Sensor for detecting one or more quantities of a fluid, in particular a pressure sensor

A sensor has a sensor body with a first face and a second face opposite to one another, and a circuit arrangement supported by the sensor body that includes a first electrical circuit pattern on the first face, a second electrical circuit pattern on the second face, connection means, which electrically connect the first circuit pattern to the second circuit pattern and has at least one through hole that extends axially between the two faces of the sensor body. A plurality of terminals are electrically connected to the first circuit pattern and/or the second circuit pattern. The at least one through hole is preferably closed at the second face of the sensor body via a closing member (30) having pre-formed body with a closing portion having a diameter, greater than a diameter, of the opening of the through hole at the second face of the sensor body.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage filing under section 371 of International Application No. PCT/IB2016/052153, filed on Apr. 15, 2016, published in English on Oct. 20, 2016, as WO2016/166712 A1 and which claims priority to Italian Application No. 102015000012046, filed on Apr. 16, 2015, the entire disclosure of these applications being hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates in general to sensors and to electronic circuits for detecting one or more quantities of a fluid, such as for example pressure sensors, and has been developed with particular reference to sensors and circuits comprising at least one body made of electrically insulating material, such as a ceramic or polymeric material. The invention finds preferred application in sensors having a body that comprises at least one flexible or movable part, in particular a body with a cavity and at least one membrane in a position corresponding to the cavity.

PRIOR ART

Some sensors of the type referred to are used in devices for detecting the pressure of fluids (liquids and aeriforms) in various sectors, such as the automotive sector, the domestic sector and sector of electrical household appliances, and the HVAC, plumbing, and sanitary sector. These sensing devices typically comprise a casing or a support, defining at least one housing with an inlet for a fluid of which the pressure is to be measured, as well as a pressure sensor set in the housing so that a sensitive portion thereof is exposed to the fluid, typically a portion comprising a membrane.

The pressure sensor has a sensor body, in general made of electrically insulating material, with an axial cavity that is closed at at least one end by the aforesaid membrane portion. In some sensors of a first type, which are generally referred to as “relative sensors”, the axial cavity is substantially a blind cavity, which is closed at a face of the sensor body, here defined for simplicity as “upper face”. The axial cavity opens, instead, at the opposite face of the sensor body, here defined as “lower face”, and is set in fluid communication with the inlet of the device. In sensors of a second type, which are generally referred to as “absolute sensors”, the cavity is, instead, substantially closed at both of its opposite ends, at one of these there being provided the membrane portion, the outer side of which is exposed to the fluid. Also known are pressure sensors of a third type, for example sensors having a body with a structure substantially similar to that of the sensors of the aforesaid second type, where, however, the cavity of the sensor body is set in fluid communication with the external environment or with another reference pressure, via at least one passage defined in a part thereof different from the corresponding membrane portion.

The sensor body may be monolithic or else made up of a number of parts. For instance, in the case of a sensor of the first type mentioned, the sensor body may be monolithic, in order to define integrally the blind cavity with the corresponding membrane portion, or else may comprise an axially hollow body, fixed at one end of which is a membrane element in order to close the aforesaid cavity at one side. The body of a sensor of the second type or third type referred to is generally made up of a number of parts, for example including a main body that defines at least a part of a cavity, closed by a further body that defines the membrane. In the case of a sensor of the second type, the cavity is blind, closed at one end (such as the upper face) by a portion of the body itself and closed at the other end (such as the lower face) by a membrane portion applied to the main body. In the case of sensors of the third type, the main body is perforated, preferably at the end opposite to the membrane part. In the case of sensors of the aforesaid second type, the end opposite to the membrane part may hence be without holes in order to provide a pressure sensor of an absolute type. In sensors of the aforesaid third type, instead, the upper face may have a hole in order to set the cavity of the sensor body in communication with the external environment or other pressure reference in order to provide a pressure sensor of a relative or differential type.

The sensor body supports a circuit arrangement, which in general includes terminals for connection of the sensor to an external system, and a circuit pattern made of electrically conductive material, typically deposited on the side of the membrane portion protected from the fluid, for example the side external to the cavity in the case of sensors of the first type, or on the side of the membrane portion facing the cavity in the case of sensors of the second and third types.

Associated to the above circuit pattern are one or more circuit components—for example, piezoelectric, piezo-resistive, resistive, or capacitive components—designed to detect bending or deformation of the membrane portion, which depends upon the pressure of the fluid.

In some applications, provided on the face of the sensor body opposite to the membrane portion is a further circuit pattern belonging to the circuit arrangement, which is also obtained by deposition of electrically conductive material. Also to this second circuit pattern there may be associated one or more circuit components of the circuit arrangement.

For instance, WO 2010/134043 A, filed in the name of the present Applicant, describes a pressure sensor of the second type referred to above, in particular of an absolute type, the sensor body of which comprises a first part defining a blind cavity and a second part that is fixed with respect to the first part so as to close the aforesaid cavity.

An inner side the second part, which provides a deformable membrane, has a first circuit pattern, connected to which are the means for detecting deformation of the membrane, for example of the type referred to above. Provided on the upper face of the first part of the sensor body—i.e., the face opposite to the second body part—are the connection terminals of the sensor and a second circuit pattern, connected to which are other electrical and/or electronic components of the circuit arrangement for control of the sensor (for example, a microcontroller, amplification components, calibration components, filtering components, connection terminals, etc.). The two circuit patterns are connected together by electrically conductive means that extend in an axial direction of the sensor body. More in particular, the first part of the sensor body has axial through holes, in a position peripheral with respect to the corresponding blind cavity, with the inner surface of these holes that is coated with a layer of electrically conductive material. One end of this conductive layer is hence located in a position corresponding to the portion of the lower face of the first body part that surrounds the opening of the blind cavity and is connected to at least one electrically conductive track of the aforesaid first circuit pattern deposited on the inner side of the second body part, i.e., the sensing membrane. The other end of the conductive layer is located, instead, at the upper face of the first body part, opposite to the membrane, and is connected to at least one track of the aforesaid second circuit pattern. In this way, the two circuit patterns are electrically connected together and/or to the terminals.

