PRESSURE SENSOR

• US 20080054383A1
• Filed: 09/01/2006
• Published: 03/06/2008
• Est. Priority Date: 09/01/2006
• Status: Active Grant

• Current Assignee: Grundfos A/S (Poul Due Jensens Fond)
• Original Assignee: Grundfos A/S (Poul Due Jensens Fond)
• Inventors: MEHALSO, Robert M., PEDERSEN, Heins K., POND, Stephen F., DYRBYE, Karsten, ERIKSEN, Gert Friis
• Granted Patent: US 7,713,771 B2
• Time in Patent Office: Days
• US Class Current: 257/415
• CPC Class Codes: G01L 9/0042 Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms details about the integration or bonding of piezoresistor in or on the diaphragm G01L9/0052 and G01L9/0057 respectively
• CPC Class Codes: H01L 29/84 controllable by variation of applied mechanical force, e.g. of pressure

Abstract

A differential pressure sensor includes a micro-electromechanical sensor die fabricated as a plurality of sensor die sites on a semiconductor wafer, and then singularized, the sensor die having a top face surface including die electrical output pads exposed to a first test fluid source and a bottom side surface exposed to a second test fluid source. The differential pressure further has a sensor die support member having a die support member fluid access port with a support member port perimeter; wherein one of the top face surface or the bottom side surface is sealed fully around the support member port perimeter by a wafer scale seal formed on the plurality of sensor die sites before die singulation. Wafer scale seals may be formed by a photofabrication process, screen printing, stamp printing, or pressure transfer printing. Some embodiments may include a photofabricated seal formed by a photosensitive polydimethylsiloxane material, by a filled photofabricated mold, and by photopatterned glass frit.

Claims

1. A differential pressure sensor comprising:

a micro-electromechanical sensor die fabricated as a plurality of sensor die sites on a semiconductor wafer, and then singularized, the sensor die having a top face surface including die electrical output pads exposed to a first test fluid source and a bottom side surface exposed to a second test fluid source; and

a sensor die support member having a die support member fluid access port with a support member port perimeter;

wherein one of the top face surface or the bottom side surface is sealed fully around the support member port perimeter by a first wafer scale seal formed on the plurality of sensor die sites before die singulation.

2. The differential pressure sensor of claim 1, wherein the first wafer scale seal is formed of a first seal material applied by one of a photofabrication process, screen printing, stamp printing, or pressure transfer printing.

3. The differential pressure sensor of claim 1, wherein the first wafer scale seal is formed of a compressible material.

4. The differential pressure sensor of claim 2, wherein the first seal material is applied by a photofabrication process and the first seal material is a photosensitive polydimethylsiloxane material.

5. The differential pressure sensor of claim 2, wherein the first seal material is applied by a photofabrication process and the first wafer scale seal is formed by filling a photofabricated mold with an elastomeric material and removing the photofabricated mold.

6. The differential pressure sensor of claim 5, wherein the elastomeric material is polydimethylsiloxane or silicone rubber.

7. The differential pressure sensor of claim 5, wherein the photofabricated mold is formed using a dry film photoresist.

8. The differential pressure sensor of claim 1, wherein the first wafer scale seal is formed of a first seal material that has an intermediate cure state and a final cure state;

the sensor die is assembled to the die support member bringing the first seal material into contact with the die support member while the first seal material is in the intermediate cure state; and

wherein the first seal material is subsequently finally cured so as to bond to the die support member.

9. The differential pressure sensor of claim 1, wherein the one of the top face surface or the bottom side surface is coated with an amorphous metal layer in a first sensing area that is exposed to a central portion of the support member port area not covered by the wafer scale seal.

10. The differential pressure sensor of claim 9, wherein the sensor die support member is made of a ceramic material;

the wafer scale seal is formed of a low temperature glass frit material with a curing temperature of 450°

C. or less;

the sensor die is assembled to the die support member bringing the glass frit material into contact with the die support member and subsequently curing the glass frit so as to bond to the die support member.

11. The differential pressure sensor of claim 1, wherein the first wafer scale seal is mechanically compressed against the die support member.

12. The differential pressure sensor of claim 1, wherein the die support member is comprised of polyphenylene sulphide.

13. The differential pressure sensor of claim 1, further comprising a top cover for assembly to the sensor die and sensor die support member after the sensor die is supported on the sensor die support, a top cover fluid access port with a top cover port perimeter;

wherein the other of the top face surface or the bottom side surface is sealed fully around the top cover port perimeter by an applied-in-place seal formed on one of the sensor die or the top cover before assembly of the top cover.

14. The differential pressure sensor of claim 13, wherein the applied-in-place seal is comprised of a compressible material.

15. The differential pressure sensor of claim 14, wherein the applied-in-place seal is cured before assembly of the top cover and is mechanically compressed after assembly to the top cover.

