# US 11,992,902 B2 · Solder alloy and solder joint

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- Number: US 11,992,902 B2
- Document ID: US11992902B2
- Status: Granted
- Kind: B2
- Application number: 17/896,321
- Filed: 2022-08-26
- Published: 2023-03-16
- Granted: 2024-05-28
- Earliest claimed: 2021-08-27
- Assignees: Senju Metal Industry Co., Ltd.
- Applicants: Senju Metal Industry Co., Ltd.
- Inventors: Takahiro Yokoyama; Shunsaku Yoshikawa
- Web page: https://patentgrep.com/patent/US11992902B2

## CPC

- B23K 35/262: {Sn as the principal constituent}
- B23K 35/0222: {for use in soldering or brazing (B23K35/0205 takes precedence)}
- C22C 1/02: by melting {(C22C1/1036 takes precedence)}
- C22C 1/03: using master alloys
- C22C 13/00: Alloys based on tin
- B23K 2101/42: Printed circuits
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

Provided are a solder alloy and a solder joint, which have a narrow ΔT to suppress solder bridges and solder icicles, and a small amount of dross generated in a solder tank, suppress Cu leaching, and have higher strength. The solder alloy has an alloy composition of, by mass %, Cu: more than 2.0% and less than 3.0%; Ni: 0.010% or more and less than 0.30%; and Ge: 0.0010 to 0.20% with the balance being Sn. Preferably, by mass %, Cu is more than 2.5% and less than 3.0%, and the alloy composition satisfies the following relations (1) and (2): 2.400≤Cu+Ni+Ge≤3.190 (1), and 0.33≤Ge/Ni≤1.04 (2). Cu, Ni, and Ge in the relations (1) and (2) each represent the contents (mass %) in the alloy composition.

## Claims

### Claim 1

A solder alloy having an alloy composition consisting of, by mass %:
Cu: more than 2.0% and less than 3.0%,
Ni: 0.10% or more and less than 0.30%, and
Ge: 0.0010 to 0.20%, with the balance being Sn,
wherein the alloy composition satisfies the following relations (1) and (2):
2.700%≤Cu+Ni+Ge≤3.190% relation (1)
0.33≤Ge/Ni≤1.04 relation (2)
wherein Cu, Ni, and Ge in the relations (1) and (2) each represent the contents (mass %) thereof in the alloy composition, and
wherein the solder alloy comprises the following properties:
a ΔT that is obtained by subtracting a solidus temperature from a liquidus temperature is less than 110° C.,
no solder bridges or solder icicles are observed after flow soldering at a temperature of 255° C.,
a tensile strength measured in accordance with JIS Z 3198-2 (2003) is 38 MPa or more,
a dross weight is 25 g or less, and
a dimension of copper wiring on a test sample is not reduced by half after immersion of seven times or more in jetting molten solder.

### Claim 2 (depends on 1)

The solder alloy according to claim 1, wherein, by mass %, Cu: more than 2.5% and less than 3.0%.

### Claim 3 (depends on 1)

A solder joint, comprising a solder alloy, wherein the solder alloy is the solder alloy according to claim 1.

### Claim 4 (depends on 2)

A solder joint, comprising a solder alloy, wherein the solder alloy is the solder alloy according to claim 2.