SUBSTRATE TO A CARRIER

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U. S. Provisional Application Serial No. 62/518,133 filed on June 12, 2017, the content of which is relied upon and incorporated herein by reference in its entirety.

BACKGROUND

[0002] The present disclosure relates to methods and apparatus for processing a flexible substrate, such as a highly flexible substrate.

[0003] Sheet manufacturing techniques are typically employed to process respective substrates (e.g., glass sheets) by conveying the respective sheets from a source, through any number of processing steps (heating, scoring, trimming, cutting, etc.), to a destination. The conveyance of the respective sheets may involve a number of elements that cooperate to move the respective substrates from station to station, preferably without degrading any desirable characteristics of the substrates. For example, typical transport mechanisms may include any number of noncontact support members, contact support members, rollers, lateral guides, etc., to guide the substrates through the system from the source, through each process station, and finally to the destination. The non-contact support members may include air bearings, fluid bar(s), low friction surface(s), etc. Non-contact support elements may include a combination of positive and negative fluid pressure streams in order to "float" the substrates during conveyance. Contact support elements may include rollers to stabilize the substrates during transport through the system.

[0004] The aforementioned transport mechanisms for sheet manufacturing systems are typically designed for relatively thick substrates, such as thicknesses that exhibit a sufficient stiffness to retain suitable mechanical dimensionality, material integrity, and/or other properties despite the forces that may be inflicted on the substrates during conveyance and processing through the manufacturing system. For example, typical sheet manufacturing techniques for cover glass used in liquid crystal displays (or other similar applications) typically require that the glass substrates exhibit a relatively high stiffness, such as may be the case when the substrates have thicknesses on the order of about 0.5 mm or greater. [0005] Use of these sheet manufacturing techniques may become problematic, however, when substrates having significantly lower stiffness (e.g., highly flexible glass substrates) are processed, such as glass substrates on the order of about 200 micrometers (um, microns) or less.

[0006] At least some of the problems that might arise using sheet manufacturing techniques on highly flexible substrates may be overcome by designing specialized processing equipment for conveying and processing such substrates. Such design, however, would require significant non-recurring expense in terms of time and resources, as well as rending existing (and possibly fully paid for) production equipment obsolete. For example, when processing highly flexible substrates, the conventional sheet manufacturing techniques may be discarded in favor of a "roll-to-roll" conveyance and processing equipment. In principle, such a substitution might lead to lower manufacturing costs in the long term; however, the non-recurring expense to design and implement a new roll-to-roll system for highly flexible substrate material would be very significant, and possibly require innovation to process certain types of flexible substrates.

[0007] Accordingly, there are needs in the art for improved methods and apparatus for modifying flexible substrates such that they may be processed using sheet processing techniques.

SUMMARY

[0008] For purposes of discussion, the disclosure herein may often refer to methodologies and apparatus involving substrates formed from glass; however, skilled artisans will realize that the methodologies and apparatus herein apply to substrates of numerous kinds, including glass substrates, crystalline substrates, single crystal substrates, glass ceramic substrates, polymer substrates, etc.

[0009] For example, one type of flexible substrate material is referred to as Corning® Willow® Glass, a display grade glass available from Corning Incorporated, Corning, NY, which is a glass material suitable for many purposes. The relatively thin material (e.g., about 0.1 mm thick, which is approximately the thickness of a sheet of paper), combined with the strength and flexibility of the glass material, support applications from the ordinary to the very highly sophisticated, such as wrapping a display element around a device or structure. Corning® Willow® Glass may, for example, be used for very thin backplanes, color filters, etc., for both organic light emitting diodes (OLED) and liquid crystal displays (LCD), such as may be used in high performance, portable devices (e.g., smart phones, tablets, and notebook computers). Corning® Willow® Glass may also be used for producing electronic components, such as touch sensors, seals for OLED displays and other moisture and oxygen sensitive technologies.

[0010] Corning® Willow® Glass may be on the order of about 100 μιτι to 200 μιτι thick, and is highly flexible, having glass characteristics including: a density of about 2.3 - 2.5 g/cc, Young's Modulus of about 70 - 80 GPa, Poisson Ratio of about 0.20 - 0.25, and minimum bend radius of about 185 - 370 mm.

[0011] If respective substrates of Coming® Willow® Glass were processed using typical sheet manufacturing techniques, the thinness and flexibility of the material could result in degradation of the material characteristics of the glass, critical failure of the glass, and/or interruption or damage to the sheet processing equipment. Therefore, techniques exist for processing flexible substrates, such as Corning® Willow® Glass, by providing for temporarily bonding the flexible substrate to a thicker and/or stiffer carrier substrate, which presents the flexible substrate as having stiffer mechanical characteristics while being processed in the sheet processing system. After processing, the temporary bond is released and the flexible substrate is subject to further manufacturing, processing, or delivery to a customer.

[0012] Existing techniques for temporarily bonding the flexible substrate to a thicker and/or stiffer carrier substrate have been successfully achieved for substrate sizes of about 370 mm x 470 mm. One measure of such success is maintaining a desired level of flatness (e.g., maintaining any out-of-plane curvature of the bonded flexible substrate to the carrier substrate of less than about 100 um). It has been discovered, however, that the complexities and difficulties in maintaining the noted flatness rise significantly as the size of the flexible substrate increases beyond 370 mm x 470 mm, such as to 1100 mm x 1300 mm or more, and as the throughput of a continuous bonding process is increased, such as to speeds of 35 mm/second or more.

[0013] Other aspects, features, and advantages will be apparent to one skilled in the art from the description herein taken in conjunction with the accompanying drawings. DESCRIPTION OF THE DRAWINGS

[0014] For the purposes of illustration, there are forms shown in the drawings that are presently preferred, it being understood, however, that the embodiments disclosed and described herein are not limited to the precise arrangements and instrumentalities shown.

[0015] FIG. 1 is a perspective view, schematic illustration of a process in which a flexible substrate is bonded to a carrier substrate in preparation for processing the flexible substrate in a conventional sheet manufacturing system;

[0016] FIG. 2 is a side view, schematic illustration of the flexible substrate bonded to the carrier substrate for processing the flexible substrate in the conventional sheet manufacturing system;

[0017] FIG. 3 is a perspective view, schematic illustration of a first sequence in which the flexible substrate may be bonded to the carrier substrate, which results in a dome-shaped out- of-plane deformation of the bonded structure;

[0018] FIG. 4 is a graphical illustration of a quantitative measure of the out-of-plane deformation of the bonded structure of FIG. 3;

[0019] FIG. 5 is a perspective view, schematic illustration of a second sequence in which the flexible substrate may be bonded to the carrier substrate, which results in a cylindrically- shaped out-of-plane deformation of the bonded structure;

[0020] FIG. 6 is a graphical illustration of a quantitative measure of the out-of-plane deformation of the bonded structure of FIG. 5;

[0021] FIG. 7 is a perspective view of an bonding apparatus for carrying out a continuous bonding process on sources of flexible substrates and carrier substrates;

[0022] FIG. 8 is a schematic illustration of a mechanism that may be employed to initiate a bonding start line and a bond front that characterizes the bonding process of FIG. 5;

