Method for automatically recovering from process errors during operation of wire bonding equipment

Abstract

A method of operating a wire bonding apparatus is provided, the method comprising the steps of: (a) attempting to bond a free air ball to a first bonding location using a wire bonding tool; (b) detecting that the free air ball was not properly bonded to the first bonding location in step (a); (c) bonding the free air ball to a second bonding location; (d) raising the wire bonding tool to a position above the bonded free air ball while a wire engaged with the wire bonding tool remains continuous with the bonded free air ball; (e) after step (d), weakening a neck portion of the wire above the free air ball; and (f) after step (e), separating the bonded free air ball from the wire so that a wire tail extends below the tip of the wire bonding tool.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Application No. 63 / 440,300, filed January 20, 2023, the contents of which are incorporated herein by reference.

[0002] The present invention relates to wire bonding operations, and more particularly to techniques for operating wire bonding equipment under various process error conditions. [Background technology]

[0003] In semiconductor device processing and packaging, wire bonding remains the primary method for providing electrical interconnection between two locations within a package (e.g., between a die pad on a semiconductor die and a lead on a lead frame). More specifically, a wire bonder (also called a wire bonding machine) is used to form a wire loop between the respective locations to be electrically interconnected. The primary methods for forming the wire loop are ball bonding and wedge bonding. Various types of bonding energy, such as ultrasonic energy, thermosonic energy, and thermocompression energy, can be used to form the bond between (a) the end of the wire loop and (b) the respective bonding location (e.g., die pad, lead, etc.). Wire bonding machines (e.g., stud bumping machines) are also used to form conductive bumps from portions of the wire.

[0004] In the ball bonding process, the tail of a wire extending from the tip of a bonding tool (e.g., a capillary) is melted by a spark from an electronic flame-off (EFO) device, forming a free-air ball. This free-air ball is then used to form a first bond (e.g., a ball bond) of the wire loop at a first bond location. The wire is then extended from the ball bond to a second bond location. A bonding tool is then used to bond a portion of the wire to the second bond location, forming a second bond (e.g., a stitch bond) of the wire loop. For example, the first bond location may be a bonding pad on a semiconductor die, and the second bond location may be a lead on a lead frame.

[0005] Several difficult conditions can arise in connection with such wire bonding operations. For example, during bonding of the first bond of a wire loop, a free air ball may not be properly bonded to the bond location. This condition may be referred to as an NSOP condition (not-pad-attached condition). In another example, the second bond of a wire loop may not be properly bonded to the bond location. This condition may be referred to as an NSOL condition (not-lead-attached condition). An exemplary process for addressing such "not-attached" conditions is disclosed in U.S. Patent No. 8,899,469, entitled "Automatic Rework Process for Non-Attached Conditions in Wire Bonding Operations."

[0006] Another challenge in wire bonding operations involves the so-called "short tail condition." For example, after forming a stitch bond at the second bond location of a wire loop, the bonding tool is raised to the short tail detection height and the wire is tested (e.g., an electrical continuity test) to ensure that the wire still has continuity with the stitch bond at the second bond location. If a short tail is not detected, the bonding head (i.e., carrying the bonding tool and the now-closed wire clamp) is raised and the wire is cut at the stitch bond location. The remaining wire tail length is used to form another free air ball for another wire loop. However, a short tail may be detected. A short tail condition can cause several problems during wire bonding, such as inconsistencies in the size and shape of the free air ball. An exemplary technique for addressing this "short tail" condition is disclosed in U.S. Patent No. 9,165,842, entitled "Short Tail Recovery Technique in Wire Bonding Operations."

[0007] The contents of each of US Pat. No. 8,899,469 and US Pat. No. 9,165,842 are incorporated herein by reference in their entirety.

[0008] It would therefore be desirable to provide an improved method for automatically recovering from the above-mentioned problems in the operation of wire bonding machines. Summary of the Invention [Means for solving the problem]

[0009] According to an exemplary embodiment of the present invention, there is provided a method of operating a wire bonding apparatus, the method comprising: (a) attempting to bond a free air ball to a first bonding location using a wire bonding tool; (b) detecting that the free air ball was not properly bonded to the first bonding location in step (a); (c) bonding the free air ball to a second bonding location; (d) raising the wire bonding tool to a position above the bonded free air ball (e.g., a tail height position) while a wire engaged with the wire bonding tool remains continuous with the bonded free air ball; (e) after step (d), weakening a neck portion of the wire above the free air ball; and (f) after step (e), separating the bonded free air ball from the wire such that a wire tail extends below the tip of the wire bonding tool.

[0010] According to another exemplary embodiment of the present invention, there is provided another method of operating a wire bonding apparatus, the method including: (a) forming a first bond of a wire loop at a first bond location using the wire bonding tool; (b) extending a wire continuous with the first bond to a second bond location; (c) attempting to bond a portion of the wire to the second bond location using the wire bonding tool; (d) detecting that the portion of the wire was not properly bonded to the second bond location in step (c); and (e) separating the portion of the wire from the first bond. (f) bending a portion of the wire to a bend location; and (g) connecting the portion of the wire to a third joining location.

