Hermetically sealed micro-device package using cold-gas dynamic spray material deposition

• US 6,723,379 B2
• Filed: 04/26/2002
• Issued: 04/20/2004
• Est. Priority Date: 03/22/2002
• Status: Expired due to Fees

• Current Assignee: Astravac Glass, Inc.
• Original Assignee: David H. Stark
• Inventors: Stark, David H.
• Primary Examiner(s): Parker, Fred J.
• Application Number:
  US10/133,049
• Publication Number:
  US 20030188881A1
• Time in Patent Office: 725 Days
• Field of Search: 427/180, 427/190-192, 427/199, 427/96, 427/108, 427/110, 427/123, 427/126.6, 427/421, 427/427, 148/537
• US Class Current: 427/180
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 7/0067 for controlling the passage of optical signals through the package
• CPC Class Codes: B81C 1/00269 Bonding of solid lids or wafers to the substrate
• CPC Class Codes: B81C 1/00293 maintaining a controlled atmosphere with processes not provided for in B81C1/00285
• CPC Class Codes: H01L 21/50 Assembly of semiconductor devices using processes or apparatus not provided for in a single one of the subgroups H01L21/06 - H01L21/326, e.g. sealing of a cap to a base of a container
• CPC Class Codes: H01L 23/10 characterised by the material or arrangement of seals between parts, e.g. between cap and base of the container or between leads and walls of the container
• CPC Class Codes: H01L 27/14618 Containers
• CPC Class Codes: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H01L 27/14683 Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof not peculiar thereto H01L21/00
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/09701 Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 31/0203 Containers; Encapsulations , e.g. encapsulation of photodiodesfor photovoltaic devices H01L31/048; for organic photosensitive devices H10K30/80
• CPC Class Codes: H01L 31/02325 the optical elements not being integrated nor being directly associated with the device
• CPC Class Codes: Y02P 80/30 Reducing waste in manufacturing processes; Calculations of released waste quantities
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

A method for manufacturing a cover assembly including a transparent window portion and a metallic frame that can be joined to a micro-device package base to form a hermetically sealed micro-device package. A sheet of a transparent material is provided having a window portion defined thereupon, the window portion having finished top and bottom surfaces. A frame-attachment area is prepared on the sheet, the frame-attachment area circumscribing the window portion. A first quantity of powdered metal particles is sprayed onto the prepared frame-attachment area of the sheet using a jet of gas, the gas being at a temperature below the fusing temperature of the metal particles. The jet of gas has a velocity sufficient to cause the metal particles to merge with one another upon impact with the sheet and with one another so as to form an initial continuous metallic coating adhering to the frame-attachment area of the sheet. Successive quantities of powdered metal particles are applied over the initial continuous metallic coating using the jet of gas so as to form a continuous built-up metallic frame incorporating the initial continuous metallic coating as its base and having an overall thickness that is a predetermined thickness.

Claims

1. A method for manufacturing a cover assembly that can be joined to a micro-device package base to form a hermetically sealed micro-device package, the cover assembly including a transparent window portion and a metallic frame, the method comprising the following steps:

providing a sheet of a transparent material having a window portion defined thereupon, the window portion having finished top and bottom surfaces;

preparing a frame-attachment area on the sheet, the frame-attachment area circumscribing the window portion;

spraying a first quantity of powdered metal particles onto the prepared frame-attachment area of the sheet using a jet of gas, the gas being at a temperature below the fusing temperature of the metal particles, the jet of gas having a velocity sufficient to cause the metal particles to merge with one another upon impact with the sheet and with one another so as to form an initial continuous metallic coating adhering to the frame-attachment area of the sheet; and

applying successive quantities of powdered metal particles over the initial continuous metallic coating using the jet of gas so as to form a continuous built-up metallic frame incorporating the initial continuous metallic coating as its base and having an overall thickness that is a predetermined thickness.

2. A method in accordance with claim 1, wherein the temperature of the jet of gas is below the glass transition temperature (T_G) of the transparent material of the sheet.

