Abstract:
An automatic ultrasonic wire bonding machine for bonding interconnecting wires to electrically conductive sites on a workpiece includes a gantry which supports a generally downwardly cascaded series of support platforms linearly translatable with respect to the gantry and to one another in response to translation drive signals provided from a remote source to a separate translation motor for each platform. A head support assembly mounted to the last translatable platform in the series rotatably supports via a hollow elongated spindle an orbital bonding tool head rotatable with respect to the head support assembly in response to a rotational drive signals provided to a head rotation motor from a remote source. The orbital bonding tool head in turn supports via a novel parallelogram linkage an ultrasonic transducer having fitted therein a downwardly protruding ultrasonic bonding tool, the parallelogram linkage enabling the tool tip to be displaced only vertically in response to reaction forces exerted on the tip in translating the tip downwardly into contact with a workpiece. Attached to a transducer support block comprising one element of the parallelogram linkage is a wire clamp located rearward of the bonding tool which has a pair of laterally opposed, laterally reciprocally actuable blades which move apart to receive and allow free movement therebetween wire from a wire supply reel, and together to grip the wire, and a clamp actuator for reciprocally moving the clamp blades in unison towards and away from the bonding tool to thereby feed wire through a wire feed bore disposed diagonally through the tool. The clamp actuator includes a hollow drive shaft which is disposed vertically and axially through a bore provided through the head drive spindle, the drive shaft having pinned to its upper end a belt-driven pulley and pinned to its lower end an eccentrically mounted cam wheel on which rides a cam follower protruding from a bell crank pivotably coupled to a parallelogram linkage bar and rigidly coupled to a clamp blade support. Wire from a supply reel located above the head courses through a bore disposed axially through the clamp actuator drive shaft, exiting through a central coaxial bore through the cam wheel, and through a vertically disposed bore through the transducer into a diagonally disposed channel formed between the jaw blades. Preferably, the machine includes a drag tube for frictionally resisting motion wire supplied from the wire supply interposed between the exit opening in the bottom of the cam wheel, and the clamp blades, the drag tube having a vertically disposed straight lower portion which fits in a bore vertically disposed through the transducer, an arcuately curved intermediate portion connected to an upper end of the vertical portion, and a straight upper portion connected to an upper end of the intermediate portion, which is angled upwardly and forwardly towards the cam wheel at an elevation angle of about sixty degrees.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    A. Field of the Invention  
           [0002]    The present invention relates to machines and apparatus for making ultrasonic wire bonds on miniature workpieces such as microcircuits and read/write heads of the type used to read data from and write data to disk memories. More particularly, the invention relates to an automatic ultrasonic bonding machine that includes an orbital head rotatable by a motor drive, thus enabling an ultrasonic wedge-type wire bonding tool protruding from the head to be oriented in arbitrary azimuthal directions, thereby enabling wire to be paid out without twisting through a wire feed bore disposed diagonally through the bonding tool, from a first bond site to subsequent bond sites located at arbitrary compass directions from the first bond site, without requiring that the workpiece be rotated.  
           [0003]    B. Description of Background Art  
           [0004]    Miniature electronic circuits, or “micro-circuits,” are used in vast quantities, in a wide variety of consumer, commercial, industrial and military devices and equipment. The majority of such micro-circuits are of a type referred to as integrated circuits. Integrated circuits contain a number of active circuit elements such as transistors, and passive elements such as resistors and capacitors. In semiconductor integrated circuits, conductive paths between circuit elements on a semiconductor substrate are formed by selectively etching the substrate. In hybrid micro-circuits, circuit elements mounted on a ceramic substrate are usually interconnected by conductive ink paths on the substrate.  
           [0005]    The functional portions of integrated circuits are typically in the form of very small, rectangular-shaped chips, ranging in size from 0.025 inch to 0.200 inch or more on a side. Input connections to integrated circuit chips are often made by bonding a very fine wire to conductive pads on the chips, the other end of each wire being bonded to a conductive terminal that is sufficiently large and robust to be inserted into a printed circuit board and soldered to conductors on the board. Wire bonding of this type utilizes ultrasonic energy and/or heat to form an intermetallic bond or weld between the wire and metallic bond site. Such wire bonds are also used to form interconnections between pads of integrated circuits, and to connect lead-out terminals to delicate read/write heads used in disk memories.  
           [0006]    Typically, bonding wires used to interconnect the pads of a semiconductor chip to terminals of a package containing the chip are made of aluminum or gold, and have a diameter of about 1 mil (0.001 inch). Those wires must be bonded to small, typically rectangular-shaped, integrated circuit pads a few mils wide.  