[0011] According to yet another exemplary embodiment of the present invention, there is provided yet another method of operating a wire bonding apparatus, the method including the steps of detecting a short tail condition after forming a wire loop, forming a free air ball using the short tail, extending the wire below a tip of the wire bonding tool contiguous with the free air ball to form a first wire tail, and bonding the first wire tail to a first bond location. [Brief explanation of the drawings]

[0012] The invention is best understood from the following detailed description read in conjunction with the accompanying drawings, in which, according to common practice, various features are not drawn to scale. Rather, the dimensions of various features have been arbitrarily increased or decreased for clarity. The drawings include the following figures: [Figures 1A-1G] 1A-1G are block diagrams illustrating portions of a wire bonding apparatus useful for explaining methods of operating the wire bonding apparatus in an NSOP condition, according to various exemplary embodiments of the present invention. [Figures 2A-2F] 2A-2L are a series of block diagrams of portions of a wire bonding apparatus useful for explaining alternative methods of operating the wire bonding apparatus in an NSOP condition, according to various exemplary embodiments of the present invention. [Figure 2G-2L] 2A-2L are a series of block diagrams of portions of a wire bonding apparatus useful for explaining alternative methods of operating the wire bonding apparatus in an NSOP condition, according to various exemplary embodiments of the present invention. [Figures 3A-3F] 3A-3M are a series of block diagrams of portions of a wire bonding apparatus useful for illustrating yet another method of operating a wire bonding apparatus in an NSOP condition, according to various exemplary embodiments of the present invention. [Figure 3G-3M]3A-3M are a series of block diagrams of portions of a wire bonding apparatus useful for illustrating yet another method of operating a wire bonding apparatus in an NSOP condition, according to various exemplary embodiments of the present invention. [Figures 4A-4F] 4A-4K are a series of block diagrams of a portion of a wire bonding apparatus useful for explaining methods of operating a wire bonding apparatus under NSOL conditions, according to various exemplary embodiments of the present invention. [Figures 4G-4K] 4A-4K are a series of block diagrams of a portion of a wire bonding apparatus useful for explaining methods of operating a wire bonding apparatus under NSOL conditions, according to various exemplary embodiments of the present invention. [Figures 5A-5F] 5A-5L are a series of block diagrams of portions of a wire bonding apparatus useful for illustrating alternative methods of operating a wire bonding apparatus under NSOL conditions, according to various exemplary embodiments of the present invention. [Figure 5G-5L] 5A-5L are a series of block diagrams of portions of a wire bonding apparatus useful for illustrating alternative methods of operating a wire bonding apparatus under NSOL conditions, according to various exemplary embodiments of the present invention. [Figures 6A-6F] 6A-6K are a series of block diagrams of a portion of a wire bonding apparatus useful for explaining how to operate the wire bonding apparatus in a short wire tail condition, according to various exemplary embodiments of the present invention. [Figures 6G-6K] 6A-6K are a series of block diagrams of a portion of a wire bonding apparatus useful for explaining how to operate the wire bonding apparatus in a short wire tail condition, according to various exemplary embodiments of the present invention. [Figures 7A-7F] 7A-7L are a series of block diagrams of a portion of a wire bonding apparatus useful for explaining how the wire bonding apparatus operates in different short wire tail conditions, according to various exemplary embodiments of the present invention. [Figures 7G-7L]7A-7L are a series of block diagrams of a portion of a wire bonding apparatus useful for explaining how the wire bonding apparatus operates in different short wire tail conditions, according to various exemplary embodiments of the present invention. [Figure 8] 8-10 are flow diagrams of various methods of operating a wire bonding apparatus according to various exemplary embodiments of the present invention. [Figure 9] 8-10 are flow diagrams of various methods of operating a wire bonding apparatus according to various exemplary embodiments of the present invention. [Figure 10] 8-10 are flow diagrams of various methods of operating a wire bonding apparatus according to various exemplary embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] As used herein, the term "semiconductor device" refers to any structure that includes (or is configured to include in a later process) a semiconductor chip or die. Exemplary semiconductor devices include bare semiconductor dies, semiconductor dies on a substrate (e.g., a lead frame, PCB, carrier, etc.), packaged semiconductor devices, flip-chip semiconductor devices, dies embedded in a substrate, stacks of semiconductor dies, etc. Additionally, semiconductor devices can include devices bonded to or otherwise configured to be included in a semiconductor package (e.g., spacers, substrates, etc. bonded in a stacked die configuration). In the context of the present invention, a semiconductor device is an example of a workpiece. Another example of a workpiece includes a semiconductor device mounted on a substrate (e.g., a semiconductor die mounted on a lead frame). Yet another example of a workpiece includes multiple semiconductor devices.

[0014] Aspects of the present invention relate to, among other things, the ability of a wire bonding machine to provide recovery processes (e.g., automatic recovery processes that do not require operator intervention) for various error conditions, such as an NSOP condition, an NSOL condition, a short tail condition, and a long tail condition.

