PLANAR ELECTRIC BOARD WITH PLIABLE WINGS AND SYSTEM FOR SENSING COMPONENTS ALONG THREE COORDINATE AXIS OF INNER FORCES IN A BLOCK MADE OF A BUILDING MATERIAL TECHNICAL FIELD

This invention relates to monitoring devices in building structures and more particularly to a planar electric board with foldable wings adapted to the realization of a system for sensing the components along three coordinate axis of internal pressures in a block made of building material.

BACKGROUND

The strategy for implementing damage detection and the characterization of mechanical structures is commonly called Structural Health Monitoring (SHM). Damages are defined as modifications of the material and/or of the geometrical properties of a structural system, comprising modifications of boundary conditions and connections of the system, that worsen performances of the system. The SHM process implies the observation of the mechanical system during the time using periodically:

- measurements of dynamical responses coming from an array of sensors,

- extraction of data of damage characteristics sensed from these measurements, - statistical analysis of these data of characteristics for determining the present health state of the system (also called structural analysis).

This process provides information about the capacity of the structure of carrying out its function, considering the unavoidable aging and degradation in working environments. After extreme events, such as earthquakes or explosions, the SHM is used for a quick screening of the conditions of the structure for providing, almost in real time, reliable information about the integrity of the structure itself.

Nowadays, SHM systems use sensors placed on the surfaces to be controlled. For example, sensors used (anemometers for calculating the wind speed, accelerometers, extensometers, motion transducers, temperature sensors, sensors for detecting motion of weights, etc.) for monitoring bridges are placed on the external surfaces of beams, wire ropes or pillars, in order to: - estimate the effects of loads on the bridge,

- evaluate the weakening of the bridge,

- foresee the probable evolution of the bridge and its expected lifetime.

SHM systems with sensors adapted to be buried in building structures to be monitored have been devised. These sensing devices include sensors (of pressure, humidity, temperature, etc.) that have at least a remote powering and transmission antenna for transmitting the measured values outside of the block of building material, as in RFID devices (that are sensorless) illustrated in the article by A. Finocchiaro, G. Ferla, G. Girlando, F. Carrara e G. Palmisano, "A 900-MHz RFID System with TAG- Antenna Magnetically-Coupled to the Die", 2008 IEEE Radio Frequency Integrated Circuits Symposium, pages 281-284. This kind of sensing devices are disclosed for example in the US patent application No. 2009/0033467 and in the PCT WO 2012/084295, herein incorporated by reference, and are depicted in figures 1, 2, 3 and 4.

As shown in figure 3, the sensor 10 is integrated in a chip IC 1 made of a semiconductor material, is supplied and communicates in a contactless fashion because it is electromagnetically coupled (for example inductively, or capacitively or through antenna) with an electric communication line with the outside, as shown in figures 1 and 2. With this technique, sensors buried in the building material may be supplied from the outside and remain galvanically isolated from the respective communication lines with the outside.

Sensing device having sensors electromagnetically coupled to respective communication lines 2, eventually ending with an antenna 22 and equipped with elements of electromagnetic expansion, are shown in figures 3 and 4. Their structure and how they are used is described in detail in the PCT application WO 2012/084295. They may be tied to a support 211 buried in a block of building material for sensing at least a characteristic of the building material along the whole block or at least in a portion thereof.

In great building structures, such as for example in pillars of bridges, it is important to sense the distribution of forces in the structure. To this end, the devices disclosed in the documents US 2009/0033467 and/or WO 2012/084295 are buried inside the structure such to remain oriented along three coordinate reference axis, for measuring the three orthogonal components (or in any case according to three different axis) of the forces in the structure.

These pressure sensors are typically constituted by an integrated semiconductor circuit with a sensing surface, eventually passivated such to be adapted to be placed in direct contact with the building material, that senses a pressure value in a direction orthogonally thereto.

SUMMARY

Tests executed by the applicant showed that during pouring and/or the consequent solidification phase of the building material, it is difficult to keep the desired mutual orientation of the cited sensing devices. This may cause relevant errors in the determination of the distribution of components of the inner forces in a block of building material.