[0023] FIG. 9 is schematic illustration of a mechanism that may be employed to create an out-of-plane deformation of the carrier substrate in order to counteract an induced out-of- plane curvature in the bonded structure; [0024] FIG. 10 is side schematic illustration of a mechanism that may be employed to provide lift, holding, and release of the flexible substrate adjacent the carrier substrate;

[0025] FIG. 11 is top down schematic illustration of the mechanism of FIG. 10;

[0026] FIGS. 12A - 12F are side schematic illustrations of the operation of the mechanism of FIG. 10 as such provides lift, holding, and release of the flexible substrate adjacent the carrier substrate;

[0027] FIGS. 13 A - 13C are graphical illustrations of qualitative measures of the bonded structure resulting from the bonding process disclosed herein; and

[0028] FIGS. 14A - 14C are further graphical illustrations of qualitative measures of the bonded structure resulting from the bonding process disclosed herein;.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] For purposes of discussion, the embodiments discussed below refer to the processing of a flexible substrate formed from glass, which is a preferred material. It is noted, however, that the embodiments may employ different materials to implement the flexible substrate, such as crystalline substrates, single crystal substrates, glass ceramic substrates, polymer substrates, etc.

[0030] Reference is now made to FIG. 1, which is a perspective view, schematic illustration of a process in which a flexible substrate 102 is temporarily bonded to a carrier substrate 104 in preparation for processing the flexible substrate 102 in a conventional sheet manufacturing system. As mentioned previously, a rationale for bonding the flexible substrate 102 to the thicker and/or stiffer carrier substrate 104 is to present the flexible substrate 102 as if it had stiffer mechanical characteristics while being processed in the sheet processing system that is designed for handling stiffer substrates than the flexible substrate 102.

[0031] With reference to FIG. 2, a schematic illustration of the resulting bonded structure 100 (the flexible substrate 102 atop the carrier substrate 104) is shown. In this regard, the carrier substrate 104 may be formed from a sheet of material, such as a glass material, where the carrier substrate 104 has a length dimension in an X-axis, a width dimension in a Y-axis, and a thickness dimension in a Z-axis (within a Cartesian Coordinate System). Notably, the X-axis and Y-axis define an X-Y plane, which may be referred to herein as being in-plane and/or defining an in-plane reference. Similarly, the flexible substrate 102 is formed from a sheet of material, which may also be a glass material, where the flexible substrate 102 has a length dimension in the X-axis, a width dimension in the Y-axis, and a thickness dimension in the Z-axis. As previously discussed, the flexible substrate 102 exhibits at least one of: (i) a flexibility that is substantially more flexible than a flexibility of the carrier substrate 104, and (ii) a thickness that is substantially less than a thickness of the carrier substrate 104.

[0032] In one or more embodiments, the flexible substrate 102 may be formed from glass and have a thickness of one of: (i) from about 50 um (microns or micrometers) to about 300 um, and (ii) from about 100 um to about 200 um. In accordance with one or more further embodiments, the flexible substrate 102 may have at least one of: a density of about 2.3 - 2.5 g/cc, a Young's Modulus of about 70 - 80 GPa; a Poisson Ratio of about 0.20 - 0.25, and a minimum bend radius of about 185 - 370 mm.

[0033] Similarly, in one or more embodiments, the carrier substrate 104 may be formed from glass; however, the carrier substrate 104 preferably has a thickness of from about 400 to about 1000 um, notably thicker than the flexible substrate 102.

[0034] Although further details regarding the bond between the flexible substrate 102 and the carrier substrate 104 will be presented later herein, it is preferred that the bond is temporary, and employed primarily for the purpose of processing the flexible substrate 102 in a conventional sheet manufacturing system. After such processing, the temporary bond may be undone and the flexible substrate 102 may be separated from the carrier substrate 104 for further processing and/or application outside the conventional sheet manufacturing system.

[0035] Any number of mechanisms and/or processes for achieving the actual bond force (temporary or otherwise) between the flexible substrate 102 and the carrier substrate 104 may be employed, so long as the bond parameters and characteristics discussed later herein are also considered and compensated for. By way of example, one skilled in the art may employ and/or modify one or more of the bonding processes disclosed in the following patent applications in achieving the conditions disclosed herein: U. S. Provisional Patent Application No. 61/736,887, filed on December 13, 2012; U.S. Patent Application No. 14/047,506, filed on October 7, 2013; U.S. Provisional Patent Application No. 61/931924 filed on January 27, 2014; U.S. Provisional Patent Application No. 61/931,912, filed on January 27, 2014; U. S. Provisional Patent Application No. 61/931,927 filed on January 27, 2014; and U. S. Provisional Patent Application No. 61/977,364 filed on April 9, 2014, the entire disclosures of which are hereby incorporated by reference.

[0036] In order to more fully appreciate the methods and apparatus disclosed herein, a detailed discussion of some bonding properties and phenomena will now be presented with reference to FIGS. 3 and 4. FIG. 3 is a perspective, schematic illustration of an example of a sequence in which the flexible substrate 102 may be bonded to the carrier substrate 104, which results in a substantially dome-shaped, out-of-plane deformation of the bonded structure 100. FIG. 4 is a graphical illustration of a quantitative measure of the out-of-plane deformation of the bonded structure 100 of FIG. 3.

[0037] Again, for purposes of discussion, prior to, and at least partially during, the bonding process, the flexible substrate 102 and the carrier substrate 104 are characterized by respective length dimensions in the X-axis, respective width dimensions in the Y-axis, and respective thickness dimensions in the Z-axis. The X-axis and Y-axis thereby define an X-Y plane, which is an in-plane reference (against which a flatness of the bonded structure 100 is compared, for example in FIG. 4).

[0038] With specific reference to FIG. 3, the bonding process may include locating the flexible substrate 102 adjacent (for example, over) the carrier substrate 104 and then inducing the bond. More particularly, when the flexible substrate 102 is located adjacent the carrier substrate 104 there will typically be some atmospheric gas (such as air) that maintains some relatively small separation between the substrates. In order to initiate the bond, a start area may be established by a localized urging of the flexible substrate 102 and the carrier substrate 104 together, such as via a mechanical pressing force. In the illustrated example, a single point and/or generally circular area may be established as the start area 20 by way of a focused pressure of the flexible substrate 102 toward, and into contact with, the carrier substrate 104, which is illustrated by the arrow 22.

[0039] Skilled artisans will appreciate that one or more other bonding criteria may also be brought into play along with inducing the start area (see the aforementioned U. S. patent application disclosures). In so doing, the induced bond at the start area 20 will propagate in accordance with a bond front 24. In the case of the illustrated start area 20 (i.e., the single point and/or generally circular area), the bond front 24 will include radially directed vectors extending away from the start area 20 in directions in the X-Y plane. The bond front 24 will continue to expand radially outwardly in the X-Y plane until it reaches an edge of the substrates, at which time the flexible substrate 102 is bonded to the carrier substrate 104.

[0040] Through experimentation, it has been discovered that the aforementioned (radially extending) bond front 24 will cause the bonded structure 100 to deform out-of-plane (i.e. , out of a reference plane defined by the Y-Y plane). In particular, the radially extending bond front 24 results in a generally dome-shaped, out-of-plane curvature in the Z-axis, which is shown in the example as being in the downward direction along the Z-axis. Stated another way, without some compensating mechanism, the mere bonding of the flexible substrate 102 to the carrier substrate 104 will produce an undesirable out-of-plane curvature, which if left unmodified may produce further undesirable effects in the down-stream processes of the sheet manufacturing system. Indeed, it is generally understood that the conventional sheet manufacturing system works best when the incoming substrates to be processed (in this case the bonded structures 100) are relatively flat.

