Abstract:
A pressure sensor module includes a pressure sensor in a sensor housing, the pressure sensor being easily mountable and pre-calibrated.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a pressure sensor module. 
     BACKGROUND INFORMATION 
     A pressure sensor device that includes a semiconductor chip having a pressure sensor is described in International Published Patent Application No. WO 98/00692. The arrangement is intended for mounting on a p.c. board. The electric leads of the semiconductor chip are not hermetically injected in the plastic of the housing. In the presence of a partial vacuum in the area of the pressure sensor, air may be drawn along the leads into the gel, mechanically stressing the bonding wires, i.e., bonds. In addition, the separating membrane corrupts the pressure characteristic of the semiconductor chip, due to its rigidity. In situations that require stricter measuring accuracy, it may therefore be required to increase the membrane diameter and reduce the membrane thickness. This may have a negative effect on miniaturization. 
     A pressure sensor chip that is mounted and fastened as a single unit in a pressure sensor module housing is described from mstnews 2/99, pages 8 to 9. It may not be possible to calibrate the pressure sensor until after the pressure sensor chip has been mounted, since mounting the pressure sensor chip and passivating it with a covering arrangement may influences a calibration curve. Therefore, the entire module housing, including the attached pressure sensor, may need to be exposed to different temperatures and pressures to achieve calibration. The long waiting period for heating the large sensor housing and the low packing density for calibration may make this very expensive. 
     In the case of the conventional pressure sensor, the reject rate during calibration may also not be detected until after the sensor chip is mounted. When this happens, the expensive pressure sensor module housing may no longer be usable. This may increases costs due to rejection. 
     A pressure sensor module in which the pressure sensor is sealed pressure-tight by a cover is described in German Published Patent Application No. 197 314 20. This mounting method may be expensive, as may be the use of a ceramic substrate. In addition, the frame surrounding the gel may need to be separately attached to the ceramic substrate. 
     SUMMARY 
     A pressure sensor module according to the present invention may provide a simple arrangement for mounting a pressure sensor in a module housing and producing a pressure sensor module. 
     A sensor housing may be made of plastic because the latter may be easy to produce. 
     Electric leads may be surrounded, at least in part, by the sensor housing, which holds them in place and enables the leads to pass through the sensor housing. 
     To protect a pressure sensor in its sensor housing against external ambient conditions and encapsulate it in a pressure-tight manner, the sensor housing may be surrounded by an encapsulating compound. In addition, the encapsulating compound may achieves a gas-tight passage for the leads. 
     The pressure sensor may have elements for improving electromagnetic compatibility. 
     As elements for improving electromagnetic compatibility, capacitors are advantageously connected electrically and mechanically to the electric leads by conductive adhesive, soldering or welding. 
     A media-resistant gel, such as fluorosilicone gel, may be used as the covering arrangement for the pressure sensor chip, so that other protection measures may be rendered unnecessary. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrated a first example embodiment of a pressure sensor module configured according to the present invention. 
     FIG. 2 illustrates a second example embodiment of a pressure sensor module configured according to the present invention. 
     FIG. 3 illustrates a third embodiment of a pressure sensor module designed according to the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a first example embodiment of a pressure sensor module  1  according to the present invention. Pressure sensor module  1  includes, among other things, a module housing  3 , in which a pressure sensor  6 , for example in the form of a sensor chip, is provided in a sensor housing  8 . Pressure sensor  6  is in contact with a medium  10  to be measured, which reaches pressure sensor  6 , for example, via a connecting sleeve  33 . Sensor housing  8  may be, for example, in the shape of a U, with the opening of the U shape coming into contact with the medium  10  to be measured and may be completely surrounding an opening  11  of connecting sleeve  33 . Pressure sensor  6  is covered and therefore protected by a covering arrangement, for example a gel, in its sensor housing  8 . 
     Sensor housing  8  may be arranged, for example, in a recess  15  of module housing  3  and may be completely surrounded, for example, by an encapsulating compound  17 . Encapsulating compound  17  seals sensor housing  8  and module housing  3  so that a medium  10  to be measured may not penetrate recess  15 . In addition, encapsulating compound  17 , which may be required to be cured, may hold sensor housing  8  in recess  15 , and it may also seals electric leads  21  passing through sensor housing  8 . This makes it unnecessary to provide a cover that hermetically encapsulates recess  15  and protects it against external influences. 
     Pressure sensor  6  is connected by bonding wires  19  to electric leads  21 , which establish the connection to external electrical connector elements  25 . Connector elements  25  may serve the purpose of connecting the arrangement to an electronic controller. Junction  23  between connector elements  25  and leads  21 , which may be produced by welding or soldering, is also located in recess  15  in encapsulating compound  17 . 
     Pressure sensor module  1  has, for example, at least one further element  27  in recess  15  for improving electromagnetic compatibility, for example in the form of capacitors. Capacitors  27  are electrically and mechanically attached to electric leads  21  or connector elements  25 , for example, by conductive adhesive, soldering or welding. Capacitors  27  may be arranged, for example, directly at junction  23 . 
     FIG. 2 shows a further exemplary embodiment of a pressure sensor module  1  according to the present invention. In this case, module housing  3  may have, in addition to recess  15 , a cavity  35  through which pass connector elements  25  or electric leads  21 . Capacitors  27  may be electrically connected to connector elements  25  in cavity  35  and may be surrounded and protected by an encapsulating compound  17 . Junction  23  may also be situated in cavity  35 . 
     Because capacitors  27  are positioned at a greater physical distance from welded junction  23  between connector elements  25  and leads  21  than they are in FIG. 1, they are also be electrically connectable to electric leads  21  or connector elements  25  by soldering or gluing. 
     Module housing  3  also includes, for example, connecting sleeve  33  having a sealing ring  29  so that connecting sleeve  33  is insertable into a further component containing medium  10  to be measured. Connecting sleeve  33  is sealed against the component by sealing ring  29  so that medium  10  to be measured contained in the component may come into contact only with pressure sensor  6  and may not escape from the component at the point where connecting sleeve  33  is mounted. 
     Pressure sensor module  1  may also have a temperature sensor  40 , for example an NTC resistor. 
     FIG. 3 shows a further exemplary embodiment of pressure sensor module  1  according to the present invention, based on FIG.  2 . Welded junction  23  is located in cavity  35  so that elements  27  may be arranged as close as possible to pressure sensor  6 , i.e., in recess  15 .