Sensor element and sensor assembly provided with a casing

1. A sensor element comprising a sensitive sensor portion on an upper side of a substrate layer, wherein:

the upper side of the substrate layer is provided with a recess on a periphery of the sensitive sensor portion;

the sensitive sensor portion comprises a membrane;

a cavity is provided underneath the membrane in the substrate layer;

the cavity is closed off by a second substrate layer; and

a third substrate layer is provided on the bottom side of the second substrate layer, the recess extends up to the bottom side of the second substrate layer, and the second substrate layer is bonded to the third substrate layer in an area outside the recess.

2. The sensor element as claimed in claim 1 , wherein the recess extends over at least three quarters of the periphery of the sensitive sensor portion on the upper side.

3. The sensor element as claimed in claim 1 , wherein the recess is interrupted by at least one bridge part.

4. The sensor element as claimed in claim 3 , wherein the bridge part comprises two parts located opposite one another.

5. The sensor element as claimed in claim 3 , wherein the bridge part forms an angle with the recess.

6. The sensor element as claimed in claim 1 , wherein the recess has a depth in a direction at right angles to the upper side of the substrate layer which is greater than a thickness of the sensitive sensor portion.

7. A sensor assembly comprising:

at least one sensor element disposed on an upper side of a substrate layer; and

a casing surrounding the at least one sensor element,

wherein:

the casing is provided with an opening for an exposed sensor portion of the sensor element;

the casing is further provided with a recess on a periphery of the opening;

the sensor portion comprises a membrane;

a cavity is provided underneath the membrane in the substrate layer;

the cavity is closed off by a second substrate layer; and

a third substrate layer is provided on the bottom side of the second substrate layer, the recess extends up to the top side of the third substrate layer, and the second substrate layer is bonded to the third substrate layer in an area outside the recess.

8. The sensor assembly as claimed in claim 7 , wherein the recess extends over at least three quarters of the periphery of the opening.

9. The sensor assembly as claimed in claim 7 , wherein the third substrate layer is a lead frame.

10. The sensor assembly as claimed in claim 9 , wherein the recess is provided on both sides of the lead frame.

11. The sensor assembly as claimed in claim 7 , wherein the exposed sensor portion of the sensor element is covered with a protective material.