Patent Application
20190036004
Embodiments of the present invention relate generally to the manufacture of a strain and/or sensor system suitable for remote sensing. In particular, embodiments of the present invention relate to piezoelectric structures that convert strain or pressure into an electrical output to drive a light source.
Strain gauges have been used to provide outputs that can be correlated to strain or pressure in a system. The use of such sensors is becoming increasingly important with the advancement of machine learning and flexible devices (e.g., wearables, flexible displays, etc.). In machine learning applications a pressure sensor may be used to monitor and adjust the amount of pressure applied by a robotic arm during handling or moving fragile components. With respect to flexible devices, when excessive strain is applied to a flexible device, mechanical or electrical failure of certain components may occur. As such, a pressure sensor may be used to provide an indication to the user that a certain pressure or strain threshold has been reached.
However, current strain gauges have significant limitations that prevent them from being integrated successfully in flexible devices and in certain machine learning applications. One drawback of existing strain gages is that they require an active circuit (e.g., Wheatstone bridge) for measuring the resistance change and then correlating the change in resistance to the amount of pressure applied. Accordingly, an external power source is needed for operation of the strain gage and battery life is reduced. Additionally, strain gages that are currently available produce an electrical signal that needs to be picked up by a circuit that is electrically coupled to the strain gage. As such, remote sensing is not currently possible. Accordingly, if a robotic arm is manipulating a component that is pressure sensitive, the robotic arm needs to be electrically coupled with the component in order to determine the pressure that is being applied to the component.
Described herein are systems that include a piezoelectric strain and/or pressure sensor formed on a substrate and coupled to a visual indicator and methods of forming such piezoelectric sensors. In the following description, various aspects of the illustrative implementations will be described using terms commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. However, it will be apparent to those skilled in the art that the present invention may be practiced with only some of the described aspects. For purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the illustrative implementations. However, it will be apparent to one skilled in the art that the present invention may be practiced without the specific details. In other instances, well-known features are omitted or simplified in order not to obscure the illustrative implementations.
Various operations will be described as multiple discrete operations, in turn, in a manner that is most helpful in understanding the present invention, however, the order of description should not be construed to imply that these operations are necessarily order dependent. In particular, these operations need not be performed in the order of presentation.
Embodiments of the invention include a sensor system that converts a mechanical input (e.g., applied strain or pressure) into an optical output as an indicator of the strain. According to an embodiment, the sensor system relies on a piezoelectric sensor. When strain or pressure is applied to the piezoelectric material, an electrical output (e.g., a voltage) is produced. As such, the sensor systems described in accordance with embodiments of the invention allow for a sensor that may not require an external power source. Since the driving signal to create the optical output is the mechanical strain applied by the user, the amount of power that needs to be provided by a separate power source, such as a battery, is reduced. This is advantageous in cases where long battery life is desired or when it is not practical to frequently remove and change batteries (e.g., in some Internet of Things (IoT)) applications where the sensor or battery are not easily accessible.
According to an embodiment, the electrical output may be used to activate a light source. For example, the light source may be a light emitting diode (LED). Since an optical light source is used to measure the strain, monitoring the strain does not require a wired connection to the device, thereby enabling remote sensing. This is particularly advantageous in machine learning applications. As an example, if a robotic arm is handling a pressure sensitive object, a detector on the robotic arm that is sensitive to the light (e.g., a photodetector) may be used to detect the intensity of the light emitted by the light source.
In some embodiments of the invention, the piezoelectric sensor may be fabricated into the substrate itself. The removal of an additional package to house the piezoelectric sensor reduces the thickness of the device. Additionally, manufacturing piezoelectric sensors into organic substrates allows for a decrease in the manufacturing cost. Previously, piezoelectric components needed to be manufactured on substrates that can withstand high temperatures, such as silicon substrates. High temperature compatible substrates such as these were used because the piezoelectric material needed to be annealed at temperatures greater than approximately 500° C. in order to crystallize the piezoelectric material. However, embodiments of the present invention allow for piezoelectric material to be deposited and crystalized at much lower temperatures by using a pulsed laser annealing process, described in greater detail below. Therefore, piezoelectric sensors are able to be fabricated on low temperature organic substrates that are typically used in package and board manufacturing. Furthermore, flexible substrates are also commonly low temperature organic materials. As such, embodiments of the invention allow for the integration of piezoelectric sensors into flexible devices, thereby enabling the use in wearables and flexible displays.
