Patent Description:
As shown in <CIT>, for example, a sensor unit to be built in a liquid sealing semiconductor pressure sensor comprises, as its main elements: a metallic diaphragm supported inside a joint and configured to isolate a pressure detection chamber from a liquid sealing chamber to be described below; the liquid sealing chamber formed above the metallic diaphragm and configured to accommodate a silicone oil serving as a pressure transmitting medium; a sensor chip provided in the liquid sealing chamber and configured to detect a variation in pressure in the silicone oil via the metallic diaphragm; a sensor chip mounting member configured to support the sensor chip; a hermetic glass configured to establish hermetic seal around the sensor chip mounting member in a through hole of a housing; and a group of terminals (lead pins) configured to send an output signal from the sensor chip and to supply electric power to the sensor chip.

In the above-described configuration, the metallic diaphragm, a base plate, and the joint are connected to one another at the same electric potential while these regions are insulated from the sensor chip. In a case where a primary power supply being a power source is insufficiently insulated from a secondary power supply being a control circuit to process the output signal from the sensor chip, an electric potential difference occurs between the metallic diaphragm and the sensor chip, which are located opposite to each other, because impedance on the sensor chip side is higher. To avoid an effect (a variation in output from the pressure sensor) on an electronic circuit and on a nonvolatile memory in such a sensor chip attributed to electric potential difference occurring both on the metallic diaphragm and on the sensor chip, provision of a metallic lower plate and a metallic member provided on an end surface of a hermetic glass in such a way as to surround the sensor chip and to define a cylindrical space has been proposed as shown in <CIT>, for example. The sensor chip is electrically connected to lead pins and a metallic member, which are coupled via a presser plate to a zero potential of an electronic circuit that is integrated in the sensor chip. Hereby, because the electric potentials of the lower plate and the metallic member become equal to the zero potential of the electronic circuit of the sensor chip located in the space surrounded by the lower plate and the metallic member, there is no difference in electric potential between the metallic diaphragm and the sensor chip. Accordingly, there is no risk of occurrence of an electric field that may affect the electronic circuit of the sensor chip.

<CIT> and <CIT> disclose further pressure sensors.

In addition, as a measure in this case, it can be considered that the way connecting the lead pins to the zero potential of the electronic circuit integrated in the sensor chip is available by further disposing a presser plate like the one mentioned above, which is to be connected to lead pins projecting from another end surface of the hermetic glass located away from the aforementioned liquid sealing chamber, or achieving electrical connection to the lead pins in another process, for example.

However, the above measure is inadvisable because the necessities of the arrangement of the additional presser plate and the operation to connect the lead pins to the presser plate result in an increase in the number of components of the pressure sensor and an increase in the number of assembly operation processes.

In view of the above-described problem, the present invention aims to provide a pressure sensor. The pressure sensor can reduce an effect of an electric field occurring between a senor chip and a metallic diaphragm in the pressure sensor without causing increases in the number of components and in assembly operation processes.

To achieve the above-described object, a pressure sensor according to the present invention comprises the features specified in claim <NUM>.

The pressure sensor according to the present invention includes the electric field blocking member which is placed between the one end surface of the sensor chip in the liquid sealing chamber and the diaphragm. Thus, it is possible to reduce an effect of an electric field occurring between a senor chip and a metallic diaphragm in a pressure sensor without causing increases in the number of components and in assembly operation processes.

<FIG> schematically illustrates a configuration of a pressure sensor applying an example of a shield structure for a pressure sensor which does not fall within the scope of the claimed invention.

In <FIG>, a pressure sensor comprises: a joint member <NUM> to be coupled to a piping into which a fluid supposed to undergo pressure detection is introduced; and a sensor unit accommodating portion which is joined to a base plate <NUM> of the joint member <NUM> by brazing or the like, for example, accommodates a sensor unit to be described later, and supplies a detection output signal from the sensor chip to a given pressure measurement apparatus.

