WO2016141119A1

WO2016141119A1 - Methods and apparatus for initiating debonding between two sheets of an assembly

Info

Publication number: WO2016141119A1
Application number: PCT/US2016/020566
Authority: WO
Inventors: Raymond Charles Cady; Allan James DOIG; Timothy Michael Miller
Original assignee: Corning Incorporated
Priority date: 2015-03-04
Filing date: 2016-03-03
Publication date: 2016-09-09
Also published as: JP2018514479A; TW201636221A; SG11201707090YA; KR20170125868A; CN107567384A; EP3265313A1

Abstract

Initiating separation of a sheet assembly (2) made of a first sheet (10) and a second sheet (20), the first sheet having an edge (14) and the second sheet being removably bonded to the first sheet. The method including relatively moving the sheet assembly and an engagement member (30) with respect to one another, so as to contact the edge with an engagement surface of the engagement member. Applying a first force to the edge, with the engagement surface, and applying a second force to the second sheet, wherein the second force is opposite to the first force, whereby the application of the first and second forces causes an initial separation of at least one portion (4) of the first sheet from a corresponding portion of the second sheet that was bonded thereto.

Description

METHODS AND APPARATUS FOR INITIATING DEBONDING BETWEEN TWO

SHEETS OF AN ASSEMBLY

BACKGROUND

Cross-Reference To Related Applications

[0001] This application claims the benefit of priority under 35 U.S.C. § 1 19 of U.S. Provisional Application Serial No. 62/128396 filed on March 4, 2015, the content of which is relied upon and incorporated herein by reference in its entirety.

Field of the invention

[0002] The present invention is directed to methods and apparatuses for initiating debonding (i.e., separation) between two sheets of a sheet assembly and, in particular to methods and apparatuses for initiating debonding between a thin sheet and a carrier.

Technical Background

[0003] To process ultra-thin glass (i.e., glass having a thickness of 300 microns or less) in existing consumer electronic fabs designed for thicker glass (on the order of 400 microns or greater), a carrier is used to support the ultra-thin glass. The carrier is bonded to the ultra-thin glass with a temporary bonding agent so that the ultra-thin glass and carrier stay bonded to one another during processing of electronic device structures, but allow the ultra-thin glass and carrier to be separated from one another after the processing is complete. To peel the carrier from the ultra-thin glass, a separation is initiated between them. One current method of initiating the separation is to force a thin blade (e.g., a razor blade) between the carrier and the ultra-thin glass. However, this method of initiating separation can cause damage to the carrier and/or the ultra-thin glass both directly by the blade, and in the form of further damage by chips of glass that are generated during the initiation process.

SUMMARY

[0004] According to the present disclosure, there are described methods and apparatuses that can initiate a separation between two sheets of an assembly, for example an ultra-thin glass and a carrier, without damaging the sheets. According to one aspect, separation is initiated by applying a lifting force on an edge of one sheet, wherein the lifting force has a component in a direction normal to a major surface of the sheet and away from the assembly.

[0005] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the various aspects as exemplified in the written description and the appended drawings. It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the various aspects, and are intended to provide an overview or framework to understanding the nature and character of the invention as it is claimed.

[0006] The accompanying drawings are included to provide a further

understanding of principles of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description serve to explain, by way of example, principles and operation of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 is a schematic side view of a sheet assembly.

[0008] FIG. 1 A is a schematic side view of a sheet according to one embodiment.

[0009] FIG. 1 B is a schematic side view of a sheet according to another embodiment.

[0010] FIG. 2 is a schematic plan view of an engagement member according to one embodiment, wherein a sheet assembly is shown in cut-away view.

[0011] FIG. 2A is a schematic plan view of an engagement member according to another embodiment, wherein a sheet assembly is shown in cut-away view.

[0012] FIG. 2B is a schematic plan view of an engagement member according to yet another embodiment.

[0013] FIG. 3 is a schematic side view of an engagement member, according to FIG. 2, during initiation of debonding.

[0014] FIG. 4 is a schematic plan view of an engagement member and a sheet assembly after debonding has been initiated. DETAILED DESCRIPTION

[0015] In the following detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth to provide a thorough understanding of various principles of the present invention. However, it will be apparent to one having ordinary skill in the art, having had the benefit of the present disclosure, that the present invention may be practiced in other

embodiments that depart from the specific details disclosed herein. Moreover, descriptions of well-known devices, methods and materials may be omitted so as not to obscure the description of various principles of the present invention. Finally, wherever applicable, like reference numerals refer to like elements.

[0016] Ranges can be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0017] Directional terms as used herein— for example up, down, right, left, front, back, top, bottom— are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0018] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; the number or type of embodiments described in the specification.

