SYSTEMS AND METHODS FOR AIR-RELEASE IN CAVITY PACKAGES

• US 20130093031A1
• Filed: 10/04/2012
• Published: 04/18/2013
• Est. Priority Date: 10/07/2011
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Gao, Jia, Yang, Jicheng, Xue, Xiaojie, Saiyed, Shafi, Ng, Siu Lung
• Granted Patent: US 8,853,839 B2
• Time in Patent Office: Days
• US Class Current: 257/417
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81C 1/00269 Bonding of solid lids or wafers to the substrate
• CPC Class Codes: B81C 2203/0109 Bonding an individual cap on the substrate
• CPC Class Codes: B81C 2203/032 Gluing
• CPC Class Codes: B81C 2203/035 Soldering
• CPC Class Codes: H01L 23/047 the other leads being parallel to the base
• CPC Class Codes: H01L 23/49861 Lead-frames fixed on or encapsulated in insulating substrates H01L23/4985, H01L23/49805 take precedence
• CPC Class Codes: H01L 29/66007 Multistep manufacturing processes
• CPC Class Codes: H01L 29/84 controllable by variation of applied mechanical force, e.g. of pressure
• 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 2924/19107 off-chip wires

Abstract

A housing for integrated devices that includes an air-release mechanism is disclosed. This is achieved, in various embodiments, by forming a vent hole in a package substrate, and arranging a package lid over the package substrate. The vent hole allows air to be released from within the cavity package, thereby ensuring that the package lid remains stably affixed to the package substrate despite increased temperatures during processing. The vent hole may be sealed upon mounting the package onto a mounting substrate.

Claims

1. A device package comprising:

a package housing defining a cavity;

a motion sensor die mounted within the housing; and

a hole extending through the housing.

2. The device package of claim 1, wherein the housing has a bottom surface comprising at least one lead, the hole extending through the bottom surface.

3. The device package of claim 2, wherein the housing comprises a package substrate and a lid attached to the package substrate, the hole extending through the package substrate.

4. The device package of claim 3, wherein the hole is sized to release air from the cavity when the lid is attached to the package substrate.

5. The device package of claim 3, wherein the lid is attached to the package substrate using an epoxy.

6. The device package of claim 3, wherein the motion sensor die comprises a microelectromechanical systems (MEMS) accelerometer.

7. The device package of claim 3, wherein the motion sensor die comprises a microelectromechanical systems (MEMS) gyroscope.

8. The device package of claim 3, wherein the hole is laterally spaced from the motion sensor die.

9. The device package of claim 3, wherein the package substrate is mounted on and electrically connected to an external board, the hole being sealed to prevent communication therethrough.

10. The device package of claim 9, wherein the hole is sealed by solder or epoxy.

11. The device package of claim 3, wherein the lid comprises a conductive material, and wherein the lid is attached to the package substrate by an epoxy material.

12. The device package of claim 11, wherein the epoxy material is electrically conductive.

13. The device package of claim 3, wherein the package substrate comprises a plastic material.

14. The device package of claim 3, wherein the package substrate comprises a printed circuit board (PCB).

15. The device package of claim 14, comprising an annular metal trace on the bottom surface of the housing, and wherein the annular metal trace surrounds the hole.

16. The device package of claim 15, wherein the annular metal trace is not electrically connected to any circuit.

17. The device package of claim 3, wherein the package substrate comprises a molded leadframe.

18. The device package of claim 17, wherein the device package is a leadframe chip scale package (LFCSP) or a small-outline integrated circuit (SOIC) package.

19. The device package of claim 17, wherein the hole is formed through a metallic portion of the leadframe.

20. The device package of claim 19, wherein the hole is formed through a dummy lead.

21. The device package of claim 17, wherein the hole comprises an upper portion adjacent to an upper surface of the package substrate, and a lower portion adjacent to a bottom surface of the package substrate, wherein the cross-sectional area of the hole is larger in the lower portion than in the upper portion.

22. The device package of claim 3, wherein the lid is shaped to form a concavity.

23. The device package of claim 3, wherein the package substrate includes a base and a wall extending from the base, and wherein the lid is substantially planar.

24. A device package comprising:

a package substrate having an upper surface and a bottom surface, the package substrate comprising;

a leadframe; and

a molding material surrounding portions of the leadframe;

wherein a hole extends through the leadframe from the upper surface of the package substrate to the bottom surface of the package substrate.

