Patent Application
20160282977
This disclosure relates generally to the field of capacitive sensing and, more specifically, to a capacitive sensing assembly including a thin film plastic.
Since its inception, capacitive sensing technology has aided biometric identification and authentication processes. In many cases, a single biometric marker can be used to uniquely identify an individual in a manner that cannot be easily replicated or imitated. The ability to capture and store biometric data in a digital file of minimal size has yielded immense benefits in fields such as law enforcement, forensics, and information security.
However, the widespread adoption of capacitive sensing technology in a broad range of applications has faced a number of obstacles. Among these obstacles is the need for a separate and distinct apparatus for capturing the biometric data, typically referred to as a sensor. As handheld devices begin to take on a greater range of functionality and more widespread use, engineers and designers of such devices are constantly seeking ways to maximize sophistication and ease of use while minimizing size and cost. Typically, such devices incorporate only those input/output components that are deemed to be essential to core functionality, e.g., a display screen and a limited set of buttons. As such, placing the sensor within electronic devices has been challenging, given the limited amount of space for additional components.
One embodiment provides a capacitive sensing stackup, including: a thin film plastic; an injection molded plastic component bonded to the thin film plastic, wherein the injection molded plastic component forms a cavity bounded by the injection molded plastic and the thin film plastic that exposes at least a portion of the thin film plastic; and, a capacitive sensor assembly including a plurality of sensor electrodes configured to be driven with a capacitive sensing signal, wherein the capacitive sensor assembly is coupled to the thin film plastic in the cavity formed by the injection molded plastic component.
Another embodiment provides a method for manufacturing a capacitive sensing stackup for capacitive sensing. The method includes: providing a thin film plastic; injection molding an injection molded plastic component, wherein the injection molded plastic component is bonded to the thin film plastic, and wherein the injection molded plastic component forms a cavity bounded by the injection molded plastic component and the thin film plastic that exposes at least a portion of the thin film plastic; and, securing a capacitive sensor assembly including a plurality of sensor electrodes configured to be driven with a capacitive sensing signal to the thin film plastic, wherein the capacitive sensor assembly is coupled to the thin film plastic in the cavity formed by the injection molded plastic component.
Yet another embodiment provides a mobile computing device that includes a housing body and a capacitive sensing stackup embedded in the housing body. The capacitive sensing stackup include: a thin film plastic, an injection molded plastic component bonded to the thin film plastic, wherein the injection molded plastic component forms a cavity bounded by the injection molded plastic and the thin film plastic that exposes at least a portion of the thin film plastic, and, a capacitive sensor assembly including a plurality of sensor electrodes configured to be driven with a capacitive sensing signal, wherein the capacitive sensor assembly is coupled to the thin film plastic in the cavity formed by the injection molded plastic component.
Electronic devices such as mobile phones, tablet devices, and laptop computers often use various forms of very high gloss substrates as the cover of such devices. These substrates are often made of materials such as glass, clear or colored plastic, acrylic, or any other material having high gloss surfaces.
In order to fit a biometric sensor (such as a fingerprint sensor) into the housing of an electronic device, a very high gloss surface can be used on an upper portion of the biometric sensor so as to match the surrounding surfaces of the electronic device in which the biometric sensor is incorporated. Some embodiments of the disclosure utilize IMD (in-mold decoration) manufacturing techniques to provide a top cover over a fingerprint sensor. IMD manufacturing is a process technology by which thin plastic layers are created that normally would not be possible using traditional injection molding. For a fingerprint sensor to function, the material used above the conductive portion of the sensor should be very thin to maintain usable signal-to-noise levels, for example 200 microns or thinner. Some capacitive sensing techniques may be able to successfully operate through a thicker material, but a thinner material usually improves the signal detected by the sensor. An IMD-formed thin plastic layer over a fingerprint sensor protects the sensor from contamination and ingress of fluids. In embodiments where the sensor is integrated into a button of an electronic device, the IMD-formed thin plastic layer can provide decoration so the button is aesthetically pleasing.
