Patent Description:
Conventionally, a pressure sensor in which a strain detecting element is formed on a stem is known (see, for example, <CIT>). Specifically, in this pressure sensor, one end of the stem is an opening to introduce a pressure medium, and the other end is a diaphragm that can be deformed according to the pressure of the pressure medium. A strain detecting element having a gauge resistance whose resistance value changes when deformed is formed on the diaphragm.

Document <CIT> discloses a sensor having polysilicon strain-sensing elements on a metal diaphragm. A thick-film insulating layer covers the metal diaphragm, and thin-film polysilicon resistive elements are formed on the thick-film insulating layer. Thick-film conductors are formed on the thick-film insulating layer and contact the thin-film polysilicon resistive elements to form electrical interconnects to the resistive elements. A passivation layer overlies the thin-film polysilicon resistive elements and the thick-film conductors.

Document <CIT> discloses a method for fabricating a thin film piezoresistive sensor by a process that includes plasma enhanced chemical vapor deposition and selective laser recrystallization. An insulating dielectric layer is first vapor deposited on a flexible substrate. A layer of highly resistive, doped semiconductor material is then deposited over the insulating layer. Metal contacts for the as yet to be formed piezoresistive sensor are deposited at selected locations on the semiconductor layer. Optionally, a passivating layer is then deposited over the semiconductor layer. Through selective laser annealing, portions of the semiconductor layer between selected metal contacts are recrystallized to a preselected resistance to form piezoresistive sensor elements. The non-annealed portions of the semiconductor layer remain to act as insulators between adjacent formed sensor elements.

Document <CIT> discloses a semiconductor pressure transducer having a polycrystalline silicon diaphragm, wherein polycrystalline silicon is vapor deposited on an etch resistant layer covering a surface of a wafer or base, preferably monocrystalline silicon.

Document <CIT> discloses a polycrystalline pressure sensor which is formed by depositing polycrystalline silicon piezoresistors on a polycrystalline sensing diaphragm. The piezoresistors are arranged in a wheatstone bridge configuration.

By the way, in recent years, it has been desired to further improve a reliability of the pressure sensor as described above. It is an object of the present disclosure to provide a pressure sensor capable of improving reliability.

The object is solved by the features of independent claim <NUM>. The dependent claims relate to preferred embodiments of the invention.

According to the invention, the low doping layer is arranged between the insulating film and the strain detecting element. Therefore, an amorphous layer formed between the low doping layer and the strain detecting element can be made smaller than the case where the strain detecting element is directly formed on the insulating film. Further, the amorphous layer is formed between the low doping layer and the insulating film, but the influence of the delayed elasticity of the amorphous layer is alleviated by the low doping layer, and is less likely to be propagated to the strain detecting element. Further, the low doping layer is composed of a material having a higher electrical resistivity than polysilicon. Therefore, even if an amorphous layer is formed between the low doping layer and the insulating film and the low doping layer is affected by the delayed elasticity of the amorphous layer, the influence on the strain detecting element can be reduced. Therefore, it is possible to suppress the change in the characteristics of the strain detecting element, and improve the reliability of the pressure sensor.

A reference numeral in parentheses attached to each component or the like indicates an example of correspondence between the component or the like and specific component or the like described in an embodiments below.

In the following examples and embodiments, the same or equivalent parts are denoted by the same reference numerals.

A pressure sensor of a first example useful for understanding the invention will be described with reference to the drawings. The pressure sensor of the present example is preferably used for detecting a combustion pressure of an internal combustion engine, for example.

First, an overall configuration of the pressure sensor in the present example will be described. As shown in <FIG> and <FIG>, the pressure sensor includes a stem <NUM>, a strain detecting element <NUM>, a housing <NUM>, a circuit board <NUM>, a connector case <NUM>, and the like.

As shown in <FIG>, the stem <NUM> has an opening <NUM> formed on one end side and a pressure introduction hole <NUM> extending from the opening <NUM> toward the other end side, and is formed in a bottomed cylindrical shape. The stem <NUM> has a diaphragm <NUM> that can be deformed according to pressure on the other end side. That is, the stem <NUM> is formed with the pressure introduction hole <NUM> so that the diaphragm <NUM> is formed on the other end side. Then, on the stem <NUM>, as shown in <FIG>, a strain detecting element <NUM> is arranged on the diaphragm <NUM> via an insulating film <NUM>.

In <FIG>, a lower side of a paper surface corresponds to the one end side, and an upper side of the paper surface corresponds to the other end side. Further, in the following, similarly, each member will be described with the lower side of the paper surface as the one end side and the upper side of the paper surface as the other end side. In other words, as will be described later, the pressure sensor is configured by integrating the stem <NUM>, the housing <NUM>, and the connector case <NUM>. Therefore, in the pressure sensor, the stem <NUM> side is the one end side, and the connector case <NUM> side is the other end side.

As shown in <FIG>, the stem <NUM> is formed with a threaded portion <NUM> that can be screwed to a member to be attached such as a fuel pipe on an outer wall surface on the opening <NUM> side. Further, a length of the outer wall surface of the stem <NUM> in a circumferential direction centered on an axial direction is changed between one end portion and the other end portion. Specifically, the stem <NUM> has a circumferential length on the outer wall surface on the other end side shorter than the circumferential length on the outer wall surface on the one end side. Then, as will be described later, the stem <NUM> is joined to the housing <NUM> by a welded portion <NUM> at a portion where the circumferential length of the outer wall surface changes.

As shown in <FIG>, the strain detecting element <NUM> is arranged on the diaphragm <NUM> of the stem <NUM> via the insulating film <NUM>. The strain detecting element <NUM> has a gauge resistor <NUM> whose resistance value changes according to deformation, and a wiring layer and a pad portion (not shown). Then, in the strain detecting element <NUM>, the gauge resistors <NUM> are connected via the wiring layer so as to form a bridge circuit, and the pad portion is arranged on the wiring layer so that each gauge resistor <NUM> is connected to an external circuit. Further, a protective film <NUM> covering the strain detecting element <NUM> is formed on the diaphragm <NUM> of the stem <NUM>. A protective member <NUM> is arranged on the protective film <NUM>.

The protective film <NUM> is formed with an opening for exposing the pad portion in a cross section different from that in <FIG>. As shown in <FIG>, in the strain detecting element <NUM>, a pad portion is connected to the circuit board <NUM> via a bonding wire <NUM>. Further, in the present example, the insulating film <NUM> is made of a silicon oxide film or the like. The gauge resistor <NUM> and the wiring layer are made of boron-doped polysilicon. The pad portion is made of an electrode film such as gold or an alloy containing gold as a main component. The protective film <NUM> is made of a silicon nitride film or the like. The protective member <NUM> is made of a gel such as a silicone gel.

As shown in <FIG>, the housing <NUM> has a tubular shape in which one end side and the other end side are opened, and a distance between the facing inner wall surfaces on the one end side is shorter than the distance between the facing inner wall surfaces on the other end side. Specifically, in the housing, a step portion <NUM> is formed between one end side and the other end side, and the distance between the facing inner wall surfaces is changed by the step portion <NUM>. As will be described later, the step portion <NUM> is formed so as to form a mounting portion <NUM> on which the circuit board <NUM> can be mounted.

The housing <NUM> is joined to the stem <NUM> via a welded portion <NUM> in a state where the diaphragm <NUM> of the stem <NUM> is located on the other end side with respect to the step portion <NUM>. That is, the dimensions and the like of the housing <NUM> and the stem <NUM> are designed so that the diaphragm <NUM> of the stem <NUM> projects toward the other end from the step portion <NUM>.

The welded portion <NUM> between the stem <NUM> and the housing <NUM> is formed by laser welding, electron beam welding, or the like. Further, a portion of the housing <NUM> on the other end side with respect to the step portion <NUM> has a hexagonal outer shape or the like so that a mounting jig such as a spanner can be attached. The mounting portion <NUM> has a hexagonal outer shape in a planar shape in accordance with the outer shape of the above portion.

The circuit board <NUM> is composed of a printed circuit board or the like, and has a hexagonal outer shape in accordance with the planar outer shape of the mounting portion <NUM>. Although detailed description will not be given here, on the circuit board <NUM>, an element land connected to a strain detecting element <NUM> (not shown), an electrode portion land connected to the electronic component <NUM> described later, an external connection land connected to a terminal member <NUM> described later, a predetermined wiring pattern, and the like are formed on a surface 50a side. The circuit board <NUM> is arranged on the mounting portion <NUM> via a joining member <NUM> so that a back surface 50b faces the mounting portion <NUM> of the housing <NUM>.

