Conductive seals and method for fabricating the same

A conductive seal comprises a central opening that can be disposed proximate to a lower surface of a diaphragm in a pressure sense die. A set of electrically conductive elements can be disposed directly over electrically conductive bonding pads on the pressure sense die in such a manner that a number of electrically molded leads can be in electrical contact with the pressure sense die. A set of electrically insulating elements can be placed adjacent to the conductive elements. The conductive elements can be located away from edges of the conductive seal, towards the central opening of the conductive seal without minimizing the insulation between the central opening and the conductive elements of the seal. Therefore, the conductive seal can prevent the pressure sense die and other electrical circuitry from die-edge shorting in order to achieve long-term sensor reliability and performance.

TECHNICAL FIELD

Embodiments are generally related to pressure sensors. Embodiments are also related to elastomeric conductive seals utilized in the context of pressure sensors. Embodiments are additionally related to the fabrication of elastomeric conductive seals.

BACKGROUND OF THE INVENTION

Pressure sensors are utilized in a wide range of sensing applications. For such applications, differential, gauge and absolute pressure sensors may accurately sense the pressure of a liquid or gaseous media. Each of these pressure sensors can be configured utilizing semiconductor technology. One of the most common types of pressure sensors is solid-state silicon pressure sensors. Such pressure sensors may incorporate a pressure sense die to exhibit a high degree of sensing accuracy. The pressure sense die provides an electrical output in response to an applied stress or pressure. The pressure sensors also can include one or two pressure ports, through which the media passes.

Some pressure sensors utilize a conductive elastomeric seal for electrically connecting a number of electrical terminals or molded-in leads to the pressure sense die. The pressure sense die can be sandwiched and compressed between an elastomeric media seal and conductive elastomeric seals contained within a plastic housing without significantly changing the output of the pressure sense die due to applied stress. These conductive seals may include two parallel, laminated conductor and insulator strips, which run from one side to the other side. Such a pressure sensor design allows the conductive seal to be slightly offset relative to the pressure sense die in the plastic housing due to manufacturing tolerances. The conductive seals can be compressed against the sense die in order to construct a pneumatic seal and effective electrical connection over the operating pressure and temperature range of the pressure sensor.

The elastomeric seals are conductive in certain precisely-determined regions so as to connect signals from the pressure sense die to the electrical terminals, which exit the housing of the pressure sensor. The conductive seals may, however, cause an electrical short if the conductor or insulator bands are forced over the edge of the pressure sense die, because the pressure sense die typically constitutes a semiconductor. In particular, electrical shorting occurs when the conductive seals wrap over the edge of the pressure sense die. The electrical shorting may short out a Wheatstone bridge or other electronic circuitry located on the sensor package such that it changes the sensor output intermittently. This intermittent sense output is difficult to detect during manufacturing and results in “die-edge shorting” in the pressure sensors.

In the majority of prior art pressure sensors, the elastomeric seals exhibit an inherent electrical shorting problem with the pressure sense die if perfect alignment is not held when the package is snapped together and the seals are compressed. The conductive seals may wrap over the edge of the pressure sense die, since the pressure sense die is slightly smaller than the package housing in order to fit the pressure sense die into the housing due to manufacturing tolerances. Therefore, die-edge shorting may occur when the pressure sense die is compressed against the seals, which can lead to a sensor malfunction or failure. Hence, it is desirable to prevent the sensing die, circuitry and electrical connections from exposure to die-edge shorting in order to ensure reliable operation of the pressure sensor.

Moreover, some current seal designs are constructed by bonding together a series of laminations of conductors and insulators utilizing adhesives, in addition to the use of a punching operation to form the hole and a slicing operation to construct individual parts. These operations can result in poorly formed parts and components that occasionally fail to meet dimensional specifications. Therefore, the pressure sensors should be constructed in such a manner that it enables the sensor parts to meet proper dimensional specifications.

A need, therefore, exists for an improved conductive seal, which achieves the elimination of die-edge shorting and which is ultimately more efficient and sturdier than presently implemented pressure sensors. Such conductive seals are described in greater detail herein.

BRIEF SUMMARY

It is, therefore, one aspect of the present invention to provide for an improved conductive seal utilized in the context of pressure sensors.

It is another aspect of the present invention to provide for a method for fabricating a conductive seal.

