MEMS direct chip attach packaging methodologies and apparatuses for harsh environments

• US 6,845,664 B1
• Filed: 10/03/2002
• Issued: 01/25/2005
• Est. Priority Date: 10/03/2002
• Status: Expired due to Term

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: United States Administrator of National Aeronautics and Space Administration
• Inventors: Okojie, Robert S.
• Primary Examiner(s): Pert, Evan
• Assistant Examiner(s): GEYER, SCOTT B
• Application Number:
  US10/263,980
• Time in Patent Office: 845 Days
• Field of Search: 257/678, 257/701, 257/787, 257/414, 257/433, 438/48, 438/51, 438/55, 438/64, 438/66, 438/67, 438/106, 438/107, 438/110, 438/112, 438/117, 438/118, 438/119, 438/121, 438/124, 438/127, 734/31, 361/600, 361/820
• US Class Current: 73/431
• CPC Class Codes: B81B 2201/0264 Pressure sensors
• CPC Class Codes: B81B 2207/095 through the lid
• 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: B81C 1/00301 Connecting electric signal lines from the MEMS device with external electrical signal lines, e.g. through vias
• CPC Class Codes: G01D 11/245 Housings for sensors

Abstract

Methods of bulk manufacturing high temperature sensor sub-assembly packages are disclosed and claimed. Sensors are sandwiched between a top cover and a bottom cover so as to enable the peripheries of the top covers, sensors and bottom covers to be sealed and bound securely together are disclosed and claimed. Sensors are placed on the bottom covers leaving the periphery of the bottom cover exposed. Likewise, top covers are placed on the sensors leaving the periphery of the sensor exposed. Individual sensor sub-assemblies are inserted into final packaging elements which are also disclosed and claimed. Methods of directly attaching wires or pins to contact pads on the sensors are disclosed and claimed. Sensors, such as pressure sensors and accelerometers, and headers made out of silicon carbide and aluminum nitride are disclosed and claimed. Reference cavities are formed in some embodiments disclosed and claimed herein where top covers are not employed.

Claims

1. A method of bulk packaging sensors, comprising the steps of:

placing a bottom substrate having an array of sensor housings in a holding device to receive sensors, each of said sensor housings having an aperture therein;

inserting a sensor having contact pads in each housing of said bottom substrate;

and, placing a top substrate having an array of covers onto each respective sensor.

2. A method of bulk packaging sensors as claimed in claim 1 wherein said array of covers include joining portions and wherein each of said joining portions include undercut portions, further comprising the steps of:

sealing the perimeter of each said housing, sensor, and cover.

3. A method of bulk packaging sensors as claimed in claim 2 wherein said step of sealing forms a hermetic seal.

4. A method of bulk packaging sensors as claimed in claim 3 wherein said step of sealing is a glass seal and wherein said glass occupies said undercut portions of said joining portions.

5. A method of bulk packaging sensors as claimed in claim 2 further comprising the steps of:

cutting said sensors into individual packages.

6. A method of bulk packaging sensors as claimed in claim 3 further comprising the steps of:

cutting said sensors into individual packages.

7. A method of bulk packaging sensors as claimed in claim 4 further comprising the steps of:

cutting said sensors into individual packages.

8. A method of bulk packaging sensors as claimed in claim 1 wherein said housings are substantially square shaped and include a substantially square perimeter wall, said wall having an inside portion and an outside portion;

each sensor includes a substantially square perimeter and said perimeter of each sensor being shorter in length than said square perimeter wall of each said housing; and

, each top cover having a substantially square perimeter shorter than said square of each respective sensor.

9. A method of bulk packaging sensors as claimed in claim 8 wherein each of said top covers is stacked upon a respective sensor and each said sensor is inserted in a respective housing of said bottom substrate.

10. A plurality of packaged sensors comprising:

a bottom substrate having a plurality of housings;

each of said housings has a perimeter;

a plurality of sensors each of which resides in a respective housing;

each of said sensors has a perimeter;

a top substrate having a plurality of covers;

each of said covers has a perimeter; and

,

said sensors being sandwiched together between said housings and said covers with the perimeters of each sensor, housing and cover sealed by glass.

11. A plurality of packaged sensors as claimed in claim 10 wherein each housing includes a recess and each sensor has a corresponding shape such that each sensor fits within said recess of each respective housing;

and, wherein, each cover has a shape which corresponds to the shape of said sensor such that when said cover is placed atop said sensor the perimeter of said sensor is not covered.

