Apparatus and methods for high-speed assembly of electronic devices

Abstract

Methods and apparatus for supporting the assembly of electronic devices comprising integrated circuits (ICs), and in particular, but not exclusively to, the assembly of an IC formed on a flexible substrate (flexible ICs) together with corresponding electronic circuitry (e.g., forming an antenna) to form an electronic device, such as a radio-frequency identification (RFID) inlays or tags.

Description

Apparatus and Methods for High-speed Assembly of Electronic Devices

[0001] The present invention relates to methods and apparatus for supporting the assembly of electronic devices comprising integrated circuits (ICs), and in particular, but not exclusively to, the assembly of an IC formed on a flexible substrate (flexible ICs) together with corresponding electronic circuitry (e.g., forming an antenna) to form an electronic device, such as a radio-frequency identification (RFID) inlay or tag.

[0002] Historically, during the manufacture of ICs, a wafer consisting of a thin layer of semiconductor material such as crystalline Silicon (c-Si) or Gallium arsenide (GaAs) is provided which serves as a substrate for supporting microelectronics that form the ICs. Such wafers typically have an extreme level of purity and are formed in a single crystal structure.

[0003] During the manufacturing process the ICs may be built up on the wafer. For example, devices such as diodes, transistors, capacitors, and resistors, can be built up by forming p-type and n-type regions, at appropriate locations, in the semiconductor substrate using appropriate doping, and by building up one or more layers of insulating and / or conducting material using appropriate fabrication processes. The location of the n-type and p-type regions and the pattern of insulating and / or conducting material in each layer defining the devices, and the interconnectivity between them, is typically defined using appropriate photolithographic processes.

[0004] Once built up, each individual IC (known as a ‘die’) is separated from the other ICs on the wafer, which typically involves slicing the ICs apart in a process known as ‘singulation’ or ‘dicing’. Singulation of the ICs is typically performed by dicing the substrate along straight lines (known as scribe lines) between the ICs, typically using a laser or abrasive water jet. During handling of the resulting ‘singulated’ IC, a single die may be picked up using an appropriate pick tool and either placed directly onto a support having corresponding contact pads during the formation of an electronic circuit or, if orientation flipping is required, placed onto another pick tool before placement onto the support having corresponding contact pads.

[0005] Whilst fabrication on crystalline semiconductor substrates is widespread, fabrication of ICs may be carried out on other substrate materials including flexible insulating substrates. For example, it is known to use a flexible substrate formed of,for example, a thin, heat-resistant material such as polymers to manufacture flexible ICs. Where the substrate is flexible, a rigid carrier is typically used to support the flexible substrate during the subsequent manufacture of electronic devices on that flexible substrate to form the flexible IC, for example using manufacturing processes similar to those described above for a crystalline semiconductor wafer, albeit adapted to be suitable to the flexible substrate being used (e.g., using lower temperatures suitable for polymer substrates or the like).

[0006] Over the past decade there has been a large increase in the demand for flexible IC based electronic devices, especially for electronic devices such as RFID inlays or tags that typically incorporate simple two terminal flexible ICs. This increase in demand has been driven, in particular, by the increasing and varied applications of RFID tags in fields as diverse as medical devices, product packaging, asset tracking, security, logistics, etc.

[0007] As with crystalline semiconductor-based ICs, flexible ICs, once fabricated, are typically separated (or diced) into individual dies for subsequent removal and integration into an end product such as an RFID tag, or the like. However, the assembly of electronic devices comprising one or more flexible ICs (such as RFID inlays or tags) at the rates required to mass produce the electronic devices in sufficient volumes, and at a low enough cost, to meet modern demands, is challenging.

[0008] Whilst high-speed assembly processes and equipment have been developed in an effort to support the high demand for low-cost electronic devices comprising flexible ICs in sufficiently large quantities, currently available equipment is expensive and processes using such equipment are beginning to reach their throughput limits. For example, in the case of manufacturing RFID tags with flexible ICs, the use of leading assembly machines can cost in the order of millions of dollars, and typically achieve assembly throughputs of between 12,000 units-per-hour (UPH) and 80,000 UPH. Whilst cheaper alternatives are available, their throughput is lower. This limits the economic applicability of RFID for very low-cost items.

[0009] Accordingly, despite the advances in assembly technology, there is an increasing need for new processes / equipment that offer increases in assembly throughput (e.g., to greater than 100,000 UPH) whilst, at the same time providing improved efficiencies and hence reduced cost. It will be appreciated that, in the context of flexible IC based electronic devices, the development of any newprocesses / equipment needs to take account of the materials from which the inlays or tags are formed and the equipment that may be used to ultimately assemble them.

[0010] It is an objective of the present invention to provide methods and apparatus that at least partially contribute to the above need.

[0011] In one example described herein there is disclosed, a method of forming an assembly carrier holding a package of flexible material carrying multiple interposers for subsequent assembly into electronic devices, the method comprising: providing multiple integrated circuit (IC) dies, wherein each IC die is a component that, when assembled with corresponding electronic circuitry, forms at least a part of a respective electronic device; respectively transferring each IC die of at least a subset of the multiple IC dies to a corresponding section of an elongate flexible carrier, each section being configured for forming a respective interposer; and packaging the flexible carrier to which the IC dies have been transferred into at least one assembly carrier for subsequent use in assembly of each interposer carrying a corresponding IC die with corresponding electronic circuitry to form at least part of a respective electronic device.

[0012] Each IC die may be a flexible IC die. The flexible IC dies may be provided on a rigid carrier.

[0013] The packaging may comprise winding the flexible carrier to which the IC dies have been transferred into at least one roll or reel held by the at least one assembly carrier.

[0014] The method may further comprise laminating the flexible carrier with another layer to encapsulate each IC die transferred to the flexible carrier, prior to packaging the flexible carrier to which the IC dies have been transferred into the at least one assembly carrier.

[0015] The multiple IC dies may be provided as part of a wafer (e.g., a flexible wafer) on which the IC dies were fabricated. The method may further comprise singulating at least a subset of the multiple IC dies into individual dies prior to the transferring. The method may further comprise separating at least a subset of the multiple IC dies into groups (e.g., columns, subarrays, or rows) of individual IC dies prior to the transferring. The multiple IC dies may be provided on an initial carrier, optionally a wafer frame.

[0016] The transferring may comprise respectively transferring each IC die to the flexible carrier individually. The transferring may comprise transferring a plurality of IC dies to the flexible carrier together as a one-dimensional array. The transferringmay comprise transferring each IC die of at least a subset of the multiple IC dies to a temporary carrier, and then transferring each IC die of at least a subset of the multiple IC dies from the temporary carrier to the corresponding section of the flexible carrier.

[0017] The method may further comprise singulating at least a subset of the multiple integrated circuit (IC) dies into individual dies on the temporary carrier. The method may further comprise separating at least a subset of the multiple integrated circuit (IC) dies into groups (e.g., columns, subarrays, or rows) of individual IC dies on the temporary carrier.

[0018] The transferring may comprise respectively transferring each IC die to the temporary carrier individually. The transferring may comprise transferring a plurality of IC dies to the temporary carrier together as a one-dimensional array. The transferring may comprise transferring all, or a subset of, the multiple IC dies to the temporary carrier together as a two-dimensional array.

[0019] The temporary carrier may have an IC receiving surface to which at least a subset of the multiple IC dies are transferred prior to transfer to the corresponding section of the flexible carrier, the IC surface being a curved surface during at least the transfer of each IC die of at least a subset of the multiple IC dies from the temporary carrier to the corresponding section of the flexible carrier. The temporary carrier may be configured for picking up each IC using a vacuum as part of the transferring. The temporary carrier may be configured for picking up each IC using adhesion as part of the transferring. The temporary carrier may be rigid. The temporary carrier may be flexible.

[0020] The transferring of each IC die of at least a subset of the multiple IC dies to the corresponding section of the flexible carrier may be configured to form a single one-dimensional array of ICs on the flexible carrier. The transferring of each IC die of at least a subset of the multiple IC dies to the corresponding section of the flexible carrier may be configured to form a two-dimensional array of ICs, comprising a plurality of one-dimensional arrays of ICs on the flexible carrier.

[0021] The method may further comprise splitting the flexible carrier into a plurality of narrower flexible carrier portions, each narrower flexible carrier portion carrying one of the one-dimensional arrays of ICs. The packaging of the flexible carrier may comprise winding each narrower flexible carrier portion into a corresponding roll or reel for subsequent use in assembly of each interposer carrying a corresponding ICdie, with corresponding electronic circuitry, to form at least part of a respective electronic device.

[0022] The method may further comprise respectively forming, prior to the packaging, at least one cut through the flexible carrier at least partially around each IC of at least a subset of the ICs transferred to the flexible carrier, to define a discrete interposer carrying that IC. Each IC may have a plurality of connection terminals and a conductive pattern may be provided on the flexible carrier for facilitating electrical connection to each terminal of each IC transferred to the flexible carrier. The conductive pattern may comprise at least two parallel conductive regions extending longitudinally along the intermediate carrier through each section to which a corresponding IC is transferred. The conductive pattern may respectively comprise a plurality of discrete conductive regions, on each section of the flexible carrier to which a corresponding IC is transferred, for facilitating respective electrical connection to each terminal of that corresponding IC.

[0023] The method may further comprise forming a conductive pattern (e.g., comprising one or more conductive regions or features) on each IC of at least a subset of the multiple ICs, prior to that IC being transferred to the flexible carrier, for facilitating electrical connection to each terminal of that IC.

[0024] A method as claimed in any preceding claim further comprising bonding, to the flexible carrier, each IC transferred to the flexible carrier. The bonding may be performed using at least one of: an anisotropic conductive adhesive (ACA), paste (ACP) or film (ACF), ultrasonic welding, laser welding, spot welding, punch-through connections, or over-edge printing. Each IC die may be provided with contact pads with material puncturing features (e.g., spikes) formed thereon. The bonding may be performed by puncturing the flexible carrier with the material puncturing features of each IC die.

[0025] In one example described herein there is disclosed, a method of assembling electronic devices, the method comprising: providing at least one assembly carrier holding a package of flexible material, carrying multiple interposers, formed in accordance with a method as described above, each interposer carrying a corresponding IC die with a plurality of terminals; and assembling each interposer of at least a subset of the multiple interposers with respective electronic circuitry supported by a substrate, by electrically connecting the plurality of terminals of the corresponding IC die carried by that interposer to that electronic circuitry, to form a corresponding electronic device.

[0026] In one example described herein there is disclosed, a method of assembling electronic devices, carrying multiple interposers the method comprising: providing at least one assembly carrier holding a package of flexible material, each interposer carrying a corresponding IC die with a plurality of terminals; and assembling each interposer of at least a subset of the multiple interposers with respective electronic circuitry supported by a substrate, by electrically connecting the plurality of terminals of the corresponding IC die carried by that interposer to that electronic circuitry, to form a corresponding electronic device.

