder alloy as described in any one of [1] to

[11] , wherein the alloy composition is Ni: 0.03 to 0.08 mass %.

[13] The solder alloy as described in any one of [1] to

[12] , wherein the alloy composition is Ni: 0.04 to 0.06 mass %.

[14] The solder alloy as described in any one of [1] to

[13] , wherein the alloy composition is Ge: 0.002 to 0.012 mass %.

[15] The solder alloy as described in any one of [1] to

[14] , wherein the alloy composition is Ge: 0.003 to 0.010 mass %.

[16] The solder alloy as described in any one of [1] to

[15] , wherein the alloy composition is Ge: 0.003 to 0.009 mass %.

[0023]

[17] The solder alloy as described in any one of [1] to

[16] , wherein the alloy composition further satisfies 0.3≦Ag / Bi≦3.0. Ag and Bi respectively represent their contents (mass %) in the aforementioned alloy compositions.

[18] The solder alloy as described in any one of [1] to

[16] , wherein the alloy composition further contains Co: 0.001 to 0.1 mass %.

[19] The solder alloy as described in

[18] , wherein the alloy composition is Co: 0.002 to 0.015 mass%.

[20] The solder alloy as described in

[18] or

[19] , wherein the alloy composition is Co: 0.004 to 0.012 mass %.

[21] The solder alloy as described in any one of

[18] to

[20] , wherein the alloy composition is Co: 0.006 to 0.009 mass %.

[0024]

[22] The solder alloy as described in any one of [1] to

[17] , wherein the alloy composition further satisfies 1 <Ag / Bi。 Ag and Bi respectively represent their contents (mass %) in the aforementioned alloy compositions.

[23] A lead-free and antimony-free solder alloy having an alloy composition comprising Ag: 3.5 mass%, Cu: 0.8 mass%, Bi: 1.0 to 2.0 mass%, Ni: 0.05 mass%, Ge: 0.008 mass%, and the remainder being Sn.

[24] A lead-free and antimony-free solder alloy having an alloy composition comprising 3.0 to 4.0 mass % of Ag, 0.7 to 0.9 mass % of Cu, 1.5 mass % of Bi, 0.03 to 0.08 mass % of Ni, 0.006 to 0.009 mass % of Ge, and the remainder being Sn.

[25] A lead-free and antimony-free solder alloy having an alloy composition comprising 3.0 to 4.0 mass % of Ag, 0.7 to 0.9 mass % of Cu, 1.8 mass % of Bi, 0.03 to 0.08 mass % of Ni, 0.006 to 0.009 mass % of Ge, and the remainder being Sn.

[26] The solder alloy as described in any one of [1] to

[17] and

[22] to

[25] , wherein the alloy composition further satisfies 1.2≦Ag / Bi≦3.0. Ag and Bi respectively represent their contents (mass %) in the aforementioned alloy compositions.

[0025]

[27] The solder alloy as described in any one of [1] to

[17] , wherein the alloy composition further satisfies Ag / Bi≦1. Ag and Bi respectively represent their contents (mass %) in the aforementioned alloy compositions.

[28] A lead-free and antimony-free solder alloy having an alloy composition comprising Ag: 2.0 mass%, Cu: 0.8 mass%, Bi: 3.0 to 5.0 mass%, Ni: 0.05 mass%, Ge: 0.008 mass%, and the remainder being Sn.

[29] A lead-free and antimony-free solder alloy having an alloy composition comprising 1.0 to 3.0 mass % of Ag, 0.7 to 0.9 mass % of Cu, 4.0 mass % of Bi, 0.04 to 0.08 mass % of Ni, 0.006 to 0.009 mass % of Ge, and the remainder being Sn.

[30] The solder alloy as described in any one of [1] to

[17] and

[27] to

[29] , wherein the alloy composition further satisfies 0.3≦Ag / Bi≦0.7; Ag and Bi respectively represent their contents (mass %) in the aforementioned alloy compositions.

[0026]

[31] A lead-free and antimony-free solder alloy having an alloy composition comprising Ag: 3.5 mass%, Cu: 0.8 mass%, Bi: 0.3 to 0.7 mass%, Ni: 0.05 mass%, Ge: 0.008 mass%, Co: 0.008 mass%, and the remainder being Sn.

[32] A lead-free and antimony-free solder alloy having an alloy composition comprising 3.0 to 4.0 mass % of Ag, 0.7 to 0.9 mass % of Cu, 0.5 mass % of Bi, 0.03 to 0.08 mass % of Ni, 0.006 to 0.009 mass % of Ge, 0.004 to 0.012 mass % of Co, and the remainder being Sn.

[33] The solder alloy as described in any one of

[18] to

[21] ,

[31] to

[32] , wherein the alloy composition is Bi: 0.3 to 1.0 mass%, and Further satisfy 5 ≦ Ag / Bi ≦ 15. Ag and Bi respectively represent the contents (mass %) in the aforementioned alloy composition.

[0027]

[34] A lead - free and antimony - free solder alloy having an alloy composition comprising Ag: 1.0 to 4.0 mass %, Cu: 0.7 to 1.0 mass %, Bi: 0.1 to 7.0 mass %, Ni: 0.040 to 0.095 mass %, Ge: 0.007 to 0.015 mass %, and the balance being Sn.

[35] The solder alloy according to

[34] , wherein the aforementioned alloy composition further contains Co: 0.001 to 0.1 mass %.

[36] The solder alloy according to

[34] or

[35] further satisfies 0.007 < Ni / (Ag + Bi) < 0.017. Ni, Ag, and Bi respectively represent the contents (mass %) in the aforementioned alloy composition.

[37] The solder alloy according to any one of

[34] to

[36] further satisfies 46 < (Cu / Ni)×(Ag + Bi) < 120. Cu, Ni, Ag, and Bi respectively represent the contents (mass %) in the aforementioned alloy composition.

[0028]

[38] A solder ball comprising the solder alloy according to any one of [1] to

[37] . <7000156>

[39] The solder ball according to

[38] , having an average particle diameter of 1 to 1000 μm.

[40] The solder ball according to

[38] or

[39] , having a sphericity of 0.95 or more.

[41] The solder ball according to any one of

[38] to

[40] , having a sphericity of 0.99 or more.

[42] A ball grid array formed using the solder ball according to any one of

[38] to

[41] .

[43] A solder joint formed using the solder alloy according to any one of [1] to

[37] . Advantages of the Invention

[0029] According to the present invention, a lead - free and antimony - free solder alloy, solder ball, and solder joint having a melting point near 230°C and a tensile strength of 50 MPa or more can be provided. Embodiments [Modes for carrying out the invention]

[0030] The solder alloy according to the embodiment of the present invention has a melting point of approximately 230°C. In the solder alloy according to the embodiment of the present invention, the main component is Sn, which has a melting point of 232° C. The solder alloy according to the embodiment of the present invention contains elements other than Sn, and the melting point is also around 230° C.

[0031] Here, the "melting point" of the solder alloy refers to the temperature above the solidus temperature and below the liquidus temperature of the solder alloy. The term "around 230°C" refers to 170 to 230°C. The phrase "the melting point of the solder alloy is around 230° C." means "the solidus temperature of the solder alloy is 170 to 225° C., and the liquidus temperature of the solder alloy is 210 to 230° C.."

[0032] 1. Composition of solder alloy The solder alloy of this embodiment has an alloy composition and is lead-free and antimony-free. The alloy composition includes Ag: 1.0 to 4.0 mass%, Cu: 0.1 to 1.0 mass%, Bi: 0.1 to 9.0 mass%, Ni: 0.005 to 0.3 mass%, Ge: 0.001 to 0.015 mass%, and the remainder is Sn.

[0033] (1) Ag: 1.0 to 4.0 mass% Ag is an element that increases the strength of the solder alloy by precipitating fine Ag3Sn at the grain boundaries. The Ag content is more preferably 2.0 mass % or more, and even more preferably 3.0 mass % or more. The Ag content is preferably 3.5 mass % or less. The Ag content is 1.0 to 4.0 mass %, preferably 1.0 to 3.5 mass %, more preferably 2.0 to 3.5 mass %, and even more preferably 3.0 to 3.5 mass %. By making the Ag content greater than the aforementioned lower limit, fine Ag3Sn can be sufficiently precipitated. By setting the Ag content below the above upper limit, the amount of coarse Ag3Sn precipitation can be reduced. Alternatively, in other aspects, by setting the Ag content to be greater than the aforementioned lower limit, the strength of the joint after welding can be improved. By keeping the Ag content below the aforementioned upper limit, the strength of the joint after welding can be improved. Furthermore, by setting the Ag content to 3.5% by mass or less, the effect of reducing the amount of coarse Ag3Sn precipitation can be further enhanced.

