JP6715218B2 - Pressure detector - Google Patents

Description

The present invention relates to a pressure detecting device.

2. Description of the Related Art In order to respond to the environment of automobiles and improve fuel efficiency, the adoption of a hydraulic system that generates hydraulic pressure by an electric motor, a fuel injection system that injects fuel with pressure, and the like are expanding. In these systems, a pressure sensor is provided to detect the pressure. Generally, a pressure sensor for detecting oil pressure (hereinafter, referred to as a pressure sensor) is housed in a metal casing in order to ensure strength reliability, such as hydraulic oil or liquid fuel to be measured. It is attached to the metal pipe through which the pressure medium flows by screwing. The metal pipe is fixed to a structure having a body GND potential, such as an automobile body or an engine. Therefore, the potential of the metal housing of the pressure sensor becomes the body GND potential as in the metal pipe.

The pressure sensor is provided with a connector terminal for connecting to an electronic control unit (ECU: Electronic Control Unit) mounted on a vehicle. If the human body touches the connector terminals of the pressure sensor in an environment where the antistatic measures against the human body are not adequately applied, such as when manufacturing a pressure sensor, electrostatic discharge (ESD: ElectroStatic Discharge) from the human body to the pressure sensor may occur. Occasionally, a high voltage may be applied to the pressure sensor. The detection element for detecting the pressure in the pressure sensor is arranged with an insulating layer between the pressure sensor and the metal case. This corresponds to electrically connecting a relatively large parasitic capacitance between the detection element and the metal casing. Therefore, when a high voltage due to ESD is applied to the connector terminal of the pressure sensor when the potential of the metal housing is the body GND potential as described above, electric charges flow from the pressure sensor into the parasitic capacitance, and the parasitic capacitance is reduced. Be charged. At this time, if a current exceeding the permissible current flows through a processing circuit on the way, the processing circuit may be destroyed.

The techniques described in Patent Documents 1 and 2 are known as ESD countermeasures for solving the above problems. In Patent Document 1, a terminal connected to a control circuit board is extended, and a protrusion is further formed on the terminal to form a discharge gap between the control circuit board and a body GND potential housing. An electronic device is disclosed. Further, in Patent Document 2, by devising the shape of the metal housing on which the circuit board is installed and bringing a part of the GND terminal close to the protruding portion of the metal housing, a discharge occurs between the metal housing and the GND terminal. A vehicle-mounted electronic device having a gap is disclosed.

Patent No. 4577276 Patent No. 5841898

In the techniques described in Patent Documents 1 and 2, the discharge gap is formed by devising the shape of the terminal structure and the metal casing, and the high voltage due to ESD is released to the GND potential. Therefore, there is a problem that the number of parts and the number of processing steps increase, resulting in an increase in cost.

A pressure detection device according to the present invention includes a metal housing having a deformable portion that is deformed by a pressure received from a pressure medium, a detection element that detects the pressure by detecting the deformation of the deformed portion, and the detection element and an electrical element. A first lead frame connected to the first lead frame, a second lead frame different from the first lead frame, and a structure for holding the first lead frame and the second lead frame. An insertion portion for inserting a connector terminal electrically connected to the detection element via the first lead frame is formed in the structure, and the insertion portion has the first portion. And a pressing terminal for pressing the connector terminal to come into contact with the first lead frame, and the second lead frame includes the pressing terminal and the metal housing. And a discharge terminal exposed from the structure at a position spaced apart from the structure by a predetermined distance.

According to the present invention, it is possible to improve the ESD resistance of the pressure sensor while avoiding an increase in cost.

It is a longitudinal section showing the composition of the pressure sensing device concerning one embodiment of the present invention. It is a figure which shows the external appearance of a connection member. It is a figure explaining capacitor formation by parasitic capacitance. It is a figure explaining the difference of the circuit operation at the time of ESD occurrence in the case where the present invention is applied and the case where it is not applied. It is a figure which shows the positional relationship of a lead frame and a metal housing. It is a figure which shows the example of a shape of a connection member at the time of comprising a parallel plate capacitor using an adhesive agent.

Hereinafter, embodiments for carrying out the present invention will be described.

FIG. 1 is a vertical cross-sectional view showing the configuration of a pressure detection device 1 according to an embodiment of the present invention. The pressure detecting device 1 is used by being mounted on an automobile, and includes a sensor element 2, a pressure port 3, a connector subassembly 5, a base member 6, a connecting member 7, a first lead frame 8, and a second lead frame. 9 is provided.