Technologies and materials developed for package/board processing are significantly less expensive than technologies and materials used for semiconductor processing. Fabricating piezoelectric sensors directly in the substrate or board reduces the cost over piezoelectric components formed on silicon because of the large panels (e.g., 510 mm×515 mm) used for organic substrate and board fabrication. Since organic substrates are usually batch manufactured in large panels, large area integration of piezoelectric sensors is also facilitated by embodiments of the invention. This enables the parallel manufacturing of large numbers of piezoelectric sensors cost-effectively. Additionally, the materials used in package and board systems are less expensive than silicon-based devices. Furthermore, since the piezoelectric sensors may be directly manufactured as part of the package substrate or board, they do not require an additional assembly operation.
Referring now to
According to an embodiment, the sensor system 100 may optionally include a signal conditioning circuit 120. The signal conditioning circuit 120 may include circuitry that converts the electrical output 104 generated by the piezoelectric sensor 110 into an appropriate input 104′ for driving the light source 130. For example, the conditioning circuit may include an amplifier, a comparator, or any other circuitry needed to modify the electrical output 104.
In one embodiment, the sensor system 100 may be operated in a digital (i.e., on/off) mode. In such embodiments, a predetermined strain or pressure threshold may be set so that the light source 130 is activated before mechanical or electrical damage occurs to the system being monitored. For example, the light source 130 may remain off as long as the strain or pressure applied to the sensor is below the predetermined threshold, and the light source 130 may be activated when the strain or pressure exceeds the threshold value. Accordingly, when the light source 130 is activated, the user of the system is provided with an optical indication that no additional stress or pressure should be applied to the device. In an embodiment where a digital mode of operation is used, the signal conditioning circuit 120 may include a comparator. The comparator may be used to compare a voltage obtained from the piezoelectric sensor 110 to a voltage associated with the predetermined threshold value. When the electrical output 104 from the piezoelectric sensor 110 exceeds the predetermined threshold value, the signal conditioning circuit may then deliver an input 104′ to the light source 130 to cause the light source to turn on.
An additional embodiment of the invention may omit the signal conditioning circuit 120 when a digital mode of operation is desired. In such an embodiment, the light source 130 may be chosen so that the forward voltage required to turn on the light source 130 is equal to the predetermined threshold value. Accordingly, the electrical output 104 from the piezoelectric sensor will only activate the light source 130 when the strain or pressure exceeds a predetermined value. In one example, a light emitting diode (LED) may be used as the light source 130.
In another embodiment, the sensor system 100 may be operated in an analog mode. Such an embodiment may be particularly useful to determine the actual strain or pressure that is being applied to the piezoelectric sensor. The intensity of the light emitted by the light source 130 may be proportional to the voltage produced by the piezoelectric sensor 110. Accordingly, when the sensor system 100 has been calibrated, a strain or pressure value may be correlated with the intensity of the light emitted from the light source. For example, the intensity of the light may be determined by an optical sensor (not shown in
Referring now to
In an embodiment, the electrical output from the piezoelectric sensor 210 may be sent to the signal conditioning circuit 220 and/or the light source 230 by conductive traces 207 formed on or in the substrate. The conductive traces may be any suitable conductive material, such as copper, tin, aluminum, alloys of conductive materials, and may also include multiple layers, such as seed layers, barrier layers, or the like. Furthermore, while the conductive traces 207 are illustrated as being substantially straight line connections between components, embodiments of the invention are not limited to such configurations. For example, the conductive traces 207 may be formed in a meandering pattern that allows for greater flexing, stretching, bending, or the like, before being damaged.
According to an embodiment, the sensor system 200 may also include one or more strain recording components 208. A strain recording component 208 may be a device that indicates that a certain level of strain has been applied to the device. A strain recording component 208 may allow for easy inspection (e.g., for warranty protection). For example, a warranty may be voided by extreme use of the device (e.g., a user may negligently apply strain or pressure far beyond normal usage). As such, a manufacture who needs to determine whether the warranty was voided or not may inspect the strain recording component 208 to see if damage will be covered by the warranty. In an embodiment, the strain recording component 208 may be a fuse. The fuse may be chosen so that any strain or pressure beyond normal usage will generate an electrical output signal from the piezoelectric sensor 210 that will blow the fuse. As such, when the fuse is blown, the warranty may be voided. Since a fuse 208 requires no additional power or memory to permanently record the excessive strain, power consumption and cost of the device are not significantly increased.