[0034] (2) Cu: 0.1 to 1.0 mass% Cu is an element that can inhibit Cu corrosion and increase the precipitation amount of Cu6Sn5. The Cu content is preferably 0.5 mass % or more, more preferably 0.7 mass % or more, and even more preferably 0.75 mass % or more. The Cu content is preferably 0.85 mass % or less, and more preferably 0.8 mass % or less. The Cu content is 0.1 to 1.0 mass %, preferably 0.5 to 0.85 mass %, more preferably 0.7 to 0.8 mass %, and even more preferably 0.75 to 0.8 mass %. By making the Cu content above the aforementioned lower limit, Cu corrosion can be suppressed, Cu6Sn5 can be fully precipitated, and the precipitation amount of brittle SnNi compounds can be reduced. By setting the Cu content to be below the aforementioned upper limit, an excessive increase in the liquidus temperature can be suppressed. Alternatively, in another aspect, by setting the Cu content to 0.7 mass % or more, the thickness of the intermetallic compound layer at the bonding interface can be reduced. By setting the Cu content below the aforementioned upper limit, the thickness of the intermetallic compound layer at the bonding interface can be reduced. When the Cu content is 0.7 mass % or more, the strength of the joint after welding can be improved. By keeping the Cu content below the aforementioned upper limit, the strength of the joint after welding can be improved. By setting the Cu content below the aforementioned upper limit, wettability can be improved. The Cu content is preferably 0.7 to 1.0 mass %, more preferably 0.7 to 0.85 mass %, and even more preferably 0.75 to 0.8 mass %.

[0035] (3) Bi: 0.1 to 9.0 mass% The Bi content is preferably 0.2 mass % or more, more preferably 0.5 mass % or more, and even more preferably 1.0 mass % or more. The Bi content is preferably 5.0 mass % or less, more preferably 4.0 mass % or less, and even more preferably 3.0 mass % or less. The content of Bi is 0.1 to 9.0 mass %, preferably 0.2 to 5.0 mass %, more preferably 0.5 to 4.0 mass %, and even more preferably 1.0 to 3.0 mass %. By keeping the Bi content above the aforementioned lower limit, the optimal mechanical strength for BGA solder balls can be achieved, while also improving creep resistance and wettability. Furthermore, since Bi is dissolved in Sn, it deforms the (Cu, Ni)6Sn5 crystal structure, inhibiting Cu corrosion and allowing for sufficient precipitation of Cu6Sn5, while also reducing the precipitation of brittle SnNi compounds. By keeping the Bi content below the aforementioned upper limit, an excessive drop in the solidus temperature can be suppressed, narrowing ΔT. This can suppress Bi segregation at the bonding interface and prevent a decrease in mechanical strength. Alternatively, in other aspects, by setting the Bi content to be greater than the aforementioned lower limit, the strength of the joint after welding can be improved. Furthermore, by setting the Bi content to 7.0 mass % or less, the strength of the joint after welding can be improved. When the Bi content is equal to or greater than the aforementioned lower limit, wettability can be improved. The Bi content is preferably 0.1 to 7.0 mass %, more preferably 0.2 to 5 mass %, and even more preferably 0.5 to 4 mass %.

[0036] (4) Ni: 0.005 to 0.3 mass% The Ni content is preferably 0.02 mass % or more, more preferably 0.03 mass % or more, and even more preferably 0.04 mass % or more. The Ni content is preferably 0.09 mass % or less, more preferably 0.08 mass % or less, and even more preferably 0.06 mass % or less. The Ni content is 0.005 to 0.3 mass %, preferably 0.02 to 0.09 mass %, more preferably 0.03 to 0.08 mass %, and even more preferably 0.04 to 0.06 mass %. By making the Ni content greater than the aforementioned lower limit, the liquidus temperature of the solder alloy can be controlled, and Ni corrosion can be suppressed, similarly to Cu. By setting the Ni content to be below the aforementioned upper limit, an excessive increase in the liquidus temperature can be suppressed. Alternatively, in another embodiment, by setting the Ni content to 0.04 mass % or more, the thickness of the intermetallic compound layer at the joint interface can be reduced, thereby increasing the strength of the joint after welding. Furthermore, by setting the Ni content to 0.095% by mass or less, the thickness of the intermetallic compound layer at the joint interface can be reduced, and the strength of the joint after welding can be improved. The Ni content is preferably 0.04 to 0.095 mass %, more preferably 0.04 to 0.08 mass %, and even more preferably 0.05 to 0.07 mass %.

[0037] (5) Ge: 0.001 to 0.015 mass% The Ge content is preferably 0.002 mass % or more, and more preferably 0.003 mass % or more. The Ge content is preferably 0.012 mass % or less, more preferably 0.01 mass % or less, and even more preferably 0.009 mass % or less. The Ge content is 0.001 to 0.015 mass %, preferably 0.002 to 0.012 mass %, more preferably 0.003 to 0.01 mass %, and even more preferably 0.003 to 0.009 mass %. By setting the Ge content above the aforementioned lower limit, the generation of oxidized Sn can be suppressed, the crystal structure of the (Cu, Ni)6Sn5 compound can be deformed, and the migration of Ni in the compound can be suppressed. Since the migration of Ni to the solder alloy is hindered, Ni corrosion can be suppressed. By keeping the Ge content below the aforementioned upper limit, an excessive increase in the liquidus temperature can be suppressed. Alternatively, in another aspect, further, by setting the Ge content to 0.007 mass % or more, discoloration of the alloy can be suppressed. By keeping the Ge content below the upper limit, wettability can be improved and the strength of the joint after soldering can be increased. The Ge content is preferably 0.007 to 0.015 mass %, more preferably 0.007 to 0.012 mass %, and even more preferably 0.007 to 0.009 mass %.

[0038] (6) Co: 0.001 to 0.1 mass% The solder alloy of this embodiment may contain Co. The content of Co is preferably 0.001 mass% or more, more preferably 0.002 mass% or more, still more preferably 0.004 mass% or more, and particularly preferably 0.006 mass% or more. The content of Co is preferably 0.1 mass% or less, more preferably 0.015 mass% or less, still more preferably 0.012 mass% or less, and particularly preferably 0.009 mass% or less. The content of Co is preferably 0.001 to 0.1 mass%, more preferably 0.002 to 0.015 mass%, still more preferably 0.004 to 0.012 mass%, and particularly preferably 0.006 to 0.009 mass%. By the content of Co being within the aforementioned range, the tensile strength can be improved, and the elongation, Poisson's ratio, and linear expansion coefficient can also be improved.

[0039] (7) The remaining part: Sn The remaining part of the solder alloy of this embodiment is Sn. In addition to the aforementioned elements, inevitable impurities may also be contained. Even when inevitable impurities are contained, it will not affect the aforementioned effects. Specific examples of inevitable impurities include As or Cd. Also, the present invention is lead-free and antimony-free, but does not exclude the inclusion of Pb or Sb as inevitable impurities.

[0040] <000026, can reduce △T, and the tensile strength is 50 MPa or more, and the elongation, Poisson's ratio, and linear expansion coefficient can be improved.

[0041] ​​​​​​​​​​​​(9)Difference between liquidus temperature and solidus temperature (ΔT) In the solder alloy of this embodiment, when ΔT is within a predetermined range, the solid-liquid coexistence region becomes narrow, so that an increase in the viscosity of the molten solder can be suppressed, segregation of Bi at the bonding interface can be suppressed, and a decrease in mechanical strength can be suppressed, which is preferable. The solidus temperature of the solder alloy of this embodiment is 170 to 225 °C, preferably 172 to 223 °C, more preferably 174 to 221 °C, and still more preferably 176 to 219 °C. The liquidus temperature of the solder alloy of this embodiment is 210 to 230 °C, preferably 212 to 230 °C, more preferably 212 to 228 °C, and still more preferably 214 to 226 °C. ΔT is preferably 50 °C or less, more preferably 45 °C or less, still more preferably 40 °C or less, particularly preferably 30 °C or less, and most preferably 15 °C or less. The lower limit of ΔT is not particularly limited, but for example, it can be 1 °C.

