Assembly method by silver sintering without pressure

Patent metadata

Field	Value
Publication number	US-10828697-B2
Application number	US-201615760056-A
Country	US
Kind code	B2
Filing date	Sep 15, 2016
Priority date	Sep 15, 2015
Publication date	Nov 10, 2020
Grant date	Nov 10, 2020

Abstract

An assembly method for assembling a first element to a second element by pressureless metal sintering, the method having a preparation step during which a sintering material is arranged at a bond interface of the elements, a pre-sintering step during which the assembly is heated for a first duration that is longer than five minutes at a first temperature that is higher than 200° C. and strictly lower than or equal to the temperature for activating diffusion at the grain boundaries, and a densification step during which the assembly is heated for a second duration at a second temperature that is higher than or equal to the temperature for activating diffusion at the grain boundaries.

First claim

The invention claimed is:

1. An assembly method for assembling a first element to a second element by pressureless metal sintering, the method comprising the following steps:
a) a preparation step, during which a sintering material comprising predominantly metal particles is arranged at a bond interface of the first element and the second element, the sintering material having a greatest dimension lying in the range of 0.5 μm to about 50 μm;
b) a pre-sintering step, during which the assembly constituted by the first element, the second element, and the sintering material is heated for a first duration that is longer than five minutes at a first temperature that is lower than a temperature for activating diffusion at grain boundaries;
c) a densification step, during which the assembly is heated for a second duration at a second temperature that is higher than or equal to the temperature for activating diffusion at the grain boundaries,
wherein the sintering material comprises at least about 80% flake-type metal particles having a form factor (f) that is less than 0.3,
wherein the sintering material is a powder.

2. The method according to claim 1 , wherein the sintering material comprises predominantly metal particles has a greatest dimension lying in the range of 0.7 μm to 5 μm.

3. The method according to claim 1 , wherein the metal particles are silver particles and the first temperature lies in the range of 200° C. to 300° C.

4. The method according to claim 1 , wherein the metal particles are silver particles and the second temperature lies in the range of 450° C. to 550° C.

5. The method according to claim 1 , wherein the metal particles are gold particles and the first temperature lies in the range of 300° C. to 400° C.

6. The method according to claim 1 , wherein the metal particles are gold particles and the second temperature lies in the range of 480° C. to 700° C.

7. The method according to claim 1 , wherein the first temperature is varied during the first duration.

8. The method according to claim 1 , wherein the second temperature is varied during the second duration.

9. The method according to claim 1 , further comprising a relaxation step, subsequent to the densification step, during which the assembly is stoved at a temperature lying in the range of 0.3 Tf to 0.5 Tf, where Tf is the melting temperature of the sintering material in Kelvin, for a third duration.

10. The method according to claim 9 , wherein the third duration lies in the range of thirty minutes to thirty hours.

11. The method according to claim 1 , comprising an idle-time step situated between the pre-sintering step and the densification step, during which the assembly is returned to the ambient temperature.

12. The method according to claim 1 , comprising a debinding step that is performed between the preparation step and the pre-sintering step, during which the assembly is stoved at a temperature lying in the range of 50° C. to 100° C.

Assignees

• Safran Electronics & Defense

Inventors

• Geoffroy Thomas
• Riou Jean-Christophe
• Bailly Eric

Classifications

• B22F1/10

  Metallic powder containing lubricating or binding agents; Metallic powder containing organic material · CPC title

• H05K3/3494 Primary

  Heating processes for reflow soldering · CPC title

• H05K3/32

  electrically connecting electric components or wires to printed circuits · CPC title

• H05K3/3442

  having edge contacts, e.g. leadless chip capacitors, chip carriers · CPC title

• H05K2203/1131

  Sintering, i.e. fusing of metal particles to achieve or improve electrical conductivity · CPC title