Above the pressure port 3, a rectangular diaphragm 3a that acts as a pressure receiving surface of the pressure medium to be measured is provided. The upper surface of the diaphragm 3a, that is, the surface opposite to the pressure receiving surface is a pedestal surface 3b on which the sensor element 2 is mounted. The pressure port 3 introduces a pressure medium such as hydraulic oil or liquid fuel to the pressure receiving surface of the diaphragm 3a. As a result, the diaphragm 3a is deformed according to the pressure of the pressure medium, and strain is generated. The sensor element 2 detects the amount of deformation of the diaphragm 3a, that is, the amount of strain, for example, by measuring the change in the resistance value according to the strain of the diaphragm 3a, and thereby detects the pressure of the pressure medium.

The pressure port 3 and the base member 6 are both made of metal such as SUS and are joined to each other by welding or the like. The connection member 7 is fixed on the base member 6 with an adhesive or the like. Below, the combination of the pressure port 3 and the base member 6 is referred to as a “metal housing”. Note that, instead of joining the pressure port 3 and the base member 6 into a metal housing, it is possible to use a metal housing in which the pressure port 3 and the base member 6 are integrally formed.

The connector subassembly 5 has connector terminals 5a. A harness (not shown) is connected to the connector terminal 5a. The pressure detection device 1 outputs the pressure detection result to the ECU by being connected to the ECU of the automobile through this harness. The connector subassembly 5 is integrally provided with a cover 11 for shielding the sensor element 2 and the like from the outside. The cover 11 has, for example, a hexagonal shape.

The connection member 7 is a structure for holding the first lead frame 8 and the second lead frame 9. The connection member 7 is formed with an insertion portion for inserting the connector terminal 5a. One end of the first lead frame 8 and one end of the second lead frame 9 are arranged in this insertion portion. On the other end side of the first lead frame 8, a bonding portion connected to the sensor element 2 by wire bonding using the wire 10 is provided. For the wire 10, for example, aluminum (Al) or gold (Au) is used. By inserting the connector terminal 5a into the insertion portion of the connecting member 7, the sensor element 2 is electrically connected to the ECU via the wire 10, the first lead frame 8, the connector terminal 5a, and the harness.

On the other end side of the second lead frame 9, a discharge terminal 9a for protecting the sensor element 2 by discharging a high voltage due to ESD when the high voltage is applied to the connector terminal 5a is provided. .. The discharge terminal 9a is exposed from the connecting member 7 at a position separated from the base member 6 forming the metal housing by a predetermined distance. When the connector terminal 5a is inserted into the insertion portion of the connecting member 7, the connector terminal 5a comes into contact with the second lead frame 9 and is electrically connected to the discharge terminal 9a. When a high voltage due to ESD is applied to the connector terminal 5a in this state, dielectric breakdown occurs between the discharge terminal 9a and the base member 6, and the applied high voltage is discharged from the discharge terminal 9a to the base member 6.

When assembling the pressure detection device 1, the connection member 7 incorporating the first lead frame 8 and the second lead frame 9 is arranged on the base member 6, and the bonding portion between the sensor element 2 and the first lead frame 8 is bonded. Are connected by wire 10. Then, in order to protect the sensor element 2 from foreign matters and the like, the silicone gel 12 is potted on the surface of the sensor element 2. The connector subassembly 5 and the metal housing are integrated by joining the cover 11 and the base member 6 by welding or the like with the connector terminal 5a inserted in the insertion portion of the connection member 7. Thereby, the pressure detection device 1 is configured.

The sensor element 2 is a pressure detection element having a one-chip structure in which a strain detection element and a processing circuit are integrally formed on a silicon substrate. Therefore, a circuit board for laying out the processing circuit is unnecessary. The output signal generated by the sensor element 2 in response to the pressure received by the diaphragm 3a passes through the wire 10, the first lead frame 8 and the connector terminal 5a, and is transmitted to the ECU by the harness.

Next, detailed shapes of the connecting member 7, the first lead frame 8, and the second lead frame 9 will be described with reference to FIG. FIG. 2 is a view showing the outer appearance of the connecting member 7 in which the first lead frame 8 and the second lead frame 9 are incorporated. In FIG. 2, the drawing on the left side is a projection view of the connecting member 7, and the drawing on the right side is a plan view.