The joint member <NUM> made of metal has a female screw portion 30fs on its inside to be screwed into a male screw portion of a connector portion of the aforementioned piping. The female screw portion 30fs is communicated with a port 30a of the joint member <NUM> which brings the fluid supplied in a direction indicated with an arrow P to a pressure chamber 28A to be described later. One of open ends of the port 30a is open toward the pressure chamber 28A formed between the base plate <NUM> of the joint member <NUM> and a diaphragm <NUM> of the sensor unit.

A contour portion of the sensor unit accommodating portion is formed as a cover member from a cylindrical waterproof case <NUM>. An opening 20b is formed at a lower end portion of the waterproof case <NUM> that is made of resin. A peripheral edge portion of the base plate <NUM> of the joint member <NUM> is engaged with a stepped portion on a peripheral edge of the opening 20b inside the case <NUM>.

A pressure of the fluid is brought into the pressure chamber 28A through the port 30a of the joint member <NUM>.

A lower end surface of a housing <NUM> of the sensor unit is coupled by welding to the peripheral edge portion of the base plate <NUM>.

The sensor unit for detecting the pressure inside the pressure chamber 28A and sending a detection output signal comprises, as its main elements, the cylindrical housing <NUM> made of metal, the diaphragm <NUM> made of metal and configured to isolate the pressure chamber 28A from an inner peripheral portion of the housing <NUM>, a sensor chip <NUM> provided with a plurality of pressure detection elements and a signal processing electronic circuit unit to process signals from the pressure detection elements, a chip mounting member <NUM> made of metal and configured to support the sensor chip <NUM> at an end portion through an adhesive layer <NUM>, a group of input-output terminals 40ai (i = <NUM> to <NUM>) electrically connected to the sensor chip <NUM>, and a hermetic glass <NUM> configured to fix the group of input-output terminals 40ai and an oil filling pipe <NUM> to a portion between an outer peripheral surface of the chip mounting member <NUM> and an inner peripheral surface of the housing <NUM>.

The diaphragm <NUM> is supported by one lower end surface of the housing <NUM> face to face relationship with the above-mentioned pressure chamber 28A. A diaphragm protection cover <NUM> to protect the diaphragm <NUM> provided in the pressure chamber 28A has a plurality of communication holes 34a. A peripheral edge of the diaphragm protection cover <NUM> is joined by welding to the lower end surface of the housing <NUM> together with a peripheral edge of the diaphragm <NUM>. The housing <NUM>, the diaphragm <NUM>, the base plate <NUM>, and the joint member <NUM> are connected to and conducted with one another and therefore have the same electric potential. In addition, the group of input-output terminals 40ai and the chip mounting member <NUM> are held by being insulated from the housing <NUM> by using an insulator such as the hermetic glass <NUM>.

A liquid sealing chamber <NUM> formed between the diaphragm <NUM> made of metal and the sensor chip <NUM>, an end surface of the hermetic glass <NUM> face to face relationship with the diaphragm <NUM> is filled with a predetermined amount of a pressure transmitting medium PM such as a silicone oil and a fluorine-based inert liquid via the oil filling pipe <NUM>. Note that one end portion of the oil filling pipe <NUM> is squashed and occluded after the oil filling as indicated with chain double-dashed lines.

The group of input-output terminals 40ai (i = <NUM> to <NUM>) is comprised of two power supply terminals, one output terminal, and five adjustment terminals. Both end portions of each terminal project from an end portion of the above-mentioned hermetic glass <NUM> toward the liquid sealing chamber <NUM> or toward a hole 24b in a terminal block <NUM> to be described later. The two power supply terminals and the one output terminal are connected to core wires 38a of respective lead wires <NUM> through connection terminals <NUM>. Each lead wire <NUM> is connected to a predetermined pressure measurement apparatus, for example. Note that <FIG> illustrates only four terminals out of the eight terminals. The group of input-output terminals 40ai are connected to the sensor chip <NUM> to be described later by using bonding wires Wi.