[0042] (10)Ni / (Ag + Bi) In this ratio, Ni, Ag, and Bi respectively represent the contents (mass %) in the alloy composition. Ni / (Ag + Bi) is obtained by dividing Ni by the sum of Ag and Bi. The solder alloy of this embodiment preferably has Ni / (Ag + Bi) exceeding 0.007. By having 0.007 < Ni / (Ag + Bi), coarsening of the intermetallic compound can be suppressed, and an excessive decrease in the solidus temperature can be suppressed. The solder alloy of this embodiment preferably has Ni / (Ag + Bi) less than 0.017. By having Ni / (Ag + Bi) < 0.017, an excessive increase in the liquidus temperature can be suppressed. Thereby, sufficient wettability can be achieved. The solder alloy of this embodiment preferably satisfies 0.007 < Ni / (Ag + Bi) < 0.017.

[0043] (11)(Cu / Ni)×(Ag + Bi) In this ratio, Cu, Ni, Ag, and Bi respectively represent the contents (mass %) in the alloy composition. (Cu / Ni)×(Ag + Bi) is obtained by multiplying the value obtained by dividing Cu by Ni by the sum of Ag and Bi. The solder alloy of this embodiment preferably has (Cu / Ni)×(Ag+Bi) exceeding 46. By having 46 < (Cu / Ni)×(Ag+Bi), an excessive increase in the liquidus temperature can be suppressed. Thereby, the wettability can be made sufficient. The solder alloy of this embodiment preferably has (Cu / Ni)×(Ag+Bi) less than 120. By having (Cu / Ni)×(Ag+Bi) < 120, coarsening of the intermetallic compound can be suppressed, and an excessive decrease in the solidus temperature can be suppressed. The solder alloy of this embodiment preferably satisfies 46 < (Cu / Ni)×(Ag+Bi) < 120. The solder alloy of this embodiment can have a composition that satisfies 46 < (Cu / Ni)×(Ag+Bi) < 110, or can also have a composition that satisfies 46 < (Cu / Ni)×(Ag+Bi) < 100.

[0044] In the solder alloy of the embodiment described above, by having a specific alloy composition containing Ag, Cu, Bi, Ni, Ge, and Sn, a lead-free and antimony-free solder alloy with a melting point near 230°C and a tensile strength of 50 MPa or more can be provided. Furthermore, the solder alloy of the embodiment described above can reduce ΔT by setting the contents of Ag and Bi within a predetermined range. When the solder alloy of the embodiment described above contains Co, by adjusting the content of Co to a predetermined range, ΔT can be reduced, and the elongation, Poisson's ratio, and linear expansion coefficient of the solder alloy can be improved.

[0045] The solder alloy of this embodiment can be exemplified by the following first to fifth embodiments.

[0046] <The First Embodiment> The solder alloy of the first embodiment has an alloy composition and is a lead-free and antimony-free solder alloy, and 1 < Ag / Bi. The alloy composition contains Ag: 1.0 to 4.0 mass%, Cu: 0.1 to 1.0 mass%, Bi: 0.1 to 9.0 mass%, Ni: 0.005 to 0.3 mass%, Ge: 0.001 to 0.015 mass%, and the balance is Sn. <​​​​​​The solder alloy of the first embodiment can be a lead-free and antimony-free solder alloy having an alloy composition including Ag: 3.5 mass%, Cu: 0.8 mass%, Bi: 1.0 to 2.0 mass%, Ni: 0.05 mass%, Ge: 0.008 mass%, and the remainder being Sn.

[0048] The solder alloy of the first embodiment can be a lead-free and antimony-free solder alloy having an alloy composition, wherein the alloy composition includes Ag: 3.0 to 4.0 mass%, Cu: 0.7 to 0.9 mass%, Bi: 1.5 mass%, Ni: 0.03 to 0.08 mass%, Ge: 0.006 to 0.009 mass%, and the remainder is Sn.

[0049] The solder alloy of the first embodiment can be a lead-free and antimony-free solder alloy having an alloy composition, wherein the alloy composition includes Ag: 3.0 to 4.0 mass%, Cu: 0.7 to 0.9 mass%, Bi: 1.8 mass%, Ni: 0.03 to 0.08 mass%, Ge: 0.006 to 0.009 mass%, and the remainder is Sn.

[0050] The solder alloy of the first embodiment can be a lead-free and antimony-free solder alloy having an alloy composition including Ag: 3.5 mass%, Cu: 0.8 mass%, Bi: 1.5 to 3.0 mass%, Ni: 0.05 mass%, Ge: 0.003 mass%, and the remainder being Sn.

[0051] The solder alloy of the first embodiment can be a lead-free and antimony-free solder alloy having an alloy composition, wherein the alloy composition includes Ag: 3.0 to 4.0 mass%, Cu: 0.7 to 0.9 mass%, Bi: 2.0 mass%, Ni: 0.03 to 0.08 mass%, Ge: 0.002 to 0.004 mass%, and the remainder is Sn.

[0052] The solder alloy of the first embodiment can be a lead-free and antimony-free solder alloy having an alloy composition, wherein the alloy composition includes Ag: 3.0 to 4.0 mass%, Cu: 0.7 to 0.9 mass%, Bi: 2.5 mass%, Ni: 0.03 to 0.08 mass%, Ge: 0.002 to 0.004 mass%, and the remainder is Sn.

[0053] The solder alloy of the first embodiment preferably satisfies 1.2≦Ag / Bi≦3.0, and more preferably satisfies 1.3≦Ag / Bi≦1.9. Ag and Bi respectively represent their contents (mass %) in the aforementioned alloy compositions. By keeping Ag / Bi within the above range, ΔT can be reduced and tensile strength can be improved.

[0054] The solder alloy of the first embodiment can be a lead-free and antimony-free solder alloy having an alloy composition, which includes Ag: 3.5 mass%, Cu: 0.8 mass%, Bi: 1.5 mass%, Ni: 0.05 mass%, Ge: 0.008 mass%, and the remainder is Sn.

[0055] The solder alloy of the first embodiment can be a lead-free and antimony-free solder alloy having an alloy composition including Ag: 3.5 mass%, Cu: 0.8 mass%, Bi: 1.8 mass%, Ni: 0.05 mass%, Ge: 0.008 mass%, and the remainder being Sn.

[0056] The solder alloy of the first embodiment can be a lead-free and antimony-free solder alloy having an alloy composition including Ag: 3.5 mass%, Cu: 0.8 mass%, Bi: 2.0 mass%, Ni: 0.05 mass%, Ge: 0.003 mass%, and the remainder being Sn.

[0057] The solder alloy of the first embodiment can be a lead-free and antimony-free solder alloy having an alloy composition including Ag: 3.5 mass%, Cu: 0.8 mass%, Bi: 2.5 mass%, Ni: 0.05 mass%, Ge: 0.003 mass%, and the remainder being Sn.

[0058] In the first embodiment, the solder alloy has a specific alloy composition including Ag, Cu, Bi, Ni, Ge, and Sn, thereby providing a lead-free and antimony-free solder alloy having a melting point of approximately 230° C. and a tensile strength of 50 MPa or more. The solder alloy of the first embodiment is not only applicable to BGA, but also to die bonding. The solder alloy of the first embodiment is 1 <Ag / Bi。 The solder alloy of the first embodiment can reduce ΔT by setting the contents of Ag and Bi within a predetermined range.

[0059] The solidus temperature of the solder alloy of the first embodiment is preferably 208 to 223°C, more preferably 210 to 221°C, and even more preferably 212 to 219°C. The liquidus temperature of the solder alloy of the first embodiment is preferably 213 to 227°C, more preferably 215 to 225°C, and even more preferably 217 to 223°C. The ΔT of the solder alloy of the first embodiment is preferably 10° C. or less, more preferably 8° C. or less, and even more preferably 7° C. or less. The lower limit of ΔT is not particularly limited, but may be 1° C., for example.

