Stacked or unstacked MEMS pressure sensor with through-hole cap and plurality of chip capacitors

Patent metadata

Field	Value
Publication number	US-10247629-B2
Application number	US-201715499639-A
Country	US
Kind code	B2
Filing date	Apr 27, 2017
Priority date	Apr 27, 2017
Publication date	Apr 2, 2019
Grant date	Apr 2, 2019

Abstract

A MEMS pressure sensing element and integrated circuit (IC) are mounted on a circuit board. The sensing element and IC can be either stacked or unstacked. Bond wires connect the IC to the circuit board. Other bond wires connect the sensing element to the IC. A cap covers the sensing element and IC. The cap is attached to the circuit board and has a small hole in it, through which viscous gel is inserted. The gel encapsulates the MEMS sensing element, IC and bond wires in the cap. The hole also allows pressurized fluid to enter the cap and exert force on the MEMS pressure sensing element after encapsulation in the gel. Chip capacitors can also be mounted on the circuit board, outside the cap. Electrical signals are generated, which represent pressure applied to the MEMS pressure sensing element through the hole and gel.

First claim

What is claimed is:

1. A pressure sensor comprising:
a circuit board having upper and lower surfaces and a plurality of vias for electrical connection;
an integrated circuit having upper and lower surfaces, the lower surface of the integrated circuit being attached to the circuit board's upper surface;
a first plurality of bond wires, electrically connecting the integrated circuit to the circuit board;
a MEMS pressure sensing element having a top side and a back side, the MEMS pressure sensing element's top side having a diaphragm;
a second plurality of bond wires electrically connecting the MEMS pressure sensing element to the integrated circuit;
a cap attached to the upper surface of the circuit board and enclosing the integrated circuit, the MEMS pressure sensing element and the bond wires therein, the cap having a top surface with an orifice;
a plurality of chip capacitors mounted on the circuit board outside of the cap; and
a gel inside the cap and substantially covering: the integrated circuit, the MEMS pressure sensing element, the first plurality and the second plurality of bond wires;
wherein pressure outside the cap is applied to the diaphragm via the gel through the orifice.

2. The pressure sensor of claim 1 , wherein the MEMS pressure sensing element has a vacuum cavity and wherein the MEMS pressure sensing element backside is attached to the upper surface of the integrated circuit thereby forming a stacked absolute pressure sensor.

3. The pressure sensor of claim 2 , further comprising:
a first layer of adhesive located between the integrated circuit and the circuit board's upper surface; and
a second layer of adhesive located between the integrated circuit's upper surface and the backside of the MEMS pressure sensing element.

4. The pressure sensor of claim 1 , wherein the MEMS pressure sensing element has a vacuum cavity below the diaphragm and wherein the MEMS pressure sensing element backside is attached to the upper surface of the circuit board and adjacent to the integrated circuit thereby forming an un-stacked absolute pressure sensor.

5. The pressure sensor of claim 4 , further comprising:
a first layer of adhesive located between the integrated circuit and the circuit board's upper surface; and
a second layer of adhesive located between the circuit board's upper surface and the backside of the MEMS pressure sensing element.

6. The pressure sensor of claim 1 , wherein the cap comprises a hollow cylinder having first and second opposing ends, the first end being open, the second end being closed by a substantially round flat plate having first and second opposing surfaces and a hole that extends through the plate.

7. The pressure sensor of claim 1 , wherein the cap is attached to the upper surface of the circuit board by at least one of epoxy and solder.

8. The pressure sensor of claim 1 , wherein the cap is made of metal.

9. The pressure sensor of claim 1 , wherein the cap is made of ceramic.

10. The pressure sensor of claim 1 , wherein the cap is made of silicon.

11. The pressure sensor of claim 1 , wherein the cap is made of glass.

12. The pressure sensor of claim 1 , further comprising:
an injection-molded housing having a pocket that accommodates the circuit board;
a plurality of angled pins embedded in the housing with angled segments extending through the vias of the circuit board and soldered to the circuit board for electrical connections;
wherein the cap is partially embedded in a layer of epoxy, the epoxy being used to constrain movement of the circuit board and protect the chip capacitors and the solders.