The aforementioned aspects and other objectives and advantages can now be achieved as described herein. A conductive seal includes a central opening that can be disposed proximate to a lower surface of a diaphragm in a pressure sense die. A set of conductive elements can be disposed directly over electrically conductive bonding pads on the pressure sense die in such a manner that a number of metal leads molded in a housing can be in electrical contact with the pressure sense die. These conductive elements should be surrounded by an elastomeric insulator and can be located away from edges of the conductive seal, towards the central opening of the conductive seal without minimizing the insulation between the central opening and the conductive elements of the seal. Therefore, the conductive seal can prevent the pressure sense die and other electrical circuitry from die-edge shorting in order to achieve long-term reliability and performance of a pressure sensor.

Furthermore, the conductive seal can be injection molded with conductive elements inserted into a mold and an elastomer molded around these elements. Such injection molding results in an enhanced sensor part formation and an increased capability of meeting the dimensional tolerances. The conductive seal can be disposed between the pressure sense die and a plastic housing, wherein the conductive seal is selectively conductive and resilient.

Additionally, the conductive seal can be slightly offset relative to the pressure sense die in the plastic housing due to manufacturing tolerances. The seal and the pressure sense die can be compressed therebetween in order to make a pneumatic seal and provide an effective electrical connection over the operating pressure and temperature range of the pressure sensor. The conductive elements of the seal can be symmetrically located in such a manner that a pressure sensor package is assembled in several orientations thus simplifying the sensor manufacturing process. The conductive elements of the seal can be designed in various shapes in accordance with design considerations.

DETAILED DESCRIPTION

Referring toFIG. 1, a detailed and exploded view of a pressure sensor100is illustrated, in which embodiments of the present invention may be implemented. The pressure sensor100can be designed utilizing semiconductor technology. The pressure sensor100can include one or two pressure ports (either120and/or180) for allowing media to pass through therein. The two pressure ports120and180can be preferably configured from a metal or plastic material. The two pressure ports120and180can be incorporated with a metal or plastic cover110. Note that inFIGS. 1-8identical or similar parts or elements are generally indicated by identical reference numerals.

A silicon pressure sense die140can be pneumatically sealed to the pressure port120by compressing a media seal130between the pressure sense die and the pressure port. Similarly, a silicon pressure sense die140can be pneumatically sealed to the housing port180by compressing a conductive seal150between the pressure sense die and the housing port. The difference between pressures in each pressure ports120and180can be sensed by passing the media up to the pressure sense die140. The pressure sense die140can include a diaphragm141and multiple electrically conductive bonding pads (not shown) therein. The diaphragm141can be made of thin silicon materials in order to respond by deforming in proportion to even very minute media pressure. The electrically conductive bonding pads can be electrically connected to the diaphragm141in order to output electrical signals.

Furthermore, the diaphragm141can be incorporated with piezoresistive elements (not shown) that convert the deformation of the diaphragm141due to the applied pressure into an electrical output (utilizing well-known piezoresistive principles) that is proportional to the applied pressure. The bonding pads of the pressure sense die140can be integrated on the piezoresistive elements. The pressure sense die140can further be in electrical contact with a conductive seal150in order to continue the electrical connection to several external electrical terminals or molded-in leads170. The media seal130, the pressure sense die140and the conductive seal150can be incorporated into a metal or plastic housing160, into which the electrical terminals or leads170can be molded. Such a pressure sensor assembly100can provide an accurate output signal.

Referring toFIG. 2, an enlarged view of a conductive seal150, as shown inFIG. 1, is illustrated, in accordance with the present embodiment. The conductive seal150comprises a central opening152, a set of parallel, laminated conductor strips154, and a set of parallel, laminated insulator strips158.FIG. 3illustrates a cross-sectional view of the conductive seal150along line A-A inFIG. 2. The conductive strips154can be made of an elastomeric material, (i.e. elastomer156), intermixed with conductive particles. The central opening152can be disposed proximate to a lower surface of the diaphragm141in the pressure sense die140, as shown inFIG. 1. The central opening152can be provided for allowing a liquid or gaseous media to pass through. The dimensional manufacturing and assembly tolerances in this present design make it possible for the die-edge shorting condition described previously to occur.