[0027] Each interposer may be connected to the flexible carrier by at least one frangible connection, and the assembling of each interposer with the corresponding electronic circuitry may comprise respectively breaking the at least one frangible connection of that interposer, to remove that interposer from the flexible carrier. The electrically connecting the plurality of terminals of each IC die carried by a respective interposer, to the corresponding electronic circuitry, may comprise respectively forming an electrical connection between each terminal and the corresponding electronic circuitry indirectly via a corresponding electrically conductive region provided on the respective interposer. The electrically connecting may be performed using at least one of: an anisotropic conductive adhesive (ACP), paste (ACP) or film (ACF), ultrasonic welding, laser welding, spot welding, or punch-through connections. The electrically connecting may be performed using ultrasonic welding and comprises forming, via the ultrasonic welding, defects in the flexible material supporting the interposer and / or a substrate supporting the electric circuitry to electrically connect the plurality of terminals of the corresponding IC die with the corresponding electronic circuitry.

[0028] The assembling may comprise respectively assembling each interposer with the corresponding electronic circuitry in: a first orientation in which an electrical contact side of the interposer faces an electrical contact side of the electronic circuitry; a second orientation in which the electrical contact side of the interposer faces a rear side of the substrate opposite a front side of the substrate that supports the electrical circuitry; a third orientation wherein the electrical contact side of the electronic circuitry faces a rear side of the interposer opposite the electrical contact side of the interposer; or a fourth orientation wherein the rear side of the interposer faces the rear side of the substrate supporting the electrical circuitry.

[0029] The assembling may comprise respectively assembling each interposer with the corresponding electronic circuitry in an orientation in which an electrical contactside of the interposer faces an electrical contact side of the electronic circuitry, and an insulating layer is provided between the electrical circuitry and the at least one interposer.

[0030] The electronic devices may be radio frequency identification (RFID) devices. The electrical circuitry may comprise an antenna.

[0031] In one example described herein there is disclosed, an electronic device formed using an assembly process according as summarised above.

[0032] In one example described herein there is disclosed, an assembly carrier holding a package of flexible material, carrying multiple interposers, each interposer carrying a corresponding IC die, formed using a method as summarised above.

[0033] In one example described herein there is disclosed, a radio frequency identification (RFID) device comprising an interposer, formed of a flexible material, and carrying at least one flexible IC die with a plurality of terminals, the plurality of terminals being electrically connected to an antenna to form the RFID device.

[0034] In one example described herein there is disclosed, an assembly carrier holding a package of flexible material, carrying multiple interposers, each interposer carrying a corresponding flexible IC die with a plurality of terminals, each terminal of a given flexible IC die being electrically connected to a respective electrically conductive region provided on the corresponding interposer.Brief Description of Figures

[0035] Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which:Figures 1a and 1 b illustrate a procedure for forming strips of flexible ICs on ‘straplike’ interposers;Figures 2 illustrates an example procedure for assembling electronic devices from an intermediate flexible carrier that carries interposers to which flexible ICs have been attached, e.g., in accordance with the procedure described shown in Figures 1a and 1 b.Figures 3a and 3b illustrate a method of manufacturing a plurality of flexible ICs on a rigid carrier;Figures 4a and 4b illustrate different methods for removing a plurality of flexible ICs from a rigid carrier on which they are formed ;Figure 5a and 5b illustrates a method of transferring a plurality of flexible ICs to a temporary carrier;Figure 6 illustrates a method of transferring a plurality of flexible ICs from a temporary carrier to corresponding interposer sections of an intermediate flexible carrier;Figure 7 illustrates a section of an intermediate flexible carrier to which flexible ICs has been transferred;Figure 8 illustrates another method of transferring a plurality of flexible ICs from a temporary carrier to an intermediate flexible carrier;Figure 9 illustrates singulation of a plurality of interposers carried by an intermediate flexible carrier, each interposer carrying a respective discrete flexible IC;Figure 10 illustrates a method of slicing a wide band-like intermediate flexible carrier that carries a 2D array of flexible ICs into a plurality of narrower intermediate flexible carriers that each carry a 1 D array of flexible ICs;Figure 11 illustrates a method of assembly for assembling interposers carried by an intermediate flexible carrier onto electronic circuitry of an electronic device; andFigure 12a to 12d each illustrates a different relative interposer / electronic circuitry orientation that may be used during assembly of interposers carried by an intermediate flexible carrier onto electronic circuitry of an electronic device.Overview

[0036] A procedure for assembling flexible ICs together, with associated electronic circuitry (e.g., an antenna or the like), to form an electronic device (e.g., an RFID inlay, tag, label or the like), will now be described in overview.

[0037] It will be appreciated that whilst the procedure is described primarily with reference to RFI D inlays or tags, the procedure is more widely applicable to any high- volume flexible IC based electronic device. Moreover, as those skilled in the art would understand, whilst the illustrated examples involve the assembly of simple two- contact flexible ICs to relatively simple electronic circuitry in the form of an antenna,the procedure can be adapted to assembly of flexible ICs, having a larger number of contacts, and / or to more complex electronic circuitry.

[0038] Moreover, whilst the procedure is described with reference to flexible ICs, the procedure could be adapted to ICs fabricated on a rigid (insulating or semiconductor) substrate.

[0039] In essence, the procedure breaks down in to two main stages: a. Stage 1 : T ransfer of the flexible ICs onto corresponding interposers (or ‘straps’), where each interposer is formed of a respective section of an intermediate flexible carrier in the form of a flexible ribbon-like structure, which is subsequently wound into a dense reel / roll / tape format to package the intermediate flexible carrier and thus form an assembly carrier for subsequent use in an assembly process; and b. Stage 2: Subsequent separation of the interposers, carrying the flexible ICs, from the strap, and respective attachment of each separated interposer to electronic circuitry (e.g., an antenna or the like), to form a corresponding electronic device (e.g., an inlay, such as an RFID inlay, or the like).

[0040] It will be appreciated that each of these stages (and possibly intermediate parts of each stage) may be performed at different locations by different entities. For example, the first stage may be performed by the manufacturer of the flexible ICs (e.g., at a site where the ICs are manufactured or some other site), whereas the second stage may be performed, potentially a significant time later, by an inlay assembler or label convertor and at a different site. Nevertheless, the first stage may also be performed by an intermediate entity such as a specialist assembler, or the like, who receives wafers, in which the flexible ICs are formed, on rigid carriers or wafer frames from the manufacturer of the flexible ICs.

[0041] Each of these stages will now be briefly introduced, by way of example only with reference to Figures 1a, 1 b and 2, before a more detailed description is provided with reference to Figures 3 to 12.Stage 1: Transfer of the flexible ICs onto corresponding interposers

[0042] Figure 1 a and 1 b illustrate an example procedure for forming strips of flexible ICs on ‘strap-like’ interposers for subsequent storage and / or usage in an electronic device assembly procedure.

[0043] As seen in Figure 1a, at step 1 of the procedure, prior to the transfer of the flexible ICs onto the interposers, the flexible ICs 130 are first manufactured on a flexible substrate 120 (e.g., a polymer-based flexible substrate, or the like) that is supported by a rigid carrier 110 (e.g., a glass carrier, a silicon wafer, a wafer frame, or the like).

[0044] At step 2, once formed, the flexible ICs 130 are lifted directly off the rigid carrier 110 in one of multiple possible ways. For example: a. A whole flexible substrate (wafer) of flexible ICs may be lifted off the rigid carrier in one piece (as shown in Figure 4a); b. Each individual flexible IC of a wafer may be respectively singulated (diced) and then lifted off the rigid carrier individually (or in groups of singulated flexible ICs); c. Whole rows (or columns) of flexible ICs ( / .e., strips of flexible ICs) may be separated and respectively lifted off the rigid carrier as a strip (as shown in Figure 4b); or d. Some other grouping of flexible ICs may be separated and lifted off the rigid carrier.

[0045] It will be appreciated that, where necessary, an appropriate release step may also need to be carried out prior to lifting flexible ICs 130 off the rigid carrier 110 (e.g., by heating a release layer provided between the flexible ICs and the rigid carrier using a suitable form of irradiation).

[0046] Lifting of the flexible ICs 130 off the rigid carrier 110 may be carried out using an appropriate pick tool, or alternatively, may be carried out using another tool (e.g., in the form of a porous vacuum chuck, or the like) that acts as a temporary carrier 210 from which the flexible ICs 130 will be transferred to the interposers / straps.

[0047] At step 3, the lifted flexible ICs 130 are transferred to corresponding interposers, where each interposer is formed of a respective section of an intermediate flexible carrier 240. In this example, the flexible ICs 130 are transferred from a temporary carrier 210, but it will be appreciated that the procedure could beadapted for transfer of the flexible ICs 130 directly from the original rigid carrier on which the flexible ICs 130 were first formed.

[0048] This transfer may be done in a number of different ways. For example, as seen in Figure 1a, step 3, the illustrated temporary carrier 210 may be a cylindrical temporary carrier 210 that is configured to present a generally cylindrical IC surface ( / .e., a surface of the temporary carrier to which those flexible ICs 130 were transferred in step 2). It will be appreciated that the cylindrical temporary carrier 210 may be configured to present the generally cylindrical IC surface by transferring the flexible ICs 130 to a flexible temporary carrier and then mounting the flexible temporary carrier on a generally cylindrical stage, or by transferring the flexible ICs 130 to a rigid temporary carrier that is already cylindrical.

[0049] The flexible ICs 130 may then be transferred from the IC surface of that temporary carrier 210 to the intermediate flexible carrier 240.

[0050] The cylindrical temporary carrier 210, in this example, is arranged in a first configuration in which it is rotatable (in, and opposed to, the rotational direction ‘B’) about a central longitudinal axis (parallel to the y-axis depicted in the illustration), and optionally configured for controlled (e.g., indexed) movement linearly in other directions corresponding to a standard cartesian coordinate system (e.g., along the x-, y- and / or z- axes depicted). It will be appreciated that the cylindrical temporary carrier 210 may be arranged in this first configuration when picking up the flexible ICs 130 in step 2 or may be moved to this first configuration after the flexible ICs 130 have been attached to its IC surface in step 2.

[0051] In this first configuration, the temporary carrier 210 is rotatable (and optionally linearly movable as appropriate) to iteratively locate the flexible ICs 130 at an appropriate position in which each flexible IC 130 can be removed from the IC surface of the temporary carrier 210 and respectively transferred to a corresponding interposer (‘strap’) section on the intermediate flexible carrier 240. To facilitate this an appropriate pick tool 220 (as seen in insert (A) of Figure 1a, step 3) may be used to transfer the flexible ICs 130 directly from the cylindrical temporary carrier 210 to a corresponding interposer section on the intermediate flexible carrier 240.

[0052] In the illustrated example, the pick tool 220 is a generally cylindrical pick tool that is configured for rotation (as indicated by arrow ‘C’) about a central longitudinal axis (parallel to the y-axis depicted in the illustration), and optionally linearly in other directions corresponding to the standard cartesian coordinate system. The cylindrical pick tool 220 is configured: to rotate (and optionally move linearly as appropriate) toa position in which it can pick one or more flexible ICs 130 from the IC surface of the temporary carrier 210; and, once the flexible IC(s) have been picked up, to rotate (and optionally move linearly as appropriate) to a position in which it can respectively place each picked-up flexible IC on a corresponding interposer on the intermediate flexible carrier 240.