[0015] A second bonding process is used to bond any free air balls that did not properly bond to the desired bonding location (e.g., the first bond location in the design) in the first bonding process to another bonding location (e.g., the second bond location in the design, or another bonding location). For example, see the processes shown in Figures 1A-1G, 2A-2L, and 3A-3M. This second bonding process can use the same bonding parameters (e.g., bond force, ultrasonic energy, bond time, etc.) as those used in the attempted first bonding process, or different bonding parameters. Such techniques include "neck" weakening, which weakens the wire in the neck region before breaking it to achieve a desired tail length (e.g., a tail length within a predetermined specification range). Advanced automated bond-off processes can also be implemented to ensure tail length and quality.

[0016] A further exemplary embodiment of the present invention relates to an NSOL auto-healing process, which utilizes an advanced, automated bond-off process to provide the desired wire tail and efficiently continue the bonding process. See, for example, the process illustrated in Figures 4A-4K and 5A-5L.

[0017] A further exemplary embodiment of the present invention relates to an automatic short-tail recovery process that utilizes EFO (i.e., electronic flame-off) assistance, followed by an advanced automatic bond-off process. See, for example, the process illustrated in Figures 6A-6K and 7A-7L.

[0018] The advanced automated bond-off process disclosed herein includes one or more of: (i) pre-teaching of the bond-off location; (ii) pre-contact XYZ motion (i.e., angled or step motion) to bend the wire tail or other wire portion; (iii) completion of the bond-off process; and / or (iv) completion of a security wire loop / stitch to provide the desired wire tail for a subsequent wire bonding operation.

[0019] Some of the processes disclosed herein include "bond-off" processes (also called rebonding or rework processes). Such processes include (i) joining a wire portion (e.g., a free air ball, a stitch bond, a wire tail, etc.) to another bond location. When an alternative bond location is used, the alternative bond location may be another portion of the original workpiece or may be an entirely different workpiece.

[0020] Like reference numbers used throughout this specification (including the drawings) refer to like elements unless otherwise stated.

[0021] As will be understood by those skilled in the art, the term “wire portion” should be interpreted broadly and is not limited to a particular length. For example, FIGS. 4H and 5H each illustrate bending of wire portion 114e1 of wire 114 (also referred to herein as wire feed 114). In both cases, an attempt was made to bond this wire portion 114e1 to its original bonding location (see FIGS. 4C and 5C ), but the wire portion 114e1 was not properly bonded to the original bonding location. Thus, in FIGS. 4H and 5H , the wire portion 114e1 is bent prior to the bond-off process. As will be understood by those skilled in the art, the length of the “bonded” wire portion 114e1 in FIGS. 4C and 5C may not be exactly the same as the length of the “bent” wire portion 114e1 in FIGS. 4H and 5H .

[0022] As used herein, terms such as "first," "second," "third," and "fourth" are used to refer to bonding locations and wire bonds. However, these terms do not explicitly refer to a specific wire bond, a specific wire bonding location, a specific order (sequence) of wire bonding, or the like. For example, a second bonding location does not necessarily refer to the second of two bonding locations. As will be appreciated by those skilled in the art, a wire loop may include more than two bonding locations and more than two bonding portions.

[0023] Throughout this application, various bonding processes are described in connection with ultrasonic energy and / or illustrated with the reference designator "USG," but it is understood that the bond may or may not include ultrasonic energy. For example, certain wire bonds may be formed using bonding force, heat, and / or table scrub without the use of ultrasonic energy.

[0024] Referring to the drawings, FIG. 1A illustrates various elements of a wire bonding apparatus 100, including a support structure 102, a wire bonding tool 110 (e.g., a capillary), and a wire clamp 112. An exemplary workpiece 103 is supported by the support structure 102. The workpiece 103 illustrated in FIG. 1A includes a semiconductor element 106 (e.g., a semiconductor die) bonded to a substrate 104 (e.g., a lead frame). According to a wire bonding program, the wire bonding tool 110 is configured to use a wire 114 to create a wire loop that provides an electrical interconnection between (i) a bonding location on the semiconductor element 106 (e.g., a bonding pad on the semiconductor element 106) and (ii) a bonding location 104a on the substrate 104 (e.g., a lead of a lead frame).

[0025] In FIG. 1A, a free air ball 114a is formed at the end of a wire 114, and ultrasonic energy (see "USG") is applied to attempt to bond the free air ball 114a to a bonding location on a semiconductor device 106. However, as shown in FIG. 1B, the free air ball 114a is not properly bonded to the bonding location. For example, this condition may be referred to as a "not-attached-to-pad" (i.e., NSOP). Wire bonding machines often include a detection system for detecting whether a portion of the wire is properly bonded to the bonding location. For example, wire bonding machines sold by Kulicke and Soffa Industries, Inc. often utilize a "BITS" process (i.e., bond integrity test system) to determine whether a proper wire bond has (or has not) been formed. International Patent Application Publication No. WO 2009 / 002345, incorporated herein by reference in its entirety, provides exemplary details of such a process and associated systems.