[0041] The bonded structure 100 in FIG. 3, however, is not generally flat. Indeed, with reference to FIG. 4, a graphical illustration of a quantitative measure of the out-of-plane deformation of an example of the bonded structure 100 of FIG. 3 is shown. In connection with the laboratory experimentation, the Z-axis of the graph in FIG. 4 is measured in um, and the X-axis and Y-axis are measured in mm. The out-of-plane, generally dome-shaped curvature is on the order of 225 - 300 um at a maximum. Such curvature may not be acceptable in conventional sheet manufacturing systems and/or may result in defective intermediate products, which are unsuitable for commercial applications. As will be discussed in more detail later herein, compensation of such undesirable bonding phenomena may be achieved in accordance with embodiments herein.

[0042] Another example of the out-of-plane curvature resulting from bonding the flexible substrate 102 to the carrier substrate 104 will be now be presented with reference to FIGS. 5 and 6. FIG. 5 is a perspective, schematic illustration of an example of an alternative sequence in which the flexible substrate 102 may be bonded to the carrier substrate 104, which results in a substantially cylindrically-shaped, out-of-plane deformation of the bonded structure 100. FIG. 6 is a graphical illustration of a quantitative measure of the out-of-plane deformation of the bonded structure 100 of FIG. 5 obtained through experimentation. [0043] With specific reference to FIG. 5, the bonding process may again include locating the flexible substrate 102 adjacent (for example, over) the carrier substrate 104 and then inducing the bond. In order to initiate the bond, the start area is again established by a localized urging of the flexible substrate 102 and the carrier substrate 104 together, such as via a mechanical pressing force. In the illustrated example, as compared with the previous example of FIG. 3 however, a generally linearly extending start area 30 is established by way of a linearly extending focused pressure of the flexible substrate 102 toward, and into contact with, the carrier substrate 104. Mechanisms for producing the linearly extending pressure and resultant linearly directed and extending start area 30 will be discussed in more detail later herein.

[0044] In the case of the illustrated linearly directed and extending start area 30, the bond front 34 will include linearly directed vectors extending transversely away from the elongate direction of the start area 30, in the X-Y plane. For example, the start area 30 may extend substantially linearly along a line parallel to the Y-axis (such as along adjacent edges of the respective substrates 102, 104 shown at the right of FIG. 5). As a result, the bond front 34 has been found to include vectors that are spaced substantially linearly along a line parallel to the Y-axis (such as the line 30), and propagate away from the start area 30 in a direction transverse to the Y-axis (e.g., in a direction parallel to the X-axis, perpendicular to the Y- axis). The bond front 34 will continue to expand linearly away from the start area 30 in the X-Y plane until it reaches the end of the substrates, at which time the flexible substrate 102 is bonded to the carrier substrate 104.

[0045] Skilled artisans will appreciate that a variation of the process shown in FIG. 5 and discussed immediately above includes initiating the start area 30 in an intermediate location along the X-axis, e.g., somewhere between the adjacent edges of the respective substrates 102, 104. In such case, the bond front 34 will again include vectors that are spaced substantially linearly along a line parallel to the Y-axis (such as the line 30), and again will propagate away from the start area 30 in a direction transverse thereto. Notably, however, the bond front 34 would include two components, one component of vectors extending linearly (and transversely) away from the start area 30 in one direction (e.g., leftward in FIG. 5), and another component of vectors extending linearly (and transversely) away from the start area 30 in another, opposite direction (e.g. , rightward in FIG. 5). Both components of the bond front 34 will continue to expand linearly away from the start area 30 in the X-Y plane until they reach an edge of the substrates, at which time the flexible substrate 102 is bonded to the carrier substrate 104.

[0046] Through experimentation, it has been discovered that the aforementioned (linearly extending) bond front 34 will also cause the bonded structure 100 to deform out-of-plane (i.e., out of a reference plane defined by the X-Y plane). In particular, the linearly extending bond front 34 results in a generally cylindrical-shaped, out-of-plane curvature in the Z-axis, which is shown in the example as being in the downward direction along the Z-axis. Again, without some compensating mechanism, the mere bonding of the flexible substrate 102 to the carrier substrate 104 will produce an undesirable out-of-plane curvature, which if left unmodified may produce further undesirable effects in the down-stream processes of the conventional sheet manufacturing system. Again, the bonded structure 100 in FIG. 5 is not generally flat. Indeed, with reference to FIG. 6, laboratory experimentation reveals that the out-of-plane, generally cylindrical-shaped curvature is on the order of 200 - 250 um at a maximum.

[0047] As discussed above, it is desirable to maintain the out-of-plane curvature of the bonded flexible substrate 102 to the carrier substrate 104 of less than about 100 um. While some existing techniques for temporarily bonding the flexible substrate 102 to the carrier substrate 104 have been successful in achieving desired flatness goals for substrate sizes of about 370 mm x 470 mm, the complexities and difficulties in maintaining the flatness rise significantly as the size of the flexible substrate 102 increases, such as to 1 100 mm x 1300 mm or more, and as the throughput of the continuous bonding process is increased, such as to speeds of 35 mm/second or more.

[0048] In view of the foregoing, reference is now made to FIG. 7, which is a perspective view of a bonding apparatus 200 for carrying out a continuous bonding process on sources of flexible substrates 102 and carrier substrates 104. Although, one of the primary functions of the bonding apparatus 200 is the bonding process itself, an additional function includes inducing an out-of-plane curvature in the carrier substrate 104 prior to bonding in order to counteract the propensity for the out-of-plane deformation that would otherwise occur in the bonded structure 100 of the flexible substrate 102 and the carrier substrate 104.

[0049] The bonding apparatus 200 includes a flexible substrate transport mechanism 202, a carrier substrate transport mechanism 204, a (cylindrical) chuck 220, a transfer mechanism 250, a pressing mechanism 280 (not shown in FIG. 7), and a controller 290. One or more of the elements of the bonding apparatus 200 are responsive to signal commands issued by the controller 290, which executes actions in accordance with a programmed algorithm (e.g. , via a software program). In this regard, the controller 290 may be implemented using any of the known computing technologies, such as digital circuitry, any of the known microprocessors that are operable to execute software and/or firmware programs, one or more programmable digital devices or systems, such as programmable read only memories (PROMs), programmable array logic devices (PALs), etc.

[0050] The flexible substrate transport mechanism 202 may receive respective sheets of the flexible substrates 102 from a loading zone, which sheets have been cut from a spool or the like (not shown), as is known in the art. The flexible substrate transport mechanism 202 operates to move the flexible substrates 102 from the loading zone to a bonding area, where the flexible substrates 102 are bonded to the carrier substrates 104. In preferred embodiments, the flexible substrate transport mechanism 202 achieves the transport functionality preferably using contactless, or at least minimal contact, sheet transport technologies, such as ultrasonic sheet transport technologies or fluid floatation transport technologies, which are known in the art. At least the rate and/or timing at which the flexible substrate transport mechanism 202 operates to move the flexible substrates 102 from the loading zone to the bonding area are preferably variable in accordance with signal commands from the controller 290.