[0053] In other examples, one or more flexible ICs 130 may be transferred from the temporary carrier 210 onto the intermediate flexible carrier 240 without use of a pick tool 220. For example, one or more interposers on the intermediate flexible carrier 240 may be pressed onto one or more corresponding flexible ICs 130, which may then be released from the temporary carrier 210. This pressing may be accomplished, for example, using a thermode, roller or other structure, which may additionally be heated to initiate bonding between the flexible IC(s) 130 and the interposers.

[0054] It will be appreciated that the intermediate flexible carrier 240 may be preconfigured with appropriate electrical contact regions (e.g., pairs of conductive features) for forming a connection to corresponding connections of the flexible ICs 130. Nevertheless, it will be appreciated that the flexible ICs 130 themselves may be provided with electrical contact regions or features (e.g., legs, bumps, or the like) that are bonded to the corresponding connections of the flexible ICs 130 in advance (e.g., either prior to removal of the flexible ICs 130 from the rigid carrier at step 1 , or after their transfer to the temporary carrier in step 2).

[0055] As the flexible ICs 130 are transferred to the interposer section on intermediate flexible carrier 240, the intermediate flexible carrier 240 is drawn, by an appropriate roller system, past the pick tool 220 for ultimate rolling into a tight / dense tape / roll format into an assembly carrier for storage and / or transfer to an assembly site.

[0056] It will be appreciated that once the flexible ICs 130 have been deposited on the intermediate flexible carrier 240 carrying the interposer in accordance with any of the approaches described above, they may be bonded to the interposer appropriately. For example, an anisotropic conductive adhesive (ACA), such as an anisotropic conductive paste (ACP) (or an anisotropic conductive film (ACF)) may be provided on the interposer (or the ICs 130) and may be cured using a conventional thermode or an in-line heated thermode roller that collects and rolls the intermediate flexible carrier 240 after the flexible ICs 130 have been transferred to it, so as to bond the flexible ICs 130 to the interposer. The use of an in-line heated thermode roller isparticularly beneficial as it facilitates higher throughput, including rolling the intermediate flexible carrier 240 carrying the interposer into the tight / dense roll / tape format for use in a subsequent assembly process. Nevertheless, it will be appreciated that there are a number of alternatives to adhesive-based bonding as will be described later.

[0057] It will be appreciated that the intermediate flexible carrier 240 may be a narrow ribbon-like strip that carries a 1 D array of flexible ICs 130, or the intermediate flexible carrier 240 may be a wider band-like strip that carries a 2D array of flexible ICs 130 (i.e., a plurality of parallel 1 D arrays of flexible ICs 130). In the latter case, step 4 may be performed, in which a wider band-like intermediate flexible carrier 240’ carrying the interposers, to which the flexible ICs 130 have been transferred, may be sliced into multiple narrower intermediate flexible carriers 240 in the form of ribbonlike strips, each strip comprising a 1 D array of flexible ICs 130. Each of these strips may then be rolled into a respective the tight / dense roll / tape. For example, as shown in Figure 1 b, a roll of a wider band-like intermediate flexible carrier 240’ carrying a 2D array of flexible ICs 130 (e.g., formed using the procedures described above) may be unwound, split into the separate narrower intermediate flexible carriers 240 comprising ribbon-like strips that each carry a 1 D array of flexible ICs 130, and rewound into individual rolls / reels each representing a respective package of intermediate flexible carrier held by a corresponding assembly carrier. In the illustrated example, the wider band-like intermediate flexible carrier 240’ is separated into six parallel 1 D strips 240 but it will be appreciated that a similar procedure could be used for any appropriate number of strips.Attachment of interposers to antennas, forming inlays or tags

[0058] Figure 2 illustrates an example procedure for assembling electronic devices (e.g., RFID inlays or tags) from an intermediate flexible carrier 240 that carries interposers to which flexible ICs have been attached (e.g., formed in accordance with a procedure described with reference to Figures 1a and 1 b).

[0059] This procedure is effectively carried out as a fifth step (step 5) of the complete two stage procedure, although it will be appreciated that step 5 may be completed by a different entity at a different site.

[0060] At step 5, an assembly carrier comprising a roll / reel of the intermediate flexible carrier 240, formed using the procedure shown in Figures 1a and 1 b, may be unrolled and the flexible ICs 130 provided on the roll individually attached tocorresponding electronic circuitry (e.g., antennas) to form the electronic devices (e.g., RFID inlays or tags). Although inductive antennas are illustrated in Figure 2, the methods and materials described herein are applicable to all types of antennas, including for use at UHF frequencies, and all types of electronic circuits.

[0061] It will be appreciated that the electronic circuitry (e.g., antennas) may, for example, be provided: on discrete partially finished end products that will incorporate the electronic devices once assembly with the flexible ICs 130 has been completed; or on another roll / web / reel of partially finished electronic devices (e.g., comprising antennas formed on a flexible substrate or in adhesive labels, for attachment to products or the like once assembly with the flexible ICs 130 has been completed).

[0062] During step 5, the reel / web of partially finished electronic devices may be unrolled (or the separate partially finished end products may be provided) and the intermediate flexible carrier 240 may be unrolled to respectively place a corresponding interposer, with its corresponding flexible IC 130 in correct electrical contact with the electronic circuitry (e.g., antennas) of each partially completed electronic device. It will be appreciated that that each interposer may be detached from the intermediate flexible carrier 240 once it has been bonded to the respective electronic circuitry by pulling the intermediate flexible carrier 240 up and away from the electronic circuitry as the intermediate flexible carrier 240 is unrolled. Nevertheless, it will be appreciated that each interposer may be detached from the intermediate flexible carrier 240 before it has been bonded to the respective electronic circuitry. The detachment may be facilitated by the presence of partial cuts, around at least part of the perimeter of the region comprising the interposer (e.g., a rectangular region including both electrical contact regions in this example) to which each flexible IC 130 is connected, and which hence provide frangible break lines around the corresponding interposer that allows that interposer and flexible IC 130 to be pulled out of the intermediate flexible carrier 240. Such partial cuts may be made either as a part of Step 4, prior to winding the intermediate flexible carrier 240 onto reels, or as a part of Step 5, after unrolling the intermediate flexible carrier 240. It will be appreciated that each interposer may be bonded to the respective electronic circuitry through the deposition of anisotropic conductive paste (ACP), an anisotropic conductive film (ACF), or the like, on (appropriate parts of) the electronic circuitry followed by curing. Nevertheless, it will be appreciated that there are a number of alternatives to adhesive-based bonding as will be described later.

[0063] It will be appreciated that when placing interposer and flexible IC 130 onto the electronic circuitry, the interposer may be attached to the electronic circuitry in a variety of different orientations. For example, for each interposer and flexible IC 130: a. The interposer and corresponding electronic circuitry may be orientated such that the electrical contact area of the interposer and the electrical contact area of the electronic circuitry face one another; b. The interposer and corresponding electronic circuitry may be orientated such that the substrate of the interposer ( / .e., the side opposite the electrical contact area) and a substrate on which the electronic circuitry is provided face one another; c. The interposer and corresponding electronic circuitry may be orientated such that the substrate of the interposer ( / .e., the side opposite the electrical contact area) and the electrical contact area of the electronic circuitry face one another; or d. The interposer and corresponding electronic circuitry may be orientated such that the substrate on which the electronic circuitry is provided ( / .e., the side opposite the electrical contact area) faces the electrical contact area of the interposer.

[0064] It will be appreciated that, beneficially, the assembly procedures introduced above, represent an assembly technology that allows for the assembly of low-cost, high-volume, electronic devices such as, for example, RFID inlays or the like, in a manner that is compatible with machinery used by packaging manufacturers or label convertors for example, or by manufacturers of consumer goods, food or beverage products, textiles and the like who use very high throughput processes. This beneficially allows significant expansion in the capacity of the resulting assembly base compared to existing technologies that were typically adapted from those originally developed to meet the more stringent constraints imposed by crystalline semiconductor substrates. Moreover, as ultra-high throughput manufacturers typically employ relatively low-cost equipment (compared to existing RFID inlay assembly equipment) to print, wind / unwind / rewind, cut, stamp, and otherwise manufacture rolls (or reels) of products at enormous speeds, the assembly procedures introduced above also have the potential to provide significant cost savings.

[0065] In summary, as a result of these technological benefits, the assembly procedures introduced above have the potential to (amongst other things): a. Support in-line assembly of low-cost, high-volume, electronic devices such as RFID inlays; b. Help to minimise barriers-to-entry to new entrants due to the relatively low capital investment required; c. Avoid a significant increase to bill of materials (BoM); d. Increase throughput to better match reel to reel processes and other ultra-high manufacturing speeds; e. Be compatible with a wide variety of substrates, including, for example, Biaxially oriented polypropylene film (BOPP), paper, and Polyethylene terephthalate (PET); and f. Be scalable for a step change in production capacity for items comprising electronic (e.g., RFID) devices.Formation of flexible ICs on ‘strap-like’ interposers

[0066] A more detailed description of stage 1 summarised above will now be described with reference to Figures 3-10.Provision of Flexible ICs on a Rigid Carrier

[0067] Figures 3a and 3b illustrate the initial steps in the method of manufacturing a plurality of flexible ICs on a rigid carrier 110. As shown in Figure 3a, a first step may comprise, by way of example only, providing an appropriate starting material upon which flexible ICs can be formed. For example, a rigid carrier 110 made of a rigid material may be provided upon which the material forming a flexible substrate 120 is deposited (e.g., to form a flexible pre-fabrication wafer for subsequent processing to form a wafer of completed ICs). Although a circular rigid carrier 110 is illustrated in Figures 3a and 3b, a plurality of flexible ICs may be formed on a rigid carrier of any suitable shape, for example a rectangular carrier similar to those used in display panel manufacture.

[0068] The rigid carrier 110 may, for example, be formed from a transparent material such as glass although it will be appreciated that the rigid carrier 110 may be formed of any other suitable flexible material, for example, polycarbonate, quartz,silicon, or any other known materials suitable for supporting the flexible substrate 120.

[0069] The flexible substrate 120 may, for example, comprise a flexible polymer such as polyimide, or some other suitable substrate material. For example, other polymer materials may comprise polymers selected from one or more of: polyethylene naphthalates, polyethylene terephthalates; polymethyl methacrylates; polycarbonates, polyvinyl alcohols, polyvinyl acetates, polyvinyl pyrrolidones, polyvinyl phenols, polyvinyl chlorides, polystyrenes, polyimides, polyamides (e.g. Nylon); poly(hydroxy ethers), polyurethanes, polycarbonates, polysulfones, parylenes, polyarylates, polyether ether ketones (PEEKs); acrylonitrile butadiene styrene (ABS), 1-Methoxy-2-propyl acetates, Benzocyclobutenes (BCB), polylactic acid (PLA), polyhydroxyalkanoates (PHAs), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT), cellulose polymers, or any other suitable polymer material.

[0070] The material forming the flexible substrate 120 may be deposited on the rigid carrier 110 using thin-film processes such as, for example: physical vapour deposition (e.g. sputter), chemical vapour deposition (e.g. plasma-enhanced chemical vapour deposition (PECVD)), vacuum deposition (e.g. thermal or electronbeam evaporation); coating (e.g. spin, dip, blade, bar, spray, or slot-die), printing (e.g. jet, gravure, offset, screen, or flexographic), pulsed-laser deposition (PLD), atomic layer deposition (ALD), lamination and / or any other suitable processes.