Specifically, the circuit board <NUM> is formed with a through hole <NUM> penetrating between a front surface 50a and the back surface 50b in a substantially central portion thereof, and are arranged so that the other end side of the stem <NUM> is located in the through hole <NUM>. The circuit board <NUM> is electrically connected to the strain detecting element <NUM> formed on the stem <NUM> via the bonding wire <NUM>. Further, an electronic component <NUM> is mounted on the circuit board <NUM>.

In the present example, the electronic component <NUM> is composed of a QFN (abbreviation of quadflatnon-leaded package) or the like in which a circuit chip in which an amplifier circuit, a correction circuit, or the like is formed is housed in a case and an electrode portion is formed in the case. Then, the electronic component <NUM> is mounted on the electrode portion land formed on the circuit board <NUM> via a solder <NUM>.

A connector case <NUM> has a columnar shape formed by molding a resin such as PPS (that is, polypropylene sulfide) or PBT (that is, polybutylene terephthalate). The connector case <NUM> has a recess <NUM> formed on one end side and an opening <NUM> formed on the other end side.

The connector case <NUM> has a terminal <NUM> for electrical connection with an external circuit. The terminal <NUM> is arranged after the connector case <NUM> is molded, for example, but may be integrally molded with the connector case <NUM> by insert molding or the like.

The terminal <NUM> is provided in the connector case <NUM> so that one end thereof is exposed in the recess <NUM> and the other end is exposed from the opening. In the present example, one end of the terminal <NUM> is bent toward a terminal member <NUM> so that it can come into contact with a contact portion 852a of the terminal member <NUM>, which will be described later.

Further, the connector case <NUM> is formed with a mounting hole <NUM> for arranging the terminal member <NUM> on one end side. Then, the terminal member <NUM> that comes into contact with the circuit board <NUM> while being in contact with the terminal <NUM> is arranged in the mounting hole <NUM>.

The terminal member <NUM> is configured to include a base portion <NUM>, a movable body <NUM>, and an urging member <NUM>. The base portion <NUM> and the movable body <NUM> are each formed by punching or bending a conductive metal member, and have a U-shaped cross section having a pair of side surfaces and a bottom surface. Further, although not particularly shown, the base portion <NUM> has a convex portion formed on the side surface, and the movable body <NUM> has a slide groove formed on the side surface. Then, the base portion <NUM> and the movable body <NUM> are assembled in a state in which the convex portions are inserted into the slide groove with the bottom surfaces facing each other and the movable body <NUM> is slidable with respect to the base portion <NUM>.

Further, although not particularly shown, the base portion <NUM> is formed with a locking portion for fixing on the side surface. The movable body <NUM> is provided with a contact portion 852a bent on one side surface.

The urging member <NUM> is formed of a coil spring or the like, and is arranged between the base portion <NUM> and the movable body <NUM> so that one end of the urging member <NUM> presses a bottom surface of the movable body <NUM> and the other end thereof presses a bottom surface of the base portion <NUM>.

Then, such a terminal member <NUM> is press-fitted into the mounting hole <NUM> formed in the connector case <NUM>, and is held in the mounting hole <NUM> by the locking portion formed in the base portion <NUM> biting into the connector case <NUM>. The base portion <NUM> is held in the mounting hole <NUM>, and the movable body <NUM> is in a slidable state with respect to the base portion <NUM>. Further, the terminal member <NUM> is held in the mounting hole <NUM> so that the contact portion 852a comes into contact with the terminal <NUM>. More specifically, the terminal member <NUM> is held in the mounting hole <NUM> so that the contact portion 852a is maintained in contact with the terminal <NUM> even when sliding.

The connector case <NUM> is integrated with the housing <NUM> by inserting one end side into the other end side of the housing <NUM> and crimping a claw portion <NUM> formed on the housing <NUM>. At this time, the connector case <NUM> is inserted so that the terminal member <NUM> comes into contact with the external connection land formed on the circuit board <NUM>. As a result, the terminal <NUM> is electrically connected to the strain detecting element <NUM> through the terminal member <NUM>, the circuit board <NUM>, the bonding wire <NUM>, and the like.

A sealing member <NUM> such as a gasket is arranged between one end of the connector case <NUM> and the mounting portion <NUM> of the housing <NUM>. Then, the sealing member <NUM> is crushed to seal the internal space.

The above is the basic configuration of the pressure sensor in the present example. In the present example, the stem <NUM> has a first stem <NUM> and a second stem <NUM>, which are welded together.

Specifically, the first stem <NUM> has a bottomed tubular shape having an open end on one end side and the diaphragm <NUM> on the other end side. The second stem <NUM> has respectively an open end on one end side and the other end side, and has a tubular shape having the threaded portion <NUM> on the one end side. That is, the first stem <NUM> constitutes the other end side of the stem <NUM>, and the second stem <NUM> constitutes the one end side of the stem <NUM>. The housing <NUM> is welded to the second stem <NUM>.

Laser welding, electron beam welding, or the like is performed on one end side of the first stem <NUM> and the other end side of the second stem <NUM> from an outer wall surface side, and the first stem <NUM> and the second stem <NUM> are joined. That is, the first stem <NUM> and the second stem <NUM> are joined by the welded portion <NUM>. The welded portion <NUM> may or may not be formed so as to reach the inner wall surface of the first stem <NUM>.

Further, the second stem <NUM> has a thin-walled portion <NUM> on one end side with respect to a portion where the welded portion <NUM> with the first stem <NUM> is formed, and the thin-walled portion <NUM> has a thinner thickness between the inner wall surface and the outer wall surface than the portion where the welded portion <NUM> is formed. That is, the second stem <NUM> has a thin-walled portion <NUM> having a lower rigidity than the portion where the welded portion <NUM> is formed on one end side with respect to the portion where the welded portion <NUM> with the first stem <NUM> is formed.

Further, in the present example, since the diaphragm <NUM> is arranged on the first stem <NUM>, the first stem <NUM> is made of a material having higher strength than the second stem <NUM>. For example, the first stem <NUM> is formed using SUS630 and the second stem <NUM> is formed using SUS430.

Further, the second stem <NUM> is formed with an alignment portion <NUM> inserted into the first stem <NUM> on the other end side.

Such a pressure sensor is attached to a fuel supply pipe or the like via, for example, the threaded portion <NUM> formed on the stem <NUM>. Then, in the pressure sensor, when a pressure medium in a fuel supply pipe is introduced into the pressure introduction hole <NUM>, the strain detecting element <NUM> outputs a detection signal corresponding to the pressure medium. Then, the pressure sensor transmits a detection signal to the external circuit via the bonding wire <NUM>, the circuit board <NUM>, the terminal member <NUM>, the terminal <NUM>, and the like. As a result, the pressure of the pressure medium is detected.

As described above, the stem <NUM> has a configuration including the first stem <NUM> and the second stem <NUM>. Therefore, a manufacturing process can be simplified as compared with the case where the entire stem <NUM> is integrally formed by cutting, cold forging, or the like.

Further, the second stem <NUM> has the thin-walled portion <NUM> on one end side with respect to the portion where the welded portion <NUM> with the first stem <NUM> is formed. Therefore, the life of the welded portion <NUM> against fatigue failure can be improved, and a reliability of the pressure sensor can be improved.

That is, in a case where the second stem <NUM> is not formed with the thin-walled portion <NUM>, as shown in <FIG>, when the pressure medium is introduced into the pressure introduction hole <NUM>, the stem <NUM> has a deformation fulcrum at the welded portion <NUM>. In this case, tensile stress is applied to the welded portion <NUM>.

On the other hand, in the present example, as shown in <FIG>, when the pressure medium is introduced into the pressure introduction hole <NUM>, the fulcrum of the deformation of the stem <NUM> becomes the thin-walled portion <NUM>. In this case, compressive stress is applied to the welded portion <NUM>. Therefore, in the present example, the life of the welded portion <NUM> against fatigue fracture can be improved.

Further, in the present example, the second stem <NUM> is formed with the alignment portion <NUM> that is inserted into the first stem <NUM>. Therefore, as shown in <FIG>, when the first stem <NUM> and the second stem <NUM> are welded and joined, it is possible to suppress an occurrence of misalignment between the first stem <NUM> and the second stem <NUM>, and it is possible to prevent a workmanship of the welded portion103 from varying from portion to portion. Therefore, it is possible to suppress that the compressive stress applied to the welded portion <NUM> varies from portion to portion, and it is possible to suppress the occurrence of local stress concentration. As a result, the life of the welded portion <NUM> against fatigue failure can be further improved.