25. The device package of claim 24, further comprising a lid attached to the upper surface of the package substrate, wherein the lid substantially encloses a portion of the package substrate and forms an air cavity within the device package.

26. The device package of claim 25, wherein the hole is configured to release air from the air cavity when the lid is attached to the upper surface of the package substrate.

27. The device package of claim 25, further comprising a microelectromechanical system (MEMS) motion sensor die attached to the upper surface of the package substrate.

28. The device package of claim 27, wherein the hole is laterally and electrically separated from the MEMS motion sensor die.

29. The device package of claim 24, wherein the hole comprises an upper portion adjacent to the upper surface of the package substrate, and a lower portion adjacent to the bottom surface of the package substrate, wherein the cross-sectional area of the hole is larger in the lower portion than in the upper portion.

30. The device package of claim 29, wherein the hole is configured to receive a sealant within the lower portion.

31. The device package of claim 30, wherein the sealant is solder.

32. The device package of claim 30, wherein the hole is further configured such that the sealant is restricted from passing through the upper portion of the hole.

33. The device package of claim 24, wherein the hole is a round hole having a diameter in a range of about 25 μ

m to about 1 mm.

34. The device package of claim 33, wherein the hole is a round hole having a diameter in a range of about 100 μ

m to about 600 μ

m.

35. A device package comprising:

a package substrate having an upper surface and a bottom surface;

a hole extending from the upper surface of the package substrate to the bottom surface of the package substrate, wherein a portion of the hole intersects the bottom surface and defines a perimeter on the bottom surface of the package substrate; and

an annular metal trace positioned substantially around the perimeter of the hole.

36. The device package of claim 35, wherein the annular metal trace is electrically isolated.

37. The device package of claim 35, further comprising a lid attached to the upper surface of the package substrate, wherein the lid substantially encloses a portion of the package substrate and forms an air cavity within the device package.

38. The device package of claim 37, wherein the lid is sealed to the package substrate with epoxy.

39. The device package of claim 37, wherein the hole is sized to release air from the air cavity when the lid is attached to the upper surface of the package substrate.

40. The device package of claim 39, wherein the package substrate comprises a printed circuit board (PCB)

41. The device package of claim 37, further comprising a microelectromechanical system (MEMS) motion sensor die attached to the upper surface of the package substrate.

42. The device package of claim 41, wherein the annular metal trace is laterally and electrically isolated from the MEMS motion sensor die.

43. A method of integrating a motion sensor with an outside electronic circuit, the method comprising:

providing a package substrate with a vent hole therethrough;

mounting a motion sensor die on the package substrate; and

attaching a lid to the package substrate to form a housing enclosing the motion sensor die but for the vent hole.

44. The method of claim 43, wherein attaching the lid comprises applying epoxy and curing the epoxy at greater than about 150°

C.

45. The method of claim 44, wherein the epoxy is electrically conductive.

46. The method of claim 43, further comprising mounting the package substrate to an external board after attaching the lid.

47. The method of claim 46, wherein mounting the package substrate comprises simultaneously sealing the vent hole.

48. The method of claim 47, wherein the package substrate comprises a molded leadframe, the vent hole is formed in a metal feature of the molded leadframe, and sealing comprises applying solder to the vent hole.

49. The method of claim 47, wherein the package substrate comprises a printed circuit board (PCB) including an annular metal trace surrounding the vent hole, and sealing comprises applying solder to the metal trace.

50. A method of mounting a packaged motion sensor device to an external board comprising:

providing a package housing comprising a cavity, a motion sensor die mounted within the housing, and a vent hole extending through the housing; and

simultaneously mounting the package housing to an external board and sealing the vent hole.

51. The method of claim 50, wherein the housing has a bottom surface comprising at least one lead, the hole extending through the bottom surface.

52. The method of claim 51, wherein the housing comprises a package substrate defining the bottom surface and a lid attached to the package substrate, the vent hole extending through the package substrate.

53. The method of claim 52, wherein the package substrate further comprises an annular metal trace on the bottom surface of the housing, and wherein the annular metal trace surrounds the hole.

54. The method of claim 53, wherein sealing the vent hole comprises coupling the annular metal trace to an annular sealing structure of the external board.