Tire pressure sensors and methods of making the same

• US 20020168795A1
• Filed: 09/18/2001
• Published: 11/14/2002
• Est. Priority Date: 05/11/2001
• Status: Active Grant

• Current Assignee: Melexis Technologies SA
• Original Assignee: Melexis NV (Sensinnovat BVBA)
• Inventors: Schuurmans, Johan
• Granted Patent: US 7,060,216 B2
• Time in Patent Office: Days
• US Class Current: 438/106
• CPC Class Codes: B29C 33/06 using radiation , e.g. electro-magnetic waves, induction heating
• CPC Class Codes: H01L 21/565 Moulds
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• 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 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• CPC Class Codes: H01L 23/3107 the device being completely enclosed
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• 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 2924/181 Encapsulation
• CPC Class Codes: H01L 2924/1815 Shape

Abstract

The elements of a tire pressure monitoring and transmitting system are encapsulated into a single package. A pressure sensitive device is covered with a flexible gel coat and then inserted into a molding tool cavity. A removable pin is incorporated into the molding tool and in its normal position is in contact with the gel. A molding compound is injected into the cavity so as to encapsulate the device and gel coat. When the pin is extracted and the device ejected from the molding cavity, an airway is left defined by the removable pin. The airway exposes the flexible gel covering the pressure sensitive device to the local air pressure, whereby the gel, being flexible, transfers the pressure to the pressure sensitive device.

Claims

1. A method of encapsulating a pressure sensitive integrated circuit within a plastic molded package, comprising:

providing an integrated circuit, the integrated circuit including a pressure sensing element;

applying a quantity of gel to the integrated circuit such as to cover at least the pressure sensing element, thereby forming a gel-covered assembly;

inserting the gel-covered assembly into a cavity of a molding tool;

attaching a retractable pin to the gel-covered assembly;

introducing a plastic mold compound into the cavity so as to encapsulate the gel-covered assembly and at least a portion of the pin; and

removing the pin from the gel such as to leave a passageway in the plastic mold encapsulating the gel-covered assembly, thereby exposing the gel to the pressure of the atmosphere through the passageway, whereby the gel transfers the pressure to the pressure sensitive integrated circuit.

2. The method of claim 1, wherein the pin is a fixed part of the mold tool and wherein removing includes ejecting the encapsulated assembly from the mold tool such that the pin extracts from the encapsulated assembly.

3. The method of claim 1, wherein the pin is a hollow tube, and wherein the method further comprises applying a reduced air pressure to an external end of the tube to maintain contact between the gel-covered assembly and the tube during the encapsulation.

4. The method of claim 1, wherein the integrated circuit is provided on a metal carrier.

5. The method of claim 4, wherein the gel covers the entire exposed portion of the integrated circuit on the carrier.

6. The method of claim 1, wherein the integrated circuit further includes one or more electrical connectors, and wherein the gel covers a portion of a first one of the one or more electrical connectors.

7. The method of claim 6, wherein the first electrical connector extends upwards from a surface of the integrated circuit so as to prevent the gel from creeping along the connector when the gel is applied to the integrated circuit.

8. The method of claim 6, wherein the first electrical connector includes a variation in height along its length.

9. The method of claim 1, wherein the mold tool includes two or more portions, wherein the pin is a fixed part of a first one of the mold tool portions, wherein attaching includes closing the two or more portions of the molding tool, and wherein removing includes separating the first mold tool portion.

14. The method of claim 1, wherein the pin is a hollow tube, and wherein the method further comprises applying a reduced air pressure to an external end of the tube to maintain contact between the gel-covered assembly and the tube during encapsulation.

10. An encapsulated pressure sensitive integrated circuit assembly, formed by:

providing an integrated circuit, the integrated circuit including a pressure sensing element;

applying a quantity of gel to the integrated circuit such as to cover at least the pressure sensing element, thereby forming a gel-covered assembly;

inserting the gel-covered assembly into a cavity of a molding tool;

attaching a retractable pin to the gel-covered assembly;

introducing a plastic mold compound into the cavity so as to encapsulate the gel-covered assembly and at least a portion of the pin; and

removing the pin from the gel such as to leave a passageway in the plastic mold encapsulating the gel-covered assembly, thereby exposing the gel to the pressure of the atmosphere through the passageway, whereby the gel transfers the pressure to the pressure sensitive integrated circuit.

11. A method of encapsulating a pressure sensitive integrated circuit within a plastic molded package, comprising:

providing an integrated circuit on a carrier, the integrated circuit including a pressure sensing element;

positioning the carrier into a cavity of a molding tool;

applying a quantity of gel to the integrated circuit such as to cover at least the pressure sensing element, thereby forming a gel-covered assembly;

attaching a retractable pin to the gel-covered assembly;

introducing a plastic mold compound into the cavity so as to encapsulate the gel-covered assembly and at least a portion of the pin; and

removing the pin from the gel such as to leave a passageway in the plastic mold encapsulating the gel-covered assembly, thereby exposing the gel to the pressure of the atmosphere through the passageway, whereby the gel transfers the pressure to the pressure sensitive integrated circuit.

12. The method of claim 11, wherein the pin is a fixed part of the mold tool and wherein removing includes ejecting the encapsulated assembly from the mold tool such that the pin extracts from the encapsulated assembly.

13. The method of claim 11, wherein the mold tool includes two or more portions, wherein the pin is a fixed part of a first one of the mold tool portions, wherein attaching includes closing the two or more portions of the molding tool, and wherein removing includes separating the first mold tool portion.

15. The method of claim 11, wherein the gel covers the entire exposed portion of the integrated circuit on the carrier.

16. The method of claim 11, wherein the integrated circuit further includes one or more electrical connectors, and wherein the gel covers a portion of a first one of the one or more electrical connectors.

17. The method of claim 16, wherein the first electrical connector extends upwards from a surface of the integrated circuit so as to prevent the gel from creeping along the connector when the gel is applied to the integrated circuit.

18. The method of claim 16, wherein the first electrical connector includes a variation in height along its length.

19. An encapsulated pressure sensitive integrated circuit assembly, formed by:

providing an integrated circuit on a carrier, the integrated circuit including a pressure sensing element;

positioning the carrier into a cavity of a molding tool;

applying a quantity of gel to the integrated circuit such as to cover at least the pressure sensing element, thereby forming a gel-covered assembly;

attaching a retractable pin to the gel-covered assembly;

introducing a plastic mold compound into the cavity so as to encapsulate the gel-covered assembly and at least a portion of the pin; and

removing the pin from the gel such as to leave a passageway in the plastic mold encapsulating the gel-covered assembly, thereby exposing the gel to the pressure of the atmosphere through the passageway, whereby the gel transfers the pressure to the pressure sensitive integrated circuit.