Patent Application
20200273719
The present invention generally relates to the field(s) of flexible integrated circuits and the manufacturing thereof (e.g., integrated circuits for the Internet of Things [IoT], flexible batteries and/or battery control, flexible sensors and/or displays, wireless communication, identification and/or security devices, such as radio-frequency identification [RFID] tags, electronic article surveillance [EAS] tags, and near-field communication [NFC] tags, etc.). More specifically, embodiments of the present invention pertain to a flexible integrated circuit and methods of manufacturing the same and attaching the same to an antenna or other substrate.
Methods of attaching electronics (e.g., integrated circuits) to a target substrate (e.g., with an antenna or trace thereon) require precision, and therefore, complex equipment is used and/or low throughput results, which leads to high cost. Antenna-on-chip (AoC) processing solves this issue by allowing the chip to be placed on a target substrate that has a primary (large) antenna in an arbitrary (but close) location, and by fabricating a coupling (small) antenna directly on the integrated circuit (IC). However, this approach is inapplicable to products in which the IC must be attached directly to the substrate (e.g., to a trace or wire on a flexible substrate).
Attaching the electronics to the antenna or trace benefits from a low total thickness (e.g., to the level of paper) and an ability to maintain or maximize flexibility of the system as a whole.
This “Discussion of the Background” section is provided for background information only. The statements in this “Discussion of the Background” are not an admission that the subject matter disclosed in this “Discussion of the Background” section constitutes prior art to the present disclosure, and no part of this “Discussion of the Background” section may be used as an admission that any part of this application, including this “Discussion of the Background” section, constitutes prior art to the present disclosure.
The present invention produces and uses highly flexible, thin substrates with integrated electronics thereon in a process that comprises attaching a thin electronics chip (e.g., integrated circuit [IC]) to a target substrate at a high production throughput.
In one aspect, the present invention relates to a method of attaching an active device on one or more substrates to a metal carrier, comprising contacting the active device on the one or more substrates with the metal carrier; and applying pressure to and heating the active device on the one or more substrates and the metal carrier sufficiently to affix or attach the active device on the one or more substrates to the metal carrier.
In various embodiments, the active device comprises an integrated circuit, the substrate(s) comprise a metal substrate on the backside of the active device and a protective and/or carrier film on the frontside of the active device, and/or the metal carrier comprises a metal foil. The protective/carrier film may be or include an organic polymer. The metal foil may comprise a foil of stainless steel, aluminum, copper, titanium, molybdenum or an alloy thereof. When the substrate(s) comprise the metal substrate and the protective and/or carrier film, further embodiments of the method may further comprise thinning the metal substrate prior to contacting the active device, the metal substrate, and the protective and/or carrier film with the metal carrier.
In other or further embodiments, at least one of the substrate(s) is continuous, and a plurality of the active devices are on the continuous substrate. In some of these embodiments, the method may further comprise dicing at least the active device and the continuous substrate prior to contacting the active device and the substrate(s) with the metal carrier.
In some embodiments, the active device comprises a plurality of active devices on the substrate(s), and the method further comprises separating the active devices. In such embodiments, the substrate(s) may include at least one continuous substrate, and the plurality of active devices may comprise an n-device-wide array of the active devices on the continuous substrate. The continuous substrate may be a sheet or a roll, and the array of active devices generally comprises an m-by-n array of rows and columns of the active devices. Both m and n may be an integer of 2 or more. n is generally an integer of 2-8 (e.g., 3, 4, 5, etc.), but when the continuous substrate is a roll, m may be ≥100, 250, 1000, or more.
In various embodiments, separating the active devices may comprise (i) splitting or dividing the continuous substrate into n individual columns or rows of active devices, each on a divided strip of the continuous substrate; (ii) transferring each of one or more columns of the n-device wide array of active devices to a corresponding individual strip of the metal carrier such that a linear one-device-wide column of the active devices is on the corresponding individual strip of the carrier, offsetting the continuous substrate to align one or more next columns of the n-device-wide array with the corresponding individual strip(s) of the metal carrier, then transferring each of the next column(s) of the n-device-wide array of active devices to the corresponding individual strip(s) of the carrier while linearly maintaining the one-device-wide column of active devices on the corresponding individual strip(s) of the metal carrier; or (iii) using roll-to-roll processing, transferring the active devices from the continuous substrate to the metal carrier continuously or intermittently while advancing the continuous substrate at a first rate and advancing the metal carrier at a second rate greater than the first rate. The active devices may be intermittently transferred when advancement of the continuous substrate and the metal carrier is stopped or paused during application of pressure and heat to the active devices on the substrate(s) and the metal carrier.