3. A method in accordance with claim 1, wherein the temperature of the jet of gas is below the temperature at which any coatings and finishes previously applied to the sheet are degraded.

4. A method in accordance with claim 1, wherein the temperature of the jet of gas is less than about 380°

C.

5. A method in accordance with claim 4, wherein the temperature of the jet of gas is near room temperature.

6. A method in accordance with claim 5, wherein the cover assembly is completely manufactured at near room temperature.

7. A method in accordance with claim 1, wherein the first quantity of powdered metal particles has a composition which is a pure metal.

8. A method in accordance with claim 7, wherein the composition of the first quantity of powdered metal particles is one of aluminum, zinc, chromium, nickel, silver, gold and tin.

9. A method in accordance with claim 7, wherein at least one of the successive quantities of powdered metal particles has a composition which is a metal alloy.

10. A method in accordance with claim 9, wherein the metal alloy is Kovar alloy.

11. A method in accordance with claim 9, wherein the metal alloy has a coefficient of thermal expansion (CTE) matching the CTE of the transparent sheet.

12. A method in accordance with claim 1, wherein the first quantity of powdered metal particles has a composition which is a metal alloy.

13. A method in accordance with claim 12, wherein the metal alloy of the first quantity of powdered metal particles is one of Kovar alloy and tin-bismuth alloy.

14. A method in accordance with claim 1, wherein the composition of the first quantity of powdered metal particles and the composition of at least one of the successive quantities of powdered metal particles are different from one another such that the built-up metallic frame includes at least two discrete metallic layers having different compositions.

15. A method in accordance with claim 14, wherein the predetermined thickness of the built-up metallic frame is within the range from about 130 microns to about 13,081 microns.

16. A method in accordance with claim 15, wherein the predetermined thickness of the built-up metallic frame is within the range from about 648 microns to about 2,769 microns.

17. A method in accordance with claim 1, wherein the predetermined thickness of the overall thickness of the built-up metal frame above the frame-attachment area is within the range from about 5% to about 100% of the thickness of the transparent material beneath the frame-attachment area.

18. A method in accordance with claim 1, wherein the predetermined thickness of the built-up metallic frame is within the range from about 130 microns to about 13,081 microns.

19. A method in accordance with claim 1, wherein the resulting cover assembly is suitable for joining to the package base by welding.

20. A method in accordance with claim 1, wherein the resulting cover assembly is suitable for joining to the package base by soldering.

21. A method for manufacturing a cover assembly for a micro-device package, the method comprising the following steps:

providing a sheet of a transparent material having a window portion defined thereupon;

spraying a first quantity of powdered particles onto the sheet using a jet of gas, the gas being at a temperature below the fusing temperature of the particles, the jet of gas having a velocity sufficient to cause the particles to merge with one another upon impact with the sheet and with one another so as to form an initial continuous coating adhering to the sheet and circumscribing the window portion thereof; and

applying successive quantities of powdered particles over the initial continuous coating using the jet of gas so as to form a continuous built-up frame circumscribing the window portion and incorporating the initial continuous coating.

22. A method in accordance with claim 21, wherein the temperature of the jet of gas is below the glass transition temperature (T_G) of the transparent material of the sheet.

23. A method in accordance with claim 21, wherein the temperature of the jet of gas is below the temperature at which any coatings and finishes previously applied to the sheet are degraded.

24. A method in accordance with claim 21, wherein the powdered particles are metal.

25. A method in accordance with claim 21, wherein the powdered particles are a polymeric material.

26. A method in accordance with claim 21, wherein the overall thickness of the built-up frame above the transparent material is within the range from about 5% to about 100% of the thickness of the transparent material beneath the frame.

27. A method in accordance with claim 21, wherein the predetermined thickness of the built-up frame is within the range from about 130 microns to about 13,081 microns.

28. A method in accordance with claim 21, wherein the built-up frame has a coefficient of thermal expansion (CTE) matching the CTE of the transparent sheet.

