Electrical resistors – Resistance value responsive to a condition – Fluid- or gas pressure-actuated
Reexamination Certificate
1999-08-25
2001-03-13
Easthom, Karl D. (Department: 2832)
Electrical resistors
Resistance value responsive to a condition
Fluid- or gas pressure-actuated
C338S036000, C257S417000, C073S721000, C073S727000
Reexamination Certificate
active
06201467
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a pressure sensor component having a chip carrier with a substantially planar chip carrier surface and a semiconductor chip on the chip carrier surface. The semiconductor chip has an integrated a pressure sensor with a pressure-detecting area exposed to the pressure to be measured. The device has a component encapsulation made of an electrically insulating material enclosing the semiconductor chip and/or the chip carrier at least in regions. The invention furthermore relates to a method for producing such a pressure sensor component.
In order to measure pressures, the medium to be measured must be brought up to the sensor, or the pressure prevailing in the medium must be transmitted to the sensor. On the other hand, the application of a semiconductor pressure sensor in the final use requires that the sensor chip be provided with a protective encapsulation by being covered with a suitable material, normally plastic. What is known in this case is the application of the semiconductor chip, usually resting on silicon as the base material, in a housing, for example DIP housing (Dual Inline Package housing), SMD housing (Surface Mounted Design housing), or else in special designs, the housing subsequently being mounted on a printed circuit board.
In one prior art embodiment, the pressure coupling is effected by means of a diaphragm which covers and thus protects the sensitive sensor, is made of metal or else plastic and can also be embodied as a separate additional structural part. Problems frequently arise in that case because pressure is coupled in only insufficiently through the housing as far as the sensor chip with the sensor simultaneously being protected. What is required, in general, is a tight connection between the medium to be measured and the sensor, which connection is simple to produce, in order to avoid extraneous air flowing in which could falsify the pressure measurement. On the other hand, in many cases there is, moreover, a requirement to separate the medium to be measured from the metallic constituents of the sensor and also from the semiconductor chip, in order to avoid the risk of corrosion or destructive influence by the medium on the sensitive constituents of the sensor. Other embodiments of known pressure sensor components provide an open housing in which the protection of the sensor chip against environmental influences is regarded only as a problem of secondary importance, and the sensor chip is not protected. Such designs are generally suitable only for non-aggressive media.
European published patent application EP 0 436 158 A2 describes a solid-state pressure sensor comprising a pressure space which is open toward two opposite sides and also comprises a distortion sensor element formed by a silicon diaphragm. Each partial space of the pressure space thereby forms a hermetically sealed, separate space with the connection. The arrangement is furthermore encapsulated by a housing which, with O-rings, seals the connection flanges penetrating through the housing. The measurement principle is in this case based on the flexure of the silicon diaphragm which is picked up by sensor elements applied on the diaphragm.
European published patent application EP A 0 690 297 A1 describes a housing for electronic components and the production thereof, in which a pressure inlet opening is formed in the upper region of the encapsulation housing. The opening forms a connection piece in a chimney-shaped manner and is designed to be integral with the encapsulation housing. U.S. Pat. No. 4,680,569 describes a semiconductor pressure sensor with a semiconductor diaphragm chip whose pressure-detecting area is connected in a pressure-tight manner to the housing exterior via chimney-shaped connection penetrating through the housing.
It is common to all the previously known configurations of semiconductor pressure sensors that their production always necessitates a multistage process for covering or encapsulating the component, by means of which process the component is brought to its desired design.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a pressure sensor component and production method, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and in which the semiconductor chip carrying the mechanically sensitive pressure sensor, and/or the chip carrier, can be encapsulated more simply in structural terms and thus more cost-effectively and which, furthermore, assures that the connection between the medium to be measured and the pressure sensor is comparatively simple to establish but is nevertheless sufficiently tight.
With the foregoing and other objects in view there is provided, in accordance with the invention, a pressure sensor component, comprising:
a chip carrier formed with a substantially planar chip carrier surface;
a semiconductor chip disposed on the chip carrier surface, the semiconductor chip having an integrated pressure sensor with a pressure-detecting surface exposed to a pressure to be measured;
a component encapsulation of electrically insulating material at least partly enclosing one of the semiconductor chip and the chip carrier; and
a chimney-shaped connection piece incorporated into the component encapsulation for exposing the pressure-detecting surface to the pressure to be measured, the connection piece having an end bearing on the semiconductor chip and pressure-tightly enclosing the pressure-detecting surface, projecting away from the pressure-detecting surface of the pressure sensor, and penetrating through the component encapsulation.
In other words, the invention provides for a chimney-shaped connection piece, which projects up relative to the pressure-detecting surface area of the pressure sensor, penetrates through the encapsulation and is connected to the pressure sensor. The connection piece is to be arranged or incorporated in the component encapsulation, it encloses at least the pressure-detecting area in a pressure-tight manner with its end bearing on the semiconductor chip, and it is open toward the outside at its opposite end.
As will be seen from the following description, the method of producing the pressure sensor component provides for a chimney-shaped connection piece to be placed onto the pressure sensor after the mounting and contact-making of the semiconductor chip on the chip carrier but still prior to the encapsulation of the pressure sensor.
According to an essential concept of the invention, provision is made, as it were, of complete integration of an opening in the housing in the form of a chimney-shaped connection piece which is preferably formed as an independent structural part. Only the pressure-sensitive surface (the pressure-detecting surface area) of the semiconductor chip remains free. The remaining constituents or regions of the semiconductor chip are covered with encapsulation material, in particular molding compound. The opening in the component lies above the pressure-sensitive area of the semiconductor chip, in order to make it possible to sense different pressures at this point. The actual encapsulation of the pressure sensor component, that is to say the covering of the chip carrier, the rest of the semiconductor chip and, if appropriate, bonding wires, leads to the desired protection of the pressure sensor component against environmental influences and enables the application and use of the pressure sensor for example in the context of mounting on a printed circuit board. Consequently, an essential advantage of the solution according to the invention resides in targeted pressure coupling using an opening in conjunction with the sealing of the component with molding compound.
In accordance with an added feature of the invention, the pressure to be measured is passed via an opening formed in the chimney-shaped connection piece directly onto the pressure-detecting surface of the semiconductor chip.
The pressure to be measured is passed via the
Bootz Eric
Janczek Thies
Neu Achim
Stadler Bernd
Winterer Jurgen
Easthom Karl D.
Greenberg Laurence A.
Infineon - Technologies AG
Lerner Herbert L.
Stemer Werner H.
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