As shown in FIG. 2, the connecting member 7 is formed with an insertion portion 7c. A connector contact portion 8b provided at one end side of the first lead frame 8 and a pressing terminal 9b provided at one end side of the second lead frame 9 are arranged in the insertion portion 7c. A bonding portion 8a for connecting the sensor element 2 to the sensor element 2 by wire bonding is provided on the other end side of the first lead frame 8, and the sensor element 2 is connected to the other end side of the second lead frame 9. A discharge terminal 9a is provided to protect from ESD.

Since the pressing terminal 9b has elasticity, when the connector terminal 5a is inserted into the insertion portion 7c, the pressing terminal 9b is deformed and presses the connector terminal 5a toward the connector contact portion 8b. Thus, the connector terminal 5a can be surely brought into contact with the connector contact portion 8b and the pressing terminal 9b, and the electrical connection between the connector terminal 5a and the first lead frame 8 and the second lead frame 9 can be secured.

Further, the connection member 7 is provided with an insertion guide 7b for performing positioning when inserting the connector terminal 5a into the insertion portion 7c. The position and the shape of the insertion guide 7b are formed so as to correspond to the position and the shape of a protrusion (not shown) provided on the connector subassembly 5. If the insertion guide 7b is not present, the position or orientation of the connector terminal 5a may be displaced when the connector terminal 5a is inserted into the insertion portion 7c, and the connector terminal 5a may not be accurately brought into contact with the connector contact portion 8b. Therefore, in the present embodiment, the insertion guide 7b is provided in the connection member 7, so that when the connector subassembly 5 is assembled, the insertion guide 7b fits with the protrusion of the connector subassembly 5 to position the connector terminal 5a. Is being done. By inserting the connector terminal 5a into the insertion portion 7c in the thus positioned state, the connector terminal 5a can be accurately brought into contact with the connector contact portion 8b.

Further, the connecting member 7 is provided with a mounting portion 7a on which electronic components such as a chip capacitor are mounted. The connector terminal 5a is press-molded into a shape that does not interfere with the electronic components mounted on the mounting portion 7a when it is inserted into the insertion portion 7c so as not to hinder the mounting of the electronic component on the mounting portion 7a. ing. As a result, the circuit board in the pressure detection device 1 can be eliminated. After mounting necessary electronic components, the mounting portion 7a is surface-protected by potting with the silicone gel 12 similarly to the sensor element 2 (see FIG. 1).

The pressing terminal 9b forms a spring for contacting the connector terminal 5a with the connector contact portion 8b in the insertion portion 7c as described above. At the time of molding the connecting member 7, the plurality of second lead frames 9 are integrated by the carrier, and after the completion of molding, a cutting process is performed to separate the second lead frames 9. At this time, the cut portion of each second lead frame 9 is exposed from the connection member 7 at a position separated from the contact surface of the connection member 7 with the base member 6 by a predetermined distance, and is used as the discharge terminal 9a. That is, in the second lead frame 9 incorporated in the connecting member 7, the discharge terminal 9a is automatically formed through the cutting process.

Next, the discharge terminal 9a, which is a feature of this embodiment, will be described below with reference to FIGS. 3 and 4.

FIG. 3 is a partially enlarged view of the pressure port 3 on which the sensor element 2 is mounted. As shown in FIG. 3, the sensor element 2 is bonded onto the pressure port 3 via a bonding agent 4. Note that, as described above, the sensor element 2 has a one-chip configuration in which the strain detection element and the processing circuit are integrally formed. The bonding agent 4 is, for example, an insulating material such as an inorganic adhesive, and is applied with a thickness extremely smaller than the area of the sensor element 2. Therefore, on the circuit including the sensor element 2, the junction between the sensor element 2 and the pressure port 3 with the bonding agent 4 sandwiched therebetween acts as a parasitic capacitance Cic having a relatively large capacitance.

FIG. 4 is a diagram for explaining the action of the discharge terminal 9a on the circuit having the above parasitic capacitance Cic. FIG. 4A shows a circuit schematic diagram when the discharge terminal 9a is not provided, and FIG. 4B shows a circuit schematic diagram when the discharge terminal 9a is provided. The ICs and protection circuits shown in these circuit schematic diagrams are circuits configured by electronic components mounted on the mounting portion 7a of the sensor element 2 and the connecting member 7.