12. A plurality of packaged sensors as claimed in claim 10 wherein said housings, sensors, and top covers are made from the group selected of silicon carbide and aluminum nitride.

13. A plurality of packaged sensors as claimed in claim 10 wherein said housings are arrayed in a first array and affixed to said first array by a plurality of first joining portions, said first joining portions separating said housings such that each said housing is spaced apart from the adjacent housing creating first gaps therebetween, and said top covers are arrayed in a second array and are affixed to said second array by a plurality of second joining portions, said second joining portions separating said covers such that each said cover is spaced apart from the adjacent cover creating second gaps therebetween, said second joining portions each include undercut sections, and, said second gaps being larger than said first gaps, said gaps and said undercut sections of said second joining portions enabling complete glassing of said top covers, said sensors and said housings.

14. A plurality of packaged sensors comprising:

a plurality of housings defined by walls;

a plurality of sensors each having perimeters which fit within said walls of said housings;

a plurality of top covers residing on top of said plurality of sensors such that each of said top covers resides on top of a respective sensor, each of said top covers having a shorter perimeter than its respective sensor, each said top cover has the same shape but is proportionally smaller than its respective sensor such that when said covers are mounted on top said each respective sensors said perimeters of said sensors are not covered.

15. A plurality of packaged sensors as claimed in claim 14 in combination with glass securing said top covers, sensors and housings together.

16. A plurality of packaged sensors as claimed in claim 15 wherein each of said sensors includes a plurality of contact pads and each of said top covers includes a plurality of bores therethrough in combination with a plurality of pins which extend through said bores of said top covers and engage said plurality of contact pads.

17. A plurality of packaged sensors as claimed in claim 16 in combination with conductive paste residing in said bores in said top covers for securing said pins to said top covers and said contact pads.

18. A plurality of packaged sensors as claimed in claim 17 in combination with glass securing said pins to said top covers.

19. A plurality of packaged sensors as claimed in claim 18 wherein said pins are selected from the group of platinum, gold, nickel, or alloys of refractory metals.

20. A plurality of packaged sensors as claimed in claim 18 wherein said top covers include a recess for over-pressure protection.

21. A plurality of packaged sensors as claimed in claim 18 wherein said sensors include diaphragms.

22. A plurality of packaged sensors as claimed in claim 18 wherein said sensors are accelerometers.

23. A plurality of packaged sensors as claimed in claim 18 wherein said sensors are a combination of pressure sensors and accelerometers.

24. A method of direct contact attachment of a pin to a contact pad on a sensor, said sensor covered with a top cover having a through hole aligned with said contact pad, said top cover having a periphery, said sensor having a periphery, and, glass binding and sealing said periphery of said top cover and said periphery of said sensor together, comprising the steps of:

dipping one end of the pin into a high temperature conductive paste that cures at a temperature less than the softening point of said glass used for sealing;

inserting said pin coated with conductive paste until it engages said contact pad;

firing said assembly to a temperature to cure said conductive paste;

cooling said assembly;

applying glass to said pin and said top cover to secure said pin to said cover; and

,

firing said assembly to the glass curing temperature.

25. A method of direct contact attachment as claimed in claim 24 comprising the additional steps of:

filling said through hole partially with nickel before dipping said pin in said conductive paste and inserting said pin in said through hole such that said pin engages said nickel.

26. A method of direct contact attachment as claimed in claim 24 wherein a plurality of pins are attached to a plurality of contact pads.

27. A method of direct contact attachment as claimed in claim 26 comprising the additional steps of:

filling said through holes partially with nickel before dipping said pins in said conductive paste and inserting said pins in said through hole and engaging said contact pads.

28. A glass-sealed sensor manufactured by the process of claim 27.

29. A glass-sealed sensor manufactured by the process of claim 26.

30. A packaged sensor sub-assembly comprising:

a bottom housing;

said sensor having contact pads and a perimeter, said sensor residing in said bottom housing;

a top cover having through holes therethrough, said through holes being aligned with said contact pads of said sensor;

pins;

conductive paste;

said pins residing in said through holes and engaging said contact pads of said sensors;

said conductive paste securing said pins to said through holes;

glass securing said top cover, sensor, and bottom housing together; and

,

glass securing said pins to said top cover.

31. A packaged sensor sub-assembly as claimed in claim 30 wherein said through holes of said top cover are partially filled with nickel such that said nickel engages said contact pads of said sensor and said nickel engages said pins.