While the strain recording component 208 is shown as being positioned along a conductive trace 207, embodiments are not limited to such configurations. For example, the strain recording component 208 may be formed as part of the sensor 210, the signal conditioning circuit 220, the light source 230, or any other location in the piezoelectric sensor system 200. Furthermore, while a fuse is included as one example of a strain recording device 208, embodiments are not so limited. For example, the strain recording device 208 may be a memory on the signal conditioning circuit 220 that can be recorded on when an excessive strain or pressure is applied to the substrate 205. During inspection, if the memory on the signal conditioning circuit 220 has recorded that excessive strain was applied, then the warranty may be voided.
Embodiments may also include a signal conditioning circuit 220. As illustrated, the signal conditioning circuit 220 may be mounted to the substrate 205. For example, the signal conditioning circuit may be a die that is surface mounted to the substrate. The die may include any suitable circuitry, such as a comparator, an amplifier, etc. For example, the signal conditioning circuit 220 may be an application-specific integrated circuit (ASIC).
According to an embodiment, the light source 230 may also be mounted to the substrate 205. The light source 230 may be any suitable light source. In one embodiment, the light source 230 may include one or more LEDs. As illustrated in
Referring now to
In the illustrated embodiment, the piezoelectric sensor 310 is integrated into the substrate 305. According to an embodiment, the piezoelectric sensor 310 includes a moveable beam 312 that spans across a cavity 306 formed in the substrate 305. For example, the moveable beam 312 may be anchored at each end to the substrate 305 and/or a conductive pad or via 309. Since a central portion of the moveable beam 312 is not supported from below, the central portion of the moveable beam 312 may be displaced towards or away from the substrate when strain or pressure is applied to the substrate 305. The extent of the displacement of the moveable beam 312 is measured by converting the mechanical deformation into an electrical output with piezoelectric regions 314 formed proximate to the ends of the moveable beam 312. The deflection of the moveable beam 312 induces strain in the piezoelectric regions 314, which generates a voltage across the piezoelectric region 314 that is proportional to the strain or pressure. In order to detect the amount of deflection, the piezoelectric regions 314 may extend out over the cavity 306. Since the piezoelectric regions 314 are mechanically coupled to the central portion of the moveable beam 312 that deflects under pressure or strain, the piezoelectric regions will also be strained, thereby producing an output voltage. While the piezoelectric regions 314 are shown on both ends of the moveable beam 312, embodiments are not limited to such configurations. For example, a piezoelectric region 314 may be formed on only one end of the moveable beam 312. According to an additional embodiment of the invention, the piezoelectric region 314 may extend across the entire moveable beam 312.
In order to transfer the voltage generated by the piezoelectric regions 314 to the light source 330, electrodes are formed above and below the piezoelectric regions 314. In one embodiment, the moveable beam may be used as one of the electrodes, and the piezoelectric region 314 may be formed directly over the moveable beam 312. Additionally, a second electrode 316 may be formed over a top surface of the piezoelectric regions 314. According to an embodiment, the second electrode 316 and the moveable beam 312 may be any suitable conductive material (e.g., copper, aluminum, alloys, etc.). In order to deliver the voltage from the piezoelectric regions 314 to the light source 330, the electrode 316 and the moveable beam 312 may be electrically coupled to the conductive pads or vias 309 on the substrate 305. In an additional embodiment, the electrodes 316 and the moveable beam 312 may be electrically coupled directly to conductive traces (not shown) and the conductive pads 309 may be omitted.
It is to be appreciated that piezoelectric material typically requires a high temperature anneal (e.g., greater than 500° C.) in order to provide the proper crystal structure to produce the piezoelectric effect. As such, depositing piezoelectric material generally requires a substrate that is capable of withstanding high temperatures (e.g., silicon). Flexible substrates, such as organic substrates described herein, typically cannot withstand temperatures above 260° C. However, embodiments of the present invention allow for piezoelectric regions 314 to be formed at much lower temperatures. For example, instead of a high temperature anneal, embodiments include depositing the piezoelectric regions 314 in an amorphous phase and then using a pulsed laser to crystallize the piezoelectric regions 314. According to an embodiment, the laser annealing process may use an excimer laser with an energy density between approximately 10-100 mJ/cm2 and pulse width between approximately 10-50 nanoseconds. For example, the piezoelectric regions 314 may be deposited with a sputtering process, an ink jetting process, or the like. According to an embodiment, the piezoelectric layer may be lead zirconate titanate (PZT), potassium sodium niobate (KNN), zinc oxide (ZnO), aluminum nitride (AlN), or combinations thereof.