[0071] It will be appreciated that although most of the examples presented above involve a flexible substrate layer 120 made of a polymer, the substrate layer 120 is not restricted to being a polymer. The flexible substrate layer 120 may be formed from any other materials that provide suitable electrical, chemical, and / or structural properties. As such the substrate layer 120 may comprise materials selected from one or more of: flexible glass, polymer materials, metal oxide materials, resin materials, resist materials, foil materials, paper, insulator coated metals, or any other suitable material. It will be appreciated that the materials listed herein are only provided by way of example and are not an exhaustive list of possible materials that may be used for the substrate layer 120.

[0072] As shown in Figure 3b, in a second step, the method of manufacturing the plurality of flexible ICs on a rigid carrier 110 may comprise forming a plurality of flexible ICs 130 on the flexible substrate 120 on the carrier 110. For example, as those skilled in the art will be familiar with, the material forming each of one or morelayers forming the plurality of flexible ICs 130 may be respectively deposited onto the flexible substrate 120, patterned using conventional top-side photoresist-based lithography, and etched using a suitable etchant, to form the required IC structure. Alternatively, rear-side photoresist-based lithography processes or imprint lithography processes may be used, or any other appropriate patterning technique, such as printing, may be used. Alternatively, a crystalline or polycrystalline semiconductor IC may be formed in a separate process and subsequently embedded into the flexible substrate 120.Removal of Flexible ICs from Rigid Carrier

[0073] Following formation of the plurality of flexible ICs 130 on the flexible substrate 120, the flexible ICs 130 may be singulated for future removal from the rigid carrier 110. For example, each flexible IC 130 (known as a ‘die’) may be separated from other flexible ICs 130 on the rigid carrier 110 by dicing the flexible substrate 130 upon which they are formed, along straight lines (known as scribe lines) between the flexible ICs 130, typically using a laser, an abrasive water jet, a saw, or some other appropriate dicing procedure - this may be referred to as a fully singulated substrate of flexible ICs 130.

[0074] It will be appreciated that, where flexible ICs 130 are fully singulated, each flexible IC may be picked off the rigid carrier 110 one at a time for subsequent transfer to an intermediate flexible carrier 240 (either directly, or indirectly via one or more temporary carriers). Nevertheless, to speed up the transfer throughput, all ora subset of the flexible ICs 130 may be picked off the rigid carrier in parallel. For example, a subset of individual flexible ICs 130 may be peeled off where the subset are positioned at a common lateral (or longitudinal) spacing in a given row (or column), e.g., every 3rd or 4th flexible IC (simultaneously or sequentially). The spacing may be selected to suit a corresponding dimension (pitch) of the next step in the assembly process (e.g., the spacing between the centres of the interposers on the flexible carrier in longitudinal and / or transverse directions).

[0075] It will be appreciated that, rather than singulating individual flexible ICs 130, the whole flexible substrate 120 supporting the flexible ICs 130 may be lifted off (e.g., peeled off) the rigid carrier 110 (with or without a laser release step), as shown in Figure 4a.

[0076] Moreover, it will be appreciated that rather than singulating individual flexible ICs 130, or transferring the entire wafer of flexible ICs, strips or blocks of pluralflexible ICs 130 (e.g., entire rows or columns of the flexible ICs 130 fabricated on the flexible substrate 110) may be sliced along straight lines to form separated strips of flexible ICs 130. Each strip of flexible ICs 130 may then be peeled off the rigid carrier 110 one at a time, or in parallel at a lateral or longitudinal spacing, e.g., every 3rdor 4thstrip of flexible ICs (simultaneously or sequentially), to suit the pitch of the next step in the assembly process as shown in Figure 4b. For example, a roller could peel an individual strip of flexible ICs 130 from the rigid carrier 110, to leave a clear ‘lane’ on the carrier.

[0077] Where the whole flexible substrate 120 supporting the flexible ICs 130 is lifted off (e.g., peeled off) the rigid carrier 110, the flexible substrate 120 (wafer) of flexible ICs 130 may be transferred to a suitable temporary carrier where the flexible ICs 130 may then be singulated into individual flexible ICs 130, or separated into strips or blocks of flexible ICs 130. Similarly, where the strips or blocks of the flexible substrate 120 supporting rows, columns or arrays of the flexible ICs 130 are lifted off (e.g., peeled off) the rigid carrier 110, they may be transferred to a suitable temporary carrier where the flexible ICs 130 may then be singulated into individual flexible ICs 130.

[0078] Singulation I separation of the flexible ICs 130 on a temporary carrier into individual, or strips or blocks of, ICs may be carried out from a front- or a back-side of the flexible ICs 130 depending on the nature of the temporary carrier and how the flexible ICs 130 are placed on that carrier (e.g., active side down or flexible substrate side down) as appropriate using a laser, a saw, or an abrasive water jet, or some other appropriate dicing procedure.

[0079] For example, where an entire wafer is transferred face (active side) down onto a temporary carrier, strips carrying a column or row of flexible ICs could be formed following the transfer by separating the wafer into strips from the back (substrate) side. This could, beneficially, be combined with an appropriate lamination step in which each column / row of flexible ICs is overlayed with an appropriate (e.g., electrostatic discharge (ESD) resistant) material to form a narrow ribbon-like structure or tape of flexible ICs 130 where the (e.g., ESD-resistant) material with which the flexible ICs 130 are covered effectively forms a flexible carrier tape on which the strip of flexible ICs 130 are located. Moreover, a plurality of such strips of flexible ICs 130 could be arranged together in coaxial alignment (e.g., before or during the lamination step) to allow a ribbon-like structure or tape to be formed that carries a plurality of strips of flexible ICs 130.

[0080] It will be appreciated that a strip or block of flexible ICs 130 (whether lifted from the rigid carrier 110 or separated after an entire wafer has been transferred to a temporary carrier 210) could be singulated into individual flexible ICs 130 at any appropriate time before, at, or possibly even after the point of attaching them to the intermediate carrier 240 (e.g., using laser cutting or the like).

[0081] Once the flexible ICs 130 have been singulated or separated into strips or blocks, each flexible IC 130 or strip or block of flexible ICs 130 may be picked up using an appropriate pick tool or using another tool (e.g., in the form of a porous vacuum chuck, or the like) that acts as a temporary carrier 210 from which the flexible ICs 130 may be transferred to the interposer sections of the intermediate carrier 240 for subsequent storage in a dense roll / tape-on-disk format.

[0082] Similarly, where the flexible ICs 130 are not singulated on the rigid carrier 10, but rather the whole flexible substrate 120 supporting the flexible ICs 130 is lifted off (e.g., peeled off) the rigid carrier 110, the whole flexible substrate 110 may be lifted using an appropriate tool (e.g., in the form of a porous vacuum chuck, or the like) that acts as a temporary carrier 210 from which the flexible ICs 130 may be subsequently transferred to interposer sections of the intermediate carrier 240 for subsequent processing into a dense roll / tape-on-disk format.Transfer of Flexible ICs to Temporary Carrier

[0083] An example method of transferring the singulated or separated flexible ICs 130 to a temporary carrier 210 (which may be flat as shown or, may be generally cylindrical as described above) will now be described in more detail with reference to Figure 5.

[0084] Figure 5a shows a cross-sectional view of the plurality of flexible ICs 130 formed on the flexible substrate 120 on top of the rigid carrier 110 in accordance with the procedure described above with reference to Figure 3. Figure 5a also depicts an active side 132 of each flexible IC 130, which is situated on a side of the flexible ICs 130 distal from the rigid carrier 110. Those active sides 132 may comprise, for example, appropriate electrical circuitry and components for electrically connecting the flexible ICs to other electronic circuitry (such as antennas and / or other components in end-products in the subsequent assembly process (e.g., assembly of RFID inlays or tags with flexible ICs). It will be appreciated that whilst the description focusses on examples in which the flexible ICs are fabricated ‘face-up’ ( / .e., with their active sides facing away from the rigid carrier) the processes described herein couldbe adapted to examples in which the flexible ICs are fabricated ‘face-down’ ( / .e., with their active sides facing the rigid carrier).

[0085] Where flexible ICs 130 are singulated, or separated into strips on the rigid carrier 110 (as described above) the individual, or strips or blocks of, flexible ICs 130 may be lifted off the rigid carrier 110 by bringing those flexible ICs 130 into contact with a surface of the temporary carrier210 (e.g., a surface of a porous vacuum chuck, or any other suitable temporary carrier 210) For example, as shown in Figures 5a and 5b, an IC receiving surface 212 of a temporary carrier 210 (e.g., a porous vacuum chuck, or the like) may be brought into contact with the flexible ICs 130 (e.g., the active side 132 of the flexible ICs 130) to form a vacuum therebetween. That in turn allows the lifting off of the flexible ICs 130 from the rigid carrier 110 by lifting the temporary carrier 210 up and away from the rigid carrier 110 (or alternatively by lifting the rigid carrier 110 up and away from the flexible substrate 120).

[0086] As mentioned above, the temporary carrier 210 may, itself, be rigid or flexible and the surface 212 of the temporary carrier 210 may be curved (e.g., cylindrical) or flat. To provide a curved IC receiving surface, where the temporary carrier 210 is flexible, the temporary carrier 210 may be placed on a curved (e.g., fully, or partially, cylindrical) surface of a stage or the like. Beneficially, where the surface 212 of the temporary carrier 210 is a curved surface, the lifting off of the flexible ICs 130 from the rigid carrier 110 may be facilitated through a rolling movement of the temporary carrier 210 over the flexible ICs 130, forming a vacuum therebetween. Once the vacuum is formed, the flexible ICs 130, can be lifted off the rigid carrier 110 as the temporary carrier 210 continues its rolling movement.

[0087] Many materials and devices suitable for use as a temporary carrier 240 are known in the art, in addition to the aforementioned vacuum chuck. Examples of such materials include films having controlled tack I stickiness (such as those sold by Gel- Pak®, under the name Gel-Film®, and / or related products), micro-textured materials such as dry adhesives and ‘gecko’-inspired materials (such as those sold by Setex®, under the name Setex®, and / or related products), vacuum-release films on textured mesh (such as the Vertec™ film membrane provided over a mesh material in the vacuum release plates provided by Gel-Pak®), electrostatic carriers (such as those provided by Eshylon Scientific), and or the like.

[0088] The surface 212 of the temporary carrier 210 brought into contact with the flexible ICs 130 may have a width corresponding to a single row or column of flexibleICs 130 ( / .e., a strip of flexible ICs 130) to facilitate the lifting off of a whole strip of flexible ICs 130 from the rigid carrier 110 as shown, by way of example, in Figure 4b.

[0089] Alternatively, the surface 212 of the temporary carrier 210 brought into contact with the flexible ICs 130 may have any intermediate width between the width of a single flexible IC and the width of the flexible substrate 120 (or greater) to facilitate the lifting off of a preconfigured set of flexible ICs from the rigid carrier 110 in one go. For example, the surface 212 may have a width corresponding to the width of 2, 3, 4... etc. rows or columns of flexible ICs on the rigid carrier 110.