Further, in the present example, the first stem <NUM> is made of a material having higher strength than the second stem <NUM>. Therefore, for example, the strength of the diaphragm <NUM> can be increased and the destruction of the diaphragm <NUM> can be suppressed as compared with the case where the first stem <NUM> is made of the same material as the second stem <NUM>.

Further, the second stem <NUM> is formed with the alignment portion <NUM>. Therefore, when the first stem <NUM> and the second stem <NUM> are welded and joined, the alignment portion <NUM> may be inserted into the first stem <NUM>, so that the manufacturing process can be simplified.

A first embodiment will be described. In the present embodiment, a low doping layer is arranged between the strain detecting element <NUM> and the insulating film <NUM> as compared with the first example. Descriptions of the same configurations and processes as those of the first example will not be repeated hereinafter.

In the present embodiment, as shown in <FIG>, a low doping layer <NUM> is formed on the insulating film <NUM>. The low doping layer <NUM> has a higher electrical resistivity than the polysilicon constituting the strain detecting element <NUM> and has a higher crystallinity than the insulating film <NUM>. In the present embodiment, the low doping layer <NUM> is made of polysilicon in which the amount of boron doped is smaller than that of polysilicon constituting the strain detecting element <NUM>. For example, the low doping layer <NUM> is composed of polysilicon doped with <NUM>% less boron than the amount of boron doped in the polysilicon constituting the strain detecting element <NUM>. Then, the strain detecting element <NUM> is formed on the low doping layer <NUM>. That is, in the present embodiment, the low doping layer <NUM> is arranged between the strain detecting element <NUM> and the insulating film <NUM>.

Further, as shown in <FIG>, the strain detecting element <NUM> is connected so that the gauge resistor <NUM> forms a bridge circuit by the wiring layer <NUM>. Specifically, the wiring layer <NUM> has a connecting portion <NUM> and an extending portion <NUM>. The strain detecting element <NUM> is configured such that adjacent gauge resistors <NUM> are connected by the connecting portion <NUM> and the extending portion <NUM> is pulled out from the connecting portion <NUM>.

Further, the pad portion <NUM> is configured to have gold as described above, and is formed so as to be connected to each wiring layer <NUM>. In the present embodiment, the pad portion <NUM> is formed so as to be connected only to the extending portion <NUM>. In other words, the pad portion <NUM> is formed so as to cover only the extending portion <NUM>. The pad portion <NUM> is configured to have a narrow width L at the end portion on the connecting portion <NUM> side so that the pad portion <NUM> is less likely to be separated from the strain detecting element <NUM> due to an anchor effect.

The gold constituting the pad portion <NUM> is a material having higher corrosion resistance than the polysilicon constituting the gauge resistor <NUM> and the wiring layer <NUM>. Further, <FIG> is a plan view in which the protective member <NUM> is omitted, and is not a cross-sectional view, but the pad portion <NUM> is hatched for easy understanding. Further, in the similar figures described later, the pad portion <NUM> is hatched for easy understanding. <FIG> is a cross-sectional view taken along the line IV-IV in <FIG>. However, in <FIG>, the gauge resistor <NUM> is exaggerated for easy understanding.

An opening 21a is formed in the protective film <NUM> so as to expose the pad portion <NUM>. In the present embodiment, two openings 21a are formed, and each opening 21a is formed so as to integrally expose the adjacent pad portions <NUM>. That is, the adjacent pad portions <NUM> are exposed from the common opening 21a. The bonding wire <NUM> for electrically connecting to the circuit board <NUM> is connected to a portion of the pad portion <NUM> exposed from the opening 21a.

Further, in the present embodiment, as shown in <FIG>, a barrier metal <NUM> formed by laminating a NiCr (nickel chromium) film <NUM> and a Pd (palladium) film <NUM> in this order from the wiring layer <NUM> side is formed between the pad portion <NUM> and the wiring layer <NUM>. The NiCr film <NUM> has high corrosion resistance and exhibits a function of protecting the polysilicon constituting the strain detecting element <NUM>. The Pd film <NUM> exerts a function of suppressing the gold constituting the pad portion <NUM> from diffusing toward the strain detecting element <NUM> side. The pad portion <NUM> is formed so as to cover the wiring layer <NUM> and the barrier metal <NUM>.

Such the barrier metal <NUM> and the pad portion <NUM> are configured as follows. That is, first, a metal mask in which the region where the NiCr film <NUM> is formed is opened is arranged, and the NiCr film <NUM> is formed by vapor deposition or the like. Next, the barrier metal <NUM> is formed by arranging a metal mask in which the region where the Pd film <NUM> is formed is opened and forming the Pd film <NUM> by vapor deposition or the like. In this case, since the NiCr film <NUM> and the Pd film <NUM> are laminated and arranged in the same region, the manufacturing process can be simplified by using a common metal mask.

Then, when forming the pad portion <NUM>, a metal mask having a larger opening than the metal mask used when forming the NiCr film <NUM> and the Pd film <NUM> is used so that the barrier metal <NUM> is covered. As a result, as described above, the pad portion <NUM> is formed so as to cover the wiring layer <NUM> and the barrier metal <NUM>.

As described above, in the present embodiment, the strain detecting element <NUM> is formed on the low doping layer <NUM>. Therefore, the reliability of the pressure sensor can be improved.

That is, as studied by the present inventors, in a case where the strain detecting element <NUM> made of polysilicon is directly formed on the insulating film <NUM>, when the polysilicon is deposited, the inventors confirmed that an amorphous layer was formed between the polysilicon and the insulating film <NUM>. Then, in the pressure sensor, it was confirmed that the characteristics of the strain detecting element <NUM> may change due to the delayed elasticity of the amorphous layer.

Therefore, in the present embodiment, the low doping layer <NUM> having higher crystallinity than the insulating film <NUM> is arranged on the insulating film <NUM>, and the strain detecting element <NUM> is formed on the low doping layer <NUM>. As a result, the amorphous layer formed between the low doping layer <NUM> and the strain detecting element <NUM> can be made smaller than the case where the strain detecting element <NUM> is formed on the insulating film <NUM>. Further, the amorphous layer is formed between the low doping layer <NUM> and the insulating film <NUM>, but the influence of the delayed elasticity of the amorphous layer is alleviated by the low doping layer <NUM>, and is less likely to be propagated to the strain detecting element <NUM>.

Further, the low doping layer <NUM> is made of a material having a higher electrical resistivity than the gauge resistor <NUM>. Therefore, an amorphous layer is formed between the low doping layer <NUM> and the insulating film <NUM>, and even if the low doping layer <NUM> is affected by the delayed elasticity of the amorphous layer, the influence of the resistance value of the gauge resistor <NUM> can be reduced. Therefore, it is possible to suppress the change in the characteristics of the strain detecting element <NUM>, and further improve the reliability of the pressure sensor.

Further, in the wiring layer <NUM>, only the extending portion <NUM> is connected to the pad portion <NUM>. Therefore, as shown in <FIG>, the contact resistance Rc between the extending portion <NUM> and the pad portion <NUM> is formed on the pad portion <NUM> side with respect to the connection point of the adjacent gauge resistors <NUM>. As a result, the change in each contact resistor Rc is similarly applied to the adjacent gauge resistors <NUM>. Therefore, in such a pressure sensor, it is possible to suppress a decrease in detection accuracy due to a change in the contact resistance Rc.

Here, the protective member <NUM> is made of a gel such as a silicone gel as described above. The gel is a material that can permeate moisture. Therefore, in the present embodiment, the pad portion <NUM> is formed so as to cover the wiring layer <NUM> and the barrier metal <NUM>. As a result, even if the moisture permeates through the protective member <NUM>, the pad portion <NUM> can prevent the moisture from reaching the wiring layer <NUM> (that is, the strain detecting element <NUM>) and the barrier metal <NUM>. Further, the pad portion <NUM> is made of gold having high corrosion resistance against moisture. Therefore, even if the pad portion <NUM> is exposed to moisture, the influence is small. Therefore, it is possible to suppress fluctuations in the characteristics of the strain detecting element <NUM>.

A second embodiment will be described. In the present embodiment, the shape of the opening 21a formed in the protective film <NUM> is changed from that in the first embodiment. Descriptions of the same configurations and processes as those of the first embodiment will not be repeated hereinafter.