[0060] The solder alloy of the first embodiment preferably has a ratio of 1.2 ≤ Ag / Bi ≤ 3.0, and more preferably 1.3 ≤ Ag / Bi ≤ 1.9. In the solder alloy of the first embodiment, by keeping the Ag / Bi ratio within the above range, ΔT can be easily reduced and tensile strength can be easily increased.

[0061] Alternatively, in other aspects, the solder alloy of the first embodiment preferably has a ratio of 1.0 ≤ Ag / Bi ≤ 50.0, more preferably 1.0 ≤ Ag / Bi ≤ 3.0, and even more preferably 1.5 ≤ Ag / Bi ≤ 3.0. In the solder alloy of the first embodiment, keeping the Ag / Bi ratio within the above range facilitates reducing ΔT and improving tensile strength.

[0062] Alternatively, in other aspects, the solder alloy of the first embodiment preferably has an Ag / Bi ratio of 10.0 ≤ Ag / Bi ≤ 50.0, and more preferably 20.0 ≤ Ag / Bi ≤ 40.0. In the solder alloy of the first embodiment, by keeping the Ag / Bi ratio within the above range, ΔT is easily reduced and tensile strength is easily increased.

[0063] <Second Implementation> The solder alloy of the second embodiment has an alloy composition and is a lead-free and antimony-free solder alloy, and satisfies Ag / Bi≦1, and the alloy composition includes Ag: 1.0 to 4.0 mass%, Cu: 0.1 to 1.0 mass%, Bi: 0.1 to 9.0 mass%, Ni: 0.005 to 0.3 mass%, Ge: 0.001 to 0.015 mass%, and the remainder is Sn. The contents of Ag, Cu, Bi, Ni, and Ge may be as described above respectively. In the ratios here, Ag and Bi respectively represent their contents (mass %) in the aforementioned alloy compositions.

[0064] The solder alloy of the second embodiment can be a lead-free and antimony-free solder alloy having an alloy composition including Ag: 2.0 mass%, Cu: 0.8 mass%, Bi: 3.0 to 5.0 mass%, Ni: 0.05 mass%, Ge: 0.008 mass%, and the remainder being Sn.

[0065] The solder alloy of the second embodiment can be a lead-free and antimony-free solder alloy having an alloy composition, wherein the alloy composition includes Ag: 1.0 to 3.0 mass%, Cu: 0.7 to 0.9 mass%, Bi: 4.0 mass%, Ni: 0.04 to 0.08 mass%, Ge: 0.006 to 0.009 mass%, and the remainder is Sn.

[0066] The solder alloy of the second embodiment preferably satisfies 0.3≦Ag / Bi≦0.7. Ag and Bi respectively represent their contents (mass %) in the aforementioned alloy compositions. When Ag / Bi is within the above range, the tensile strength can be further improved.

[0067] The solder alloy of the second embodiment is preferably a lead-free and antimony-free solder alloy having an alloy composition comprising Ag: 2.0 mass%, Cu: 0.8 mass%, Bi: 4.0 mass%, Ni: 0.05 mass%, Ge: 0.008 mass%, and the remainder being Sn.

[0068] In the solder alloy of the second embodiment, by having a specific alloy composition including Ag, Cu, Bi, Ni, Ge and Sn, a lead-free and antimony-free solder alloy with a melting point of approximately 230°C and a tensile strength of 50 MPa or more can be provided. The solder alloy of the second embodiment is not only applicable to BGA, but also to die bonding. The solder alloy of the second embodiment is Ag / Bi≦1. The solder alloy of the second embodiment can reduce ΔT by setting the contents of Ag and Bi within a predetermined range.

[0069] The solidus temperature of the solder alloy of the second embodiment is preferably 175 to 220°C, more preferably 175 to 218°C, and even more preferably 176 to 216°C. The liquidus temperature of the solder alloy of the second embodiment is 210 to 230°C, preferably 211 to 229°C, and more preferably 213 to 227°C. The ΔT of the solder alloy of the second embodiment is preferably 50° C. or less, more preferably 45° C. or less, and even more preferably 40° C. or less. The lower limit of ΔT is not particularly limited, but may be 1° C., for example.

[0070] The solder alloy of the second embodiment preferably has a ratio of 0.3≦Ag / Bi≦0.7. In the solder alloy of the second embodiment, by keeping the Ag / Bi ratio within the above range, it is easy to reduce ΔT and increase tensile strength.

[0071] Alternatively, in other aspects, the solder alloy of the second embodiment preferably has a ratio of 0.1 ≤ Ag / Bi ≤ 0.8, more preferably 0.15 ≤ Ag / Bi ≤ 0.7, and even more preferably 0.2 ≤ Ag / Bi ≤ 0.6. In the solder alloy of the second embodiment, keeping the Ag / Bi ratio within the above range facilitates lowering ΔT and increasing tensile strength.

[0072] The solder alloy of the first embodiment can suppress the decrease in solidus temperature more than the solder alloy of the second embodiment. The solder alloy of the first embodiment can further reduce ΔT than the solder alloy of the second embodiment. The solder alloy of the second embodiment can further improve the tensile strength compared to the solder alloy of the first embodiment.

[0073] <Third Implementation Form> The solder alloy of the third embodiment has an alloy composition and is a lead-free and antimony-free solder alloy. The alloy composition includes Ag: 1.0 to 4.0 mass%, Cu: 0.1 to 1.0 mass%, Bi: 0.1 to 9.0 mass%, Ni: 0.005 to 0.3 mass%, Ge: 0.001 to 0.015 mass%, Co: 0.001 to 0.1 mass%, and the remainder is Sn. The contents of Ag, Cu, Bi, Ni, Ge, and Co can be as described above, respectively.

[0074] The solder alloy of the third embodiment can be a lead-free and antimony-free solder alloy having an alloy composition, wherein the alloy composition includes Ag: 3.5 mass%, Cu: 0.8 mass%, Bi: 0.3 to 0.7 mass%, Ni: 0.05 mass%, Ge: 0.008 mass%, Co: 0.008 mass%, and the remainder is Sn.

[0075] The solder alloy of the third embodiment can be a lead-free and antimony-free solder alloy having an alloy composition, wherein the alloy composition includes Ag: 3.0 to 4.0 mass%, Cu: 0.7 to 0.9 mass%, Bi: 0.5 mass%, Ni: 0.03 to 0.08 mass%, Ge: 0.006 to 0.009 mass%, Co: 0.004 to 0.012 mass%, and the remainder is Sn.

[0076] The solder alloy of the third embodiment preferably has Bi: 0.3 to 1.0 mass %, and satisfies 5≦Ag / Bi≦15. Ag and Bi respectively represent their contents (mass %) in the aforementioned alloy compositions. When Ag / Bi is within the above range, by adjusting the Co content to a predetermined range, ΔT can be reduced and the tensile strength, elongation, Passon's ratio, and linear expansion coefficient can be improved.

[0077] The solder alloy of the third embodiment is preferably a lead-free and antimony-free solder alloy having an alloy composition comprising Ag: 3.5 mass%, Cu: 0.8 mass%, Bi: 0.5 mass%, Ni: 0.05 mass%, Ge: 0.008 mass%, Co: 0.008 mass%, and the remainder being Sn.

[0078] The Co content of the solder alloy of the third embodiment is 0.001 to 0.1 mass %. In the solder alloy of the third embodiment, by having a specific alloy composition including Ag, Cu, Bi, Ni, Ge, Co and Sn, a lead-free and antimony-free solder alloy with a melting point of approximately 230°C and a tensile strength of 50 MPa or more can be provided. The solder alloy of the third embodiment is not only applicable to BGA, but also to die bonding.

[0079] The solidus temperature of the solder alloy of the third embodiment is preferably 212 to 222° C., more preferably 214 to 220° C., and even more preferably 216 to 218° C. The liquidus temperature of the solder alloy of the third embodiment is preferably 216 to 226° C., more preferably 218 to 224° C., and even more preferably 220 to 222° C. The ΔT of the solder alloy of the third embodiment is preferably 10° C. or less, more preferably 8° C. or less, and even more preferably 7° C. or less. The lower limit of ΔT is not particularly limited, but may be 1° C., for example.

[0080] The solder alloy of the third embodiment preferably has an Ag / Bi ratio of 5 ≤ ≤ 15. In the solder alloy of the third embodiment, keeping the Ag / Bi ratio within this range facilitates lowering ΔT and improving tensile strength. Furthermore, keeping the Ag / Bi ratio within this range improves elongation, Passon's ratio, and linear expansion coefficient.