The terminal block <NUM> to align the group of input-output terminals 40ai is molded by using a resin material such as polybutylene terephthalate (PBT) as a key component. The terminal block <NUM> has the plurality of holes 24b into which the group of input-output terminals 40ai are inserted, and a hollow portion 24A having a predetermined volume inside. A terminal alignment portion 24T has the plurality of holes 24b located away from one another and is integrally molded in such a way as to orthogonally intersect the above-mentioned base end portion. A lower end surface of the base end portion of the terminal block <NUM> as an adhesion surface is attached to an upper end surface of the housing <NUM> by using a silicone-based adhesive. Hereby, an annular adhesive layer 10a having a predetermined thickness is formed on the upper end surface of the housing <NUM>. Further, a coating layer 10b made of a silicone-based adhesive is formed in a predetermined thickness on the entire upper end surface of the hermetic glass <NUM> from which the group of input-output terminals 40ai project.

A space between an inner peripheral surface of the waterproof case <NUM> and an outer peripheral surface of the terminal block <NUM> serving as a terminal alignment member as well as an outer peripheral surface of an end cap <NUM> connected to the terminal block <NUM> and covering the holes 24b in the terminal alignment portion 24T mentioned above as well as an open end at an upper part of the terminal block <NUM>, and a space between the inner peripheral surface of the waterproof case <NUM> and an outer peripheral surface of the housing <NUM> are filled with a given amount of a sealing medium <NUM>. The terminal block <NUM> and the end cap <NUM> are facing the base plate <NUM> of the joint member <NUM> while interposing the above-described sensor unit and are disposed in the waterproof case <NUM>. An upper end surface of the end cap <NUM> projects upward from an open end of the waterproof case <NUM>. Namely, a position of the upper end surface of the end cap <NUM> is located at a higher position than a position of an open end surface of the waterproof case <NUM>.

The sensor chip <NUM> is adhered to one end portion of the chip mounting member <NUM> located inside the liquid sealing chamber <NUM> through the adhesive layer <NUM>, for example. As shown in <FIG>, an external size of the sensor chip <NUM> having a substantially rectangular shape is set larger than a diameter of the chip mounting member <NUM>.

In the liquid sealing chamber <NUM>, a disk conductive plate <NUM> is supported by one of end surfaces of the hermetic glass <NUM> in such a way as to surround the sensor chip <NUM>, for example. The conductive plate <NUM> is made of an insulating material which is one of resin, glass, and ceramic, and one of end surfaces thereof is formed out of a metallic film and integrated with the metallic film of gold, silver, copper, aluminum, or the like serving as a conductive layer, which is formed by adherence, vapor deposition, plating, or the like. The one end surface of the conductive plate <NUM> provided with the conductive layer as mentioned above is opposed to the diaphragm <NUM> and the other end surface being an insulating layer of the conductive plate <NUM> is supported by the hermetic glass <NUM>.

In addition, a shielding member <NUM> serving as an electric field blocking member is provided between one of end surfaces of the sensor chip <NUM> and the diaphragm <NUM> in the liquid sealing chamber <NUM>. The shielding member <NUM> is configured to block an electric field undesirable for the signal processing electronic circuit unit of the sensor chip <NUM>.

The shielding member <NUM> may be formed from a conductive metal material such as stainless steel, copper, and aluminum, for example. Further, the shielding member <NUM> may be formed from an insulating material such as resin, glass, and ceramic with its surface layer being provided and integrated with film-formed conductive metal by adhesion, vapor deposition, sputtering, plating, and the like, for example.

As shown in <FIG>, four fixing end portions of the cap-shaped shielding member <NUM> are brought close to an outer peripheral portion of the sensor chip <NUM> on the one end surface of the disk conductive plate <NUM>, and are joined to and conducted with the outer peripheral portion. Although illustration is omitted, a plurality of openings are provided in a side surface of the shielding member <NUM>. A shape of the shielding member <NUM> is formed into a shape that enables the pressure transmitting medium PM to move such that a pressure in accordance with a displacement of the diaphragm <NUM> propagates to the sensor chip <NUM> through the pressure transmitting medium PM.