[0090] It will be appreciated that where, rather than transferring individual, or strips of, flexible ICs 130 from the rigid carrier 110 to the temporary carrier 210, the whole flexible substrate of flexible ICs is transferred to the temporary carrier 210, the surface 212 of the temporary carrier 210 is wide enough to contact the whole set of flexible ICs 130 formed on the rigid carrier - i.e., greater than, or equal to, a width corresponding to the width of a typical flexible substrate 120 (e.g., approx. 300 mm for the width of a circular rigid carrier, approx. 680 mm for the width of a Generation 4 panel carrier, etc.). It will be appreciated that in this scenario the flexible ICs 130 may still be separated or singulated, or alternatively they may remain connected to one another in the form of one whole wafer of flexible ICs 130 and subsequently separated or singulated at some later stage of the process.

[0091] Whether singulated (or separated into strips or blocks) before or after transfer to temporary carrier 210, the individual (or strips or blocks of) flexible ICs 130 may be lifted from the temporary carrier 210 using an appropriate tool 220 (e.g., another vacuum chuck, tape, or some other temporary device for transferring the singulated I separated flexible ICs 130) for transfer to the intermediate flexible carrier 240.

[0092] The flexible ICs 130 may be transferred to the intermediate flexible carrier 240, (which may also be referred to as a web, or ribbon) and bonded thereto via appropriate electrical contacts. As described in more detail later, these electrical contacts are typically pre-configured on the intermediate flexible carrier 240, but may, alternatively, be formed on the flexible ICs 130 prior to their transfer to the intermediate flexible carrier 240.

[0093] It will be appreciated that whilst the description focuses primarily on scenarios in which the temporary carrier is a rigid temporary carrier, the temporary carrier could be a flexible carrier such as a flexible adhesive-coated release layer(e.g., a polymer-based flexible sheet, or a stretchable sheet mounted on a “wafer frame”) or any other suitable flexible temporary carrier.

[0094] One possible method for transferring the flexible ICs 130 from a temporary carrier 210 to an intermediate carrier 240 will now be described, by way of example only, with reference to Figure 6.Exemplary Method of Transferring Flexible ICs to Intermediate Flexible Carrier

[0095] As shown in Figure 6, the temporary carrier 210 to which flexible ICs 130 have been transferred in this example is configured to present a generally cylindrical IC surface ( / .e., a surface of the temporary carrier to which those flexible ICs 130 were transferred in step 2). The cylindrical temporary carrier 210, in this example, is arranged in a first configuration in which it is rotatable (in, and opposed to, the rotational direction ‘B’) about a central longitudinal axis (parallel to the y-axis depicted in the illustration), and optionally configured for controlled (e.g., indexed) movement linearly in other directions corresponding to a standard cartesian coordinate system (e.g., along the x-, y- and / or z- axes depicted). For example, the temporary carrier 210 may be mounted on a rotary mechanism, or the like, to facilitate the rotation of the temporary carrier 210. In this first configuration, the temporary carrier 210 is rotatable (and optionally linearly movable as appropriate) to iteratively locate the flexible ICs 130 at an appropriate position in which each flexible IC 130 can be removed from the IC surface of the temporary carrier 210 and respectively transferred to a corresponding interposer (‘strap’) section on the intermediate flexible carrier 240.

[0096] To facilitate the removal and transfer of the flexible ICs 130, an appropriate pick tool 220 (as seen in insert (A) of Figure 6) is provided for transferring the flexible ICs 130 directly from the cylindrical temporary carrier 210 to the corresponding interposer section on the intermediate flexible carrier 240. In this example, the pick tool 220 is a generally cylindrical pick tool that is configured for rotation (as indicated by arrow ‘C’) about a central longitudinal axis (parallel to the y-axis depicted in the illustration), and optionally linearly in other directions corresponding to the standard cartesian coordinate system. The cylindrical pick tool 220 is configured: to rotate (and optionally move linearly as appropriate) to a position in which it can pick one or more flexible ICs 130 from the IC surface of the temporary carrier 210; and, once the flexible IC(s) have been picked up, to rotate (and optionally move linearly asappropriate) to a position in which it can respectively place each picked-up flexible IC on a corresponding interposer section on the intermediate flexible carrier 240.

[0097] In more detail, the temporary carrier 210 may be rotated about the longitudinal axis in the rotational direction of (or opposite) arrow B, such that one or more flexible ICs 130 on the IC surface of the temporary carrier are brought into a removal position. The pick tool 220 may be similarly rotated about its longitudinal axis to bring a pickup surface of the pick tool 220 into alignment with the removal position of the flexible ICs 130 (this rotation may occur before, simultaneously with, or after the rotation of the temporary carrier 210). The pickup surface of the pick tool 220 may thus be brought into contact with the corresponding flexible IC(s) 130 that are located in their removal position on the temporary carrier 210 to attach to the corresponding flexible IC(s) 130 (e.g., by formation of an appropriate vacuum or adhesion force between the pickup surface and the flexible IC(s) 130). The pick tool 220 may then be rotated to lift the flexible IC(s) 130 attached to the pickup surface, from the temporary carrier 210 (it will be appreciated that the lifting may be assisted by a corresponding movement of the pick tool 220 and / or temporary carrier 210 away from one another). The pick tool 220 may be further rotated (and optionally move linearly as appropriate) to respectively move each flexible IC(s) 130 attached to the pickup surface into alignment with a corresponding interposer section on the intermediate flexible carrier 240. Each flexible IC(s) 130 on the pickup surface of the pick tool 220 may thus be brought into contact with the corresponding interposer section on the intermediate flexible carrier 240 and then released for subsequent bonding to the intermediate flexible carrier 240. It will be appreciated that the rotational (and any linear) movements of the pick tool 220 and temporary carrier 210 may be appropriately synchronised to allow continuous co-ordinated pickup, transfer, and placement of the flexible ICs. It will also be appreciated that the pick tool 220 may have a plurality of pickup surfaces distributed around its surface and may be configured for the pickup of one or more flexible ICs 130 from the temporary carrier 210 by one pickup surface while another pickup surface releases one or more other flexible ICs 130 onto the intermediate carrier 240. It will be appreciated that, further flexible ICs 130 may be transferred onto the IC surface of the temporary carrier 210 (for example from a rigid carrier) while other flexible ICs, already on the temporary carrier, are being removed for transfer to the intermediate flexible carrier 240. Effectively, this allows the temporary carrier 210 to be restocked in a refill operation that occurs in parallel with the transfer of flexible ICs 130 onto the intermediateflexible carrier 240. Such a refill operation may, beneficially, enable essentially uninterrupted assembly of flexible ICs 130 onto interposer sections of the intermediate flexible carrier 240.

[0098] The intermediate flexible carrier 240 may be a narrow ribbon-like strip that carries a 1 D array of flexible ICs 130, or the intermediate flexible carrier 240 may be a wider band-like strip that carries a 2D array of flexible ICs 130 (i.e., a plurality of parallel 1 D arrays of flexible ICs 130).

[0099] As described in more detail later, the intermediate flexible carrier 240 may be provided with an appropriate conductive pattern (e.g., in Al, Cu, Ni, Au, Sn, etc,) for forming contact features for respective electrical connection to corresponding electronic terminals of each flexible IC 130.

[0100] The intermediate flexible carrier 240 may, by way of example, include a flexible, insulating substrate that is suitable for supporting the conductive pattern (e.g., in Al, Cu, Ni, Au, Sn, etc,). In one example, the flexible insulating substrate may be a polymer such as PET, BOPP, PE, PI, etc, or a paper-based material or other suitable substrate, with the conductive pattern formed thereon.

[0101] The intermediate flexible carrier 240 may, by way of example, also include a layer of an appropriate adhesive to facilitate the adhesion of the flexible ICs 130 to the contact features on the intermediate flexible carrier 240. For example, an anisotropic conductive adhesive (ACA), an anisotropic conductive paste (ACP), or an anisotropic conductive film (ACF) may be deposited on the contact features along the length of the intermediate flexible carrier 240. Alternatively (or additionally), a layer of an appropriate adhesive may be provided on the flexible ICs 130 themselves. As those skilled in the art will understand, and as described in more detail later, other appropriate methods of bonding flexible ICs 130 to the contact features on the intermediate flexible carrier 240 may avoid the use of adhesives.

[0102] Once the flexible ICs 130 have been transferred to the intermediate flexible carrier 240 the adhesive may be cured by conventional thermodes or, for higher throughput, an in-line heated thermode roller 320 and an anvil or, opposing heated nip rollers so as to cure the ACA / ACP / ACF and bond the flexible ICs 130 to the intermediate flexible carrier 240.

[0103] Finally, once cured, and the flexible ICs 130 are bonded to the intermediate flexible carrier 240 thus forming a plurality of interposers including bonded flexible ICs 130, the intermediate flexible carrier 240 can then be rolled up into a reel / tape format for easy storage, transportation, and subsequent use in an assembly process.

[0104] It will be appreciated that, whilst the description focuses on applications in which a single flexible IC is attached to each interposer section, as part of the formation of the interposers, additional components may also be bonded to the intermediate flexible carrier 240 at appropriate locations, for example, discrete passive components, sensors, etc., such that the intermediate flexible carrier 240 supports a circuit, rather than just one or more flexible ICs 130.Conductive Pattern

[0105] Referring to Figure 7, which illustrates a section of an intermediate flexible carrier 240 to which flexible ICs 130 have been transferred, the conductive pattern provided on the intermediate flexible carrier 240 may respectively comprise, for each 1 D array of flexible ICs 130 to be attached to the intermediate flexible carrier 240, a pair of parallel conductive regions 245a, 245b (245) extending (substantially) the length of the intermediate flexible carrier 240. The parallel conductive regions may be separated by a gap suitable for the placement of ‘two-terminal’ flexible ICs 130 with each terminal electrically connected to one of the parallel conductive regions. Thus, when each flexible IC 130 is placed on a corresponding interposer section 250 on a surface of the intermediate flexible carrier 240 and bonded / secured in place, it bridges the gap between the parallel conductive regions 245 with each of its terminals contacting a different respective conductive region 245. Nevertheless, it will be appreciated that the conductive pattern may comprise a different respective discrete conductive region for connection to each terminal of each flexible IC 130, and / or may have additional conductive regions for contacting additional terminals of flexible ICs 130 having more than two terminals.Placement of the conductive pattern

[0106] As described above, the intermediate flexible carrier 240 may be preconfigured with a conductive pattern. Nevertheless it will be appreciated that rather than the conductive pattern being formed on the intermediate flexible carrier 240, conductive features may instead be provided on the flexible ICs 130 while they are still on the rigid carrier 110 (or possibly while they are on the temporary carrier 210).

[0107] For example, once the flexible ICs 130 have been formed on the flexible substrate 120 on the rigid carrier 110, conductive features (with or without an appropriate supporting substrate) may be formed on the flexible ICs 130 prior to the flexible ICs 130 being lifted from the rigid carrier 110. For example, the conductivefeatures (with or without an appropriate supporting substrate) may be bonded to the flexible ICs 130 that have been formed on the flexible substrate 120 using an appropriate roller or the like which is rolled over the flexible ICs 130 to deposit the conductive features thereon.

