High-temperature solder joint material and solder joint body

Abstract

To provide a high-temperature lead-free solder alloy that has high joining reliability at a high temperature suitable for semiconductor joining, is superior in workability, and can be supplied at low cost.SOLUTION: A lead-free solder alloy has a basic composition of Zn-Al-In, and contains 1 to 30 mass% of Al, 0.1 to 50 mass% of In, and Zn and inevitable impurities for the rest to have a lower soldering temperature in joining, and also contains 0.001 to 1.0 mass% of Ga in addition to the basic composition to have improved wettability. The lead-free solder alloy having the basic composition of Zn-Al-In further contains one or two or more kinds selected out of Mn, Li, Sr, Mg, Si, Sn, Ge, Cu, Ag, Sb, and Ni each within a specific range to have a lower joining temperature, thereby improving characteristics of joining strength, wettability, solderability, joining reliability, etc.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a lead-free solder alloy, particularly to a lead-free solder alloy used for high-temperature soldering, a solder joint using this lead-free solder alloy, and an electronic circuit board and an electronic device.

Background Art

[0002] In recent years, in the mounting of electronic components, from the viewpoint of avoiding environmental load, Sn-Ag-Cu-based lead-free solder alloys and Sn-Cu-Ni-based lead-free solder alloys are used for soldering at about 250 °C or lower. However, as a high-temperature solder used for soldering at 250 °C or higher, solder alloys containing Pb at a high concentration, such as Pb5Sn, are widely used.

[0003] And, in addition to the conventional silicon, the need for wide-gap semiconductors made of SiC or GaN has increased for the composition used in power semiconductor devices, and a Pb-free solder alloy is also required as a joining material used for high-temperature solder joints. Therefore, Patent Document 1 discloses a technique using a Zn-Al eutectic alloy joining material, and Patent Document 2 discloses a technique using a Zn-Al-Ag-based solder alloy.

[0004] In Patent Document 1, since it is necessary to hold a Zn-Al eutectic alloy joining material at a temperature of 280 °C to 410 °C for 30 minutes to 3 hours and then rapidly cool it in water at -4 °C to 20 °C to exhibit a superplastic state, it takes time to process the joining material.

[0005] Patent Document 2 discloses a technique related to a Zn-Al-Ag-based lead-free solder alloy having a melting point of about 300 °C to 400 °C.

[0006] However, in the technique disclosed in Patent Document 1, it takes time to process the joining material, and in Patent Document 2, there is a concern that the material cost increases because Ag is contained, and each technique has problems in practicality.

Prior Art Documents

Patent Document

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] In view of such a situation, the present invention provides a lead-free solder alloy for high temperature that has high joint reliability at high temperatures suitable for semiconductor bonding, is excellent in workability, and can be supplied at low cost.

Means for Solving the Problems

[0009] The present invention is a lead-free solder alloy having a basic composition of Zn-Al-In, containing 1 mass% or more and 30 mass% or less of Al, 0.1 mass% or more and 50 mass% or less of In, and the balance being Zn and inevitable impurities, and by containing 0.001 mass% or more and 1.0 mass% or less of Ga in the composition, the wettability is improved.

[0010] Furthermore, in the lead-free solder alloy having the above-mentioned basic composition of Zn-Al-In, one or more selected from Mn, Li, Sr, Mg, Si, Sn, Ge, Cu, Ag, Sb, and Ni are respectively, Mn in an amount of 0.001 mass% or more and 0.5 mass% or less, Li in an amount of 0.01 mass% or more and 0.5 mass% or less, Sr in an amount of 0.001 mass% or more and 0.1 mass% or less, Mg in an amount of 0.001 mass% or more and 0.3 mass% or less, Si in an amount of 0.01 mass% or more and 1.0 mass% or less, Sn in an amount of 0.1 mass% or more and 5.0 mass% or less, Ge in an amount of 0.001 mass% or more and 1.0 mass% or less, Cu in an amount of 0.1 mass% or more and 5.0 mass% or less, Ag is 0.01% by mass or more and 4.0% by mass or less, Sb is 0.01% by mass or more and 3.0% by mass or less, By containing 0.005% by mass or more and 0.5% by mass or less of Ni, the bonding temperature is lowered, and characteristics such as bonding strength, wettability, solderability, and bonding reliability are improved.

Effect of the Invention

[0011] The lead-free solder alloy of the present invention has excellent characteristics even in a high-temperature range of 300°C or higher. Therefore, it is useful for bonding wide-gap semiconductors using SiC or GaN, and for power modules using these. Since the cost is also low, it can be widely applied to the mounting of electronic components.

Brief Description of the Drawings

[0012]

Figure 1

Modes for Carrying Out the Invention

[0013] The embodiments of the present invention will be described below. A lead-free solder alloy having a basic composition of Zn-Al-In of the present invention, characterized by containing 1.0% by mass or more and 30% by mass or less of Al, 0.1% by mass or more and 50% by mass or less of In, and the balance containing Zn and unavoidable impurities. Further, as the content of Al, 18% by mass or more and 28% by mass or less is preferable for semiconductor bonding applications. Zn-Al-based alloys are widely known for the Zn22Al composition and are applied to bonding using superplastic characteristics, but bonding in a high-temperature range close to 400°C is required. However, most of the semiconductor components used in power devices have extremely low heat resistance of 400°C or higher, and are not suitable for semiconductor bonding in reality. Therefore, in the present invention, in order to have the characteristics of a Zn-Al alloy, lower the melting point of the alloy, and make a bonding material suitable for semiconductor bonding, In is contained to lower the melting point.

