# US 11,310,950 B2 · Liquid metal infiltration rework of electronic assembly

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- Number: US 11,310,950 B2
- Document ID: US11310950B2
- Status: Granted
- Kind: B2
- Application number: 16/659,750
- Filed: 2019-10-22
- Published: 2021-04-22
- Granted: 2022-04-19
- Earliest claimed: 2019-10-22
- Assignees: International Business Machines Corporation
- Applicants: International Business Machines Corporation
- Inventors: Mark K. Hoffmeyer; Timothy P. Younger
- Web page: https://patentgrep.com/patent/US11310950B2

## CPC

- H05K 13/0486: {Replacement and removal of components}
- B23K 1/0016: {Soldering of electronic components}
- B23K 1/018: Unsoldering; Removal of melted solder or other residues
- H05K 2203/043: Reflowing of solder coated conductors, not during connection of components, e.g. reflowing solder paste
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- 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

## Abstract

Provided is a method for removing an electronic component from a printed wiring board. The method comprises applying an embrittlement agent to a lead of an electronic component that is soldered to the printed wiring board. The electronic component is removed from the printed wiring board by breaking the embrittled lead.

## Claims

### Claim 1

A method comprising:
applying an embrittlement agent to a soldered joint of an electronic component that is soldered to a printed wiring board; and
removing the electronic component from the printed wiring board by breaking the embrittled joint,
wherein the embrittlement agent comprises metal particles, wherein the metal particles include one or more particles selected from the group consisting of elemental copper, a copper alloy, elemental silver, a silver alloy, elemental antimony, and an antimony alloy, and
wherein the metal particles further comprise one or more particles selected from the group consisting of elemental gallium, a gallium-tin alloy, a gallium-indium alloy, and a gallium-tin-indium alloy.

### Claim 2 (depends on 1)

The method of claim 1, wherein the embrittlement agent is a paste comprising metal that causes liquid metal embrittlement when it infiltrates the joint of the electronic component.

### Claim 3 (depends on 1)

The method of claim 1, the method further comprising:
heating the applied embrittlement agent to a temperature that meets or exceeds a reflow temperature of the embrittlement agent; and
holding the embrittlement agent at the temperature for an amount of time to allow the embrittlement agent to at least partially diffuse into the joint,
wherein removing the electronic component from the printed wiring board is performed after the embrittlement agent has at least partially diffused into the joint.

### Claim 4 (depends on 3)

The method of claim 3, wherein the amount of time and the temperature are based on the composition of the embrittlement agent.

### Claim 5 (depends on 1)

The method of claim 1, wherein removing the electronic component from the printed wiring board comprises applying a mechanical force to break the joint of the electronic component.

### Claim 6 (depends on 1)

The method of claim 1, the method further comprising:
removing, after removing the electronic component, residual alloyed solder from the printed wiring board using a vacuum solder tool;
depositing fresh solder paste on pads on the printed wiring board;
placing a new electronic component on the printed wiring board in place of the electronic component; and
attaching the new electronic component using a reflow soldering process.

### Claim 7 (depends on 1)

The method of claim 1, wherein the embrittlement agent further comprises an alcohol emulsion carrier.

### Claim 8 (depends on 1)

The method of claim 1, wherein the embrittlement agent comprises a flux carrier.

### Claim 9

A method comprising:
applying an embrittlement agent to a soldered joint of an electronic component that is soldered to a printed wiring board;
heating the applied embrittlement agent to a temperature that meets or exceeds a reflow temperature of the embrittlement agent;
holding the embrittlement agent at the temperature for an amount of time to allow the embrittlement agent to at least partially diffuse into the joint; and
removing, after the embrittlement agent has at least partially diffused into the joint, the electronic component from the printed wiring board by breaking the embrittled joint,
wherein the embrittlement agent comprises metal particles, wherein the metal particles include one or more particles selected from the group consisting of elemental copper, a copper alloy, elemental silver, a silver alloy, elemental antimony, and an antimony alloy.

### Claim 10 (depends on 9)

The method of claim 9, wherein the embrittlement agent is a paste comprising metal that causes liquid metal embrittlement when it infiltrates the joint of the electronic component.

### Claim 11 (depends on 9)

The method of claim 9, wherein the amount of time and the temperature are based on the composition of the embrittlement agent.

### Claim 12 (depends on 9)

The method of claim 9, wherein removing the electronic component from the printed wiring board comprises applying a mechanical force to break the joint of the electronic component.

### Claim 13 (depends on 9)

The method of claim 9, the method further comprising:
removing, after removing the electronic component, residual alloyed solder from the printed wiring board using a vacuum solder tool;
depositing fresh solder paste on pads on the printed wiring board;
placing a new electronic component on the printed wiring board in place of the electronic component; and
attaching the new electronic component using a reflow soldering process.