[0051] As noted above, the flexible substrates 102 may be characterized as having a length dimension in the X-axis, a width dimension in the Y-axis, and a thickness dimension in the Z- axis (see, FIG. 3). As previously mentioned, the flexible substrate 102 may be formed from any suitable material, such as glass, and is very thin, such as having a thickness of one of: (i) from about 50 um to about 300 um, and (ii) from about 100 um to about 200 um. The flexibility of the flexible substrate 102 may be characterized in any number of ways, such as having at least one of: a density of about 2.3 - 2.5 g/cc, a Young's Modulus of about 70 - 80 GPa; a Poisson Ratio of about 0.20 - 0.25, and a minimum bend radius of about 185 - 370 mm. Still further, the flexible substrate 102 may have a relatively large surface area (particularly given its very thin characteristics), such as having an area defined by one of: (i) a length of greater than about 500 mm and a width of greater than about 500 mm; and (ii) a length of about 1 100 mm and a width of about 1300 mm. [0052] The carrier substrate transport mechanism 204 may receive respective sheets of the carrier substrates 104 from another loading zone, which sheets have been cut from a spool, ribbon, or the like (not shown), as is known in the art. The carrier substrate transport mechanism 204 operates to move the carrier substrates 104 from the loading zone to the bonding area, preferably using contactless, or at least minimal contact, sheet transport technologies, such as ultrasonic sheet transport technologies or fluid floatation technologies, which are known in the art. At least the rate and/or timing at which the carrier substrate transport mechanism 204 operates to move the carrier substrates 104 from the loading zone to the bonding area are preferably variable in accordance with signal commands from the controller 290.

[0053] As noted above, the carrier substrate 104 may be characterized as having a length dimension in an X-axis, a width dimension in a Y-axis, and a thickness dimension in a Z- axis, where the X-axis and Y-axis define an X-Y plane (see FIG. 3). As previously mentioned, the carrier substrate 104 may be formed from any suitable material, such as glass, as is substantially thicker than, and/or less flexible than, the flexible substrates 102. For example, the carrier substrate 104 may have a thickness of about 400 to about 1000 um.

[0054] The cylindrical chuck 220 operates to hold the carrier substrate 104 in the bonding area, preferably below the flexible substrate 102. Although further details of the cylindrical chuck 220 will be presented below, it is noted that the cylindrical chuck 220 preferably achieves the aforementioned holding function using vacuum technologies, which are known in the art. At least the timing and degree to which the cylindrical chuck 220 operates to receive, hold and then release the carrier substrates 104 to/from the bonding area are preferably variable in accordance with signal commands from the controller 290.

[0055] The transfer mechanism 250 operates to: (i) move, for example lift, the flexible substrate 102 off of the transport mechanism 202, preferably without contacting the flexible substrate 102, and (ii) hold the flexible substrate 102 adjacent the carrier substrate 104 such that a gap therebetween is established in a controlled manner. For example, the gap may be on the order of about 100 um to 1000 um, more preferably about 250 um to 500 um. In preferred embodiments, the transfer mechanism 250 accomplishes the moving, lifting and holding operations using a combination ultrasonic and vacuum mechanism, which will be described in more detail later herein. At least the rate of lifting, moving, holding, and releasing (which will be described in more detail later herein), timing thereof, and/or magnitude of the gap at which the transfer mechanism 250 manipulates the flexible substrate 102 are preferably variable in accordance with signal commands from the controller 290.

[0056] The pressing mechanism 280 operates to induce a bond between the flexible substrate 102 and the carrier substrate 104, preferably by providing linearly extending pressure down on an opposite side of the flexible substrate 102 from the carrier substrate 104, until there is contact between the flexible substrate 102 and the carrier substrate 104. Although further details of the pressing mechanism 280 will be presented later herein, it is noted that in some embodiments, and with reference to FIG. 5, the contact is an elongate start area (e.g. , a line) 30 from which a bond initiates (extending substantially along a line parallel to the Y-axis), such that a first bond front propagates away from the start line 30 in a first direction substantially transverse to the start line 30 and the Y-axis. Although, FIG. 5 shows the elongate start line 30 near an edge of the flexible substrate 102, the pressing mechanism 280 may operate to induce the bond at an intermediate lateral position (between edges of the flexible substrate 102 along the X axis), such that a second bond front also propagates away from the start line 30 in a second direction, substantially opposite to the first direction, and transverse to the start line 30 and the Y-axis. At least the position at which the bond is induced, the rate at which the bond is induced, etc. are variable in accordance with signal commands from the controller 290 to the pressing mechanism 280.

[0057] Skilled artisans will appreciate that there are a number of mechanisms that may be employed for producing the linearly extending pressure and resultant linearly directed and extending start line 30. For example, with reference to FIG. 8, the pressing mechanism 280 may include a leaf-spring deflection element 282, which includes a relatively rigid frame member 284 and a relatively flexible spring element 286. The flexible spring element 286 is rotationally coupled to the frame member 284 via respective hinged couplings 284-1 , 284-2 to produce a leaf-spring deflection element. In operation, the frame member 284 and spring element 286 are oriented parallel to the desired start line 30, such as above the flexible substrate 102. A downwardly directed force is then applied to the frame member 284 such that the flexible spring element 286 urges the flexible substrate 102 against the carrier substrate 104 along a line, thereby producing the desired start line 30.

[0058] In order to achieve a significant level of controllability in connection with the pressing mechanism 280, the leaf-spring deflection element 282 may include one or more mechanical actuators 288-1, 288-2 that couple the frame member 284 to a ridged portion of the bonding apparatus 200. By way of example, the one or more mechanical actuators 288-1 , 288-2 may be implemented using electro -mechanical technologies (e.g. , servo motors, etc.), pneumatic technologies, hydraulic technologies, etc., in such a way as to permit the functionality of the pressing mechanism 280 to be variable in response to signal commands from the controller 290.

[0059] Thus, in response to signal commands from the controller 290, the one or more mechanical actuators 288-1 , 288-2 may effect the downwardly directed force to urge the flexible spring element 286 against the flexible substrate 102 in order to at least one of: (i) press the flexible substrate 102 toward the carrier substrate 104, (ii) initiate a substantial localized area of contact (e.g., relatively less elongate area of contact than the final start line 30) with the carrier substrate 104, (iii) further press the flexible substrate 102 into contact with the carrier substrate 104 in order to modify the localized area of contact into the elongate start line 30, and (iv) maintain the pressing of the flexible substrate 102 in contact with the carrier substrate 104 for a predetermined time after at least one of the first and second bond fronts propagate away from the start line 30.

