JP7383312B2 - wireless sensor - Google Patents

Description

The present invention relates to a wireless sensor that transmits and receives data wirelessly, which can be downsized, highly reliable, and save power.

In recent years, the scale of the sensor market has expanded rapidly due to the increasing momentum of IoT, and various sensors such as temperature, humidity, pressure, vibration, acceleration, sound, light, flow velocity, speed, distance measurement, GPS, etc. are used. There is an increasing need to analyze and utilize data.
Furthermore, its use is expected to increase rapidly in the future for applications such as safety confirmation and automation.

A typical sensor device is equipped with a sensor that acquires target data, a microcomputer or dedicated controller that performs processing such as acquiring, digitizing, and calculating data from the sensor, and also performs wireless data communication. There are also products that are equipped with transmitter/receiver ICs for this purpose.
However, sensor devices equipped with these various components tend to be large in size, and the higher the functionality, the more difficult it is to reduce the size and weight, and the mounting locations are limited.

Furthermore, a sensor device equipped with a wireless communication function requires an antenna for wireless communication, and in order to ensure a communication distance, it is necessary to increase the size of the antenna. Therefore, the balance with communication performance makes miniaturization even more difficult.

Existing sensor devices often have multiple parts of various types mounted on the surface, and exposed parts are susceptible to reliability degradation due to external factors such as humidity and dust, making them unsuitable for applications that require environmental resistance. Difficult to use. In order to improve environmental resistance, it is possible to enclose the product in a sturdy case, but this has the contradictory problem of increasing the product size.

In order to support IoT, it is preferable that sensor devices can be installed anywhere, even when sensors are later added to aging equipment to bring its performance closer to that of the latest equipment. Many of the manufacturing facilities in Japan are aging and not the latest models, so in order to implement IoT, it is necessary to be able to easily install various sensors, and sensors will continue to become smaller and smaller in the future. It is thought that the demand for higher reliability and lower power consumption will increase.

As a measure to improve the above-mentioned problem, a sensor module is known in which an analog circuit and a digital circuit are arranged on the front and back sides of a multilayer board and the components are mounted to achieve miniaturization (for example, Patent Document 1). Further, an RFID sensor tag with a self-power generation function is known that uses RFID technology to record sensor data using vibration self-generated power (for example, Patent Document 2).
Furthermore, a wireless sensor unit is known in which deterioration in communication performance is suppressed by creating a hollow structure between component mounting boards (for example, Patent Document 3).

Japanese Patent Application Publication No. 2013-19826 Japanese Patent Application Publication No. 2006-52742 JP2021-106331A

However, in the technique of Patent Document 1, the mounting board has a hollow structure, so there is a possibility that impact resistance cannot be ensured, and there is also a possibility that the bonded case cannot be maintained for a long period of time in a harsh environment. Furthermore, since the structure is not completely sealed, there are reliability issues, such as if there are defects such as holes in the lid material, reliability may be lowered due to moisture or dust infiltration.

In addition, with the technology of Patent Document 2, the communication distance of the RFID tag is short due to miniaturization, so reader/writer equipment must be placed close to read sensor data, making it unsuitable for management over a wide area. There are challenges.

In addition, in the technology of Patent Document 3, in order to suppress the deterioration of communication performance, components such as sensors and power supply components are placed three-dimensionally apart from each other by creating a hollow structure, which makes the product smaller. The problem is that it is becoming difficult to adapt. Additionally, since it does not have a sealed structure, there is a concern that reliability may deteriorate due to moisture or dust infiltration.

That is, the present invention was made to solve the above problems, and aims to provide a wireless sensor that is small in size, has high wireless communication performance, and has high reliability.

According to the wireless sensor according to the present invention, the wireless sensor is attached to an object to be measured and used, and the elements used for sensing operation are three-dimensionally arranged within a multilayer printed wiring board. are integrally sealed with resin, and antenna circuits used for external transmission and reception of sensor data are electrically connected to each other on the surface layers of both sides of the multilayer printed wiring board. The feature is that it can be installed .
By adopting this configuration, it is possible to achieve miniaturization by arranging the elements three-dimensionally within the multilayer printed wiring board, and by integrally sealing the multilayer printed wiring board with resin, it becomes a sealed structure. It can prevent moisture and dust from entering and improve reliability. Furthermore, by forming the antenna circuit on the surface layer of both sides of the resin-sealed multilayer printed wiring board, it is possible to secure the antenna area without being affected by the element and circuit size required for sensing, and improve communication performance. be able to demonstrate fully.

