Patent Description:
Sensor devices, e.g. fluid sensor devices, may comprise a sensor, like a temperature sensor, and/or a mechanical resonator, like a tuning fork resonator. There are known sensor devices, like the sensor described in <CIT> and the fluid sensor described in <CIT>, that require interconnecting at least two Printed Circuit Boards (PCBs) and grounding the PCBs for electrostatic discharge (ESD) protection and for preventing electromagnetic interference (EMI noise).

Spring contacts, also known as spring fingers or ground contacts, are commonly used for grounding between a device and a PCB. Spring contacts are soldered onto a PCB. However, in many applications, like when the sensor device is implemented in a vehicle, vibrations can generate stress and fatigue on the solder joint between the spring contact and the PCB, thereby weakening the connection.

In some sensor device known from the prior art, like the sensor device <NUM> represented in <FIG>, the grounding of the PCBs <NUM>, <NUM> is carried out by means of a pin <NUM> soldered to the electrically conductive body <NUM> of the sensor device <NUM> and the PCB <NUM>. The PCBs <NUM>, <NUM> are interconnected by means of rigid connection means <NUM>. For protecting and insulating PCBs <NUM>, <NUM> and electronic components from the threats of harsh environments, the cavity <NUM> of the sensor device <NUM> can be filled with epoxy resin (this method is also known as PCB potting). Epoxy resin, however, due to its rigid material properties, does not allow dampening vibrations. Moreover, as it involves the installation of several elements (<NUM>, <NUM>), as well as steps of soldering and potting, the manufacturability of such sensor device is affected.

It is therefore an object to provide a simplified grounding solution for a sensor device with an improved resistance to vibrations and adapted for high volume production, i.e. with a higher manufacturability.

The above-mentioned object is achieved by means of the sensor device according to the independent claim <NUM>. Said sensor device comprises an electrically conductive body adapted to accommodate at least a first printed circuit board (PCB) and a second PCB. The first PCB and the second PCB are connected together by a flexible electrically conductive means and the sensor device further comprises at least one electrically conductive spring held between the two PCBs by a snap-fit, a form-fit or a press-fit connection such that a first portion of the spring is pressed against one of the PCBs and a second portion of the spring is pressed against the electrically conductive body to maintain an electrical connection between the electrically conductive body and the PCBs.

Hence, as the electrically conductive spring is held by a snap-fit, a form-fit or a press-fit connection, an electrical connection between the electrically conductive body and the PCBs, i.e. to perform the grounding function, can be maintained without the need of soldering the electrically conductive spring to the PCBs or the electrically conductive body. Instead, the electrical connection between the electrically conductive spring and the PCB is advantageously achieved by pressing a first portion of the spring against the PCB. Similarly, the electrical connection between the electrically conductive spring and the electrically conductive body is achieved by pressing a second portion of the spring against the electrically conductive body. Consequently, with respect to the known solutions for electrical grounding in sensor device, no soldered joint - and thus no electrical connection - can be damaged by vibrations. The combination of the solder-free solution to assemble the electrically conductive spring and the use of a flexible electrically conductive means, i.e. a flexible electrical connection such as PCB flex, allows avoiding the drawbacks caused by rigid connections, especially with respect to vibrations. Instead, the present invention provides a sensor device without rigid connections between the two PCBs. Moreover, as no soldering step is required to install the electrically conductive spring for ensuring the grounding function, the manufacturing is simplified, thereby improving the repeatability and reducing the cost of the assembly process. Consequently, the sensor device is rendered compatible for high volume production. In addition, as no specific soldering step is required for ensuring the grounding function, automation of the assembly process is rendered possible. Moreover, it allows providing a potting free assembly process, which improves further the manufacturability of the sensor device.

Advantageous embodiments of the sensor device are the subject matter of the dependent claims. The sensor device can be further improved according to various advantageous embodiments.

According to one embodiment, the sensor device can further comprise a plastic holder onto which the at least one electrically conductive spring is mounted, and the plastic holder can be disposed between the two PCBs, such that only one of the two PCBs is in direct surface contact with the plastic holder and the other of the two PCBs is in direct surface contact with the at least one spring.

The use of a plastic holder allows providing a solder-free solution.

Only one PCB is in direct contact surface with the plastic holder. It involves that the plastic holder lies on one PCB and is dimensioned such that the height of the plastic holder is smaller than the distance between the two PCBs in the assembled state of the sensor device. Therefore, a gap between the plastic holder and the other PCB (the one in contact with the spring) is generated. Hence, a minimum gap to strain relief is provided, allowing the PCBs to move with respect to each other by means of the spring. Consequently, the spring provides a combination of grounding function and strain relief function, in a solder-free assembly.

According to one embodiment, the plastic holder can comprise a base from which extends essentially transversally a receptacle adapted for partially receiving the at least one spring.

Hence, the receptacle of the plastic holder provides a holding feature for the mounting of the spring without the need of any fastener.

According to one embodiment, at least one guiding arm can extend from the first portion of the spring, said guiding arm being adapted to be received in a corresponding groove of the receptacle of the plastic holder.

The at least one guiding arm allows facilitating the mounting of the spring to the receptacle of the plastic holder by providing a guiding feature to the spring. It also allows ensuring a correct positioning of the spring with respect to the plastic holder.

According to one embodiment, the plastic holder can be held in position, in the assembled state of the fluid sensor, by means of a snap-fit, press-fit or form-fit connection with corresponding elements of the sensor device.

Hence, the assembly of the plastic holder can be easily carried out and does not require the use of any tools thanks to the snap-fit, press-fit or form-fit connection. The manufacturing of the sensor device can therefore be further simplified.

According to one embodiment, the plastic holder can have a circumference comprising at least one recess configured for receiving a corresponding locking element protruding from a first assembly element of the sensor device.

Hence, the plastic holder and the head assembly comprise structural features configured for realizing a snap-fit, press-fit or form-fit connection in the assembled state of the sensor device.

The first assembly element can be a header assembly of the sensor device in which terminals are received.

According to one embodiment, the plastic holder can comprise at least one receptacle configured for receiving a corresponding locking arm protruding from a second assembly element, the at least one receptacle comprising a locking arm such that in the assembled state of the sensor device, a snap-fit, press-fit or form-fit connection is formed between the locking arms respectively of the second assembly element and the plastic holder.

Hence, the plastic holder and the second assembly element, e.g. a connector, comprise structural features configured for realizing a snap-fit, press-fit or form-fit connection in the assembled state of the sensor device.

According to one embodiment, the at least one electrically conductive spring can be hold between the two PCBs by a snap-fit, press-fit and/or form-fit connection formed between the first portion of the spring and one of the PCB.

