Robert Boschgmbh

Heiko Gruner

Kurt Burger

Erich Zabler

Heinz Friedrich

Karl-Otto Linn

Werner Herden

Franz Rieger

Dieter Handtmann

Hans Neu

Werner Pfander

Georg Zimmermann

Dietmar Schnepf

Hans-Martin Hochenberger

Rainer Schussler

Claus-Dietrich Pilch

Hans-Joachim Seidel

Friedrich Vogel

Klaus Reindl

A thin-film strain gauge and a method for producing it are proposed; the strain gauge is advantageously capable of integration into a thin-film circuit. The strain gauge comprises an elastically deformable spring element in combination with at least one elongation-sensitive resistor. The resistor disposition (R1-R4), the low-impedance connections (L11-L42) between the various resistance regions and the associated connection tracks (L5-L8) are applied in a vacuum process, preferably by cathode sputtering. The low-impedance connections (L11-L42) and the connection tracks (L5-L8) are of material which, although different from the material making up the actual resistance region, still has approximately the same temperature coefficient of resistance, so as to preclude errors caused by temperature.

Method of making a thin-film strain gauge

Thin-film strain gauge

A thin tantalum foil is sufficiently stable mechanically for supporting a bridge of thin film resistors with a glass insulating layer interposed between them and the foil, while a fluid medium flows past the resistors for measurement of its temperature or for thermal measurement of the rate of flow of the mass of the medium. The resistors form a bridge one half of which is heated to maintain a predetermined temperature for measurement of the rate of flow by means of the heating current, while the other half provides a reference for the regulation of the heating current. A slot in the metal foil between the halves of the bridge provides thermal decoupling between the heated and unheated parts of the bridge.

Temperature sensor for determining mass transfer rate and/or temperature

To form a temperature sensor, for example suitable in an automotive vehicle, to determine ambient temperatures, or to provide a temperature compensated thin-film circuit, for example for incorporation with an oscillator circuit, two stable thin-film layers are applied to a non-conductive substrate, the layers being capable of being etched. The overall temperature coefficient of resistance can be matched to a predetermined value by selective interconnection of at least two thin-film resistance elements formed by the thin films, of which one thin film resistance element for example comprises a nickel layer over a tantalum base, with a predetermined temperature coefficient of resistance, the other resistance element merely being the tantalum layer with essentially zero temperature coefficient of resistance, the overall temperature coefficient of resistance of the combination being determined by adjustment of the relative resistance values after measurement of the temperature coefficient of resistance of the nickel-tantalum layer to determine its actual temperature coefficient so that, in spite of tolerances in the manufacture of the thin films, interchangeable elements of highly accurate overall resistance and temperature coefficient of resistance values can be obtained.

Controlled temperature coefficient thin-film circuit element

To provide for rapid temperature response to changes in temperature of an air flow past the sensing end portion of a resistance sensing track (13) on a ceramic substrate (12), the resistance sensing track is applied in a meander of a predetermined length, which is spaced from contact terminal points (14) to the meander by at least the longitudinal extent (19) of the meander; two covering layers (20, 21) are provided, one (20) being thin and covering the meander and adjacent connecting tracks (15, 16), and the other (21) being thick and sturdy and retaining the plate (12) in position in a housing (1, 2), overlapping the first covering (20), but being spaced therefrom by at least half the longitudinal extent (19) of the meander.

Fast-response temperature sensor

A meander-shaped layer of nickel is deposited by evaporation on a ceramic wafer over an intermediate layer of tantalum serving to improve adhesion, and covered by a protective coating of silicon or epoxy resin is used as a temperature sensor in the intake pipe of a supercharged internal combustion engine. The low mass of the sensor element thus provided enables the resistance of the nickel path to follow rapidly, by its variation, the variations of temperature of the intake air. The sensor has a casing made up of two parts, the lower one of which has two connection prongs molded into it, the ends of which are flattened into tabs that are soldered to contact areas of the ceramic wafer. The upper casing portion has a cavity for the ceramic wafer, the lower part of which is filled with a potting compound to protect the solder joints. The width of the nickel paths that provide the temperature sensitive resistance is about 50 .mu.m and the thickness is from 0.2 to 1 .mu.m and the resistance may be typically 1000 ohms.