32. A packaged sensor sub-assembly as claimed in claim 31 wherein said pins are selected from the group of gold, platinum or nickel.

33. A packaged sensor sub-assembly as claimed in claim 30 glassed to a Kovar header fused to a stainless steel housing.

34. A packaged sensor sub-assembly comprising:

a sensor having contact pads and a perimeter;

a top cover having through holes therethrough, said through holes being aligned with said contact pads of said sensor;

pins;

conductive paste;

said pins residing in said through holes and engaging said contact pads of said sensors;

said conductive paste securing said pins to said through holes;

glass securing said top cover and sensor together; and

,

glass securing said pins to said top cover.

35. A packaged sensor sub-assembly as claimed in claim 34 glassed to a Kovar header fused to a stainless steel housing.

36. A packaged sensor sub-assembly as claimed in claim 34 wherein said through holes of said top cover are partially filled with nickel such that said nickel engages said contact pads of said sensor and said nickel engages said pins.

37. A packaged sensor sub-assembly as claimed in claim 36 wherein said pins are selected from the group of gold, platinum or nickel.

38. A packaged sensor sub-assembly as claimed in claim 34 in combination with a sensor sub-assembly housing:

said sensor sub-assembly housing comprising a stainless steel housing having an interior and an exterior, said interior includes threads thereon, a ceramic tube resides in said interior of said stainless steel housing, brazing resides intermediate said interior threads of said stainless steel housing and said ceramic tube, and, said brazing secures said ceramic tube and said stainless steel housing together upon heating said brazing; and

,

said sensor sub-assembly being secured to said stainless steel housing and said ceramic tube by glass creating a reference cavity.

39. A packaged sensor sub-assembly housing in combination with a sensor sub-assembly housing as claimed in claim 38 further comprising metal bumps on said contact pads.

40. A sensor sub-assembly as claimed in claim 34 further comprising metal bumps on said contact pads.

41. A method for packaging a sensor sub-assembly, said sensor sub-assembly comprising a bottom housing, said sensor having contact pads and a perimeter, said sensor residing in said bottom housing, a top cover having through holes therethrough, said through holes being aligned with said contact pads of said sensor, pins, conductive paste, said pins residing in said through holes and engaging said contact pads of said sensors, said conductive paste securing said pins to said through holes, glass securing and sealing said top cover, sensor, and bottom housing together, and, glass securing said pins to said top cover, comprising the steps of:

attaching a Kovar header to a stainless steel housing;

inserting said sensor sub-assembly into said Kovar header, and,

glassing said sensor sub-assembly to said Kovar header.

42. A method for packaging a sensor as claimed in claim 41 wherein the steps of inserting said sensor sub-assembly into a Kovar header and glassing said sensor sub-assembly to said Kovar header are performed before said step of attaching said Kovar header to said stainless steel housing.

43. A method for packaging a sensor sub-assembly, said sensor sub-assembly comprising a sensor having contact pads and a perimeter, said sensor residing in said bottom housing, a top cover having through holes therethrough, said through holes being aligned with said contact pads of said sensor, pins, conductive paste, said pins residing in said through holes and engaging said contact pads of said sensors, said conductive paste securing said pins to said through holes, glass securing said top cover and sensor together, and, glass securing said pins to said top cover, comprising the steps of:

inserting said sensor sub-assembly into a stainless steel housing having threads on the interior of said housing; and

,

sealing said threads, said sensor sub-assembly and said pins within said housing.

44. A method for packaging a sub-assembly as claimed in claim 43 wherein said step of sealing said threads, said sub-assembly and said pins within said housing is a glass seal.

45. A method for packaging a sub-assembly as claimed in claim 43 wherein said glass seal length is at least 10 times the thickness of said sub-assembly.

46. A method for packaging a sub-assembly as claimed in claim 43 wherein said interior threads include at least 5 ribs.

47. A sensor sub-assembly in combination with a stainless steel housing having an interior and an exterior, said interior includes threads thereon, comprising a sensor having contact pads and a perimeter, said sensor residing in said bottom housing, a top cover having through holes therethrough, said through holes being aligned with said contact pads of said sensor, pins, conductive paste, said pins residing in said through holes and engaging said contact pads of said sensors, said conductive paste securing said pins to said through holes and to said contact pads, glass securing said top cover and sensor together, and, glass securing said pins to said top cover in combination with a stainless steel housing having an interior and an exterior, sealing glass residing in said interior of said of said stainless steel housing seals said threads, said sensor sub-assembly and said pins within said housing.