[0081] Alternatively, in another aspect, the solder alloy of the third embodiment preferably has a ratio of 0.2 ≤ Ag / Bi ≤ 15.0, more preferably 0.3 ≤ Ag / Bi ≤ 3.0, even more preferably 0.5 ≤ Ag / Bi ≤ 2.0, and particularly preferably 0.6 ≤ Ag / Bi ≤ 1.0. In the solder alloy of the third embodiment, by keeping the Ag / Bi ratio within the above range, ΔT is easily reduced and tensile strength is easily increased.

[0082] The solidus temperature of the solder alloy of the third embodiment is preferably 200 to 223°C, more preferably 202 to 221°C, and even more preferably 204 to 219°C. The liquidus temperature of the solder alloy of the third embodiment is preferably 210 to 227°C, more preferably 211 to 225°C, and even more preferably 213 to 223°C. The ΔT of the solder alloy of the third embodiment is preferably 30° C. or less, more preferably 20° C. or less, and even more preferably 15° C. or less. The lower limit of ΔT is not particularly limited, but may be 1° C., for example.

[0083] <Fourth Implementation Type> The solder alloy of the fourth embodiment has an alloy composition and is lead-free and antimony-free. The alloy composition includes Ag: 1.0 to 4.0 mass%, Cu: 0.7 to 1.0 mass%, Bi: 0.1 to 7.0 mass%, Ni: 0.040 to 0.095 mass%, Ge: 0.007 to 0.015 mass%, and the remainder is Sn. The contents of Ag, Cu, Bi, Ni, and Ge may be as described above respectively.

[0084] The solder alloy of the fourth embodiment may be a lead-free and antimony-free solder alloy having an alloy composition comprising Ag: 3.0 to 3.5 mass%, Cu: 0.7 to 1.0 mass%, Bi: 1.0 to 2.0 mass%, Ni: 0.040 to 0.060 mass%, Ge: 0.007 to 0.010 mass%, and the remainder being Sn.

[0085] Alternatively, the solder alloy of the fourth embodiment may be a lead-free and antimony-free solder alloy having an alloy composition comprising 1.5 to 2.5 mass% of Ag, 0.7 to 1.0 mass% of Cu, 3.0 to 5.0 mass% of Bi, 0.060 to 0.080 mass% of Ni, 0.007 to 0.010 mass% of Ge, and the remainder being Sn.

[0086] In the solder alloy of the fourth embodiment, by having a specific alloy composition including Ag, Cu, Bi, Ni, Ge and Sn, a lead-free and antimony-free solder alloy with a melting point of approximately 230°C and a tensile strength of 50 MPa or more can be provided. The solder alloy of the fourth embodiment is not only suitable for BGA, but also suitable for die bonding.

[0087] The solder alloy of the fourth embodiment is preferably 0.3≦Ag / Bi≦3.0, more preferably 1.2≦Ag / Bi≦3.0, and even more preferably 1.3≦Ag / Bi≦1.9. In the solder alloy of the fourth embodiment, by keeping the Ag / Bi ratio within the above range, ΔT can be easily reduced and the tensile strength can be easily increased.

[0088] Alternatively, the solder alloy of the fourth embodiment is preferably 0.3≦Ag / Bi≦3.0, and more preferably 0.3≦Ag / Bi≦0.7. In the solder alloy of the fourth embodiment, by keeping the Ag / Bi ratio within the above range, ΔT can be easily reduced and the tensile strength can be easily increased.

[0089] The solder alloy system of the fourth embodiment further exhibits the following effects. The solder alloy of the fourth embodiment can reduce the thickness of the intermetallic compound layer at the bonding interface. Furthermore, the solder alloy of the fourth embodiment can fully precipitate fine Ag3Sn and reduce the amount of coarse Ag3Sn precipitated. Furthermore, the solder alloy of the fourth embodiment can suppress discoloration of the alloy. Furthermore, the solder alloy of the fourth embodiment can improve the strength of the joint after soldering.

[0090] For the solder alloy of the fourth embodiment, it is preferable that Ni / (Ag + Bi) exceeds 0.007. By having 0.007 < Ni / (Ag + Bi), coarsening of intermetallic compounds can be suppressed, and excessive decrease in the solidus temperature can be suppressed. For the solder alloy of the fourth embodiment, it is preferable that Ni / (Ag + Bi) is less than 0.017. By having Ni / (Ag + Bi) < 0.017, excessive increase in the liquidus temperature can be suppressed. Thereby, sufficient wettability can be achieved. For the solder alloy of the fourth embodiment, it is preferable that 0.007 < Ni / (Ag + Bi) < 0.017 is satisfied. Ni, Ag, and Bi respectively represent the contents (mass %) in the alloy composition.

[0091] For the solder alloy of the fourth embodiment, it is preferable that (Cu / Ni)×(Ag + Bi) exceeds 46. By having 46 < (Cu / Ni)×(Ag + Bi), excessive increase in the liquidus temperature can be suppressed. Thereby, sufficient wettability can be achieved. For the solder alloy of the fourth embodiment, it is preferable that (Cu / Ni)×(Ag + Bi) is less than 120. By having (Cu / Ni)×(Ag + Bi) < 120, coarsening of intermetallic compounds can be suppressed, and excessive decrease in the solidus temperature can be suppressed. For the solder alloy of the fourth embodiment, it is preferable that 46 < (Cu / Ni)×(Ag + Bi) < 120 is satisfied. The solder alloy of the fourth embodiment can have a composition that satisfies 46 < (Cu / Ni)×(Ag + Bi) < ll0, or can also have a composition that satisfies 46 < (Cu / Ni)×(Ag + Bi) < 100.

[0092] For the solder alloy of the fourth embodiment, it is preferable that 1.0 ≦ Ag / Bi ≦ 50.0, more preferably 1.0 ≦ Ag / Bi ≦ 3.0, and even more preferably 1.5 ≦ Ag / Bi ≦ 3.0. In the solder alloy of the fourth embodiment, by having the Ag / Bi ratio within the above range, it is easy to reduce △T and easy to improve the tensile strength.

[0093] Or, in other aspects, for the solder alloy of the fourth embodiment, it is preferable that 10.0 ≦ Ag / Bi ≦ 50.0, more preferably 20.0 ≦ Ag / Bi ≦ 40.0. In the solder alloy of the fourth embodiment, by having the Ag / Bi ratio within the above range, it is easy to reduce △T and easy to improve the tensile strength.

[0094] Alternatively, the solder alloy of the fourth embodiment preferably has a ratio of 0.1 ≤ Ag / Bi ≤ 0.8, more preferably 0.15 ≤ Ag / Bi ≤ 0.7, and even more preferably 0.2 ≤ Ag / Bi ≤ 0.6. In the solder alloy of the fourth embodiment, keeping the Ag / Bi ratio within the above range facilitates lowering ΔT and increasing tensile strength.

[0095] The solidus temperature of the solder alloy of the fourth embodiment is 170 to 225°C, preferably 172 to 223°C, more preferably 174 to 221°C, and even more preferably 176 to 219°C. The liquidus temperature of the solder alloy of the fourth embodiment is 210 to 230°C, preferably 212 to 230°C, more preferably 212 to 228°C, and even more preferably 214 to 226°C. ΔT is preferably 50° C. or less, more preferably 45° C. or less, and even more preferably 40° C. or less. The lower limit of ΔT is not particularly limited, but may be 1° C., for example.

[0096] <Fifth Implementation Type> The solder alloy of the fifth embodiment has an alloy composition and is lead-free and antimony-free, and the alloy composition includes Ag: 1.0 to 4.0 mass%, Cu: 0.7 to 1.0 mass%, Bi: 0.1 to 7.0 mass%, Ni: 0.040 to 0.095 mass%, Ge: 0.007 to 0.015 mass%, Co: 0.001 to 0.1 mass%, and the remainder is Sn. The contents of Ag, Cu, Bi, Ni, Ge, and Co can be as described above, respectively.