Rapid acting gas temperature sensor

To improve the adhesion of a nickel layer to a valve metal layer in a thin film electronic circuit, a boundary layer is created between the valve metal and the nickel layer. The boundary layer is created by oxidizing the valve metal surface and applying the nickel layer by cathode sputtering with sufficiently high energy to cause nickel-ion migration into the valve metal oxide layer. The so-formed boundary layer improves the mechanical adhesion of the nickel layer to the valve metal layer and also prevents penetration of solder to the valve metal layer since the boundary layer acts as a diffusion barrier.

Thin film circuit

A carrier strip of polyimide resin sheet material carries on one face an etched pattern of metallization comprising temperature-independent resistors formed of an underlying metallization layer of tantalum base, temperature-dependent resistors in which the effect of the upper layer of metallization, of a nickel base, is predominant, and conductive paths provided by broader strips of the nickel base material. A cover layer of the same heat-resistant resin sheet material is sealed and bonded to the carrier strip wherever a metallization layer does not intervene, taking care to leave open certain contact areas for the attachment of connecting leads. A holder structure holds the strips at each end and provides clear space for attaching connecting leads as well. The holder structure is designed to allow the flow of medium to pass in good thermo contact with the portion of the device enclosing the resistance elements.

Probe for measuring flow rate and/or temperature of a flowing medium

An apparatus is proposed for measuring the mass of a fluid medium such as the mass of air induced by internal combustion engines which has at least one temperature-dependent measuring resistor film disposed in the flow of the medium, whose temperature and/or resistance is regulated in accordance with the mass of the medium and wherein the manipulated variable is a measure for the mass of the medium. The temperature-dependent measuring resistor film is disposed on a carrier separated therefrom by an insulating film and a temperature-dependent heating resistor film. The temperature of the heating resistor film is regulated to approximately the same temperature as the temperature-dependent measuring resistor film so that a heat flow between the temperature-dependent measuring resistor and the carrier is prevented. As a result, the response speed of the apparatus to changes in the flow rate of the medium is substantially improved as is the precision of measurement.

Apparatus for measuring the mass of a fluid medium

To provide a pre-heated sensor which is capable of heating the sensing element exposed to gases to a temperature of above 400.degree. C. and preferably above 500.degree. C., at which temperature the sensor will be essentially immune to lead content in the gases, an elongated heating rod is placed within a sensor structure in which a solid electrolyte tube is held in position by a first stressed compression spring, the heating rod being formed with a radially projecting flange against which a second compression spring bears, concentrically located within the first, the heating rod itself comprising a long ceramic tube, preferably formed with two longitudinal bores to accept connecting wires to a thermocouple positioned at the end of the tube to sense the temperature of the sensing tube, surrounded by a first metallic tube forming an electrical connection to one terminal of a spiral heating wire which is wrapped around a fiberglass sleeve slipped over the metallic tube, connected to a second metallic tube outside of the fiberglass sleeve which, in turn, has yet another fiberglass sleeve slipped thereover, which is split in the region of the flange, to provide a sensing element in which all components are concentrically located within each other, and held in position by an end cap and in place by compression springs to permit assembly from the region of the end cap which, upon completion of the assembly, is secured in position, and compression-stressing the springs, thereby providing reliable connection and shock and vibration resistant seating of all components while permitting simple assembly under mass production conditions.

Internally, electrically heated electrochemical sensing element

A pure aluminum outer layer is provided to facilitate bonding with aluminum bonding wires having a diameter of 50 .mu.m or greater without formation of troublesome slivers upon bonding. Beneath that a copper-bearing aluminum layer with 1 to 4% copper content is provided. A third layer beneath the copper-bearing layer containing up to 1% silicon can be added below the copper-bearing layer to promote adhesion at contact window edges.

Growing community of inventors

Gerlingen, Germany

Heiko Gruner