Liquid metal infiltration rework of electronic assembly

Patent metadata

Field	Value
Publication number	US-11278977-B2
Application number	US-201916659764-A
Country	US
Kind code	B2
Filing date	Oct 22, 2019
Priority date	Oct 22, 2019
Publication date	Mar 22, 2022
Grant date	Mar 22, 2022

Abstract

Provided is a method for removing an electronic socket from a printed wiring board. The method comprises placing an embrittlement sheet over an electronic socket on a printed wiring board. The electronic socket is mounted to the printed wiring board using a plurality of hidden solder joints. The method further comprises causing the embrittlement sheet to melt. The melted embrittlement sheet wets the plurality of hidden solder joints. The electronic socket is removed from the printed wiring board by breaking the embrittled solder joints.

First claim

What is claimed is:

1. A method comprising:
placing an embrittlement sheet over an electronic socket on a printed wiring board, wherein the electronic socket is mounted to the printed wiring board using a plurality of hidden solder joints;
causing the embrittlement sheet to melt such that the melted embrittlement sheet wets the plurality of hidden solder joints; and
removing the electronic socket from the printed wiring board by breaking the embrittled solder joints.

2. The method of claim 1 , the method further comprising:
applying a pre-fluxing agent on the electronic socket prior to placing the embrittlement sheet over the electronic socket,
wherein causing the embrittlement sheet to melt comprises applying backside heating of the printed wiring board to heat the embrittlement sheet above a reflow temperature of the embrittlement sheet.

3. The method of claim 2 , wherein the causing the embrittlement sheet to melt further comprises applying frontside heating of the printed wiring board, wherein the method further comprises:
holding the embrittlement sheet at the reflow temperature for an amount of time to allow the embrittlement sheet to at least partially diffuse into the solder joints,
wherein the amount of time and the reflow temperature are based on the composition of the embrittlement sheet.

4. The method of claim 2 , the method further comprising:
placing a Teflon sheet over the embrittlement sheet; and
applying a mechanical force to the Teflon sheet, wherein the mechanical force increases a contact force between the embrittlement sheet and one or more contact pins in the electronic socket.

5. The method of claim 1 , wherein the embrittlement sheet is a planar sheet that comprises one or more metal particles that, when melted, cause liquid metal embrittlement of the solder joints.

6. The method of claim 1 , wherein the embrittlement sheet is a composition that include one or more metals selected from the group consisting of elemental gallium, a gallium-tin alloy, a gallium-indium alloy, and a gallium-tin-indium alloy.

7. The method of claim 6 , wherein the embrittlement sheet further include one or more metals selected from the group consisting of elemental copper, a copper alloy, elemental silver, a silver alloy, elemental antimony, and an antimony alloy.

8. The method of claim 1 , wherein removing the electronic socket from the printed wiring board comprises applying a mechanical force to break the plurality of hidden solder joints.

9. The method of claim 1 , the method further comprising:
removing, after removing the electronic socket, 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 socket on the printed wiring board in place of the electronic socket; and
attaching the new electronic socket using a reflow soldering process.

10. The method of claim 1 , wherein the electronic socket is a hybrid land grid array (HLGA) socket.

11. A system comprising:
a memory; and
a processor communicatively coupled to the memory, wherein the processor is configured to perform a method comprising:
placing an embrittlement sheet over an electronic socket on a printed wiring board, wherein the electronic socket is mounted to the printed wiring board using a plurality of hidden solder joints;
causing the embrittlement sheet to melt such that the melted embrittlement sheet wets the plurality of hidden solder joints; and
removing the electronic socket from the printed wiring board by breaking the embrittled solder joints.

12. The system of claim 11 , wherein the method further comprises:
applying a pre-fluxing agent on the electronic socket prior to placing the embrittlement sheet over the electronic socket,
wherein causing the embrittlement sheet to melt comprises applying backside heating of the printed wiring board to heat the embrittlement sheet above a reflow temperature of the embrittlement sheet.

13. The system of claim 12 , wherein the causing the embrittlement sheet to melt further comprises applying frontside heating of the printed wiring board, wherein the method further comprises:
holding the embrittlement sheet at the reflow temperature for an amount of time to allow the embrittlement sheet to at least partially diffuse into the solder joints,
wherein the amount of time and the reflow temperature are based on the composition of the embrittlement sheet.

14. The system of claim 12 , wherein the method further comprises:
placing a Teflon sheet over the embrittlement sheet; and
applying a mechanical force to the Teflon sheet, wherein the mechanical force increases a contact force between the embrittlement sheet and one or more contact pins in the electronic socket.

15. The system of claim 11 , wherein the method further comprises:
removing, after removing the electronic socket, 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 socket on the printed wiring board in place of the electronic socket; and
attaching the new electronic socket using a reflow soldering process.

16. A computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the processor to perform a method comprising:
placing an embrittlement sheet over an electronic socket on a printed wiring board, wherein the electronic socket is mounted to the printed wiring board using a plurality of hidden solder joints;
causing the embrittlement sheet to melt such that the melted embrittlement sheet wets the plurality of hidden solder joints; and
removing the electronic socket from the printed wiring board by breaking the embrittled solder joints.

17. The computer program product of claim 16 , wherein the method further comprises:
applying a pre-fluxing agent on the electronic socket prior to placing the embrittlement sheet over the electronic socket,
wherein causing the embrittlement sheet to melt comprises applying backside heating of the printed wiring board to heat the embrittlement sheet above a reflow temperature of the embrittlement sheet.

18. The computer program product of claim 17 , wherein the causing the embrittlement sheet to melt further comprises applying frontside heating of the printed wiring board, wherein the method further comprises:
holding the embrittlement sheet at the reflow temperature for an amount of time to allow the embrittlement sheet to at least partially diffuse into the solder joints,
wherein the amount of time and the reflow temperature are based on the composition of the embrittlement sheet.

19. The computer program product of claim 17 , wherein the method further comprises:
placing a Teflon sheet over the embrittlement sheet; and
applying a mechanical force to the Teflon sheet, wherein the mechanical force increases a contact force between the embrittlement sheet and one or more contact pins in the electronic socket.

20. The computer program product of claim 16 , wherein the method further comprises:
removing, after removing the electronic socket, 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 socket on the printed wiring board in place of the electronic socket; and
attaching the new

Assignees

• IBM

Inventors

• Hoffmeyer Mark K
• Younger Timothy P

Classifications

• H05K3/3436

  having an array of bottom contacts, e.g. pad grid array or ball grid array components · CPC title

• H05K2203/176

  Removing, replacing or disconnecting component; Easily removable component · CPC title

• B23K1/018 Primary

  Unsoldering; Removal of melted solder or other residues · CPC title

• B23K2101/42

  Printed circuits · CPC title

• H05K2201/10719

  Land grid array [LGA] · CPC title