Hence, the grounding function and the strain relief function can be both achieved by means of the electrically conductive spring that can advantageously be hold without requiring any solder joint.

According to one embodiment, the first portion of the spring can comprise a main section terminated with a free-end section, the free-end section extending transversally from the main section through a corresponding through hole of the PCB.

The insertion of the free-end section of the spring in a corresponding through hole of the PCB allows providing a form-fit connection for maintaining the spring in place without the need of solder joints.

According to one embodiment, the at least one electrically conductive spring can be hold between the two PCBs so that the at least electrically conductive spring is in direct surface contact with both PCBs.

Hence, in comparison with the alternative of the plastic holder, a snap-fit, press-fit and/or form-fit connection can be directly formed by means of an already existing element of the sensor device (like an assembly pin of the assembly element). Such connections have the advantage to be solder-free, to not require additional element and can be carry out without the need of tool, i.e. allows simplifying the assembly.

According to one embodiment, the first portion of the spring can be a flat portion from which protrudes the second portion formed by a bent tab.

The flat first portion provides a well-adapted contact surface for ensuring the electrical connection when said first portion is pressed against the PCB. As the second portion protrudes from the first portion, the first and the second portions are merged so as to ensure a continuous electrical connection. The bent tab of the second portion is specially adapted to contact and be pressed against a wall of the electrically conductive body.

According to one embodiment, the first portion of the spring can be provided with a bump, such that the bump of the first portion is pressed against one of the PCBs, and the second portion can be formed by a bent tab and protrudes from the first portion.

The feature of the bump allows further improving the electrical contact between the spring and the PCB when the first portion, i.e. the bump, is pressed against the PCB.

As the second portion protrudes from the first portion, the first and the second portions are merged so as to ensure a continuous electrical connection. The bent tab of the second portion is specially adapted to contact and be pressed against a wall of the electrically conductive body.

According to one embodiment, the at least one electrically conductive spring can comprise a third portion extending from the first portion till a base of the spring, the base being geometrically opposed to the first portion such that the third portion is in a preloaded state between the first and the second PCBs.

The third portion of the spring being in a preloaded state between the two PCBs, the spring imparts a sufficient spring force along a direction transversal to the PCBs so as to provide a strain relief to the PCBS. Hence, the electrically conductive spring allows not only providing a grounding function but, in addition, a stress relief function which improves the holding of the PCBs, especially under vibrations, as no stress is caused on rigid connections (like solder joints). Hence, the two functions of electrical grounding and strain relief of the PCBs are advantageously carried out by means of one single component, the electrically conductive spring, that can be assembled to the sensor device without the need of soldering step.

According to one embodiment, the at least one spring can be integrally formed with a shielding base from which said spring extends essentially transversally therefrom, said shielding base being arranged parallel between the two PCBs.

Hence, the spring performing the grounding function can provide an additional function: a shielding function. When the shielding base is disposed between the two PCBs is allowed preventing cross talk (i.e. unintentional electromagnetic coupling) between the two PCBs.

The above-mentioned object is further achieved by means of a method according to the independent claim <NUM> for assembling a sensor device. Said method for assembling a sensor device comprises the steps of a) mounting at least one electrically conductive spring to a plastic holder, b) disposing the plastic holder onto a first PCB, the first PCB being connected to a second PCB by a flexible electrically conductive means, c) arranging the second PCB over the plastic holder so as to press a first portion of the spring against the second PCB , d) assembling an electrically conductive body for accommodating the PCBs so as to press a second portion of the spring against said electrically conductive body to maintain an electrical connection between the electrically conductive body and the PCBs.

Hence, the electrically conductive spring mounted in the plastic holder allows maintaining an electrical connection between the electrically conductive body and the PCBs, i.e. to perform the grounding function, without the need of being soldered to the PCBs or the electrically conductive body. Instead, the electrical connection between the electrically conductive spring and the PCB is simply achieved by pressing a first portion of the spring against the PCB. Similarly, the electrical connection between the electrically conductive spring and the electrically conductive body is simply achieved by pressing a second portion of the spring against the electrically conductive body. Consequently, with respect to the known solutions for electrical grounding in sensor device, no soldered joint - and thus no electrical connection - can be damaged by vibrations. The combination of the solder-free solution to assemble the electrically conductive spring and the use of a flexible electrically conductive means, i.e. a flexible electrical connection such as PCB flex, allows avoiding the drawbacks caused by rigid connections, especially with respect to vibrations. Instead, the present invention provides a sensor device without rigid connections between the two PCBs. Moreover, as no soldering step is required to install the electrically conductive spring for ensuring the grounding function, the manufacturing is simplified, thereby improving the repeatability and reducing the cost of the assembly process. Consequently, the method for assembling a sensor device is rendered compatible for high volume production. In addition, as no specific soldering step is required for ensuring the grounding function, automation of the assembly process is rendered possible. Moreover, it allows providing a potting free assembly process, which improves further the manufacturability of the sensor device.

Advantageous embodiments of the method for assembling a sensor device are the subject matter of the dependent claims. The method for assembling a sensor device can be further improved according to various advantageous embodiments.

According to one embodiment, at step a) a guiding arm of the spring can be received in a corresponding groove of a receptacle of the plastic holder.

Hence, the assembly of the spring to the plastic holder can be simplified thanks to the guiding feature provided by the guiding arm of the spring. It also allows ensuring a correct positioning of the spring with respect to the plastic holder.

According to one embodiment, at step c) the second PCB connected to a connector can be moved pivotally onto the plastic holder about a rotational axis transversal to the insertion direction.

Hence, the assembly of the sensor device is carried out by easy assembly steps that do not require any tools and are adapted for automation, thereby improving the manufacturability of the sensor device.

According to one embodiment, at step d) the plastic holder can be held in position by means of a snap-fit, press-fit or form-fit connection with corresponding elements of the sensor device.

Hence, the assembly of the plastic holder can be easily carried out and does not require the use of any tools thanks to the snap-fit, press-fit or form-fit connection. The manufacturing of the sensor devise can therefore be further simplified.

Additional features and advantages will be described with reference to the drawings. In the description, reference is made to the accompanying figures that are meant to illustrate preferred embodiments of the invention. It is understood that such embodiments do not represent the full scope of the invention.

The accompanying drawings are incorporated into the specification and form a part of the specification to illustrate several embodiments of the present invention. These drawings, together with the description serve to explain the principles of the invention. The drawings are merely for the purpose of illustrating the preferred and alternative examples of how the invention can be made and used, and are not to be construed as limiting the invention to only the illustrated and described embodiments. Furthermore, several aspects of the embodiments may form - individually or in different combinations - solutions according to the present invention. The following described embodiments thus can be considered either alone or in an arbitrary combination thereof. Further features and advantages will become apparent from the following more particular description of the various embodiments of the invention, as illustrated in the accompanying drawings, in which like references refer to like elements, and wherein:.