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In order to generate an electrical output when the moveable beam 412 is deflected, an additional electrode 415 may be formed in contact with the piezoelectric region 414. The electrode 415 may be formed directly over the insulating layer 411. Additionally, the electrode 415 may be electrically coupled to a conductive pad or via 409 on the substrate 405. As such, the voltage generated across the piezoelectric region 414 may be transmitted to the light source 430, even when the moveable beam 412 is not part of the conductive path between the piezoelectric sensor 410 and the light source 430.
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While the piezoelectric sensor 510 is not integrated into the substrate 505, several benefits still remain when the piezoelectric sensor 510 is used in the sensing system 500. For example, the power consumption of the device is still decreased compared to typical strain gauges, such as those described above. Even though it is a discrete component, the piezoelectric sensor 510 is able to generate an output voltage that is proportional to the strain or pressure applied. As such, the light source 530 may be driven without significantly increasing power consumption of the device. Additionally, the combination of the piezoelectric sensor 510 and the light source 530 allows for remote sensing, similar to the sensor systems described above.
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While
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Depending on its applications, computing device 800 may include other components that may or may not be physically and electrically coupled to the board 802. These other components include, but are not limited to, volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flash memory, a graphics processor, a digital signal processor, a crypto processor, a chipset, an antenna, a display, a touchscreen display, a touchscreen controller, a battery, an audio codec, a video codec, a power amplifier, a global positioning system (GPS) device, a compass, an accelerometer, a gyroscope, a speaker, a camera, and a mass storage device (such as hard disk drive, compact disk (CD), digital versatile disk (DVD), and so forth).
The communication chip 806 enables wireless communications for the transfer of data to and from the computing device 800. The term “wireless” and its derivatives may be used to describe circuits, devices, systems, methods, techniques, communications channels, etc., that may communicate data through the use of modulated electromagnetic radiation through a non-solid medium. The term does not imply that the associated devices do not contain any wires, although in some embodiments they might not. The communication chip 806 may implement any of a number of wireless standards or protocols, including but not limited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE 802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE, GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well as any other wireless protocols that are designated as 3G, 4G, 5G, and beyond. The computing device 800 may include a plurality of communication chips 806. For instance, a first communication chip 806 may be dedicated to shorter range wireless communications such as Wi-Fi and Bluetooth and a second communication chip 806 may be dedicated to longer range wireless communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others.
The processor 804 of the computing device 800 includes an integrated circuit die packaged within the processor 804. In some implementations of the invention, the integrated circuit die of the processor may be packaged on an organic substrate that includes one or more piezoelectric sensors, in accordance with implementations of the invention. The term “processor” may refer to any device or portion of a device that processes electronic data from registers and/or memory to transform that electronic data into other electronic data that may be stored in registers and/or memory.
The communication chip 806 also includes an integrated circuit die packaged within the communication chip 806. In accordance with another implementation of the invention, the integrated circuit die of the communication chip may be packaged on an organic substrate that includes one or more piezoelectric sensors, in accordance with implementations of the invention.
The above description of illustrated implementations of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific implementations of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize.
These modifications may be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific implementations disclosed in the specification and the claims. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.
Embodiments of the invention include a piezoelectric sensor, comprising: a cavity formed into an organic substrate; a moveable beam formed over the cavity and anchored to the organic substrate; a piezoelectric region formed over an end portion of the moveable beam, wherein the piezoelectric region extends at least partially over the cavity; and a top electrode formed over a top surface of the piezoelectric region.
Additional embodiments of the invention include a piezoelectric sensor, wherein the top electrode is electrically coupled to a first conductive pad or via, and wherein the moveable beam is electrically coupled to a second conductive pad or via.
Additional embodiments of the invention include a piezoelectric sensor, wherein the moveable beam has a uniform cross-section.
Additional embodiments of the invention include a piezoelectric sensor, wherein the moveable beam has an I-shaped cross-section.
Additional embodiments of the invention include a piezoelectric sensor, wherein the moveable beam has a length that is substantially greater than a width of the moveable beam.
Additional embodiments of the invention include a piezoelectric sensor, further comprising: an electrically insulating layer formed on a top surface of the moveable beam; and a bottom electrode formed over the electrically insulating layer, wherein the bottom electrode contacts the piezoelectric region.
