Compliant and hermetic solder seal

• US 20030198428A1
• Filed: 04/17/2002
• Published: 10/23/2003
• Est. Priority Date: 04/17/2002
• Status: Active Grant

• Current Assignee: Avago Technologies Fiber IP Singapore PTE Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies Fiber IP Singapore PTE Limited (Broadcom, Inc.)
• Inventors: Humpston, Giles, Miller, Daniel J., Trott, Gary R., Ichimura, Yoshikatsu, Nystrom, Michael J., Mar, Nancy M., Reynolds, Heidi L.
• Granted Patent: US 6,958,446 B2
• Time in Patent Office: Days
• US Class Current: 385/16
• CPC Class Codes: B23K 1/0016 Brazing of electronic components
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: B23K 2103/18 Dissimilar materials
• CPC Class Codes: B23K 2103/52 Ceramics
• CPC Class Codes: B23K 2103/54 Glass
• CPC Class Codes: B23K 2103/56 semiconducting semiconducting devices B23K2101/40
• CPC Class Codes: B23K 35/26 with the principal constituent melting at less than 400 degrees C
• CPC Class Codes: G02B 2006/12104 Mirror; Reflectors or the like
• CPC Class Codes: G02B 6/12 of the integrated circuit kind electric integrated circuits H01L27/00
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: G02B 6/3582 Housing means or package or arranging details of the switching elements, e.g. for thermal isolation
• CPC Class Codes: G02B 6/36 Mechanical coupling means G02B6/255, G02B6/42 take precedence
• CPC Class Codes: G02B 6/4248 Feed-through connections for the hermetical passage of fibres through a package wall see provisionally also G02B6/4428

Abstract

A solder joint or seal attaching components having dissimilar coefficients of thermal expansion is made thin (e.g., less than 20 μm and preferably about 5 μm) and of a solder such as an indium-based solder that has a tendency to creep. The solder is toroidal or otherwise shaped to avoid tensile stress in the solder. Axial shearing stress in the solder causes reversible creep without causing failure of the joint or seal. In one embodiment, a toroidal solder seal has a diameter, a footprint, and a thickness in approximate proportions of 5000:200:1.

Claims

1. A solder joint comprising:

first and second components having different coefficients of thermal expansion; and

solder between and attached to the first and second components, wherein the solder has a toroidal shape and surrounds a cavity formed between the first and second component.

2. The solder joint of claim 1, wherein the solder is an in indium-based alloy.

3. The solder joint of claim 2, wherein the indium based alloy is 48% tin by weight.

4. The solder joint of claim 1, wherein the solder has a stress rupture life of less than about 1,000 minutes at an applied stress of 5 MN·

m<sup>−

2</sup> at an operating temperature of the solder joint.

5. The solder joint of claim 1, wherein the solder has a thickness less than 20 μ

m.

6. The solder joint of claim 1, wherein the solder has a thickness no greater than 5 μ

m.

7. The solder joint of claim 1, wherein the toroidal shape is such that thermal expansion of the first and second components fails to cause significant tensile or tangential stress in the solder.

8. The solder joint of claim 7, wherein the toroidal shape has a diameter, a footprint, and a thickness that are in proportions 5000:

200;

1.

9. The solder joint of claim 8, wherein the toroidal shape is 18 mm in diameter.

10. The solder joint of claim 9, wherein the toroidal shape has a footprint of 0.8 mm.

11. The solder joint of claim 1, wherein the first component comprises a silicon substrate having a metalized region to which the solder attaches.

12. The solder joint of claim 11, wherein the second component comprises a quartz plate having a metalized region to which the solder attaches.

13. The solder joint of claim 1, wherein the second component comprises a glass or ceramic material having a metalized region to which the solder attaches.

14. A solder joint comprising:

first and second components having dissimilar coefficients of thermal expansion; and

solder between and attached to the first and second components, wherein the solder has a thickness less than 20 μ

m and has a tendency to creep in response to shearing stress cause by thermal expansion of the first and second components.

15. The solder joint of claim 14, wherein the solder has a thickness no greater than 5 μ

m.

16. The solder joint of claim 14, wherein the solder has a stress rupture life of less than about 1,000 minutes at an applied stress of 5 MN·

m<sup>−

2</sup> at an operating temperature of the solder joint.

17. An optical switch comprising:

an optical plate;

an integrated circuit; and

a solder seal attaching the optical plate to the integrated circuit and hermetically enclosing a cavity that is between the optical plate and the integrated circuit, wherein the solder seal is in the shape of a torus having a diameter that is much larger than a footprint of the torus, the footprint being much larger than a thickness of the torus.

18. The optical switch of claim 17, wherein the thickness of the torus is less than about 20 μ

m.

19. The optical switch of claim 17, wherein the footprint is more than 10 times the thickness, and the diameters is more than 25 times the footprint.

20. The optical switch of claim 17, wherein the solder is an indium-based solder.