The conductive plate <NUM> is connected to and conducted with one or more of the group of input-output terminals 40ai through e.g. a zero (V) terminal and the bonding wire Wi. According to this configuration described above, the electric potentials of the shielding member <NUM> and the conductive plate <NUM> are set to the same electric potential as that of the electronic circuit mounted in the sensor chip <NUM>.

A predetermined clearance is formed between a portion of the shielding member <NUM> covering the entire sensor chip <NUM> and the end surface of the sensor chip <NUM>. Note that an external size of the shielding member <NUM> may be appropriately set according to the size of the signal processing electronic circuit unit of the sensor chip <NUM> so as to block the electric field undesirable for the signal processing electronic circuit unit of the sensor chip <NUM>.

Accordingly, as a consequence of disposing the shielding member <NUM> having the same electric potential as the electric potential of the sensor chip <NUM> between the diaphragm <NUM> and the signal processing electronic circuit unit of the sensor chip <NUM>, an electric field to act on the sensor chip <NUM>, which occurs due to a potential difference between the diaphragm <NUM> having the same electric potential as that of a primary power supply (not shown) of the unit and a control circuit (not shown) side, is blocked by the shielding member <NUM>. Moreover, since the electric potential of the shielding member <NUM> and that of the sensor chip <NUM> are set to the same electric potential, no electric field occurs therebetween. For this reason, because the potential difference that occurs between the sensor chip <NUM> and the diaphragm <NUM> does not act on the sensor chip <NUM>, it is possible to prevent an effect on the electronic circuit in the sensor chip <NUM>.

<FIG> partially shows the essential parts of the pressure sensor applying another example of the shield structure for a pressure sensor according to the claimed invention.

In the example shown in <FIG>, the four fixing end portions of the cap-shaped shielding member <NUM> are brought close to the outer peripheral portion of the sensor chip <NUM> on the end surface of the disk conductive plate <NUM> and are joined to the end surface, for example. Instead, an example shown in <FIG> is designed such that a shielding plate <NUM> is supported on the end surface of the hermetic glass <NUM> in the liquid sealing chamber <NUM>.

Note that constituents in <FIG> which are the same as the constituents in the example shown in <FIG> will be indicated by the similar reference characters and overlapping explanations thereof will be omitted.

Though the illustration is omitted, this pressure sensor also comprises: a joint member to be coupled to a piping into which a fluid supposed to undergo pressure detection is introduced; and a sensor unit accommodating portion which is joined to a base plate of the joint member, accommodates a sensor unit to be described later, and supplies a detection output signal from the sensor chip to a given pressure measurement apparatus.

The shielding plate <NUM> serving as the electric field blocking member is provided between the one end surface of the sensor chip <NUM> and the diaphragm <NUM> in the liquid sealing chamber <NUM>. The shielding plate <NUM> is configured to block an electric field undesirable for the signal processing electronic circuit unit of the sensor chip <NUM>. The shielding plate <NUM> may be formed from a conductive metal material such as stainless steel, copper, and aluminum, for example. Alternatively, the shielding plate <NUM> may be formed from an insulating material such as resin, glass, and ceramic with one of its surface layers being formed and integrated with a conductive layer of conductive metal formed by adhesion, vapor deposition, sputtering, plating, and the like. As shown in <FIG>, the strip-shaped shielding plate <NUM> comprises a trench-shaped portion 48A facing the one end surface of the sensor chip <NUM>, and a first fixing portion 48B and a second fixing portion 48C continued to both end portions of the trench-shaped portion 48A. The trench-shaped portion 48A, the first fixing portion 48B, and the second fixing portion 48C are integrally molded by press work, for example. The trench-shaped portion 48A passes immediately above a central part of the sensor chip <NUM> with a predetermined clearance. The oil filling pipe <NUM> is press-fitted into a hole 48b in the first fixing portion 48B, and the respective group of input-output terminals 40ai projecting from the end surface of the hermetic glass <NUM> are inserted into holes 48f and 48d and a notch portion 48e of the second fixing portion 48C. Hereby, the first fixing portion 48B and the second fixing portion 48C come close to the outer peripheral portion of the sensor chip <NUM> at the one end portion of the chip mounting member <NUM> and come into contact with and get supported by the end surface of the hermetic glass <NUM>.