[0026] In FIG. 1A, after detecting that the free air ball 114a is not properly bonded at the bond position, the wire bonding tool 110 moves toward another bond position (see FIGS. 1C-1D). In the example shown in FIG. 1D, the bond position utilized is the original second bond position 104a on the substrate 104. However, other bond positions are also contemplated. In FIG. 1D, the free air ball 114a is bonded (e.g., ultrasonically bonded, see "USG") to a bond position (e.g., lead 104a) on the substrate 104. In FIG. 1E, the wire bonding tool 110 rises, and the wire 114 (engaged with the wire bonding tool 110) remains continuous with the bonded free air ball 114a' until it reaches a position above the bonded free air ball 114a' (e.g., a tail height position). In FIG. 1F, the wire 114 is raised while engaged with the wire bonding tool 110, to a position (e.g., a tail height position) above the bonded free air ball 114a'. In FIG. 1F, the neck portion 114b of the wire 114 above the bonded free air ball 114a' is weakened. For example, the neck portion 114b can be weakened by (i) manipulating an ultrasonic transducer mounted on the wire bonding tool 110 to weaken the neck portion 114b and / or (ii) manipulating the xy table of the wire bonding apparatus 100 mounted on the wire bonding tool 110 to weaken the neck portion 114b. In FIG. 1G, the bonded free air ball 114a' is separated from the wire 114, and a wire tail 114c extends below the tip of the wire bonding tool 110. This wire tail can be used to continue the wire bonding process.

[0027] 2A-2L show another method for addressing improperly bonded free air balls (e.g., NSOP conditions). FIGS. 2A-2G show the same operation sequence as FIGS. 1A-1G. After the new wire tail 114c extends below the tip of the wire bonding tool 110, the wire bonding tool 110 is moved toward the substrate 104 (see FIG. 2H, which may be the same substrate as in FIGS. 2A-2G or a different substrate). For example, the wire bonding tool 110 can approach the bonding position on the substrate 104 at an angle to bend the wire tail, as shown in FIG. 2I. For example, this angled approach can be achieved by driving the wire bonding tool 110 in the x, y, and z directions using a drive system of a bond head assembly (not shown) carrying the wire bonding tool 110.

[0028] In FIG. 2I, the wire tail 114c is bent toward the bonding position of the substrate 104 (the wire clamp 112 is closed), and in FIG. 2J, the wire tail 114c is bonded to the bonding position of the substrate 104 (the wire clamp 112 is open). Although FIGS. 2I-2J show the wire tail 114c (FIG. 2I) bent toward the bonding position (FIG. 2J), the present invention is not limited thereto. For example, the wire tail 114c may be bent toward a bending position (e.g., a cup-shaped bending position, not shown) different from the bonding position (FIG. 2J).

[0029] In Figure 2K, the wire bonding tool 110 is raised, and the wire 114 (engaged with the wire bonding tool 110) is raised to a position above (e.g., at tail height) the bonded wire tail 114c' while remaining continuous with the bonded wire tail 114c'. In Figure 2L, the bonded wire tail 114c' is separated from the wire 114, and another wire tail 114c extends below the tip of the wire bonding tool 110. This wire tail 114c can be used to continue the wire bonding process.

[0030] 3A-3M illustrate another method for addressing an improperly bonded free air ball (e.g., an NSOP condition). FIGS. 3A-3J illustrate the same sequence of operations as FIGS. 2A-2J. After the wire tail 114c is bonded to the bond location in FIG. 3J (e.g., to form a first bond in the wire loop), the wire 114d, which is continuous with the bonded wire tail 114c', is extended to another bond location (see FIG. 3K), where a portion of the wire is bonded to form a second bond in the wire loop (see FIG. 3K). The wire bonding tool 110 is then raised (e.g., to a tail height position) above the second bond (labeled 114d1 in FIG. 3L) while the wire feed 114 remains continuous with the second bond (see FIG. 3L). In FIG. 3L, the wire feed 114 remains continuous with the second bond. At 3M, the wire feed 114 is separated from the second bond 114d1, forming another wire tail 114c (wire loop labeled 114d') below the wire bonding tool 110. This wire tail 114c can be used to continue the wire bonding process.

[0031] 1A-1G, 2A-2L, and 3A-3M each relate to a method of operation of a wire bonding apparatus when a free air ball is not properly bonded to a bonding location (e.g., an NSOP (not on pad) condition). However, aspects of the present invention relate to a method of operation of a wire bonding apparatus when other types of problems occur (e.g., an NSOL (not on lead) condition, a short tail condition, etc.).

[0032] 4A-4K, methods for addressing improperly bonded wire portions (e.g., NSOL conditions) are illustrated. In FIG. 4A, a free air ball 114a is formed at the end of a wire 114, and ultrasonic energy (USG) is applied using a bonding tool 110 to bond the free air ball 114a to a bonding location on a semiconductor element 106 (e.g., a bonding pad on the semiconductor element 106 of the workpiece 103). (This bonding location may be considered a first bonding location.) In FIG. 4B (where the free air ball is shown as a bonded free air ball 114a'), a wire 114e continuous with the first bonding location (i.e., the bonded free air ball 114a') is extended to a second bonding location (e.g., a lead 104a of a lead frame 104). In FIG. 4C, the free air ball 114a' is extended to a second bonding location (e.g., a lead 104a of a lead frame 104). In FIG. 4C , ultrasonic energy (see “USG”) is applied in an attempt to bond wire portion 114e1 of wire length 114e (e.g., end 114e1 of wire length 114e) to a second bond location. However, as shown in FIG. 4D , wire portion 114e1 is not properly bonded to the second bond location. For example, this condition may be referred to as a “not attached lead” (NSOL). As noted above, wire bonding machines often include detection systems for detecting whether a portion of the wire is properly bonded to a bond location. For example, wire bonding machines sold by Kulicke and Soffa Industries, Inc. often utilize a “BITS” process (i.e., bond integrity test system) to confirm that a proper wire bond has been formed. International Patent Application Publication No. WO 2009 / 002345 (incorporated by reference in its entirety) provides exemplary details of such a process and associated systems.