In the present embodiment, as shown in <FIG>, the opening 21a formed in the protective film <NUM> exposes a portion where the pad portion <NUM> and the wiring layer <NUM> overlap in a normal direction with respect to a surface direction of the diaphragm <NUM>. Further, the opening 21a is formed so as to expose a portion of the pad portion <NUM> different from a portion covering the end portion of the extending portion <NUM> of the pad portion <NUM>. In other words, the opening 21a is formed inside the extending portion <NUM> without intersecting the end portion of the extending portion <NUM>. That is, the opening 21a is formed so as not to expose a portion where the step is formed on the pad portion <NUM>. In addition, in the normal direction with respect to the surface direction of the diaphragm <NUM>, it is viewed from the normal direction with respect to the surface direction of the diaphragm <NUM>.

According to this configuration, the infiltration of the moisture that has passed through the protective member <NUM> is suppressed by the pad portion <NUM>. Therefore, it is possible to prevent the moisture from reaching the strain detecting element <NUM> and the barrier metal <NUM>, and it is possible to prevent the reliability of the pressure sensor from being lowered.

That is, the pad portion <NUM> is formed by vapor deposition or the like as described above. However, in a case where an aspect ratio, which is a ratio of the height and width of the strain detecting element <NUM> and the barrier metal <NUM>, is large, it may be difficult to completely cover the strain detecting element <NUM> and the barrier metal <NUM>. That is, the side surfaces of the strain detecting element <NUM> and the barrier metal <NUM> may be exposed from the pad portion <NUM>. In this case, if the opening 21a is formed so as to expose the portion of the pad portion <NUM> that covers the end portion of the extending portion <NUM>, when the pad portion <NUM> is not properly formed in the portion, the pad portion <NUM> may not be properly formed, the moisture that has passed through the protective member <NUM> may infiltrate from the portion.

On the other hand, in the present embodiment, the opening 21a formed in the protective film <NUM> is formed to expose the portion different from the covering portion covering the end portion of the extending portion <NUM> of the pad portion <NUM> in the portion where the pad portion <NUM> and the extending portion <NUM> overlap. That is, the portion where the pad portion <NUM> is difficult to be formed is not exposed. Therefore, it is possible to prevent the moisture that has passed through the protective member <NUM> from reaching the strain detecting element <NUM> and the pad portion <NUM>, and it is possible to prevent the reliability of the pressure sensor from being lowered.

A modification of the second embodiment will be described. In the second embodiment, due to wiring restrictions or the like, it may be necessary to form the opening 21a so as to expose the portion of the pad portion <NUM> that covers the end of the extending portion <NUM>. In this case, it is preferable that the opening 21a is set so that the distance from the portion of the strain detecting element <NUM> exposed from the pad portion <NUM> is large. For example, in comparison with <FIG> and <FIG>, a distance between the opening 21a that exposes a portion of the pad portion <NUM> that covers the end of the extending portion <NUM> and a portion of the strain detecting element <NUM> that is exposed from the pad portion <NUM> is longer in <FIG>. Therefore, as shown in <FIG>, it is preferable that the distance between the portion of the strain detecting element <NUM> exposed from the pad portion <NUM> and the end portion of the opening 21a is larger.

A third embodiment will be described. In the present embodiment, a thin-walled portion is formed on the first stem <NUM> as compared with the first embodiment. Descriptions of the same configurations and processes as those of the first embodiment will not be repeated hereinafter.

In the present embodiment, as shown in <FIG>, the first stem <NUM> is formed with a thin-walled portion <NUM> between the welded portion <NUM> and the diaphragm <NUM>, and the thin-walled portion <NUM> has a thinner thickness between the inner wall surface and the outer wall surface than the portion where the welded portion <NUM> is formed. In the present embodiment, the thin-walled portion <NUM> is configured such that a groove portion <NUM> is formed so as to go around the outer wall surface.

According to this configuration, since the thin-walled portion <NUM> is formed on the first stem <NUM>, the reliability of the pressure sensor can be further improved.

That is, in the pressure sensor, after the strain detecting element <NUM> is formed on the first stem <NUM>, the first stem <NUM> and the second stem <NUM> are welded and joined to form the stem <NUM>. In this case, heat is applied when the first stem <NUM> and the second stem <NUM> are welded and joined, but this heat is less likely to be propagated to the diaphragm <NUM> side because the thermal resistance at the thin-walled portion <NUM> increases. Therefore, it is possible to reduce the influence of heat during welding on the strain detecting element <NUM> and the pad portion <NUM> arranged on the diaphragm <NUM>. In particular, since the gold constituting the pad portion <NUM> is easily diffused by heat, it is possible to suppress the diffusion of gold. Therefore, the reliability of the pressure sensor can be further improved.

In the third embodiment, the groove portion <NUM> may not be formed so as to go around the outer wall surface of the first stem <NUM>. Further, the groove portion <NUM> may be formed on the inner wall surface instead of the outer wall surface. Even if the groove portion <NUM> is formed in this way, the thin-walled portion <NUM> is formed in the portion between the welded portion <NUM> and the diaphragm <NUM> in the first stem <NUM>, so that the same effect as that of the third embodiment can be obtained.

A second example useful for understanding the invention will be described. The present example is a modification of the configuration of the circuit board <NUM> with respect to the first example. Descriptions of the same configurations and processes as those of the first example will not be repeated hereinafter.

First, the configuration of an electronic component <NUM> of the present example will be described. The electronic component <NUM> is a QFN, and a circuit chip on which an amplifier circuit, a correction circuit, and the like are formed is housed in a case. Then, as shown in <FIG>, the electronic component <NUM> has two sets of opposite sides 701a to 701d, and has a planar rectangular shape in which the sides 701a to 701d of each set are orthogonal to each other, and has a configuration in which a plurality of electrode portions <NUM> are provided on each side. <FIG> is a plan view showing a side of the electronic component <NUM> facing the circuit board <NUM>. Further, in <FIG>, the electronic component <NUM> has a rectangular shape in a plane, but the electronic component <NUM> may have a substantially rectangular shape in a plane, and may have a rounded shape with chamfered corners.

Then, as shown in <FIG>, the electronic component <NUM> is arranged so that a virtual line K connecting a center of the through hole <NUM> and an outer edge of the circuit board <NUM>, and a center of the two sides 701a and 701c of the two pairs of opposite sides 701a to 701d intersect. In other words, the electronic component <NUM> is arranged in a state in which the virtual line K and the two sides 701a and 701c of the two pairs of opposite sides 701a to 701d are orthogonal to each other. More specifically, the circuit board <NUM> has a hexagonal outer shape. The electronic component <NUM> is arranged so that one side 701c facing the outer edge of the circuit board <NUM> is parallel to one side of the outer edge of the circuit board <NUM> when viewed from the normal direction with respect to the surface direction of the circuit board <NUM>.

On the circuit board <NUM>, electrode portion lands 501a and 501b are formed at positions facing the electrode portions <NUM> formed on the two sides 701b and 701d intersecting one side 701a on the through hole <NUM> side of the electronic component <NUM>. Further, on the circuit board <NUM>, an electrode portion land 501c is formed at a position facing the electrode portion <NUM> formed on the one side 701c facing the one side 701a on the through hole <NUM> side of the electronic component <NUM>. In the following, the electrode portion lands 501a and 501b at positions facing the electrode portions <NUM> formed on the two sides 701b and 701d intersecting the one side 701a on the through hole <NUM> side of the electronic component <NUM> are referred to as the side lands 501a and 501b. Further, the electrode portion 501b at a position facing the electrode portion <NUM> formed on the one side 701c facing the one side 701a on the through hole <NUM> side of the electronic component <NUM> is also referred to as a facing land 501c.

In the present example, the circuit board <NUM> is not formed with the electrode portion land 501c at a position facing the electrode portion <NUM> formed on one side 701a on the through hole <NUM> side of the electronic component <NUM>. Further, as described above, the circuit board <NUM> is also formed with external connection lands 502a to 502c connected to the terminal member <NUM> at positions facing the terminal member <NUM>. In the present example, the external connection land <NUM> has a power supply land 502a to which a power supply voltage is applied, a ground land 502b connected to the ground, and an output land 502c to which a detection result is output. Further, the circuit board <NUM> is also formed with an element land <NUM> electrically connected to the strain detecting element <NUM> in a portion on the through hole <NUM> side. Further, the circuit board <NUM> is also formed with a ground pattern <NUM> that is maintained at a predetermined potential at a position facing the electronic component <NUM> and suppresses the potential fluctuation of the electronic component <NUM>. Further, wiring patterns 511a to 511c and <NUM> for connecting predetermined locations are also connected on the circuit board <NUM>. The circuit board <NUM> is formed with a protective layer such as a resist that protects the wiring patterns 511a to 511c, <NUM> and the like. The protective layer is appropriately formed with openings at a portion to which the bonding wire <NUM> is connected and a portion to be connected to the terminal member <NUM>. In <FIG>, this protective layer is omitted.