When the human body touches the connector terminal 5a while the connector terminal 5a is inserted in the insertion portion 7c of the connection member 7 at the time of manufacturing the pressure detection device 1, the electric charge accumulated in the human body is discharged by the ESD, and the connector terminal A high voltage may be applied to 5a. At this time, in the case of FIG. 4A in which the discharge terminal 9a is not provided, charging from the human body through the connector terminal 5a, the protection circuit, the IC, and the parasitic capacitance CiC to the metal case of the body GND potential is performed. A path is formed. Therefore, most of the electric charges emitted from the human body toward the connector terminal 5a flow into the parasitic capacitance CiC having a relatively large capacitance. At that time, a high-voltage current flows through the IC, that is, the processing circuit of the sensor element 2, so that the resistance element and the like in the processing circuit may be burned by Joule heat, and the sensor element 2 may be destroyed. In order to avoid a malfunction of the processing circuit due to noise, a capacitance acting as a noise path may be provided between the wiring from the connector terminal 5a to the protection circuit and the metal case. At least a part of the electric charge flows into the parasitic capacitance CiC, so that the sensor element 2 may be destroyed in the same manner. However, when the high voltage applied to the connector terminal 5a is a negative voltage, the flow of charges is opposite to that in FIG.

On the other hand, in the case of FIG. 4B in which the discharge terminal 9a is provided, a discharge gap is formed between the discharge terminal 9a and the metal case. When the charge due to the ESD flows from the connector terminal 5a, the potentials of the protection circuit and the IC rise with respect to the GND potential of the metal case. When the potential gradient of the discharge gap reaches the dielectric breakdown level of air, the discharge gap is dielectrically broken down, and a discharge is generated from the discharge terminal 9a toward the metal casing. As a result, the electric charge discharged from the human body toward the connector terminal 5a flows into the metal casing from the discharge terminal 9a without passing through the IC. As a result, it is possible to prevent a high-voltage current from flowing through the IC and prevent the sensor element 2 from being destroyed. The discharge gap formed by the discharge terminal 9a is preferably provided closer to the connector terminal 5a than the protection circuit formed by the electronic components mounted on the mounting portion 7a, as shown in FIG. 4(b).

In the case of FIG. 4B, the dielectric breakdown level in the discharge gap can be adjusted by adjusting the distance between the discharge terminal 9a and the metal casing. In order to prevent the destruction of the sensor element 2 due to ESD, it is necessary to cause the dielectric breakdown of the discharge gap at a voltage level lower than the withstand voltage of the sensor element 2. Here, it is known that the dielectric breakdown of air generally occurs when the potential gradient E [V/m] is 3 [MV/m] or more.

Further, the tip shape of the discharge terminal 9a also greatly contributes to the voltage level at which the dielectric breakdown of the discharge gap occurs. Specifically, the sharper the tip of the discharge terminal 9a, the larger the potential gradient of the discharge gap, and the easier the discharge is due to the dielectric breakdown. Here, the discharge terminal 9a is formed on the second lead frame 9 by the cutting process after the connection member 7 is molded as described above. Therefore, the tip shape of the discharge terminal 9a is generally sharpened by cutting. Therefore, even at a relatively low voltage level, dielectric breakdown can occur in the discharge gap between the discharge terminal 9a and the metal casing, and the breakdown of the sensor element 2 can be prevented more reliably.

FIG. 5 is a diagram showing a positional relationship between the first lead frame 8 and the second lead frame 9 and the metal housing. In FIG. 5, in order to facilitate understanding of the positional relationship between the first lead frame 8 and the second lead frame 9 and the metal housing, the portion of the connector subassembly 5 excluding the tip portion of the connector terminal 5a and the connecting member 7 are connected. And are removed, and the external appearance of the pressure detection device 1 is shown by a front view.

In the pressure detection device 1 of the present embodiment, the lower surface of the first lead frame 8, that is, the surface on the base member 6 side and the upper surface of the base member 6 in the metal housing are connection members that are insulators. The resin and the adhesive 7 are sandwiched in between, and are arranged to face each other at a predetermined interval. As a result, a parallel plate capacitor having a parasitic capacitance Ct is formed between the first lead frame 8 and the metal casing in the section indicated by the broken line in FIG. As shown in FIG. 5, the parallel plate capacitor region is in contact with the connector terminal 5a on the electrical path more than the bonding portion 8a connected to the sensor element 2 and the mounting portion 7a on which the electronic component is mounted in the connecting member 7. It is preferably formed at a position close to the connector contact portion 8b. By providing Ct in parallel with the parasitic capacitance Cic, it becomes possible to shunt the charge of the ESD, and an effect of reducing the influence of Cic is expected.