A similar solution is known also from WO 2014/097255 A, filed in the name of the present Applicant, on which the preamble of claim1is based. This document describes a pressure sensor of the first type referred to above, with a monolithic sensor body that defines a blind cavity, closed at one face of the body by a membrane portion. Provided on the outer side of the membrane portion are the connection terminals and a first circuit pattern, with associated thereto the components for detecting deformation, whereas provided on the opposite face of the body, in a position peripheral with respect to the opening of the cavity, is a second circuit pattern, for connection of a component for detecting a quantity of the fluid that is to be measured, in particular a temperature sensor. The temperature sensor is mounted so that at least its sensitive part is exposed directly to the fluid, substantially in front of the opening of the cavity, for carrying out a direct detection of the quantity of interest. Also in this case, the two circuit patterns are connected together by means of metallized holes, i.e., holes that traverse the sensor body in a peripheral position with respect to the blind cavity, in which an electrically conductive material is contained. This material projects on the outside of the holes, at the corresponding ends, in order to be in electrical contact with respective track of the two circuit patterns. In the case of the pressure sensor of WO 2010/134043, even though the metallized holes are in any case hollow (given that the thickness of the conductive layer that covers the surfaces thereof is modest), there is no risk of passage through them of the fluid that is to be measured. In fact, in this application, the ends of the metallized holes at the lower face of the first part of body are obstructed or in any case isolated from the fluid by the second body part that defines the membrane.

Also in the case of WO 2014/097255 A, the metallized holes are empty, and their ends at the lower face of the sensor body are obstructed via a protective layer of electrically insulating material, that is to cover for the most part the corresponding second circuit pattern, to which the temperature sensor is connected. In any case, in the pressure sensor referred to in the prior document in question, the area of the lower face of the sensor body where the bottom ends of the metallized holes are located is isolated from the fluid by virtue of the presence of an annular seal. This seal provides for axial fluid-tightness on the aforesaid protective layer so as to circumscribe a volume that can be occupied by the fluid that is to be measured, and the area where the ends of the metallized holes closed by the protective layer are located is in any case outside this volume, thus not being reachable by the fluid.

In a possible variant embodiment of WO 2014/097255, at least one of the metallized holes is defined in the sensor body so that its end at the lower face is located within the region circumscribed by the aforesaid seal, i.e., in a position that can be reached by the fluid. For this reason, according to the variant in question, the metallized hole referred to is filled with a conductive material. Total filling of the hole may, however, prove problematical on account of the capillary dimensions, i.e., the very small diameter, of the hole with the risk that, albeit apparently plugged on the outside, in the inside air bubbles or cavities not filled by the conductive material are present, which are difficult to detect. This solution is moreover relatively costly, in so far as complete filling of the through hole or holes of the sensor body implies the use of a significant amount of conductive material, which in the case of pressure sensors is typically an alloy with a base of noble or in any case costly metals, such as a silver-palladium alloy. For this reason, in practice, the metallized holes may be filled only partially, i.e., only at the end of interest.

The present applicant has, however, found that in sensors obtained in this way, when these are used in combination with high-pressure fluids or in the presence of sudden pressure increases of considerable amount, there may occur in an altogether unforeseeable way deformations and/or extrusions of the material used for plugging the metallized hole. These deformations may create passages that set in communication the two opposite faces of the sensor body, i.e., that set in communication the face exposed to the fluid with the opposite face, which should, instead, remain protected and isolated, on account of the presence of circuit components that are unsuited for coming into contact with the fluid to be detected.

For a better understanding of this problem,FIG. 1Ais a schematic illustration, at an enlarged scale, of a sensor body SB provided with a through hole TH, the cylindrical surface of which is coated with a conductive layer CC, as mentioned previously. An end of the metallized hole TH-CC corresponding to the face UF of the sensor body SB exposed to the fluid is plugged via a mass of filler material PB deposited locally. The material PB may be an electrically conductive material, or else a resin, or other electrically insulating material. The filling mass is formed by depositing at the bottom of the metallized hole a drop of the material in question in the molten or liquid state.

As explained above, in the case of use of the sensor in combination with fluids at high pressure or in the presence of temporary increases in the normal working pressure, it may occasionally happen that the mass of material PB is unable to withstand the thrust exerted by the pressure (represented schematically by the arrow designated by P inFIG. 1B), with consequent risk of deformation and/or extrusion of the material that plugs the hole TH. This deformation and/or extrusion may lead also to creation of a passage TP that enables outflow of the fluid through the metallized hole, as highlighted inFIG. 1C, thereby setting in direct communication with the two opposite faces of the sensor body.

AIM AND SUMMARY OF THE INVENTION

The aim of the present invention is basically to overcome the drawbacks mentioned previously in a simple, inexpensive, and reliable way.

The above aim is achieved, according to the invention, by a sensor for detecting at least one physical quantity of a fluid, in particular a pressure, and by a device integrating such a sensor, which have the characteristics referred to in the annexed claims, the claims forming an integral part of the technical teaching provided in relation to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Reference to “an embodiment” or “one embodiment” in the framework of the present description is intended to indicate that a particular configuration, structure, or characteristic described in relation to the embodiment is comprised in at least one embodiment. Hence, phrases such as “in an embodiment” or “in one embodiment” and the like that may be present in various points of this description, do not necessarily all refer to one and the same embodiment. In the framework of the present description, where not otherwise specified or when not immediately evident from the context described, definitions of position such as “top”, “bottom”, “upper”, “lower”, “lateral” and the like are meant to refer to the arrangement illustrated in a given figure. Moreover, particular configurations, and/or structures, and/or characteristics described may be considered individually or combined in any adequate way, in one or more embodiments, even different from the embodiments described hereinafter by way of non-limiting example. The references used in what follows are provided only for convenience and do not define the sphere of protection or the scope of the embodiments.

InFIGS. 2-5, designated as a whole by1is a sensor for detecting at least one quantity of a fluid according to an embodiment of the present invention. In the example illustrated, the sensor is a pressure sensor, in particular a pressure sensor of the first type referred to in the introductory part of the present description. The sensor1has a sensor body2, preferably made of electrically insulating material, such as a ceramic material or the like, for example alumina, or a polymeric material. The body2is preferably monolithic with two opposite faces2aand2band a peripheral face2c, for example with a generally cylindrical shape. In embodiments not represented herein, the body2may have a shape different from the one exemplified, for example generally parallelepipedal or prismatic. The sensor body2may also comprise a number of parts associated to one another, for example glued or welded, such as a tubular or axially hollow part and a membrane part fixed at one end of the tubular part, or again—in the case of a sensor of the second type, as referred to in the introductory part—may include a main part defining a blind cavity and an additional membrane element, for example glued, for closing the aforesaid blind cavity; alternatively, the aforesaid main part may include a passage in order to provide a pressure sensor of the third type described in the introductory part.

Defined in the body2is an axial blind cavity, designated by3inFIGS. 2 and 5. The cavity3is closed at the end face2bof the body2by a corresponding elastically deformable portion, which is designated by4inFIG. 5(see alsoFIGS. 8 and 9) and is referred to hereinafter also as “membrane portion”, and is instead open at the opposite end face2a. The thickness of the elastically deformable membrane portion4may be predefined according to the pressure range to be measured and/or to the maximum pressure that the sensor has to withstand, in particular envisaging a thickness of the portion4that is greater, the higher the pressure to which the device is subjected. Preferably, a thickness of the membrane portion4comprised between ⅓ and ⅕ of the thickness of the body2is envisaged. The cavity3is designed to receive, through its opening corresponding to the face2a, a fluid, for example a liquid or a gas, of which at least one quantity is to be detected, here represented by a pressure.