The second fixing portion 48C is conducted with one of the group of input-output terminals 40ai, e.g. the zero (V) terminal, which are connected to the one end surface being a conductive surface of the shielding plate <NUM> through the bonding wire Wi. According to this configuration described above, the electric potential of the conductive surface being the one end surface of the shielding plate <NUM> is set to the same electric potential as that of the electronic circuit mounted in the sensor chip <NUM>.

Note that an external size and a width dimension of the shielding plate <NUM> may be appropriately set depending on the size of the signal processing electronic circuit unit of the sensor chip <NUM> so as to block the electric field undesirable for the signal processing electronic circuit unit of the sensor chip <NUM>.

Accordingly, as a consequence of disposing the shielding plate <NUM> having the same electric potential as that of signal processing electronic circuit unit of the sensor chip <NUM> between the diaphragm <NUM> and the sensor chip <NUM>, an electric field to act on the sensor chip <NUM>, which occurs due to the potential difference between the diaphragm <NUM> having the same electric potential as that of the primary power supply (not shown) of the unit and the control circuit (not shown) side, is blocked by the shielding plate <NUM>. Moreover, since the electric potential of the shielding plate <NUM> and that of the sensor chip <NUM> are set to the same electric potential, no electric field occurs therebetween. For this reason, because the potential difference that occurs between the sensor chip <NUM> and the diaphragm <NUM> does not act on the sensor chip <NUM>, it is possible to prevent the effect on the electronic circuit in the sensor chip <NUM>.

<FIG> partially shows a configuration of the pressure sensor applying still another example of the shield structure for a pressure sensor which does not fall within the scope of the claimed invention.

A pressure sensor shown in <FIG> comprises: a joint member <NUM> to be coupled to a piping into which a fluid supposed to undergo pressure detection is introduced; and a sensor housing <NUM> made of metal, joined to the joint member <NUM> and a base plate <NUM> by brazing or the like, and configured to accommodate a sensor unit to be described later.

One of open ends of a port 60a of the joint member <NUM> is open toward a pressure chamber 58A formed between the base plate <NUM> of the joint member <NUM> and a diaphragm <NUM> of the sensor unit.

The sensor unit for detecting a pressure inside the pressure chamber 58A and sending a detection output signal comprises, as its main elements, the diaphragm <NUM> made of metal and configured to isolate the pressure chamber 58A from an inner peripheral portion of the sensor housing <NUM>, a sensor chip <NUM> provided with a plurality of pressure detection elements and a signal processing electronic circuit unit to process signals from the pressure detection elements, a conductive plate <NUM> provided with a hole into which an outer peripheral portion of the sensor chip <NUM> is inserted and configured to surround the sensor chip <NUM>, and a group of input-output terminals 54ai (i = <NUM> to <NUM>) electrically connected to the sensor chip <NUM>.

The diaphragm <NUM> made of metal is welded and fixed between a joining end of the sensor housing <NUM> mentioned above and a joining end of the base plate <NUM>. As a consequence, the electric potential of the sensor housing <NUM> is set to the same electric potential as the electric potentials of the diaphragm <NUM> and the like because the sensor housing <NUM> is connected to and conducted with the diaphragm <NUM>, the base plate <NUM>, and the joint member <NUM>.