Further, the second lead frame 9 is formed with a discharge terminal 9a and a pressing terminal 9b. As shown in FIG. 5, the discharge terminal 9a is arranged at a position different from the parallel plate capacitor region defined by the first lead frame 8 and spaced apart from the metal housing by a predetermined distance. In order to facilitate discharge, the tip shape of the discharge terminal 9a is sharp as described above. By doing so, unnecessary discharge from other than the discharge terminal 9a is eliminated, and the sensor element 2 can be protected more reliably from the high voltage of ESD. Unlike the parallel plate capacitor area of the first lead frame 8, a resin or adhesive agent for the connecting member 7 is arranged between the tip of the discharge terminal 9a and the metal casing in order to avoid carbonization due to discharge. Preferably not.

It is desirable to set the distance between the discharge terminal 9a and the metal casing in the range of 0.1 [mm] to 0.6 [mm]. The reason for this will be described below.

In the case of an automobile component such as the pressure detection device 1, high voltage noise (surge) generated from another automobile component having a large inductance may be input. Even when a surge voltage of about several hundred [V] is input, it is necessary to maintain a certain distance so as to ensure insulation between the discharge terminal 9a and the metal casing and prevent a conductive state. ..

As described above, it is known that the dielectric breakdown of air generally occurs when the potential gradient E [V/m] is 3 [MV/m] or more. Here, the value of the surge voltage generally assumed in the surge test is about 300 [V]. Applying these values to the expression of the potential gradient E [V/m], that is, E=V/d (where V: voltage [V], d: distance between electrode plates [m]), the discharge terminal 9a is obtained. The minimum distance between metal housings is calculated to be 0.1 [mm].

On the other hand, in order to prevent the sensor element 2 from being damaged by ESD, as described above, it is necessary to cause the dielectric breakdown of the discharge gap at a voltage level lower than the withstand voltage of the sensor element 2. Here, the withstand voltage required for the sensor element 2 is, for example, 2 [kV], which is one of the standard values of the ESD withstand test in the human body model. Therefore, it is necessary to set the distance between the discharge terminal 9a and the metal casing so that the dielectric breakdown of the discharge gap occurs reliably at a voltage lower than the standard value and the discharge is performed from the discharge terminal 9a.

When the voltage level is 1.8 [kV] or more as a value that allows for a margin with respect to the standard value 2 [kV], dielectric breakdown occurs between the discharge terminal 9a and the metal casing. In this case, when d=0.6 [mm] in the above formula of the potential gradient E [V/m], V=1.8 [kV] and the potential gradient E [V/m] is 3 [MV]. /M]. Therefore, the maximum distance between the discharge terminal 9a and the metal casing is calculated to be 0.6 [mm].

As described above, it is desirable that the distance between the discharge terminal 9a and the metal casing is set within the range of the lower limit value of 0.1 [mm] or more and the upper limit value of 0.6 [mm] or less. However, it is also possible to employ only one of these lower and upper limits. That is, when it is not necessary to consider the surge voltage, the distance between the discharge terminal 9a and the metal casing may be less than 0.1 [mm]. In addition, when the withstand voltage of the sensor element 2 is high, the distance between the discharge terminal 9a and the metal casing may be larger than 0.6 [mm].

When the connecting member 7 is made of a molding resin, there is a minimum thickness that can be arranged between the metal frame and the first lead frame 8 or the second lead frame 9 due to restrictions in molding. Therefore, by using a connecting member having a shape different from that of the connecting member 7, resin of the connecting member is prevented from being arranged between the first lead frame 8 and the second lead frame 9 and the metal housing (base member 6). The adhesive that joins the connecting member and the base member 6 may be used as the dielectric of the parallel plate capacitor.