Here, the electronic component <NUM> is fixed to the electrode portion lands 501a to 501c via a solder <NUM> as described above. Then, a solder paste constituting the solder <NUM> is arranged by screen printing using a metal mask having a predetermined area opened. In this case, the electrode portion lands 501a to 501c are preferably enlarged so that the opening of the metal mask can be made larger than a predetermined area in order to improve the solder removal property during screen printing.

Therefore, in the present example, as shown in <FIG>, the side lands 501a and 501b have a protrusion length L1 from the electronic component <NUM> so that the solder removal property can be improved in the normal direction with respect to the surface direction of the circuit board <NUM>. However, as shown in <FIG>, the facing lands 501c are arranged on the outer edge side of the circuit board <NUM>, and similarly to the side lands 501a and 501b, if the protrusion length L2 from the electronic component <NUM> is lengthened, the size of the circuit board <NUM> becomes large. The protrusion length L1 is a length in a direction orthogonal to one sides 701b and 701c facing the side lands 501a and 501b of the electronic component <NUM>. The protrusion length L2 is a length in a direction orthogonal to one side 701c facing the facing land 501c of the electronic component <NUM>.

Therefore, in the present example, the facing land 501c has the protrusion length L2 shorter than the protrusion length L1. However, in this case, simply shortening the protrusion length L2 reduces the area of the facing land 501c, so that the size of the opening of the metal mask corresponding to the facing land 501c also becomes smaller. Therefore, when the protrusion length L2 of the facing land 501c is shortened, there is a concern that a solderability may be deteriorated.

Therefore, in the present example, a plurality of electrode portions <NUM> formed on one side 701c of the electronic component <NUM> are further connected to a common facing land 501c. That is, the facing land 501c is configured by connecting a plurality of adjacent electrode portion land. In other words, the plurality of electrode portions <NUM> formed on one side 701c of the electronic component <NUM> face the common facing land 501c. In the present example, two facing lands 501c are formed. Each of the facing lands 501c is connected to four electrode portions <NUM> formed on one side 701c of the electronic component <NUM>, respectively.

The electronic component <NUM> is in a state in which the circuit chip inside the case is electrically connected to the predetermined electrode portion <NUM>. Therefore, the electrode portion <NUM> connected to the common facing land 501c is in a state in which a portion of the circuit chip having the same potential is connected or is not connected to the circuit chip.

As described above, the facing land 501c has the protrusion length L2 shorter than the protrusion length L1. Therefore, the size of the circuit board <NUM> can be reduced as compared with the case where the protrusion length L2 is the same as the protrusion length L1.

Further, the facing land 501c is configured by connecting a plurality of adjacent electrode portion land. Therefore, the area of the facing land 501c can be increased, and the deterioration of the solderability can be suppressed. Therefore, it is possible to suppress the occurrence of poor connection between the electronic component <NUM> and the circuit board <NUM>, and it is possible to improve the reliability of the pressure sensor.

That is, as shown in <FIG>, the side lands 501a and 501b have the protrusion length L1 set so as to improve the solderability. Then, the solder <NUM> is arranged according to the sizes of the side lands 501a and 501b. Therefore, the opening of the metal mask when arranging the solder paste can be enlarged.

On the other hand, as shown in <FIG>, the facing land 501c has the protrusion length L2 shorter than the protrusion length L1. For this reason, the facing land 501c connect the adjacent electrode portion lands so that the solder <NUM> can be spread in the arrangement direction of the electrode portions <NUM>. That is, the opening of the metal mask when arranging the solder paste can be enlarged. Therefore, it is possible to suppress the deterioration of the solderability, and it is possible to suppress the occurrence of poor connection between the electronic component <NUM> and the circuit board <NUM>. <FIG> shows a state in which the two electrode portions <NUM> are connected to the common facing land 501c.

Further, in the present example, on the circuit board <NUM>, the electrode portion land is not formed at a position facing the electrode portion <NUM> formed on one side 701a on the through hole <NUM> side. Therefore, the electronic component <NUM> can be arranged close to the through hole <NUM>, and the circuit board <NUM> can be miniaturized.

In the present example, since the electronic component <NUM> is arranged on the circuit board <NUM> as described above, the three regions of the electronic component <NUM> are connected to the electrode portion lands 501a to 501c. In this case, if the amount of solder <NUM> between the facing land 501c and the electrode portion <NUM> is increased too much, there is a concern that the electronic component <NUM> may be tilted with respect to the circuit board <NUM>. Therefore, it is preferable that the amount (that is, the thickness) of the solder <NUM> arranged on the facing land <NUM> is adjusted so that the electronic component <NUM> does not tilt.

A third example useful for understanding the invention will be described hereafter. The present example is a modification of the configuration of the circuit board <NUM> with respect to the second example. Descriptions of the same configurations and processes as those of the second example will not be repeated hereinafter.

In the present example, as shown in <FIG>, the external connection lands 502a to 502c and the electrode portion land 501b are connected via the external connection patterns 511a to 511c. The element land <NUM> and the electrode portion land 501a are connected via a sensing pattern <NUM>. The external connection patterns 511a to 511c and the sensing pattern <NUM> are formed in different regions.

Specifically, the external connection patterns 511a to 511c and the sensing pattern <NUM> are formed so as to intersect different virtual lines K with respect to the virtual line K connecting the center of the through hole <NUM> and the outer edge of the circuit board <NUM>. In other words, the external connection patterns 511a to 511c and the sensing pattern <NUM> are formed so as not to intersect the same virtual line K. For example, the virtual line K in <FIG> intersects only the sensing pattern <NUM>.

Then, on the circuit board <NUM>, a guard pattern <NUM> maintained at a predetermined potential is formed between the power supply pattern 511a connecting the power supply land 502a and the electrode portion land 501a and the sensing pattern <NUM>.

In the present example, the guard pattern <NUM> is maintained at the ground potential. Specifically, as shown in <FIG>, the circuit board <NUM> is formed with a guard pattern <NUM> on the back surface 50b side as well as a plurality of through-hole electrodes <NUM>. The guard pattern <NUM> on the back surface 50b side is connected to the ground pattern 511b connected to the ground land 502b through the through-hole electrode <NUM>, and is maintained at the ground potential. Then, the guard pattern <NUM> on the front surface 50a side is maintained at the ground potential by being connected to the guard pattern <NUM> on the back surface 50b side through the through-hole electrode <NUM>.

Further, in the present example, the circuit board <NUM> is formed with a ground pattern <NUM> for a body ground on the back surface 50b side. Further, in the present example, a joining portion <NUM> arranged between the mounting portion <NUM> of the housing <NUM> and the circuit board <NUM> uses a conductive adhesive. Then, in the circuit board <NUM>, the ground pattern <NUM> is configured as the body ground by electrically connecting the connection portion 523a to the housing <NUM> via the joining member <NUM>.

According to this configuration, the external connection patterns 511a to 511c and the sensing pattern <NUM> are formed in different regions. Since the external connection patterns 511a to 511c are connected to the external circuit via the terminal member <NUM>, noise is likely to be applied. Therefore, it is possible to suppress the propagation of noise from the external connection patterns 511a to 511c to the sensing pattern <NUM> as compared with the case where the external connection patterns 511a to 511c and the sensing pattern <NUM> are formed in the same region (that is, close to each other).

Further, in the external connection patterns 511a to 511c, noise is particularly likely to be applied to the power supply pattern 511a. Then, in the present example, the guard pattern <NUM> maintained at a predetermined potential is formed between the power supply pattern 511a and the sensing pattern <NUM>. Therefore, even if noise is applied to the power supply pattern 511a, it is possible to suppress the noise from being coupled to the sensing pattern <NUM>. Therefore, it is possible to suppress a decrease in detection accuracy and improve the reliability of the pressure sensor.

A fourth example useful for understanding the invention will be described. The present example is a modification of the configuration of the circuit board <NUM> with respect to the second example. Descriptions of the same configurations and processes as those of the second example will not be repeated hereinafter.

As described above, the circuit board <NUM> is formed with the protective layer such as a resist, and the protective layer is appropriately provided with openings at a portion to which the bonding wire <NUM> is connected and a portion to be connected to the terminal member <NUM>. Then, in the present example, as shown in <FIG>, an opening <NUM> is formed in the protective layer <NUM> so as to reach the through hole <NUM> while exposing entirely the element land <NUM>. Further, on the back surface 50b side of the circuit board <NUM>, a portion of the protective layer <NUM> located at the end on the through hole <NUM> side is removed. In this example, the opening <NUM> corresponds to a damming structure. Further, <FIG> corresponds to a cross-sectional view taken along the line XVII-XVII in <FIG>.