[0033] In FIG. 4E, with the wire clamp 112 closed, it is detected that the wire portion 114e1 is not properly bonded to the second bonding location, and in FIG. 4F, the wire 114e (including the wire portion 114e1) is separated from the first bond (bonded free air ball 114a'). In FIG. 4G, the wire bonding tool 110 is moved toward the bonding location on the substrate 104. For example, the wire bonding tool 110 can approach the bonding location on the substrate 104 at an angle so as to bend the wire portion 114e1 in FIG. 4H. For example, this angled approach is performed by driving the wire bonding tool 110 in the x, y, and z directions using a drive system of a bond head assembly (not shown) on which the wire bonding tool 110 is mounted.

[0034] In FIG. 4H, wire portion 114e1 (a portion of the length of wire 114e) is bent toward a bonding position on substrate 104 (wire clamp 112 is closed). In FIG. 4I, wire portion 114e1 is bonded to a bonding position on substrate 104 (wire clamp 112 is open). While FIGS. 4H-4I illustrate bending wire portion 114e1 (FIG. 4H) toward the bonding position (FIG. 4I), the present invention is not limited thereto. For example, wire portion 114e1 may be bent toward a bending position (e.g., a cup or other bending position, not shown) different from the bonding position (FIG. 4I). Prior to FIG. 4I, wire portion 114e1 is bent toward a bonding position on substrate 104. In FIG. 4J, wire bonding tool 110 (with the wire clamp open) is elevated above bonded wire portion 114e1′ (e.g., to the tail level). Next, in Figure 4J, wire clamp 112 is closed, leaving wire 114 (engaged to wire bonding tool 110) continuous with the bonded wire portion (now designated 114e1'). In Figure 4K, bonded wire portion 114e1' is separated from wire 114, leaving another wire tail 114c extending below the tip of wire bonding tool 110. This wire tail 114c can be used to continue the wire bonding process.

[0035] 5A-5L illustrate another method for addressing an improperly bonded wire portion (e.g., an NSOL condition). FIGS. 5A-5I illustrate the same sequence of operations as FIGS. 4A-4I. After wire portion 114e1 is bonded to the bond position (e.g., the third bond position) of FIG. 5I (e.g., to form a first bond of the wire loop labeled 114e1′ in FIG. 5J), wire 114d, continuous with the bonded wire portion 114e1′, is extended to another bond position (e.g., the fourth bond position) (see FIG. 5J), where a portion of the wire is bonded to form a second bond of the wire loop (see FIG. 5J). The wire bonding tool 110 is then raised (e.g., to a tail height position) above the second bond (see FIG. 5K) with the wire feed 114 still continuous with the second bond (labeled 114d1 in FIG. 5L). 5L, the wire feed 114 is separated from the second bond 114d1, forming another wire tail 114c (wire loop labeled 114d') below the wire bonding tool 110. This wire tail 114c can be used to continue the wire bonding process.

[0036] 6A-6K, a method for addressing a short tail condition in the wire bonding apparatus 100 is shown. In FIG. 6A, after the formation of the wire loop 208 (including the length of wire between the first bond 208a and the second bond 208b), the wire bonding tool 110 is raised to a height h1 (referred to as the "tail height") that is higher than height h0. In normal operation, the detection system can detect the presence of a (continuous) wire tail still connected to the second bond 208b. However, in the example shown in FIG. 6A, a short tail condition has occurred. That is, the wire tail 214a extending from the tip of the wire bonding tool 110 in FIG. 6A is short and not connected to the second bond 208b.

[0037] As mentioned above, wire bonding machines sold by Kulicke and Soffa Industries, Inc. often utilize a "BITS" process (i.e., Bond Integrity Test System) to verify that a proper wire bond has been formed. International Patent Application Publication No. WO 2009 / 002345, which is incorporated herein by reference in its entirety, provides a detailed example of such a process and associated system. While such a BITS process can be used to detect a short tail condition, it will be understood that other techniques can also be used to detect a short tail condition.

[0038] 6B-6C, a short wire tail 214a is used to form a free air ball 214b. For example, an electronic flame-off device 217 is used to melt the short wire tail 214a, forming the free air ball 214b (e.g., height h2, which may be different from and / or greater than h1). As will be appreciated by those skilled in the art, the free air ball 214b will likely be smaller than a typical free air ball in a particular wire bonding application.