The present invention will now be described with reference to the attached Figures. Various structures, systems and devices are schematically depicted in the drawings for purposes of explanation only and so as to not obscure the present disclosure with details, which are well known to those skilled in the art. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the present disclosure. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary or customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein.

In the following, elements with the same reference numeral already described and illustrated with respect to one figure will not necessarily be described in detail again with respect to the other figures, but reference is made to the previous description of the same reference numeral.

<FIG> illustrates a cut view of a sensor device <NUM> according to a first embodiment of the present invention.

As represented on <FIG>, a first PCB <NUM> is connected to a second PCB <NUM> by a flexible electrically conductive means <NUM>. The flexible electrically conductive means <NUM> provides a flexible electrical connection between the first PCB <NUM> and the second PCB <NUM>. The flexible electrically conductive means <NUM> can be a PCB flex or flexible PCB. The flexible electrically conductive means <NUM> is formed of a thin insulating polymer film having conductive circuit patterns affixed thereto. The use of a flexible electrically conductive means <NUM>, like a flexible PCB <NUM>, allows avoiding rigid interconnection between the first PCB <NUM> and the second PCB <NUM>.

Electrical components <NUM> are connected onto each PCB <NUM>, <NUM>.

Terminal pins <NUM> are soldered to the first PCB <NUM>. The terminal pins <NUM> extend from a terminal block <NUM> accommodated in a first assembly <NUM>, like a header assembly <NUM> of the sensor device <NUM>. Sensitive elements (not represented), like temperature sensor or resonator, are connected to the terminal pins <NUM>.

Terminal pins <NUM> are soldered to the second PCB <NUM>. The terminal pins <NUM> are connectors for customer connection.

A connector <NUM>, constituting a second assembly of the sensor device <NUM>, is represented in <FIG>.

The connector <NUM> and the header assembly <NUM> are held together by means of an electrically conductive body <NUM>. In the assembled state of the fluid sensor <NUM>, as represented in <FIG>, the electrically conductive body <NUM> is crimped to a first border <NUM> of the connector <NUM>. The electrical conductive body <NUM> is further attached to the connector <NUM> by means of a form-fit connection between a second border <NUM> of the connector <NUM> and a corresponding step <NUM> of the electrically conductive body <NUM>.

A form-fit connection is also formed between a step <NUM> of the header assembly <NUM> and a border <NUM> of the electrically conductive body <NUM>.

The electrically conductive body <NUM> is thus adapted to accommodate the first PCB <NUM> and the second <NUM>.

In order to electrically ground the PCBs <NUM>, <NUM> for electrostatic discharge (ESD) protection and for preventing electromagnetic interference (EMI noise), it is necessary to create an electrical connection between the PCBs <NUM>, <NUM> and the electrically conductive body <NUM>. The electrical grounding function is carried out by means of an electrically conductive spring <NUM>.

In the first embodiment of the invention, the electrically conductive spring <NUM> is disposed on a plastic holder <NUM>. The plastic holder <NUM> is disposed between the two PCBs <NUM>, <NUM> such that, in the assembled state of the fluid sensor <NUM>, as shown in <FIG>, a first portion <NUM> of the spring <NUM> is pressed against the second PCB <NUM>.

Moreover, a second portion <NUM> of the spring <NUM> is pressed against the electrically conductive body <NUM> so as to maintain an electrical connection between the electrically conductive body <NUM> and the PCBs <NUM>, <NUM>.

The structure of the spring <NUM> is shown in <FIG>. The spring <NUM> for the sensor device <NUM> according to the first embodiment is further described in the following in reference to <FIG>, <FIG>.

The first portion <NUM> of the spring <NUM> is a flat portion 202a in a plan parallel to the surfaces of the PCBs <NUM>, <NUM>. The flat structure 202a of the first portion <NUM> provides a well-adapted contact surface for ensuring the electrical connection when the second PCB <NUM> is pressed against said first portion <NUM>. In a variant, the first portion <NUM> is provided with a bump, the bump being pressed against said first portion <NUM> so as to further improve the electrical contact.

The second portion <NUM> is formed by a bent tab 204a, the apex 204b of which is pressed against the electrically conductive body <NUM> in the assembled state of the sensor device <NUM>. The bent tab 204a extends from the first portion <NUM> in a direction so as to form an angle A from the flat first portion <NUM> (see <FIG>). The bent tab 204a has a free-end 204c.

As illustrated in <FIG>, the angle A between the first portion <NUM> and the second portion <NUM> and the angle B at the apex 204b of the second portion <NUM> are both adapted for allowing the apex 204b to be pressed against the electrically conductive body <NUM> in the assembled stated of the device sensor <NUM> (the assembled state is shown in <FIG>).

The first portion <NUM> and the second portion <NUM>, in particular at the apex 204b, can be covered by an electrically conductive layer to further improve the electrical contact. Such electrically conductive layer can be formed of gold plating over a nickel plating layer.

The spring <NUM> has a flat base portion <NUM> adapted to rest on a corresponding base <NUM> of a receptacle <NUM> of the plastic holder <NUM>.

For improving the retention of the spring <NUM>, a tongue <NUM> (see <FIG>) of the base <NUM> of the spring <NUM> can be bent, i.e. crimped, to the base <NUM> of the plastic holder <NUM>.

The spring <NUM> further comprises a third portion <NUM> extending between the first portion <NUM> and the base <NUM>, so that the third portion <NUM> does not have any free end. The third portion <NUM> of the spring <NUM> is configured to be in a preloaded state between the two PCBs <NUM>, <NUM> (as illustrated in <FIG>). The third portion <NUM> is thus structurally configured for imparting a sufficient spring force along a direction transversal D to the PCBs <NUM>, <NUM> so as to provide strain relief to the PCBs <NUM>, <NUM>. The third portion <NUM> acts as a compression spring exerting its restoring force along the direction D. As shown in <FIG>, the third portion <NUM> is a three-point bent tongue 210a. The shape of the third portion <NUM> advantageously allows increasing the working stroke of the spring <NUM> while having a reduced bulk.

In a variant, the third portion <NUM> acts as a compression spring but has a different structure than the design of the three-point bent tongue 210a of the spring <NUM> shown in <FIG>, <FIG>.