The pressure sensor1comprises a circuit arrangement supported by the sensor body2. This arrangement is represented in a partial and schematic way inFIGS. 6 and 7, in isolation from the sensor body, where it is designated as a whole by5. The circuit arrangement5comprises a first electrical circuit pattern, designated as a whole by6inFIGS. 6 and 7, designed to be at the face2bof the body2. The circuit pattern6comprises a plurality of tracks made of electrically conductive material, for example a metal or a metal alloy (such as a silver-palladium alloy), preferably silk-screen printed or in any case deposited on or associated to the face2bof the body2, on its side external to the cavity3, as is visible, for example, inFIG. 8. Some of the aforesaid tracks are designated by6ainFIGS. 6-8. Consequently, in the preferred embodiment, the insulating material constituting the body2is exploited directly as substrate for at least part of the circuit arrangement5.

Connected to the circuit pattern6is a plurality of corresponding circuit components, comprising means for detecting bending or deformation of the membrane3, for example of any type known in the sector, as mentioned in the introductory part, such as a bridge of resistors, or piezo-resistors, or piezo-resistive elements, referred to hereinafter for brevity also as “resistances”, irrespective of the corresponding connection or configuration.

Also one or more of these components may be directly formed on the face2b, for example in the form of screen-printed or deposited resistances. By way of example, inFIGS. 7 and 8designated by R are four resistances forming parts of a sensing bridge, made of resistive or piezo-resistive material (for example, a resistive or piezo-resistive paste) deposited on the face2bat the membrane portion3, in particular in a region thereof subject to elastic deformation, and connected to respective tracks6aof the circuit pattern6. In the case exemplified, the control electronics of the pressure sensor1is in a remote position and connected to the circuit arrangement5via suitable terminals (described hereinafter). In variant embodiments (not illustrated), the control electronics of the sensor may include one or more components—for example, processing components and/or amplification components, such as integrated circuits or chips—supported directly by the sensor body2and electrically connected to one of its circuit patterns, in particular to the circuit pattern6.

It should be noted that inFIGS. 3 and 4the circuit pattern6, with the corresponding components R, is coated with a protective layer L1of electrically insulating material, such as a layer of polymeric or vitreous material.

The circuit arrangement5comprises a second electrical circuit pattern, designated as a whole by7inFIGS. 6 and 7, which is located at the face2aof the body2. The circuit pattern7comprises one or more tracks of electrically conductive material, for example a metal or a metal alloy (such as a silver-palladium alloy), for example silk-screen printed or deposited on, or in any case associated to, a region of the face2athat is in a position peripheral with respect to the opening of the cavity3.

In various embodiments, one or more of the circuit patterns6and7comprises/comprise a plurality of tracks of electrically conductive material, such as a metal or a metal alloy, which are fixed or glued or engraved on the respective face2band2aof the body2, or else tracks fixed or glued or deposited or silk-screen printed or engraved on a different support, such as a circuit support, associated to the body2.

In a preferred embodiment, a track of the circuit pattern7at least partially surrounds the opening of the cavity3. In the case exemplified, the track designated by11surrounds the opening of the cavity3completely. In various embodiments, the aforesaid track has a circular closed-ring shape and is set around the opening of the cavity3, in particular to define an area resting on which, directly or with interposition of a layer of other material, is a circular sealing element, such as an O-ring.

In one embodiment, electrically connected to the second circuit pattern7is at least one circuit component, in particular a sensor means for detecting a physical characteristic or quantity of the fluid other than the pressure. In the example illustrated (seeFIGS. 2, 6, and 7), this component—designated as a whole by8—has an active part8athat is to be exposed to the fluid and at least two connection terminals8b. In a preferred embodiment, the component8is a temperature sensor, such as a resistor performing functions of temperature sensor, for example an NTC (negative-temperature coefficient) resistor, the active part8aof which (i.e., the part performing sensing functions) is to be exposed directly to the fluid in order to carry out direct detection of temperature. Not excluded from the scope of the invention is the use of different types of sensors, not necessarily temperature sensors.

With reference to the example shown, the terminals8bof the sensor8are in the form of reophores or legs, designed to be soldered to respective connection pads, belonging to the circuit pattern7. Not excluded from the scope of the invention, instead of components with reophores or legs, is the use of electronic components of a surface-mount (SMD) type, preferably provided with small metal terminals, for example in the form of pads or metallized ends, designed to be soldered directly on conductive tracks of a circuit pattern, in particular using a solder paste. Components of an SMD type that may be used for the purposes of implementation of the invention preferably have small dimensions, also so as to be more easily coated with a possible protective material, such as a thermally conductive but electrically insulating material and/or a material for protection against corrosion.

In embodiments where the pressure sensor according to the invention is designed for possible use in combination with electrically conductive liquids, there may advantageously be provided an appropriate electrical insulation of the electrical parts (such as electrical tracks and components) exposed to the fluid, for example via a protective polymeric coating, or a coating made of vitreous material or some other electrically insulating material; as has been said, this type of protection may be facilitated by the use of electronic components of an SMD type.

It may be noted that inFIG. 2the circuit pattern7is prevalently coated with a protective layer L2of electrically insulating material, such as a layer of polymeric or vitreous material, which is locally open at pads for connection of the sensor8, or in any case shaped so as to leave these pads exposed to enable soldering or connection of the terminals of the sensor8.

In one embodiment (see, for example,FIG. 12), an annular sealing element9, in particular of an O-ring type, is designed to rest directly on the protective layer L2and circumscribes a region where the opening of the cavity3is located and within which the sensor8is positioned.

According to various embodiments (not shown), the protective layer L2is absent or does not cover the annular track11of the circuit pattern7. In these embodiments, an annular sealing element similar to the one designated by 9, in particular of an O-ring type, is designed to rest directly on the track11and circumscribes a region where the opening of the cavity3is located and within which the sensor8is positioned.

The circuit arrangement5moreover comprises contacts or terminals for electrical connection of the sensor1to a generic external system (such as the control electronics of the sensor), the contacts or connection terminals of which are connected to electrically conductive tracks of at least one of the circuit patterns6and7. In an embodiment, such as the one represented, terminals (some of which are designated by10) are provided, which extend longitudinally and are made of electrically conductive material and are mechanically coupled to the face2bof the sensor body2in an area that is peripheral with respect to the membrane portion3and electrically connected to tracks6aof the circuit pattern6. In variant embodiments, the terminals may have a different form, for example they may be of an elastic or spring type, or represented by simple pads or contacts, or be obtained according to other techniques in themselves known.