FIG. 6 is a diagram showing an example of the shape of a connecting member when a parallel plate capacitor is formed by using an adhesive. In the connecting member 13 shown in FIG. 6A, the lower surface of the parallel plate region of the first lead frame 8, that is, the surface on the base member 6 side is exposed from the connecting member 13, and the first lead frame 8 is formed. Are attached to the connecting member 13. When the connecting member 13 to which the first lead frame 8 is attached is placed on the base member 6, the first lead is obtained from the bottom surface of the connecting member 13, that is, the surface of the connecting member 13 facing the metal housing (base member 6). A part of the frame 8, that is, a surface of the first lead frame 8 facing the base member 6 is exposed. In this state, the connecting member 13 is attached to the base member 6 with an insulating adhesive. However, as described above, in order to avoid carbonization of the adhesive due to discharge, the adhesive is not arranged between the discharge terminal 9a and the metal casing (base member 6). Then, the adhesive acts as a dielectric of the parallel plate capacitor, and a parasitic capacitance Ct is formed between the first lead frame 8 and the metal case. At this time, by controlling the amount of the adhesive and adjusting the thickness of the adhesive layer, it is possible to obtain a desired capacitance value in the parasitic capacitance Ct.

Moreover, you may use the connection member 14 shown in FIG.6(b). A wall portion 14a formed along the outer edge and a filling portion 14b surrounded by the wall portion 14a are provided on the bottom surface of the connection member 14. The filling portion 14b is recessed with respect to the bottom surface more than the wall portion 14a. Similar to the connecting member 13 shown in FIG. 6A, the connecting member 14 has a lower surface in the parallel plate region of the first lead frame 8, that is, a surface on the base member 6 side exposed from the connecting member 14. The first lead frame 8 is attached to the connecting member 14. When the connection member 14 to which the first lead frame 8 is attached is placed on the base member 6, the bottom surface of the wall portion 14a comes into contact with the metal housing (base member 6). At this time, the wall member 14a may be used for positioning when the connecting member 14 is attached to the metal housing. Further, a groove or a step corresponding to the protruding shape of the wall portion 14a is formed on the metal housing side, and the wall portion 14a is aligned with the groove or the step so that the connection member 14 is positioned. Good. In addition, a part of the first lead frame 8, that is, a surface of the first lead frame 8 facing the base member 6 is exposed from the surface of the filling portion 14b facing the metal housing (base member 6). Become. In this state, the filling portion 14b is filled with an insulating adhesive and the connecting member 14 is attached to the base member 6. However, also in this case, as described above, in order to avoid carbonization of the adhesive due to discharge, the adhesive is not arranged between the discharge terminal 9a and the metal casing (base member 6). Then, as in the case of the connecting member 13, the adhesive acts as a dielectric of the parallel plate capacitor, and a parasitic capacitance Ct is formed between the first lead frame 8 and the metal case. Since the thickness of the adhesive layer at this time is the height of the wall portion 14a, it is possible to suppress variation in the distance between the first lead frame 8 and the discharge terminal 9a and the metal housing. Therefore, by adjusting the height of the wall portion 14a, it is possible to accurately obtain a desired electrostatic capacitance value in the parasitic capacitance Ct and suppress variations in the discharge voltage. In addition, a part of the first lead frame 8 may not be exposed in the filling portion 14b.

Furthermore, when the connecting member 14 is attached to the metal housing, the metal housing may be arranged to protrude toward the first lead frame 8 side in the filling portion 14b with respect to the bottom surface of the wall portion 14a. For example, a table-shaped convex portion having a flat top is formed in the metal casing, and when the connecting member 14 is attached, the convex portion is inserted into the recessed portion of the filling portion 14b, thereby It is possible to realize various arrangements. Alternatively, as described above, a groove corresponding to the protruding shape of the wall portion 14a is provided in the metal casing, and the wall portion 14a is fitted into this groove, whereby the above arrangement can be realized. As a result, the metal casing and the first lead frame 8 can be arranged at a distance smaller than the minimum resin thickness due to the above-described restrictions at the time of molding, so that the parasitic capacitance Ct can be increased.

Similarly, when the connection member 14 is attached to the metal housing, the metal housing may be arranged to project toward the discharge terminal 9a side with respect to the bottom surface of the wall portion 14a. As a result, the metal casing and the discharge terminal 9a can be arranged at a distance smaller than the minimum resin thickness due to the above-described restrictions at the time of molding, so that the discharge voltage can be reduced.