The invention also includes a sensor unit that acquires the state of the object to be measured, a transmitter/receiver unit that externally communicates data obtained by the sensor unit, and a power supply unit that supplies power to at least the sensor unit and the transmitter/receiver unit. may be a feature.

Moreover, it may be characterized by comprising a control section that executes calculations and digitization of data obtained by the sensor section, and overall operation management.

Further, the transmitting/receiving section may be arranged in the outermost layer inside the resin-sealed multilayer printed wiring board, and the transmitting/receiving section and the antenna may be connected at the shortest distance.
According to this configuration, the wiring length can be minimized and deterioration in communication performance due to impedance can be suppressed.

Further, the antenna circuits formed on both sides of the multilayer printed wiring board may be electrically connected to each other by a structure formed in the manufacturing process of the multilayer printed wiring board.
According to this configuration, by incorporating the components, there are no mounted components or connection wiring on the front and back surfaces, so the front and back surfaces can be effectively used as antenna circuits, so that sufficient communication performance can be ensured. Furthermore, the configuration formed in the manufacturing process of the multilayer printed wiring board refers to configurations such as through holes, build-up connections using laser vias, and end surface electrodes.

According to the wireless sensor according to the present invention, the wireless sensor includes a sensor section that is attached to a measurement target object and acquires the state of the measurement target object, and a main body section that is communicably connected to the sensor section through external wiring. Elements used for sensing operations other than the section are three-dimensionally arranged within the multilayer printed wiring board, and the multilayer printed wiring board is integrally sealed with resin, and the antenna circuit used for external transmission and reception of sensor data is arranged three-dimensionally within the multilayer printed wiring board. , is characterized in that both surface layers of a multilayer printed wiring board are electrically connected to each other and attached to a metal body as the object to be measured .
By adopting this configuration, it is possible to achieve miniaturization by arranging the elements three-dimensionally within the multilayer printed wiring board, and by integrally sealing the multilayer printed wiring board with resin, it becomes a sealed structure. It can prevent moisture and dust from entering and improve reliability. Furthermore, by forming the antenna circuit on the surface layer of one and/or both sides of the resin-sealed multilayer printed wiring board, the antenna area can be secured without being affected by the size of the elements and circuits required for sensing. Communication performance can be fully demonstrated.
In addition, by providing the sensor unit outside the main body of the wireless sensor, the sensor unit can be installed even in places where it is difficult to install the wireless sensor, such as in a small gap where the installation space is small or due to high temperatures. be able to. Furthermore, since the sensor unit can be brought into direct contact with the object to be measured, sensing errors can be minimized.

According to the present invention, it is possible to provide a wireless sensor that is small but has high wireless communication performance and high reliability.

FIG. 2 is a block diagram showing the internal configuration of a wireless sensor. FIG. 1 is a cross-sectional view showing a first embodiment of a wireless sensor. FIG. 3 is a cross-sectional view showing a second embodiment of a wireless sensor. FIG. 2 is a schematic explanatory diagram showing an embodiment in which a sensor section is placed outside. FIG. 2 is a schematic explanatory diagram showing a state in which a wireless sensor is attached to an object to be measured using an adhesive tape.

(overall structure)
The wireless sensor in this embodiment will be described below based on the drawings.
Note that the wireless sensor of the present invention is not limited to the embodiments described below.

Figure 1 shows a block diagram of the internal configuration of the wireless sensor.
The wireless sensor 10 wirelessly transmits sensor data obtained by measuring objects to be measured in various environments.
The wireless sensor 10 includes a sensor section 50 that acquires the state of the object to be measured, a control section 51 that calculates, records, and digitizes sensor data obtained by the sensor section 50, and manages operations, and a control section 51 that performs operation management. The transmitting/receiving section 52 externally communicates with the transmitting/receiving section 52, an antenna circuit 54 connected to the transmitting/receiving section 52, and a power supply section 53 supplying operating power to the sensor section 50, the control section 51, and the transmitting/receiving section 52.
However, the configuration may be such that the wireless sensor 10 is not provided with the control unit 51. In this case, a memory for storing sensor data may be provided.
Alternatively, the wireless sensor 10 may have a configuration in which the sensor section 50 is not provided. In this case, the wireless sensor 10 and the sensor unit 50 are connected by external wiring.