[0060] As mentioned previously, with reference to FIG. 5 the one or more elongate bond fronts propagating from the start line 30 may cause the undesirable curvature out of the X-Y plane. In accordance with one or more embodiments herein, compensation of the cylindrical- shaped out-of-plane deformations due to the undesirable bonding phenomena may be achieved. In general, such compensation may be achieved by manipulating the carrier substrate 104 prior to the bonding operation. For example, the process may include at least one of stressing and straining the carrier substrate 104 to induce a curvature out of the X-Y plane in a direction along the Z-axis that counteracts the induced curvature out of the X-Y plane that would occur via the bond front propagation phenomena. Thus, for example, if the bond front propagation phenomena tends to induce curvature out of the X-Y plane in a direction characterized as shown in FIG. 5 (e.g., in a downward direction or negative Z-axis direction), then the general compensation methodology involves at least one of stressing and straining the carrier substrate 104 to induce a curvature out of the X-Y plane in an opposite direction (e.g., upward or positive Z-axis direction).

[0061] With reference to FIG. 9, the cylindrical chuck 220 may be configured to counteract the propensity for the out-of-plane deformation that would otherwise occur in the bonded structure 100. The cylindrical chuck 220 includes a base element (or connection) 222 that is rigidly connected to a frame of the bonding apparatus 200. A biasing surface 224 receives, holds, and releases the carrier substrates 104 in the manner discussed above, such as via use of vacuum technologies.

[0062] In addition, in response to signal commands from the controller 290, the biasing surface 224 may be varied anywhere from substantially flat 224-1 to some curved maximum 224-2, such as between 5 meters to 25 meters radius of curvature. This is accomplished by way of one or more mechanical actuators 226 and complementary mechanical linkages 230, 232, 234, 236. By way of example, the linkages may include a biasing member 230, such as a rod or the like, that extends generally parallel to the Y-axis and operates to provide a force to maintain the biasing surface 224 upward in the positive Z-axis direction, whilst lateral edges (at substantial extremes in the X-axis) of the biasing surface 224 are urged downward, including substantial components of force in the negative Z-axis direction.

[0063] The linkages also include an adjustment mechanism 226 that operates (preferably in response to the signal commands of the controller 290) to move upwardly and downwardly along the base element 222 in the positive and negative Z-axis directions. The linkages also include first and second biasing arms 232, 234, each coupled at respective proximal ends 232-1, 234-1 to the adjustment mechanism 226, and coupled at respective distal ends 232-2, 234-2 to respective lateral edges of the biasing surface 224. The aforementioned couplings include rotational couplings 236-1 , 236-2, 236-3, 236-4. When the adjustment mechanism 226 moves in the negative Z-axis direction, the proximal ends 232-1, 234-1 of the first and second biasing arms 232, 234 are urged downward (away from the biasing member 230), which urges the lateral edges of the biasing surface 224 downward (in the negative Z-axis direction) and adjusts the biasing surface 224 from substantially flat 224-1 to the curved maximum 224-2. The opposite action is achieved when the adjustment mechanism 226 moves in the positive Z-axis direction in response to signal commands from the controller 290. By way of example, the adjustment mechanism 226 may be implemented using electromechanical technologies (e.g., servo motors, etc.), pneumatic technologies, hydraulic technologies, etc., in such a way as to permit an adjustable amount of cylindrical-shaped out- of-plane curvature of the biasing surface 224 in a Z-axis direction opposite to the direction of the undesirable curvature shown in FIG. 5.

[0064] In operation, the carrier substrate 104 may be placed on the biasing surface 224 such that manipulation of the carrier substrate 104 may be achieved prior to the bonding operation. In particular, the biasing surface 224 induces mechanical stress and/or strain in the carrier substrate 104 to induce a cylindrical-shaped out-of-plane curvature (out of the X-Y plane) in a direction along the Z-axis that counteracts the induced curvature out of the X-Y plane that would occur via the bond front propagation phenomena. For example, the one of stressing and/or straining via the biasing surface 72 may be characterized as mechanically bending the carrier substrate 104 about an axis that is spaced away from the X-Y plane in the Z-axis direction, and that is parallel to the Y-axis, to induce the curvature. In FIG. 9, such axis 240 is located below, and parallel to, the biasing member 230, thereby defining a radius of curvature 242 of the biasing surface 224 and the carrier substrate 104, such that the curvature out of the X-Y plane is a positive direction along the Z-axis (e.g., an upward direction as illustrated).

[0065] After such induced curvature in the carrier substrate 104 is achieved, the bonding process may include the aforementioned step of locating the flexible substrate 102 adjacent the carrier substrate 104 (at the noted gap), via the transfer mechanism 250, while maintaining the at least one of stressing and straining of the carrier substrate 104, via the cylindrical chuck 220.

[0066] With reference to FIG. 10, further details of the transfer mechanism 250 will now be provided. FIG. 10 may be considered to be a side view of some embodiments of the transfer mechanism 250 in which one bond front (a first bond front) is induced and propagates in a direction (e.g., the negative X-axis direction) away from the start line 30 under the pressing mechanism 280. Skilled artisans will appreciate, however, that FIG. 10 may be considered to be a side view of alternative embodiments of the transfer mechanism 250, illustrating the features on only one side of the pressing mechanism 280, with a mirror image of features being employed (but not shown) on the other side of the pressing mechanism 280. In such alternative embodiments, two bond fronts (first and second bond fronts) are induced and propagate in opposite directions from the start line 30.

[0067] As mentioned previously, the transfer mechanism 250 operates to: (i) move the flexible substrate 102 off of the transport mechanism 202, preferably without contacting the flexible substrate 102, and (ii) hold the flexible substrate 102 adjacent the carrier substrate 104 such that the gap, G, is established in a controlled manner. Since the carrier substrate 104 is in a state of cylindrical curvature, the magnitude of the gap G will vary as a function of the particular lateral location (along the X-axis direction) at which the gap G is measured and the degree of curvature of the carrier substrate 104. As also mentioned, the transport mechanism 202 may accomplish the moving, lifting and holding operations using any of the known technologies, such as a combination of ultrasonic and vacuum mechanisms.

[0068] In accordance with preferred embodiments, the transfer mechanism 250 includes a plurality of respective ultrasonic and vacuum mechanisms 252-1, 252-2, 252-3, 252-4, 252-5, etc., on the one side of the pressing mechanism 280 (as shown). In alternative embodiments in which first and second bond fronts are induced (propagating in opposite directions from the start line 30), a corresponding plurality of respective ultrasonic and vacuum mechanisms 254-1, 254-2, 254-3, 254-4, 254-5, etc. (not shown in FIG. 10) are employed in a mirror image on the opposite side of the pressing mechanism 280. Each ultrasonic and vacuum mechanism 252-i, 254-i is individually controllable via signaling from the controller 290 to apply a variable amount of lift and/or release in order to precisely adjust the gap G and to subsequently command the transfer mechanism 250 to synchronously release the non-contact hold on the flexible substrate 102 in synchronization with the propagation of the bond front(s) away from the start line 30.

[0069] With reference to FIGS. 10 and 1 1, each of the respective ultrasonic and vacuum mechanisms 252-1 , 252-2, 252-3, 252-4, 252-5, on the one side of the pressing mechanism 280 (as shown) may be considered to define a respective zone within a first set of zones. Each such zone is generally elongate in the Y-axis direction, and generally narrow in the X- axis direction. Thus, the ultrasonic and vacuum mechanism 252-1 may be considered to provide the lift/release function in a first zone 1 , the ultrasonic and vacuum mechanism 252-2 may be considered to provide the lift/release function in a second zone 2, the ultrasonic and vacuum mechanism 252-3 may be considered to provide the lift/release function in a third zone 3, the ultrasonic and vacuum mechanism 252-4 may be considered to provide the lift/release function in a fourth zone 4, and the ultrasonic and vacuum mechanism 252-5 may be considered to provide the lift/release function in a fifth zone 5.

