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Heater structure for a sensor device

IP.com Disclosure Number: IPCOM000237967D
Publication Date: 2014-Jul-23
Document File: 14 page(s) / 2M

Publishing Venue

The IP.com Prior Art Database

Abstract

The sensor device comprises a hotplate on a membrane . The hotplate is heated by a N-fold rotationally symmetric heater structure having N > 1 heater elements of identical design. Each heater element comprises an inner section, an intermediate section and an outer section arranged in series, with the inner section having a larger electrical cross section than the outer section. This design allows to heat the hotplate to a homogeneous temperature at moderate supply voltages.

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Heater structure for a sensor device

Abstract

          The sensor device comprises a hotplate (4) on a membrane (3). The hotplate
(4) is heated by a N-fold rotationally symmetric heater structure (6a, 6b, 7a, 7b) having N > 1 heater elements (6a, 6b) of identical design. Each heater element (6a, 6b) comprises an inner section (16), an intermediate section (17) and an outer section (15) arranged in series, with the inner section (16) having a larger electrical cross section than the outer section (15). This design allows to heat the hotplate (4) to a homogeneous temperature at moderate supply voltages.

Technical Field

          The invention relates to a sensor device comprising a substrate with a hotplate and a heater structure arranged in the hotplate.

Background Art

          Various types of sensors require elevated temperatures for operation. For example, gas sensors with metal oxide sensing structures best operate at temperatures in a range of at least 100 °C or higher, depending on the oxide to be used and on the gas species to be measured. A gas sensor of this type is described in EP 2278308 or WO 2014/012948.

          In order to keep the temperature distribution on the hotplate homogeneous, the heating structure of these devices is a "double spiral" that has wider leads in the central region of the hotplate than in the peripheral, outer region of the hotplate.

Disclosure of the Invention

          The problem to be solved by the present invention is to provide a sensor device of the type mentioned above that has improved versatility.

          This problem is solved by the sensor device of this disclosure. This device comprises:

          - A substrate having a hotplate: The hotplate is the heated area of the device and it has an inner region and an outer region, with the outer region surrounding the inner region.

          - A heater structure arranged in said hotplate: The heater structure is structured and adapted for heating the hotplate.


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          - A driver for generating a heating current through said heater structure: This driver is typically an electrical circuit adapted to generate an electrical current in the heater structure. The driver can be integrated on the substrate or it can be implemented as an external component.

          - A sensing structure arranged on said heater structure: This is the sensitive structure of the sensor device, which has to be heated to an elevated temperature.

          The heater structure comprises a number N > 1 of heater elements, with each of said heater elements having an outer section and an inner section. The outer and inner sections of each heater element are arranged electrically in series. The driver is structured and adapted to heat the heater elements with parallel currents, i.e. with separate currents branched from the same voltage source. In a simple embodiment, this can e.g. be achieved by statically wiring the heater elements to be electrically parallel to each other.

          Further, the maximum electrical cross section of the outer section of each heater eleme...