16. The differential pressure sensor of claim 13, wherein the applied-in-place seal is formed of a second seal material that has an intermediate cure state and a final cure state;

the top cover is assembled to the sensor die and sensor die support member bringing the second seal material into contact with the top cover and the sensor die while the second seal material is in the intermediate cure state; and

wherein the second seal material is subsequently finally cured so as to bond to the top cover and sensor die.

17. The differential pressure sensor of claim 13, wherein the other of the top face surface or the bottom side surface is coated with an amorphous metal layer in a second sensing area that is exposed to a central portion of the top cover port area not covered by the apply-in-place seal.

18. The differential pressure sensor of claim 13, further comprising an electrical connection wiring board supported by the die support member and electrically connected to the die electrical output pads by one of thermocompression bonding, reflow soldering or anisotropic conductive epoxy.

19. The differential pressure sensor of claim 18, wherein the electrical connection wiring board is first electrically connected to the die electrical output pads forming an attached die subassembly that is then assembled to the die support member.

20. The differential pressure sensor of claim 19, wherein the wafer scale seal is formed on the bottom side surface of the sensor die and the apply-in-place seal extends to cover the die output pads.

21. The differential pressure sensor of claim 13, wherein the top cover is comprised of polyphenylene sulphide.

22. The differential pressure sensor of claim 13, wherein the die support member and the top cover are formed in one piece.

23. The differential pressure sensor of claim 11, wherein an outer case perimeter is formed at the outermost area of overlap of the top cover and die support member when assembled and further comprising an outer case seal formed along at least a portion of the outer case perimeter.

24. The differential pressure sensor of claim 23, wherein the outer case seal is an apply-in-place seal formed on one of the top cover or die support member prior to the assembly of the top cover to the die support member.

25. The differential pressure sensor of claim 23, wherein the outer case seal is a formed as an ultrasonic weld of top cover and die support material along at least a portion of the outer case perimeter.

26. The differential pressure sensor of claim 23, wherein the top cover and die support member are held in mechanical compression after assembly of the top cover to the die support member and the outer case seal is a compressible gasket member interposed between the top cover and the die support member.

27. The differential pressure sensor of claim 13, wherein the applied-in-place seal is formed of a seal material applied by one of screen printing, stamp printing, pressure transfer printing, dispensing through a needle having a seal-shaped hollow portion, or dispensing through a needle that is moved along a seal pattern pathway.

28. The differential pressure sensor of claim 1, further comprising a top cover for assembly to the sensor die and sensor die support member after the sensor die is supported on the sensor die support, a top cover fluid access port with a top cover port perimeter;

wherein the other of the top face surface or the bottom side surface is sealed fully around the top cover port perimeter by a second wafer scale seal formed on the plurality of sensor die sites before die singulation.

29. The differential pressure sensor of claim 28, wherein the second wafer scale seal is formed of a second seal material applied by one of a photofabrication process, screen printing, stamp printing, or pressure transfer printing.

30. The differential pressure sensor of claim 28, wherein the second wafer scale seal is formed of a compressible material.

31. A differential pressure sensor assembly comprising:

a micro-electromechanical sensor die fabricated as a plurality of sensor die sites on a semiconductor wafer, and then singularized, the sensor die having a top face surface including die electrical output pads and a bottom side surface for exposure to two test fluid sources;

a sensor die support member having die support side, a support member outer side, and a die support member fluid access port therethrough having a support member port perimeter on the die support side and having a die support seal member holding feature located on the support member outer side;

a first wafer scale seal formed on the plurality of sensor die sites before die singulation adapted to seal one of the top face surface or the bottom side surface fully around the support member port perimeter;

a top cover for assembly to the sensor die and sensor die support member after the sensor die is supported on the sensor die support, the top cover having a die interface side, a top cover outer side, and a top cover fluid access port therethrough having a top cover port perimeter on the die interface side;

an applied-in-place seal formed on the other of the sensor die or the top cover before assembly of the top cover adapted to seal the other of the top face surface or the bottom side surface fully around the top cover port perimeter; and

a die support seal member that is held by the die support seal member holding feature, the die support seal member having a die support seal interior opening aligned with the die support fluid access port and adapted to seal against the support member outer side and around the die support member fluid access port when compressed.

32. The differential pressure sensor of claim 31, wherein the die support seal member is an O-ring.

33. The differential pressure sensor of claim 31, wherein the top cover has a top cover seal member holding feature located on the top cover outer side, and a top cover seal member that is held by the top cover seal member holding feature, the top cover seal member having a top cover seal interior opening aligned with the top cover fluid access port adapted to seal against the top cover outer side and around the top cover fluid access port when compressed.

34. The differential pressure sensor of claim 33, wherein the top cover seal member is an O-ring.

35. The differential pressure sensor of claim 33, wherein the top cover is assembled to the die support member and sensor die and further comprising a rigid outer sensor case having a sensor cavity formed by a sensor cavity wall enclosure having an interior wall surface adapted to receive the assembled top cover, die support member and sensor die, and having first and second test fluid access ports formed through the sensor cavity wall enclosure in fluid communication with the top cover fluid access port and the die support member fluid access port, respectively, the sensor cavity dimensioned so as to mechanically compress the top cover seal member and the die support seal member and the first and second test fluid access ports having first and second openings in the interior wall surface that are positioned and dimensioned to lie within the top cover seal interior opening and the die support seal interior opening, respectively.