Additional embodiments of the invention include a piezoelectric sensor, wherein the bottom electrode and the top electrode are each coupled to a different conductive pad or via on the substrate, and wherein the moveable beam is not electrically coupled to the piezoelectric region.
Embodiments of the invention include a sensor system, comprising: an organic substrate; a piezoelectric sensor coupled to the organic substrate; and a light source electrically coupled to the piezoelectric sensor, wherein an intensity of light emitted by the light source is at least partially controlled by an electrical output signal generated by the piezoelectric sensor.
Additional embodiments of the invention include a sensor system, wherein the piezoelectric sensor is a discrete component mounted to the organic substrate.
Additional embodiments of the invention include a sensor system, wherein the piezoelectric sensor is integrated into the organic substrate.
Additional embodiments of the invention include a sensor system, wherein the piezoelectric sensor comprises: a cavity formed into the organic substrate; a moveable beam formed over the cavity and anchored to the organic substrate; a piezoelectric region formed over an end portion of the moveable beam, wherein the piezoelectric region extends at least partially over the cavity; and a top electrode formed over a top surface of the piezoelectric region.
Additional embodiments of the invention include a sensor system, wherein the top electrode and the moveable beam are electrically coupled to the light source.
Additional embodiments of the invention include a sensor system, wherein the piezoelectric sensor further comprises: an electrically insulating layer formed on a top surface of the moveable beam; and a bottom electrode formed over the electrically insulating layer, wherein the bottom electrode contacts the piezoelectric region.
Additional embodiments of the invention include a sensor system, wherein the bottom electrode and the top electrode are each electrically coupled to the light source, and wherein the moveable beam is not electrically coupled to the piezoelectric region.
Additional embodiments of the invention include a sensor system, wherein the piezoelectric sensor and the light source are electrically coupled by one or more conductive traces.
Additional embodiments of the invention include a sensor system, wherein the conductive traces are meandering traces.
Additional embodiments of the invention include a sensor system, further comprising:
an electrical output conditioning circuit electrically coupled to the piezoelectric sensor, wherein the electrical output conditioning circuit modifies the electrical output signal generated by the piezoelectric sensor before it is delivered to the light source.
Additional embodiments of the invention include a sensor system, wherein the electrical output conditioning circuit includes an amplifier and/or a comparator.
Embodiments of the invention include a method of forming a piezoelectric sensor, comprising: forming a beam over an organic substrate; depositing a piezoelectric material over portions of the beam, wherein the piezoelectric layer has a substantially amorphous crystal structure; crystallizing the piezoelectric material with a pulsed laser anneal, wherein a temperature of the organic substrate does not exceed 260° C.; forming an electrode over a top surface of the piezoelectric material; and forming a cavity below a portion of the beam.
Additional embodiments of the invention include a method of forming a piezoelectric sensor, wherein the piezoelectric layer is deposited with a sputtering or ink-jetting process.
Additional embodiments of the invention include a method of forming a piezoelectric sensor, wherein the cavity is formed with a reactive ion etching process.
Additional embodiments of the invention include a method of forming a piezoelectric sensor, wherein the piezoelectric layer and the second electrode do not completely cover a top surface of the first electrode.
Embodiments of the invention include a sensor system for controlling a machine, comprising: an organic substrate; a piezoelectric sensor coupled to the organic substrate; a light source electrically coupled to the piezoelectric sensor, wherein an intensity of light emitted by the light source is at least partially controlled by an electrical output signal generated by the piezoelectric sensor; an electrical output conditioning circuit electrically coupled to the piezoelectric sensor, wherein the electrical output conditioning circuit modifies the electrical output signal generated by the piezoelectric sensor before it is delivered to the light source; and a photodetector mounted remotely from the organic substrate.
Additional embodiments of the invention include a sensor system for controlling a machine, wherein the piezoelectric sensor comprises: a cavity formed into the organic substrate; a moveable beam formed over the cavity and anchored to the organic substrate; a piezoelectric region formed over an end portion of the moveable beam, wherein the piezoelectric region extends at least partially over the cavity; and a top electrode formed over a top surface of the piezoelectric region.
Additional embodiments of the invention include a sensor system for controlling a machine, wherein the piezoelectric sensor further comprises: an electrically insulating layer formed on a top surface of the moveable beam; and a bottom electrode formed over the electrically insulating layer, wherein the bottom electrode contacts the piezoelectric region.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2016/025654 | 4/1/2016 | WO | 00 |
