Package, in particular for MEMS devices and method of making same

• US 20080164543A1
• Filed: 01/04/2008
• Published: 07/10/2008
• Est. Priority Date: 01/04/2007
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Shaw, Mark, Fontana, Fulvio Vittorio, Ziglioli, Federico Giovanni
• Granted Patent: US 7,898,043 B2
• Time in Patent Office: Days
• US Class Current: 257/415
• CPC Class Codes: B81B 7/0061 suitable for fluid transfer from the MEMS out of the package or vice versa, e.g. transfer of liquid, gas, sound
• CPC Class Codes: B81B 7/007 Interconnections between the MEMS and external electrical signals
• CPC Class Codes: H01L 2224/0554 External layer
• CPC Class Codes: H01L 2224/0555 Shape
• CPC Class Codes: H01L 2224/0556 Disposition
• CPC Class Codes: H01L 2224/0557 the external layer being disposed on a via connection of the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/05571 the external layer being disposed in a recess of the surface
• CPC Class Codes: H01L 2224/05573 Single external layer
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/056 with a principal constituent of the material being a metal or a metalloid, e.g. boron [B], silicon [Si], germanium [Ge], arsenic [As], antimony [Sb], tellurium [Te] and polonium [Po], and alloys thereof
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/1461 MEMS

Abstract

A package includes a substrate provided with a passing opening and a MEMS device. The MEMS device includes an active surface wherein a portion of the MEMS device is integrated sensitive to the chemical/physical variations of a fluid. The active surface of the MEMS device faces the substrate and is spaced therefrom, the sensitive portion being aligned to the passing opening. A protective package incorporates the MEMS device and the substrate, leaving at least the sensitive portion of the MEMS device exposed through the passing opening of the substrate.

Claims

1. A package, comprising:

a substrate provided with a passing opening,

a MEMS device comprising an active surface wherein a sensitive portion of said MEMS device is integrated sensitive to chemical/physical variations of a fluid;

wherein said active surface of said MEMS device faces said substrate and is spaced therefrom, said sensitive portion being aligned to said passing opening; and

a protective package, which incorporates said MEMS device and said substrate, leaving at least said sensitive portion of said MEMS device exposed through said passing opening of said substrate.

2. The package according to claim 1, wherein electric connections which electrically couple said MEMS device to said substrate are present outside said sensitive portion.

3. The package according to claim 2, wherein an underfiller incorporates said electric connections.

4. The package according to claim 2, wherein said electric connections comprise bumps.

5. The package according to claim 2, wherein an underfiller completely surrounds at least said sensitive portion of said MEMS device.

6. The package according to claim 2, wherein said underfiller shows a tapered profile.

7. The package according to claim 4, wherein a peripheral portion of said active surface of said MEMS device is provided with connection pads, wherein an upper surface of said substrate facing said active surface of said MEMS device is provided with conductive lands, and wherein bumps are electrically connected between said conductive lands and said connection pads.

8. The package according to claim 1, wherein said substrate is of the conventional LGA type.

9. The package according to claim 1, wherein said substrate is of the conventional BGA type.

10. The package according to claim 1, wherein said substrate comprises an insulating core including conductive vias that project with respect to said insulating core in correspondence with an upper surface of said substrate facing said active surface of said MEMS device, said upper surface being free from welding masking layers, the electric connection between said MEMS device and said conductive vias being obtained through interposition of a layer of connection material.

11. The package according to claim 1, wherein an upper surface of said substrate facing said active surface of said MEMS device is provided with conductive lands, and wherein the electric connection between said MEMS device and said conductive lands is obtained through interposition of a layer of connection material.

12. The package according to claim 11, wherein said layer of connection material is of a material chosen among:

ACP (Anisotropic Conductive Paste), NCP (Not Conductive Paste), ACF (Anisotropic Conductive Tape), NCT (Not Conductive Tape).

13. The package according to claim 11, wherein said layer of connection material completely surrounds at least said sensitive portion of said MEMS device.

14. The package according to claim 1, wherein said MEMS device is mounted onto said substrate through the known “

flip-chip”

assembling method.

15. The package according to claim 1, wherein said MEMS device is completely enclosed in said protective package.

16. The package according to claim 1, further comprising integrated circuits mounted flanked or piled onto the MEMS device.

17. The package according to claim 1, wherein said integrated circuits are electrically connected to the substrate, through further electric connections.

18. The package according to claim 17, wherein said protective package incorporates said integrated circuits and said further electric connections.

19. The package according to claim 1, wherein said MEMS device is a pressure, flow, gas, pH, or in general chemical sensor.