Further, in order to improve the ESD resistance of the pressure detection device 1, it is also effective to reduce the electrostatic capacitance value of the parasitic capacitance Cic. Specifically, for example, by increasing the thickness of the bonding agent 4 that bonds the sensor element 2 to the pressure port 3, the capacitance value of the parasitic capacitance Cic can be reduced. Here, the parallel plate capacitor capacitance C[F] is C=ε·, where S[m ² ] is the area of the electrode plates, d[m] is the distance between the electrode plates, and ε[F/m] is the dielectric constant. It is represented by the formula S/d. From this equation, it can be seen that the parallel plate capacitor capacitance C decreases as the inter-electrode plate distance d increases. Therefore, the thickness of the bonding agent 4 is increased within a range that does not affect the strain detection performance of the sensor element 2 and the distance between the sensor element 2 and the pressure port 3 is increased to reduce the capacitance value of the parasitic capacitance CiC. It is possible to improve the ESD resistance of the pressure detection device 1.

According to the embodiment of the present invention described above, the following operational effects are achieved.

(1) The pressure detection device 1 includes a deformable portion that is deformed by the pressure received from the pressure medium, that is, a metal housing having a diaphragm 3a, a sensor element 2 that detects the pressure by detecting the deformation of the deformed portion, and a sensor element. 2, a first lead frame 8 electrically connected to the second lead frame 8, a second lead frame 9 different from the first lead frame 8, and a structure for holding the first lead frame 8 and the second lead frame 9, that is, a connection And a member 7. The connection member 7 is provided with an insertion portion 7c for inserting the connector terminal 5a electrically connected to the sensor element 2 via the first lead frame 8. A first lead frame 8 and a pressing terminal 9b for pressing the connector terminal 5a to bring it into contact with the first lead frame 8 are arranged in the insertion portion 7c. The second lead frame 9 is formed with a pressing terminal 9b and a discharge terminal 9a exposed from the connecting member 7 at a position separated from the metal housing by a predetermined distance. Since this is done, it is possible to improve the ESD resistance of the pressure detection device 1 that is a pressure sensor while avoiding an increase in cost.

(2) The first lead frame 8 has a connecting portion connected to the sensor element 2 by wire bonding, that is, a bonding portion 8a, and a connector contact portion 8b with which the connector terminal 5a pressed by the pressing terminal 9b contacts. An electronic component is connected on the electric path between the bonding portion 8a and the connector contact portion 8b. Since it did in this way, the noise tolerance of the pressure detection apparatus 1 can be improved.

(3) The connecting member 7, 13 or 14 is joined to the metal housing with an adhesive. This adhesive is not arranged between the discharge terminal 9a and the metal casing. Since it did in this way, carbonization of the adhesive agent by discharge can be avoided and it can prevent that discharge terminal 9a and a metal case are electrically connected.

(4) The adhesive is an insulator, and the first surface of the first lead frame 8, that is, the surface on the side of the metal housing in the parallel plate region and the second surface of the metal housing, that is, the base member 6 The upper surface is arranged to face the upper surface with an adhesive agent sandwiched therebetween. Since it did in this way, a parasitic capacitance is produced between the 1st lead frame 8 and a metal case, and the noise resistance of the pressure detection device 1 which is a pressure sensor can be improved.

(5) The connection member 14 has a contact surface that contacts the metal housing, that is, the bottom surface of the wall portion 14a, and a filling portion 14b that is recessed with respect to the contact surface and that is filled with an adhesive. By using such a connecting member 14, the discharge voltage at which the discharge from the discharge terminal 9a is performed can be set to a desired voltage value by adjusting the height of the wall portion 14a.

(6) The predetermined distance between the discharge terminal 9a and the metal casing is preferably 0.1 mm or more. By doing so, it is possible to avoid conduction between the discharge terminal 9a and the metal casing due to the input of the surge voltage.

(7) Further, the predetermined distance between the discharge terminal 9a and the metal casing is preferably 0.6 mm or less. By doing so, it is possible to prevent the damage of the sensor element 2 by causing the dielectric breakdown between the discharge terminal 9a and the metal casing at the withstand voltage of the sensor element 2 or less.

(8) The metal casing includes the pressure port 3 for introducing the pressure medium into the deformable portion, and the base member 6 joined to the connecting member 7. Since it did in this way, the pressure detection apparatus 1 with high noise resistance can be comprised.

In the embodiment described above, the one-chip type sensor element 2 in which the strain detection element and the processing circuit are integrated has been described as an example, but the sensor element other than the one-chip type, that is, the strain gauge and the processing circuit is The present invention is similarly applicable to sensor elements formed on different substrates. In this case, in general, the strain gauge is arranged in the closest state to the metal casing in an insulated state, so that a parasitic capacitance having a large capacitance value is formed between the strain gauge and the metal casing. Therefore, when the charge due to the ESD flows through the processing circuit when flowing into the parasitic capacitance, the sensor element may be destroyed. Therefore, also in this case, the same measure as that of the embodiment is effective.