In one embodiment, the circuit pattern7comprises a track that defines, or that is electrically connected to, at least one pad, for connection of a terminal or reophore8bof the circuit component represented here by the sensor8. In the example shown (seeFIGS. 6-7), the aforesaid track, designated by11, has an annular shape and is obtained by deposition of conductive material, for example of the type mentioned above, on the face2aof the sensor body, to surround the opening of the cavity3. Designated by12ais the aforesaid pad for connection of a reophore8bof the sensor8, which is preferably located within the ring defined by the track11and is connected to the latter via a corresponding portion of track11a(see alsoFIG. 12). The pad12apreferably has the same thickness as the track11, but represented in the figures, on its upper side, is a filler material—for example a solder paste—used for electrical and mechanical connection of the corresponding reophore8bof the sensor8.

The circuit arrangement5further comprises means for electrically connecting together the two circuit patterns6and7, i.e., for connecting the circuit pattern7directly or indirectly (via the circuit pattern6) to one or more respective terminals10. These connection means comprise at least one track or metallization obtained in a respective through hole of the sensor body2, which extends axially between the faces2aand2b. Preferably, as in the case represented, two of these holes are provided with surface metallization: these holes, which are preferably but not necessarily in positions substantially opposite with respect to the opening of the cavity3, are designated by14and15inFIG. 5. Preferably, located on the inner surface of each hole14and15is a respective layer of electrically conductive material or “metallization”, for example of the type already referred to above, which extends throughout the length and/or surface of the corresponding hole, as far as its two ends, preferably coming out therefrom on the faces2aand2bof the body2, in particular to form, or be connected to, respective contact pads, such as circular pads or electrical tracks, possibly forming part of the circuit patterns6and/or7.

Preferably, then, deposition of the material of these layers is carried out in way such that part of the metal or conductive material projects on the outside of the holes14and15, at the corresponding ends and/or the aforesaid respective pads. For simplicity, in what follows, the connection means between the circuit patterns6and7will be defined also as “metallized holes”.

The layers of conductive material in the holes14and15are designated by14aand15a, for example inFIGS. 6 and 7, and preferably have a tubular or hollow cylindrical shape, it being, however, possible for them to have a different configuration. If need be, the holes14and15could be at least partially filled with other material, such as a soldering material and/or a sealant. The layers14a,15amay be obtained with any technique known in the sector, for example via deposition, or silk-screen printing, or filling and suction.

In the same figures, designated by14band15bare the contact pads defined at or connected to the lower ends of the layers14aand15a, i.e., at the face2aof the sensor body2; designated, instead, by14cand15care the contact pads defined at or connected to the upper ends of the layers14aand15a, i.e., at the face2bof the sensor body2. The pads14b,15b,14c,15cpreferably have an annular shape; i.e., they are open at the centre.

In the embodiment exemplified, as may be noted, for example inFIGS. 6-7, the conductive layer14ais designed to connect the track11of the circuit pattern7to a first terminal10, via a track6aof the circuit pattern6. For this purpose, preferably the end pad14bis connected to the track11via a respective portion of track11b(see alsoFIG. 12), whereas the end pad14cis connected to the aforesaid first terminal10via a track6a.

Once again with reference to the embodiment exemplified inFIGS. 6 and 7, designated by12bis a second pad for connection of the second reophore8bof the temperature sensor8. This pad12b, which is also represented in various figures with the soldering material of the corresponding reophore8b, is preferably located within the ring defined by the track11. The pad12bis electrically insulated from the track11and, in the example, is connected to the conductive layer15aof the hole15, which is in turn electrically connected to a second terminal10, via the circuit pattern6. For this purpose, preferably, the pad12bis connected, for example via a corresponding conductive track13of the circuit pattern7, to the end pad15band hence to the layer15a(see alsoFIG. 11), whereas the end pad15cis connected to the aforesaid second terminal10via a further track6aof the circuit pattern6. In the case exemplified, the pads12a,12bfor connection of the temperature sensor8are in positions diametrally opposite to the cavity3, but this does not constitute an essential characteristic, it being possible to locate them in other areas within the track11.

According to an inventive characteristic, on the face of the sensor body2that faces the fluid, here represented by the face2a, the metallized hole or each metallized hole of the sensor1is occluded via a closing member having at least in part a pre-formed body, i.e., a body on at least one portion of which there is bestowed a substantially predefined shape before it is mounted on the sensor body. In the figures, designated for this purpose by30are the members for closing the metallized holes14-14aand15-15a, a possible embodiment of which is illustrated inFIGS. 13-16, where the pre-formed body is designated by30a.

In a preferred embodiment, the pre-formed body30aof each member30has at least one closing portion31. In various embodiments, the closing portion31is cylindrical or shaped like a disk having a diameter D1larger than that of the corresponding hole14or15, or else comprises at least one circular part having such a diameter D1that is designed to rest on at least one corresponding pad14bor15b. According to other embodiments, the closing portion31may have a different perimetral profile or cross-sectional dimension (i.e., a cross-sectional dimension in a direction radial or orthogonal with respect to the axis of the hole), but in any case a shape inscribed in which is an imaginary circular region of diameter D1(for example, the portion31could have a polygonal shape, inscribed in which is an imaginary cylindrical or disk-shaped portion of diameter D1).

As represented inFIG. 16, the diameter D1of the closing portion31is larger than the diameter DHof the hole14(or15) provided with the corresponding metallization14a(or15a). In this way, the closing portion31remains on the outside of the metallized hole14-14a(or15-15a), it being able to cover completely the corresponding end opening thereof. The diameter D1is predefined in the stage of design of the closing portion31, such as to cover or close completely the corresponding end opening of the metallized hole14-14aor15-15a, even in the conditions of different tolerances of size of the device1and/or of positioning of the closing member30with respect to the corresponding metallized hole that are typical of industrial production of sensors or circuits.

In the case of the embodiment referred to inFIGS. 13-16, the pre-formed body30aof the closing member30comprises, in addition to the closing portion31, also a positioning or centring portion, designated by32(hereinafter defined for brevity also simply as “centring portion”), which extends underneath the portion31. Preferably, the centring portion32has a cylindrical or tubular shape having a diameter D2smaller than the diameter D1, in particular smaller than that of the corresponding metallized hole14-14a,15-15a. According to embodiments not represented, the centring portion32may have other shapes suited to the purpose, and in particular a shape designed to be inscribed or contained in a circle of diameter D2(for example, a polygonal or star shape that can be inscribed in a circle of diameter D2).