The electrically conductive spring <NUM> allows not only providing a grounding function but, in addition, a stress relief function which improves the retention of the PCBs <NUM>, <NUM>, especially under vibrations, as no stress is caused on and by rigid connections (like solder joints). Hence, the two functions of electrical grounding and strain relief of the PCBs <NUM>, <NUM> are advantageously carried out by means of one single component, the electrically conductive spring <NUM>, that can be assembled to the sensor device <NUM> without the need of soldering step.

As can be seen on <FIG>, in the assembled state of the fluid sensor <NUM>, the plastic holder <NUM> is disposed between the two PCBs <NUM>, <NUM>, such that only the first PCB <NUM> is in direct surface contact with the plastic holder <NUM> and only the second PCB <NUM> is in direct surface contact with the spring first portion <NUM> of the spring <NUM>. This is rendered possible by the specific dimensions of the spring <NUM> and the plastic holder <NUM> as well as by the arrangement of the spring <NUM> with respect to the plastic holder <NUM>. This feature is further described with respect to <FIG>.

<FIG> illustrates a plastic holder <NUM> adapted for receiving three springs <NUM> for a sensor device <NUM> according to the first embodiment. In a variant, the plastic holder <NUM> is adapted for receiving only one spring <NUM>. In another variant, the plastic holder <NUM> is adapted for receiving two, four or more springs <NUM>.

The plastic holder <NUM> comprises a base <NUM>. The base <NUM> can be provided with one or more holes <NUM> to accommodate the electrical component(s) <NUM> connected to the first PCB <NUM>.

The plastic holder <NUM> is one-piece integrally formed, by injection molding for example, thereby being easily manufacturable.

As shown in <FIG>, three receptacles <NUM> extend transversally from the base <NUM>, i.e. along a direction parallel to the Z-direction of the Cartesian coordinates. Each receptacle <NUM> comprises a base <NUM> to support the base <NUM> of the spring <NUM>. Each receptacle <NUM> is formed by two grooves <NUM> facing each other towards the base <NUM>. The grooves <NUM> are positioned on the base <NUM> and spaced from each other such that when a spring <NUM> is received therein, it allows the second portion <NUM> and the third portion <NUM> of the spring <NUM> to protrude outwards from the grooves <NUM> (the protruding aspect is even more visible on the right side of the view of <FIG>). Hence, the grooves <NUM> allows the retention of the spring <NUM> without hindering the contact between the second portion <NUM> and the electrically conductive portion <NUM> in the assembled state of the sensor device <NUM> (as illustrated in <FIG>) nor the strain relief function carried out by the third portion <NUM> of the spring <NUM>.

The total height H between the highest point <NUM> of the groove <NUM> and the base <NUM> of the plastic holder <NUM> is dimensioned so as to be smaller than the distance d1 between the two PCBs <NUM>, <NUM> in the assembled state of the sensor device <NUM> (as illustrated in <FIG>). Hence, a gap of height d2 (see <FIG>) is comprised between the highest point <NUM> of the plastic holder <NUM> and the second PCB <NUM> in the assembled state of the sensor device <NUM>. Hence, as shown in <FIG>, only the first PCB <NUM> is in direct surface contact with the plastic holder <NUM>, which lies on the first PCB <NUM>. The gap d2 between the plastic holder <NUM> and the second PCB <NUM> provides sufficient space for strain relief, i.e. for allowing the third portion <NUM> of the spring <NUM> to exert its restoring force. Consequently, it allows, for example under vibrations, a mutual movement of the PCBs <NUM>, <NUM> that is not affected by any rigid interconnection, in comparison with fluid sensor of the state of start, as illustrated in <FIG> for example.

In order to facilitate the mount of the spring <NUM> to the plastic holder <NUM> and to improve its retention into the receptacle <NUM>, the spring <NUM> further comprises two guiding arms <NUM>.

As shown in <FIG> and <FIG>, the guiding arms <NUM> extend from the first portion <NUM> towards the base <NUM>. The guiding arms <NUM> extend on different sides than the second portion <NUM> and the third portion <NUM>. The guiding arms <NUM> are adapted to be respectively received in the grooves <NUM> of each receptacle <NUM> of the plastic holder <NUM> in order to provide stability to the spring <NUM>. As indicated in <FIG>, the distance d3 between the two free-ends 212a of the guiding arms <NUM> (see <FIG>) is substantially greater than the distance d4 of length of the first portion <NUM> of the spring <NUM> and of the distance d5 between the grooves <NUM> of a same receptacle <NUM>. It allows, when the spring <NUM> is received into the receptacle <NUM> of the plastic holder <NUM>, as shown in <FIG>, to keep the guiding arms <NUM> of the spring <NUM> slightly under stress. It therefore improves the retention of the spring <NUM> within the receptacle <NUM> and its grooves <NUM> because it prevents the spring <NUM> to tip over from the receptacle <NUM> when the apex 204b of the second portion <NUM> is pressed against the electrically conductive body <NUM> (the electrically conductive body <NUM> is shown in <FIG>).

In order to maintain the plastic holder <NUM> to the header assembly <NUM> and the connector <NUM>, snap-fit, press-fit or/and form-fit connections between the plastic holder <NUM> and the header assembly <NUM>, as well as between the plastic holder <NUM> ad the connector <NUM> are performed. Snap-fit, press-fit or/and form-fit connections allow easy assembly steps and do not require the use of any tools. Hence, the manufacturing of the sensor devise <NUM> can be simplified.

As shown in <FIG>, the plastic holder <NUM> comprises two receptacles <NUM> respectively adjacent to receptacles <NUM> already described above. Each receptacle <NUM> comprises a space <NUM> adapted for receiving a locking arm of the connector <NUM> (the locking arm of the connector <NUM> will be described hereafter with respect to the <FIG>). Each receptacle <NUM> also comprises a locking arm <NUM> extending from the base <NUM> and having a free-end <NUM> with a hook shape 320a. The hook shape 320a of the locking arm <NUM> of the plastic holder <NUM> is adapted to perform a snap-fit connection with a corresponding locking arm of the connector <NUM> in the assembled stated of the sensor device <NUM>. It thus allows maintaining the plastic holder <NUM> to the connector <NUM> by a snap fit connection.

As shown in <FIG>, the plastic holder <NUM> is further provided with a recess <NUM> on a circumference <NUM> of the base <NUM>. The recess <NUM> has a shape complementary to a corresponding locking element protruding from the head assembly <NUM> (the locking element protruding from the head assembly <NUM> will be described hereafter with respect to the <FIG>). Hence, a form-fit connection can be carried out between the plastic holder <NUM> and the head assembly <NUM>.

In a variant, the plastic holder <NUM> can be attached to the head assembly <NUM> by means of a snap-fit or a press-fit connection.

