# US 11,999,018 B2 · SnBi and SnIn solder alloys

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- Number: US 11,999,018 B2
- Document ID: US11999018B2
- Status: Granted
- Kind: B2
- Application number: 16/557,587
- Filed: 2019-08-30
- Published: 2020-03-05
- Granted: 2024-06-04
- Earliest claimed: 2018-08-31
- Assignees: Indium Corporation
- Applicants: Indium Corporation
- Inventors: Francis M. Mutuku; Ning-Cheng Lee; Hongwen Zhang
- Web page: https://patentgrep.com/patent/US11999018B2

## CPC

- B23K 35/262: {Sn as the principal constituent}
- B23K 35/0244: {Powders, particles or spheres; Preforms made therefrom}
- B23K 35/025: {Pastes, creams or slurries}
- B23K 35/264: {Bi as the principal constituent}
- C22C 12/00: Alloys based on antimony or bismuth
- C22C 13/02: with antimony or bismuth as the next major constituent
- C22C 30/06: containing zinc
- 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

Some implementations of the disclosure are directed to low melting temperature (e.g., liquidus temperature below 210° C.) SnBi or Snln solder alloys. A SnBi solder alloy may consist of 2 to 60 wt % Bi; optionally, one or more of: up to 16 wt % In, up to 4.5 wt % Ag, up to 2 wt % Cu, up to 12 wt % Sb, up to 2.5 wt % Zn, up to 1.5 wt % Ni, up to 1.5 wt % Co, up to 1.5 wt % Ge, up to 1.5 wt % P, and up to 1.5 wt % Mn; and a remainder of Sn. A Snln solder alloy may consist of: 8 to 20 wt % In; optionally, one or more of: up to 12 wt % Bi, up to 4 wt % Ag, up to 5 wt % Sb, up to 3 wt % Cu, up to 2.5 wt % Zn, up to 1.5 wt % Ni, up to 1.5 wt % Co, up to 1.5 wt % Ge, up to 1.5 wt % P, and up to 1.5 wt % Mn; and a remainder of Sn.

## Claims

### Claim 1

A solder alloy, consisting of:
50 wt % to 60 wt % Bi;
about 0.02 wt % Ni;
greater than 0 wt % to 2 wt % Ag;
greater than 0 wt % to 1 wt % Cu; and
a remainder of Sn, wherein the solder alloy has a liquidus temperature of less than 200° C.

### Claim 2 (depends on 1)

The solder alloy of claim 1, wherein the difference between the liquidus temperature of the solder alloy and a solidus temperature of the solder alloy is less than 20° C.

### Claim 3 (depends on 2)

The solder alloy of claim 2, wherein the liquidus temperature of the solder alloy is between 140° C. and 160° C.

### Claim 4 (depends on 1)

The solder alloy of claim 1, wherein the solder alloy has a yield strength between 50 and 80 MPa at room temperature.

### Claim 5 (depends on 1)

The solder alloy of claim 1, wherein the solder alloy has a tensile strength between 70 and 100 MPa at room temperature.

### Claim 6 (depends on 5)

The solder alloy of claim 5, wherein the liquidus temperature of the solder alloy is between 140° C. and 200° C.

### Claim 7 (depends on 1)

The solder alloy of claim 1, wherein the solder alloy includes: about 40.8 wt % Sn, about 57.8 wt % Bi, about 1.2 wt % Ag, about 0.2 wt % Cu, and about 0.02 wt % Ni.

### Claim 8 (depends on 1)

The solder alloy of claim 1, wherein the solder alloy is a solder powder.

### Claim 9 (depends on 1)

The solder alloy of claim 1, wherein the solder alloy is a solder ball.

### Claim 10 (depends on 1)

The solder alloy of claim 1, wherein the solder alloy is a solder preform.

### Claim 11

A solder paste, comprising:
flux; and
a solder alloy consisting of 50 wt % to 60 wt % Bi; about 0.02 wt % Ni; greater than 0 wt % to 2 wt % Ag; greater than 0 wt % to 1 wt % Cu; and a remainder of Sn, wherein the solder alloy has a liquidus temperature of less than 200° C.

### Claim 12 (depends on 11)

The solder paste of claim 11, wherein the solder alloy consists of about 40.8 wt % Sn, about 57.8 wt % Bi, about 1.2 wt % Ag, about 0.2 wt % Cu, and about 0.02 wt % Ni.