# US 5,705,745 A · Mass flow sensor

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- Number: US 5,705,745 A
- Document ID: US5705745A
- Status: Granted
- Kind: A
- Application number: 08/700,745
- Filed: 1996-07-29
- Granted: 1998-01-06
- Earliest claimed: 1995-07-29
- Assignees: Robert Bosch GmbH
- Inventors: Christoph Treutler; Detlef Gruen; Horst Muenzel; Helmut Baumann; Steffen Schmidt; Andreas Lock
- Web page: https://patentgrep.com/patent/US5705745A

## CPC

- G01F 1/6845: {Micromachined devices}
- G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME

## Abstract

In a mass flow sensor having a frame of monocrystalline silicon and a membrane fixed therein, a heating element and, if indicated, temperature-measuring elements are provided on the membrane. A heat-conducting element, which extends from the membrane across the frame, is provided in the edge area of the membrane. The heating element, the heat-conducting element and, if indicated, temperature-measuring elements are patterned out of a single metal layer.

## Claims

### Claim 1

A mass flow sensor comprising:
a frame composed at least partially of monocrystalline silicon;
a membrane fixed in the frame, the membrane having an edge;
a metal layer;
a heating element patterned out of the metal layer, the heating element being arranged on the membrane;
at least one temperature-measuring element patterned out of the metal layer; and
at least one heat-conducting element patterned out of the metal layer, the heat-conducting element being arranged at the edge of the membrane, the heat-conducting element extending from the membrane across the frame, the heat-conducting element conducting heat from the heating element.

### Claim 2 (depends on 1)

The mass flow sensor according to claim 1, wherein the membrane includes a membrane layer, the membrane layer extending across a top side of the frame.

### Claim 3 (depends on 2)

The mass flow sensor according to claim 2, wherein, in a vicinity of the frame, the membrane layer has an opening, the heat-conducting element being in direct contact with the silicon of the frame through the opening.

### Claim 4 (depends on 1)

The mass flow sensor according to claim 1, wherein the metal layer includes platinum.

### Claim 5 (depends on 1)

The mass flow sensor according to claim 1, wherein the membrane includes at least one of silicon oxide and silicon nitride.

### Claim 6 (depends on 1)

The mass flow sensor according to claim 1, further comprising an additional metal layer arranged on the heat-conducting element.

### Claim 7 (depends on 6)

The mass flow sensor according to claim 6, further comprising a dielectric passivation layer arranged on the heat-conducting element, below the additional metal layer.

### Claim 8 (depends on 1)

The mass flow sensor according to claim 1, further comprising an additional metal layer arranged underneath the heat-conducting element.

### Claim 9 (depends on 1)

The mass flow sensor according to claim 1, wherein the temperature-measuring element is arranged on the membrane on two sides of the heating element.

### Claim 10 (depends on 1)

The mass flow sensor according to claim 1, wherein the heat-conducting element has a first thermal conductivity greater than a second thermal conductivity of the membrane.