[0097] The solder alloy of the fifth embodiment may have an alloy composition and be a lead-free and antimony-free solder alloy, the alloy composition including Ag: 3.0 to 3.5 mass%, Cu: 0.7 to 1.0 mass%, Bi: 0.3 to 0.7 mass%, Ni: 0.040 to 0.060 mass%, Ge: 0.007 to 0.010 mass%, Co: 0.005 to 0.010 mass%, and the remainder being Sn.

[0098] In the solder alloy of the fifth embodiment, by having a specific alloy composition including Ag, Cu, Bi, Ni, Ge, Co and Sn, a lead-free and antimony-free solder alloy with a melting point of approximately 230°C and a tensile strength of 50 MPa or more can be provided. The solder alloy of the fifth embodiment is not only applicable to BGA, but also to die bonding. The solder alloy of the fifth embodiment can improve the elongation, Poisson's ratio, and coefficient of linear expansion.

[0099] For the solder alloy of the fifth embodiment, it is preferable that 5 ≦ Ag / Bi ≦ 15. In the solder alloy of the fifth embodiment, when the ratio of Ag / Bi is within the above range, it is easy to reduce ΔT and easy to improve the tensile strength. Also, it is easy to improve the elongation, Poisson's ratio, and coefficient of linear expansion.

[0100] Furthermore, the solder alloy of the fifth embodiment exhibits the following effects. The solder alloy of the fifth embodiment can make the thickness of the intermetallic compound layer at the bonding interface thinner. Also, the solder alloy of the fifth embodiment can cause fine Ag3Sn to precipitate sufficiently and reduce the precipitation amount of coarse Ag3Sn. Also, the solder alloy of the fifth embodiment can suppress the discoloration of the alloy. Also, the solder alloy of the fifth embodiment can improve the strength of the joint after welding.

[0101] For the solder alloy of the fifth embodiment, it is preferable that Ni / (Ag + Bi) exceeds 0.007. By having 0.007 < Ni / (Ag + Bi), the coarsening of the intermetallic compound can be suppressed, and the excessive decrease in the solidus temperature can be suppressed. For the solder alloy of the fifth embodiment, it is preferable that Ni / (Ag + Bi) is less than 0.017. By having Ni / (Ag + Bi) < 0.017, the excessive increase in the liquidus temperature can be suppressed. Thereby, the wettability can be made sufficient. For the solder alloy of the fifth embodiment, it is preferable that 0.007 < Ni / (Ag + Bi) < 0.017 is satisfied. Ni, Ag, and Bi respectively represent the contents (mass %) in the alloy composition.

[0102] For the solder alloy of the fifth embodiment, it is preferable that (Cu / Ni) × (Ag + Bi) exceeds 46. By having 46 < (Cu / Ni) × (Ag + Bi), the excessive increase in the liquidus temperature can be suppressed. Thereby, the wettability can be made sufficient. For the solder alloy of the fifth embodiment, it is preferable that (Cu / Ni) × (Ag + Bi) is less than 120. By having (Cu / Ni) × (Ag + Bi) < 120, the coarsening of the intermetallic compound can be suppressed, and the excessive decrease in the solidus temperature can be suppressed. The solder alloy of the fifth embodiment preferably satisfies 46 < (Cu / Ni) × (Ag + Bi) < 120. The solder alloy of the fifth embodiment may have a composition satisfying 46 < (Cu / Ni) × (Ag + Bi) < 110, or may have a composition satisfying 46 < (Cu / Ni) × (Ag + Bi) < 100.

[0103] The solder alloy of the fifth embodiment preferably has an Ag / Bi ratio of 0.2 ≤ Ag / Bi ≤ 15.0, and more preferably 5 ≤ Ag / Bi ≤ 15. In the solder alloy of the fifth embodiment, keeping the Ag / Bi ratio within the above range facilitates lowering ΔT and improving tensile strength. Furthermore, keeping the Ag / Bi ratio within the above range also improves elongation, Passon's ratio, and linear expansion coefficient.

[0104] Alternatively, the solder alloy of the fifth embodiment preferably has an Ag / Bi ratio of 0.2 ≤ Ag / Bi ≤ 15.0, more preferably 0.3 ≤ Ag / Bi ≤ 3.0, even more preferably 0.5 ≤ Ag / Bi ≤ 2.0, and particularly preferably 0.6 ≤ Ag / Bi ≤ 1.0. In the solder alloy of the fifth embodiment, by keeping the Ag / Bi ratio within the above range, ΔT is easily reduced and tensile strength is easily increased.

[0105] The solidus temperature of the solder alloy of the fifth embodiment is preferably 200 to 223°C, more preferably 202 to 221°C, and even more preferably 204 to 219°C. The liquidus temperature of the solder alloy of the fifth embodiment is preferably 210 to 227°C, more preferably 211 to 225°C, and even more preferably 213 to 223°C. The ΔT of the solder alloy of the fifth embodiment is preferably 30° C. or less, more preferably 20° C. or less, and even more preferably 15° C. or less. The lower limit of ΔT is not particularly limited, but may be 1° C., for example.

[0106] 2. Solder balls The lead-free and antimony-free solder alloy of the embodiment described above is the most suitable form for use in solder balls of BGA. The sphericity of the solder balls of this embodiment is preferably 0.90 or above, more preferably 0.95 or above, and most preferably 0.99 or above. The true sphericity can be obtained by various methods such as the least square center method (LSC method), the minimum zone center method (MZC method), the maximum inscribed center method (MIC method), and the minimum circumscribed center method (MCC method). In the present invention, the sphericity of the solder ball is measured using a CNC image measuring system (ULTRAQUICK VISION ULTRA QV350-PRO measuring device manufactured by Mitsutoyo Co., Ltd.) using the minimum zone center method (MZC method). In the present invention, the so-called sphericity refers to the deviation from a true sphere, for example, the arithmetic mean value calculated by dividing the diameter of 500 solder balls by the major diameter. The closer the value is to the upper limit of 1.00, the closer it is to a true sphere.

[0107] The solder balls of this embodiment are used to form bumps on electrodes or substrates of semiconductor packages such as BGA (Ball Grid Array). The diameter of the solder balls in this embodiment is preferably in the range of 1 to 1000 μm, more preferably in the range of 50 μm to 300 μm. The solder balls can be manufactured using a general solder ball manufacturing method. The diameter in this embodiment refers to the diameter measured by an ULTRAQUICK VISION ULTRA QV350-PRO measuring device manufactured by Mitsutoyo Corporation.

[0108] 3. Solder joints The solder joint of this embodiment is suitable for connecting an IC chip and its substrate (interposer) in a semiconductor package, or connecting a semiconductor package and a printed circuit board. Here, the so-called "solder joint" related to the present invention is connected using the above-mentioned solder alloy related to the present invention, and refers to the connection part between the IC chip and the substrate, and includes the connection part of the electrode or the connection part between the die and the substrate.

[0109] 4. Others The solder alloy bonding method described above can be performed using conventional methods, such as reflow soldering. The heating temperature can be adjusted appropriately based on the heat resistance of the wafer and the liquidus temperature of the solder alloy. To minimize thermal damage to the wafer, a temperature of approximately 240°C is preferred. The melting temperature of the solder alloy during flow soldering is approximately 20°C higher than the liquidus temperature. Furthermore, when joining using the solder alloy of this embodiment, considering the cooling rate during solidification can further refine the microstructure. For example, cooling the solder joint at a cooling rate of 2 to 3°C / s or more can be used. These other joining conditions can be adjusted appropriately depending on the composition of the solder alloy.

[0110] The solder alloy of the present invention can be manufactured by using low-alpha radiation materials as raw materials. Such low-alpha radiation alloy can suppress soft errors when used to form solder bumps around memory devices. [[Example]]

[0111] The present invention is described below by way of examples, but the present invention is not limited to the following examples.

[0112] The solder alloys of Examples 1 to 4 were synthesized according to the following compositions. Each solder alloy was measured according to the following method.

[0113] (1) Determination of solidus temperature and liquidus temperature The solidus temperature and the liquidus temperature were measured by differential scanning calorimetry (DSC) using a thermomechanical analyzer (EXSTAR 6000, manufactured by Seiko Instruments). The solidus temperature was measured according to the method of JIS Z3198-1. The liquidus temperature was measured by DSC in the same manner as the solidus temperature measurement method in JIS Z3198-1.