In a preferential embodiment, the centring portion32has a diameter D2(FIG. 16) that is smaller than the diameter DHof the metallized hole: in this way, the centring portion32facilitates mounting of the member30on the sensor body2, moreover ensuring correct positioning of the closing portion31relative to the metallized hole. For this purpose, in a preferred embodiment of the invention, the diameters of the hole with the corresponding metallization, of the closing portion31, and of the centring portion32are such that, for any centring position that may be assumed by the portion32in the metallized hole, the closing portion31always obstructs the end opening of the hole. The concept is well exemplified by the comparison betweenFIGS. 14 and 15, which illustrate a position of the portion32perfectly centred in the hole (FIG. 14) and a position completely off centre of the portion32in the hole, i.e., up against the conductive layer14a(FIG. 15): as may be noted, also in this position, the portion31covers the end opening of the metallized hole14-14acompletely.

In general, in an embodiment of the type represented inFIGS. 13-16, where the portion32starts from a central area of the underside of the portion31, half of the difference between the diameter D1of the closing portion and the diameter D2of the centring portion is greater than the difference between the diameter DHof the metallized hole and the diameter D2of the centring portion32.

In various embodiments, the positioning or centring portion32may also have a shape and size such as to cause an albeit minimal interference with the inner surface of the hole14(or15), i.e., with the corresponding metallization14a(or15a), in particular in order to cause a mutual mechanical fixing, for example in order to keep the closing member30temporarily in position, in particular in the steps that precede fixing or soldering of the closing portion31to the circuit pattern7and/or to the corresponding pad14bor15b. For this purpose, the centring and/or fixing portion32could also have a shape that is at least in part conical, or else have two different diameters of which one is designed to provide the aforesaid interference or again presents a surface knurling or is shaped with radial reliefs (for example, with a cross section substantially shaped like a star, with points of the star designed to provide the aforesaid interference with the corresponding metallized hole14a). Of course, for these cases, the shape and/or sectional dimensions of the portion32will be chosen so as to cause an interference that will not damage or will not jeopardize operation of the metallization14aor15a, for example a shape that, if need be, is in part deformable.

The closing portion31is preferably shaped like a plate, whilst the portion32—if present—preferably has the shape of a pin or relief projecting from the portion31. In alternative embodiments, the portion32comprises a number of parts in relief, such as three pins arranged in a triangle or a number of pins arranged at the vertices of a polygon that can be inscribed in a circle of diameter D2or DH.

In the embodiment illustrated by way of example inFIGS. 13-16, the portions31and32have a circular outer profile, the former being shaped like a small disk and the latter being cylindrical. It will be appreciated, however, that—as has been said—these shapes, albeit preferred, are not strictly essential for the purposes of implementation of the invention, and may be different. The portion31could in fact have a peripheral profile that is polygonal, elliptical, etc.; similar considerations apply to the portion32, if present.

In various embodiments (not represented), the upper side or surface of the portion31could have a shape different from the one here represented as plane, for example at least in part curved or prismatic, for instance hemispherical. Also the underside or lower surface of the portion31could have a shape different from the one here represented as plane, but in any case such as to perform the function of closing the corresponding metallized hole. For instance, the lower surface of the portion31could be in part curved or prismatic, for example recessed. Also for these cases, the lower surface of the portion31is preferably provided with a profile designed to mate in a uniform way with the area of the pads14bor15b, such as a plane coupling profile or surface: this also in order to obtain a good fluid-tightness against any infiltration of the fluid into the coupling area, in particular after a corresponding gluing or soldering. The peripheral and/or upper and/or lower surfaces of the portion31preferably have a shape designed to enable easy soldering or fixing of the portion31to the pads14bor15band/or a shape designed to enable a further coating of the portion31via a coating and/or protective material, such as a resin or a sealant.

In various embodiments, the shape of the portion31of the member30is such as to provide also an electrical terminal, preferably via a relief that extends from the upper face of the portion31, for example for soldering and/or fixing of a component of the circuit arrangement (for instance, an electrical terminal of the sensor8: in this case, the terminal of the sensor8may be connected directly to the member30instead of to a corresponding pad12aor12b).

Of course, the metallized holes14-14a,15-15ado not necessarily need to have a circular cross section either. The term “diameter” used here is hence to be understood in general, and consequently also as indicating perimetral dimensions or cross-sectional dimensions of the body30aof the closing member30that correspond to an area or a perimeter or a cross section of the portions31and/or32and/or of the corresponding metallized hole.

The pre-formed body30aof the member30, whether comprising or not the centring portion32, is preferably made of at least a metal material or a metal alloy, such as copper, or copper alloys, preferably tinned or coated with other metal or alloy, in particular a material designed to facilitate soldering or gluing. Preferably, the pre-formed body30ais made of a single piece, obtained for example via machining operations, such as blanking and/or upsetting and/or turning, or else the member30is formed at least in part via stamping, such as deformation using a die or injection of molten metal material into a die.

For instance, in one embodiment, the body30aof the member30(even when it comprises only the closing portion31) is obtained starting from a metal bar appropriately machined via turning, or else from a metal bar shaped via blanking and/or stamping; alternatively, an end portion of a metal bar could be deformed via an upsetting operation to obtain the portion31. The body30aof the member30may be also obtained via a process of micromelting or stamping of molten metal material.

The closing member30and/or at least the portion31of its body30ais preferably made of a material having a hardness and/or a mechanical strength greater than that of the materials commonly used for occluding the metallized holes provided according to the known art, in particular a material having a deformation strength and/or a shear strength greater than those of an alloy for soldering circuits.

The member30, and in particular its closing portion31, enables a sealing or closing of the metallized hole14to be obtained that is substantially immune from any deformation or extrusion, which is typical instead of the masses of soldering or closing material used in the traditional technique, as exemplified inFIGS. 1A-1C.

In various embodiments, the shape and/or dimensions of the body30aor of its portion31are preferably defined also taking into account the corresponding material, for example it being possible to define a diameter and/or a thickness of the portion31that is all the smaller (obviously compatibly with the diameter of the metallized holes), the higher the mechanical strength of the material used. In various embodiments, the annular area of resting of the portion31of the member30on the pad14bor15bmay be defined beforehand so that it will be possible to withstand the thrust loads due to the pressure of the fluid. In the case of the example ofFIG. 16, the aforesaid annular area substantially corresponds to the circular area defined by the diameter D1minus the circular area defined by the diameter DHof the circular hole, not considering the area defined by a possible chamfer.

In various embodiments, the thickness and shape of the portion31of the member30may be determined in such a way as to define a substantially annular area capable of withstanding the force or pressure of the fluid, in particular a pressure of some hundreds of bar and/or a force in a direction substantially parallel to the axis of the metallized hole14,15, such as a force of some kilograms, for example a pressure comprised between 1 kg/mm2and 4 kg/mm2

The aforesaid substantially annular area of resting of the portion31is preferably greater than the area corresponding to the metallized hole14-14a,15-15a, in particular a value of surface corresponding to at least twice the area that corresponds to the metallized hole14-14a,15-15a.