Installing sensing devices of the type disclosed in the cited prior documents on pre-formed rigid three-dimensional structures, that establish the mutual orientation of the devices, would make complex and economically less convenient the mutual positioning of the devices.

In order to obviate to these drawbacks, it has been devised a planar electric board with foldable wings along folding lines defined on a base surface such to define oriented planes, having an auxiliary circuit comprising pairs of capacitive coupling plates, destined to be electromagnetically coupled to corresponding antennas for contactless power supplying and for transceiving data of sensing devices, and at least two common communication lines to which the corresponding capacitive coupling plates are connected.

This electric board may be used for realizing sensing systems of the inner pressure in a block of building material, and more generally for realizing sensing systems of components along three coordinate axis of any physical vector amount, by bonding, on the foldable wings and on the base surface, sensing devices having directional sensors of this physical amount.

According to an embodiment, the planar electric board comprises a planar support made of material that may be hot and/or cold foldable, wherein the auxiliary circuit is placed on this support. This support may be for example in the form of an engraved ribbon of Teflon or of any other thermoplastic material with a plurality of wings, adapted to be hot and/or cold folded such to assume a desired orientation.

According to an embodiment, the auxiliary circuit is realized in/on a layer of flexible material that is laminated over the plane support.

Sensing devices adapted to be bonded on the electric board of this disclosure for building sensing systems according to the present disclosure, are galvanically isolated and supplied through antennas for contactless power supplying, such as for example the devices disclosed in the documents US 2009/0033467 and/or WO 2012/084295.

According to an embodiment, a sensing system of internal pressures along three coordinate axis of a block of building material, comprises an electric board of this disclosure and sensing devices having galvanically isolated pressure sensors, each having a passivated sensing surface adapted to be placed in contact with a building material.

It is further disclosed a block of building material comprising a sensing system of internal pressures buried therein in which the building material is in direct contact with the sensitive passivated surfaces of the pressure sensors.

The claims are integral part of this specification and are herein incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1 and 2 show known sensing devices, disclosed in the US patent publication No. 2009/0033467, including circuits adapted to transmit in contactless fashion the electromagnetic energy required for powering a buried sensor.

Figures 3 and 4 show known sensing devices, disclosed in the document WO

2012/084295, including circuits adapted to transmit in contactless fashion electromagnetic energy and information.

Figure 5 shows an example of sensing system according to this disclosure having a support in the form of ribbon with folded wings, on which sensing devices that include pressure sensors are fixed.

Figure 6 is a detailed view of an electric board according to the present disclosure with sensing devices bonded on respective wings of a support and coupled in a contactless manner with electric communication lines.

Figure 7a is an embodiment of the electric board of figure 6 with a transceiving and contactless power supplying antenna connected to the electric communication lines.

Figure 7b is an embodiment of the electric board of figure 6 wherein the electric communication lines are connected to the outside through a cable and through related connection terminals.

Figures 8a and 8b are plant views of embodiments of the support according to this disclosure with wings not yet folded and spaces destined to house sensing devices.

Figure 9 illustrates an embodiment of a sensing device having a pressure sensor and a respective antenna for contactless power supplying and for transceiving data.

Figure 10 is a cross sectional of the sensing device of figure 9 and of an embodiment of a package substrate embedding an antenna electromagnetically coupled to the antenna of the sensing device, and metallization for realizing a capacitive coupling with electric communication lines on the support according to the present disclosure.

Figures 11A and 11B are plant views of embodiments of the package substrate shown in figure 10.

Figure 12 is a cross section of the sensing device and of the relative substrate of figure 10, and of the support on which the electric communication lines are defined.

Figure 13 illustrates the sensing device of figure 10 with the relative substrate fixed to a layer of fiexible material with electromagnetic expansion antennas and with capacitive coupling plates.

Figure 14 is a top view of a layer of flexible material with capacitive coupling plates of a support according to an embodiment of this disclosure.

Figure 15 shows capacitive coupling plates of the layer of fiexible material of figure 14 connected among them.

Figure 17 is a top view of a layer of flexible material with capacitive coupling plates of a support according to an embodiment of this disclosure.