FIG. 2 shows a cross-sectional view of the wireless sensor of this embodiment.
As shown in FIG. 2, the wireless sensor 10 includes a plurality of elements involved in the sensing operation (elements that specifically implement the functions of the sensor unit 50, control unit 51, transmitting/receiving unit 52, and power supply unit 53 shown in FIG. 1): Hereinafter, the description of the elements will be omitted) and wiring for electrically connecting the elements 50, 51, 52, and 53 are three-dimensionally built into the multilayer printed wiring board 11. Therefore, the size of the wireless sensor 10 can be reduced compared to the case of conventional surface mounting.

In the wireless sensor 10, an antenna circuit 54 is formed on the surface layer of a multilayer printed wiring board 11. The multilayer printed wiring board 11 includes a plurality of elements 50, 51, 52, and 53 involved in sensing operation, and wiring for electrically connecting each of the elements 50, 51, 52, and 53, and the surface layer includes these elements 50, 51, 52, and 53. , 51, 52, 53 and wiring are not arranged, a sufficient antenna area can be secured on the surface layer for forming the antenna circuit 54, and communication performance can be fully demonstrated.
Furthermore, if the wireless sensor 10 is downsized, the size of the antenna circuit 54 is also downsized at the same time. Since it becomes easier to secure the area of 54, deterioration in communication performance due to miniaturization can be suppressed.

Further, a transmitting/receiving section 52 is built in directly below the antenna circuit 54. That is, the antenna circuit 54 is formed on the front side of the outermost surface layer 11a constituting the multilayer printed wiring board 11, and the metal layer 12 such as copper foil is formed on the back side of the outermost surface layer 11a. A transmitting/receiving section 52 is arranged. Further, the metal layer 12 and the antenna circuit 54 are electrically connected by a via 14 penetrating the outermost layer 11a.
By arranging the antenna circuit 54 on the front surface of one board layer and the transmitting/receiving section 52 on the back surface, the wiring length is only the thickness of one board layer, so the wiring length can be minimized. This makes it possible to minimize the deterioration in communication performance due to impedance.
In this case, the metal layer 12 and the transmitting/receiving section 52 may be connected by bonding or may be mounted by flip chip mounting. In the case of flip-chip mounting, the impedance is lower than that of bonding wire connection, so communication performance can be further improved.

In this embodiment, the antenna circuit 54 is also formed on the back surface of the multilayer printed wiring board 11. The antenna circuit 54 on the front surface and the antenna circuit 54 on the back surface are electrically connected by a through hole 16 passing through the multilayer printed wiring board 11 in the stacking direction. Note that the method of electrically connecting the antenna circuit 54 on the front surface and the antenna circuit 54 on the back surface is not limited to through holes, and may also be a method such as build-up connection using laser vias or end surface electrodes. good. The connection between the antenna circuit 54 on the front surface and the antenna circuit 54 on the back surface is formed during the manufacturing process of the multilayer printed wiring board 11.
Since there are no mounted components or wiring on the front and back surfaces of the multilayer printed wiring board 11, the front and back surfaces of the board can be effectively used as the antenna circuit 54, so that sufficient communication performance can be ensured.

Note that a solder resist is applied to the front and back surfaces of the multilayer printed wiring board 11. By forming a solder resist layer on the front and back surfaces of the multilayer printed wiring board 11, the solder resist layer protects the antenna circuit 54 and serves as an insulating film that insulates the antenna circuit 54.
Furthermore, in order to protect and insulate the antenna circuit 54, the outer periphery of the multilayer printed wiring board 11 can be sealed with resin.

In the embodiment shown in FIG. 2, the transmitting/receiving unit 52 is arranged on the back side of the outermost layer 11a, the sensor unit 50 and the control unit 51 are arranged on the front side of the intermediate layer 11b, and A power supply section 53 is arranged at. Note that although the antenna circuit 54 is formed on the back side of the backmost layer 11c, no element is arranged on the front side of the backmost layer 11c.
In this way, the elements 50, 51, 52, and 53 necessary for the sensing operation are arranged facing each other in the outermost layer 11a, the intermediate layer 11b, and the backmost layer 11c that constitute the multilayer printed wiring board 11. Resin is filled between the layer 11a and the intermediate layer 11b and between the intermediate layer 11b and the backmost layer 11c, and each element 50, 51, 52, 53 is sealed with the resin.

For this reason, each element 50, 51, 52, and 53 is sealed, so compared to products that are covered with something like a lid in a later process, there are no cavities and they are less affected by the external environment such as humidity and dust. It is less susceptible to damage and can have high reliability.
In addition, in a flat component arrangement such as in a surface mount product, wiring between components tends to become redundant, but in a wireless sensor using a multilayer printed wiring board as in the present invention, the wiring length is reduced by utilizing the spaces between the layers of the multilayer board. Since it can be made shorter, it is possible to miniaturize the product while improving its electrical characteristics. In particular, the wiring length has a large effect on high frequency ranges or when using with very low power, so it is possible to improve the characteristics of wireless communication.