Examples of suitable pressures in “hot stamping” may be from 15 to 350 N/cm2 (20-500 pounds per square inch [psi], or any value or range of values therein). Also, heating (i) the active device on the substrate(s) and (ii) the metal carrier in “hot stamping” may comprise heating a pressure-applying device or a common environment of (i) the active device on the substrate(s) and (ii) the metal carrier to a temperature of 80-200° C., or any value or range of values therein (e.g., 100-150° C.).
In some embodiments, the substrate(s) comprise a protective and/or carrier roll, and the metal carrier comprises a roll of metal foil. In such embodiments, (a) contacting the active device on the substrates with the metal carrier and (b) applying pressure to and heating (i) the active device on the substrates and (ii) the metal carrier comprises advancing the active device on the protective and/or carrier roll using one or more first rollers and advancing the roll of metal foil using one or more second rollers (e.g., roll-to-roll processing). At least one first roller and at least one second roller are configured to bring the active device on the protective and/or carrier roll into contact with the roll of metal foil. In some examples, the substrate(s) may further comprise a metal substrate on an opposite surface of the active device from the protective and/or carrier roll, and when applying pressure to and heating (i) the active device on the substrates and (ii) the metal carrier, the roller contacts the protective and/or carrier roll, and the metal substrate contacts the metal carrier.
Alternatively, applying pressure to the active device on the substrate(s) and the metal carrier may comprise pressing the active device on the substrate(s) into the metal carrier using a stamping die. The stamping die may comprise a pattern of (i) ridges or plateaus and (ii) troughs or depressions configured to transfer a pattern into either a metal layer in the substrate(s) or the metal carrier. For example, the pattern may comprise (a) a first pattern configured to form an antenna, one or more capacitive coupling structures, and/or one or more traces in the metal layer or the metal carrier, and (b) an optional second pattern to remove or disrupt the metal in a region of the metal layer or the metal carrier overlapping with the active device.
In some examples, when pressing the active device on the one or more substrates into the metal carrier, the stamping die contacts the substrate(s), and the active device contacts the metal carrier. In such examples, at least one of the active device and the metal carrier may include an insulating or dielectric layer that is between the active device and the metal carrier when the active device contacts the metal carrier.
In some embodiments, the method further comprises removing the one or more substrates from the active device during or after applying pressure and heat to the active device on the one or more substrates and the metal carrier. For example, the substrate(s) may include a release layer between the substrate(s) and the active device, or between adjacent layers of the substrate(s).
Attaching the IC with a relatively small coupling antenna (or other capacitive coupling structure) thereon to a target substrate with a relatively large antenna (or other capacitive coupling structure) thereon or therein may be easily integrated into a roll-to-roll process to enable high production throughput. These and other advantages of the present invention will become readily apparent from the detailed description of various embodiments below.
Reference will now be made in detail to various embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the following embodiments, it will be understood that the descriptions are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents that may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be readily apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present invention.
The technical proposal(s) of embodiments of the present invention will be fully and clearly described in conjunction with the drawings in the following embodiments. It will be understood that the descriptions are not intended to limit the invention to these embodiments. Based on the described embodiments of the present invention, other embodiments can be obtained by one skilled in the art without creative contribution and are in the scope of legal protection given to the present invention.
Furthermore, all characteristics, measures or processes disclosed in this document, except characteristics and/or processes that are mutually exclusive, can be combined in any manner and in any combination possible. Any characteristic disclosed in the present specification, claims, Abstract and Figures can be replaced by other equivalent characteristics or characteristics with similar objectives, purposes and/or functions, unless specified otherwise.
Stamping is an established film attach process in large-area device/substrate manufacturing. In banknote manufacturing, for example, a foil is stamped at a certain pressure and a certain temperature on a target substrate in the security foil attach process. For example, “hot stamping” typically includes a pressure of around 80-100 psi, at a temperature of approximately 120° C. In the same way, flexible integrated circuits can be placed onto a foil and stamped on a target substrate at high speeds.
Low assembly throughput causes manufacturing costs to rise. AoC allows for rough placement (e.g., placement within a relatively large area, and/or in a location with relatively large error margins) on a primary antenna surface, allowing more options for high speed die placement. Similar results can be expected for devices (e.g., ICs) that are capacitively coupled to traces on a substrate. Stamping is a well-established, high-speed process that is compatible with roll-to-roll (R2R) manufacturing and that can leverage the use of stainless steel (SS) as a substrate, as the device (e.g., the IC and/or SS substrate) can handle stamping forces much higher than silicon devices can.