A method for assembling the sensor device <NUM> according to the first embodiment is described in the following by means of the <FIG>.

<FIG> illustrates a step of the method for assembling the sensor device <NUM> wherein three distinct springs <NUM> are mounted to the plastic holder <NUM>. Each spring <NUM> is inserted along an insertion direction M1 transversal to the base <NUM> and parallel to the grooves <NUM> (i.e. parallel to the Z direction of the Cartesian coordinate) until the base <NUM> of the spring <NUM> is in contact with the base <NUM> of the receptacle <NUM>. The tongue <NUM> of the spring <NUM> can be crimped to the base <NUM> of the plastic holder <NUM> to improve the retention of the spring <NUM> to the plastic holder <NUM>.

Hence, as shown in the following step represented in <FIG>, each spring <NUM> is received in a respective receptacle <NUM> of the plastic holder <NUM>. The guiding arms <NUM> of each spring are received in the corresponding grooves <NUM> of each receptacle <NUM>. The guiding arms <NUM> have helped guiding the mount of the springs <NUM> to the receptacle <NUM>. As the guiding arms <NUM> of the spring <NUM> are slightly under stress in the receptacle <NUM>, it allows improving the retention of the spring <NUM> to the plastic holder <NUM>.

As shown in <FIG>, the first PBC <NUM> is connected to the header assembly <NUM>. The second PCB <NUM> is connected to the connector <NUM>. <FIG> illustrates a step wherein the header assembly <NUM> and the connector <NUM> of the sensor device <NUM> are positioned with respect to each other so as to align the PCBs <NUM>, <NUM> and the flex PCB <NUM> in a common plan (XY). The pin terminals <NUM> are soldered to the first PCB <NUM> and the pin terminals <NUM> are soldered to the second PCB <NUM>. The numbers of pin terminals <NUM>, <NUM> is not limitative.

The plastic holder <NUM>, comprising the three springs <NUM>, is positioned above the first PCB <NUM> so as to be assembled to the first PCB <NUM> along the insertion direction M <NUM>.

As shown in <FIG>, two locking elements <NUM> protrude from the head assembly <NUM>. The free-end 132a of each locking element <NUM> has a complementary shape of the corresponding recess <NUM> of the plastic holder <NUM>. Hence, a form-fit connection between the plastic holder <NUM> and the locking elements <NUM> of the head assembly <NUM> is possible. The free end 132a of the locking element <NUM> can have a hook shape for providing a snap-fit connection with a corresponding step of the recess <NUM>.

In the following step represented by <FIG>, the plastic holder <NUM> is disposed onto the first PCB <NUM> being connected to the second PCB <NUM> by means of the flexible electrically conductive means <NUM>. The plastic holder <NUM> has been assembled to the first PCB <NUM> along the insertion direction M1 (indicated in <FIG>). Each locking elements <NUM> of the head assembly <NUM> is snap-fitted, form-fitted or press-fitted into the corresponding recess <NUM> of the plastic holder <NUM> thereby ensuring the retention of the plastic holder <NUM> to the head assembly <NUM>.

As shown in <FIG>, two locking arms <NUM> protrude from the connector <NUM>. The free-end 134a of each locking arm <NUM> has a hook shape. Each locking arm <NUM> is adapted to be received in the corresponding receptacle <NUM> of the plastic holder <NUM>. As already described above, each receptacle <NUM> also comprises a locking arm <NUM> extending from the base <NUM> and having a free-end <NUM> with a hook shape 320a. The hook shape 320a of the locking arm <NUM> of the plastic holder <NUM> is adapted to perform a snap-fit connection with the corresponding locking arm <NUM> of the connector <NUM> in the assembled stated of the sensor device <NUM>. It thus allows maintaining the plastic holder <NUM> to the connector <NUM> by a snap fit connection, as shown in <FIG> and described thereafter.

From <FIG>, the connector <NUM> has been pivoted according to the direction M2 (shown in <FIG> by the arrow M2 representing a rotational axis, M2 being transversal to M1) so as to arrange the second PCB <NUM> over the plastic holder <NUM> (see <FIG>). Thereby, the second PCB <NUM> is pressed against the flat first portion <NUM> of each spring <NUM> so as to ensure an electrical contact between the second PCB <NUM> and each spring <NUM>.

Hence, <FIG> represents a step of the assembling method wherein the second PCB <NUM> connected to the connector <NUM>, is moved pivotally onto the plastic holder <NUM> about the rotational axis (M2) transversal to the insertion direction M <NUM> (said direction M <NUM> is represented in <FIG>).

Each locking arm <NUM> of the connector <NUM> is inserted into the space <NUM> of the receptacle <NUM> of the plastic holder <NUM>. The connector <NUM> is snap-fitted to the plastic holder <NUM> by the mutual retention of the hook shape free-ends 134a, 320a of the locking arm <NUM> and the corresponding locking arm <NUM>.

As shown in <FIG> and already described above with respect to <FIG>, a gap of height d2 is provided between the highest point <NUM> of the plastic holder <NUM> and the second PCB <NUM>. Hence, the gap d2 between the plastic holder <NUM> and the second PCB <NUM> provides sufficient space for strain relief, i.e. for allowing the third portion <NUM> of the spring <NUM> to exert its restoring force (the third portion <NUM> is in a preloaded state between the two PCBs <NUM>, <NUM>). Consequently, it allows, for example under vibrations, a mutual movement of the PCBs <NUM>, <NUM> that is not affected by any rigid interconnection, in comparison with fluid sensor of the state of start, as illustrated in <FIG> for example.

As shown in <FIG>, the second portion <NUM> of the spring <NUM> protrudes such that the apex 204b of the bent tab 204a extends beyond, in particular slightly beyond, the surfaces of the PCBs <NUM>, <NUM>. Hence, when the electrically conductive body <NUM> is assembled to the header assembly <NUM> and the connector <NUM>, it will ensure that the protruding apex 204b is pressed against the electrically conductive body <NUM> so as to provide a reliable electrical contact between the spring <NUM> and the electrically conductive body <NUM>.

In a step following the step illustrated by <FIG>, the electrically conductive body <NUM> is assembled to the header assembly <NUM> and the connector <NUM> so as to provide the sensor device <NUM> in its assembled state as represented in <FIG>.

As already described above, in the assembled state of the fluid sensor <NUM> represented in <FIG>, the electrically conductive body <NUM> is crimped to a first border <NUM> of the connector <NUM>. The electrical conductive body <NUM> is further attached to the connector <NUM> by means of a form-fit connection between a second border <NUM> of the connector <NUM> and a corresponding step <NUM> of the electrically conductive body <NUM>.