Referring toFIG. 4, an enlarged view of the conductive seal150, as shown inFIG. 1, is illustrated, in accordance with a preferred embodiment. The conductive seal150can be disposed between the pressure sense die140and the housing160, where the conductive seal150is selectively conductive and resilient. This conductive seal comprises a set of rectangular-shaped conductive elements400. The conductive seal150can be incorporated with several conductive elements400based on design requirements. The conductive elements400can be disposed directly over the electrically conductive bonding pads (not shown) on the pressure sense die140in such a manner that a number of electrically molded leads170can be in electrical contact with the pressure sense die140.

The central opening152can be disposed proximate to a lower surface of the diaphragm141in the pressure sense die140, as shown inFIG. 1. The central opening152can be provided for allowing a liquid or gaseous media to pass through. The rectangular-shaped conductive elements400can be positioned at each corner of the conductive seal150with a specific distance away from the edges of the seal150, which provides sufficient sealing effect between the pressure sense die140and the seal150. Such conductive seal150with the rectangular-shaped conductive elements400can seal the pressure sense die140and other electronic circuits to protect the pressure sense die140from die-edge shorting.

The rectangular-shaped conductive elements400can be symmetrically located in such a manner that the pressure sensor package100can be assembled in several orientations. The conductive seal150can be slightly offset relative to the pressure sense die140in the plastic housing160due to manufacturing tolerances. The seal150and the pressure sense die140can be compressed therebetween in order to make a pneumatic seal and effective electrical connection over the operating pressure and temperature range. Such compressive force can provide appropriate pressure between the pressure sense die140and the seal150to maintain electrical communication between the bonding pads of the pressure sense die140and the rectangular-shaped conductive elements400of the seal150.

The conductive seal150can be injection molded with the rectangular-shaped conductive elements400inserted into a mold and an elastomer156can be molded around the seal150. Such injection molding results in better sensor part formation and higher capability of meeting the dimensional tolerances.

These geometrical shapes of the conductive elements400are described for purposes of clarity and specificity; however, they should not be interpreted in any limiting way. Other shapes are also possible. However, it will be apparent to those skilled in the art that the geometrical shapes can be changed without departing from the scope of the invention.

Note that inFIGS. 1-8, identical or similar parts or elements are generally indicated by identical reference numerals.

Referring toFIG. 5, an enlarged view of the conductive seal150with L-shaped conductive elements500is illustrated, in accordance with an alternative embodiment. The conductive seal150can be disposed between the pressure sense die140and the housing160, where the conductive seal150is selectively conductive and resilient. This conductive seal comprises a set of L-shaped conductive elements500. The conductive seal150can be incorporated with several conductive elements500based on design requirements. The conductive elements500can be disposed directly over the electrically conductive bonding pads (not shown) on the pressure sense die140in such a manner that a number of electrically molded leads170can be in electrical contact with the pressure sense die140.

The central opening152can be disposed proximate to a lower surface of the diaphragm141in the pressure sense die140, as shown inFIG. 1. The central opening152can be provided for allowing a liquid or gaseous media to pass through. The L-shaped conductive elements500can be positioned at each corner of the conductive seal150with a specific distance away from the edges of the seal150, which provides sufficient sealing effect between the pressure sense die140and the seal150. Such conductive seal150with the L-shaped conductive elements500can seal the pressure sense die140and other electronic circuits to protect the pressure sense die140from die-edge shorting.

The L-shaped conductive elements500can be symmetrically located in such a manner that the pressure sensor package100can be assembled in several orientations. The conductive seal150can be slightly offset relative to the pressure sense die140in the plastic housing160due to manufacturing tolerances. The seal150and the pressure sense die140can be compressed therebetween in order to make a pneumatic seal and effective electrical connection over the operating pressure and temperature range. Such compressive force can provide appropriate pressure between the pressure sense die140and the seal150to maintain electrical communication between the bonding pads of the pressure sense die140and the L-shaped conductive elements500of the seal150. The conductive seal150can be injection molded with the L-shaped conductive elements500inserted into a mold and an elastomer156can be molded around the seal150.

Referring toFIG. 6, a schematic perspective view of the conductive seal150with triangular-shaped conductor strips600is illustrated, in accordance with an alternative embodiment. The conductive seal150can be disposed between the pressure sense die140and the housing160, where the conductive seal150is selectively conductive and resilient. This conductive seal comprises a set of triangular-shaped conductive elements600. The conductive seal150can be incorporated with several conductive elements600based on design requirements. The conductive elements600can be disposed directly over the electrically conductive bonding pads (not shown) on the pressure sense die140in such a manner that a number of electrically molded leads170can be in electrical contact with the pressure sense die140.