According to this configuration, the protective layer <NUM> is formed with the opening <NUM> so as to reach the through hole <NUM> while exposing entirely the element land <NUM>. Therefore, the reliability of the pressure sensor can be improved.

That is, the strain detecting element <NUM> and the element land <NUM> are electrically connected via the bonding wire <NUM>. Further, as shown in <FIG>, the protective member <NUM> made of a gel such as a silicone gel is arranged on the strain detecting element <NUM>. In this case, the protective member <NUM> may bleed onto the circuit board <NUM> along the bonding wire <NUM>. Then, when the protective member <NUM> bleeds onto the circuit board <NUM> and reaches between the terminal member <NUM> and the external connection lands 502a to 502c, there is a possibility that a poor connection between the terminal member <NUM> and the external connection lands 502a to 502c occurs.

Therefore, in the present example, the protective layer <NUM> is formed with the opening <NUM> so as to reach the through hole <NUM> while exposing entirely the element land <NUM>. As a result, when the protective member <NUM> bleeds to the element land <NUM> side, the area for accumulating the protective member <NUM> can be increased as compared with the case where the protective layer <NUM> is formed with the opening <NUM> in which only a part of the element land <NUM> is opened. Further, when the protective member <NUM> bleeds to the element land <NUM> side, the protective member <NUM> can be flowed to the back surface 50b side of the circuit board <NUM> through the through hole <NUM>. Therefore, it is possible to prevent the protective member <NUM> from reaching the external connection lands 502a to 502c, and it is possible to suppress the occurrence of poor connection between the terminal member <NUM> and the external connection lands 502a to 502c. Therefore, the reliability of the pressure sensor can be improved.

embodiment fifth example useful for understanding the invention will be described. The present example is a modification of the configuration of the circuit board <NUM> with respect to the fourth example. Descriptions of the same configurations and processes as those of the fourth example will not be repeated hereinafter.

In the present example, as shown in <FIG>, a dam portion <NUM> is formed between the element land <NUM> connected to the strain detecting element <NUM> and the external connection lands 502a to 502c. Specifically, the dam portion <NUM> is constructed by forming an uneven structure on the protective layer <NUM>. That is, the dam portion <NUM> is configured, for example, by forming a recess in the protective layer <NUM> that is recessed from the periphery. Further, the dam portion <NUM> is configured by forming, for example, a convex portion protruding from the periphery.

In the present example, the dam portion <NUM> corresponds to a damming structure. Further, <FIG> shows a state in which the protective layer <NUM> is arranged on the circuit board <NUM>. However, the openings for exposing the element lands <NUM> and the external connection lands 502a to 502c formed on the protective layer <NUM> are omitted.

In this way, the dam portion <NUM> may be formed between the element land <NUM> and the external connection lands 502a to 502c. Even with such a configuration, when the protective member <NUM> bleeds to the element land <NUM> side, the dam portion <NUM> can prevent the protective member <NUM> from reaching the external connection lands 502a to 502c. Therefore, the same effect as that of the fourth example can be obtained.

A plurality of dam portions <NUM> may be formed between the element land <NUM> and the external connection lands 502a to 502c.

A sixth example useful for understanding the invention will be described. In the present example, the shape of the housing <NUM> is changed from that of the first example. Descriptions of the same configurations and processes as those of the first example will not be repeated hereinafter.

In the present example, as shown in <FIG>, the housing <NUM> is formed with a height projection <NUM> as a convex portion on the mounting portion <NUM>. Specifically, the height projections <NUM> are formed at three locations. Further, the housing <NUM> has a tubular shape having a hollow portion having a central axis a in one direction. Each of the height projections <NUM> is formed at equal intervals in the circumferential direction about the central axis a, and has the same height. Each of the height projections <NUM> is formed by press molding or the like when the housing <NUM> is prepared. That is, each height projection is formed using the same processing device.

Then, as shown in <FIG>, the circuit board <NUM> is arranged so as to be in contact with each height projection <NUM>. That is, the circuit board <NUM> is arranged in contact with the height projections formed at equal intervals in the circumferential direction at three locations. A joining member <NUM> is arranged between the circuit board <NUM> and the mounting portion <NUM>.

In the present example, the circuit board <NUM> is arranged so that the center of the through hole <NUM> and the central axis a of the housing <NUM> coincide with each other. Therefore, the portions of the circuit board <NUM> that come into contact with the height projections <NUM> are located at equal intervals in the circumferential direction with the through hole <NUM> as the center. Further, <FIG> shows the housing <NUM> and the circuit board <NUM>, and the configuration of the stem <NUM> and the like are omitted.

Further, in the present example, although not particularly shown, one of the height projections <NUM> is formed so as to be located on the opposite side of the terminal member <NUM> with the circuit board <NUM> interposed therebetween.

According to this configuration, the circuit board <NUM> is in contact with each height projection <NUM> at three points. Further, each of the height projections <NUM> is formed at equal intervals in the circumferential direction, and have the same height. Therefore, it is possible to prevent the circuit board <NUM> from tilting with respect to the mounting portion <NUM>. Therefore, it is possible to suppress the occurrence of poor connection between the terminal member <NUM> and the circuit board <NUM>, and it is possible to improve the reliability of the pressure sensor.

Further, the distance between the mounting portion <NUM> and the circuit board <NUM> is defined by the height of the height projection <NUM>. Therefore, the distance between the mounting portion <NUM> and the circuit board <NUM> can be set as a desired distance. That is, a joining member <NUM> having a desired thickness can be arranged between the mounting portion <NUM> and the circuit board <NUM>. Therefore, the joining member <NUM> can exert a desired stress relaxation function, and the stress propagated from the housing <NUM> to the circuit board <NUM> can be reduced.

By the way, it is conceivable to secure a space between the circuit board <NUM> and the mounting portion <NUM> by arranging a spacer or the like prepared separately from the housing <NUM> between the circuit board <NUM> and the mounting portion <NUM>. However, in this configuration, since spacer is separately formed, it is assumed that the height of each spacer varies. In addition, the number of parts is increased by preparing spacers.

On the other hand, in the present example, each of the height projections <NUM> is formed on the housing <NUM> by using the same processing device, and it is suppressed that the heights are different. Therefore, in the present example, it is possible to reduce the number of parts while suppressing the circuit board <NUM> from tilting with respect to the mounting portion <NUM>, as compared with the case where the space between the circuit board <NUM> and the mounting portion <NUM> is secured by arranging a spacer or the like prepared separately from the housing <NUM>.

Further, when the spacer is made of a material different from that of the housing <NUM>, there is a concern that cracks may occur in the spacer due to the difference in the coefficient of thermal expansion from the housing <NUM>. However, in the present example, since each height projection <NUM> is composed of a part of the housing <NUM>, it is possible to suppress the introduction of cracks into the height projection <NUM> due to the difference in the coefficient of thermal expansion.

Further, in the present example, one of the height projections <NUM> is formed so as to be located on the opposite side of the terminal member <NUM> with the circuit board <NUM> interposed therebetween. Therefore, since the pressing force of the terminal member <NUM> can be supported by the height projection <NUM>, the tilting of the circuit board <NUM> can be further suppressed.

A modification of the sixth example will be described. In the sixth example, the height projections <NUM> may be formed at four or more locations at equal intervals in the circumferential direction about the central axis a. However, even if the height projections <NUM> are formed at four or more locations, the circuit board <NUM> is in principle in contact with each height projection <NUM> at three locations.

Further, in the sixth example, the height projection <NUM> may not be formed so as to be located on the opposite side of the terminal member <NUM> with the circuit board <NUM> interposed therebetween.

A seventh example useful for understanding the invention will be described. In the present example, the shape of the housing <NUM> is changed from that of the sixth example. Descriptions of the same configurations and processes as those of the sixth example will not be repeated hereinafter.

In the present example, as shown in <FIG>, the housing <NUM> is formed with one height projection <NUM> and one side portion <NUM> having a predetermined length on the mounting portion <NUM>. Specifically, the height projection <NUM> and the side portion <NUM> are centered on the central axis a, and the lengths in the circumferential direction between the height projection <NUM> and each end of the side portion <NUM> are evenly spaced. Further, the heights of the height projection <NUM> and the side portion <NUM> are the same. The side portion <NUM> has, for example, a length of about <NUM>/<NUM> with respect to one side of the hexagonal shape constituting the outer shape of the housing <NUM>. Further, in the present example, the height projection <NUM> and the side portion <NUM> correspond to the convex portion.