Hence, the electrically conductive spring <NUM> mounted to the plastic holder <NUM> allows maintaining an electrical connection between the electrically conductive body <NUM> and the PCBs <NUM>, <NUM>, i.e. to perform the grounding function, without the need of being soldered to the PCBs <NUM>, <NUM> or the electrically conductive body <NUM>. Instead, the electrical connection between the electrically conductive spring <NUM> and the PCB is simply achieved by pressing the first portion <NUM> of the spring <NUM> against the second PCB <NUM>. Similarly, the electrical connection between the electrically conductive spring <NUM> and the electrically conductive body <NUM> is simply achieved by pressing the second portion <NUM>, in particular the apex 204b of the bent tab 204a, of the spring <NUM> against the electrically conductive body <NUM>. Consequently, with respect to the known solutions for electrical grounding in sensor device, no soldered joint - and thus no electrical connection - can be damaged by vibrations. The combination of the solder-free solution to assemble the electrically conductive spring <NUM> and the use of the PCB flex <NUM> allows avoiding the drawbacks caused by rigid connections, especially with respect to vibrations. Instead, the present invention provides a sensor device <NUM> without rigid connections between the two PCBs <NUM>, <NUM>. Moreover, as no soldering step is required to install the electrically conductive spring for ensuring the grounding function, the manufacturing is simplified, thereby improving the repeatability and reducing the cost of the assembly process. Consequently, the method for assembling a sensor device is rendered compatible for high volume production. In addition, as no specific soldering step is required for ensuring the grounding function, automation of the assembly process is rendered possible. Moreover, it allows providing a potting free assembly process, which improves further the manufacturability of the sensor device <NUM>.

<FIG> illustrates a schematic view of an electrically conductive spring element <NUM> for a sensor device <NUM> according to the first embodiment. <FIG> illustrates a schematic cut view of the sensor device <NUM> according to the first embodiment of the present invention comprising the spring element <NUM>, as a variant of the spring <NUM>. The <FIG> and <FIG> are described together in the following. Elements with the same reference numeral already described and illustrated in <FIG> will not be described in detail again but reference is made to their description above.

The spring element <NUM> comprises three springs 400a, 400b, 400c extending from a common shielding base <NUM>. In an alternative, the spring element <NUM> comprises a shielding base <NUM> and only one spring 400a. In another variant, the spring element <NUM> comprises a shielding base <NUM> and two, four or more springs 400a, b, c,.

The springs 400a, 400b, 400c are integrally formed with the shielding base <NUM>. Hence, the spring element <NUM> is formed in one-piece.

As the spring <NUM> according to the first variant, each springs 400a, 400b, 400c according to the second variant comprises a first flat portion <NUM> from which extend a second portion <NUM> performing the electrical grounding function and a third portion <NUM> performing the strain relief portion. Each springs 400a, 400b, 400c comprises, as in the first variant, two guiding arms <NUM> extending from the first portion <NUM>.

In comparison with the spring <NUM>, the springs 400a, 400b, 400c according to the second variant share a common base <NUM> that provides a shielding function to the PCBs <NUM>, <NUM>. Therefore, the base <NUM> of the spring element <NUM> is dimensioned so as to cover the base <NUM> of the plastic holder, substantially corresponding to the surfaces of the PCBs <NUM>, <NUM> as shown in <FIG>. Hence, when the shielding base <NUM> lies on the plastic holder <NUM>, it involves that the shielding base <NUM> is disposed between the two PCBs <NUM>, <NUM> (the plastic holder being disposed between the two PCBs), thereby preventing cross talk (i.e. unintentional electromagnetic coupling) between the two PCBs <NUM>, <NUM>.

Therefore, the spring element <NUM> allows not only to perform a grounding function and a strain relief function but also an additional shielding function.

The <FIG> illustrates a cut view of a sensor device <NUM> according to a second embodiment of the present invention.

Similarly than for the sensor device <NUM> according to the first embodiment, the sensor device <NUM> comprises a first PCB <NUM> connected to a second PCB <NUM> by a flexible electrically conductive means <NUM>. The flexible electrically conductive means <NUM> provides a flexible electrical connection between the first PCB <NUM> and the second PCB <NUM>. The flexible electrically conductive means <NUM> can be a PCB flex or flexible PCB <NUM>. The flexible electrically conductive means <NUM> is formed of a thin insulating polymer film having conductive circuit patterns affixed thereto. The use of a flexible electrically conductive means <NUM>, like a PCB flex, allows avoiding rigid interconnection between the first PCB <NUM> and the second PCB <NUM>.

Terminal pins <NUM> are soldered to the first PCB <NUM>. The terminal pins <NUM> extend from a terminal block <NUM> accommodated in a first assembly <NUM>, like a header assembly <NUM>, of the sensor device <NUM>. Sensitive elements (not represented), like temperature sensor or resonator, are connected to the terminal pins <NUM>.

A second assembly <NUM>, like a connector <NUM>, and the header assembly <NUM> are held together by means of an electrically conductive body <NUM>. The electrically conductive body <NUM> is adapted to accommodate the first PCB <NUM> and the second <NUM>.

The electrically conductive body <NUM> is attached to the header assembly <NUM> and to the connector <NUM> in the same way as the electrical conductive body <NUM> already described in reference with <FIG>, to which reference is made.

In order to electrically ground the PCBs <NUM>, <NUM> for electrostatic discharge (ESD) protection and for preventing electromagnetic interference (EMI noise), it is necessary to create an electrical connection between the PCBs and the electrically conductive body <NUM>. The electrical grounding function is carried out by means of an electrically conductive element <NUM>.

The electrically conductive element <NUM> comprises at least two springs 600a, 600b extending from a common shielding base <NUM>. In an alternative, the spring element <NUM> comprises a shielding base <NUM> and only one spring 600a. In another variant, the spring element <NUM> comprises a shielding base <NUM> and three or more springs 600a, b,. The two or more springs 600a, b have the same structure, the description of which therefore applies for each spring.

The springs 600a, 600b are integrally formed with the shielding base <NUM>. Hence, the spring element <NUM> is formed in one-piece.

In a variant, the sensor device <NUM> according to the second embodiment is provided with at least one spring 600a instead of the electrically conductive element <NUM>, i.e. individual springs 600a, 600b that are not integrally formed with a common shielding base <NUM>.

The electrically conductive element <NUM> is disposed between the two PCBs <NUM>, <NUM> such that the shielding base <NUM> rests on the first PCB <NUM>.

As for the first embodiment, a first portion <NUM> of the spring 600a is pressed against the second PCB <NUM>. Moreover, a second portion <NUM> of the spring 600a is pressed against the electrically conductive body <NUM> so as to maintain an electrical connection between the electrically conductive body <NUM> and the PCBs <NUM>, <NUM>.