Additionally, recent tests have shown that by thinning the device (e.g., metal substrate) down, pressures as high as 3.5 N/mm2 can be achieved (e.g., used to attach a device by stamping). For example, force tests have shown that a 5 μm-thick stainless steel sample can survive a force of 3.5 N/mm2, and functionality has been demonstrated for ICs on such thin substrates. This level of robustness cannot be achieved by traditional silicon ICs. This method (i.e., “hot stamping”) additionally allows the product to be very thin and flexible. For example, extreme bending tests have been performed on a 10 μm-thick stainless steel sample, and bending radii of as small as 125 μm have been observed. In combination with AoC or a similar capacitive coupling method, electronic circuits can easily be integrated with an antenna or other devices on another substrate in a “hot stamping” foil attach process.
Integrating flexible IC devices in an established roll-to-roll (R2R) manufacturing and/or stamping process allows for efficient use of existing infrastructure (e.g., equipment sets, clean room environments, etc.) and maximum die attach throughput. Using Antenna-on-Chip or similar capacitive coupling processing allows the coarse placement of the die on the target substrate. In the examples shown in
The carrier film 110, release coating 120, color film or coating 130, and size coating 140 are conventional, and are conventionally and sequentially deposited or otherwise placed on the preceding structure to form the film stack 100-A. The active devices 150 may be formed on the film stack 100-A or placed on the film stack 100-A (e.g., by a low-resolution pick-and-place process, roll-to-roll processing, or using surface mount technology; see, e.g., U.S. Pat. No. 9,004,366 [Atty. Docket No. IDR2272] and U.S. patent application Ser. No. 16/078,887, filed Aug. 22, 2018 [Atty. Docket No. IDR4720US], the relevant portions of each of which are incorporated herein by reference).
The material 160 to be hot stamped may comprise a metal sheet or foil. For example, the metal sheet or foil may comprise stainless steel, aluminum, copper, titanium or molybdenum. The metal sheet or foil may have a thickness of from about 3 μm to about 1000 μm (e.g., 3 μm to 200 μm, 5 to 100 μm, or any other value or range of values therein). The material 160 may have essentially any shape, such as square, circular, oval, oblong, etc. Alternatively, the material 160 may have a predetermined irregular and/or patterned shape. In some embodiments, the material 160 may be square or rectangular, and optionally separated from a sheet of x-by-y square or rectangular units, or an x-unit wide roll, where each unit represents an individual, separable substrate for a single integrated circuit (e.g., display device, solar cell, identification tag, etc.). The foil may be (or be used to form) an antenna or to connect the active device 150 to one or more other devices, such as a display, a sensor, or one or more batteries. The material 160 is generally conventionally cleaned prior to hot stamping.
The film stacks that may be used in hot foil stamping are not limited to that shown in
The present “hot stamping” process may include four subprocesses: Thinning, dicing, separating and attaching. Each of these subprocesses will be discussed in greater detail below.
Preparing the IC for Greater Flexibility (Thinning)
An IC built on a 75 μm-thick stainless steel substrate has a limited bending radius (e.g., about 15 mm), below which the IC fails. To reduce this bending radius, the substrate should have a higher degree of flexibility. One way to do this is by thinning the metal substrate 200 as shown in
In further embodiments, the carrier and/or protective film with the active devices 210 and the thinned metal substrate 205 thereon can be used in a “hot stamping”-based IC attach process. For example, the antenna-on-chip process is known, and one may assume that the coupling antenna is already present on the front (IC) side of the active devices 210, although the coupling antenna may be formed or added later (e.g., after the IC attach process). Herein, the term “active devices” includes an IC and optionally a coupling antenna or one or more metal pads adjacent to a peripheral edge of the IC (which can be used for capacitive coupling to one or more traces on another substrate). Alternatively, the active device includes an IC and one or more bonding or other electrical connection pads thereon, having dimensions sufficiently large to enable low-resolution placement of the active device onto a carrier film or foil.
Dicing
There are three options for dicing after thinning the devices. For example,
The first option (“300-1” in
The second option (“300-2” in
The third option (“300-3” in
A combination of options can also be used (e.g., patterning the thinned substrate 330 and the protective/carrier film 320). The dies 350 may be in an array (see, e.g.,
Dicing can be performed by any known mechanical, thermal, optical, or chemical method, such as laser scribing, saw-dicing, punch-dicing, etching, laser ablating, etc.