[0039] 6D-6F illustrate an exemplary process for forming the first wire tail 214c. More specifically, in FIG. 6D (with the wire clamp 112 closed), the wire bonding tool 110 is lowered (e.g., by lowering a bond head assembly (not shown) carrying the wire bonding tool 110) toward the substrate 104 (which may be part of the substrate 104 in FIG. 6A or another substrate). In FIG. 6E (with the wire clamp 112 open), the wire bonding tool 110 is further lowered toward the substrate 104. In FIG. 6F (with the wire clamp 112 closed), contact between the free air ball 214b and the substrate 104 is detected. Thus, through this process (or another process), the wire continuous with the free air ball is extended below the tip of the wire bonding tool, forming the first wire tail 214c (e.g., height h3). U.S. Patent No. 9,165,842 describes a method for creating such a wire tail after detecting a short wire tail. Such exemplary methods may also be used within the scope of the present invention to extend the wire below the tip of the wire bonding tool to create a first wire tail.

[0040] 6G, the wire bonding tool 110 is moved toward the bonding position on the substrate 104. For example, the wire bonding tool 110 approaches the bonding position on the substrate 104 at an angle so as to bend the wire tail 214c as shown in FIG. 6H. For example, this oblique approach is performed by driving the wire bonding tool 110 in the xyz directions using a drive system of a bond head assembly (not shown) on which the wire bonding tool 110 is mounted.

[0041] In FIG. 6H, the wire tail 214c is bent toward a bonding position on the substrate 104 (the wire clamp 112 is closed). In FIG. 6I, the wire tail 214c is bonded to a bonding position on the substrate 104 (the wire clamp 112 is open). Although FIGS. 6H-6I show the wire tail 214c being bent toward a bonding position (FIG. 6I), the present invention is not limited thereto. For example, the wire tail 214c may be bent toward a bending position (e.g., a cup-shaped or other bending position, not shown) different from the bonding position (FIG. 6I). Prior to FIG. 6J, the wire bonding tool 110 (with the wire clamp open) is raised to a position above the bonded wire tail 214c' (e.g., a tail height position). Next, in FIG. 6J, the wire tail 214c is bonded to a bonding position on the substrate 104. In Figure 6J, the wire clamp 112 is closed and the wire 114 (engaged with the wire bonding tool 110) is continuous with the spliced ​​wire tail 214c'. In Figure 6K, the spliced ​​wire tail 214c' is separated from the wire 114, leaving another wire tail 114c extending below the tip of the wire bonding tool 110. This wire tail 114c can be used to continue the wire bonding process.

[0042] 7A-7L illustrate another method for addressing a short tail condition in a wire bonding apparatus. FIGS. 7A-7I illustrate the same sequence of operations as FIGS. 6A-6I. After the wire tail 214c is bonded to the substrate 104 at a bonding location (FIG. 7I), the wire 214d, continuous with the bonded wire tail 214c', is extended to another bonding location (e.g., a second bonding location) (see FIG. 7J), for example, to form a first bond of the wire loop, designated 214c', and a portion of the wire is bonded to this bonding location to form a second bond 214e of the wire loop (see FIG. 7J). The wire bonding tool 110 is then raised above the second bond 214e (e.g., to a tail height position) (see FIG. 7K), with the wire feed 114 remaining continuous with the second bond. In FIG. 7K, the wire feed 114 remains continuous with the second bond. 7L, the wire feed 114 is separated from the second bond 214e, forming another wire tail 114c (wire loop labeled 214') below the wire bonding tool 110. This wire tail 114c can be used to continue the wire bonding process.

[0043] 8-10 are flow diagrams illustrating various methods of operation of the wire bonding apparatus. As will be understood by those skilled in the art, certain steps included in the flow diagrams may be omitted, certain steps may be added, and the order of steps may be changed from the order shown, all within the scope of the present invention.

[0044] Referring to FIG. 8 , in step 800, an attempt is made to bond a free air ball to a first bonding location using a wire bonding tool (see, e.g., FIGS. 1A, 2A, and 3A). In step 802, it is detected that the free air ball was not properly bonded to the first bonding location in step 800 (see, e.g., the unbonded free air ball in FIGS. 1B, 2B, and 3B). In step 804, the free air ball is bonded to a second bonding location (see, e.g., FIGS. 1D, 2D, and 3D). In step 806, the wire bonding tool is raised to a position above the bonded free air ball with the wire engaged with the wire bonding tool in continuity with the bonded free air ball (see, e.g., FIGS. 1E, 2E, and 3E). In step 808, after step 806, the neck portion of the wire is weakened above the free air ball. In step 810, after step 808, the bonded free air ball is separated from the wire, with the wire tail extending below the tip of the wire bonding tool (see, eg, Figures 1G, 2G, 3G).