[0114] (2) Determination of tensile strength and elongation A universal testing machine (Instron: 5966) was used to perform tensile tests on test pieces with a parallel section of 30 mm and a diameter of 8 mm to determine the tensile strength and elongation.

[0115] (3) Pasombi The Passon's ratio was measured using a SING AROUND type sonic velocity measuring device (UVM-2, Ultrasonic Wave Industries, Inc.) on a cubic test piece with a side of 15 mm.

[0116] (4) Linear expansion coefficient The linear expansion coefficient was measured using a thermomechanical analyzer (EXSTAR 6000, Seiko Instruments) on a test piece with a diameter of 8 mm and a length of 15 mm.

[0117] (Example 1) A solder alloy having an alloy composition including 3.5 mass % of Ag, 0.8 mass % of Cu, 1.5 mass % of Bi, 0.05 mass % of Ni, 0.008 mass % of Ge, and the balance of Sn was manufactured. The solidus temperature of the solder alloy of Example 1 is 214°C, the liquidus temperature is 219°C, and the ΔT is 5°C. The tensile strength of the solder alloy of Example 1 is 66.2 MPa.

[0118] (Example 2) A solder alloy having an alloy composition including 3.5 mass % of Ag, 0.8 mass % of Cu, 1.8 mass % of Bi, 0.05 mass % of Ni, 0.008 mass % of Ge, and the balance of Sn was manufactured. The solder alloy of Example 2 has a solidus temperature of 213°C, a liquidus temperature of 218°C, and a ΔT of 5°C. The tensile strength of the solder alloy of Example 2 is 69.9 MPa.

[0119] (Example 3) A solder alloy having an alloy composition including 2.0 mass % of Ag, 0.75 mass % of Cu, 4.0 mass % of Bi, 0.07 mass % of Ni, 0.008 mass % of Ge, and the balance of Sn was manufactured. The solder alloy of Example 3 has a solidus temperature of 206°C, a liquidus temperature of 219°C, and a ΔT of 13°C. The tensile strength of the solder alloy of Example 3 is 83.8 MPa.

[0120] (Example 4) A solder alloy having an alloy composition including 3.5 mass % of Ag, 0.8 mass % of Cu, 0.5 mass % of Bi, 0.05 mass % of Ni, 0.008 mass % of Ge, 0.008 mass % of Co, and the balance of Sn was manufactured. The solder alloy of Example 4 has a solidus temperature of 217°C, a liquidus temperature of 221°C, and a ΔT of 4°C. The tensile strength of the solder alloy of Example 4 is 55.5 MPa. The elongation of the solder alloy of Example 4 is 33%. The Passon's ratio of the solder alloy of Example 4 is 0.35. The linear expansion coefficient of the solder alloy of Example 4 is 21.5 ppm / K.

[0121] (Example 5) A solder alloy having an alloy composition including 3.5 mass % of Ag, 0.8 mass % of Cu, 2.0 mass % of Bi, 0.05 mass % of Ni, 0.003 mass % of Ge, and the balance of Sn was manufactured. The solder alloy of Example 5 has a solidus temperature of 212°C, a liquidus temperature of 218°C, and a ΔT of 6°C. The tensile strength of the solder alloy of Example 5 is 72.3 MPa.

[0122] (Example 6) A solder alloy having an alloy composition including 3.5 mass % of Ag, 0.8 mass % of Cu, 2.5 mass % of Bi, 0.05 mass % of Ni, 0.003 mass % of Ge, and the balance of Sn was manufactured. The solder alloy of Example 6 has a solidus temperature of 211°C, a liquidus temperature of 216°C, and a ΔT of 5°C. The tensile strength of the solder alloy of Example 6 is 78.0 MPa.

[0123] <Preparation of solder alloy powder> (Test Examples A1 to A15, Test Examples B1 to B16) The solder alloy powders of the test examples were prepared according to the compositions shown in Tables 1 to 5 below. In the powder size classification (Table 2) of JIS Z 3284-1:2014, the solder alloy powder satisfies the particle size distribution specified in Symbol 6. The mass fraction of the solder alloy powder having a particle size of 5 to 15 μm relative to the mass of the entire solder alloy powder (100%) is 80% or more.

[0124] Test Examples A1 to A12 and Test Example A14 correspond to the fourth embodiment. Test Examples A13 and A15 correspond to the fifth embodiment.

[0125] Test Examples B1 to B16 also do not correspond to any of the fourth embodiment and the fifth embodiment. Test Example B3, Test Examples B5 to B6, Test Examples B8 to B9, and Test Examples B11 to B16 are within the scope of the present invention. Test Examples B1 to B2, Test Example B4, Test Example B7, and Test Example B10 are outside the scope of the present invention.

[0126] Using the solder alloy powder prepared above, we conducted evaluations of intermetallic compound (IMC) layer thickness, Ag3Sn size, discoloration resistance, wettability, and solder joint strength according to the evaluation methods described in the "Evaluation" section below. The results are shown in Tables 1 and 2.

[0127] <Assessment> 《Evaluation of the Thickness of Intermetallic Compound (IMC) Layer》 Solder balls with a diameter of 0.3 mm were produced using the solder alloy powders of each example. A CSP module substrate (S / F: electrolytic Ni / Au, size 12×12 mm) was coated with flux (WF-6400, manufactured by Senju Metal Industries, Ltd.) and then loaded with solder balls. Then, reflow soldering is performed (220°C or higher, 40 seconds, peak temperature 245°C) to obtain a CSP with solder ball electrodes. Furthermore, an electrode pattern (S / F:Cu-OSP) was printed on a glass epoxy substrate (FR-4, 30×120 mm, 0.8 mm thick) using solder paste. The solder paste contained a solder alloy powder consisting of 3% Ag by mass, 0.5% Cu by mass, and the remainder Sn. Then, the CSP with solder ball electrodes and the printed glass epoxy substrate were reflowed (above 220°C, 40 seconds, peak temperature 245°C) to produce an evaluation substrate. Cross-sections of the evaluation substrates after soldering were observed using a field-emission scanning electron microscope (JSM-7000F, manufactured by JEOL Ltd.). The observation area was the IMC at the CSP side of the bonding interface. IMC thickness was measured using image processing software (Scandium, manufactured by Olympus). The evaluation results of Test Examples A1 to A15 and Test Examples B1 to B16 are shown in Tables 1 and 2.

[0128] Judgment criteria: A: The thickness of the IMC layer is less than 1.4 μm. B: The thickness of the IMC layer is greater than 1.4 μm.

[0129] Evaluation of the Size of Ag3Sn Solder balls with a diameter of 0.3 mm were produced using the solder alloy powders of each test example. After applying flux (WF-6317 manufactured by Senju Metal Industries, Ltd.) on the electrodes (S / F: Cu-OSP), the obtained solder balls were mounted. Reflow soldering was performed using a reflow device (SNR-615 manufactured by Senju Metal Industries, Ltd.) (peak temperature 245° C., cooling rate 2° C. / s). The cross-section of the welded sample was observed using a field-emission scanning electron microscope (JSM-7000F, manufactured by JEOL Ltd.). The evaluation results of Test Examples A1 to A15 and Test Examples B1 to B16 are shown in Tables 1 and 2.

[0130] Judgment criteria: A: The maximum length of Ag3Sn is less than 5μm. B: The maximum length of Ag3Sn is greater than 5 μm and less than 90 μm. C: The maximum length of Ag3Sn is above 90 μm.

[0131] Evaluation of discoloration resistance Solder balls with a diameter of 0.3 mm were produced using the solder alloy powders of each example. The solder balls were left to stand in a highly accelerated life test apparatus (HAST chamber, ESPEC Co., Ltd.: EHS-211M). Set the temperature at 125°C / 100% RH and visually check for discoloration of the solder balls after 4 hours. The evaluation results of Test Examples A1 to A15 and Test Examples B1 to B16 are shown in Tables 1 and 2.

[0132] Judgment criteria: A: The solder balls are discolored. B: The solder balls did not change color.

[0133] Evaluation of Wettability Solder balls with a diameter of 0.3 mm were produced using the solder alloy powders of each example. After applying flux (WF-6317 manufactured by Senju Metal Industries, Ltd.) to a substrate (S / F: Cu-OSP), the obtained solder balls were mounted. Then, reflow soldering is performed (above 220°C, 40 seconds, peak temperature 245°C). After reflow, the length of the wetted spread was measured using a digital microscope (VHX-6000 manufactured by Keyence Co., Ltd.). The evaluation results of Test Examples A1 to A15 and Test Examples B1 to B16 are shown in Tables 1 and 2.