48. A sensor sub-assembly in combination with a stainless steel housing having an interior and an exterior, said interior includes threads thereon, as claimed in claim 47 wherein said glass seal length is at least 10 times the thickness of said sub-assembly.

49. A sensor sub-assembly in combination with a stainless steel housing having an interior and an exterior, said interior includes threads thereon, as claimed in claim 48 wherein said stainless steel housing further includes threads on the exterior of said housing.

50. A sensor sub-assembly housing comprising a stainless steel housing having an interior and an exterior, said interior includes threads thereon, a ceramic tube resides in said interior of said stainless steel housing, brazing resides intermediate said interior threads of said stainless steel housing and said ceramic tube, and, said brazing secures said ceramic tube and said stainless steel housing together upon heating said brazing.

51. A sensor sub-assembly housing as claimed in claim 50 wherein said ceramic tube has first and second ends and said first end is smooth.

52. A sensor sub-assembly housing as claimed in claim 50 further comprising a blow-out stopper.

53. A sensor sub-assembly housing as claimed in claim 50 further comprising a particulate shield.

54. A sensor sub-assembly housing as claimed in claim 50 further comprising a through hole in said ceramic tube.

55. A sensor sub-assembly housing as claimed in claim 54 further comprising a thermocouple which passes through said ceramic tube in one of said through holes.

56. A packaged sensor sub-assembly comprising:

a bottom housing;

said sensor having contact pads and a perimeter, metal bumps formed on said contact pads, said sensor residing in said bottom housing;

a top cover having through holes therethrough, said through holes being aligned with said contact pads of said sensor;

said through holes being filled with nickel so as to form a transconnect;

said transconnect engaging said bumps;

conductive paste; and

,

glass securing said top cover, sensor, transconnect and bottom housing together forming a reference cavity bounded by said top cover, said sensor and said glass.

57. A packaged sensor sub-assembly as claimed in claim 56 wherein said top cover includes top and bottom surfaces and said transconnect extends radially from said through holes onto the top and bottom surfaces of said top cover.

58. A packaged sensor sub-assembly as claimed in claim 56 wherein said bottom housing, said sensor and said top cover are made selected from the group of aluminum nitride or silicon carbide.

59. A packaged sensor sub-assembly as claimed in claim 56 in combination with a sensor sub-assembly housing comprising a stainless steel housing having an interior and an exterior, said interior includes threads thereon, a ceramic tube resides in said interior of said stainless steel housing, brazing resides intermediate said interior threads of said stainless steel housing and said ceramic tube, and, said brazing secures said ceramic tube and said stainless steel housing together upon heating said brazing;

and,

said sensor sub-assembly being glassed to secure said stainless steel housing and said ceramic tube together thereby creating a reference cavity.

60. A sensor sub-assembly housing comprising a stainless steel tube, a ceramic tube having through holes, a reference cavity, and an opening therein, said ceramic tube being partially brazed to said stainless steel tube, said ceramic tube extending outside said stainless steel tube a sufficient length to thermally decouple said stainless steel tube from said sensor.

61. A sensor sub-assembly housing as claimed in claim 60 in combination with a packaged sensor sub-assembly comprising a bottom housing, a sensor having contact pads and a perimeter, said sensor residing in said bottom housing;

said through holes fo said ceramic tube being aligned with said contact pads of said sensor, pins and conductive paste, said pins residing in said through holes and engaging said contact pads of said sensors, said conductive paste securing said pins to said through holes, glass securing said sensor, bottom housing and ceramic housing together.

62. A packaged sensor sub-assembly comprising a sensor sub-assembly inserted into and glassed to a kovar header brazed to a stainless steel housing, said sensor sub-assembly comprising a bottom housing, said sensor having contact pads and a perimeter, said sensor residing in said bottom housing, a top cover having through holes therethrough, said through holes being aligned with said contact pads of said sensor, pins and conductive paste, said pins residing in said through holes and engaging said contact pads of said sensors, said conductive paste securing said pins to said through holes, glass securing and sealing said top cover, sensor, and bottom housing together, and, glass securing said pins to said top cover.

63. A packaged sensor sub-assembly as claimed in claim 62 wherein the sensor sub-assembly is first glassed to the Kovar header before said Kovar header is brazed to said stainless steel housing.