[0045] In certain embodiments, in optional step 812, the wire tail is bent to a third bond location (see, e.g., FIGS. 2I and 3I), and the wire tail is bonded to the third bond location (see, e.g., FIGS. 2J and 3J). In certain embodiments, in optional step 814, the wire tail is bent to a bent location, and the wire tail is bonded to the third bond location. In certain embodiments, in optional step 816, the wire tail is bonded to the third bond location (see, e.g., FIG. 2J). The wire bonding tool is raised above the bonded wire tail (see, e.g., FIG. 2K), with the wire feed still continuous with the bonded wire tail. The wire feed is then separated from the bonded wire tail, and another wire tail is formed below the wire bonding tool (see, e.g., FIG. 2L). In certain embodiments, in optional step 818, the wire tail is bonded to a third bond location to form a first bond of the wire loop (e.g., see FIG. 3J), the wire is extended to a fourth bond location (e.g., see FIG. 3K), a portion of the wire is bonded to the fourth bond location to form a second bond of the wire loop (e.g., see FIG. 3K), the wire bonding tool is raised above the second bond while the wire feed remains continuous with the second bond (e.g., see FIG. 3L), and the wire feed is separated from the second bond to form another wire tail below the wire bonding tool (e.g., see FIG. 3M).

[0046] Referring to FIG. 9 , in step 900, a first bond of a wire loop is formed at a first bond location using a wire bonding tool (see, e.g., FIGS. 4A and 5A ). In step 902, a wire continuous from the first bond is extended to a second bond location (see, e.g., FIGS. 4B and 5B ). In step 904, an attempt is made to bond a portion of the wire to the second bond location using the wire bonding tool (see, e.g., FIGS. 4C and 5C ). In step 906, it is detected that a portion of the wire was not properly bonded to the second bond location in step 904 (see, e.g., the unbonded wire in FIGS. 4D and 5D ). In step 908, a portion of the wire is separated from the first bond (see, e.g., FIGS. 4F and 5F ). ​​In step 910, a portion of the wire is bent along a bend location (see, e.g., FIGS. 4H and 5H ). In step 912, a portion of the wire is bonded to a third bond location (see, eg, Figures 4I and 5I).

[0047] In certain embodiments, in optional step 914, after step 912, the wire bonding tool is raised above the third bond position with the wire feed still connected to the bonded portion of the wire, and the wire feed is separated from the bonded portion of the wire to form another wire tail below the wire bonding tool (see, e.g., FIGS. 4J and 4K). In certain embodiments, in optional step 916, after step 912, another wire is extended to a fourth bond position with the wire feed still connected to the bonded portion of the wire (see, e.g., FIG. 5J), and another portion of the wire is bonded to the fourth bond position to form a second bond of the wire loop (see, e.g., FIG. 5J). The wire bonding tool is raised above the second bond with the wire feed still connected to the second bond (see, e.g., FIG. 5K), and the wire feed is separated from the second bond to form another wire tail below the wire bonding tool (see, e.g., FIG. 5L).

[0048] Referring to FIG. 10, in step 1000, a short tail condition is detected after the formation of a wire loop, and a short wire tail extends from the tip of the wire bonding tool (see, for example, FIGS. 6A and 7A). In step 1002, a free air ball is formed using the short wire tail (see, for example, FIGS. 6B-6C and 7B-7C). In step 1004, the wire continuous with the free air ball is extended below the tip of the wire bonding tool to form a first wire tail (see, for example, FIGS. 6D-6F and 7D-7F). In step 1006, the first wire tail is bonded to a first bonding location (see, for example, FIGS. 6I and 7I).

[0049] In certain embodiments, in optional step 1008, before step 1006, the first wire tail is bent to a first bond position (see, e.g., FIGS. 6H and 7H). In certain embodiments, in optional step 1010, before step 1006, the first wire tail is bent to a bent position. In certain embodiments, in optional step 1012, the wire bonding tool is raised to a position above the bonded first wire tail with the wire engaged with the wire bonding tool continuously with the bonded first wire tail (see, e.g., FIG. 6J), and the bonded first wire tail is separated from the wire so that the second wire tail extends below the tip of the wire bonding tool (see, e.g., FIG. 6K). In certain embodiments, in optional step 1014, a length of wire is extended to a second bond position. A portion of the wire is bonded to the second bond position to form a second bond of another wire loop (see, e.g., FIG. 7J). The wire bonding tool is raised above the second bond with the wire feed still continuous with the second bond (see, e.g., FIG. 7K), and the wire feed is separated from the second bond to form a second wire tail below the wire bonding tool (see, e.g., FIG. 7L).

[0050] Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not limited to the details shown, and various changes in details may be made within the scope and range of equivalents of the claims and without departing from the invention.

Claims

1. 1. A method of operating a wire bonding apparatus, comprising: (a) attempting to bond a free air ball to a first bonding location using a wire bonding tool; (b) detecting that the free air ball was not properly bonded to the first bonding position in the step (a); (c) joining the free air ball to a second joining position; (d) raising the wire bonding tool to a position above the bonded free air ball while the wire engaged with the wire bonding tool is continuous with the bonded free air ball; (e) after step (d), weakening the neck portion of the wire above the free air ball; (f) after step (e), separating the bonded free air ball from the wire so that a wire tail extends below the tip of the wire bonding tool; A method having the following.

2. The method of claim 1 , further comprising the steps of: (g1) bending the wire tail to a third bonding location; and (g2) bonding the wire tail to the third bonding location.

3. 3. The method of claim 2, further comprising, prior to step (g1), the step of angularly approaching the third joining location to allow for bending in step (g1).