[0019] As used herein, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a "component" includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0020] To process thin sheets, i.e., those having a thickness of 300 microns or less, for example 300, 275, 250, 225, 200, 175, 150, 125, 100, 75, 50, 20, or 10 microns, in existing equipment designed for processing thicker sheets, the thin sheets are temporarily bonded with a carrier to form a sheet assembly having a thickness appropriate for the particular processing equipment. The thin sheet may be a thin silicate glass sheet, for example, on which electronic devices are to be built, wherein the electronic device benefits from the high temperature processing capability and hermeticity of the silicate glass (for simplicity sake, the term "glass sheet" is used herein to refer to a silicate glass sheet). The thin sheet is bonded to the carrier with a temporary bonding agent that allows the thin sheet and carrier to be separated from one another after the processing is complete. The sheet assembly is processed, for example to fabricate electronic device components onto the thin sheet, and then the thin sheet is removed from the carrier. To remove the thin sheet from the carrier, when the thin sheet is a glass sheet, it is beneficial to initiate a local debonding, i.e., at an area smaller than the entire area over which the sheets were bonded for the processing. Once debonding has been initiated, the thin glass sheet can be peeled from the carrier using mechanical levers or other fixtures, for example. By initiating debonding on a portion of the area over which the thin glass sheet is bonded to the carrier, there is a reduced risk of breaking the thin glass sheet than when attempting to peel the thin glass sheet from the carrier without debonding initiation. That is, the force to initiate debonding is greater than that to maintain peeling of the thin sheet from the carrier after peeling has started. Thus, if one were to attempt to initiate debonding and peel in one motion, the higher force for initiation would also be used to maintain peeling, which would increase the risk of breaking or otherwise damaging the thin sheet or carrier. On the other hand, when firstly initiating debonding and then peeling in two separate actions, the debonding initiation can be performed at the higher required force, and the peeling can be performed at a lower force, thereby reducing the risk of breaking or otherwise damaging the thin sheet or carrier. Further, separation of the sheets is initiated by applying a lifting force on an edge of one sheet, wherein the lifting force has a component in a direction normal to a major surface of the sheet and away from the assembly, and the lifting force is applied by an engagement surface that does not damage the sheet, or leave a residue thereon. Accordingly, two sheets of an assembly, for example an ultra-thin glass and a carrier, can be separated without damaging the sheets, whereby the carrier can be used again in another process, and the electronic device built on the ultra-thin glass is not damaged, resulting in a higher yield for the device manufacturer.

[0021] Generally, a method of initiating debonding (separation) of a sheet assembly includes relatively moving a sheet assembly and an engagement member with respect to one another. The sheet assembly includes a first sheet and a second sheet, the first sheet having a first major surface, a second major surface opposite the first major surface, and an edge disposed between and adjoining the first major surface and the second major surface. The second sheet is removably bonded to the second major surface. The engagement member has an engagement surface, which is contacted with the edge so as to apply a first force to the edge, the first force including a force component in a first direction that is normal to the first major surface. At the same time, the second sheet is held by a second force having a force component in a second direction that is opposite to the first direction, whereby the application of the first and second forces causes an initial debonding (separation) of at least one portion of the first sheet from a corresponding portion of the second sheet that was bonded thereto.

[0022] An apparatus for initiating the debonding (separation) of a sheet assembly includes an engagement member having a compliant engagement surface, and a planar support surface for holding the sheet assembly. In one embodiment, the planar support surface is disposed relative to the engagement member so that the plane in which the planar support surface lies intersects the engagement surface in a line segment. With this arrangement, the sheet assembly (or the engagement member) can be moved in a simple manner so that an edge of an appropriate one of the sheets contacts the engagement surface that is used to initiate debonding (separation) of the sheets. That is, with the above-described arrangement of the support relative to the engagement member, the engagement member and sheet assembly can be moved relative to one another with a simple linear or planar motion; one degree of freedom is fixed so as to facilitate alignment between the sheet assembly and the engagement member. In other embodiments, relative positions of the engagement member, engagement surface, and sheet assembly can be altered (including in three dimensions) to bring the engagement surface and sheet assembly (in particular an edge of an appropriate one of the sheets in the assembly) into contact with each other in the desired manner.

[0023] As shown in FIG. 1 , one embodiment of a sheet assembly 2 includes a first sheet 10 temporarily or removably bonded to a second sheet 20. There are many different manners of temporarily bonding the first sheet 10 to the second sheet 20 that are known in the art, and such are not particularly limited for use with the concepts of the present disclosure, for example there may be used: a silicone material between the first and second sheets 10, 20 - see EP2025650; a surface modification layer on either one or both of the first and second sheets 10, 20 - see US2014-0170378; a treatment of the surfaces that are temporarily bonded - see KR2013044774; or a variety of other materials and bonding agents known in the art. According to other embodiments, there may be included more than two sheets in the sheet assembly. For example, a sheet assembly may include: multiple thin sheets stacked together and temporarily bonded on one carrier; or a stack having a first thin sheet temporarily bonded to a first carrier, a second thin sheet temporarily bonded to a second carrier, wherein the first and second thin sheets are permanently bonded to one another as part of an electronic device. In the latter case, the two thin sheets may have been separately processed on their respective carriers to form, for example, a TFT backplane, and a color filter, for an LCD display. The two thin sheets are then permanently bonded to one another around their perimeters to form the LCD panel. Upon completion of the LCD panel, the two carriers are removed therefrom. In all of the above situations, the debonding initiation described herein may be used to facilitate peeling of one sheet from another.