Unlike the first embodiment, the sensor device <NUM> is not provided with a plastic holder so as to maintain the spring element <NUM>. Instead, the spring element <NUM> is held between the two PCBs <NUM>, <NUM> by a form-fit connection formed between a first portion <NUM> of the spring 600a of the spring element <NUM> and the second PCB <NUM>.

The first portion <NUM> of the spring <NUM> is a flat portion 602a in a plan parallel to the surfaces of the PCBs <NUM>, <NUM>.

According to the second embodiment, the first portion <NUM> comprises a main section 603a terminated with a free-end section 603b, the free-end section 603b extending transversally from the main section 603a through a corresponding through hole <NUM> of the PCB <NUM>. The form-fit connection between the free-end section 603b of the spring 600a and the PCB <NUM> allows maintaining the spring 600a, and thus the spring element <NUM>, without the need of solder joints. The spring element <NUM> can therefore be held in the sensor device <NUM> without soldering.

In a variant, the free-end section 603b can have a shape or a structure so as to provide a snap-fit connection or a press-fit connection with the hole <NUM> of the PCB <NUM>.

The flat structure 602a of the first portion <NUM> provides a well-adapted contact surface for ensuring the electrical connection when the first portion <NUM> is pressed against the second PCB <NUM>. In a variant (not represented), the first portion <NUM> is provided with a bump, the bump being pressed against said first portion <NUM> so as to further improve the electrical contact.

The second portion <NUM> is formed by a bent tab 604a, the apex 604b of which is pressed against the electrically conductive body <NUM> in the assembled state of the sensor device <NUM>. The bent tab 604a extends from the first portion <NUM> in a direction so as to form an angle A from the flat first portion <NUM>. The bent tab 604a has a free-end 604c.

As illustrated in <FIG> for the spring 600a, the angle A between the first portion <NUM> and the second portion <NUM> and the angle B at the apex 604b of the second portion <NUM> are both adapted for allowing the apex 604b to be pressed against the electrically conductive body <NUM> in the assembled stated of the device sensor <NUM>.

The first portion <NUM> and the second portion <NUM>, in particular at the apex 604b, can be covered by an electrically conductive layer to further improve the electrical contact. Such electrically conductive layer can be formed of gold plating over a nickel plating layer.

The spring 600a further comprises a third portion <NUM> extending between the first portion <NUM> and the shielding base <NUM>, so that the third portion <NUM> does not have any free end. The third portion <NUM> of the spring 600a is configured to be in a preloaded state between the two PCBs <NUM>, <NUM>. The third portion <NUM> is thus structurally configured for imparting a sufficient spring force along a direction transversal D to the PCBs <NUM>, <NUM> so as to provide strain relief to the PCBs <NUM>, <NUM>. The third portion <NUM> acts as a compression spring exerting its restoring force along the direction D. As shown in <FIG>, the third portion <NUM> is a three-point bent tongue 610a. The shape of the third portion <NUM> advantageously allows increasing the working stroke of the spring 600a, and thus the spring element <NUM>, while having a reduced bulk.

In a variant, the third portion <NUM> acts as a compression spring but has a different structure than the design of the three-point bent tongue 610a of the spring 600a shown in <FIG>.

The electrically conductive spring element <NUM> allows not only providing a grounding function but, in addition, a stress relief function which improves the retention of the PCBs <NUM>, <NUM>, especially under vibrations, as no stress is caused on and by rigid connections (like solder joints). Hence, the two functions of electrical grounding and strain relief of the PCBs <NUM>, <NUM> are advantageously carried out by means of one single component, the electrically conductive element <NUM>, that can be assembled to the sensor device <NUM> without the need of soldering step.

In order to further improve the retention of the shielding base <NUM> on the sensor device <NUM>, the shielding base <NUM> can comprise a tongue <NUM> that extends transversally from the base <NUM>. The shielding base <NUM> is arranged in the sensor device <NUM> such that the tongue <NUM> abuts on a locking element <NUM> protruding from the head assembly <NUM>. The abutment of the tongue <NUM> against the locking element <NUM> prevents a displacement of the shielding base <NUM> in a plan (XY) parallel to the PCBs <NUM>, <NUM>.

The <FIG> illustrates a cut view of a sensor device <NUM> according to a third embodiment of the present invention.

Similarly than for the sensor devices <NUM> and <NUM> according to the first and second embodiments, the sensor device <NUM> comprises a first PCB <NUM> connected to a second PCB <NUM> by a flexible electrically conductive means <NUM>. The flexible electrically conductive means <NUM> is similar than the flexible electrically conductive means <NUM>, <NUM> already described above.

The use of flexible electrically conductive means <NUM> allows avoiding rigid interconnection between the first PCB <NUM> and the second PCB <NUM>.

Terminal pins (not visible in <FIG>) are soldered to the first PCB <NUM>. These terminal pins extend from a terminal block <NUM> accommodated in a first assembly <NUM>, like a header assembly <NUM>, of the sensor device <NUM>. Sensitive elements (not represented), like temperature sensor or resonator, are connected to the terminal pins <NUM>.

The electrically conductive element <NUM> comprises three springs 800a, 800b, 800c extending from a common shielding base <NUM>. In an alternative, the spring element <NUM> comprises a shielding base <NUM> and only one spring 800a. In another variant, the spring element <NUM> comprises a shielding base <NUM> and two or more springs 800a, b,. The two or more springs 800a, b have the same structure, the description of which therefore applies for each spring.

The springs 800a, 800b, 800c are integrally formed with the shielding base <NUM>. Hence, the spring element <NUM> is formed in one-piece.

In a variant, the sensor device <NUM> according to the third embodiment is provided with at least one spring 800a instead of the electrically conductive element <NUM>, i.e. individual springs 800a, 800b that are not integrally formed with a common shielding base <NUM>.

As for the first and the second embodiments, a first portion <NUM> of the spring 800a is pressed against the second PCB <NUM>. Moreover, a second portion <NUM> of the spring 800a is pressed against the electrically conductive body <NUM> so as to maintain an electrical connection between the electrically conductive body <NUM> and the PCBs <NUM>, <NUM>.

Unlike the first embodiment, the sensor device <NUM> is not provided with a plastic holder so as to maintain the spring element <NUM>. Instead, the spring element <NUM> is held between the two PCBs <NUM>, <NUM> by a press-fit connection formed between a first portion <NUM> of the spring 800a of the spring element <NUM> and the second PCB <NUM>.

The first portion <NUM> of the spring <NUM> is a flat portion 802a in a plan parallel to the surfaces of the PCBs <NUM>, <NUM>.