The central opening152can be disposed proximate to a lower surface of the diaphragm141in the pressure sense die140, as shown inFIG. 1. The central opening152can be provided for allowing a liquid or gaseous media to pass through. The triangular-shaped conductive elements600can be positioned at each corner of the conductive seal150with a specific distance away from the edges of the seal150, which provides sufficient sealing effect between the pressure sense die140and the seal150. Such conductive seal150with the triangular-shaped conductive elements600can seal the pressure sense die140and other electronic circuits to protect the pressure sense die140from die-edge shorting.

The triangular-shaped conductive elements600can be symmetrically located in such a manner that the pressure sensor package100can be assembled in several orientations. The conductive seal150can be slightly offset relative to the pressure sense die140in the plastic housing160due to manufacturing tolerances. The seal150and pressure the sense die140can be compressed therebetween in order to make a pneumatic seal and effective electrical connection over the operating pressure and temperature range. Such compressive force can provide appropriate pressure between the pressure sense die140and the seal150to maintain electrical communication between the bonding pads of the pressure sense die140and the triangular-shaped conductive elements600of the seal150. Note that the conductive seal150can be injection molded with the triangular-shaped conductive elements600inserted into a mold and an elastomer156can be molded around the seal150.

Referring toFIG. 7, an enlarged view of the conductive seal150with circular-shaped conductive elements700is illustrated, in accordance with an alternative embodiment. The conductive seal150can be disposed between the pressure sense die140and the housing160, where the conductive seal150is selectively conductive and resilient. This conductive seal comprises a set of circular-shaped conductive elements700. The conductive seal150can be incorporated with several conductive elements700based on design requirements. The conductive elements700can be disposed directly over the electrically conductive bonding pads (not shown) on the pressure sense die140in such a manner that a number of electrically molded leads170can be in electrical contact with the pressure sense die140.

The central opening152can be disposed proximate to a lower surface of the diaphragm141in the pressure sense die140, as shown inFIG. 1. The central opening152can be provided for allowing a liquid or gaseous media to pass through. The circular-shaped conductive elements700can be positioned at each corner of the conductive seal150with a specific distance away from the edges of the seal150, which provides sufficient sealing effect between the pressure sense die140and the seal150. Such conductive seal150with the circular-shaped conductive elements700can seal the pressure sense die140and other electronic circuits to protect the pressure sense die140from die-edge shorting.

The circular-shaped conductive elements700can be symmetrically located in such a manner that the pressure sensor package100can be assembled in several orientations. The conductive seal150can be slightly offset relative to the pressure sense die140in the plastic housing160due to manufacturing tolerances. The seal150and pressure the sense die140can be compressed therebetween in order to make a pneumatic seal and effective electrical connection over the operating pressure and temperature range. Such compressive force can provide appropriate pressure between the pressure sense die140and the seal150to maintain electrical communication between the bonding pads of the pressure sense die140and the circular-shaped conductive elements700of the seal150.

The conductive seal150can be injection molded with the circular-shaped conductive elements700inserted into a mold and an elastomer156can be molded around the seal150.

Referring toFIG. 8, a flow chart illustrative of a method800for fabricating the conductive seal150is illustrated, in accordance with an alternative embodiment. As illustrated at block810, a central opening152can be formed on the conductive seal150proximate to a lower surface of a diaphragm141in a pressure sense die140. As indicated at block820, a set of conductive elements154can be disposed directly over electrically conductive bonding pads on the pressure sense die140in such a manner that a number of electrical terminals170can be in electrical contact with the pressure sense die140.

Thereafter, as described at block830, insulating elements156can be placed adjacent to and surrounding the conductive elements154. Finally, as depicted at block840, the set of conductive elements154can be located in the corners away from edges of the conductive seal150, towards the central opening152of the conductive seal150without minimizing the insulation between the central opening152and the conductive elements154of the seal150. Hence, the conductive seal150can prevent die-edge shorting with the pressure sense die140and other electrical circuitry, which enables a long-term reliability of the pressure sensor100.