Merely by way of example, the portion31may have a thickness comprised between approximately 0.15 and 0.3 mm, preferably approximately 0.2 mm. With a metallized hole having an internal diameter of between approximately 0.6 and approximately 1 mm, preferably 0.8 mm, the portion31may have a diameter D1of between approximately 1 mm and approximately 1.6 mm, preferably 1.4 mm, whereas the portion32—if present—may have a diameter D2of between approximately 0.59 mm and approximately 0.99 mm, preferably 0.6 mm.

In a preferred embodiment, the end of the metallized hole where a closing member30is to be mounted, provided with centring portion32is shaped so as to define a lead-in portion or a flaring, for example a chamfered profile or a profile inclined with respect to the axis of the hole in order to facilitate insertion of the portion32into the hole. For this purpose, in the embodiment provided by way of example represented inFIGS. 13-16, the end of the hole14includes a substantially frustoconical stretch, designated by FC only inFIGS. 14-16, with the corresponding conductive layer14aor15athat has a corresponding shape in this region. Preferably, the lower end of the portion32is shaped so as to favour insertion of the portion itself in the metallized hole; in the case exemplified, this lower end has a profile or a chamfered, or inclined, or rounded peripheral edge, designated by32aonly inFIG. 13, but other shapes suitable for the purpose are obviously possible, such as a generally pointed or hemispherical shape or a frustoconical shape that is more marked as compared to the case illustrated.

According to a further inventive characteristic, at least one portion of the pre-formed body30aof the member30, preferably its closing portion31, is fixed in a fluid-tight way to the corresponding metallized hole. Preferably, the aforesaid portion31is fixed in position via at least one of a fixing material and a sealing material, for example a soldering material, a gluing material, or a resin. In various embodiments, a first material may be provided for local fixing in position and/or for obtaining a first seal of the portion31, and a second material may be provided for guaranteeing or improving the necessary fluid-tightness of the portion31with respect to the corresponding metallized hole. In an embodiment of this type, for example, the first fixing and/or sealing material may be a soldering or gluing material, whereas the second sealing material may be a soldering material, or a resin, or a polymer. In various other preferred embodiments, instead, a single material is provided, which performs simultaneously functions of fixing in position and functions of tightness, such as a soldering material (for example, a metal alloy), or a gluing material, or a resin, or a polymer. In the figures, such a material, which simultaneously performs fixing and sealing functions, is designated by 35.

In a preferred embodiment, the material35is set at least on the end face of the sensor so as to surround the closing portion31of the member30peripherally in order to ensure fluid-tightness between this face and the peripheral surface of the portion31. The material35used presents characteristics such as to fix the member30in position, in addition to guaranteeing the necessary fluid-tightness. For this purpose, preferably, the material35is a material or a metal designed to weld or bond chemically and/or structurally to the material of the portion31and to the material of the corresponding pad14bor15b. Of course, the material35may also be deposited so as to extend at least in part over the upper surface of the portion31and/or coat this portion completely, possibly extending at least in part between its lower surface and the corresponding pad14bor15b.

In a preferred embodiment, the fixing and/or sealing material is a weld material or an added material, with the body30aof the member30that is fixed in position in a fluid-tight way via soldering or sealing or gluing.

In a different embodiment, the fixing and/or sealing material is a material that provides or coats at least in part one of the closing member30and the circuit pattern7and pads14b,15b, with the portion31of the member30that is fixed in position in a fluid-tight way via soldering. For instance, the body30aof the member30and/or the pads14b,15bmay be initially coated with a soldering material (for example, they may be pre-tinned), this material being is then re-melted to bring about sealing and/or fixing, and hence without any need for a further addition of solder alloy. In addition or as an alternative, such a material designed to remelt may be provided within a metallized hole, the material coating the corresponding metallization at least in the part of hole that is to receive a portion of the pre-formed body, for example the portion32. The material designed to remelt may also comprise a surface layer of part of the pre-formed body or of the metallization of the hole.

Preferably, the end pad14bor15bwhere the member30is located has a diameter larger than the diameter of the closing portion31. Preferably, the diameter of the portion31of the member30and the diameter of the pad14bor15bin question are such that, for any position of centring of the former with respect to the latter, a peripheral annular part of the pad projects laterally from the closing portion31. Also this concept emerges from the comparison betweenFIGS. 14 and 15.

In this way, as may be appreciated, the side or the lower surface of the portion31rests on the pad14a(or15a), with the aforesaid peripheral part of the latter that in any case projects laterally. In an implementation of this sort, the fixing and/or sealing material, such as the material35, in particular a weld or added material, may be a material used for fixing or soldering together at least the aforesaid peripheral part of the pad in question and the lateral surface of the closing portion31of the member30, as exemplified for instance inFIGS. 14-16.

The material35, in the case of soldering, is preferably a metal material or a metal alloy, for example with a base of indium, and/or tin, and/or lead. In possible variant embodiments, on the other hand, the material35is a solder paste or a glue designed to ensure positioning and fluid-tightness at high pressures, preferably pressures of up to at least 400 bar.

The arrangement of the closing members30according toFIGS. 13-16at the lower ends of the metallized holes14-14aand15-15ais clearly visible also inFIG. 10and in the details represented inFIGS. 11 and 12, where also the portions11aand13of track for connection of the pads12a,12bare clearly visible.

FIGS. 17-19illustrate an embodiment according to which the pre-formed body30aof the closing members, here designated by30′, consists only of the closing portion31, here exemplified in the form of a disk-shaped plate, which may be made and/or fixed according to what is described in reference to the previous example ofFIGS. 13-16. This type of implementation presupposes a higher operating precision in positioning of the member30at the end of the corresponding metallized hole, given the absence of a centring portion, but presents the advantage of simplifying the formation of the member itself, which, for example, may be obtained via blanking from a metal strap. This solution enables also saving of material for production of the pre-formed body.

For the rest, also in this case the members30′ fixed in position via the corresponding material35ensure closing in a fluid-tight way of the metallized holes, without any risk of deformation and/or extrusion with consequent passage of the fluid, as described in the introductory part of the present disclosure.