[0108] Once the conductive features (with or without an appropriate supporting substrate) have been bonded to the flexible ICs 130 while they are still on the rigid carrier 110, the flexible ICs 130 to which the conductive features are bonded may be lifted from the rigid carrier 110 and transferred to the surface of the intermediate flexible carrier 240 and bonded / secured thereto using any appropriate bonding / securing method described herein.

[0109] Alternatively, once the conductive features (with or without an appropriate supporting substrate) have been bonded to the flexible ICs 130 while they are still on the rigid carrier 110, the flexible ICs 130 may be left in place for use in a subsequent assembly procedure. This ‘leave in place’ approach may have particular benefit for flexible ICs 130 that have more than two electrical contacts. In this case the conductive features could be patterned to provide a suitable number of ‘legs’ which would then project from a surface of the flexible ICs 130 until their release from the rigid carrier 110.Other methods of transfer to the intermediate flexible carrier

[0110] In the approach for transferring the flexible ICs 130 to the intermediate flexible carrier 240 described above with reference to Figure 6, the flexible ICs 130 are transferred to a cylindrical temporary carrier 210 and then subsequently onto the intermediate flexible carrier 240 using an appropriate cylindrical pick tool 220. Nevertheless, this is only one example of how the flexible ICs 130 may be transferred to the intermediate flexible carrier 240.

[0111] In another example, the flexible ICs 130 may be transferred from the rigid carrier 110 to a temporary carrier 210 (e.g., in this example active side down as shown in Figures 5a and 5b) that has a generally flat planar IC surface. The temporary carrier may, in this case, be a rigid carrier, or may be a flexible carrier (e.g., in the form of a flexible release tape mounted on a wafer frame). Referring to Figure 8, which illustrates another method of transferring a plurality of flexible ICs from a temporary carrier 210 to an intermediate flexible carrier 240, a cylindrical or roller type pick tool 340 comprising a plurality of vacuum chucks or adhesion pads 342 may be rotated / rolled (in the rotational direction indicated by arrow D) betweenthe flexible ICs 130 on the temporary carrier 210 and a surface 242 of the intermediate flexible carrier 240 to transfer the flexible ICs 130 from the temporary carrier 210 to the first surface 242 of the intermediate flexible carrier 240.

[0112] For example, the pick tool 340 may be rotated about its longitudinal axis to bring a pickup surface on a corresponding vacuum chuck or adhesion pad 342 of the pick tool 340 into alignment with one or more flexible ICs 130. The pickup surface of the pick tool 340 may thus be brought into contact with the corresponding flexible IC(s) 130 to attach to the corresponding flexible IC(s) 130 (e.g., by formation of an appropriate vacuum or temporary adhesion between the pickup surface and the flexible IC(s) 130). The pick tool 340 may continue to be rotated to lift the flexible IC(s) 130 attached to the pickup surface, from the temporary carrier 210 (it will be appreciated that the lifting may be assisted by a corresponding slight movement of the pick tool 340 and / or temporary carrier 210 away from one another. The temporary carrier 210 may additionally or alternatively be translated in a direction parallel to the plane of its surface.). The pick tool 340 may be further rotated (and optionally move linearly as appropriate) to respectively move each flexible IC(s) 130 attached to the pickup surface into alignment with a corresponding interposer section on the intermediate flexible carrier 240. Each flexible IC(s) 130 on the pickup surface of the pick tool 340 may thus be brought into contact with the corresponding interposer section on the intermediate flexible carrier 240 and then released for subsequent bonding to the intermediate flexible carrier 240. It will be appreciated that in addition to the rotational (and any linear) movements of the pick tool 340, the temporary carrier 210 may also be moved appropriately in synchronisation with the pick tool 340, to allow continuous co-ordinated pickup, transfer, and placement of the flexible ICs. It will also be appreciated that the pick tool 340 may be configured for the pickup of one or more flexible ICs 130 from the temporary carrier 210 by a pickup surface of one vacuum chuck or adhesion pad 342 while another pickup surface of another vacuum chuck or adhesion pad 342 releases one or more other flexible ICs 130 onto the intermediate carrier 240.

[0113] As seen in Figure 8, in this example, as the flexible ICs 130 are placed, the intermediate flexible carrier 240 may be drawn past the pick tool, and onto a roll / reel 260 (e.g., for subsequent storage and / or usage in an electronic device assembly procedure).

[0114] It will be appreciated that the flexible ICs 130 placed on the intermediate flexible carrier 240 may be bonded to the intermediate flexible carrier 240 (or contactregions provided thereon), using any appropriate bonding / securing method described herein, before being rolled onto the reel / roll 260. For example, an appropriate adhesive may be provided on the surface 242 of the intermediate flexible carrier 240 and / or the flexible ICs 130 (as previously described - e.g., ACP, ACF, or the like) to assist with the transfer and adhesion of the flexible ICs 130 to the intermediate flexible carrier 240.

[0115] It will be appreciated that whilst the use of a temporary carrier is particularly beneficial for facilitating automation and high throughputs, the flexible ICs 130 may be transferred directly to the intermediate flexible carrier 240 from the rigid carrier 110.Singulation into separate interposers

[0116] Referring to Figure 9, which illustrates singulation of a plurality of interposers 252 carried by an intermediate flexible carrier, once the flexible ICs 130 have been bonded / secured to interposer sections 250 of the intermediate flexible carrier 240, the interposer sections 250 may be (partially) cut to define a plurality of distinct interposers 252, where each individual interposer 252 includes a single flexible IC 130 on its own conductive regions formed from conductive features 245a, 245b.

[0117] Specifically, prior to rolling the intermediate flexible carrier 240 onto a reel (or alternatively as the intermediate flexible carrier 240 is unrolled for assembly of e.g., RFID tags), each interposer 252 and its respective electrical contacts (e.g., conductive features 245a, 245b) on the intermediate flexible carrier 240 may be respectively singulated to allow easy separation of each interposer 252 (and the flexible IC 130 that it carries) for assembly onto / into an electronic device (e.g., an RFID inlay or tag).

[0118] For example, to singulate each interposer 252, partial transverse and longitudinal cuts 254 may be respectively performed around the perimeter of the interposer 252 (using, for example, a laser, or a blade, or another die-cutting technique) through the intermediate flexible carrier 240 (and through the contact regions 245a, 245b). One or more sections of the intermediate flexible carrier 240 around the perimeter may, nevertheless, be left uncut to form one or more frangible connections 256a, 256b (256) with the intermediate flexible carrier 240 that holds the interposer 252 in place until separation of the interposer 252 from the intermediate flexible carrier 240 is required (e.g., for the purposes assembly). As seen in Figure 9, each frangible connection 256 may be respectively positioned at a location of theinterposer 252 having both intermediate flexible carrier 240 and a conductive feature 245 present (e.g., frangible connections 256a), or at a location of the interposer 252 having only intermediate flexible carrier 240 and no conductive feature 245 present (e.g., frangible connections 256b).

[0119] Each interposer may have any suitable dimensions - for example having a length of between 3 and 100 mm (between distal ends) and a width of between 0.5 and 20 mm. The separation of the interposers on the intermediate flexible carrier 240 may be, for example, between 0.01 and 1 mm. The flexible ICs 130 themselves typically have lateral dimensions (width, length) of the order of 0.1 mm to 10 mm and the interposers 252 may have dimensions appropriately configured based on these IC dimensions and / or the dimensions of an article to which the interposers 252 are to be attached in the subsequent assembly stage (and a placement tolerance of that subsequent assembly stage).

[0120] It will be appreciated that whilst the examples described relate to interposers 252 that are arranged in a single row on the intermediate flexible carrier 240, extending transversely across the intermediate flexible carrier 240, any suitable arrangement and orientation may be chosen, depending on, for example: the nature of the dimensions of the flexible IC, the interposer 252, and the intermediate flexible carrier 240; the flexible IC transfer mechanism; the preferred form factor for the next (assembly) stage of electronic device (e.g., RFID inlay or tag) manufacturing, etc. In general, for the RFID inlay or tag example, the density of interposers 252 with their flexible ICs on the intermediate flexible carrier 240 will be relatively high, and the pitch of the interposers 252 will usually be shorter than that of antennas to which they will subsequently be attached.Forming narrower intermediate flexible carriers (e.g., 1D strips)

[0121] As mentioned above, a wider band-like intermediate carrier 240’ to which a 2D array of flexible ICs 130 have been transferred (i.e. , a plurality of parallel 1 D arrays of flexible ICs 130) may be sliced into narrower ribbon-like intermediate flexible carriers 240 (e.g., multiple intermediate flexible carriers 240 with a single row of flexible ICs 130 bonded on each intermediate flexible carrier 240). In a variation of this approach, the flexible ICs 130 may be bonded to the narrower ribbon-like intermediate flexible carriers 240 after they have been sliced from the wider bandlike intermediate carrier 240’.

[0122] Figure 10 illustrates a method of slicing a wide band-like intermediate flexible carrier that carries a 2D array of flexible ICs into a plurality of narrower intermediate flexible carriers that each carry a 1 D array of flexible ICs.

[0123] As seen in Figure 10, to slice the wider intermediate flexible carrier 240’ into multiple narrower intermediate flexible carriers 240, each comprising a 1 D array of flexible ICs 130 bonded thereto, a roll / reel of wide-band intermediate flexible carrier 240’ with flexible ICs 130 bonded / secured thereon (as described above) may be provided on a rotary mechanism 350 for facilitating the unrolling of the roll of wider intermediate flexible carrier 240’. It will be appreciated that whilst, in the illustrated example, the roll of the wider intermediate flexible carrier 240’ already has the 2D array of flexible ICs bonded to it, the roll of wider intermediate flexible carrier 240’ may not have the 2D array of flexible ICs in place. Instead, the 2D array of flexible ICs could be transferred to the wider intermediate flexible carrier 240’ as it is unrolled, before the wider intermediate flexible carrier 240’ is sliced into the multiple narrower intermediate flexible carriers 240. In this case the roll of the wider intermediate flexible carrier 240’ may, nevertheless, have the contact regions 245 to which the flexible ICs will, ultimately, be connected already formed on it for each narrower flexible carrier 240

[0124] To slice the wider intermediate flexible carrier 240’ into multiple narrower intermediate flexible carrier 240 of flexible ICs 130, as also shown in Figure 10, as the roll of wider intermediate flexible carrier 240’ with flexible ICs 130 bonded / secured thereto is unwound, the wider intermediate flexible carrier 240’ is slit to separate it into two or more (e.g., six as shown in Figure 10), parallel narrower intermediate flexible carriers 240, each comprising a single row of flexible ICs 130.

[0125] As seen in Figure 10, as the wider intermediate flexible carrier 240’ is sliced into the multiple narrower intermediate flexible carriers 240, each narrower intermediate flexible carrier 240 may be respectively drawn onto a respective assembly reel 360 (for subsequent storage and / or usage in an electronic device assembly procedure). Any waste material from between the narrower intermediate flexible carriers 240 may be collected as waste on, for example, one or more waste rolls 380, or the like, for future recycling.Other bonding / securing approaches

[0126] Whilst, as described above, the flexible ICs 130 may be bonded (both electrically and mechanically) to the intermediate flexible carrier 240 using ACP, ACF,or the like, other bonding methods and / or means of securing the flexible ICs 130 to the intermediate flexible carrier 240 (both electrically and mechanically) are possible. A non-conductive adhesive or underfill may be used to supplement the mechanical bond, for example on regions of the flexible ICs that do not feature electrical contacts.