[0024] The first sheet 10 has a first major surface 1 1 , a second major surface 12 opposite and generally parallel to the first major surface 1 1 , an edge 14, and a thickness 16. The first edge 14 is disposed between and adjoins both the first major surface 1 1 and the second major surface 12. The first edge 14 is present around the entire periphery of the first sheet 10. As shown in FIG. 1 , the first edge 14 is square with the first major surface 1 1 and the second major surface 12, but such need not be the case. Alternatively the first edge 14 may be radiused, or rounded,

(asymmetrically or symmetrically), as shown in FIG. 1 A, or chamfered (asymmetrically or symmetrically), as shown in FIG. 1 B. The first sheet may be either a thin glass sheet, or a carrier. When the first sheet is the carrier, it will have a thickness of 200 microns or greater. When the first sheet is the thin glass sheet, it will have a thickness of 300 microns or smaller. The first sheet 10 may be made of any suitable material, including glass, for example, a silicate glass, a boro-silicate glass, or an alumino-boro-silicate glass, a glass ceramic, silicon, or soda-lime-silicate glass. The first sheet may be alkali-free glass, or an alkali-containing glass.

Additionally, the first sheet 10 may be an interposer having a plurality of holes extending into or through its thickness. Additionally, the first sheet 10 may have any suitable size, for example, Gen1 (300x400 mm), Gen2 (360x465 mm), Gen3, Gen4, Gen5 (1 100x1300 mm), Gen6, Gen7, Gen8 (2200x2500 mm), or Genl O.

[0025] The second sheet 20 has a third major surface 23, a fourth major surface 24 opposite and generally parallel to the third major surface 23, a second edge 22, and a thickness 26. The second edge 22 is disposed between and adjoins both the third major surface 23 and the fourth major surface 24. The second edge 22 is present around the entire periphery of the second sheet 20. The second edge 22 may be coincident (i.e., even or aligned) with the first edge 14 either at a portion or along the entirety thereof. In the latter case, the first sheet 10 and second sheet 20 will be of the same size. Alternatively, the first sheet 10 may be larger than the second sheet 20, or smaller than the second sheet 20. Accordingly, in some instances the second edge 22 may be offset 3 from the first edge 14. As shown in FIG. 1 , the offset 3 is in a direction 5 but, alternatively, the offset 3 may be in the opposite direction 7. The offset 3 may be the same around the entire periphery of the sheet assembly 2, but such need not be the case. In order to provide for reuse of a carrier (for example the first sheet 10) the thin sheet (for example the second sheet 20) should have an offset that prevents deposition onto the carrier of material that cannot easily be removed, for example, the offset 3 can be < 3 mm in direction 5. If the offset is too large, then materials from the electronic device processing will be deposited onto the carrier and may hinder reuse of the carrier. As shown in FIG. 1 , the second edge 22 is square with the third major surface 23 and the fourth major surface 24, but such need not be the case. Alternatively the second edge 22 may be radiused, or rounded,

(asymmetrically or symmetrically), as shown in FIG. 1 A, or chamfered

(asymmetrically or symmetrically), as shown in FIG. 1 B. The second sheet may be either a thin glass sheet, or a carrier. When the second sheet is the carrier, it will have a thickness of 200 microns or greater. When the second sheet is the thin glass sheet, it will have a thickness of 300 microns or smaller. The thickness 26 may be either the same as, greater than, or less than, the thickness 16. The second sheet may be made of any suitable material, including glass, for example a silicate glass, a boro-silicate glass, or an alumino-boro-silicate glass, a glass ceramic, silicon, or soda-lime-silicate glass. The second sheet may be alkali-free glass, or an alkali- containing glass. Additionally, the second sheet 20 may be an interposer having a plurality of holes extending into or through its thickness. When the second sheet 20 is a thin sheet, it may be a single thin sheet, or may be part of a larger stack of sheets that make a device, for example a consumer electronic device, for example a display. When part of a stack of sheets, another sheet in the stack may also be temporarily bonded to a carrier to be removed from that sheet.

[0026] FIG. 2 shows an apparatus 100 for initiating debonding, or separation, between the first and second sheets 10, 20. As shown, the apparatus includes an engagement member 30 and a support 40.

[0027] In FIG. 2, the engagement member 30 is shown as a circular wheel that includes a core 31 , an engagement surface 32, and a diameter 36 (of the core 31 ). Also, the engagement member 30 is mounted for rotation about an axis 34. The core 31 may be made of any suitable rigid material, which is not particularly limited, for example, metal, or plastic.

[0028] The engagement surface 32 is made of a material that facilitates engaging the edge of one of the first and second sheets 10, 20 with a suitable amount of friction so as to produce a force large enough to initiate debonding. Because the thickness of the sheets is on the order of less than 1 mm, there is a small area for developing the amount of friction suitable to initiate debonding, whereby the selection of a suitable material is important. Also, the material of the engagement surface 32 may provide for contact with the edge of one of the sheets 10, 20 with any one or more of:

minimizing or leaving no damage; leaving minimal or no particles; leaving minimal or no residue, on it, each of which facilitate reusing that sheet 10, 20 in another process. Accordingly, the engagement surface 32 is made of a compliant material, for example rubber, for example butyl rubber, Nylon, or urethane. For example, a simple butyl-rubber O-ring around a small shaft can be suitable. The Durometer of the material can be about 50 - 90, for example, about 70. If the Durometer of the material is too low, and the offset 3 is small, the engagement surface 32 tends to contact both the first sheet 10 and the second sheet 20, whereby the sheets 10, 20 are not separated from one another. A material having a Durometer of less than 50, with an offset 3 of < 1 mm, was attempted, but did not successfully separate first and second sheets bonded in the manner of US2014-0170378, and having a bond energy of 400-800 mJ/m² between the first and second sheet. If the Durometer of the material is too high, then it is difficult to generate enough friction between the engagement surface and the edge, and consequently enough normal force component to initiate debonding of the sheets. Durometers other than those described above may work with an adjustment of the force with which the sheet assembly 2 is pressed against the engagement surface 32, together with an adjustment of the diameter 36. In other aspects, the material is chosen to leave a minimal amount, or no, particles on the sheets; in this case, the material is chosen so as to be non-friable, for example butyl rubber, Nylon, or urethane, may be used. In other aspects, the material is chosen to leave a minimal amount, or no residue on the sheets; in this case butyl rubber, Nylon, or urethane, for example, may be used. Instead of having a core 31 and a separate engagement surface 32, the engagement member 30 may be made of all the same material, as a monolith, wherein the material is one suitable for engaging one of the sheets 10, 20, as described above. The engagement surface 32 may be provided around the entire circumference of the engagement member 30, as shown in FIG. 2. According to other aspects, the engagement surface 32 may be disposed in separate segments disposed

discontinuously around the circumference of the engagement member 30, as shown in FIG. 2A, for example. According to still other aspects, the engagement surface 32 may be disposed in one or more separate segments 32A, 32 B across the width of the engagement member 30 (wherein the width of the engagement member 30 is measured along a line parallel to dashed line 44 in FIG. 2 and on the engagement member 30), as shown in FIG. 2B, for example; in this case, the segments may be either continuous around the circumference as are segments 32A, or discontinuous around the circumference as are segments 32B. Although only one segment 32A is shown on any particular line across the width of the engagement member 30, any suitable number of segments 32A may be so disposed. [0029] The diameter 36 of the engagement member 30 is the diameter of the core 31 , and is chosen based on the thickness of the sheets 10, 20 to be separated. When the sheets 10, 20 are on the order of 100 to 500 microns, the diameter 36 may be in the range of from ¼ to ½ inch (6.3 to 12.7 mm, for example about 10 mm), for example. The engagement surface 32 then extends from the outer surface of the core, wherein in some examples the amount of extension may be from about 1 .1 mm to about 2.4 mm (about 3/64 to about 3/32 of an inch). Generally, a smaller diameter 36 is preferred, as such provides good access to the edge 14 of the first sheet 10, and provides a built-in force-limiting mechanism as discussed below in connection with the method of initiating debonding.

[0030] The engagement member 30 is coupled to a motor 37 which rotates the engagement member 30, together with engagement surface 32, in the direction of arrow 33. A controller 38 is coupled to the motor 37 to control the rotation of the engagement member. The controller 38 may be a central processing unit, a programmable logic controller, or other suitable device, whose operation will be described below in connection with the manner of operating engagement member 32 to initiate separation between the first and second sheets 10, 20.

[0031] Referring to FIG. 2, the support 40 includes a planar support surface 42 for supporting the sheet assembly 2, so that the sheet assembly 2 may be presented to the engagement member 30 to initiate debonding of the first and second sheets 10, 20. The support 40 is disposed relative to the engagement member 30 so that the plane in which the planar support surface 42 lies intersects the engagement member 30 in a line segment 44 (a dashed line in FIG. 2). With this arrangement, the sheet assembly 2 (or the engagement member 30) can be moved in a simple manner so that an edge of an appropriate one of the sheets 10, 20 contacts the engagement surface 32, which, as will be discussed later, is used to initiate separation of the sheets 1 0, 20. That is, with the above-described arrangement of the support 40 relative to the engagement member 30, the engagement member 30 and sheet assembly 2 can be moved relative to one another with a simple linear or planar motion; one degree of freedom is fixed so as to facilitate alignment between the sheet assembly 2 and the engagement member 30. For example, as shown in FIG. 2, the sheet assembly 2 may undergo simple linear motion in direction 7 toward and into contact with the engagement member 30. According to some examples, the axis 34 of the engagement member 30 may be mounted in a stationary position, and the sheet assembly 2 moved into a position defined by stops (not shown) on the support 40, whereby the stops appropriately position the sheet assembly relative to the engagement surface 32. According to other examples, the support 40, and/or the axis of rotation 34 or the engagement member 30, may be movable in three dimensions to facilitate appropriate alignment of an edge of the sheet to be engaged with the engagement member, e.g. , so that the first major surface 1 1 is positioned at a suitable offset 71 relative to the axis of rotation 34. The movement of the support and/or the axis of rotation may be controlled by controller 38. The support 40 may be a pressure /vacuum table, for example, wherein the support 40 provides fluid pressure to float the sheet assembly 2 for movement into alignment with the engagement member 30, and then provides vacuum for holding the sheet assembly 2 in that aligned position.

[0032] With reference to FIGS. 3 and 4, a method of initiating separation of the sheet assembly 2, i.e., initiating debonding between the first sheet 10 and the second sheet 20, will now be described.

[0033] The sheet assembly 2 is supported by the planar support surface 42 of the support 40 by, for example, fluid issuing from the planar support surface 42. In such a manner, the sheet assembly 2 may readily be moved from the left side of FIG. 3, in the direction 7 toward and into contact, or nearly into contact, with the engagement surface 32. When the sheet assembly is in a suitable position relative to the engagement surface 32, the support member can then be switched to vacuum mode to hold the sheet assembly 2 to the planar support surface 42.

