Measuring and testing – Speed – velocity – or acceleration
Reexamination Certificate
2002-08-08
2003-11-11
Moller, Richard A. (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
C073S514320, C073S514350, C073S700000, C073S862000
Reexamination Certificate
active
06644117
ABSTRACT:
FIELD OF THE INVENTION
The present invention refers to microstructure technology and especially to electromechanical components.
BACKGROUND OF THE INVENTION AND PRIOR ART
Electromechanical components are components which electrically detect or electrically cause a mechanical effect. Examples of electromechanical components are sensors for linear accelerations, rotary speed sensors, force sensors, pressure sensors and also microvalves or micropumps.
Acceleration sensors, for example, i.e. sensors for detecting a linear acceleration, or rotary speed sensors for detecting an angular acceleration, normally include a movable mass which is connected to a fixed frame through at least one spring beam. When an acceleration sensor is subjected to an acceleration, the spring beam will deform elastically and the mass will be deflected. This deflection can then be detected making use of a large number of known methods, such a capacitive, inductive, optical etc. methods.
Microvalves, however, normally have a movable, elastic structure which, in response to the application of a suitable electric signal, will reduce or enlarge the size of a flow path for a fluid, i.e. which will cause as a mechanical effect a limitation of the amount of fluid flowing through.
Micropumps are, however, normally provided with a diaphragm which is elastic or elastically suspended so as to change a volume. A micropump will normally also be provided with valves so as to achieve via said change in volume a conveyance of a defined amount of fluid. It follows that the mechanical effect in the case of micropumps is transport and dosage of a fluid.
Pressure sensors or force sensors may also be provided with an elastically deformable diaphragm, which is elastically deformed, i.e. “deflected”, to a certain degree in response to a specific pressure; just as in the case of the acceleration sensor, this deflection can be detected in various ways so as to obtain an electric signal indicative of the pressure applied. All the above-mentioned electromechanical components comprise an active part, which is elastically deformed by the outer mechanical effect or the elastic deformation of which leads to the mechanical effect.
Such electromechanical components can comprise an integrated means for converting the mechanical effect into an electric effect or for converting an electric effect into a mechanical effect. Only by way of example, the known electrode structure, e.g. in the form of fingers or in the form of a diaphragm, should here be mentioned; this electrode structure comprises a first group of electrodes connected to a movable part, and a second group of electrodes connected to a fixed part relative to which the movable part moves. The two groups of electrodes are arranged in an interleaving mode of arrangement in such a way that a deflection of the movable part relative to the fixed part results in a change in the distances between the electrodes, said change leading to a change in the capacitance of the electrode arrangement. This change in capacitance is e.g. a function of the acceleration acting on the movable part. In the case of a pressure sensor, the mechanical effect can be caused e.g. by a change in the distance between two planar electrodes in the sense of a plate capacitor. This change in capacitance can be measured making use of an alternating voltage.
Electromechanical components of this type are normally produced from silicon material in miniaturized form making use of the silicon-based technology which proved to be efficient in wafer processing. Silicon-based technology permits mass production which resulted in a wide range of use of e.g. capacitive acceleration sensors which have been produced using silicon-based technology; such acceleration sensors are in particular used in the field of automotive engineering, where acceleration sensors for airbag systems should especially be mentioned.
In the case of such silicon sensors, the inertial mass is suspended from thin springs and provided with electrode structures defining together with fixed similar electrode structures a capacitor whose capacitance changes in the case of acceleration, whereby the acceleration can be detected electronically. Silicon acceleration sensors are produced e.g. in polysilicon surface mechanics by the firm of Bosch in Reutlingen. In the case of this technology a wafer with sensor chips is produced and subsequently connected, e.g. by means of the anodic bonding method, to a cover wafer which has been prefabricated in a suitable manner again by means of silicon-based micromechanical techniques, so that the sensitive micromechanically patterned silicon sensor structures will be protected. Subsequently, the composite wafer with the encapsulated sensor chips is diced. The individual sensor chips are then installed together with an electronic chip in a suitable housing making use of standard methods in the field of microelectronical technology so as to obtain the finished sensor system. The sensor systems can then be further processed like purely electronic components.
Advantages of these silicon acceleration sensors are the small physical size of the sensor and, consequently, of the chip, the fact that they can be produced in batch production processes as well as the high long-term stability and the accuracy in view of the advantageous properties of the silicon material used.
One disadvantage of such systems is the fact that, due to the very small dimensions of their sensor structures, when e.g. electrode structures are intended to be used as groups of fingers, and in view of the so-called sticking effect, it is necessary to protect such sensors against particles and moisture by a virtually hermetic seal. Another disadvantage is that, in spite of batch production and the build-up technique used in the field of electronics technology, the manufacturing process in its entirety is still very expensive, since, in addition to the electronic chip, also two silicon wafers must be produced, connected and diced by micromechanical methods.
Although silicon-based technology has gained great acceptance, which resulted in more moderate prices for the whole clean room systems and which has already led to a high degree of automation, it should still be pointed out that a complete clean room as well as adequately trained staff are necessary for wafer processing. It follows that a decisive cost factor is not the material itself, but the production outlay, which is essentially determined by the systems required and the labour costs incurred.
DE 44 02 119 A1 discloses a micro-diaphragm pump, the diaphragm being produced from titanium and the valves from polyimide. Alternatively, the diaphragm may consist of polyimide having a heating coil applied thereto .
U.S. Pat. No. 5,836,750 discloses an electrostatically driven mesopump comprising a plurality of unit cells. A pump diaphragm can be produced from metal-coated polymers, from metal or from a conductive flexible elastic polymer.
DE 197 20 482 A1 discloses a micro-diaphragm pump having a diaphragm which consists of PC or PFA. A piezo-actor can be provided on a brass sheet which is, in turn, applied to the pump diaphragm.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide less expensive electromechanical components and methods for producing the same, which still have mechanical and electrical properties comparable to those of silicon components.
In accordance with a first aspect of the present invention, this object is achieved by an electromechanical component comprising: a polymeric body including a mechanically active part and a frame; and a metal layer which covers the mechanically active part at least partially so as to mechanically stabilize the same, said mechanically active part including a spring beamconnecting the frame to a mass which moves when said spring beam bends; and said metal layer encompassing the spring beam substantially completely, with the exception of the locations where said spring beam is connected to the frame and the mass, so as to mechanically reinforce
Giousouf Metin
Kueck Heinz
Glenn Michael A.
Glenn Patent Group
Hahn-Schickard-Gesellschaft fuer Angewandte Forschung E.V.
Moller Richard A.
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