A liquid sealing chamber <NUM> which is a hermetically sealed space formed from the diaphragm <NUM> and the inner peripheral portion of the sensor housing <NUM> is filled with a predetermined amount of the pressure transmitting medium PM such as a silicone oil and a fluorine-based inert liquid. After the pressure transmitting medium PM is put in via a hole 56a in the sensor housing <NUM>, the hole 56a is closed with a plug member <NUM>. The group of input-output terminals 54ai are supported while being insulated from the sensor housing <NUM> by using hermetic glass <NUM> (see <FIG>). The group of input-output terminals 54ai are connected to the sensor chip <NUM> by using the bonding wires Wi.

In the liquid sealing chamber <NUM>, the rectangular conductive plate <NUM> is supported by an inner peripheral surface of the sensor housing <NUM> in such a way as to surround the sensor chip <NUM>, for example. The conductive plate <NUM> is made of an insulating material which is one of resin, glass, and ceramic, and one of end surfaces thereof is formed out of a metallic film and integrated with the metallic film of gold, silver, copper, aluminum, or the like serving as a conductive layer, which is formed by adherence, vapor deposition, plating, or the like. The one end surface of the conductive plate <NUM> being the conductive layer is opposed to the diaphragm <NUM> and the other end surface being an insulating layer is supported by the sensor housing <NUM>. In addition, a shielding member <NUM> serving as the electric field blocking member is provided between one of end surfaces of the sensor chip <NUM> and the diaphragm <NUM> in the liquid sealing chamber <NUM>.

Moreover, the conductive plate may be comprised of a core member <NUM> made of an insulating material and a cover member <NUM> made of a conductive material and configured to cover the core member <NUM> as shown in <FIG>, for example. Note that illustration of the shielding member <NUM> is omitted in <FIG>.

The annular core member <NUM> has a stepped portion 63R provided on an inner peripheral edge portion and located adjacent to one end surface. The cover member <NUM> comprises a disk portion 67A that covers the other end surface of the core member <NUM> facing the diaphragm <NUM>, an inner peripheral edge portion 67C continued to the disk portion 67A and configured to cover an inner peripheral portion of the core member <NUM>, and a fixing portion 67B continued to the inner peripheral edge portion 67C and fixed to the stepped portion 63R of the core member <NUM> by swage processing. The one end surface of the core member <NUM> of the conductive plate is adhered to the inner peripheral surface of the sensor housing <NUM>. At that time, as shown in <FIG>, predetermined clearances are formed between the fixing portion 67B of the cover member <NUM> in the conductive plate and the inner peripheral surface of the sensor housing <NUM> as well as between an outer peripheral surface of the sensor chip <NUM> and the inner peripheral edge portion 67C of the cover member <NUM> in the conductive plate, thus preventing the sensor housing <NUM> from coming into contact with the cover member <NUM>.

Furthermore, the conductive plate may be comprised of a core member <NUM>' made of an insulating material and a cover member <NUM>' made of a conductive material and configured to cover the core member <NUM>' as shown in <FIG>, for example. The annular core member <NUM>' has a thin overhang portion <NUM>'F provided on an outer peripheral edge portion. The cover member <NUM>' comprises a disk portion <NUM>'A that covers the other end surface of the core member <NUM>' facing the diaphragm <NUM>, an outer peripheral edge portion <NUM>'C continued to the disk portion <NUM>'A and configured to cover an outer peripheral portion of the overhang portion <NUM>'F of the core member <NUM>', and a fixing portion <NUM>'B continued to the outer peripheral edge portion <NUM>'C and fixed to one of end surfaces of the overhang portion <NUM>'F of the core member <NUM>' by swage processing. An end surface around an inner peripheral edge portion of the core member <NUM>' of the conductive plate is adhered to the inner peripheral surface of the sensor housing <NUM>. At that time, as shown in <FIG>, predetermined clearances are formed between the fixing portion <NUM>'B of the cover member <NUM>' in the conductive plate and the inner peripheral surface of the sensor housing <NUM>, as well as between the outer peripheral surface of the sensor chip <NUM> and an inner peripheral edge portion <NUM>'a of the cover member <NUM>' in the conductive plate as well as an inner peripheral surface of the core member <NUM>', thus preventing the sensor housing <NUM> from coming into contact with the cover member <NUM>'.