[0034] As is seen from FIG. 3, the engagement member 30 may be a circular wheel, and the axis of rotation 34 is offset from the first major surface 1 1 by a distance 71 in the first direction 61 , and is offset from the planar support surface 42 by a distance 72 in the first direction, wherein the distance 72 is greater than or equal to the thickness of the sheet assembly 2 in which it is desired to initiate debonding, wherein the thickness of the sheet assembly 2 is the sum of the thickness 16 of the first sheet 10, the thickness 26 of the second sheet 20, and the thickness of any bonding material therebetween. In cases where the bonding material has a negligible thickness, as in the bonding materials of US2014-0170378, its thickness can be ignored when calculating the thickness of the sheet assembly 2 and, subsequently, the amount of offset distance 72. The distance 72 can be adjusted to fit the expected thickness of the sheet assembly 2 for which debonding initiation is desired, and this distance will depend not only upon the thickness of the sheet assembly 2, but also upon the distance between the engagement surface 32 and the axis of rotation 34 (in this case, the diameter 36 of the engagement member 30). More specifically, the edge of the sheet to be lifted (as shown in FIG. 3, edge 14 of first sheet 10) should be placed a lateral distance (in the direction 7) from the axis of rotation 34 by a distance less than the diameter 36. Accordingly, the engagement surface 32 contacts the edge 14 of only the first sheet 10, so that the first sheet 10 may be lifted relative to the second sheet 20. According to some examples, with a second sheet on the order of 100 microns, and a first sheet on the order of 400 microns, the first sheet 10 may be lifted from about 1 to about 3 mm, and will typically be the same as the distance between the major surface 1 1 and the axis of rotation 34, i.e., the offset distance 71 .

[0035] Then, to initiate debonding, the engagement member 30 is rotated by motor 37 so as to turn in the direction 33. A suitable speed of rotation may be on the order of 1 -20 revolutions per minute (RPM). With slower speeds in the range, it is easier to generate the amount of friction desirable for engaging an edge of a sheet, and to generate an appropriate amount of normal force component. Also, with slower speeds in the range it is easier to control the debonding initiation so as to not break the sheets of the sheet assembly. For example, with the diameter 36 on the order of from ¼ to ½ inch (6.3 to 12.7 mm, for example about 10 mm), a rotational speed on the order of 1 -20 RPM, and a butyl rubber engagement surface 32, and a thickness 16 on the order of 500 microns, with a corner of the sheet assembly presented to the engagement surface, the engagement member 30 can produce about one pound of force (4.5 Newtons), which is a sufficient debonding initiation force to separate first and second sheets bonded in the manner of US2014-0170378, and having a bond energy of 50-800 mJ/m², for example 300-800 mJ/m², between the first and second sheet. That is, because the engagement member rotates, with its axis of rotation 34 offset in the manner described above, the engagement surface 32, due to its compliant nature, is pressed against the edge 14 and generates a friction force between it and the edge 14. As the engagement member 30 continues to rotate, with the engagement surface 32 in frictional engagement with the edge 14, it develops a first force 51 (tangential to the engagement member 30) having a component 51 a in the first direction 61 substantially normal to the first major surface 1 1 . As shown, the force 51 need not be normal to the first major surface 1 1 ; only a component 51 a of the force 51 may be substantially normal to the first major surface, as long as that component 51 a has sufficient magnitude to develop the force for separating the first sheet 10 from the second sheet 20. Indeed, a force component perpendicular to component 51 a assists in developing suitable friction between the engagement surface 32 and the edge 14. However, if the force component perpendicular to component 51 a becomes too large, it may undesirably cause the first sheet 10 to slide against the second sheet 20 and/or cause damage to the first sheet 10.

[0036] As noted above, the support 40 holds the sheet assembly 2 to the planar support surface 42 by vacuum, which develops a second force 52 having a component that acts on the sheet assembly 2 in a second direction 62, which is opposite to the first direction 61 (and as shown in FIG. 3 is substantially normal to the fourth major surface 24). Although the force 52 is shown as substantially normal to the fourth major surface 24, such need not be the case; only a component of the force 52 may be substantially normal to the first major surface, as long as that component has sufficient magnitude to develop the force for separating the first sheet 10 from the second sheet 20. Because the forces 51 and 52 have

components acting in opposite directions, and because they act on separate sheets 10, 20 of the sheet assembly, the forces 51 and 52 will initiate debonding, or separation, between at least a portion of the first and second sheets 10, 20. FIG. 4 shows a sheet assembly 2 in which a portion of the first sheet 10 has been debonded from a corresponding portion of the second sheet 20 over an area 4 that is less than the entire area over which the first sheet 10 was bonded to the second sheet 20. That is, the first and second sheets 10, 20 remain bonded over the area 6. However, after the debonding initiation at area 4, the sheets 10, 20 may be peeled from one another over the remaining area 6 by a peeling force that is less than the initiation force, and such may be performed by, for example, mechanical levers or fixtures, together with appropriate devices for engaging and pulling the sheet, for example, suction cups or other suction devices. The sheets 10, 20 may be peeled so that they are then completely separate from one another.

