Transducer packaging assembly for use in sensing unit subjected to high G forces

• US 6,570,485 B1
• Filed: 11/17/2000
• Issued: 05/27/2003
• Est. Priority Date: 11/17/2000
• Status: Expired due to Fees

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.), Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Espinosa, Frank F., Stratton, Thomas G., Bender, Terrence D., Ciglenec, Reinhart, Mallison, Edgar R., Bodin, Joel J.
• Primary Examiner(s): Easthom, Karl D.
• Application Number:
  US09/715,480
• Time in Patent Office: 921 Days
• Field of Search: 338/4, 338/36, 338/42, 296/211, 737/20, 737/21, 737/26, 737/27, 737/07
• US Class Current: 338/42
• CPC Class Codes: G01L 19/02 Arrangements for preventing, or for compensating for, effects of inclination or acceleration of the measuring device; Zero-setting means for aneroid barometers G01L7/14
• CPC Class Codes: G01L 19/06 Means for preventing overload or deleterious influence of the measured medium on the measuring device or vice versa
• CPC Class Codes: G01L 19/141 Monolithic housings, e.g. molded or one-piece housings
• CPC Class Codes: G01L 19/147 Details about the mounting of the sensor to support or covering means
• CPC Class Codes: G01L 19/149 of immersion sensor, e.g. where the sensor is immersed in the measuring medium or for in vivo measurements, e.g. by using catheter tips
• 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: Y10T 29/49103 Strain gauge making

Abstract

A transducer packaging assembly for use in a sensing unit subjected to high forces of acceleration includes a base having a cavity. A pressure sensitive semiconductor die is bonded to a large backplate having a shape so that it nestles into the cavity but is spaced from a surface of the cavity. A planar cover secured to the base has a hole larger than the die but smaller than the backplate, and thin wires extend from the die to electrical connections on the assembly. A viscous fluid fills a space between the backplate and the cavity, and a space between the backplate and the cover, and transmits a pressure to be measured to the pressure sensitive die. The viscous fluid has a sufficiently high viscosity to oppose movement of the backplate relative to the cavity while cushioning the pressure sensitive die and the backplate from forces of acceleration.

Claims

1. A transducer packaging assembly for use in a sensing unit having a passage filled with a viscous fluid for transmitting a pressure to be measured to said packaging assembly, said sensing unit subjected to high forces of acceleration, comprising:

a pressure sensitive die having a frontside and a backside, said frontside having electrical connections;

a backplate, said backplate having a thickness and a shape;

means for bonding said backside to said backplate;

a base having a cavity, said cavity having a shape conforming to said shape of said backplate with said cavity being of a size so that said backplate nestles in said cavity and is spaced from a surface of said cavity;

said viscous fluid filling a space between said backplate and said cavity, with said fluid transmitting said pressure to be measured to said pressure sensitive die;

means for retaining said backplate within said cavity; and

said backplate moveable and floatable within said cavity with said viscous fluid having a viscosity sufficient to impede movement of said backplate relative to said cavity due to forces of acceleration.

2. The transducer packaging assembly of claim 1 wherein said means for retaining said backplate within said cavity comprises a cover, said cover secured to said base and having an opening larger than said die and smaller than said backplate, with said viscous fluid filling a space between said backplate and said cover.

3. The transducer packaging assembly of claim 1 wherein said backplate comprises a circular cross-section portion for complementary receipt in said cavity, a transition portion and a termination portion having a rectangular cross section.

4. The transducer packaging assembly of claim 1 wherein said backplate is formed from a material selected from the group consisting of silicon, Pyrex™

, and SD2 glass.

5. The transducer packaging assembly of claim 1 further comprising a thin sheet of a semipermeable material immersed in said viscous fluid and surrounding a portion of said backplate.

6. The transducer packaging assembly of claim 1 wherein said viscous fluid comprises particles of a material selected so that the density of said viscous fluid is equal to the density of said combination of said pressure sensitive die and said backplate.

7. The transducer packaging assembly of claim 6 wherein said material for said particles comprises an oxide or a titanate of a heavy metal.