Figure 18 shows capacitive coupling plates connected among them through electric communication lines of the layer of flexible material of figure 17. Figure 19 is a detailed view of a structure according to the present disclosure and shows a substrate of a sensing device in which there are auxiliary metals that constitute an auxiliary capacitance in series to the electromagnetic expansion antennas.

Figure 20 is a plant view of an embodiment of the package substrate with auxiliary metals constituting the auxiliary capacitance depicted in figure 19.

Figure 21 illustrates schematically how to perform a contactless test and a trimming of the structure according to the present disclosure.

Figures 22 and 23 illustrate schematically how to trim the auxiliary metallization of figure 20.

Figure 24 illustrates schematically how to perform a contactless test and a trimming of a sensing device mounted on the respective substrate.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

An embodiment of the sensing system of pressure components in a block of building material along three coordinate axis is shown in figure 5. It comprises a support 1 that defines a base surface 2 and wings 3 confining with the base surface 2 along folding lines 4. On the base surface 2 and on the wings 3 there are sensing devices 5, each containing an integrated circuit IC for example of the type disclosed in the cited document WO 2012/084295, having respective pressure sensors 6 equipped with a planar sensing surface substantially coplanar with the plane defined by the wing 3 or coplanar with the base surface 2 on which they are installed.

The sensing devices 5 are powered and transmit/receive data through contactless electromagnetic coupling with electric communication lines 14, shown in figure 6, according to the disclosure of the documents US 2009/0033467 and/or WO 2012/084295 and schematically sketched in figures from 1 to 4.

This kind of contactless power supplying and transceiving is particularly convenient because the sensing devices 5 and the integrated circuits IC contained in the sensing devices 5 are galvanically isolated from the electric communication lines 14, and this increases their reliability and thus the reliability of the whole system. Moreover, the sensing devices 5 may be fixed, for example by bonding, after heaving realized the electric board composed of the support 1 and of the auxiliary circuit constituted by the electric communication lines 14 and by the capacitive coupling plates destined to be electromagnetically coupled with respective plates of the sensing devices 5.

Once the sensing devices 5 are mounted, the wings 3 are folded, eventually hot folded if the material used for the support 1 does not allow a cold folding, up to assuming the desired orientation.

The sensing system according to this disclosure is fabricated by realizing an electric board by forming the plane support 1 such to make it have at least a base surface 2 and at least two foldable wings 3 along folding lines 4, thus realizing the auxiliary circuit with the electric communication lines 14 and the electromagnetic expansion antennas thereon, then the sensing devices 5 are fixed on the electric board such to be galvanically isolated from the electric communication lines 14 and to be electromagnetically coupled with them for transmitting/receiving data and to be powered in a contactless fashion, and finally the wings 3 are folded along folding lines.

The planar support 1, having at least a base surface 2 and at least two foldable wings 3, the auxiliary circuit containing the electric communication lines 14 and the capacitive coupling plates 10, in which spaces on which the galvanically isolated sensing devices that will be electromagnetically coupled in a contactless fashion to the electric communication lines 14, constitutes a planar electric board with foldable wings that may be realized separately from the sensing devices. This electric board may also be used in sectors different from the monitoring of structures of building material, for supplying and keeping oriented directional sensors of any type. More generally, it could be used for realizing sensing systems of the components along three coordinate axis of any physical vector amount, obtained by bonding on the electric board sensing devices having directional sensors of this physical amount.

For example, with a planar electric board according to the present disclosure, it is possible to realize sensing systems of the direction of electromagnetic waves by bonding on its base surface 2 and on its wings 3 sensing devices, embedding directional sensors of electromagnetic waves, galvanically isolated and electromagnetically coupled with the electric connection lines 14, thus folding the wings 3 such to orient the directional sensors of electromagnetic waves according to orthogonal planes in respect to a triplet of coordinate axis. The sensing devices 5 will be powered in a contactless fashion by electromagnetic coupling to the electric communication lines 14, for example according to the techniques disclosed in the documents US 2009/0033467 and/or WO 2012/084295, and the signals generated by the sensors will be transmitted on the electric communication lines 14.