The shielding member <NUM> may be formed from a conductive metal material such as stainless steel, copper, and aluminum, for example. Alternatively, the shielding member <NUM> may be formed from an insulating material such as resin, glass, and ceramic with one of its surface layers being formed and integrated with a conductive metallic film formed by adhesion, vapor deposition, sputtering, plating, and the like. That is to say, the shielding member <NUM> is supported by the sensor housing <NUM> set to the same electric potential as a primary side electric potential by using an insulator (the insulating layer of the conductive plate <NUM>).

The shielding member <NUM> is designed to entirely cover the one end surface of the sensor chip <NUM> while providing a predetermined clearance and thus to block an electric field undesirable for a signal processing electronic circuit unit of the sensor chip <NUM>. A pair of fixing end portions of the shielding member <NUM> and the conductive plate <NUM> are joined to and conducted with one another through conductive surfaces. The one end surface of the conductive plate <NUM> being the conductive surface is joined to and conducted with one or more of the group of input-output terminals 54ai, e.g. a zero (V) group of input-output terminals 54ai through the bonding wire Wi. According to this configuration described above, the electric potentials of the shielding member <NUM> and the conductive plate <NUM> are set to the same electric potential as the electric potential of the electronic circuit mounted in the sensor chip <NUM>.

Accordingly, as a consequence of disposing the shielding member <NUM> having the same electric potential as that of the signal processing electronic circuit unit of the sensor chip <NUM> between the diaphragm <NUM> and the one end surface of the sensor chip <NUM>, an electric field to act on the sensor chip <NUM>, which occurs due to a potential difference between the diaphragm <NUM> having the same electric potential as that of the primary power supply (not shown) of the unit and the control circuit (not shown) side, is blocked by the shielding member <NUM>. Moreover, since the electric potential of the shielding member <NUM> and the electric potential of the sensor chip <NUM> are set to the same electric potential, no electric field occurs therebetween. For this reason, because the potential difference that occurs between the sensor chip <NUM> and the diaphragm <NUM> does not act on the sensor chip <NUM>, it is possible to prevent an effect on the electronic circuit in the sensor chip <NUM>.

<FIG> partially shows the essential parts of the pressure sensor applying still another example of the shield structure for a pressure sensor according to the present invention.

In the example shown in <FIG>, the four fixing end portions of the cap-shaped shielding member <NUM> are brought close to the outer peripheral portion of the sensor chip <NUM> on the end surface of the disk conductive plate <NUM> and are joined to the end surface. Instead, an example shown in <FIG> is designed such that a shielding plate <NUM>' is joined to an end surface of a chip mounting member <NUM>' facing the liquid sealing chamber <NUM>.

The sensor chip <NUM> is adhered to one end portion of the chip mounting member <NUM>' located on the inside of the liquid sealing chamber <NUM> through the adhesive layer <NUM>, for example. As shown in <FIG>, the external size of the sensor chip <NUM> having the substantially rectangular shape is set smaller than a diameter of the chip mounting member <NUM>'. The chip mounting member <NUM>' is connected to and conducted with one or more of the group of input-output terminals 40ai, e.g. the zero (V) input-output terminal through the bonding wire Wi, for example.

The shielding plate <NUM>' serving as the electric field blocking member is provided between the one end surface of the sensor chip <NUM> and the diaphragm <NUM> in the liquid sealing chamber <NUM>. The shielding plate <NUM>' is configured to block the electric field undesirable for the signal processing electronic circuit unit of the sensor chip <NUM>. The shielding plate <NUM>' may be formed from a conductive metal material such as stainless steel, copper, and aluminum, for example. Alternatively, the shielding plate <NUM>' may be formed from an insulating material such as resin, glass, and ceramic with one of its surface layers being formed and integrated with a conductive metal film formed by adhesion, vapor deposition, sputtering, plating, and the like.