8. The transducer packaging assembly of claim 1 wherein a capability of said assembly to withstand an acceleration force varies with a direction of said acceleration force and said assembly is oriented in said sensing unit so that a greater acceleration force occurs in a direction of a greater capability to withstand said greater acceleration force.

9. The transducer packaging assembly of claim 1 further comprising electrical conductors attached to said electrical connections.

10. The transducer packaging assembly of claim 1 wherein said pressure sensitive die includes a resistance temperature bridge.

11. A transducer packaging assembly for use in a sensing unit having a passage filled with a viscous fluid for transmitting a pressure to be measured to said packaging assembly, said sensing unit subjected to high forces of acceleration, comprising:

a pressure sensitive die having a frontside and a backside;

a backplate having a lower portion, a transition portion and a termination portion;

means for bonding said backside to said backplate;

a base having a cavity, said cavity having a shape for complementary receipt of said lower portion with said cavity being of a size so that said lower portion nestles in said cavity and is spaced from a surface of said cavity;

a cover secured to said base, said cover having an opening larger than said die and smaller than said backplate;

thin wires extending from said frontside of said pressure sensitive die; and

said viscous fluid filling a space between said backplate and said cavity and a space between said backplate and said cover, said viscous fluid transmitting said pressure to be measured to said pressure sensitive die with said backplate moveable and floatable in said cavity and said viscous fluid opposing movement of said backplate relative to said cavity, with said combination of said pressure sensitive die and said backplate cushioned by said viscous fluid from forces of acceleration.

12. The transducer packaging assembly of claim 11 wherein said lower portion comprises a circular cross-section portion and said termination portion has a rectangular cross section.

13. The transducer packaging assembly of claim 11 wherein said backplate is formed from a material having a TCE substantially equal to a TCE of said pressure sensitive die.

14. The transducer packaging assembly of claim 11 wherein a capability of said assembly to withstand an acceleration force varies with a direction of said acceleration force and said assembly is oriented in said sensing unit so that a greater acceleration force occurs in a direction of a greater capability to withstand said greater acceleration force.

15. The transducer packaging assembly of claim 11 further comprising a thin sheet of a semipermeable material immersed in said viscous fluid and surrounding a portion of said backplate.

16. The transducer packaging assembly of claim 11 wherein said viscous fluid is a single-phase fluid.

17. The transducer packaging assembly of claim 11 wherein said viscous fluid is a multiphase fluid.

18. A method of constructing a transducer assembly having a pressure sensitive die for use in a sensing unit subjected to high forces of acceleration, said sensing unit having a passage for transmitting a pressure to be measured to said pressure sensitive die, comprising the following steps:

providing a backplate having said pressure sensitive die bonded thereto;

providing a base having a cavity slightly larger than said backplate but of the same shape as said backplate;

nestling said backplate into said cavity with said backplate maintained in a spaced relationship to a surface of said cavity;

bonding a cover to said base, said cover having a hole larger than said pressure sensing die but smaller than said backplate;

making electrical connections at said pressure sensitive die; and

filling a space between said backplate and said cavity, a space between said backplate and said cover, and said passage with a viscous fluid, said viscous fluid transmitting said pressure to be measured to said pressure sensitive die with said backplate movable and floatable in said cavity and said viscous fluid cushioning said pressure sensitive die and said backplate from forces of acceleration.

19. The method of claim 18 wherein said step of nestling said backplate into said cavity with said backplate maintained in a spaced relationship to a surface of said cavity comprises the step of placing a thin sheet of semipermeable material over said cavity before nestling said backplate into said cavity.

20. The method of claim 18 wherein the step of filling a space between said backplate and said cavity and a space between said backplate and said cover with a viscous fluid comprises the step of providing a viscous fluid comprising particles of a material selected so that the density of said viscous fluid is equal to the density of said combination of said pressure sensitive die and said backplate.

21. The method of claim 18 further comprising the step of mounting the transducer packaging assembly in a sensing unit so that said assembly is oriented in said sensing unit so that a greater acceleration force occurs in a direction of a greater capability to withstand said greater acceleration force.