4. 4. The method of claim 3, further comprising, before step (g1), performing xyz movement using a drive system of a bond head assembly carrying the wire bonding tool to approach the third bonding position at an angle.

5. 3. The method of claim 2, wherein a wire clamp above the wire bonding tool is closed during step (g1) and opened during step (g2).

6. 2. The method of claim 1, further comprising the steps of: (g1) bending the wire tail to a bent position; and (g2) joining the wire tail to a third joining position.

7. 7. The method of claim 6, wherein a wire clamp above the wire bonding tool is closed during step (g1) and opened during step (g2).

8. 10. The method of claim 1, further comprising the steps of: bonding the wire tail to a third bonding location; raising the wire bonding tool above the bonded wire tail while a wire feed remains continuous with the bonded wire tail; and separating the wire feed from the bonded wire tail to form another wire tail below the wire bonding tool.

9. 10. The method of claim 1, further comprising the steps of: bonding the wire tail to a third bond location to form a first bond of the wire loop; extending the wire to a fourth bond location; bonding a portion of the wire to the fourth bond location to form a second bond of the wire loop; raising the wire bonding tool above the second bond with a wire feed continuous with the second bond; and separating the wire feed from the second bond to form another wire tail below the wire bonding tool.

10. 2. The method of claim 1, wherein step (e) comprises weakening the neck portion of the wire by at least one of the following steps: (i) manipulating an ultrasonic transducer mounted on the wire bonding tool to weaken the neck portion; and (ii) manipulating an xy table of the wire bonding apparatus mounted on the wire bonding tool to weaken the neck portion.

11. 1. A method of operating a wire bonding apparatus, comprising: (a) forming a first bond on a wire loop at a first bond location using the wire bonding tool; (b) extending a wire continuous with the first bond to a second bond location; (c) using the wire bonding tool to attempt to bond a portion of the wire to the second bond location; (d) detecting that a portion of the wire was not properly joined to the second joining position in step (c); (e) separating a portion of the wire from the first bond; (f) bending a portion of the wire to a bend location; (g) connecting a portion of the wire to a third bond location; A method comprising:

12. The method of claim 11 , wherein the bending location is the third joint location.

13. The method of claim 11 , wherein the bend location is different from the third bond location.

14. 12. The method of claim 11, wherein prior to step (f), the method comprises the step of approaching the third bond location at an angle to allow for bending at (f).

15. 15. The method of claim 14, further comprising, prior to step (f), performing xyz movement using a drive system of a bond head assembly carrying the wire bonding tool to approach the third bonding position at the angle.

16. 12. The method of claim 11, wherein a wire clamp above the wire bonding tool is closed during step (f) and opened during step (g).

17. 12. The method of claim 11, further comprising: (h) after step (g), raising the wire bonding tool above the third bond position while the wire supply is still continuous with the bonded portion of the wire; and (h) separating the wire supply from the bonded portion of the wire to form another wire tail below the wire bonding tool.

18. 12. The method of claim 11, further comprising: (h) extending another length of wire to a fourth bond location, wherein after step (g), the wire feed is continuous with the bonded portion of the wire to extend the other length of wire to the fourth bond location; (i) bonding another portion of the wire to the fourth bond location to form a second bond of the wire loop; (j) raising the wire bonding tool above the second bond with the wire feed continuous with the second bond; and (k) separating the wire feed from the second bond to form another wire tail below the wire bonding tool.

19. 1. A method of operating a wire bonding apparatus, comprising: (a) detecting a short tail condition in which a short wire tail extends from the tip of a wire bonding tool after forming a wire loop; (b) forming a free air ball using the short wire tail; (c) extending a wire continuous with the free air ball below the tip of the wire bonding tool to form a first wire tail; (d) joining the first wire tail to a first joining location; A method comprising:

20. 20. The method of claim 19, further comprising, prior to step (d), bending the first wire tail toward the first bond location.

21. 21. The method of claim 20, wherein prior to the bending step, the method includes the step of approaching the first bond location at an angle that allows for the bending.

22. 21. The method of claim 20, further comprising, prior to the bending step, performing xyz movement using a drive system of a bond head assembly carrying the wire bonding tool to angularly approach the first bonding location.

23. 21. The method of claim 20, wherein a wire clamp above a wire bonding tool is closed during the bending step and is open during step (d).

24. 20. The method of claim 19, further comprising the step of bending the first wire tail to a bent position before step (d).

25. 25. The method of claim 24, wherein a wire clamp above the wire bonding tool is closed during the bending step and is opened during step (d).

26. 20. The method of claim 19, further comprising: (e) raising the wire bonding tool to a position above the bonded first wire tail while the wire engaged with the wire bonding tool is continuous with the bonded first wire tail; and (f) after step (e), separating the bonded first wire tail from the wire so that a second wire tail extends below the tip of the wire bonding tool.

27. 20. The method of claim 19, further comprising the steps of extending the wire to a second bond location; bonding a portion of the wire to the second bond location to form a second bond on another wire loop; raising the wire bonding tool above the second bond with the wire feed continuous with the second bond; and separating the wire feed from the second bond to form a second wire tail below the wire bonding tool.

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