Further, although the pressure detection device 1 described in the embodiment is described as being mounted on an automobile and detecting the pressure of a pressure medium such as hydraulic oil or liquid fuel, the pressure detection device used for other purposes is also described. Similarly, the present invention can be applied. As long as the sensor element is disposed in close proximity to the metal housing in an insulated state and the metal housing is at the GND potential, the ESD resistance improvement of the present invention can be effectively applied to various pressure detection devices. Can be operated. For example, in a sensor that detects a load as strain, a large force is applied to the sensor, so that resin or the like cannot be used in the pressure receiving portion. Further, the pedestal of the sensor element also needs to be rigidly constructed. Therefore, the housing of such a sensor is inevitably made of metal and has a configuration similar to that of the pressure detection device 1 described in the embodiment. Therefore, by similarly applying the present invention, the ESD resistance can be improved. Can be planned.

As described above, the sensor element used in the sensor may be a one-chip type sensor element in which the strain detection element and the processing circuit are integrated, or they may be formed on different substrates. May be In any case, the same effects as those described in the embodiment can be obtained.

The pressure detection device to which the present invention is applied is not limited to the donut shape as described in the embodiments, and may have another shape. As long as the technical elements described above are incorporated, there is no problem with any shape.

As described above, by applying the present invention to the pressure detection device, it is possible to improve the ESD resistance without causing dissimilar metal bonding and without special processing. Further, since this structure does not use a chip capacitor, improvement in connection reliability, cost reduction, and space saving can be expected.

The embodiments and various modifications described above are merely examples, and the present invention is not limited to these contents unless the characteristics of the invention are impaired. Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other aspects that are conceivable within the scope of the technical idea of the present invention are also included within the scope of the present invention.

1 Pressure Detection Device 2 Sensor Element 3 Pressure Port 3a Diaphragm 3b Pedestal Surface 4 Bonding Agent 5 Connector Subassembly 5a Connector Terminal 6 Base Member 7 Connection Member 7a Mounting Part 7b Insertion Guide 7c Insertion Part 8 First Lead Frame 8a Bonding Part 8b Connector contact part 9 Second lead frame 9a Discharge terminal 9b Pressing terminal 10 Wire 11 Cover 12 Silicone gel

Claims (8)

A metal casing having a deformable portion that is deformed by the pressure received from the pressure medium,
A detection element for detecting the pressure by detecting the deformation of the deformable portion,
A first lead frame electrically connected to the detection element;
A second lead frame different from the first lead frame;
A structure for holding the first lead frame and the second lead frame,
In the structure, an insertion portion for inserting a connector terminal electrically connected to the detection element via the first lead frame is formed,
The first lead frame and a pressing terminal for pressing the connector terminal to make contact with the first lead frame are arranged in the insertion portion,
The pressure detection device in which the pressing terminal and the discharge terminal exposed from the structure at a position separated from the metal housing by a predetermined distance are formed on the second lead frame. The pressure detection device according to claim 1,
The first lead frame has a connection portion connected to the detection element by wire bonding, and a contact portion with which the connector terminal pressed by the pressing terminal contacts.
A pressure detection device in which an electronic component is connected on an electric path between the connection portion and the contact portion. The pressure detection device according to claim 1 or 2,
The structure is bonded to the metal housing with an adhesive,
The pressure detecting device in which the adhesive is not arranged between the discharge terminal and the metal casing. The pressure detection device according to claim 3,
The adhesive is an insulator,
The pressure detection device in which the first surface of the first lead frame and the second surface of the metal housing are arranged to face each other with the adhesive in between. The pressure detection device according to claim 4,
The pressure detecting device, wherein the structure has a contact surface that is in contact with the metal housing, and a filling portion that is recessed with respect to the contact surface and that is filled with the adhesive. The pressure detection device according to any one of claims 1 to 5,
The pressure detecting device, wherein the predetermined interval is 0.1 mm or more. The pressure detection device according to any one of claims 1 to 6,
The said predetermined space|interval is a pressure detection apparatus which is 0.6 mm or less. The pressure detection device according to any one of claims 1 to 7,
The pressure detection device, wherein the metal casing includes a pressure port for introducing the pressure medium into the deformable portion, and a base member joined to the structure.

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