In preferred embodiments of the invention, the pre-formed body30aof the closing member extends on the outside of the corresponding metallized hole, as in the case of the member30′, or else extends only partially into the corresponding hole, for a limited stretch of the length of the hole itself, as in the case of the member30. In this way, any risk of anomalous electrical contacts or even failure of the closing member following upon thermal expansion are prevented. From practical tests conducted by the present Applicant, the latter has noted that these problems may arise in the case of closing members aimed also at replacing the surface metallization of the through holes, i.e., members that extend completely between the two faces of the sensor body until they come out of the two ends of the hole, for example members substantially in the form of rivets or metal terminals mechanically upset at their two opposite ends, outside the hole. In these cases, there may occasionally occur expansion of such a member, which is greater than that of the sensor body. This causes mechanical stresses on the member, at the opposite end of the hole, which may give rise to false contacts with the corresponding track of the circuit pattern on account of the fact that the head of the rivet or the upset end of the terminal tends to rise with respect to the corresponding face of the sensor body. For the same reasons, there may arise also occasional failure of the conductive tracks or of the pads, if the ends of the rivet or of the terminal are soldered to the tracks or pads themselves.

The above problems are prevented in the preferred case of closing members30′ external to the hole or of closing members30that extend only partially into the metallized hole, for a limited part of its length. In these embodiments, the closing member is fixed in position at just one end of the hole; i.e., it is not fixed at the other end of the same hole, thereby preventing mechanical stresses that could be the cause of cracks or failure following upon thermal expansion.

In various embodiments, the closing members30and/or30′ may have a shape and/or dimensions such as to enable easy handling thereof for them to be picked up, and/or moved, and/or positioned for their installation on the pressure sensor1. For instance, a shape and size may be chosen to enable handling of a member30or30′ using a small suction pad or a suction device or vacuum device, such as a device for manual pick-up or a device belonging to an automatic assembly system. For this purpose, for example, an automated system may be used of the type employed for handling and mounting SMD components, such as a system of the pick-and-place (P&P) type, which in particular is designed to pick up the closing member30or30′ via suction or vacuum.

For this purpose, the upper part of the portion31of the body30amay be provided with a surface designed for the P&P system, such as a smooth surface or a surface finished in such a way as to enable tightness when suction is exerted by a small suction pad or when vacuum is brought about. In order to facilitate picking-up, the closing members30or30′ may be pre-arranged in purposely provided containers or on strips, in particular in a position such as to expose the aforesaid upper surface of the portion31.

As mentioned previously, the circuit pattern7is practically entirely coated with a protective layer L2of electrically insulating material, in particular a vitreous or polymeric material, applied on the face2aof the body2. In a preferred embodiment, as may be appreciated, for example, inFIGS. 2 and 20, the protective layer L2has passages or openings (not represented) so as to leave exposed the connection pads12aand12bof the sensor8, as well as passages or openings so as to leave exposed the pads14b,15band the head of the closing members30, with the corresponding fixing and/or sealing material, for example the material35, that performs both of functions. Such a measure enables, for example, mounting and connection of the sensor8, as well as mounting and fixing in a fluid-tight way of the members30, even after arrangement of the layer L2. On the other hand, in different embodiments, the layer L2could be provided following upon mounting of the sensor8and/or of the members30, also so to coat at least partially the pads12a,12band/or the pads14b,15b, and/or the portion31of the members30or30′ with the corresponding material35.

In a variant embodiment of this type, it is also possible to omit the material35, the sealing functions of which can be performed directly by material of the protective layer L2. As already mentioned, in a case of this type other means may be provided to obtain fixing in position of the closing member30or30′, such as soldering of the closing portion31on the pads14bor15b, or else the aforesaid insertion with slight interference of the centring portion32in the corresponding metallized hole.

In the embodiment exemplified inFIGS. 2 and 20, the layer L2is deposited—for example via silk-screen printing—in way such that at least an annular part of its upper surface is as a whole substantially plane in order to provide a resting surface for the annular seal9. In a preferred embodiment of this type, the circuit pattern7comprises an annular track11, so that such an annular track or the part of the layer L2that covers it will enable simple definition of a uniformly plane resting base for the seal9.

It should be noted in any case that the diameter of the track11could even be smaller than the diameter of the seal9, in which case the latter can rest on the lower face2bof the sensor body2, possibly also in an peripheral area thereof not presenting parts of the circuit arrangement or a protective layer L2(in a way similar to what is illustrated inFIG. 22).

As may be noted inFIG. 20, in the case exemplified, both the pads12aand12band the members30that close the upper ends of the metallized holes are located within the region circumscribed by the seal9, thereby being exposed to the fluid. Provision of a member30with the corresponding sealing and fixing material enables solution of the problems highlighted in the introductory part of the present description.

FIGS. 21 and 22are schematic illustrations of an example of device for detecting the pressure of fluids that integrates a pressure sensor according to one of the embodiments described previously, and namely a sensor1, preferably but not necessarily with a protective layer L2of the type described with reference toFIGS. 2 and 20. Such a device, designated as a whole by100, may find use, for example, in the automotive sector, or in the domestic sector and the sector of electrical household appliances, or in the HVAC, plumbing, and sanitary sector.

With reference toFIG. 21, the device100has a casing body, formed for example by at least two body components101,102, coupled in a fluid-tight way so as to define between them a housing for the sensor1. In the case exemplified, the component101defines a tubular part103of an electrical connector, whereas the component102defines an inlet104, designed to be connected to a circuit, located in which is the fluid of which the pressure and temperature are to be detected (assuming—as in the case considered here—that the component8is a temperature sensor).

Visible inFIG. 22is the housing defined between the two components101,102, within which the sensor1is fixed with modalities in themselves known. From the figure it may moreover be noted how extending within the tubular part103of the component101are connection terminals103a, with which the terminals10of the pressure sensor1are electrically in contact. The pressure sensor1is mounted within the casing body101-102so that its lower face—located in which is the opening of the cavity3—faces the inlet104, within which the temperature sensor8preferably projects. Mounted between an upper face of the component102and the pressure sensor1is the seal9. Preferably, the aforesaid upper face of the component102is purposely provided with a positioning seat102afor the seal9, which rests on the opposite side on the lower face of the sensor, as explained previously.

As may be noted, with the arrangement illustrated, the seal9delimits peripherally a chamber or a volume V, within which the closing members30of the metallized holes are located.

General operation of the device20and of the pressure sensor1occurs according to known modalities, and consequently will not be described in detail here. As may be appreciated, the fluid at inlet from the passage104can reach the cavity3of the sensor body2, causing a bending thereof proportional to the pressure, which is measured via the corresponding sensing means R. The fluid, of course, also impinges upon the sensor8, enabling detection of the further quantity of interest, here represented by the temperature of the fluid. Also in the case of high pressures at the inlet104, the presence of the closing members30prevents any possible leakage of the fluid being detected through the metallized holes14-14aand15-15a, as explained previously.

The invention has so far been described with reference to the structure of a pressure sensor of the first type referred to in the introductory part of the present description. It will be appreciated, however, that the invention may likewise be applied also to pressure sensors of the second or third types referred to previously. Such a case is, for instance, exemplified inFIG. 23, where the same references as those of the previous figures are used to designate elements that are technically equivalent to the ones already described above.

