Pressure sensor device with a MEMS piezoresistive element attached to an in-circuit ceramic board
A pressure sensor device with a MEMS piezoresistive pressure sensing element attached to an in-circuit ceramic board comprises a monolithic ceramic circuit board formed by firing multiple layers of ceramic together. The bottom side of the circuit board has a cavity, which extends through layers of material from the ceramic circuit board is formed. A ceramic diaphragm, which is one of the layers, has a peripheral edge. The diaphragm's thickness enables the diaphragm bounded by the edge to deflect responsive to applied pressure. A MEMS piezoresistive pressure sensing element attached to the top side of the ceramic circuit board generates an output signal responsive to deflection of the ceramic diaphragm. A conduit carrying a pressurized fluid (liquid or gas) can be attached directly to the ceramic circuit board using a seal on the bottom of the ceramic circuit board, which surrounds the opening of the cavity through the bottom.
1. A MEMS piezoresistive pressure sensor device comprising:
a ceramic circuit board having a top side and a bottom side, the bottom side having a cavity, which extends through the ceramic circuit board to a ceramic diaphragm having a peripheral edge, the ceramic diaphragm having a thickness selected to enable the ceramic diaphragm to deflect responsive to an applied pressure;
a MEMS piezoresistive pressure sensing element attached to the top side of the ceramic diaphragm by a layer of glass frit, the MEMS piezoresistive pressure sensing element being substantially centered over the ceramic diaphragm peripheral edge, the MEMS piezoresistive pressure sensing element configured to generate an output signal responsive to deflection of the ceramic diaphragm.
2. The pressure sensor device of claim 1 , further comprising a metal seal coupled to the bottom side of the ceramic circuit board and surrounding the cavity where the cavity meets the bottom side.
3. The pressure sensor device of claim 1 , further comprising an integrated circuit attached to the top side of the ceramic circuit board and located outside the perimeter of the diaphragm.
4. The pressure sensor device of claim 1 , further comprising an integrated circuit attached to the top side of the ceramic circuit board and located whereby at least part of the integrated circuit is within the perimeter of the diaphragm.
5. The pressure sensor device of claim 1 , further comprising an adhesive between the MEMS piezoresistive pressure element and the top side of the ceramic circuit board.
6. The pressure sensor device of claim 1 , wherein the ceramic circuit board further comprises at least one capacitor, which is internal to the ceramic circuit board, between the top and bottom surfaces, the at least one capacitor being electrically coupled to the integrated circuit.
7. The pressure sensor device of claim 1 , further comprising at least one capacitor attached to the top surface, the at least one capacitor being electrically coupled to the integrated circuit.
8. The pressure sensor device of claim 1 , wherein the ceramic circuit board comprises a monolithic ceramic layer, formed from a first plurality of layers of low-temperature co-fired ceramics.
9. The pressure sensor device of claim 1 , wherein the ceramic circuit board comprises a monolithic ceramic layer, formed from a first plurality of layers of high-temperature co-fired ceramics.
10. The pressure sensor device of claim 1 , further comprising a plurality of bond pads on the top side of the ceramic circuit board.
11. The pressure sensor device of claim 1 , further comprising a conduit, configured to carry a pressurized fluid, the conduit having a port, which extends into the ceramic cavity and applies a pressurized fluid against the diaphragm.
12. The pressure sensor device of claim 11 , wherein the conduit is metal.
13. The pressure sensor device of claim 11 , further comprising an adhesive seal between the port and the cavity.
14. The pressure sensor device of claim 13 , wherein the adhesive seal is a solder.
15. The pressure sensor device of claim 1 , wherein the ceramic diaphragm is circular.
16. The pressure sensor device of claim 1 , wherein the ceramic diaphragm is rectangular.