According to the third embodiment, the first portion <NUM> is provided with a through hole <NUM>. In the variant shown in <FIG>, the through hole <NUM> has a circular cross-section. However, in another variant, the through hole <NUM> has a cross-section with a different shape, like an oblong shape.

An assembly pin <NUM> extends from the second assembly <NUM>, i.e. the connector <NUM> made in plastic material. The assembly pin <NUM> has a substantially cylindrical main body <NUM> on which extends radially at least one longitudinal tongue <NUM>. The cylindrical main body <NUM> assembly pin <NUM> has a similar diameter of the one of the through hole <NUM> of the first portion <NUM>. Hence, when the assembly pin <NUM> is inserted through the PCB <NUM>, via a corresponding through hole <NUM> of the PCB <NUM>, the at least one longitudinal tongue <NUM> is slightly deformed in the through holes <NUM> of the PCB <NUM> and <NUM> of the springs 800a, thereby providing a press-fit connection. This press-fit connection between the first portion <NUM> of the spring 800a and the PCB <NUM> by means of the assembly pin <NUM> of the first assembly <NUM> of the sensor device <NUM> allows maintaining the spring 800a, and thus the spring element <NUM>, without the need of solder joints. The spring element <NUM> can therefore be held in the sensor device <NUM> without soldering.

The flat structure 802a of the first portion <NUM> provides a well-adapted contact surface for ensuring the electrical connection when the first portion <NUM> is pressed against the second PCB <NUM>. In a variant (not represented), the first portion <NUM> is provided with a bump, the bump being pressed against said first portion <NUM> so as to further improve the electrical contact.

As in the first and the second embodiment, the second portion <NUM> of the spring 800a is formed by a bent tab 804a, the apex 804b of which is pressed against the electrically conductive body <NUM> in the assembled state of the sensor device <NUM>. The bent tab 804a extends from the first portion <NUM> in a direction so as to form an angle A from the flat first portion <NUM>. The bent tab 804a has a free-end 804c.

As illustrated in <FIG> for the spring 800a, the angle A between the first portion <NUM> and the second portion <NUM> and the angle B at the apex 804b of the second portion <NUM> are both adapted for allowing the apex 804b to be pressed against the electrically conductive body <NUM> in the assembled stated of the device sensor <NUM>.

The first portion <NUM> and the second portion <NUM>, in particular at the apex 804b, can be covered by an electrically conductive layer to further improve the electrical contact. Such electrically conductive layer can be formed of gold plating over a nickel plating layer.

As in the first and the second embodiment, the spring 800a further comprises a third portion <NUM> extending between the first portion <NUM> and the shielding base <NUM>, so that the third portion <NUM> does not have any free end. The third portion <NUM> of the spring 800a is configured to be in a preloaded state between the two PCBs <NUM>, <NUM>. The third portion <NUM> is thus structurally configured for imparting a sufficient spring force along a direction transversal D to the PCBs <NUM>, <NUM> so as to provide strain relief to the PCBs <NUM>, <NUM>. The third portion <NUM> acts as a compression spring exerting its restoring force along the direction D. As shown in <FIG>, the third portion <NUM> is a three-point bent tongue 810a. The shape of the third portion <NUM> advantageously allows increasing the working stroke of the spring 800a, and thus the spring element <NUM>, while having a reduced bulk.

In a variant, the third portion <NUM> acts as a compression spring but has a different structure than the design of the three-point bent tongue 810a of the spring 800a shown in <FIG>.

The electrically conductive spring element <NUM> allows not only providing a grounding function but, in addition, a stress relief function which improves the retention of the PCBs <NUM>, <NUM>, especially under vibrations, as no stress is caused on and by rigid connections (like solder joints). Hence, the two functions of electrical grounding and strain relief of the PCBs <NUM>, <NUM> are advantageously carried out by means of one single component, the electrically conductive element <NUM>,that can be assembled to the sensor device <NUM> without the need of soldering step.

In comparison to the first embodiment, the sensor devices <NUM>, <NUM> of the second and third embodiments are not provided with a plastic holder <NUM> for carrying the springs/spring element. Instead, the spring elements <NUM>, <NUM> of the second and third embodiment are in direct surface contact with both PCBs <NUM>, <NUM>, <NUM>, <NUM>: the base <NUM>, <NUM> is in direct contact with the first PCB <NUM>, <NUM> and the first portion <NUM>, <NUM> is in direct surface contact with the second PCB <NUM>, <NUM>. While the sensors <NUM>, <NUM> of the second and third embodiment do not require an additional element, such as a plastic holder, they need the second PCB <NUM>, <NUM> to be provided with a through hole <NUM>, <NUM> so as to form a press-fit, snap-fit or form-fit connection with the first portion of the spring element <NUM>, <NUM>.

The presence of a through hole in the PCB for maintaining the springs/spring element according to the first embodiment is not required thanks to the use of the plastic holder <NUM>.

In a variant (not illustrated), the sensor devices <NUM>, <NUM>, <NUM> can comprise more than two PCBs, for example stacked over each other and with spring(s) or spring element arranged therebetween.

All of the first, second and third embodiments, provide a sensor device <NUM>, <NUM>, <NUM> wherein the electrically conductive spring/spring element performing both the grounding function and the strain relief function, is held by a snap-fit, a form-fit or a press-fit connection, i.e. without the need of soldering the electrically conductive spring/spring element.

As no soldering step is required to install the electrically conductive spring for ensuring the grounding function, the manufacturing is simplified, thereby improving the repeatability and reducing the cost of the assembly process. Consequently, the sensor device is rendered compatible for high volume production.

Claim 1:
Sensor device comprising an electrically conductive body (<NUM>, <NUM>, <NUM>) adapted to accommodate at least a first printed circuit board (PCB) and a second PCB,
the sensor device being characterized in that
the first PCB (<NUM>, <NUM>, <NUM>) and the second PCB (<NUM>, <NUM>, <NUM>) are connected together by a flexible electrically conductive means (<NUM>, <NUM>, <NUM>) and
the sensor device further comprises at least one electrically conductive spring (<NUM>, <NUM>, <NUM>, 600a, <NUM>, 800a) held between the two PCBs by a snap-fit, a form-fit or a press-fit connection
such that a first portion (<NUM>, <NUM>, <NUM>) of the spring is pressed against one of the PCBs (<NUM>, <NUM>, <NUM>) and
a second portion (<NUM>, <NUM>, <NUM>) of the spring is pressed against the electrically conductive body (<NUM>, <NUM>, <NUM>) to maintain an electrical connection between the electrically conductive body and the PCBs.