Fixing end portions of the strip-shaped shielding plate <NUM>' are brought close to the outer peripheral portion of the sensor chip <NUM> at one end portion of the chip mounting member <NUM>', and are joined to the end portion and conducted with the end portion. According to this configuration, the electric potentials of the shielding plate <NUM>' and the chip mounting member <NUM>' are set to the same electric potential as the electric potential of the electronic circuit mounted in the sensor chip <NUM>.

A predetermined clearance is formed between the one end surface of the sensor chip <NUM> and a portion of the shielding plate <NUM>' facing the one end surface of the sensor chip <NUM>. Note that an external size and a width dimension of the shielding plate <NUM>' may be appropriately set according to the size of the signal processing electronic circuit unit of the sensor chip <NUM> so as to block the electric field undesirable for the signal processing electronic circuit unit of the sensor chip <NUM>.

Further, in this case, the group of input-output terminals 40ai and the bonding wires Wi are connected to the chip mounting member <NUM>'. However, without limitation to this example, the group of input-output terminals 40ai and the bonding wires Wi may be connected directly to the shielding member <NUM>'.

Accordingly, as a consequence of disposing the shielding plate <NUM>' having the same electric potential as that of the signal processing electronic circuit unit of the sensor chip <NUM> between the diaphragm <NUM> and the sensor chip <NUM>, an electric field to act on the sensor chip <NUM>, which occurs due to the potential difference between the diaphragm <NUM> having the same electric potential as that of the primary power supply (not shown) of the unit and the control circuit (not shown) side, is blocked by the shielding plate <NUM>'. Moreover, since the electric potential of the shielding plate <NUM>' and that of the sensor chip <NUM> are set to the same electric potential, no electric field occurs therebetween. For this reason, because the potential difference that occurs between the sensor chip <NUM> and the diaphragm <NUM> does not act on the sensor chip <NUM>, it is possible to prevent an effect on the electronic circuit in the sensor chip <NUM>.

Claim 1:
A pressure sensor comprising:
a sensor unit including a housing (<NUM>), a sensor chip (<NUM>) for detecting a pressure and sending a detection output signal, a chip mounting member (<NUM>) supporting the sensor chip (<NUM>), a diaphragm (<NUM>) supported by a lower end surface of the housing (<NUM>) for partitioning a liquid sealing chamber (<NUM>), in which the sensor chip (<NUM>) is placed, from a pressure chamber (28A) facing the liquid sealing chamber (<NUM>), and a group of input-output terminals (40ai) supported by a hermetic glass (<NUM>) and electrically connected to the sensor chip (<NUM>); the housing (<NUM>), the hermetic glass (<NUM>), the chip mounting member (<NUM>), and the diaphragm (<NUM>) forming the liquid sealing chamber (<NUM>); and
an electric field blocking member (<NUM>) placed between one end surface of the sensor chip (<NUM>) in the liquid sealing chamber (<NUM>) and the diaphragm (<NUM>), and for blocking an electric field acting on a signal processing electronic circuit unit of the sensor chip (<NUM>),
wherein the electric potential of the electric field blocking member (<NUM>) is set to the same electric potential as that of the electronic circuit of the sensor chip (<NUM>),
characterized in that
the electric field blocking member (<NUM>) is strip-shaped and comprises a trench-shaped portion (48A) facing the one end surface of the sensor chip (<NUM>) and passing immediately above a central part of the sensor chip (<NUM>) with a predetermined clearance, and first and second fixing portions (48B, 48C) continued to both end portions of the trench-shaped portion (48A), and
an oil filling pipe (<NUM>) is press-fitted into a hole (48b) in the first fixing portion (48B), the group of input-output terminals (40ai) projecting from the end surface of the hermetic glass (<NUM>) are inserted into holes (48f, 48d) and a notch portion (48e) of the second fixing portion (48C), the electric field blocking member (<NUM>) is electrically connected to one of the group of input-output terminals (40ai), and the first and second fixing portions (48B, 48C) are supported on an end surface of the hermetic glass (<NUM>).