The material used for resin sealing may be a printed wiring board material such as epoxy resin, or other resins. Alternatively, a combination of a plurality of resins may be used.
Resin sealing may be performed after each element is mounted, or may be performed simultaneously when the printed wiring board is multilayered. In this case, by creating multiple layers using high-vacuum equipment, the resin can flow well into the spaces of each layer, and the elements can be fixed, thereby increasing reliability.

FIG. 3 shows an embodiment in which the antenna circuit is formed only on the surface. Note that the same components as those in the embodiment shown in FIG. 2 are given the same reference numerals, and the description thereof will be omitted.
In the embodiment shown in FIG. 3, the antenna circuit 54 is formed only on the surface layer of the multilayer printed wiring board 11, and a solder resist is applied thereto.

Note that in this embodiment, the antenna circuit is not arranged on the back layer of the multilayer printed wiring board 11, but the land 18 is formed on the back layer through the through hole 16 that is electrically connected to the antenna circuit 54 on the surface layer. You can.

In the embodiments of FIGS. 2 and 3 described above, the multilayer printed wiring board 11 is composed of 4 to 6 layers including the outermost layer 11a, the intermediate layer 11b, and the backmost layer 11c, but the number of layers is It is not limited to 4 to 6 layers.

FIG. 4 shows a schematic configuration diagram when the sensor section is provided outside the wireless sensor.
In this case, the sensor section 50 is installed directly on the measurement object 30.
Further, a control section 51, a transmitting/receiving section 52, and a power supply section 53, which are elements other than the sensor section 50, are built three-dimensionally within the multilayer printed wiring board 11, and this is referred to as a main body section 34.
The configuration of the main body section 34 is the same as that of the wireless sensor 10 shown in FIGS. 1 to 3 except that the sensor section 50 is removed, and the other configurations are the same, so a description thereof will be omitted.

The sensor section 50 and the main body section 34 are connected by an external wiring 32 consisting of a signal line and a power line. It is preferable to provide a tap connectable to the external wiring 32 on the surface or side surface of the main body part 34.
By providing the sensor section 50 outside the main body section 34 in this way, the sensor section can be installed even in small gaps where the installation space is small, or in places where it is difficult to install the wireless sensor 10 due to high temperatures. 50 can be installed.
Furthermore, in this case, the sensor unit 50 can be brought into direct contact with the object to be measured, so that sensing errors can be minimized.
The main body section 34 may be installed in the measurement object 30 on which the sensor section 50 is installed if there is a suitable place for attachment on the measurement object 30 on which the sensor section 50 is installed, or it may be installed on the measurement object 30 on which the sensor section 50 is installed. If there is no suitable location, it may be installed at any location other than the measurement target 30.

(object to be measured)
Objects to be measured include machines, equipment, structures, vehicles, and the like. The part to which the wireless sensor 10 is attached to the object to be measured is preferably a metal body, and the metal body may be made of copper, aluminum, titanium, stainless steel, iron, or the like. Note that the location where the wireless sensor 10 is attached is not limited to a metal body, but may be a non-metal body, and a container containing a liquid or the like may also be used as the measurement target.

(Attachment to measurement target)
Figure 5 shows the wireless sensor attached to the object to be measured.
The wireless sensor 10 and the object to be measured 30 can be fixed using double-sided tape 40.
Note that the method of fixing the wireless sensor 10 to the measurement object 30 is not limited to the double-sided tape 40, and for example, the wireless sensor 10 may be directly fixed to the measurement object 30 with bolts, screws, or the like. Alternatively, it may be fixed using adhesive or solder.

(Sensor part)
The sensor unit 50 includes a temperature sensor that measures temperature changes, an acceleration sensor that measures acceleration changes, a humidity sensor that measures humidity changes, a pressure sensor that measures pressure changes, a magnetic sensor that measures magnetic changes, and a light amount change. A light sensor, a volume sensor that measures sound, a distance sensor that measures distance, a flow sensor that measures the flow rate of liquid or gas, a gyro sensor that measures angular velocity, an infrared sensor that measures infrared light, a vibration sensor that measures vibration, or at least one of other sensors.
However, the type of sensor unit 50 is not limited to these sensors.

