Mass flow sensor having a measuring element arranged on a membrane retained on a monocrystalline silicon wafer
AssigneeRobert Bosch GmbH
InventorsEckart Reihlen, Jiri Marek, Frank Bantien, Guenther Findler, Michael Offenberg, Josef Kleinhans, Uwe Konzelmann, Botho Ziegenbein
Life of this patent
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Abstract
A mass flow sensor includes a measuring element arranged on a membrane that is clamped in a frame. The sensor is formed by introducing a recess into a silicon wafer. Through the application of a recess having perpendicular walls, the thickness of the frame can be reduced, thus allowing the required surface area of the wafer to also be reduced.
Claims3
A mass flow sensor for measurinq the flow of a medium having a first temperature, the sensor comprising:
- a membrane;
- a measuring element arranged on the membrane, the measurinq element being at a second temperature higher than the first temperature, the measuring element measuring the flow of the medium based upon a transfer of heat from the measuring element to the medium;
- and
- a frame for retaining the membrane, the frame including a monocrystalline silicon wafer having a recess with side walls that are perpendicular to a bottom surface of the silicon wafer,
- wherein:
- the bottom surface of the silicon wafer has a 100 orientation;
- and
- the recess is in a rear portion of the silicon wafer, and has edges which form a generally hexagonal-shaped opening on the bottom surface of the silicon wafer, with at least one of the edges lying on a plane with a 111 orientation.
A mass flow sensor for measurinq the flow of a medium having a first temperature, the sensor comprising:
- a membrane;
- a measuring element arranged on the membrane, the measuring element being at a second temperature higher than the first temperature, the measuring element measuring the flow of the medium based upon a transfer of heat from the measuring element to the medium;
- and
- a frame for retaining the membrane, the frame including a monocrystalline silicon wafer having a recess with side walls that are perpendicular to a bottom surface of the silicon wafer,
- wherein:
- the bottom surface of the silicon wafer has a 110 orientation;
- and
- the recess has first, second, third and fourth edges which form a parallelogram-shaded opening on the bottom surface of the silicon wafer and which lie on planes with a 111 orientation perpendicular to the bottom surface of the silicon wafer, with the first and second edges forming an angle of approximately 109.5.degree., the second and third edges forming an angle of approximately 70.5.degree., and the third and fourth edges forming an angle of approximately 109.5.degree..
Dependencies are inferred from the claim text.