[0070] When the bi-lateral, mirror arrangement is employed, the ultrasonic and vacuum mechanisms 254-1 , 254-2, 254-3, 254-4, 254-5 may be defined to provide the lift/release functions in first, second, third, fourth, and fifth zones 1 , 2, 3, 4, 5, respectively (a second set of zones), on the opposite side of the pressing mechanism 280. See FIG. 1 1.

[0071] Reference is now made to FIGS. 12A - 12F, which are schematic illustrations of the affect that the signaling from the controller 290 has on the individual ultrasonic and vacuum mechanism 252-i, 254-i in order to synchronously release the non-contact hold on the flexible substrate 102 in synchronization with the propagation of the bond front(s) 34, 36 away from the start line 30.

[0072] As shown in FIG. 12 A, the start line 30 is established via the application of the signal commands from the controller 290 to the pressing mechanism 280 in order to apply the downwardly directed force to at least one of: (i) press the flexible substrate 102 toward the carrier substrate 104, (ii) initiate a substantial localized area of contact (e.g., relatively less elongate than the final start line 30) with the carrier substrate 104, (iii) further press the flexible substrate 102 into contact with the carrier substrate 104 in order to modify the localized area of contact into the elongate start line 30, and (iv) maintain the pressing of the flexible substrate 102 in contact with the carrier substrate 104 for a predetermined time after the first and second bond fronts 34, 36 propagate away from the start line 30.

[0073] As shown in FIG. 12B, as the first bond front 34 (which extends in the Y-axis direction) propagates in the negative X-axis direction through zone 1 (of the first set of zones), the controller 290 operates to command the transfer mechanism 250 to synchronously release the flexible substrate 102 in such zone. Similarly, as the second bond front 36 (which also extends in the Y-axis direction) propagates in the positive X-axis direction through zone 1 (of the second set of zones), the controller 290 operates to command the transfer mechanism 250 to synchronously release the flexible substrate 102 in such zone.

[0074] As shown in FIGS. 12C, 12D, and 12E, as the first and second bond fronts 34, 36 propagate in the negative and positive X-axis directions, respectively, through the zones 2, 3, and 4 (of the first and second sets of zones, respectively), the controller 290 operates to command the transfer mechanism 250 to synchronously (and sequentially) release the flexible substrate 102 in such zones.

[0075] As shown in FIG. 12F, the first and second bond fronts 34, 36 continue to propagate through zone 5 until the flexible substrate 102 and the carrier substrate 104 are fully bonded together. Although not shown in FIG. 12F, the induced curvature in the carrier substrate 104 during the bonding process by the biasing surface 224 is eventually released via signal commands from the controller 290, such that the characteristics of the curvature out of the X- Y plane due to the bond are mitigated. [0076] Turning again to FIG. 1 1 , in accordance with one or more embodiments, the transfer mechanism 250 may further include a plurality of contactless vacuum chucks 256-1 , 256-2, 256-3, 256-4 operating to separately and independently hold the flexible substrate 102 adjacent the carrier substrate 104 at only respective regions proximate to each of four corners of the flexible substrate 102. By way of example, the contactless vacuum chucks 256-1 may be implemented using Bernoulli chucks. The controller 290 operates to command the plurality of contactless chucks 256-1 , 256-2, 256-3, 256-4 to maintain the holding of the flexible substrate 102 adjacent the carrier substrate 104 only in the respective regions proximate to each of four corners of the flexible substrate 102 for a predetermined time after the synchronous releasing of the Nth zone (e.g., the fifth zone 5 of each of the first and second sets of zones).

[0077] As also illustrated in FIG. 1 1 , the controlled, synchronous and sequential release of the flexible substrate 102 via the transfer mechanism 250 may be fine-tuned to maintain desirable substantially convex-shaped first and second bond fronts 34, 36 with reference to the propagation direction.

[0078] With further reference to FIGS. 7 and 1 1 , the bonding apparatus 200 may further include a velocity measuring unit 300 operating to determine at least one of: (i) a first bond front velocity of the first bond front 34 in the first direction, and (ii) a second bond front velocity of the second bond front 36 in the second direction. The at least one first and second bond front velocity is fed back to the controller 290 in order to permit a feedback control loop operating to adjust one or more parameters of the bonding apparatus 200. Indeed, it has been found that such feedback permits simultaneous improvement in the flatness of the bonded structure 100 and the bonding speed.

[0079] For example, the controller 290 may operate to command the transfer mechanism 250 to adjust the gap G of the flexible substrate 102 relative to the carrier substrate 104 as a function of the at least one first and second bond front velocity. Additionally and/or alternatively, the controller 290 may operate to command the transfer mechanism 250 to adjust a timing of the synchronous releasing as a function of the at least one first and second bond front velocity. Additionally and/or alternatively, the controller 290 may operate to command the plurality of contactless chucks 256-i to adjust the predetermined time of maintaining the holding in respective regions proximate to each of the four corners of the flexible substrate 102 as a function of the at least one first and second bond front velocity. Additionally and/or alternatively, the controller 290 may operate to command the cylindrical chuck 220 in order to adjust the radius of curvature 242 in the carrier substrate 104 as a function of the at least one first and second bond front velocity. Additionally and/or alternatively, the controller 290 may operate to command the pressing mechanism 280 to adjust at least one of: (i) a rate at which the leaf-spring deflection element 286 is advanced to initiate the substantial localized area of contact with the carrier substrate 104, (ii) a rate at which the leaf-spring deflection element 286 is advanced to further press the flexible substrate 102 into contact with the carrier substrate 104 in order to modify the localized area of contact into the elongate start line 30, and (iii) the predetermined time after at least one of the first bond front 34 and the second bond front 36 propagate away from the start line 30 as a function of the at least one first and second bond front velocity.

[0080] FIG. 13A is a graphical illustration of a qualitative measure of the out-of-plane deformation (warp) of the bonded structure 100 resulting from use of the aforementioned compensation methodology and/or apparatus. The warp (in um) extends along the Y-axis of the graph, and the radius of curvature (in meters) of the carrier substrate 104 extends along the X-axis of the graph. FIG. 13B shows measurements of the edge gradient, and FIG. 13C shows measurements of the comer gradient. The edge gradient is a metric of warpage, specifically a slope of the warp within a region (e.g., about 50 mms) directly adjacent to an edge of the bonded structure 100. A corner gradient is another metric of warpage, specifically the slope of the warp within a region (e.g., 50 mms) directly adjacent to a corner the bonded structure 100.

[0081] FIGS. 14A, 14B, 14C are graphical illustrations of further qualitative measures of the bonded structure 100 resulting from use of the aforementioned compensation methodology and/or apparatus. In FIG. 14A, the out-of-plane deformation (warp) extends along the Y-axis of the graph, and the bond speed (in mm per second) extends along the X-axis of the graph. FIG. 14A shows measurements of the aforementioned warp as a function of bond speed, FIG. 14B shows measurements of the edge gradient, and FIG. 13C shows measurements of the corner gradient.