In other embodiments, a COF (chip on flex) flex circuit itself can be an IMD layer, as opposed to providing an IMD layer separate from the fingerprint sensor. In these embodiments, the COF would not be bonded to the IMD layer, but rather is a part of the IMD film itself. For example, a sensor that includes copper traces on its top surfaces can be covered with an ink layer that can be color coded to match a customer's requirements. A polyimide (PI) film layer can then be deposited onto the ink layer, forming the IMD film.
As described herein, electronic devices can be configured to include a variety of components and features including, but not limited to, a display, a touch screen, a scratch-resistant cover (e.g., lens), a storage device, a system on a chip, one or more CPU (central processing unit) cores, one or more GPU (graphics processing unit) cores, memory, wireless network connectivity (e.g., 802.11 b/g), Bluetooth® connectivity, a camera, one or more speakers, a battery (e.g., built-in, rechargeable lithium-ion polymer battery), a power connector, among other things. Additionally, electronic devices and electronic device displays can be configured to include, for example, a button or form factor for user interaction (e.g., power on and off, volume change, etc.). Buttons can be provided and integrated in the electronic device housing or be included as part of an electronic device screen.
Biometric sensors can include, for example, a fingerprint sensor, a velocity sensor, a temperature sensor, an iris or retina sensor, among other sensors. An integrated circuit is electrically connected to the biometric sensor. Conductive traces of the biometric sensor can be etched or otherwise formed on an upper side of a substrate. A protective coating is applied to the upper surface of the substrate, over the biometric sensor to provide electrical isolation and mechanical protection of the sensor. Alternatively, conductive traces of the sensor can be formed on a bottom-side of a substrate, where the substrate can act as a protective coating and can be further improved another coating applied to the upper surface.
In the sensor packagings disclosed herein, a biometric sensor, such as a fingerprint sensor, is integrated with an electronic device display or electronic device housing and is positionable on or adjacent to an uppermost surface of the electronic device display or housing such that the fingerprint sensor is within about 250 microns or less of a finger when the finger comes in contact with the uppermost surface of the electronic device. In at least some configurations, the sensor packagings can be configured such that the biometric sensor is configured to be positioned within about 200 microns of a finger, more preferably within 150 microns, still more preferably within 100 microns, or even more preferably within 50 microns of a finger, when the finger comes in contact with the uppermost surface of the electronic device. In at least some configurations, the sensor packagings can be configured such that the biometric sensor is configured to be positioned more than 50 microns away from a finger, more than 100 microns away from the finger, more than 150 microns, and in some configurations more than 200 microns from a finger surface when the finger comes in contact with the uppermost surface of the electronic device. Capacitive sensors may be capable of successfully performing fingerprint detection and authentication through a wide range of material thickness. For example, in certain configurations a capacitive sensor may be able to successfully detect a finger even with 300 or more microns of material between the capacitive sensor and the finger. However, a capacitive sensor usually is more effective in detecting a fingerprint through a low material thickness.
In some configurations, a single chip can be provided that controls one or more of the display, the touch screen and the fingerprint sensing functions. Additionally, the biometric sensor can be incorporated in the electronic device so that the surface of the electronic device incorporating the sensor packagings presented to a user is smooth or substantially smooth. Displays and systems can be configured such that they are integrally formed so that they act in a unified manner or such that the completed electronic device is comprised of a single component.
The housing 110 has a cover layer 120 over a sensor component (not shown in
The cover layer 120 is positioned such that it obscures electronic components located within the housing 110. For example, in a touch screen interface, a portion of the interface that is not covered by cover layer 120 can be configured to have a plurality of touch screen sensors. The plurality of touch screen sensors can be any suitable conductor, including a transparent conductor, for example, from a layer of patterned indium tin oxide (ITO), carbon nanotubes, metal nanowires, conductive polymers or fine metal lines (e.g., copper lines). Additionally, a fingerprint sensor can, but need not, be positioned in a location where the cover layer 120 is also present. In another configuration, an aperture can be provided in the cover layer 120 corresponding to all or part of a location where the fingerprint is sensed. The cover layer 120 can be separate from the sensor itself or can be formed integral with the sensor, as described in greater detail herein.