[0127] In one example, the flexible ICs 130 may be electrically and mechanically bonded to the intermediate flexible carrier 240 using ultrasonic welding methods. For example, a sonotrode may be used to ultrasonically weld the flexible ICs 130 to the intermediate flexible carrier 240.

[0128] In another example, flexible ICs 130 may be electrically and mechanically connected to the intermediate flexible carrier 240 through the use of punch-through connections (e.g., mechanically crimped / embossed punch-through connections, or the like). Alternatively, the flexible ICs 130 may be secured to the intermediate flexible carrier 240 through the use of other appropriate mechanical crimping techniques and / or appropriate mechanical embossing techniques.

[0129] In another example, the flexible ICs 130 may be electrically and mechanically connected to the intermediate flexible carrier 240 through the use of over-edge printing techniques (e.g., with the contact pads of the flexible IC 130 facing away from the intermediate flexible carrier 240).

[0130] In another example, flexible ICs 130 may be electrically and mechanically connected to the intermediate flexible carrier 240 through the use of laser welding methods. For example, flexible ICs 130 may be secured to the intermediate flexible carrier 240 through laser drilling of appropriate portions of flexible ICs 130 and / or a surface of the intermediate flexible carrier 240 to produce vias between the flexible ICs 130 and the surface of the intermediate flexible carrier 240. Those vias may then subsequently be filled with solder, conductive adhesive material, or the like, to secure the flexible ICs 130 to the intermediate flexible carrier 240 .

[0131] In yet another example, the flexible ICs 130 may be electrically and mechanically connected to the intermediate flexible carrier 240 through the use of spot-welding methods. For example, flexible ICs 130 may be provided with contact pads that come into contact with a first surface 242 of the intermediate flexible carrier 240, and which is heated by spot-welding to fuse the contact pads to the intermediate flexible carrier 240.

[0132] In yet another example, flexible ICs 130 may be electrically and mechanically connected to the intermediate flexible carrier 240 through the use of contact pads provided on the flexible ICs 130 having ‘spiky’ structures, or otherappropriate types of structures that are configured to penetrate ( / .e., puncture) and engage with the electrical contacts 245 on the first surface 242 of the intermediate flexible carrier 240 thereby securing the flexible ICs 130 to the first surface 242 of the intermediate flexible carrier 240 and making electrical connections therebetween.Other methods of transfer to the temporary carrier

[0133] In the approaches for transferring the flexible ICs 130 to the intermediate flexible carrier 240 described above, the flexible ICs 130 are transferred directly to the temporary carrier 210 (and then subsequently onto the intermediate flexible carrier 240 via an appropriate pick tool 220). Nevertheless, it will be appreciated that the flexible ICs 130 may alternatively be transferred indirectly to the temporary carrier 210 (and then subsequently onto the intermediate flexible carrier 240 via an appropriate pick tool 220).

[0134] In one example, rather than direct transfer to the temporary carrier 210, the whole flexible substrate 120 of flexible ICs 130 may be transferred to dicing tape in a face-down orientation. That dicing tape, for example, could be brought into contact with the flexible ICs 130 on the flexible substrate 120, and lifted away from the flexible substrate 120 to form a piece of dicing tape supporting a plurality of flexible ICs 130 (e.g., at least one strip of flexible ICs 130). Having removed the plurality of flexible ICs 130 from the rigid carrier 110, they may be subsequently diced up (singulated) as necessary using methods already described, and then transferred to the temporary carrier 210 (e.g., by bringing the diced flexible ICs on the dicing tape into contact with the surface 212 of the temporary carrier 210).

[0135] In another example, a pick tool could be used to pick up individual flexible ICs 130 from the flexible substrate 120 and then subsequently deposit them onto the temporary carrier 210 ( / .e., a ‘pick-and-place’ approach). Once on the temporary carrier 210, the flexible ICs 130 may be subsequently transferred onto the intermediate flexible carrier 240 via an appropriate pick tool using any of the techniques described herein.Assembly

[0136] A more detailed description of stage 2 summarised above will now be described with reference to Figures 11 and 12a to 12d.

[0137] Figure 11 illustrates an example method of assembly for assembling interposers 252 (e.g., flexible ICs 130 with respective conductive features) onelectronic circuitry 422 (e.g., an antenna) of an electronic device supported by a substrate 420 (e.g., to form RFID tags, or the like).

[0138] As shown in Figure 11 , the electronic device substrate 420 may be provided as a flattened strip, or the electronic device substrate 420 may initially be provided in the form of a roll / reel of a web material, comprising the electronic circuitry 422 (e.g., antennas), which may be unrolled prior to placing interposers 252 on to the electronic circuitry 422 to form the electronic devices. Alternatively, a number of products, finished articles, a roll of labels, or the like, may be provided with which the interposers 252 may be assembled.

[0139] As illustrated in Figure 11 , to assemble the interposers 252 (e.g., flexible ICs 130 with respective conductive features) on the electronic circuitry 422 supported by the electronic device substrate 420, a roll / reel of the intermediate flexible carrier 240 carrying the interposers 252 as described above may be provided with each interposer 252 (partially) singulated for easy transfer onto the electronic circuitry 422 to form the corresponding electronic device. Alternatively, such singulation of interposers 252 may be performed after the intermediate flexible carrier 240 has begun to be unwound from its roll / reel.

[0140] During assembly, the roll / reel of intermediate flexible carrier 240 carrying the interposers 252 is unrolled over a strip of electronic circuitry 422, representing multiple partially completed electronic devices, supported by the electronic device substrate 420. Each interposer 252 and its corresponding flexible IC 130 is then respectively transferred to the electronic circuitry 422 representing a partially completed electronic device. It will be appreciated that, as shown in Figure 11 , the roll of intermediate flexible carrier 240 carrying the interposers 252 may have a relatively small pitch (spacing between I dimensions of the interposers 252) compared to the pitch of the electronic device substrate 420 (spacing between I dimensions of the partially completed electronic devices).

[0141] As the roll / reel of intermediate flexible carrier 240 carrying the interposers 252 is unrolled, each interposer 252 that is transferred to the electronic device may be popped / torn out of, or otherwise removed from, the intermediate flexible carrier 240 (by virtue of the cuts and frangible connection portions provided around its perimeter), to leave a small perimeter (waste material) of intermediate flexible carrier 240 which may be rolled up onto a waste roll 380.

[0142] It will be appreciated that to assist with the transfer of the interposers 252 to the electronic device any appropriate conductive adhesive may be used (e.g.,applied to the interposer 252 and / or the electronic circuitry 422) to ensure the interposer 252 sticks to the electronic circuitry 422 when they come into contact with one another. For example, conventional ACP attachment methods, similar to those outlined above for the attachment of flexible ICs 130 to the intermediate flexible carrier 240 may be used.

[0143] Alternatively, thanks to the low alignment accuracy demands and high material robustness associated with joining the relatively large conducting features of the interposers 252 to electrical contact areas of the electronic circuitry 422, other methods of attaching (i.e. , bonding) the interposers 252 to the electronic circuitry 422 may be used. For example, in a particularly beneficial alternative, the interposers 250 may be bonded to the electronic circuitry 422 using ultrasonic welding methods.

[0144] In another example, interposers 252 may be secured to the electronic circuitry 422 through the use of punch-through connections (e.g., crumped punch- through connections, or the like). Alternatively, the interposers 252 may be secured to the electronic devices through the use of other appropriate mechanical crimping techniques and / or appropriate mechanical embossing techniques.

[0145] In another example, interposers 252 may be secured to the electronic circuitry 422 through the use of laser welding methods. For example, interposers 252 may be secured to the electronic circuitry 422 through laser drilling of appropriate portions of interposers 252 and / or the electronic circuitry 422 and / or the substrate 420 supporting the electronic circuitry 422 to produce vias between the interposers 252 and the electronic devices. Those vias may then subsequently be filled with solder, conductive adhesive material, or the like, to secure the interposers 252 to the electronic circuitry 422.

[0146] In yet another example, interposers 252 may be secured to the electronic circuitry 422 through the use of contact pads provided on the interposers 252 having ‘spiky’ structures, or other appropriate types of structures that are configured to penetrate (j.e., puncture) and engage with the electronic circuitry 422, thereby securing the interposers 252 to the electronic circuitry 422 and making electrical connections therebetween.

[0147] Beneficially, such simple physical techniques for attaching interposers 252 to the electronic circuitry 422 and / or substrates 420 supporting the electronic devices (compared to adhesive attach and cure) are not only robust and very fast, but they are also compatible with reel-to-reel manufacturing. This makes them well-suited for positioning in the machinery of such manufacturing, for example conversionmachinery, widely used in the preparation of labels and flexible packaging, or the like.

[0148] It will be appreciated that, in some cases the interposers 252 may not include an insulating substrate - they may be composed entirely of conductive patterns (strips). In this case a protective layer of insulating material, such as a high durability encapsulant or varnish (e.g., parylene-c orthe like), could be applied to the interposer 252 following assembly to the electronic circuitry (e.g., antenna or other application circuit).

[0149] Furthermore, such simple physical techniques for attaching interposers 252 to electronic circuitry 422 in the manner described above are beneficially versatile in that they allow the interposers 252 to be attached to the electronic circuitry 422 in a variety of different orientations. In particular, it has been discovered that when ultrasonic and or laser welding techniques are used to attach interposers 252, small defects formed in the substrate 420 supporting the electronic circuitry 422 and / or the portion of intermediate flexible carrier 240 supporting the interposer 252 may be sufficient to allow electrical connection between the interposers 252 and the electronic devices (even when they are arranged in a counterintuitive manner e.g., substrate-to-substrate rather than electrical contact-to-electrical contact). Example orientations of the interposers 252 and the electronic circuitry 422 are as follows: a. The interposers 252 are orientated with their electrical contacts facing the electrical contacts of the electronic circuitry 422; b. The interposers 252 are orientated with their substrates (e.g., a portion of intermediate flexible carrier 240) facing the substrate 420 supporting the electronic circuitry 422; c. The interposers 252 are orientated with their substrates (e.g., a portion of intermediate flexible carrier 240) facing the electrical contact area of the electronic circuitry 422; or d. The interposers 252 are orientated with their electrical contacts facing the substrate 420 supporting the electronic circuitry 422.

[0150] These different possible orientations of interposers 252, and the electronic circuitry 422, are illustrated in Figures 12a-d.

[0151] In a first example orientation shown in Figure 12a, the interposer 252 is orientated such that the electrical contacts of the interposer 252 are facing theelectrical contact areas of the electronic circuitry 422 supported by substrate 420. It will be appreciated that when in this specific orientation an insulating layer 424 may be placed between some of the electronic circuitry 422 (e.g., where the electronic circuitry 422 comprises antennas, an insulating layer 424 may be places between antenna windings) and the interposer 252 to prevent electrical shorting. By way of example the insulating layer 424 may include a non-conducting adhesive, or the like.