64. A method of packaging a sensor sub-assembly comprising the steps of:

inserting a ceramic tube inside a stainless steel housing, said ceramic tube having through holes, and said stainless steel housing includes an interior having threads thereon;

inserting brazing material in the gap intermediate said stainless steel housing and said ceramic tube such that said brazing material is conformal to said interior threads;

heating said brazing material and securing said ceramic tube to said stainless steel housing;

inserting a sensor sub-assembly having contact pads into said stainless steel housing in alignment with said through holes of said ceramic tube and in proximity to said ceramic tube; and

,

inserting and heating glass to secure said sensor sub-assembly to said ceramic tube and said stainless steel housing forming a reference cavity.

65. A method of packaging a sensor sub-assembly as claimed in claim 64 further comprising the steps of:

coating pins with paste;

inserting said coated pins into said through holes of said ceramic tube and into engagement with said contact pads; and

,

heating said paste to secure said pins to said ceramic tube and contact pads.

66. A method of packaging a sensor sub-assembly as claimed in claim 65 further comprising the steps of:

placing a metal bump on each of said contact pads prior to said step of inserting said sensor sub-assembly having contact pads into said stainless steel housing in alignment with said through holes of said ceramic tube and in proximity to said ceramic tube.

67. A method of packaging a sensor sub-assembly as claimed in claim 65 further comprising the steps of:

inserting a blow-out stopper in said interior of said stainless steel tube prior to said step of heating said brazing material and securing said ceramic tube to said stainless steel housing; and

,

attaching a particulate shield to said stainless steel housing to protect said sensor sub-assembly.

68. A method of packaging a sensor sub-assembly as claimed in claim 65 wherein said paste is a conductive paste.

69. A method of packaging a sensor sub-assembly as claimed in claim 65 wherein said paste is a nonconductive paste.

70. A method of packaging a sensor sub-assembly in a stainless steel housing having an interior and an exterior, comprising the steps of:

coating pins with paste;

inserting said coated pins into a ceramic tube having through holes;

placing said coated pins inside said through holes in said ceramic tube and heating said paste to secure said pins to said ceramic tube;

smoothening one end of said ceramic tube and said pins located therein such that said end of said pins are coplanar with said ceramic tube;

attaching said pins to bumps on contact pads of a sensor;

heating said ceramic tube and said sensor and bumps on said contact pads;

prewetting the interior of a stainless steel housing with a glass paste;

inserting said ceramic tube and sensor in said interior of said prewet stainless steel housing;

inserting additional glass to secure said sensor to said ceramic tube and said stainless steel housing to form a reference cavity;

firing said ceramic tube, said sensor and said stainless steel housing to cure said glass.

71. A method of packaging a sensor sub-assembly in a stainless steel housing having an interior and an exterior as claimed in claim 70 wherein said step of firing said ceramic tube, said sensor and said stainless steel housing to cure said glass is performed at 800 degrees centigrade for 30 in a nitrogen ambient environment.

72. A method of packaging a sensor sub-assembly in a stainless steel housing having an interior and an exterior as claimed in claim 70 wherein said step of heating said ceramic tube and said sensor and bumps on said contact pads is performed at 650 degrees centigrade.

73. A method of packaging a sensor sub-assembly in an aluminum nitride header partially secured within a stainless steel housing having an interior, an exterior and a reference cavity formed therein, said sensor sub-assembly including contact pads, comprising the steps of:

coating said aluminum nitride header with a metallic material;

inserting said aluminum nitride header having four through holes therein into said stainless steel housing;

attaching said metallic material to said stainless steel housing;

coating through hole openings with conductive paste;

inserting conductive pins in said through holes coating said holes with conductive paste;

heating said header, said stainless steel housing, said pins and said conductive paste so as to cure and harden said conductive paste;

reapplying said conductive paste on said cured and hardened conductive paste which is proximate said reference cavity;

inserting said sensor sub-assembly in said reference cavity such that said sensor contact pads are aligned with said through holes of said aluminum nitride header;

heating and bonding said sensor sub-assembly to said reference cavity such that electrical conductivity may be established between said contact pads and said pins; and

,

sealing between said aluminum nitride header and said sensor locking air between said reference cavity and said sensor.

74. A method of packaging a sensor sub-assembly as claimed in claim 73 wherein said step of attaching said metallic material to said stainless steel housing is performed by laser welding.

75. A method of packaging a sensor sub-assembly as claimed in claim 73 wherein said step of attaching said metallic material to said stainless steel housing is performed by brazing.

76. A method of packaging a sensor sub-assembly as claimed in claim 73 wherein said metallic material is nickel.