The biometric sensor is connected with one or more conductive traces 138 to a processing system 152. The processing system 152 can be included outside of the housing 110, as shown in
As shown in
One reason for placing the sensor package 250 behind the cover layer 120 rather than positioning the sensor package 250 to directly be in contact with a finger, is that the cover layer provides protection from water, liquids, and other debris that may be harmful to the sensor package. The cover layer 120 can serve to protect the sensor package 250, as well as other circuitry or electronics from damage.
In addition to what is shown in
At stage 310, a thin film plastic layer 302 is provided. In some embodiments, the thin film plastic layer 302 is formed by the IMD manufacturing process. According to some embodiments, IMD is a type of plastic molding process used for decorating plastic surfaces with an abrasion-resistant coat and optionally color. A carrier foil is placed inside an opened mold. The mold can be constructed so that the back side of the carrier foil rests against a flat wall. The carrier foil can be bent, if desired. The carrier foil carries dried ink layers that are to be transferred to a plastic part with the ink facing towards the side of the mold into which plastic is inserted. After the mold is filled with plastic, the ink adheres to the plastic and is removed from mold.
At stage 320, one or more injection molded plastic components 304 are injection molded and bonded to the thin film plastic layer 302. The injection molded plastic components 304 and the thin film plastic layer 302 form a cavity 308 that exposes at least a portion of the thin film plastic layer 302. In one embodiment, the injection molded plastic components 304 are thicker than the thin film plastic layer 302.
At stage 330, a sensor package 306 including a plurality of sensor electrodes configured to be driven with a capacitive sensing signal is coupled to the thin film plastic layer 302 in the cavity 308 formed by the injection molded plastic components 304 and the thin film plastic layer 302.
In some embodiments, an illumination source can be added to the assembly so that light from the illumination source travels through the thin film plastic layer 302. In other words, the assembly may comprise a button that can light up.
In yet another embodiment, the cavity can include five sides formed by injection molded plastic components. Starting with the embodiment shown in
At step 604, graphics and/or ink are applied to the thin film plastic layer. In some embodiments, step 604 is optional and is not performed.
At step 606, thermal forming of the thin film plastic layer is performed. Thermal forming forms the thin film plastic layer into a desired shape. For example, the thin film plastic may be formed according the surface of a button or surrounding features. In some embodiments, step 606 is optional and is not performed.
At step 608, one or more injection molded plastic components are injection molded and bonded to the thin film plastic layer. The injection molded plastic components and the thin film plastic layer form a cavity that exposes at least a portion of the thin film plastic layer.
At step 610, a sensor package is secured to the thin film plastic layer within the cavity. In some embodiments, the sensor package is secured to the thin film plastic layer with an adhesive. In other embodiments, if the sensor package is appropriately sized, the sensor package is secured to the thin film plastic layer via friction between the sensor package and the one or more injection molded plastic components.
While certain steps were specifically mentioned as optional, it should be appreciated that the steps of
As shown in
In other embodiments, a COF (chip on flex) flex circuit itself can be the IMD layer. In these embodiments, the COF would not be bonded to the formed IMD layer, but rather is a part of the IMD film itself. As shown in the stackup 1100 of
The embodiments and examples set forth herein were presented in order to best explain the present disclosure and its particular application and to thereby enable those skilled in the art to make and use the invention. However, those skilled in the art will recognize that the foregoing description and examples have been presented for the purposes of illustration and example only. The description as set forth is not intended to be exhaustive or to limit the invention to the precise form disclosed.
All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
The use of the terms “a” and “an” and “the” and “at least one” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term “at least one” followed by a list of one or more items (for example, “at least one of A and B”) is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