The circuit board <NUM> is arranged so as to come into contact with the height projection <NUM> and the side portion <NUM>. Therefore, the circuit board <NUM> is in contact with the height projection <NUM> and the side portion <NUM>. Then, the side portion <NUM> is in contact with the circuit board <NUM> over a predetermined length.

In this way, even if one height projection <NUM> and one side portion <NUM> are formed on the housing <NUM> so as to come into contact with the circuit board <NUM> at two locations, the same effect as that of the sixth example can be obtained.

A modification of the seventh example will be described. In the seventh example, the two side portions <NUM> may be provided without forming the height projection <NUM>. In this case, the two side portions <NUM> may be formed so that the lengths in the circumferential direction between the ends are evenly spaced. Even with such a configuration, since the circuit board <NUM> comes into contact with the side portion <NUM> at two locations, the same effect as that of the sixth example can be obtained.

Further, in the sixth example, if the circuit board <NUM> comes into contact with the height projections <NUM> at three locations, the side portions <NUM> may be formed on the housing <NUM>. For example, the housing <NUM> may be formed with three side portions <NUM>. In this case, each side portion <NUM> may be formed in such manner that the distance between the edges of the side portions <NUM> is formed at equal intervals in the circumferential direction with the central axis a as the center. Further, for example, the housing <NUM> may be formed with one height projection <NUM> and two side portions <NUM>. In this case, in the one height projection <NUM> and the two side portions <NUM>, the distance between the height projection <NUM> and the ends of each side portion <NUM> is formed at equal intervals in the circumferential direction with the central axis a as the center.

An eighth example useful for understanding the invention will be described. The present example is a modification of the configuration of the housing <NUM> with respect to the sixth example. Descriptions of the same configurations and processes as those of the sixth example will not be repeated hereinafter.

In the present example, as shown in <FIG>, the housing <NUM> is formed with a height projection <NUM> and an alignment projection <NUM>. In the present example, the alignment projection <NUM> is formed on the height projection <NUM>, and the length of the outer wall surface of the alignment projection <NUM> is shorter than that of the height projection <NUM>.

The circuit board <NUM> is formed with a recess <NUM> into which the alignment projection <NUM> is inserted at a position corresponding to the alignment projection <NUM>. The circuit board <NUM> is arranged in a state in which the alignment projection <NUM> is inserted into the recess <NUM> and the height projection <NUM> is in contact with the circuit board <NUM>.

According to this configuration, since the alignment projection <NUM> is inserted into the recess <NUM> of the circuit board <NUM>, misalignment is less likely to occur. Further, when arranging the circuit board <NUM>, the alignment projection <NUM> may be inserted into the recess <NUM>, so that the alignment can be facilitated.

A modification of the eighth example will be described. In the eighth example, as shown in <FIG>, the alignment projection <NUM> may be formed separately from the height projection <NUM>. Further, as shown in <FIG>, the recess <NUM> may be formed at an outer edge portion of the circuit board <NUM>. That is, the recess <NUM> may be a notch formed in the outer edge portion of the circuit board <NUM>.

A ninth example useful for understanding the invention will be described. In the present example, the circuit board <NUM> is provided with a conductive terminal portion as compared with the first example. Descriptions of the same configurations and processes as those of the first example will not be repeated hereinafter.

In the present example, as shown in <FIG>, the circuit board <NUM> is formed with a pad portion <NUM> for the body ground on the surface 50a side. Specifically, the circuit board <NUM> is formed with a cutout portion <NUM> at the outer edge portion. In the present example, the circuit board <NUM> has a hexagonal outer shape before the cutout portion <NUM> is formed, and the cutout portion <NUM> is formed by cutting out one corner portion forming the hexagonal shape. The pad portion <NUM> is arranged around the cutout portion <NUM>. In the present example, the pad portion <NUM> is formed in the regions 55a and 55b that sandwich the cutout portion <NUM>.

At least the surface of the pad portion <NUM> is made of gold. Further, in <FIG> and the like, in the plan view of the circuit board <NUM>, a predetermined wiring pattern and other wiring patterns connected to the pad portion <NUM> are omitted.

The conduction terminal portion <NUM> is arranged so as to be electrically connected to the pad portion <NUM> and electrically connected to the mounting portion <NUM> of the housing <NUM>. The conductive terminal portion <NUM> have a board side connection portion <NUM> joined to the circuit board <NUM>, a housing side connection portion <NUM> connected to the mounting portion <NUM> of the housing <NUM>, and a connecting portion <NUM> connected the board side connection portion <NUM> and the housing side connection portion <NUM>.

The board side connection portion <NUM> has a flat plate shape, and two board side connection portions <NUM> are provided so as to correspond to the shape of each pad portion <NUM>. The housing side connection portion <NUM> has a disk shape, and a convex portion <NUM> as a projection is formed substantially in the center of the housing side connection portion <NUM>.

The board side connection portion <NUM> and the housing side connection portion <NUM> are formed so as to be located on different surfaces. Further, the board side connection portion <NUM> and the housing side connection portion <NUM> are formed so that the housing side connection portion <NUM> does not intersect a virtual surface connecting the two board side connection portions <NUM>. That is, the housing side connection portion <NUM> is arranged at a position protruding from the virtual surface connecting the two board side connection portions <NUM>.

The connecting portion <NUM> has a board side connecting part <NUM> and a housing side connecting part <NUM>. The board side connecting part <NUM> is connected to each board side connection portion <NUM> and extends from a portion where the board side connection portion <NUM> is located to a surface where the housing side connecting part <NUM> is located. The board side connecting part <NUM> extends along the normal direction with respect to the surface direction of the board side connection portion <NUM>. The housing side connecting part <NUM> is provided so as to connect a portion of the board side connecting part <NUM> opposite to the board side connection portion <NUM> to the housing side connection portion <NUM>.

Further, the connecting portion <NUM> has an elastic part <NUM> that can be elastically deformed. In the present example, the elastic part <NUM> is provided on the housing side connecting part <NUM> by forming a portion having a lower rigidity than the board side connection portion <NUM> or the like on the housing side connecting part <NUM>. For example, in the present example, the housing side connecting part <NUM> has the same thickness as the board side connection portion <NUM> and the like, but a width L1 of the housing side connecting part <NUM> is narrower than the width L2 of the board side connection portion <NUM>. As a result, the elastic part <NUM> is formed in the housing side connecting part <NUM>.

Then, in the conduction terminal portion <NUM>, the board side connection portion <NUM> is connected to each pad portion <NUM> formed on the surface 50a of the circuit board <NUM> via the solder <NUM>. Further, the conductive terminal portion <NUM> is arranged so that the housing side connection portion <NUM> is located on the back surface 50b side of the circuit board <NUM> by arranging the board side connecting part <NUM> in the cutout portion <NUM>.

At this time, the conduction terminal portion <NUM> is arranged so as not to protrude outward from the outer edge of the circuit board <NUM> before forming the cutout portion <NUM>. That is, in the conduction terminal portion <NUM>, the housing side connection portion <NUM> and the connecting portion <NUM> are housed in the cutout portion <NUM> in the normal direction with respect to the surface direction of the circuit board <NUM>. That is, in the present example, the cutout portion <NUM> and the conduction terminal portion <NUM> are sized and shaped so as not to project outward from the outer edge of the circuit board <NUM> before the conduction terminal portion <NUM> forms the cutout portion <NUM> when the conduction terminal portion <NUM> is arranged. Further, the conductive terminal portion <NUM> is arranged so that the center of gravity of the conductive terminal portion <NUM> is located at the center of the two pad portions <NUM> in the normal direction with respect to the surface direction of the circuit board <NUM>.

Then, the housing side connection portion <NUM> is connected to the mounting portion <NUM> of the housing <NUM> by resistance welding. That is, the housing side connection portion <NUM> and the mounting portion <NUM> of the housing <NUM> are electrically connected via the welded portion <NUM>. As a result, the pad portion <NUM> of the circuit board <NUM> is connected to the mounting portion <NUM> of the housing <NUM> via the conduction terminal portion <NUM> to the body ground. In the conduction terminal portion <NUM>, after the board side connection portion <NUM> is connected to the pad portion <NUM> of the circuit board <NUM>, the housing side connection portion <NUM> is resistance welded to the mounting portion <NUM> of the housing <NUM>.

Similar to the housing <NUM> described with reference to <FIG> of the sixth example, the housing <NUM> of the present example has three height projections <NUM> on the mounting portion <NUM> at equal intervals in the circumferential direction about the central axis a. The circuit board <NUM> has a structure in which the cutout portion <NUM> is formed at one corner of the hexagonal shape, and the three height projections <NUM> are arranged so as to be close to each of the three corners of the hexagonal shape. That is, the circuit board <NUM> is arranged so that one height projection <NUM> is located on the opposite side of the conduction terminal portion <NUM> with respect to the central axis a.