20. The package according to claim 1, wherein said protective package is realized through molding.

21. The package according to claim 11, wherein said substrate is of the LGA type.

22. A package, comprising:

a substrate comprising an insulating core,

an integrated circuit comprising an active surface;

wherein said active surface of said integrated circuit faces said substrate and is spaced therefrom;

a protective package, which incorporates said integrated circuit and said substrate; and

conductive vias projecting with respect to said insulating core in correspondence with an upper surface of said substrate facing said active surface of said integrated circuit, said upper surface being free from masking layers at least in correspondence with said active surface, the electric connection between said integrated circuit and said conductive vias being obtained through interposition of a layer of connection material.

23. The package according to claim 22, wherein said layer of connection material is of a material chosen among:

ACP (Anisotropic Conductive Paste), NCP (Not Conductive Paste), ACF (Anisotropic Conductive Tape), NCT (Not Conductive Tape).

24. The package according to claim 22, wherein said integrated circuit is mounted onto said substrate through the known “

flip-chip”

assembling method.

25. The package according to claim 22, wherein said integrated circuit is completely enclosed in said protective package.

26. A method for protecting packages comprising a substrate provided with a passing opening, and at least one MEMS device comprising an active surface wherein a portion of said MEMS device is integrated sensitive to chemical/physical variations of a fluid, the method comprising the following steps:

forming on said sensitive portion a protection layer which fills at least partially said passing opening,

forming a protective package, which incorporates said MEMS device and said substrate, leaving said protection layer exposed,

removing said protection layer so that said protective package leaves at least said sensitive portion of said MEMS device exposed, through said passing opening of said substrate.

27. The method according to claim 26, wherein said protection layer is formed of a paste washable in water.

28. The method according to claim 26, wherein said protection layer is a viscous paste, with a viscosity comprised between 15.000 and 17.000 cps.

29. The method according to claim 26, wherein said protection layer is formed at least on said sensitive portion of the MEMS device before it is connected to said substrate.

30. The method according to claim 26, wherein said protection layer is formed at least on said sensitive portion of said MEMS device by stencil printing.

31. The method according to claim 26, wherein said protection layer is formed at least on said sensitive portion of the MEMS device after it has been connected to a substrate.

32. The method according to claim 30, wherein said protection layer is formed on a lower surface of the substrate, then with a spatula it is distributed inside said passing opening.

33. The method according to claim 27, wherein said protection layer is removed through a washing step first in cold water and then in hot water.

34. The method according to claim 33, wherein said washing step is carried out with spray jets of cold water at a pressure of about 4 atmospheres and then with spray jets of hot water at about 50°

C. at a pressure of about 4 atmospheres.

35. The method according to claim 27, wherein said protection layer is removed through a washing step in cold water with the help of ultrasounds.

36. An electronic device, comprising:

a substrate including a passing opening;

a die coupled to the substrate, the die including an active surface and the active surface including a sensitive portion positioned adjacent the passing opening of the substrate and the die being operable to sense a physical parameter of a medium to which the sensitive portion is exposed through the passing opening; and

a protective package housing the substrate and the die.

37. The electronic device of claim 36 wherein the die comprises a MEMS device.

38. The electronic device of claim 36 wherein the medium comprises a fluid.

39. The electronic device of claim 38 wherein the physical parameter of the fluid comprises a chemical property of the fluid.

40. The electronic device of claim 36 wherein the sensitive portion of the die is positioned towards a center of the die and wherein the protective package is formed around a periphery of the die, and wherein the coupling of the die to the substrate includes an underfiller that isolates the sensitive portion of the die from the protective package.

41. The electronic device of claim 36 further comprising a second die coupled to the substrate.

42. An electronic system, comprising:

electronic circuitry including a sensor, the sensor including,

a substrate including a passing opening;

a die coupled to the substrate, the die including an active surface and the active surface including a sensitive portion positioned adjacent the passing opening of the substrate and the die being operable to sense a physical parameter of a medium to which the sensitive portion is exposed through the passing opening; and

a protective package housing the substrate and the die.

43. The electronic system of claim 42 wherein the sensor comprises one of a pressure, flow, gas, or pH sensor.

44. The electronic system of claim 43 wherein the electronic circuitry comprises one of control circuitry, test equipment circuitry, or safety system circuitry.

45. A method of protecting packages including a substrate and a die, the die including an active surface including a sensitive portion and the method comprising:

forming a passing opening in the substrate;

forming a protection layer over the sensitive portion of the die;

attaching the die to the substrate;

forming a protective package to house the substrate and the die, the protective package leaving the passing opening exposed; and

removing the protection layer through the passing opening.

46. The method of claim 45,

wherein the protection layer forms a projection extending from the active surface of the die;

wherein attaching the die to the substrate includes inserting the projection into the passing opening.

47. The method of claim 45 wherein attaching the die to the substrate is done before forming the protection layer.

48. The method of claim 45 wherein the protection layer comprises a water soluble paste.