Pressure sensor and process for producing the pressure sensor

• US 6,732,590 B1
• Filed: 11/20/2002
• Issued: 05/11/2004
• Est. Priority Date: 11/20/2002
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Schröder, Martin, Gottlieb, Alfred
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): Jenkins, Jermaine
• Application Number:
  US10/301,096
• Publication Number:
  US 20040093954A1
• Time in Patent Office: 538 Days
• Field of Search: 737/00--56
• US Class Current: 73/754
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
• CPC Class Codes: G01L 19/147 Details about the mounting of the sensor to support or covering means
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48465 the other connecting portion not on the bonding area being a wedge bond, i.e. ball-to-wedge, regular stitch
• CPC Class Codes: H01L 2224/49175 Parallel arrangements
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• 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

Abstract

The invention relates to a pressure sensor with an MEM structure (micro electro mechanical structure), which has a hollow housing in which a semiconductor chip with a pressure-sensitive area is arranged. In its interior and with parts of the semiconductor chip, the housing is covered by a first plastic compound, which has a lower level of deformation than a second plastic compound, which partly covers the pressure-sensitive area of the semiconductor chip.

Claims

1. A pressure sensor, comprising:

a semiconductor chip having a pressure-insensitive area, a pressure-sensitive area for receiving an external pressure, and a plurality of contact areas configured on said pressure-insensitive area;

a hollow housing having a housing interior, a housing base on which said semiconductor chip is configured, a housing wall surrounding said semiconductor chip, and a plurality of flat conductors each having an internal section projecting from said housing wall into said housing interior and an external section projecting from said housing wall away from said housing interior;

a plurality of connecting elements, each one of said plurality of connecting elements electrically connecting one of said plurality of contact areas to said internal section of a respective one of said plurality of flat conductors;

a first plastic compound covering said plurality of connecting elements, said internal section of each one of said plurality of plurality of flat conductors, and said plurality of contact areas; and

a second plastic compound at least partly covering said pressure-sensitive area of said semiconductor chip;

said first plastic compound undergoing less deformation than said second plastic compound when under a given pressure loading.

2. The pressure sensor according to claim 1, wherein said second plastic compound is a plastic gel of a resilient elastomer based on silicone.

3. The pressure sensor according to claim 1, wherein said first plastic compound includes a thermosetting plastic.

4. The pressure sensor according to claim 3, wherein said thermosetting plastic is an epoxy resin or a silicone resin.

5. The pressure sensor according to claim 1, wherein said hollow housing includes a housing cover formed with an opening exposing said pressure-sensitive area and said second plastic compound.

6. The pressure sensor according to claim 1, wherein said semiconductor chip is formed with a hermetically sealed cavity under a reference pressure.

7. The pressure sensor according to claim 6, comprising:

a gas-tight adhesive layer;

said semiconductor chip including a rigid semiconductor wall made of semiconductor chip material and bounding said cavity;

said pressure-sensitive area of said semiconductor chip being formed by a pressure-sensitive membrane of semiconductor chip material;

said cavity having a cylindrical shape and being sealed off from said pressure-sensitive membrane;

said gas-tight adhesive layer located between said semiconductor wall and said housing base; and

said gas-tight adhesive layer serving as a hermetic closure for said cavity.

8. The pressure sensor according to claim 1, wherein:

said housing base has an outer underside that defines a level; and

said external section of each one of said plurality of said flat conductors is configured at said level of said outer underside of said housing base.

9. The pressure sensor according to claim 1, wherein:

said housing base defines a level; and

said external section of each one of said plurality of said flat conductors is configured at said level of said housing base.

10. A vehicle tire including a pressure sensor, the pressure sensor comprising:

a semiconductor chip having a pressure-insensitive area, a pressure-sensitive area for receiving an external pressure, and a plurality of contact areas configured on said pressure-insensitive area;

a hollow housing having a housing interior, a housing base on which said semiconductor chip is configured, a housing wall surrounding said semiconductor chip, and a plurality of flat conductors each having an internal section projecting from said housing wall into said housing interior and an external section projecting from said housing wall away from said housing interior;

a plurality of connecting elements, each one of said plurality of connecting elements electrically connecting one of said plurality of contact areas to said internal section of a respective one of said plurality of flat conductors;

a first plastic compound covering said plurality of connecting elements, said internal section of each one of said plurality of plurality of flat conductors, and said plurality of contact areas; and

a second plastic compound at least partly covering said pressure-sensitive area of said semiconductor chip;

said first plastic compound undergoing less deformation than said second plastic compound when under a given pressure loading.

11. A motor vehicle including a pressure sensor, the pressure sensor comprising:

a semiconductor chip having a pressure-insensitive area, a pressure-sensitive area for receiving an external pressure, and a plurality of contact areas configured on said pressure-insensitive area;

a hollow housing having a housing interior, a housing base on which said semiconductor chip is configured, a housing wall surrounding said semiconductor chip, and a plurality of flat conductors each having an internal section projecting from said housing wall into said housing interior and an external section projecting from said housing wall away from said housing interior;

a plurality of connecting elements, each one of said plurality of connecting elements electrically connecting one of said plurality of contact areas to said internal section of a respective one of said plurality of flat conductors;

a first plastic compound covering said plurality of connecting elements, said internal section of each one of said plurality of plurality of flat conductors, and said plurality of contact areas; and

a second plastic compound at least partly covering said pressure-sensitive area of said semiconductor chip;

said first plastic compound undergoing less deformation than said second plastic compound when under a given pressure loading.

12. A process for producing a pressure sensor, the process which comprises:

providing a hollow housing incorporating a semiconductor chip having a pressure-sensitive area and a plurality of pressure-insensitive areas, the hollow housing formed with an opening exposing at least the pressure-sensitive area;

applying a first plastic compound to the plurality of the pressure-insensitive areas within the hollow housing while sealing interfaces between the first plastic compound and surfaces of housing inner walls and while sealing surfaces of the pressure-insensitive areas;

applying a second plastic compound to the pressure-sensitive area of the semiconductor chip while sealing an interface between the first plastic compound and the second plastic compound in a gas-tight manner; and

providing the first plastic compound with material characteristics and providing the second plastic compound with material characteristics such that the first plastic compound undergoes a lower deformation than the second plastic compound when under a common external pressure condition.

13. The process according to claim 12, which comprises first producing a plurality of semiconductor chips having pressure-sensitive areas by:

etching out cavities at a plurality of semiconductor chip positions from a rear side of a semiconductor wafer until reaching translucent and/or a pressure-sensitive membranes at the upper side of the semiconductor wafer; and

after selectively applying electrodes to the pressure-sensitive membranes and applying contact areas to pressure-insensitive areas of the semiconductor wafer, dividing the semiconductor wafer into the plurality of semiconductor chips.

14. The process according to claim 13, which comprises pressure die-casting a plurality of hollow housings on a flat lead frame and embedding transition sections of flat conductors in housing walls, each of the plurality of hollow housings having a housing base.

15. The process according to claim 14, which comprises:

bonding each one of the plurality of the semiconductor chips onto the housing base of a respective one of the plurality of hollow housings;

sealing off the cavities in a gas-tight manner; and

then

connecting internal sections of the flat conductors to the contact areas of the semiconductor chip using bonding wires.

16. The process according to claim 12, which comprises after applying the first plastic compound and the second plastic compound, fitting a housing cover having an opening to the hollow housing, leaving the pressure-sensitive area free.