36. The differential pressure sensor of claim 35, wherein the die support member and the top cover are formed in one piece.

37. The differential pressure sensor of claim 31, wherein the first wafer scale seal is formed of a seal material applied by one of a photofabrication process, screen printing, stamp printing, or pressure transfer printing.

38. A differential pressure sensor assembly comprising:

a micro-electromechanical sensor die fabricated as a plurality of sensor die sites on a semiconductor wafer, and then singularized, the sensor die having a top face surface including die electrical output pads and a bottom side surface for exposure to two test fluid sources;

a sensor die support member having die support side, a support member outer side, and a die support member fluid access port therethrough having a support member port perimeter on the die support side and having a die support seal member holding feature located on the support member outer side;

a first wafer scale seal formed on the plurality of sensor die sites before die singulation adapted to seal one of the top face surface or the bottom side surface fully around the support member port perimeter; and

a die support seal member that is held by the die support seal member holding feature, the die support seal member having a die support seal interior opening aligned with the die support fluid access port and adapted to seal against the support member outer side and around the die support member fluid access port when compressed.

39. The differential pressure sensor of claim 38, further comprising:

a top cover for assembly to the sensor die and sensor die support member after the sensor die is supported on the sensor die support, the top cover having a die interface side, a top cover outer side, and a top cover fluid access port therethrough having a top cover port perimeter on the die interface side; and

a second wafer scale seal formed on the plurality of sensor die sites before die singulation adapted to seal the other of the top face surface or the bottom side surface fully around the top cover port perimeter;

wherein the top cover has a top cover seal member holding feature located on the top cover outer side, and a top cover seal member that is held by the top cover seal member holding feature, the top cover seal member having a top cover seal interior opening aligned with the top cover fluid access port adapted to seal against the top cover outer side and around the top cover fluid access port when compressed.

40. The differential pressure sensor of claim 39, wherein the top cover is assembled to the die support member and sensor die and further comprising a rigid outer sensor case having a sensor cavity formed by a sensor cavity wall enclosure having an interior wall surface adapted to receive the assembled top cover, die support member and sensor die, and having first and second test fluid access ports formed through the sensor cavity wall enclosure in fluid communication with the top cover fluid access port and the die support member fluid access port, respectively, the sensor cavity dimensioned so as to mechanically compress the top cover seal member and the die support seal member and the first and second test fluid access ports having first and second openings in the interior wall surface that are positioned and dimensioned to lie within the top cover seal interior opening and the die support seal interior opening, respectively.

41. The differential pressure sensor of claim 40, wherein the die support member and the top cover are formed in one piece.

42. The differential pressure sensor of claim 39, wherein the first and second wafer scale seals are formed of first and second seal materials, respectively, applied by one of a photofabrication process, screen printing, stamp printing, or pressure transfer printing.

43. The differential pressure sensor of claim 38, further comprising:

a rigid outer sensor case having a sensor cavity formed by a sensor cavity wall enclosure having an interior wall surface adapted to receive the die support member and sensor die, and having a first test fluid access port formed through the sensor cavity wall enclosure and having a first opening in the interior wall surface with a first access port inner perimeter;

a second wafer scale seal formed on the plurality of sensor die sites before die singulation adapted to seal the other of the top face surface or the bottom side surface fully around the first access port inner perimeter; and

a second test fluid access port formed through the sensor cavity wall enclosure in fluid communication with the die support member fluid access port;

wherein the sensor cavity is dimensioned so as to mechanically compress the die support seal member and the second wafer scale seal and wherein the second test fluid access port has a second opening in the interior wall surface that is positioned and dimensioned to lie within the die support seal interior opening.

44. A differential pressure sensor comprising:

a micro-electromechanical sensor die fabricated as a plurality of sensor die sites on a semiconductor wafer, and then singularized, the sensor die having a top face surface including die electrical output pads and a bottom side surface for exposure to two test fluid sources;

a rigid outer sensor case having a sensor cavity formed by a sensor cavity wall enclosure having an interior wall surface adapted to receive the sensor die, and having first and second test fluid access ports formed through the sensor cavity wall enclosure and having first and second openings in the interior wall surface with first and second access port inner perimeters; and

first and second wafer scale seals formed on the plurality of sensor die sites before die singulation adapted to seal the top face surface and the bottom side surface fully around the first and second access port inner perimeters;

wherein the sensor cavity is dimensioned so as to ensure contact between the first and second wafer scale seals and the first and second test fluid access ports, respectively.

45. The differential pressure sensor of claim 44, wherein the sensor cavity is dimensioned so as to mechanically compress at least one of the first and second wafer scale seals.

46. The differential pressure sensor of claim 44, wherein at least one of the first and second wafer scale seals are formed of a seal material that may be cured after die singulation.