[0014] In addition, by adding Ga to the Zn-Al-In alloy composition which is the basic composition of the present invention, the wettability was improved and the soldering characteristics were successfully improved.

[0015] As the amount of Ga contained in the Zn-Al-In alloy composition which is the basic composition of the present invention, 0.001 mass% or more and 1.0 mass% or less is preferable.

[0016] Furthermore, by adding one or more selected from Mn, Li, Sr, Mg, Si, Sn, Ge, Cu, Ag, Sb, and Ni to the Zn-Al-In alloy composition which is the basic composition of the present invention and the alloy composition containing Ga in the basic composition, characteristics such as the following joint strength, joint reliability, and solderability are remarkably improved.

[0017] By containing Mn in an amount of 0.001 mass% or more and 0.5 mass% or less, the joint strength and joint reliability are improved.

[0018] By containing Li in an amount of 0.01 mass% or more and 0.5 mass% or less, the solderability can be improved.

[0019] By containing Sr in an amount of 0.001 mass% or more and 0.1 mass% or less, the solderability is improved. And, as a more preferable content, it is 0.01 mass% or more and 0.05 mass%.

[0020] By containing Mg in an amount of 0.001 mass% or more and 0.3 mass% or less, the joint strength is improved. And, as a more preferable content, it is 0.01 mass% or more and 0.1 mass% or less.

[0021] By containing Si in an amount of 0.01 mass% or more and 1.0 mass% or less, the joint strength is improved.

[0022] By containing Sn in an amount of 0.1 mass% or more and 5.0 mass% or less, the corrosion of the joint part is suppressed and the joint reliability is improved. And more preferably, the content is 0.3% by mass or more and 3.0% by mass or less.

[0023] By containing 0.001% by mass or more and 1.0% by mass or less of Ge, oxidation during soldering is prevented.

[0024] By containing 0.1% by mass or more and 5.0% by mass or less of Cu, corrosion of the joint part is suppressed and joint reliability is improved. And more preferably, the content is 1.0% by mass or more and 3.0% by mass or less.

[0025] By containing 0.01% by mass or more and 4.0% by mass or less of Ag, the melting point is lowered and wettability is also improved.

[0026] By containing 0.01% by mass or more and 3.0% by mass or less of Sb, the bonding strength is improved.

[0027] By containing 0.005% by mass or more and 0.5% by mass or less of Ni, corrosion of the joint part is suppressed and joint reliability is improved. And more preferably, the content is 0.01% by mass or more and 0.1% by mass or less.

Examples

[0028] Hereinafter, the present invention will be described in detail based on examples. (Lowering of melting point)

[0029] Table 1 shows the solidus point and liquidus point when 5% by mass of In is contained in the Zn-22Al composition which is the basic composition of the present invention.

[0030]

Table 1

[0031] As shown in Table 1, the Zn-22Al-5In composition has a solidus point of 366 °C, and it can be seen that the solidus point is lowered by 57 °C compared with the Zn22Al composition.

[0032] Furthermore, it has been found that the lead-free alloy based on Zn-Al-In of the present invention is also suitable for joining aluminum materials. By incorporating In, the joining temperature can be lowered compared to conventional aluminum joining materials such as Zn-22Al. This results in less load on the materials to be joined and enables a reduction in the temperature during joining compared to conventional joining materials, contributing to the reduction of carbon dioxide emissions.

[0033] Furthermore, by adding one or more elements selected from Mn, Li, Sr, Mg, Si, Sn, Ge, Cu, Ag, Sb, and Ni to the lead-free solder alloy based on Zn-Al-In and the composition containing Ga in the lead-free solder alloy, it is possible to improve corrosion resistance, wettability, joint strength, and joint reliability.

Industrial Applicability

[0034] The lead-free alloy based on Zn-Al-In of the present invention can be joined at a lower temperature compared to conventional Zn-Al-based solder alloys and can be provided at a lower cost. Therefore, it is expected to be widely used as a joining material for power semiconductors using SiC or GaN and as a joining material for aluminum materials.

Claims

1. A lead-free solder alloy having Al, In, and Zn as the basic components, wherein the lead-free solder alloy contains 1% by mass or more and 30% by mass or less of Al, 0.1% by mass or more and 50% by mass or less of In, 25% by mass or more and 99% by mass or less of Zn, and further contains inevitable impurities, and is a Zn-Al-In-based lead-free solder alloy.

2. The lead-free solder alloy according to Claim 1, wherein the Zn-Al-In-based lead-free solder alloy contains 0.001% by mass or more and 1.0% by mass or less of Ga.

3. The Zn-Al-In-based lead-free solder alloy according to Claims 1 and 2, which contains one or more selected from Mn, Li, Sr, Mg, Si, Sn, Ge, Cu, Ag, Sb, and Ni.

4. A joint part and a solder joint joined using the Zn-Al-In-based lead-free solder alloy according to any one of Claims 1 to 3, and an electric circuit and an electronic device in which the electronic component is joined to a substrate.

5. A joint part and a solder joint of an aluminum material using the Zn-Al-In-based lead-free solder alloy according to any one of Claims 1 to 3.

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