An advantage of the planar electric board with foldable wings of this disclosure, consists in that it may be fabricated at a relatively small cost. Indeed, it is possible to realize on the support 1, the electric connection lines 14 and the electromagnetic expansion antennas for forming the circuits shown in figures 6 and 7a through planar processes. For example, these circuits may be realized directly on the support 1 with the technology used for fabricating PCB (Printed Circuit Board), or by electro-plating or ink-jet, or also by laminating on the support 1 with a process Roll-to-Roll (R2R) a layer 13 on which or in which the electric connection lines 14 are defined and the electromagnetic expansion antennas 19, of the type illustrated in the documents US 2009/0033467 and/or WO 2012/084295, destined to be electromagnetically coupled to respective antennas for contactless power supplying 8 of the sensing devices 5.

By connecting to a common electric line all the capacitive coupling plates 10 of the support, sketched in figures 6, 7a and 7b as plates 10 of capacitors placed in front of respective capacitive coupling plates 9 embedded in the package of the sensing device 5, it is possible to irradiate simultaneously a variable electromagnetic field on all the antennas 7 for contactless power supplying the integrated circuits IC embedding the sensors 6 through the antennas 8 embedded in the package.

As shown in figures 7a and 7b, the electric communication lines 14 will transmit the signals coming from the sensors through a single antenna 19 embedded in the auxiliary circuit or through connection terminals CONNECTOR of electric connections 20.

In the embodiment of figure 5, the support 1 is substantially a ribbon with numerous wings 3 folded perpendicularly thereto. This support may be obtained by realizing the planar ribbon depicted in figure 8a, engraved such to define the wings 3 foldable along folding lines 4, in any case the particular embodiment of the support 1 is non limiting. In the embodiment shown in figure 8a, particularly useful for realizing sensing systems of internal forces of a block made of building material, the support 1 is provided with holes 16 realized on the wings 3 and on the base surface 2 in correspondence of the places in which the sensing devices 5 will be fixed. The function of these holes 16 is to allow the building material to come into direct contact, when poured, with the sensitive surface of the sensor 6 embedded in the sensing device 5. In this particular application, sensing devices 5 embedding the integrated circuits IC disclosed in the document WO 2012/084295, that include passivated sensitive surfaces that may be placed in contact with the building material, will be conveniently used.

From the above considerations, it is clear that the support 1 of the novel electric board with foldable wings of this disclosure may also have no hole 16. In the above cited example of the sensing system of the direction of arrival of electromagnetic waves, these holes 16 may be omitted and the wings 3 and the base surfaces 2 may be solid.

Even in the case of pressure sensors 6, it is possible to omit these holes 16, in order to reduce the pressure measured by the sensor itself and to increase, in this way, the greatest pressure value that the sensor may sense.

According to another embodiment depicted in figure 8b, the support 1 is composed of only two rectangular wings 3 confining with the rectangular base surface 2 along consecutive sides thereof. This embodiment may be embedded in blocks of building materials having relatively reduced sizes.

The support 1 may be made of a material resistant at environment temperature and easily hot workable such as Teflon, or a thermoplastic material, or LCP (Liquid-crystal polymers), or polyimide or yet FR4, ROGER, BT.

For sake of ease, hereinafter reference will be made to the case shown in figure 8a in which the planar electric board of this disclosure is destined to the realization of systems for sensing internal forces in a block of building material. It is clear that what will be stated holds, mutatis mutandis, also when the electric board does not have holes 16 because it is destined to other objectives, such as for example for realizing systems for sensing the direction of arrival of electromagnetic waves.

Embodiments of integrated circuits IC of the sensing devices 5 adapted to be fixed to the electric board of this disclosure for realizing the cited sensing systems to be buried in blocks of building material for monitoring building structures of great size, are shown for example in the documents US 2009/0033467 and/or WO 2012/084295.