[0037] With the offsets 71 , 72 and diameter 36 chosen appropriately, as soon as the sheet 10 is lifted up, the force 51 (and normal component 51 a) decreases because the sheet 10 moves towards the top part of the wheel (i.e., engagement member 30). Alternatively, the controller 38 may be used to decrease, or stop, movement of the engagement surface 32 so as to reduce the force on the first sheet 10 after debonding has been initiated. For example, the controller 38 may be signaled to stop movement of the engagement surface 32 upon sensing a reduction in load on the motor 37 In either case, the force on first sheet 10 is reduced after debonding initiation, which reduces the chances of breaking or otherwise damaging the first sheet 10 after initiating the debonding from second sheet 20.

[0038] It should be emphasized that the above-described embodiments of the present invention, particularly any "preferred" embodiments, are merely possible examples of implementations, merely set forth for a clear understanding of various principles of the invention. Many variations and modifications may be made to the above-described embodiments of the invention without departing substantially from the spirit and various principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.

[0039] For example, although the engaging surface was shown as contacting the edge at a corner 8 of the sheet assembly, such need not be the case. Instead, the engagement surface may contact an edge at a distance 9 of up to about an inch (25.4 mm), for example about ¼ inch (6.3 mm) away from the corner. The distance 9 will depend upon the bonding energy between the first sheet 10 and the second sheet 20, and should be kept within a range so that the area 4 will reach from the point of contact to the corner 8 of the bonded area between the first sheet 10 and the second sheet 20. Additionally, after initiation at one location around the perimeter of the sheet assembly, the sheet assembly and engagement member may be moved relative to one another to provide initiation at one or more additional points, for example within about an inch (25.4 mm) of any remaining corner around the perimeter of the sheet assembly. If the engagement surface contacts the edge at a point too far away from the corner of the sheet assembly, either the sheets will not separate, or the sheet engaged by the engagement surface will break or otherwise be damaged. After one or more areas 4 have been provided around the perimeter of the sheet assembly 2, the sheets may be peeled from one another so that they are completely separated.

[0040] By way of additional example, although the corners 8 of the sheet assembly were shown as being right angles, i.e., the first major surface 1 1 was shown as a rectangle, such need not be the case. Instead, the corners of the sheet assembly may have chamfers on one or more of the first sheet 10 and the second sheet 20, whereby the major surfaces 1 1 , 23 may be a polygons. Additionally, when both the first and second sheets 10, 20 have chamfers, the chamfers need not have the same configuration, i.e., the major surfaces 1 1 , 23 need not have the same polygonal shape.

[0041] By way of additional example, although a circular wheel was shown, such need not be the case. Instead, for example, the engagement member may be an out-of-round wheel in the manner of a cam lobe, may be a belt driven between two wheels, may be a lever pivoting about an axis, or may be a finger. Translating rotational speed as described above (for example, a diameter 36 on the order of from 6.3 to 12.7 mm, an engagement surface 32 extending from the diameter on the order of from 1 .1 to 2.4 mm, and a rotational speed on the order of 1 -20 RPM), the linear equivalent speed of a belt would be from about 0.5 mm/s to about 18.3 mm/s. In any case, one important aspect of the engagement member is that it have an engagement surface that is disposed to act on the edge of a sheet to be removed from a sheet assembly so as not to damage that sheet. By acting on the edge of the sheet, the engagement surface is less likely to damage the major surfaces of the sheet so that the removed sheet may be used again in another assembly. That is, the engagement surface avoids damage to the major surfaces of the removed sheet, which damage may lead to reduced strength in the removed sheet, and/or to a reduced ability to bond the removed sheet with another sheet, and/or to a reduced ability to see through the removed sheet when performing alignment operations between the processes of forming a consumer electronic device on another sheet that is bonded to the removed sheet. [0042] By way of further example, although as described above, rotation of the engagement member 30 was started after positioning of the sheet assembly 2 relative thereto, such need not be the case. Instead, the engagement member 30 may be made to rotate, and while remaining in rotation, the sheet assembly 2 may be made to move in the direction 7 toward and into contact with engagement surface 32.

[0043] It is to be understood that various features disclosed in this specification and in the drawings can be used in any and all combinations. By way of non-limiting example the various features may be combined with one another as set forth in the following aspects:

[0044] According to a first aspect, there is provided a method of initiating separation of a sheet assembly, comprising:

a. moving a sheet assembly and an engagement member relative to one another, the sheet assembly comprising a first sheet and a second sheet, the first sheet comprising a first major surface, a second major surface opposite the first major surface, and an edge disposed between and adjoining the first major surface and the second major surface, the second sheet removably bonded to the second major surface, the engagement member comprising an engagement surface;

b. contacting the edge with the engagement surface;

c. with the engagement surface, applying a first force to the edge, the first force comprising a force component in a first direction that is normal to the first major surface; and

d. applying a second force to the second sheet, the second force comprising a force component in a second direction that is opposite to the first direction, whereby the application of the first and second forces causes an initial separation of at least one portion of the first sheet from a corresponding portion of the second sheet that was bonded thereto.

[0045] According to a second aspect, there is provided the method of aspect 1 , further comprising reducing the first force after the at least one portion of the first sheet has separated from the corresponding portion of the second sheet.