[0082] Although the disclosure herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the embodiments herein. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present application.

[0083] In accordance with one or more further embodiments of the disclosure, a number of specific combinations of elements are provided below.

[0084] Embodiment 1 : A method includes: holding, without contacting, a flexible substrate adjacent a carrier substrate such that a gap therebetween is established, wherein the carrier substrate comprises a sheet of material, a length dimension in an X-axis, a width dimension in a Y-axis, and a thickness dimension in a Z-axis, where the X-axis and Y-axis define an X- Y plane, and the flexible substrate comprises a sheet of material, a length dimension in the X- axis, a width dimension in the Y-axis, and a thickness dimension in the Z-axis, wherein at least one of: (i) a flexibility of the flexible substrate is substantially more flexible than a flexibility of the carrier substrate, and (ii) the thickness of the flexible substrate is substantially less than a thickness of the carrier substrate; inducing a bond between the flexible substrate and the carrier substrate, wherein the bond initiates at an elongate start line that extends substantially along a line parallel to the Y-axis such that a first bond front propagates away from the start line in a first direction substantially transverse to the start line and the Y-axis; and synchronously releasing the non-contact hold on the flexible substrate with the propagation of the first bond front away from the start line.

[0085] Embodiment 2: A method comprising the elements of Embodiment 1, and further comprising: determining a first bond front velocity of the first bond front in the first direction; and adjusting the gap of the flexible substrate relative to the carrier substrate as a function of the first bond front velocity.

[0086] Embodiment 3: A method comprising the elements of Embodiments 1 or 2, wherein: the synchronous releasing includes sequentially releasing the non-contact hold on the flexible substrate in a first set of respective zones as the first bond front propagates through such first set of respective zones; the first set of respective zones each extend parallel to the Y-axis and each are sequentially arranged next to one another in the first direction parallel to the X-axis; and the direction of the propagation of the first bond front is parallel to the X-axis.

[0087] Embodiment 4: A method comprising the elements of Embodiments 1 , 2, or 3, wherein: the inducing of the bond between the flexible substrate and the carrier substrate includes a second bond front that propagates away from the start line in a second direction substantially opposite to the first direction and transverse to the start line and the Y-axis; the synchronous releasing includes sequentially releasing the non-contact hold on the flexible substrate in a second set of respective zones as the second bond front propagates through such second set of respective zones; the second set of respective zones each extend parallel to the Y-axis and each are sequentially arranged next to one another in the second direction parallel to the X-axis; and the direction of the propagation of the second bond front is parallel to the X-axis.

[0088] Embodiment 5 : A method comprising the elements of Embodiments 1, 2, 3, or 4, further comprising: determining at least one of a first bond front velocity of the first bond front in the first direction, and a second bond front velocity of the second bond front in the second direction; and adjusting a timing of the synchronous releasing as a function of at least one of the first bond front velocity and the second bond front velocity.

[0089] Embodiment 6: A method comprising the elements of Embodiments 1 , 2, 3, 4, or 5, wherein: the first and second sets of respective zones each includes n zones, n = 1, 2, 3, . . . N, arranged in respective sequences in the respective first and second directions away from the start line; and the holding, without contacting, the flexible substrate adjacent the carrier substrate includes maintaining the holding only in respective regions proximate to each of four corners of the flexible substrate for a predetermined time after the synchronous releasing of the Nth zones of each of the first and second sets of respective zones.

[0090] Embodiment 7: A method comprising the elements of Embodiments 1, 2, 3, 4, 5, or 6, further comprising: determining at least one of a first bond front velocity of the first bond front in the first direction, and a second bond front velocity of the second bond front in the second direction; and adjusting the predetermined time of maintaining the holding in respective regions proximate to each of four corners of the flexible substrate as a function of at least one of the first bond front velocity and the second bond front velocity.

[0091] Embodiment 8: A method comprising the elements of Embodiments 1, 2, 3, 4, 5, 6, or 7, further comprising mechanically bending the carrier substrate to induce a cylindrical curvature in the carrier substrate out of the X-Y plane in a first direction along the Z-axis prior to inducing the bond between the flexible substrate and the carrier substrate along the start line, such that the characteristics of the first bond front tends to cause the bonded flexible substrate and the carrier substrate to curve out of the X-Y plane in a second direction along the Z-axis, opposite to the first direction.

[0092] Embodiment 9: A method comprising the elements of Embodiments 1 , 2, 3, 4, 5, 6, 7, or 8, further comprising: determining a first bond front velocity of the first bond front in the first direction; and adjusting a radius of curvature of the cylindrical curvature in the carrier substrate as a function of the first bond front velocity.

[0093] Embodiment 10: A method comprising the elements of Embodiments 1 , 2, 3, 4, 5, 6, 7, 8, or 9, further comprising advancing a leaf-spring deflection element against the flexible substrate in order to: press the flexible substrate toward the carrier substrate, initiate a substantial localized area of contact with the carrier substrate, further press the flexible substrate into contact with the carrier substrate in order to modify the localized area of contact into the elongate start line, and maintain the pressing the flexible substrate in contact with the carrier substrate for a predetermined time after the first bond front propagates away from the start line.

[0094] Embodiment 1 1 : A method comprising the elements of Embodiments 1 , 2, 3, 4, 5, 6, 7, 8, 9, or 10, further comprising: determining a first bond front velocity of the first bond front in the first direction; and adjusting the predetermined time after the first bond front propagates away from the start line as a function of first bond front velocity.

[0095] Embodiment 12: A method comprising the elements of Embodiments 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, or 1 1, wherein at least one of: the flexible substrate comprises glass; the flexible substrate comprises a thickness of one of: (i) from about 50 um to about 300 um, and (ii) from about 100 um to about 200 um; the flexible substrate comprises an area defined by one of: (i) a length of greater than about 500 mm and a width of greater than about 500 mm; and (ii) a length of about 1100 mm and a width of about 1300 mm; the flexible substrate comprises at least one of: a density of about 2.3 - 2.5 g/cc, a Young's Modulus of about 70 - 80 GPa; a Poisson Ratio of about 0.20 - 0.25, and a minimum bend radius of about 185 - 370 mm; the carrier substrate comprises glass; and the carrier substrate comprises a thickness of from about 400 to about 1000 um.

[0096] Embodiment 13 : A method comprising the elements of Embodiments 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1, or 12, wherein an amount of deformation out of the X-Y plane after bonding is less than or equal to at least one of: (i) about 200 um; (ii) about 100 um; (iii) about 75 um; and (iii) about 50 um.

[0097] Embodiment 14: An apparatus, comprising: a carrier substrate transport mechanism operating to move a carrier substrate from a loading zone to a bonding zone, where the carrier substrate is formed from a sheet of material, the carrier substrate having a length dimension in an X-axis, a width dimension in a Y-axis, and a thickness dimension in a Z-axis, where the X-axis and Y-axis define an X-Y plane; a chuck operating to hold the carrier substrate in the bonding zone; a flexible substrate transport mechanism operating to move a flexible substrate from a further loading zone to the bonding zone, where the flexible substrate is formed from a sheet of material, the flexible substrate having a length dimension in the X-axis, a width dimension in the Y-axis, and a thickness dimension in the Z-axis, wherein at least one of: (i) a flexibility of the flexible substrate is substantially more flexible than a flexibility of the carrier substrate, and (ii) the thickness of the flexible substrate is substantially less than a thickness of the carrier substrate; a transfer mechanism operating to: (i) move the flexible substrate off of the transport mechanism without contacting the flexible substrate, and (ii) hold the flexible substrate adjacent the carrier substrate such that a gap therebetween is established; a pressing mechanism operating to induce a bond between the flexible substrate and the carrier substrate, wherein the bond initiates at an elongate start line that extends substantially along a line parallel to the Y-axis such that a first bond front propagates away from the start line in a first direction substantially transverse to the start line and the Y-axis; and a controller operating to command the transfer mechanism to synchronously release the non-contact hold on the flexible substrate with the propagation of the first bond front away from the start line.