[0134] Judgment criteria: A: The wetted and expanded length is 1000 μm or more. B: The wetted spread length is less than 1000 μm.

[0135] 《Evaluation of Solder Joint Strength》 Solder balls with a diameter of 0.76 mm were produced using the solder alloy powders of each example. After applying flux (WF-6400, manufactured by Senju Metal Industries, Ltd.) on a substrate treated with electrolytic Ni / Au, solder balls were placed on it. Then, reflow soldering is performed (above 220°C, 40 seconds, peak temperature 245°C). After welding, the samples were subjected to a tensile test using a Dage 4000HS (manufactured by Nordson Advanced Technology Co., Ltd.) at a test speed of 1000 μm / s. The number of tests was set to N = 20. The evaluation results of Test Examples A1 to A15 and Test Examples B1 to B16 are shown in Tables 1 and 2.

[0136] Judgment criteria: A: The percentage of IMC layer damage in all tests is less than 50%. B: The percentage of tests in which the IMC layer was destroyed exceeds 50% of the total number of tests.

[0137] [Table 1]

[0138] [Table 2]

[0139] As shown in Table 1, the thickness of the IMC layer of Test Examples A1 to A15 corresponding to the fourth embodiment or the fifth embodiment was evaluated as A. In addition, the evaluation of the thickness of the IMC layer of Test Examples B1 to B2 and Test Examples B7 to B16, in which the Cu content was 0.7 to 1.0 mass % and the Ni content was 0.040 to 0.095 mass % or less, was A. On the other hand, in Test Examples B3 to B6, in which the Cu or Ni content was outside the above range, the evaluation of the thickness of the IMC layer was B.

[0140] As shown in Table 1, the evaluation of the size of Ag3Sn in Test Examples A1 to A15 corresponding to the fourth embodiment or the fifth embodiment was A or B. In Test Examples A1, A3 to A14, B1, and B3 to B15, in which the Ag content was 3.5% by mass or less, the evaluation of the size of Ag3Sn was A. In addition, in Test Example A2 and Test Example B16, in which the Ag content was 4.0 mass %, the evaluation of the size of Ag3Sn was B. On the other hand, in Test Example B2 in which the Ag content exceeded 4.0 mass %, the evaluation of the size of Ag 3 Sn was C.

[0141] As shown in Table 1, the discoloration resistance of Test Examples A1 to A15 corresponding to the fourth embodiment or the fifth embodiment was evaluated as A. In addition, the test examples B1 to B8 and the test examples B10 to B12 in which the Ge content was 0.007 mass % or more were evaluated as A in terms of discoloration resistance. On the other hand, Test Examples B9, B13 to B16, in which the Ge content was less than 0.007 mass %, were evaluated as B in terms of discoloration resistance.

[0142] As shown in Table 1, the wettability evaluation of Test Examples A1 to A15 corresponding to the fourth embodiment or the fifth embodiment was A. In addition, the wettability of test examples B2 to B3, B5, B8 to B9 was evaluated as A. On the other hand, the wettability of Test Examples B1, B6, and B11 to B13, which satisfy 0.017≦Ni / (Ag+Bi) and (Cu / Ni)×(Ag+Bi)≦46, was evaluated as B. In addition, the wettability of Test Example B4 in which the Cu content exceeded 1.0 mass % was evaluated as B. In addition, the wettability of Test Example B7, in which the Bi content was less than 0.1 mass %, was evaluated as B. In addition, the wettability of Test Example B10 in which the Ge content exceeded 0.015 mass % was evaluated as B. In addition, the wettability of Test Example B14, in which the content of Ag or Bi was insufficient, was evaluated as B.

[0143] As shown in Table 1, the evaluation of the strength of the solder joints of Test Examples A1 to A15 corresponding to the fourth embodiment or the fifth embodiment was A. In addition, the strength of the solder joints of Test Examples B1 to B8, Test Example B9, and Test Examples B11 to B16 containing 1.0 to 4.0 mass % of Ag, 0.7 to 1.0 mass % of Cu, 0.1 to 7.0 mass % of Bi, 0.040 to 0.095 mass % of Ni, and 0.015 mass % or less of Ge was evaluated as A. On the other hand, the strength of the solder joints of Test Examples B1 and B2, in which the Ag content was outside the above range, was evaluated as B. In addition, the strength of the solder joints of Test Examples B3 and B4, in which the Cu content was outside the above range, was evaluated as B. In addition, the strength of the solder joints of Test Examples B5 and B6, in which the Ni content was outside the above range, was evaluated as B. In addition, in test examples B7 and B8 in which the Bi content was outside the predetermined range, the evaluation of the strength of the solder joint was B. In addition, the strength of the solder joint portion of Test Example B10, in which the Ge content exceeded 0.015 mass %, was evaluated as B.

[0144] As described above, the solder alloys of the fourth and fifth embodiments exhibit the following effects. The aforementioned solder alloy can reduce the thickness of the intermetallic compound layer at the bonding interface. Furthermore, the solder alloy can fully precipitate fine Ag3Sn and reduce the amount of coarse Ag3Sn precipitated. Furthermore, the solder alloy of the fifth embodiment can suppress discoloration of the alloy. Furthermore, the solder alloy of the fifth embodiment can improve the strength of the joint after soldering. The aforementioned solder alloys can improve wettability.

[0145] Furthermore, using the solder alloy powder prepared above, the solidus temperature and liquidus temperature were measured according to the procedure described in "(1) Measurement of Solidus Temperature and Liquidus Temperature." Furthermore, using the solder alloy powder prepared above, the tensile strength was measured according to the procedure described in "(2) Measurement of Tensile Strength and Elongation." The measurement results are shown in Tables 3 and 4. Test Examples A1 to A15 have melting points around 230° C. and tensile strengths of 50 MPa or more.

[0146] [Table 3]

[0147] [Table 4] [Possibility of Industrial Application]

[0148] According to the present invention, a lead-free and antimony-free solder alloy, solder ball, and solder joint having a melting point of approximately 230°C and a tensile strength of 50 MPa or greater can be provided. The solder alloy, solder ball, and solder joint are suitable for use in QFPs.

Claims

1. A lead-free and antimony-free solder alloy having an alloy composition comprising Ag: 1.0 to 4.0 wt%, Cu: 0.1 to 1.0 wt%, Bi: 0.1 to 9.0 wt%, Ni: 0.005 to 0.3 wt%, Ge: 0.007 to 0.015 wt%, and the remainder being Sn.

2. A lead-free and antimony-free solder alloy having an alloy composition comprising Ag: 1.0 to 4.0 wt%, Cu: 0.1 to 1.0 wt%, Bi: 0.1 to 9.0 wt%, Ni: 0.005 to 0.3 wt%, Ge: 0.007 to 0.012 wt%, Co: 0.001 to 0.1 wt%, and the remainder being Sn; the solder alloy having a tensile strength of 50 MPa or more, wherein the aforementioned alloy composition satisfies 46 < (Cu / Ni) × (Ag + Bi) < 120, where Cu, Ni, Ag, and Bi represent the content of the aforementioned alloy composition in units of mass.

3. The solder alloy as described in claim 2, wherein, The difference between the liquidus temperature and the solidus temperature of the aforementioned solder alloy is less than 30°C.

4. The solder alloy as described in claim 2 or 3, wherein, The aforementioned alloy composition satisfies 0.007 < Ni / (Ag+Bi) < 0.017, the aforementioned alloy composition satisfies 0.2≦Ag / Bi≦15.0, where Cu, Ni, Ag and Bi respectively represent the content of the aforementioned alloy composition, and their units are by mass.

5. A solder ball comprising the solder alloy described in claim 1 or 2.

6. The solder balls as described in claim 5 have an average particle size of 1 to 1000 μm.

7. The solder balls as described in claim 5 have a sphericity of 0.95 or higher.

8. The solder balls as described in claim 7 have a sphericity of 0.99 or higher.

9. A ball grid array formed using solder balls as described in claim 5.

10. A solder joint made using the solder alloy described in claim 1 or 2.