[0046] According to a third aspect, there is provided the method of any one of the preceding aspects, wherein the engagement surface is made of at least one of a compliant material, a butyl rubber, Nylon, or urethane. [0047] According to a fourth aspect, there is provided the method of any one of the preceding aspects, wherein the engagement surface is made of a material having a Durometer value of from 50 to 90.

[0048] According to a fifth aspect, there is provided the method of any one of the preceding aspects, wherein the engagement surface is made of a non-friable material that does not leave residue or particles on the first sheet.

[0049] According to a sixth aspect, there is provided the method of any one of the preceding aspects, wherein applying the first force comprises rotating the

engagement member.

[0050] According to a seventh aspect, there is provided the method of aspect 6, further comprising rotating the engagement member so that the engagement surface moves relative to the edge at a speed of from 0.5 to 18.3 mm/s prior to contacting the edge.

[0051] According to an eighth aspect, there is provided the method of aspect 6 or aspect 7, further comprising slowing the rotation of the engagement member after the at least one portion of the first sheet has been initially separated from the corresponding portion of the second sheet.

[0052] According to a ninth aspect, there is provided the method of any one of aspects 6-8, wherein an axis of rotation of the engagement member is offset from the first major surface in the first direction.

[0053] According to a tenth aspect, there is provided the method of any one of aspects 6-9, wherein the engagement member is a wheel.

[0054] According to an eleventh aspect, there is provided the method of aspect 10, wherein the wheel has a diameter of from 6.3 to 12.7 mm, and further comprising rotating the engagement member at a speed of from 1 to 20 revolutions per minute.

[0055] According to a twelfth aspect, there is provided the method of aspect 10 or aspect 1 1 , wherein the engagement surface is disposed continuously around the entire circumference of the wheel.

[0056] According to a thirteenth aspect, there is provided the method of aspect 10 or aspect 1 1 , further comprising a plurality of engagement surfaces disposed discontinuously around the circumference of the wheel. [0057] According to a fourteenth aspect, there is provided the method of any one of aspectsl 0-13, further comprising a plurality of engagement surfaces disposed discontinuously across the width of the wheel.

[0058] According to a fifteenth aspect, there is provided the method of any one of the preceding aspects, further comprising contacting the edge with the engagement surface within 25.4 mm of a corner of the sheet assembly.

[0059] According to a sixteenth aspect, there is provided the method of any one of the preceding aspects, wherein the first sheet is thicker than the second sheet.

[0060] According to a seventeenth aspect, there is provided the method of any one of the preceding aspects, wherein the first sheet is thinner than the second sheet.

[0061] According to an eighteenth aspect, there is provided the method of any one of the preceding aspects, wherein the first sheet has a thickness > 200 microns.

[0062] According to a nineteenth aspect, there is provided the method of any one of the preceding aspects, wherein the second sheet has a thickness < 300 microns.

[0063] According to a twentieth aspect, there is provided the method of any one of the preceding aspects, wherein the sheet assembly has a thickness < 3 mm.

[0064] According to a twenty-first aspect, there is provided the method of any one of the preceding aspects, wherein the first sheet is a silicate glass.

[0065] According to a twenty second aspect, there is provided the method of any one of the preceding aspects, wherein the second sheet is a silicate glass.

[0066] According to a twenty third aspect, there is provided the method of any one of the preceding aspects, wherein the first and second major surfaces are parallel to one another.

[0067] According to a twenty fourth aspect, there is provided the method of any one of the preceding aspects, wherein the second sheet comprises a third major surface, a fourth major surface opposite to the third major surface, and a second edge disposed between and adjoining the first major surface and the second major surface, and further wherein the second edge is coincident with the first edge.

[0068] According to a twenty fifth aspect, there is provided the method of any one of the preceding aspects, wherein the second sheet comprises a third major surface, a fourth major surface opposite to the third major surface, and a second edge disposed between and adjoining the first major surface and the second major surface, and further wherein the second edge is offset from the first edge in a direction away from the engagement surface.

[0069] According to a twenty sixth aspect, there is provided the method of aspect 26, wherein the edge offset is < 3 mm.

[0070] According to a twenty seventh aspect, there is provided the method of any one of the preceding aspects, wherein the edge is rounded.

[0071] According to a twenty eighth aspect, there is provided the method of any one of the preceding aspects, wherein the edge is chamfered.

[0072] According to a twenty ninth aspect, there is provided the method of any one of the preceding aspects, wherein the edge is square with the first and/or second major surfaces.

[0073] According to a thirtieth aspect, there is provided an apparatus for initiating separation of a sheet assembly, the apparatus comprising:

e. an engagement member comprising a compliant engagement surface; and f. a planar support surface, for holding a sheet assembly, the planar support surface being disposed relative to the engagement member so that the plane in which the planar support surface lies intersects the engagement surface in a line segment.

[0074] According to a thirty first aspect, there is provided the apparatus according to aspect 30, further comprising an axis of rotation around which the engagement surface travels.

[0075] According to a thirty second aspect, there is provided the apparatus according to aspect 30 or aspect 31 , further comprising a motor coupled to the engagement member to cause the engagement surface to travel.

[0076] According to a thirty third aspect, there is provided the apparatus according to aspect 32, further comprising a controller coupled to the motor, the controller configured to cause the motor to slow upon being signaled of a reduction in load on the motor.