(control unit)
The control unit 51 has a function of calculating and digitizing sensor data from the sensor unit 50 and a function of controlling the overall operation of the wireless sensor 10.
Further, sensor data from the sensor section 50 can also be stored in a storage area within the control section 51. The sensor data to be stored is data digitized within the control unit 51. Note that the storage area for storing sensor data is not limited to the storage area in the control unit 51, and a storage area may be provided in the transmitting/receiving unit 52, or other memory for storage may be provided.

The wireless sensor 10 is equipped with an identification ID for individual identification. As a result, when using a large number of wireless sensors 10, such as several thousand pieces, sensor data can be linked without confusion. Although the identification ID is held by the control unit 51 and/or the transmitting/receiving unit 52, the identification ID may be held using an external memory other than that.
In the case of a passive communication method or active communication method that has an identification ID in advance, it can be used, and when using other communication methods, individual identification can be made by adding a separate identification ID. .

(transmission/reception section)
The transmitting/receiving unit 52 includes a semiconductor for wireless communication, an antenna for external communication, and a memory for storing settings. The transmitting/receiving unit 52 can use 920 MHz UHF band communication and 2.4 GHz band communication, but may also use frequency bands other than those mentioned above.
Further, as the communication method of the transmitting/receiving unit 52, it is preferable to adopt a semi-passive communication method when it is desired to suppress power consumption, and an active communication method can be adopted when there is sufficient power. This makes it possible to extend the communication distance and increase the degree of freedom of communication.

(Power supply part)
The power supply section 53 can include a power generation element such as a thermoelectric power generation harvester, a vibration power generation harvester, and other harvester elements in addition to a battery or a solar cell. Further, an element that controls voltage or an element that stores electricity may be provided.

10 Wireless sensor 11 Multilayer printed wiring board 11a Top layer 11b Intermediate layer 11c Bottom layer 12 Metal layer 14 Via 16 Through hole 18 Land 20 Sensor part 30 Measurement object 32 External wiring 34 Main body part 40 Double-sided tape 50 Sensor part 51 Control Section 52 Transmission/reception section 53 Power supply section 54 Antenna circuit

Claims (10)

A wireless sensor used by being attached to an object to be measured,
The elements used for sensing operation are arranged three-dimensionally within the multilayer printed wiring board, and the multilayer printed wiring board is integrally sealed with resin.
Antenna circuits used for external transmission and reception of sensor data are electrically connected to each other on the surface layers of both sides of the multilayer printed wiring board , and
A wireless sensor that is attached to a metal body as the object to be measured . a sensor unit that acquires the state of the object to be measured;
a transmitting/receiving unit that externally communicates data obtained by the sensor unit;
The wireless sensor according to claim 1, further comprising a power supply unit that supplies power to at least the sensor unit and the transmitter/receiver unit. 3. The wireless sensor according to claim 2, further comprising a control section that executes calculation and digitization of data obtained by the sensor section and overall operation management. The transmitting/receiving section is arranged in the outermost layer inside the resin-sealed multilayer printed wiring board, and the transmitting/receiving section and the antenna circuit are connected at the shortest distance. The wireless sensor described in 3. The antenna circuits formed on both sides of the multilayer printed wiring board are electrically connected to each other by a structure formed in a manufacturing process of the multilayer printed wiring board. The wireless sensor according to any one of the above. a sensor unit that is attached to the object to be measured and acquires the state of the object to be measured;
A main body part that is communicably connected to the sensor part by external wiring,
Elements used for sensing operations other than the sensor section are three-dimensionally arranged within the multilayer printed wiring board, and the multilayer printed wiring board is integrally sealed with resin.
Antenna circuits used for external transmission and reception of sensor data are electrically connected to each other on the surface layers of both sides of the multilayer printed wiring board , and
A wireless sensor that is attached to a metal body as the object to be measured . The main body portion is
a transmitting/receiving unit that externally communicates data obtained by the sensor unit;
The wireless sensor according to claim 6, further comprising a power supply section that supplies power to at least the sensor section and the transmitter/receiver section. The main body portion is
8. The wireless sensor according to claim 6, further comprising a control section that executes calculations, digitization, and overall operation management of the data obtained by the sensor section. 8. The wireless communication device according to claim 7 , wherein the transmitting/receiving section is disposed in the outermost layer inside the resin-sealed multilayer printed wiring board, and the transmitting/receiving section and the antenna circuit are connected at the shortest distance. sensor. The antenna circuits formed on both sides of the multilayer printed wiring board are electrically connected to each other by a structure formed in a manufacturing process of the multilayer printed wiring board. The wireless sensor according to any one of the above.