Metal powder sintering paste and method of producing the same, and method of producing conductive material

Patent metadata

Field	Value
Publication number	US-10941304-B2
Application number	US-201715477868-A
Country	US
Kind code	B2
Filing date	Apr 3, 2017
Priority date	Apr 4, 2016
Publication date	Mar 9, 2021
Grant date	Mar 9, 2021

Abstract

There is a problem that when a silver powder sintering paste that is substantially free from resin is used, an organic solvent used as a dispersion medium bleeds, which results in contamination and wire bonding defects. In order to solve the problem, provided is a metal powder sintering paste that contains, as a principal component, silver particles having an average particle diameter (a median diameter) of 0.3 μm to 5 μm and further contains an anionic surfactant but is substantially free from resin.

First claim

What is claimed is:

1. A metal powder sintering paste,
the paste comprising, as a principal component, silver particles having a median diameter of 0.3 μm to 5 μm, and
further comprising an anionic surfactant, and
being substantially free from resin,

wherein
the surfactant is one in which when the temperature is increased with thermogravimetric-differential thermal analysis (TG-DTA) from room temperature to 350° C. at 2° C./min, a residue is reduced to not more than 20% by mass with respect to the initial mass, and

wherein
a content of the surfactant is not more than 2% by mass with respect to the paste.

2. The metal powder sintering paste according to claim 1 , wherein
the surfactant is a saturated carboxylic acid represented by Formula (I) below:
R 1 O(CH 2 CH(R 2 )O) n1 CH 2 COOR 3   (I)

wherein R 1 is a linear or branched alkyl group having at least 7 carbon atoms,
R 2 is any one of —H, —CH 3 , —CH 2 CH 3 , and —CH 2 CH 2 CH 3 ,
R 3 is —H or alkali metal, and
n1 is in a range of 2 to 5.

3. The metal powder sintering paste according to claim 1 , wherein
the surfactant is liquid at 25° C.

4. The metal powder sintering paste according to claim 1 , wherein
the silver particles are in a flake form.

5. The metal powder sintering paste according to claim 1 , wherein
in the silver particles, the content of particles with a particle diameter of smaller than 0.3 μm is not more than 5% by mass.

6. The metal powder sintering paste according to claim 5 , wherein
in the silver particles, the content of particles with a particle diameter of smaller than 0.5 μm is not more than 15% by mass.

7. The metal powder sintering paste according to claim 1 , wherein
the metal powder sintering paste further comprises an organic solvent as a dispersion medium.

8. The metal powder sintering paste according to claim 7 , wherein
the organic solvent has a boiling point in a range of 150 to 250° C.

9. The metal powder sintering paste according to claim 1 , capable of being sintered to form a conductive material having an electric resistance of not higher than 6 μΩ·cm.

10. The metal powder sintering paste according to claim 1 , wherein
the content of the silver particles is at least 70% by mass with respect to the paste.

11. A metal powder sintering paste,
the paste comprising, as a principal component, silver particles having a median diameter of 0.3 μm to 5 μm, and
further comprising an anionic surfactant, and
being substantially free from resin,

wherein
a content of the surfactant is not more than 2% by mass with respect to the paste, and

wherein
a bleed ratio is less than 1.70,
wherein the bleed ratio is calculated as a ratio of a diameter after bleeding to an original diameter of the paste
when the paste is applied onto a substrate having a gold electrode with a surface roughness Ra of 0.04 μm on its surface by a stamping method to have a diameter of 170±50 μm, which then is left to stand for 20 minutes, and
the diameter after bleeding is measured by measuring the diameter including a dispersion medium that had bled.

12. The metal powder sintering paste according to claim 11 , wherein
the surfactant is one in which when the temperature is increased with thermogravimetric-differential thermal analysis (TG-DTA) from room temperature to 350° C. at 2° C./min, a residue is reduced to not more than 20% by mass with respect to the initial mass.

13. The metal powder sintering paste according, to claim 11 , wherein
the surfactant is a saturated carboxylic acid represented by Formula (I) below:
R 1 O(CH 2 CH(R 2 )O) n1 CH 2 COOR 3   (I)

wherein R 1 is a linear or branched alkyl group having at least 7 carbon atoms,
R 2 is any one of —H, —CH 2 CH 3 , and —CH 2 CH 2 CH 3 ,
R 3 is —H or alkali metal, and
n1 is in a range of 2 to 5.

14. The metal powder sintering paste according to claim 11 , wherein
the surfactant is liquid at 25° C.

15. The metal powder sintering paste according to claim 11 , wherein
the silver particles are in a flake form.

16. The metal powder sintering paste according to claim 11 , wherein
in the silver particles, a content of particles with a particle diameter of smaller than 0.3 μm is not more than 5% by mass.

17. The metal powder sintering paste according to claim 16 , wherein
in the silver particles, a content of particles with a particle diameter of smaller than 0.5 μm is not more than 15% by mass.

18. The metal powder sintering paste according to claim 11 , wherein
the metal powder sintering paste further comprises an organic solvent as a dispersion medium.

19. The metal powder sintering paste according to claim 18 , wherein
the organic solvent has a boiling point in a range of 150 to 250° C.

20. The metal powder sintering paste according to claim 11 , capable of being sintered to form a conductive material having an electric resistance of not higher than 6 μΩ·cm.

21. The metal powder sintering paste according to claim 11 , wherein
a content of the silver particles is at least 70% by mass with respect to the paste.

22. A method of producing the metal powder sintering paste according to claim 1 , comprising mixing an anionic surfactant and silver particles having a median diameter of 0.3 μm to 5 μm together but substantially not with resin.

23. A method of producing a conductive material, comprising a step of calcining a metal powder sintering paste according to claim 1 .

24. The method of producing a conductive material according to claim 23 , wherein
the calcining is carried out at a temperature in a range of 160° C. to 300° C.

25. The method of producing a conductive material according to claim 23 , wherein
the calcining is carried out in an air oven at 160° C. to 250° C. for 30 to 120 minutes.

Assignees

• Nichia Corp

Inventors

• Kunimune Teppei
• Kuramoto Masafumi

Classifications

• H10W72/071 Primary

  Connecting or disconnecting · CPC title

• B22F1/068

  Flake-like particles · CPC title

• B22F1/107

  containing organic material comprising solvents, e.g. for slip casting · CPC title

• H01B1/22 Primary

  the conductive material comprising metals or alloys · CPC title

• B22F2201/50

  air · CPC title