[0098] Embodiment 15: An apparatus, comprising the elements of Embodiment 14, further comprising: a velocity measuring unit operating to determine a first bond front velocity of the first bond front in the first direction, wherein the controller operates to command the transfer mechanism to adjust the gap of the flexible substrate relative to the carrier substrate as a function of the first bond front velocity.

[0099] Embodiment 16: An apparatus, comprising the elements of Embodiments 14 or 15, wherein: the controller operates to command the transfer mechanism to effect the synchronous releasing to include sequentially releasing the non-contact hold on the flexible substrate in a first set of respective zones as the first bond front propagates through such first set of respective zones; the first set of respective zones each extend parallel to the Y-axis and each are sequentially arranged next to one another in the first direction parallel to the X-axis; and the direction of the propagation of the first bond front is parallel to the X-axis.

[00100] Embodiment 17: An apparatus, comprising the elements of Embodiments 14, 15 or 16, wherein: the inducing of the bond between the flexible substrate and the carrier substrate includes a second bond front that propagates away from the start line in a second direction substantially opposite to the first direction and transverse to the start line and the Y- axis; the controller operates to command the transfer mechanism to effect the synchronous releasing to include sequentially releasing the non-contact hold on the flexible substrate in a second set of respective zones as the second bond front propagates through such second set of respective zones; the second set of respective zones each extend parallel to the Y-axis and each are sequentially arranged next to one another in the second direction parallel to the X- axis; and the direction of the propagation of the second bond front is parallel to the X-axis.

[00101] Embodiment 18: An apparatus, comprising the elements of Embodiments 14, 15, 16, or 17, further comprising: a velocity measuring unit operating to determine a first bond front velocity of the first bond front in the first direction, and a second bond front velocity of the second bond front in the second direction, wherein the controller operates to command the transfer mechanism to adjust a timing of the synchronous releasing as a function of at least one of the first bond front velocity and the second bond front velocity.

[00102] Embodiment 19: An apparatus, comprising the elements of Embodiments 14, 15, 16, 17, or 18, wherein: the first and second sets of respective zones each includes n zones, n = 1 , 2, 3, . . . N, arranged in respective sequences in the respective first and second directions away from the start line; the apparatus further comprises a plurality of contactless vacuum chucks operating to separately and independently hold the flexible substrate adjacent the carrier substrate at only respective regions proximate to each of four comers of the flexible substrate; and wherein the controller operates to command the plurality of contactless chucks to effect the holding, without contacting, the flexible substrate adjacent the carrier substrate to include maintaining the holding only in the respective regions proximate to each of four corners of the flexible substrate for a predetermined time after the synchronous releasing of the Nth zones of each of the first and second sets of respective zones.

[00103] Embodiment 20: An apparatus, comprising the elements of Embodiments 14, 15, 16, 17, 18, or 19, further comprising: a velocity measuring unit operating to determine a first bond front velocity of the first bond front in the first direction, and a second bond front velocity of the second bond front in the second direction, wherein the controller operates to command the plurality of contactless chucks to adjust the predetermined time of maintaining the holding in respective regions proximate to each of four corners of the flexible substrate as a function of at least one of the first bond front velocity and the second bond front velocity.

[00104] Embodiment 21 : An apparatus, comprising the elements of Embodiments 14, 15, 16, 17, 18, 19, or 20, wherein the chuck operates to mechanically bend the carrier substrate to induce a cylindrical curvature in the carrier substrate out of the X-Y plane in a first direction along the Z-axis prior to inducing the bond between the flexible substrate and the carrier substrate along the start line, such that the characteristics of the first bond front tends to cause the bonded flexible substrate and the carrier substrate to curve out of the X-Y plane in a second direction along the Z-axis, opposite to the first direction.

[00105] Embodiment 22: An apparatus, comprising the elements of Embodiments 14, 15, 16, 17, 18, 19, 20 or 21, further comprising: a velocity measuring unit operating to determine a first bond front velocity of the first bond front in the first direction; and wherein the controller operates to command the chuck in order to adjust a radius of curvature of the cylindrical curvature in the carrier substrate as a function of the first bond front velocity.

[00106] Embodiment 23: An apparatus, comprising the elements of Embodiments 14, 15, 16, 17, 18, 19, 20, 21, or 22, wherein the pressing mechanism includes a leaf-spring deflection element operating to advance against the flexible substrate in order to: press the flexible substrate toward the carrier substrate, initiate a substantial localized area of contact with the carrier substrate, further press the flexible substrate into contact with the carrier substrate in order to modify the localized area of contact into the elongate start line, and maintain the pressing the flexible substrate in contact with the carrier substrate for a predetermined time after the first bond front propagates away from the start line.

[00107] Embodiment 24: An apparatus, comprising the elements of Embodiments 14, 15, 16, 17, 18, 19, 20, 21, 22, or 23, further comprising: a velocity measuring unit operating to determine a first bond front velocity of the first bond front in the first direction; and wherein the controller operates to command the leaf-spring deflection element to adjust at least one of: (i) a rate at which the leaf-spring deflection element is advanced to initiate the substantial localized area of contact with the carrier substrate, (ii) a rate at which the leaf- spring deflection element is advanced to further press the flexible substrate into contact with the carrier substrate in order to modify the localized area of contact into the elongate start line, and (iii) the predetermined time after the first bond front propagates away from the start line as a function of first bond front velocity.

[00108] Embodiment 25 : An apparatus, comprising the elements of Embodiments 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24, wherein at least one of: the flexible substrate is formed from glass; the flexible substrate comprises a thickness of one of: (i) from about 50 um to about 300 um, and (ii) from about 100 um to about 200 um; the flexible substrate comprises an area defined by one of: (i) a length of greater than about 500 mm and a width of greater than about 500 mm; and (ii) a length of about 1 100 mm and a width of about 1300 mm; the flexible substrate comprises at least one of: a density of about 2.3 - 2.5 g/cc, a Young's Modulus of about 70 - 80 GPa; a Poisson Ratio of about 0.20 - 0.25, and a minimum bend radius of about 185 - 370 mm; the carrier substrate is formed from glass; and the carrier substrate comprises a thickness of from about 400 to about 1000 um.

[00109] Embodiment 26: An apparatus, comprising the elements of Embodiments 14, 15, 16, 17, 18, 19, 20, 21 , 22, 23, 24, or 25, wherein an amount of deformation out of the X-Y plane after bonding is less than or equal to at least one of: (i) about 200 um; (ii) about 100 um; (iii) about 75 um; and (iii) about 50 um.