[0152] In a second example orientation shown in Figure 12b, interposers 252 are orientated with their substrates (e.g., a portion of intermediate flexible carrier 240) facing the substrate 420 supporting the electronic circuitry 422. It will be appreciated that when in this specific orientation an insulating layer 424 may not be required.

[0153] In a third example orientation shown in Figure 12c, the interposers 252 are orientated with their substrates (e.g., a portion of intermediate flexible carrier 240) facing the electrical contact area of the electronic circuitry 422. It will be appreciated that when in this specific orientation an insulating layer 424 also may not be required.

[0154] In a fourth example orientation shown in Figure 12d, interposers 252 are orientated with their electrical contacts facing the substrate 420 supporting the electronic circuitry 422. It will be appreciated that when in this specific orientation an insulating layer 424 may not be required.

Claims

Claims1. A method of forming an assembly carrier holding a package of flexible material carrying multiple interposers for subsequent assembly into electronic devices, the method comprising: providing multiple integrated circuit (IC) dies, wherein each IC die is a component that, when assembled with corresponding electronic circuitry, forms at least a part of a respective electronic device; respectively transferring each IC die of at least a subset of the multiple IC dies to a corresponding section of an elongate flexible carrier, each section being configured for forming a respective interposer; and packaging the flexible carrier to which the IC dies have been transferred into at least one assembly carrier for subsequent use in assembly of each interposer carrying a corresponding IC die with corresponding electronic circuitry to form at least part of a respective electronic device.

2. A method as claimed in claim 1 , wherein each IC die is a flexible IC die.

3. A method as claimed in claim 2, wherein the flexible IC dies are provided on a rigid carrier.

4. A method as claimed in any preceding claim, wherein the packaging comprises winding the flexible carrier to which the IC dies have been transferred into at least one roll or reel held by the at least one assembly carrier.

5. A method as claimed in any preceding claim, further comprising laminating the flexible carrier with another layer to encapsulate each IC die transferred to the flexible carrier, prior to packaging the flexible carrier to which the IC dies have been transferred into the at least one assembly carrier.

6. A method as claimed in any preceding claim, wherein the multiple IC dies are provided as part of a wafer on which the IC dies were fabricated.

7. A method as claimed in claim 6, wherein the method further comprises singulating at least a subset of the multiple IC dies into individual dies prior to the transferring.

8. A method as claimed in claim 6, wherein the method further comprises separating at least a subset of the multiple IC dies into groups (e.g., columns, subarrays, or rows) of individual IC dies prior to the transferring.

9. A method as claimed in claim 3, wherein the multiple IC dies are provided on an initial carrier, optionally a wafer frame.

10. A method as claimed in any preceding claim, wherein the transferring comprises respectively transferring each IC die to the flexible carrier individually.

11. A method as claimed in any preceding claim, wherein the transferring comprises transferring a plurality of IC dies to the flexible carrier together as a one-dimensional array.

12. A method as claimed in any preceding claim, wherein the transferring comprises transferring each IC die of at least a subset of the multiple IC dies to a temporary carrier, and then transferring each IC die of at least a subset of the multiple IC dies from the temporary carrier to the corresponding section of the flexible carrier.

13. A method as claimed in claim 12, wherein the method further comprises singulating at least a subset of the multiple integrated circuit (IC) dies into individual dies on the temporary carrier.

14. A method as claimed in claim 12, wherein the method further comprises separating at least a subset of the multiple integrated circuit (IC) dies into groups (e.g., columns, subarrays, or rows) of individual IC dies on the temporary carrier.

15. A method as claimed in any of claims 12 to 14, wherein the transferring comprises respectively transferring each IC die to the temporary carrier individually.

16. A method as claimed in any of claims 12 to 14, wherein the transferring comprises transferring a plurality of IC dies to the temporary carrier together as a one-dimensional array.

17. A method as claimed in any of claims 12 to 14, wherein the transferring comprises transferring all, or a subset of, the multiple IC dies to the temporary carrier together as a two-dimensional array.

18. A method as claimed in any of claims 12 to 17, wherein the temporary carrier has an IC receiving surface to which at least a subset of the multiple IC dies are transferredprior to transfer to the corresponding section of the flexible carrier, the IC surface being a curved surface during at least the transfer of each IC die of at least a subset of the multiple IC dies from the temporary carrier to the corresponding section of the flexible carrier.

19. A method as claimed in any of claims 12 to 18, wherein the temporary carrier is configured for picking up each IC using a vacuum as part of the transferring.

20. A method as claimed in any of claims 12 to 18, wherein the temporary carrier configured for picking up each IC using adhesion as part of the transferring.

21. A method as claimed in any of claims 12 to 20, wherein the temporary carrier is rigid.

22. A method as claimed in any of claims 12 to 20, wherein the temporary carrier is flexible.

23. A method as claimed in any preceding claim, wherein the transferring of each IC die of at least a subset of the multiple IC dies to the corresponding section of the flexible carrier is configured to form a single one-dimensional array of ICs on the flexible carrier.

24. A method as claimed in any of claims 12 to 22, wherein the transferring of each IC die of at least a subset of the multiple IC dies to the corresponding section of the flexible carrier is configured to form a two-dimensional array of ICs, comprising a plurality of onedimensional arrays of ICs on the flexible carrier.

25. A method as claimed in claim 24, wherein the method further comprises splitting the flexible carrier into a plurality of narrower flexible carrier portions, each narrower flexible carrier portion carrying one of the one-dimensional arrays of ICs, and wherein the packaging of the flexible carrier comprises winding each narrower flexible carrier portion into a corresponding roll or reel for subsequent use in assembly of each interposer carrying a corresponding IC die, with corresponding electronic circuitry, to form at least part of a respective electronic device.

26. A method as claimed in any preceding claim further comprising respectively forming, prior to the packaging, at least one cut through the flexible carrier at least partially around each IC of at least a subset of the ICs transferred to the flexible carrier, to define a discrete interposer carrying that IC.

27. A method as claimed in any preceding claim wherein each IC has a plurality of connection terminals and wherein a conductive pattern is provided on the flexible carrier for facilitating electrical connection to each terminal of each IC transferred to the flexible carrier.

28. A method as claimed in claim 27, wherein the conductive pattern comprises at least two parallel conductive regions extending longitudinally along the intermediate carrier through each section to which a corresponding IC is transferred.

29. A method as claimed in claim 27, wherein the conductive pattern respectively comprises a plurality of discrete conductive regions, on each section of the flexible carrier to which a corresponding IC is transferred, for facilitating respective electrical connection to each terminal of that corresponding IC.

30. A method as claimed in any preceding claim further comprising forming a conductive pattern on each IC of at least a subset of the multiple ICs, prior to that IC being transferred to the flexible carrier, for facilitating electrical connection to each terminal of that IC.

31. A method as claimed in any preceding claim further comprising bonding, to the flexible carrier, each IC transferred to the flexible carrier.

32. A method as claimed in claim 31 , wherein the bonding is performed using at least one of: an anisotropic conductive adhesive (ACA), paste (ACP) or film (ACF), ultrasonic welding, laser welding, spot welding, punch-through connections, or over-edge printing.

33. A method as claimed in claim 31 , wherein each IC die is provided with contact pads with material puncturing features (e.g., spikes) formed thereon, and wherein the bonding is performed by puncturing the flexible carrier with the material puncturing features of each IC die.

34. A method of assembling electronic devices, the method comprising: providing at least one assembly carrier holding a package of flexible material, carrying multiple interposers, formed in accordance with any preceding claim, each interposer carrying a corresponding IC die with a plurality of terminals; and assembling each interposer of at least a subset of the multiple interposers with respective electronic circuitry supported by a substrate, by electrically connecting theplurality of terminals of the corresponding IC die carried by that interposer to that electronic circuitry, to form a corresponding electronic device.

35. A method of assembling electronic devices, the method comprising: providing at least one assembly carrier holding a package of flexible material, carrying multiple interposers, each interposer carrying a corresponding IC die with a plurality of terminals; and assembling each interposer of at least a subset of the multiple interposers with respective electronic circuitry supported by a substrate, by electrically connecting the plurality of terminals of the corresponding IC die carried by that interposer to that electronic circuitry, to form a corresponding electronic device.

36. A method as claimed in claim 34 or 35, wherein each interposer is connected to the flexible carrier by at least one frangible connection, and the assembling of each interposer with the corresponding electronic circuitry comprises respectively breaking the at least one frangible connection of that interposer, to remove that interposer from the flexible carrier.

37. A method as claimed in any of claims 34 to 36, wherein the electrically connecting the plurality of terminals of each IC die carried by a respective interposer, to the corresponding electronic circuitry, comprises respectively forming an electrical connection between each terminal and the corresponding electronic circuitry indirectly via a corresponding electrically conductive region provided on the respective interposer.

38. A method as claimed in any of claims 34 to 37, wherein the electrically connecting is performed using at least one of: an anisotropic conductive adhesive (ACP), paste (ACP) or film (ACF), ultrasonic welding, laser welding, spot welding, or punch-through connections.

39. A method as claimed in claim 38, wherein the electrically connecting is performed using ultrasonic welding and comprises forming, via the ultrasonic welding, defects in the flexible material supporting the interposer and / or a substrate supporting the electric circuitry to electrically connect the plurality of terminals of the corresponding IC die with the corresponding electronic circuitry.

40. A method as claimed in any of claims 34 to 39, wherein the assembling comprises respectively assembling each interposer with the corresponding electronic circuitry in: a first orientation in which an electrical contact side of the interposer faces an electrical contact side of the electronic circuitry; a second orientation in which the electrical contact side of the interposer faces a rear side of the substrate opposite a front side of the substrate that supports the electrical circuitry; a third orientation wherein the electrical contact side of the electronic circuitry faces a rear side of the interposer opposite the electrical contact side of the interposer; or a fourth orientation wherein the rear side of the interposer faces the rear side of the substrate supporting the electrical circuitry.41 . A method as claimed in any of claims 34 to 39, wherein the assembling comprises respectively assembling each interposer with the corresponding electronic circuitry in an orientation in which an electrical contact side of the interposer faces an electrical contact side of the electronic circuitry, and an insulating layer is provided between the electrical circuitry and the at least one interposer.

42. A method as claimed in any of claims 34 to 41 , wherein the electronic devices are radio frequency identification (RFID) devices.

43. A method as claimed in any of claims 34 to 42, wherein the electrical circuitry comprises an antenna.

44. An electronic device formed using the assembly process according to any of claims 34 to 43.

45. An assembly carrier holding a package of flexible material, carrying multiple interposers, each interposer carrying a corresponding IC die, formed using a method according to any of claims 1 to 33.

46. A radio frequency identification (RFID) device comprising an interposer, formed of a flexible material, and carrying at least one flexible IC die with a plurality of terminals, the plurality of terminals being electrically connected to an antenna to form the RFID device.

47. An assembly carrier holding a package of flexible material, carrying multiple interposers, each interposer carrying a corresponding flexible IC die with a plurality of terminals, each terminal of a given flexible IC die being electrically connected to a respective electrically conductive region provided on the corresponding interposer.

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