13. The pressure sensor of claim 1 , further comprising:
pre-molded angled pins having an angled segments extending through the circuit board vias and soldered to the circuit board for electrical connections;
a plastic overmold encapsulating the circuit board, the chip capacitors, portion of the angled pins, and the cap;
wherein the cap is partially embedded in the plastic overmold.

14. The pressure sensor of claim 13 , wherein the cap and the cap's top surface, but not the orifice, are embedded in the plastic overmold.

15. The pressure sensor of claim 1 , wherein the integrated circuit has a hole, the circuit board has a hole and wherein the MEMS pressure sensing element has a hole in the backside of the MEMS pressure sensing element that extends upwardly through the MEMS pressure sensing element to the diaphragm, the MEMS pressure sensing element being stacked on top of the integrated circuit with the backside of the MEMS pressure sensing element facing the upper surface of the integrated circuit, the holes in the integrated circuit, circuit board and MEMS pressure sensing element being aligned with each other to form a stacked differential pressure sensor, such that the diaphragm in the MEMS pressure sensing element deflects responsive to a first pressure applied through the orifice in the cap and a second pressure applied through the holes in the circuit board, integrated circuit and MEMS pressure sensing element.

16. The pressure sensor of claim 15 , further comprising:
a first layer of adhesive located between the integrated circuit and the circuit board's upper surface; and
a second layer of adhesive located between the integrated circuit's upper surface and the backside of the MEMS pressure sensing element.

17. The pressure sensor of claim 1 , wherein the circuit board further comprises a hole adjacent to the integrated circuit and which extends through the upper and lower surfaces of the circuit board, wherein the MEMS pressure sensing element is a differential pressure sensing element further comprising a hole in its back side that extends upwardly to the diaphragm, the hole in the back side of the MEMS pressure sensing element being aligned with the hole through the upper and lower surfaces of the circuit board to form an un-stacked differential pressure sensor, wherein
a first pressure is applied to the top side of the diaphragm through the orifice in the cap and through the gel and, a second pressure is applied to the back side of the diaphragm through the hole in the circuit board and the hole in the back side of the MEMS pressure sensing element.

18. The pressure sensor of claim 17 , further comprising:
a first layer of adhesive located between the circuit board's upper surface and the integrated circuit's lower surface; and
a second layer of adhesive located between the circuit board's upper surface and the MEMS pressure sensing element's back side.

19. A method of forming a plurality of MEMS pressure sensors, the method comprising:
attaching a plurality of chip capacitors on a top side of a circuit board outside of locations of caps, which will be affixed thereafter;
attaching a plurality of integrated circuits on the top side of the circuit board, each integrated circuit having a top side and a bottom side, the bottom side of each integrated circuit being attached to the top side of the circuit board;
attaching each of a plurality of MEMS pressure sensing elements on the top side of at least one of the corresponding integrated circuit and the circuit board, each MEMS pressure sensing element having a diaphragm on a top side;
connecting each MEMS pressure sensing element to the integrated circuit with a first plurality of bond wires;
connecting each integrated circuit to corresponding metal traces on the circuit board with a second plurality of bond wires;
affixing a cap over each integrated circuit and MEMS pressure sensing element, the cap compris

Assignees

• Continental automotive systems inc

Inventors

• Chiou Jen-Huang Albert

Classifications

• H10W90/753

  between laterally-adjacent chips · CPC title

• H10W90/752

  between stacked chips · CPC title

• H10W90/732

  between stacked chips · CPC title

• H10W72/884

  Die-attach connectors and bond wires · CPC title

• B81B2207/012

  the micromechanical device and the control or processing electronics being separate parts in the same package · CPC title