29. A method for manufacturing a cover assembly that can be joined to a micro-device package base to form a hermetically sealed micro-device package, the cover assembly including a transparent window portion and a frame, the method comprising the following steps:

providing a sheet of a transparent material having a window portion defined thereupon;

preparing a frame-attachment area on the sheet, the frame-attachment area circumscribing the window portion;

depositing metal onto the prepared frame-attachment area of the sheet using cold-gas dynamic spray deposition until a built-up metal frame is formed upon the sheet having a predetermined thickness above the frame-attachment area.

30. A method in accordance with claim 29, wherein the step of preparing a frame-attachment area on the sheet further comprises roughening the surface of the sheet along a path circumscribing the window portion.

31. A method in accordance with claim 29, wherein the predetermined thickness of the built-up metal frame above the frame-attachment area is within the range from about 5% to about 100% of the thickness of the sheet beneath the frame-attachment area.

32. A method in accordance with claim 29, wherein the step of depositing metal further comprises depositing a layer of Kovar alloy onto the sheet using cold-gas dynamic spray deposition until the layer has a thickness of within the range from about 127 microns to about 12,700 microns.

33. A method in accordance with claim 32, wherein the step of depositing metal further comprises depositing a first layer of aluminum onto the prepared frame-attachment area of the sheet before the Kovar alloy layer using cold-gas dynamic spray deposition until the first layer has a thickness within the range from about 2.54 microns to about 127 microns.

34. A method in accordance with claim 33, wherein the step of depositing metal further comprises depositing an intermediate layer of nickel after the aluminum layer and before the Kovar alloy layer using cold-gas dynamic spray deposition until the second layer has a thickness within the range from about 2.54 microns to about 127 microns.

35. A method in accordance with claim 34, wherein the step of depositing metal further comprises depositing an intermediate layer of copper after the aluminum layer and before the nickel layer using cold-gas dynamic spray deposition until the second layer has a thickness of within the range from about 2.54 microns to about 127 microns.

36. A method in accordance with claim 32, wherein the step of depositing metal further comprises depositing a first layer of zinc onto the prepared frame-attachment area of the sheet using cold-gas dynamic spray deposition until the first layer has a thickness within the range from about 2.54 microns to about 127 microns.

37. A method in accordance with claim 36, wherein the step of depositing metal further comprises depositing an intermediate layer of nickel after the zinc layer and before the Kovar alloy layer using cold-gas dynamic spray deposition until the nickel layer has a thickness within the range from about 2.54 microns to about 127.

38. A method in accordance with claim 32, wherein the step of depositing metal further comprises depositing a first layer of chromium onto the prepared frame-attachment area of the sheet using cold-gas dynamic spray deposition until the first layer has a thickness within the range from about 2.54 microns to about 127 microns.

39. A method in accordance with claim 38, wherein the step of depositing metal further comprises depositing an intermediate layer of nickel after the chromium layer and before the Kovar alloy layer using cold-gas dynamic spray deposition until the second layer has a thickness within the range from about 2.54 microns to about 127 microns.

40. A method in accordance with claim 29, further comprising the step of depositing additional metallic layers onto the built-up frame using solution bath plating.

41. A method in accordance with claim 40, further comprising the step of flattening the top surface of the built-up frame to a predetermined flatness after the cold-gas dynamic spray metal deposition and before depositing additional metallic layers using solution bath plating.

42. A method in accordance with claim 40, wherein the step of flattening the top surface of the built-up frame is performed using one of grinding, lapping, pressing and laser ablation procedures.

43. A method in accordance with claim 40, wherein the step of depositing additional metallic layers using solution bath plating includes:

plating a layer of nickel over the cold-gas dynamic spray deposited metal of the frame until the nickel layer has a thickness within the range from about 0.002 microns to about 25 microns; and

plating a layer of gold over the nickel layer until the gold layer has a thickness within the range from about 0.0508 microns to about 0.508 microns.

44. A method in accordance with claim 29, further comprising the step of annealing the built-up frame by heating after its deposition onto the sheet.

45. A method in accordance with claim 44, wherein the step of annealing includes annealing the totality of the sprayed-on metals and alloys.

46. A method in accordance with claim 44, wherein the step of annealing includes annealing only the outermost portions of the integral built-up frame.