[0077] According to a thirty fourth aspect, there is provided the apparatus according to any one of aspects 31 -33, wherein the axis of rotation is offset, from the plane in which the planar support surface lies, by a distance equal to or greater than the thickness of a sheet assembly in which debonding is to be initiated. [0078] According to a thirty fifth aspect, there is provided the apparatus according to aspect 34, wherein the offset is less than 6 mm.

[0079] According to a thirty sixth aspect, there is provided the apparatus according to any one of aspects 32-35, wherein the engagement member is a wheel, and the motor is coupled to the wheel to cause the wheel to rotate.

[0080] According to a thirty seventh aspect, there is provided the apparatus according to aspect 36, wherein the engagement surface is disposed continuously around the entire circumference of the wheel.

[0081] According to a thirty eighth aspect, there is provided the apparatus according to aspect 36 or aspect 37, further comprising a plurality of engagement surfaces disposed discontinuously around the circumference of the wheel.

[0082] According to a thirty ninth aspect, there is provided the apparatus according to any one of aspects 36-38, further comprising a plurality of engagement surfaces disposed discontinuously across a width of the wheel.

[0083] According to a fortieth aspect, there is provided the apparatus according to any one of aspects 36-39, wherein the diameter of the wheel is from about 6.3 to about 12.7 mm.

[0084] According to a forty first aspect, there is provided the apparatus according to any one of aspects 30-40, wherein the compliant engagement surface is made of butyl rubber, Nylon, or urethane.

[0085] According to a forty second aspect, there is provided the apparatus according to any one of aspects 30-41 , wherein the compliant engagement surface has a Durometer of from 50 to 90.

[0086] According to a forty third aspect, there is provided the apparatus according to any one of aspects 30-42, wherein the compliant engagement surface is non- friable.

Claims

What is Claimed is:

1 . A method of initiating separation of a sheet assembly, comprising:

moving a sheet assembly and an engagement member relative to one another, the sheet assembly comprising a first sheet and a second sheet, the first sheet comprising a first major surface, a second major surface opposite the first major surface, and an edge disposed between and adjoining the first major surface and the second major surface, the second sheet removably bonded to the second major surface, the engagement member comprising an engagement surface;

contacting the edge with the engagement surface;

with the engagement surface, applying a first force to the edge, the first force comprising a force component in a first direction that is normal to the first major surface; and

applying a second force to the second sheet, the second force comprising a force component in a second direction that is opposite to the first direction, whereby the application of the first and second forces causes an initial separation of at least one portion of the first sheet from a corresponding portion of the second sheet that was bonded thereto.

2. The method of claim 1 , further comprising reducing the first force after the at least one portion of the first sheet has separated from the corresponding portion of the second sheet.

3. The method of any one of the preceding claims, wherein the engagement surface is made of at least one of a compliant material, a butyl rubber, Nylon, or urethane.

4. The method of any one of the preceding claims, wherein the engagement surface is made of a material having a Durometer value of from 50 to 90.

5. The method of any one of the preceding claims, wherein applying the first force comprises rotating the engagement member.

6. The method of claim 5, further comprising slowing the rotation of the engagement member after the at least one portion of the first sheet has been initially separated from the corresponding portion of the second sheet.

7. The method of claim 5 or claim 6, wherein an axis of rotation of the engagement member is offset from the first major surface in the first direction.

8. The method of any one of claims 5-7, wherein the engagement member is a wheel, wherein the wheel has a diameter of from 6.3 to 12.7 mm, and further comprising rotating the engagement member at a speed of from 1 to 20 revolutions per minute.

9. The method of any one of the preceding claims, further comprising contacting the edge with the engagement surface within 25.4 mm of a corner of the sheet assembly.

10. The method of any one of the preceding claims, wherein the second sheet comprises a third major surface, a fourth major surface opposite to the third major surface, and a second edge disposed between and adjoining the first major surface and the second major surface, and further wherein the second edge is offset from the first edge in a direction away from the engagement surface.

1 1 . The method of claim 10, wherein the edge offset is < 3 mm.

12. An apparatus for initiating separation of a sheet assembly, the apparatus comprising:

an engagement member comprising a compliant engagement surface; and a planar support surface, for holding a sheet assembly, the planar support surface being disposed relative to the engagement member so that the plane in which the planar support surface lies intersects the engagement surface in a line segment.

13. The apparatus according to claim 12, further comprising an axis of rotation around which the engagement surface travels.

14. The apparatus according to claim 13, wherein the axis of rotation is offset, from the plane in which the planar support surface lies, by a distance equal to or greater than the thickness of a sheet assembly in which debonding is to be initiated.

15. The apparatus according to any one of claims 12-14, wherein the engagement member is a wheel, and further comprising a motor coupled to the wheel to cause the wheel to rotate.

16. The apparatus according to claim 15, wherein the diameter of the wheel is from about 6.3 to about 12.7 mm.

17. The apparatus according to any one of the preceeding claims, wherein the compliant engagement surface is made of butyl rubber, Nylon, or urethane.

18. The apparatus according to any one of the preceeding claims, wherein the compliant engagement surface has a Durometer of from 50 to 90.

19. The apparatus according to any one of the preceeding claims, wherein the compliant engagement surface is non-friable.