Oxide-bondable solder

• US 6,319,617 B1
• Filed: 08/18/2000
• Issued: 11/20/2001
• Est. Priority Date: 12/17/1999
• Status: Expired due to Term

• Current Assignee: Bell Semiconductor, LLC (Hilco Inc. (d/b/a Hilco Global))
• Original Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Inventors: Ramirez, Ainissa G, Kammlott, Guenther Wilhelm, Jin, Sungho, Mavoori, Hareesh
• Primary Examiner(s): Koehler, Robert R.
• Application Number:
  US09/642,216
• Time in Patent Office: 459 Days
• Field of Search: 428/469, 428/450, 428/432, 428/433, 428/434, 420/501, 420/507, 420/513, 420/555, 420/557, 420/563, 420/576, 420/577, 420/416, 420/580, 420/589, 228/101, 228/903, 427/123
• US Class Current: 428/469
• CPC Class Codes: B23K 35/262 Sn as the principal constituent
• CPC Class Codes: B23K 35/3006 Ag as the principal constituent
• CPC Class Codes: B23K 35/3013 Au as the principal constituent
• CPC Class Codes: G02B 6/022 using mechanical stress, e.g. tuning by compression or elongation, special geometrical shapes such as "dog-bone" or taper G02B6/02204 takes precedence; optical modulation using photo-elastic effect G02F1/0131
• CPC Class Codes: G02B 6/4238 Soldering
• CPC Class Codes: Y10S 228/903 Metal to nonmetal

Abstract

A solder composition that bonds well to oxides and other surfaces to which solder bonding is conventionally difficult is provided. The solder is particularly useful for reliable bonding and packaging of optical components that often have oxide surfaces. The solder composition exhibits a microstructure containing a solder matrix in which is distributed fine, micron-scale islands of rare-earth-containing intermetallic particles. The existence of the islands makes the rare earth elements better available for bonding, and reduce the extent to which the rare earths are oxidized. Advantageously, the solder contains Au and/or Ag, in which the rare earth elements tend to have some solid solubility. Due to this solubility, the Au and/or Ag tend to provide some additional protection of the rare earths against oxidation, and thereby also provide accelerated dissolution of the rare earth into the molten solder.

Claims

1. An article comprising a solder composition that comprises:

one or more elements selected from the group consisting of Sn, Sb, In, Bi, Zn, and Pb; and

0.01 to 20 wt. % of one or more rare earth elements,

wherein the microstructure of the solder composition consists essentially of a matrix and islands of one or more intermetallic compounds in the matrix, wherein the one or more intermetallic compounds comprise at least a portion of the one or more rare earth elements, wherein the average effective diameter of the islands is less than 60 μ

m, and wherein the matrix comprises a base solder material comprising at least a portion of the one or more elements.

2. The article of claim 1, wherein the average effective diameter of the islands is less than 20 μ

m.

3. The article of claim 1, wherein the solder composition further comprises at least 0.1 wt. % Au, Ag, or mixtures thereof, based on the weight of the total composition.

4. The article of claim 3, wherein the amount of Au, Ag, or mixtures thereof is sufficient to reduce the rate of oxidation of rare earth in the solder by at least 20% compared to a substantially identical solder composition without the Au, Ag, or mixtures thereof, and wherein the Au, Ag, or mixtures thereof provide solid solubility for at least a portion of the one or more rare earth elements.

5. The article of claim 3, wherein the solder composition comprises greater than 50 wt. % Au, Ag, or mixtures thereof.

6. The article of claim 5, wherein the solder composition comprises 0.1 to 5 wt. % of the one or more rare earth elements.

7. The article of claim 6, wherein the solder composition comprises 0.2 to 2 wt. % of the one or more rare earth elements.

8. The article of claim 3, wherein the solder composition comprises 0.1 to 30 wt. % Au, Ag, or mixtures thereof.

9. The article of claim 8, wherein the solder composition comprises 0.2 to 5 wt. % Au, Ag or mixtures thereof.

10. The article of claim 3, wherein the solder composition consists essentially of Au, Sn, and the one or more rare earth elements, or Ag, Sn and the one or more rare earth elements.

11. The article of claim 1, wherein the one or more rare earth elements are selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

12. A process for fabricating an article, comprising the step of bonding surfaces of two or more components with a solder composition that comprises:

one or more elements selected from the group consisting of Sn, Sb, In, Bi, Zn, and Pb; and

0.1 to 20 wt. % of one or more rare earth elements,

wherein the microstructure of the solder composition consists essentially of a matrix and islands of one or more intermetallic compounds in the matrix, wherein the one or more intermetallic compounds comprise at least a portion of the one or more rare earth elements, wherein the average effective diameter of the islands is less than 60 μ

m, and wherein the matrix comprises a base solder material comprising at least a portion of the one or more elements.

13. The process of claim 12, wherein the average effective diameter of the islands is less than 20 μ

m.

14. The process of claim 12, wherein the solder composition further comprises at least 0.1 wt. % Au, Ag, or mixtures thereof, based on the weight of the total composition.

15. The process of claim 14, wherein the amount of Au, Ag, or mixtures thereof is sufficient to reduce the rate of oxidation of rare earth in the solder by at least 20% during bonding compared to a substantially identical solder composition without the Au, Ag, or mixtures thereof, and wherein the Au, Ag, or mixtures thereof provide solid solubility for at least a portion of the one or more rare earth elements.

16. The process of claim 15, wherein the solder composition comprises greater than 50 wt. % Au, Ag, or mixtures thereof.

17. The process of claim 16, wherein the solder composition comprises 0.1 to 5 wt. % of the one or more rare earth elements.

18. The process of claim 17, wherein the solder composition comprises 0.2 to 2 wt. % of the one or more rare earth elements.

19. The process of claim 14, wherein the solder composition comprises 0.1 to 30 wt. % Au, Ag, or mixtures thereof.

20. The process of claim 19, wherein the solder composition comprises 0.2 to 5 wt. % Au, Ag or mixtures thereof.

21. The process of claim 14, wherein the solder composition consists essentially of Au, Sn, and the one or more rare earth elements, or Ag, Sn and the one or more rare earth elements.

22. The process of claim 12, wherein the one or more rare earth elements are selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

23. The process of claim 12, wherein the solder composition exhibits a creep strain rate of less than 10% per year.

24. The process of claim 12, wherein the bonded surface of at least one of the components comprises an oxide, and wherein the bonding is performed in the absence of an intermediate metallizing layer.

25. The process of claim 12, wherein the bonded surface of at least one of the components comprises an oxide s elected from the group consisting of Al₂O₃, SiO₂, NiO, Cr₂O₃, TiO₂, NbO₂, Fe₂O₃, Ta₂O₅, ZrO₂, CuO, and ZnO, or a metal selected from the group consisting of Al, Si, Cr, Ti, Nb, Ta, Zr, and Zn.

26. The process of claim 12, wherein at least one of the components is a silica-based optical fiber, a silica-based optical fiber grating, or silica-based or phosphate glass-based planar waveguide.