More generally, these integrated circuits IC and the relative sensing devices 5 that embed them, that are galvanically isolated, will be of the type shown in figures 9 and 10, respectively. They have a sensor 6, that may be a pressure sensor 6, and an antenna 7 for contactless power supplying the sensor 6 realized on a substrate 11, for example of a semiconducting material. As shown in figure 9, conveniently the antenna 7 will be coupled to an electromagnetic expansion antenna 8, electrically connected to other capacitive coupling plates 9, embedded in the package of the sensing device, and destined to be electromagnetically coupled to respective capacitive coupling plates 10 defined in the auxiliary circuit, shown in figures 6, 7A and 7B, of the planar electric board of this disclosure. With this capacitive coupling between the plates 9 and 10, it is possible to prevent soldering that may be damaged when subjected to the high pressures that typically are generated in a block of building material, and as a consequence this may lead to a misfunctioning of at least a sensing device 5.

Exemplary patterns of capacitive coupling plates 9 embedded in the package of a sensing device 5 usable in the sensing system of this disclosure, are shown in figures 11A and 11B. Preferably, the plates 9 are defined according to geometries adapted to minimize losses for eddy currents. In the shown embodiments, the sensitive surface of sensor 6 is not covered by the package such to allow the building material to pour through the package and be in direct contact with the sensor.

Figure 12 is a sectional view of a portion of the planar electric board of this disclosure and of the sensing device of figure 10. It shown the support 1 with the hole 16, in order to make a building material (for example concrete) come into contact with the sensitive surface of the sensor 6, and the layer 13 on which there is the auxiliary circuit. In the embodiment of figure 12 only the capacitive coupling plates 10 of the auxiliary circuit are shown, electromagnetically coupled to the respective plates 9 of the sensing device 5, that remains galvanically isolated from the planar electric board.

The sensing device 5 will be fixed to the layer of flexible material 13 by bonding or through a layer of silicon oxide or of dielectric 17, as shown in figure 13.

As stated above making reference to figure 6, the auxiliary circuit will be defined on a layer 13, that may be of flexible material laminated onto the support 1, embedding capacitive coupling plates 10 connected to a common electric line 14. These plates 10 may be realized for example as shown in figures 14 and 16, connected to respective electric connection lines 14 to which all plates 10 are connected in parallel, and as a consequence the system is fault tolerant, meaning that if at least a sensing device 5 is damaged, the other sensing devices will continue to function normally.

Preferably, the plates 10 in the layer 13 will have a shape corresponding to that of plates 10 embedded in the package of the sensing device, such to obtain a good electromagnetic coupling.

The capacitive coupling plates 9 and 10 may have a different shape, as shown in figures 16, 17 and 18, that are similar to figures 11 A, 14 and 15. It is to be noticed that the package of figure 16, differently from that of figures 11A and 11B, does not have any hole for exposing the sensor of the sensing device, that remains covered. Similarly, the layer 13 shown in figures 17 and 18 of the planar electric board has no hole.

In order to regulate the resonance frequency of the connection between the electromagnetic expansion antenna 8 and the capacitive coupling plate 9 embedded in the package of the sensing devices 5, it is possible to interpose therebetween a capacitance 15, shown in figures 19 and 20, for example by defining a metal 15 with interdigitated portions separated by a dielectric.

After having fixed the sensing devices 5 on the electric board and before having folded the wings 3, the sensing system of this disclosure is still substantially planar, thus it may be easily fully or partially tested with a contactless technique using an ATE (Automatic Test Equipment), as shown in figure 21, to which an antenna may be connected that may be of Hertzian type, or of magnetic or capacitive type. Before folding the wings, the sensing system is planar thus, if the used sensing devices 5 are the ones disclosed referring to figures 19 and 20, using a laser (figures 22 and 23) it is possible to carry out a trimming or fine tuning of the resonance frequencies of at least a part of the system, for example by acting on capacitors 15 by properly modifying the corresponding metallization embedded in the package of the sensing device 5. This operation may be executed by acting from the side of the sensing device (figure 22) or from the side of the support 1 (figure 23). In the latter case, the support 1 and the eventual layer 13 that embeds the auxiliary circuit, will have holes 18 such to expose the metallization 15 also after the sensing device 5 has been fixed to the electric board.

As an alternative, as shown in figure 24, it is even possible to test only the sensing devices through an ATE capacitively coupled therewith, and to carry out the above mentioned trimming of the metallization 15 before mounting the devices on the electric board.