In the case of the device ofFIG. 23, the sensor—here designated as a whole by1′—has a body made up of at least two distinct parts, comprising a first main body part2′, defining the corresponding axial cavity3, which is closed in at the face2b, in particular by a corresponding portion4′, which here does not perform the membrane function. The sensor body then comprises a membrane part4″, fixed in a fluid-tight way to the body part2′, in a known way, at the opposite end of the cavity3, i.e., at the face2a. In the non-limiting example, the face2ais provided with a recess (not shown), which is substantially coaxial to the cavity3, within which the membrane4′ is fixed, the recess and membrane preferably having a similar peripheral profile. In other embodiments (not represented), the aforesaid recess may be absent.

The side of the membrane4″ external to the cavity3is exposed to the fluid of which the pressure is to be detected, whereas its opposite side, facing the inside of the cavity3, carries at least one circuit component R for detecting bending or deformation of the membrane4″. The at least one component R may comprise, for example, a plurality of piezoelectric, piezo-resistive, or resistive elements, or else a respective part of a capacitive detector, the other part of which is associated to the main body2′, for example according to techniques in themselves known.

In the embodiment exemplified, the at least one component R is connected to the circuit pattern6provided on the face2avia metallized holes14′ and15′, which are made in a way similar to the holes14-14aand15-15a. It should be noted that, in this case, the holes14′ and15′ do not require respective closing members of the type designated by30or30′, given that the lower end thereof is in any case in a protected position, thanks to the presence of the membrane4″. The circuit pattern6is substantially of the type already described and illustrated previously, obviously modified with tracks and/or pads necessary for connection of the metallized holes14′ and15′.

In one embodiment, such as the one exemplified inFIG. 23, there is further provided the sensor8, for example a temperature sensor, mounted at the face2aand electrically connected to the circuit pattern6via the circuit pattern7and the metallized holes14-14aand15-15a. The circuit pattern7is similar or substantially similar to what has already been described previously, for example with at least one corresponding track of electrically conductive material, in particular an annular track, which is located on a region of the face2athat at least partially surrounds the membrane4″. Also the metallized holes14-14aand15-15aare made in a way similar or substantially similar to what has already been described, with the corresponding closing members30(or possibly30′).

In the case exemplified, the sensor1′ is of the third type described in the introductory part of the present disclosure; i.e., the sensor body2′,4″ has a passage for setting the inside of the cavity3in communication with the outside. In the example, such a passage—designated by16—is configured as a through hole of the portion4′ of the body2′, thus giving rise to a pressure sensor of the type generically known as “relative pressure sensor”. It will be appreciated, on the other hand, that in variant embodiments the passage16may be omitted or else sealed in the production stage, in which case the sensor1′ will be of the second type referred to in the introductory part, thus giving rise to a pressure sensor of the type generically known as “absolute pressure sensor”, i.e., one presenting a known reference pressure within the hermetically closed cavity3. For the rest, the structure of the device100illustrated inFIG. 23—including the arrangement of the annular seal element9—is substantially the same as the structure of the similar device ofFIG. 22.

As may be appreciated, in the case ofFIG. 23, the fluid at inlet from the passage104can impinge upon the exposed side of the membrane4″, causing a bending thereof proportional to the pressure, which is measured via the corresponding sensing means R. The fluid also impinges upon the sensor8, enabling detection of the further quantity of interest, here represented by the temperature of the fluid.

From the foregoing description, the characteristics of the present invention emerge clearly, as likewise do its advantages, which are principally represented by the simplicity, economy, and reliability of the proposed solution. Use of the members30or30′, with the corresponding fixing and sealing means (such as the material35or the material of the coating L2or the combination with a first, fixing, material and a second, sealing, material or a mechanical interference between the member30and the corresponding metallized hole, or combinations of these means) enables elimination of the problems described with reference toFIGS. 1A-1B, guaranteeing a high reliability of the sensor also in the long term. Practical tests conducted by the present applicant, with pressures of the fluid that is to be measured of up to 400 bar and with sizing of the metallized holes and of the closing members as exemplified previously, have made it possible to ascertain the effectiveness of the solution proposed.

It is clear that numerous variants to the pressure sensor described herein by way of example are possible for the person skilled in the branch, without thereby departing from the scope of the invention as defined in the annexed claims.

The electrically conductive track referred to inFIGS. 6 and 7, with the associated pads and/or the protective layers L1, L2can be obtained on the sensor body2with techniques other than silk-screen printing, even though this is the preferred technique; for example, alternative techniques in this sense may be selected from among lithography, photolithography, spraying or a jet of conductive material, surface metallization, plating, etc.

In possible variant embodiments, the sensor forming the subject of the invention may be equipped with a plurality of additional components of the type previously designated by 8, such as resistors or sensors, for example with electrical connection in parallel or else via a connection to further pads and tracks of the type exemplified.

The structure of the circuit pattern7could be of the type described in WO 2014/097255, i.e., configured for enabling connection of alternative components and/or connection according to a number of alternative modalities of one and the same component.

With circuit configurations different from the ones exemplified, the circuit pattern7could comprise a number of concentric conductive tracks or, instead of a single tracks11, a plurality of tracks could be provided forming an arc of circumference. The metallized holes could even number more than two, according to the circuit needs, at least one of which having an end located in an area that can be reached by the fluid, and hence provided with the corresponding closing member30.

Not excluded from the scope of the invention is the case of use of at least one of a fixing and/or sealing material that extends between the lower surface of the portion31and the corresponding pad14bor15b, and possibly between part of the outer surface of the portion32and a corresponding part of the surface of the corresponding metallized hole. Such a case is exemplified schematically inFIG. 24, where the same reference numbers as those of the previous figures are used to designate elements that are technically equivalent to the ones already described, amongst which a fixing and/or sealing material35. InFIG. 24the arrows F1are aimed at representing schematically the pressure of the fluid impinging upon the closing portion31of the member30.

The fixing and/or sealing material35between the lower surface of the portion31and the corresponding pad14b(or15b) has in any case a reduced thickness, in particular such as a thin layer or film. In embodiments of this type, the area of the material35possibly subjected to the pressure of the fluid on its outer profile (this pressure is represented schematically by the arrows F2) substantially corresponds to the aforesaid reduced thickness of the material35. The material35is thus able to withstand high mechanical stresses, or forces, or pressures F2of the fluid, even though the material itself has a hardness or strength lower than that of the closing member30. Similar considerations also apply in the case where the layer of fixing and/or sealing material that extends underneath the portion31of the member30belongs to a mass of the same material that also surrounds the portion31peripherally and/or coats it at least in part.