Pressure sensor

Details Pressure sensor Pressure sensor

1999-03-03

2000-05-16

Oen, William

Measuring and testing

Fluid pressure gauge

Diaphragm

73721, G01L 906, G01L 706

Patent

active

060620889

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a pressure sensor.


BACKGROUND INFORMATION

German Patent 40 28 376 describes a conventional pressure sensor, in which a strain element (i.e., expansion measuring element) is applied on a membrane. The strain element is produced on a glass plate using thin-layer technology.


SUMMARY OF THE INVENTION

In contrast, the pressure sensor according to the present invention has the advantage that, by using silicon bridge elements, particularly inexpensive pressure sensors can be produced. Individual bridge elements can be manufactured very cost-effectively by producing a multiplicity of bridge elements simultaneously from one silicon wafer. In this context, the mounted piezoresistive resistor elements exhibit high sensitivity.
By setting the membrane in a rigid frame, as one piece, a pressure sensor is produced in which by simply varying the membrane thickness, sensors can be manufactured for various pressure ranges. In this context, to achieve high sensitivity, the strain element extends from the frame onto the membrane. The piezoelectric resistor elements are preferably arranged in areas of great mechanical deformation, in order to assure a high measured signal. The silicon bridge element can be arranged either directly on the metal membrane and the frame or via a substrate. By using the substrate, the silicon bridge element is easier to handle during the manufacturing process. In this context, provision can be made for a joining area on the frame and on the membrane. To improve the temperature sensitivity of the sensor signal, provision can be made that the joining area not be fixedly joined to the membrane, but rather rest on it. The attachment areas are preferably joined to the membrane or to the frame by gluing or soldering. Membranes and frames can advantageously be manufactured by a metal machining process. To make possible a particularly simple assembly of the pressure sensor, the frame can also be designed as a screw-in part which is provided with a thread.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first exemplary embodiment of a pressure sensor according to the present invention.
FIG. 2 shows a top view of a silicon bridge element according to the present invention.
FIG. 3 shows another exemplary embodiment of the pressure sensor according to the present invention.
FIG. 4 shows yet another exemplary embodiment of the pressure sensor according to the present invention.


DETAILED DESCRIPTION

FIG. 1 shows a first exemplary embodiment of the pressure sensor according to the invention having a metallic membrane 1, which is set (i.e., stretched on) in a rigid frame 3. Arranged on membrane 1 is a strain element, which is configured as a silicon bridge element 2. Silicon bridge element 2 is attached; on the one hand, to membrane 1, and on the other hand, to rigid frame 3, in each case via a joining area 10. Furthermore, provision is made on rigid frame 3 for a hybrid circuit 4, by means of which the signals of silicon bridge element 2 are evaluated. For this purpose, silicon bridge element 2 has piezoresistive resistors 11, whose resistance changes as a function of the stress states in the silicon material. The electrical connection between silicon bridge element 2 and hybrid circuit 4 is brought about via a bonding wire 5. Moreover, provision can be made for further bonding wires or other electrical conducting elements, by means of which the signals of hybrid circuit 4 can be routed to beyond the pressure sensor. Frame 3 additionally has a thread 6, by means of which frame 3 can be fixedly mounted.
Via pressure feed 7, the lower side of membrane 1 is acted upon by a pressure to be measured. The upper side of the membrane is acted upon by the normal pressure of the environment or by a reference pressure, so that the absolute pressure or a differential pressure is measured. Due to the pressure difference between pressure feed 7 and the upper side of the membrane, a deformation of the membrane occurs, which causes a corresponding deformation

REFERENCES:
patent: 4675643 (1987-06-01), Tanner et al.

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