Further, the circuit board <NUM> is mechanically connected to the mounting portion <NUM> of the housing <NUM> via the joining member <NUM> arranged between the mounting portion <NUM> of the housing <NUM> and the circuit board <NUM>. In the present example, the circuit board <NUM> is electrically connected to the mounting portion <NUM> of the housing <NUM> via the conductive terminal portion <NUM>. Therefore, as the joining member <NUM>, a member that connects the circuit board <NUM> and the mounting portion <NUM> of the housing <NUM> only mechanically may be used, and for example, a silicone-based adhesive or the like is used.

The joining members <NUM> are arranged at five locations in the present example. Specifically, the three joining members <NUM> are arranged around the height projections <NUM>. Further, the two joining members <NUM> are arranged near the corners of the circuit board <NUM>, which are different from the corners where the height projections <NUM> are arranged. That is, the two joining members <NUM> are arranged in the center of the circumferential direction between the first height projection <NUM> located on the opposite side of the conduction terminal portion <NUM> with respect to the central axis a, and each second height projection <NUM> adjacent to the first height projection <NUM>.

As described above, in the present example, the pad portion <NUM> for the body ground is formed on the circuit board <NUM>, and the pad portion <NUM> is electrically connected to the mounting portion <NUM> of the housing <NUM> via the conduction terminal portion <NUM>. The conduction terminal portion <NUM> is joined to the mounting portion <NUM> of the housing <NUM> via the welded portion <NUM>. Further, the circuit board <NUM> is mechanically connected to the mounting portion <NUM> of the housing <NUM> via the joining member <NUM>. Therefore, it is possible to improve the bondability between the circuit board <NUM> and the mounting portion <NUM> of the housing <NUM>, and to stabilize the electrical connection between the pad portion <NUM> of the circuit board <NUM> and the mounting portion <NUM> of the housing <NUM>.

That is, for example, when the circuit board <NUM> is connected to the housing <NUM> by the body ground, a pad portion for the body ground is formed on the back surface 50b side of the circuit board <NUM>, and a conductive member made of silver paste is arranged between the pad portion and the mounting portion <NUM> of the housing <NUM>. Therefore, it is conceivable to connect the pad portion and the housing <NUM> to the body ground. At least the surface of the pad portion is made of gold.

However, in this configuration, the bondability between the conductive member made of silver paste and the pad portion made of gold tends to be low, and the thickness of the conductive member tends to vary. Therefore, in this configuration, there is a concern that the contact resistance varies between the pad portion <NUM> and the mounting portion <NUM> of the housing <NUM>, and the stability of the electrical connection may decrease.

On the other hand, in the present example, since the mounting portion <NUM> of the housing <NUM> and the conductive terminal portion <NUM> electrically connected via the welded portion <NUM> are used, the stability of the electrical connection between the circuit board <NUM> and the mounting portion <NUM> of the housing <NUM> can be achieved. The solder <NUM> is arranged between the board side connection portion <NUM> and the pad portion <NUM>, but the solder <NUM> has higher bondability with gold constituting the pad portion <NUM> than silver and is easy to stabilize. Therefore, the thickness of the solder <NUM> is unlikely to vary, and variation in contact resistance is suppressed. That is, the board side connection portion <NUM> and the pad portion <NUM> are connected via the solder <NUM> in an electrically stable state.

Further, in the present example, the pad portion <NUM> is formed on the surface 50a of the circuit board <NUM> and is connected to the board side connection portion <NUM> of the conduction terminal portion <NUM> via the solder <NUM>. Therefore, the solder <NUM> can be arranged at the same time as the solder paste or the like when the electronic component <NUM> is arranged on the circuit board <NUM>. Therefore, it is possible to prevent the manufacturing process from becoming complicated.

Further, the conductive terminal portion <NUM> is configured to have the elastic part <NUM> at the connecting portion <NUM>. Therefore, when the convex portion <NUM> of the housing side connection portion <NUM> is resistance welded to the mounting portion <NUM> of the housing <NUM>, the elastic part <NUM> is elastically deformed. Therefore, it is possible to prevent excessive stress from being propagated to the board side connection portion <NUM>. That is, it is possible to prevent problems such as the board side connection portion <NUM> being peeled off from the pad portion <NUM>.

Further, the conductive terminal portion <NUM> is arranged so that the center of gravity of the conductive terminal portion <NUM> is located at the center of the two pad portions <NUM> in the normal direction with respect to the surface direction of the circuit board <NUM>. Therefore, before connecting the conductive terminal portion <NUM> to the mounting portion <NUM> of the housing <NUM>, the inclination of the conductive terminal portion <NUM> can be suppressed, and it is possible to prevent the process of resistance welding the housing side connection portion <NUM> to the mounting portion <NUM> of the housing <NUM> from becoming complicated.

Further, the conduction terminal portion <NUM> is arranged so as not to protrude outward from the outer edge of the circuit board <NUM> before forming the cutout portion <NUM>. Therefore, by arranging the conduction terminal portion <NUM>, it is possible to prevent the pressure sensor from becoming large.

The modification of the ninth example will be described below. In the ninth example, the example in which the cutout portion <NUM> is formed in the outer edge of the circuit board <NUM> has been described. However, a through hole is formed in the inner edge of the circuit board <NUM>, and the conduction terminal portion <NUM> is arranged in the through hole.

Further, in the ninth example, the pad portion <NUM> may be formed on the back surface 50b side of the circuit board <NUM>, and the board side connection portion <NUM> of the conduction terminal portion <NUM> may connect to the pad portion <NUM> on the back surface 50b side of the circuit board <NUM>. In this case, the shape of the conductive terminal portion <NUM> is appropriately adjusted so that it can be connected to the back surface 50b side of the circuit board <NUM>.

A tenth example useful for understanding the invention will be described. The present example is a modification of the configuration of the conductive terminal portion <NUM> with respect to the ninth example. Descriptions of the same configurations and processes as those of the ninth example will not be repeated hereinafter.

In the present example, as shown in <FIG>, the board side connecting part <NUM> of the conductive terminal portion <NUM> is connected to the board side connection portion <NUM>, and has a first connecting part 931a extending to the side opposite to the housing side connection portion <NUM> from the board side connection portion <NUM> and a second connecting part 931b connecting the first connecting part 931a and the housing side connecting part <NUM>. That is, a part of the conduction terminal portion <NUM> is in a state of protruding from the surface 50a side of the circuit board <NUM>.

The elastic part <NUM> is composed of the housing side connecting part <NUM> and the second connecting part 931b. Specifically, the second connecting part 931b is made into the elastic part <NUM> by having the same width as the housing side connecting part <NUM>. That is, as compared with the first example, the region of the elastic part <NUM> in the conductive terminal portion <NUM> is larger.

As described above, in the present example, the elastic part <NUM> has the housing side connecting part <NUM> and the second connecting part 931b. Therefore, when the convex portion <NUM> of the housing side connection portion <NUM> is resistance welded to the mounting portion <NUM> of the housing <NUM>, the elastic part <NUM> is elastically deformed. Therefore, it is possible to prevent excessive stress from being propagated to the board side connection portion <NUM>.

For example, in the above embodiments, the first stem <NUM> and the second stem <NUM> may be configured by using the same material. Further, the alignment portion <NUM> may not be formed on the second stem <NUM>. Then, in the above embodiments, the stem <NUM> may be composed of a single member instead of the configuration having the first stem <NUM> and the second stem <NUM>.

Claim 1:
A pressure sensor that detects a pressure of a pressure medium, comprising:
a stem (<NUM>) having
a pressure introduction hole (<NUM>) formed on one end side and into which the pressure medium is introduced, and
a diaphragm (<NUM>) formed on the other end side and that can be deformed according to the pressure of the pressure medium;
an insulating film (<NUM>) arranged on the diaphragm (<NUM>); and
a strain detecting element (<NUM>) being arranged on the insulating film (<NUM>) and being configured to output a detection signal according to the deformation of the diaphragm (<NUM>), wherein
the strain detecting element (<NUM>) has a portion made of polysilicon,
characterized by further comprising
a low doping layer (<NUM>) arranged on the insulating film (<NUM>) between the insulating film (<NUM>) and the strain detecting element (<NUM>),
the low doping layer (<NUM>) having a higher electrical resistivity than the polysilicon and a higher crystallinity than the insulating film (<NUM>) .