The first embodiment of the second option 300-2 (dicing the thinned metal foil substrate 330 and active devices 310, but maintaining a continuous protective/carrier film 320) can also be achieved by dicing the active devices 310 prior to placing the protective/carrier film 320 over/on the active devices 310. Dicing the active devices 310 on the metal substrate 330 can be terminated inside or at the surface of the substrate 330. When the substrate 330 is partially diced (i.e., dicing is terminated inside the substrate 330), subsequent thinning can then separate the substrate 330 (e.g., after placement on or affixing to the protective/carrier film 320).
Separating
Before the dies 350 are transferred to a subsequent carrier foil, they are separated to allow the placement of the die 350 on or at a predetermined position (e.g., on a product surface). When a partial cut is made in a dicing lane (e.g., options 300-2 and 300-3 discussed above with respect to
In a straightforward example shown in
In the R2R process, when the roll of diced dies 350 and the roll of foil 400 are run at different speeds (e.g., the roll of foil 400 proceeds at a faster rate than the roll of diced dies 350), column pitch separation (i.e., an increased spacing 414 between dies 350 in a column of the array 360) can be achieved.
After separation, the dies 350 proceed on divided foil rolls 405a-e. Each divided roll 405a-e represents one column of the array 360. The divided foil rolls 405a-e may advance on separate rollers 420 in parallel (e.g., one set of rollers 420 per divided foil roll 405). Adherence of the dies 350 (e.g., to the foil roll 400) may be improved by the present separation process.
Another method exemplified in
As shown in
Another approach to separating the dies 350 is shown in
Attach (Stamping)
Stamping of a Carrier Film onto the Target Substrate
After the die 350 (in which the active device 310 may include a coupling antenna) on the protective/carrier film 320 is placed on the metal foil carrier 400 as shown in
The metal carrier foil 400 may contain a primary antenna or capacitive coupling structure (e.g., a metal pad or trace) thereon or therein. The primary antenna or capacitive coupling structure may be placed on the metal carrier foil 400 prior to hot stamping, formed during hot stamping (see “Stamping both active device and primary antenna/capacitive coupling structure at the same time” below), or after the hot stamping process, since the primary antenna/capacitive coupling structure fabrication and/or attachment process is not necessarily coupled to the manufacturing process(es) for the rest of the device.
Stamping of a Carrier Film onto the Target Substrate without Protective Film Removal
As shown in
Stamping without a Carrier Film
In the embodiment shown in
As is shown in
For example, the stamping die 175 can include at least two patterns, an antenna pattern 172 and a raster pattern 174. Referring now to
The patterns in the stamping die are by no means limited to those shown in
In another alternative (e.g., in which the carrier 100-B does not include a metal layer 180, similar to carrier 100-A in
In general, in scenarios where a stainless steel or other metal substrate remains on or under (i.e., overlapping with) the active device 150, the metal foil substrate 160 may be patterned in a manner that allows the electromagnetic signal to efficiently pass through (such as the cage structure disclosed in U.S. patent application Ser. No. 16/790,494 [Attorney Docket No. IDR5120], filed Feb. 13, 2020, the relevant portions of which are incorporated herein by reference) in applications where wireless signals need to be transferred. This substrate patterning may be performed at the same time as dicing (which may be conducted by patterning dicing lanes in the substrate). Substrate patterning may not be necessary if the substrate has been thinned down to a level providing a low conductivity, or in the case where the coupling antenna communicates with the primary antenna without the metal substrate in between.
The present invention is not limited to wireless communication devices (e.g., devices including one or more antennas, such as NFC tags, RF and RFID tags, HF, UHF and VHF devices, etc.). The system (e.g., the die 350 or device including the die 350 on the [patterned] metal foil carrier 400) can also include other types of electronics, such as sensors, batteries, displays and actuators (e.g., on/off switch, display selector, etc.).
The protective film 320 may not necessarily be a continuous film, but could also be patterned (e.g., perforated) in the dicing lanes to skip an additional patterning step in the dicing process. This can be done, for instance, by screen printing a passivating film, or patterning a photoresist layer.
Furthermore, the dies do not necessarily have to be thin. Hot stamping is not limited to devices under a certain maximum thickness.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.
The present application claims priority to U.S. Provisional Pat. Appl. No. 62/811,481, filed Feb. 27, 2019 (Atty. Docket No. IDR5260-PR), incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62811481 | Feb 2019 | US |