           [0007]    The most common method of interconnecting wires between semiconductor chip pads and external terminals is to form an ultrasonic weld at each end of a conducting wire. To form such bonds, the free end of a length of bonding wire is placed in contact with a pad. Then the tip of an ultrasonic transducer is pressed against the wire, and energized with ultrasonic energy for a short time interval, welding an end of the wire to the pad. The free end of the bonded wire is then moved to other pads, and bonded thereto by the same process. After the last bond in a series of bonds has been thus formed, the wire is severed near the last bond.  
           [0008]    In view of the very small size of the micro-circuit pads and bonding wire, it can be appreciated that ultrasonic bonding of connecting wires to integrated circuit pads must be performed using a tool mounted in a bonding machine that permits the tool to be manipulated to precisely controllable positions within a work area containing a workpiece.  
           [0009]    Typical wire bonding machines used for ultrasonic welding of wires to micro-circuit pads includes an elongated, generally vertically disposed, force-applying member or “tool.” The tool is connected at the upper end thereof to a source of ultrasonic energy, such as a piezoelectric transducer connected to an electrical energy source alternating at an ultrasonic frequency. Usually, the tool is connected to the transducer through a tapered horn structure that matches the acoustic input impedance of the tool to the output impedance of the transducer, which typically has a larger diameter than the tool.  
           [0010]    One type of ultrasonic bonding tool used to bond wires to micro-circuit pads is referred to as a wedge bonder and has a flat lower working face adapted to press a bonding wire into contact with a pad, while ultrasonic energy is applied through the tool to the wire to form an ultrasonic weld. This working face is usually quite small, typically having a rectangular shape only about a few mils on a side, to permit bonding wire to small micro-circuit pads, without contacting adjacent circuit elements. Typically, this is done by first viewing a particular workpiece pad and tool tip in a stereo microscope and video camera to align a workpiece relative to a bonding machine, and then using an automatic actuator system to position the tool tip at consecutive bond site locations on the workpiece, using a control system which employs pattern recognition logic.  
           [0011]    In most wire bonding machines, the bonding tool is so constructed as to facilitate the positioning of bonding wire over a pad, prior to performing the bonding operation. Such bonding tools may include an upwardly angled lower face rearward of the working face, and a generally vertically disposed rear face. An angled bore or wire guide hole having an entrance aperture in the rear face and an exit aperture in the angled lower face of the tool enables bonding wire supplied from a reel mounted upwardly and rearwardly of the tool to be paid out through the exit aperture in the angled lower face of the tool. Typically, a remotely actuable clamp located rearward of the wire guide hole entrance and movable with the tool is used to feed bonding wire through the guide hole.  
           [0012]    The clamp used to push wire through the guide hole of a bonding tool usually consists of a pair of jaws that may alternately be closed to grip the wire, and opened to allow free travel of the wire. Generally, such clamps may be moved toward and away from the guide hole entrance, typically on a line of movement which coincides with the axis of the guide hole. To feed wire through the guide hole, the jaws of the clamp are first opened, and the clamp then moved away from the guide opened, and the clamp then moved away from the guide hole. The jaws are then closed to grip the wire, and then moved towards the guide hole, thus feeding wire through the guide hole.  
           [0013]    In wire bonding machines of the type just described, the machine is used to translate the bonding tool to the proper position to bond wire to a first bond site of a pair of bond sites, such as a pad on an integrated circuit die, feed wire out through the guide hole exit aperture, move the tool to a second bond site and form another bond. In this manner, any desired number of pads or other elements of a circuit can be connected together, in a procedure referred to a “stitch” bonding. After the last bond in a series of bonds has been made, the wire must be severed, to permit making bonds between other pairs of bond sites. Oftentimes, the bonding tool itself is utilized to sever the bonding wire.  
           [0014]    In moving a wedge bonding tool from a first bond site to a second bond site, the tool must be translated rearward from, the first site to the second site, in a vertical plane containing both the longitudinal axis and wire-guide bore axis of the tool. This requirement results from the fact that wire paying out forwardly through the exit aperture of the bonding tool tip must remain in the plane containing the longitudinal and guide hole axes of the tool, to ensure that the wire will not bind on the exit aperture chamfer, or become twisted.  
           [0015]    Because of the requirement for translating a wedge bonding tool from a first to subsequent bond sites in the plane of the bonding tool longitudinal axis and wire guide bore axis, existing wedge bonding methods require that a workpiece be rotated to align a direction vector between the two sites with the bonding tool plane, and subsequent translation of the bonding tool rearwardly in that plane along the direction vector.  
           [0016]    One method of performing the required relative translations and rotations of a wedge bonding tool relative to a workpiece utilizes a support platform for the workpiece, which is translatable in an X-Y plane perpendicular to the longitudinal axis of the bonding tool, and rotatable in the Y-Y plane. With this method, the bonding tool need only be translatable downwardly, in a minus −Z direction to effect a bond, and upwardly in a plus+Z direction after a bond has been made.  
           [0017]    In some ultrasonic wire bonding applications, the bonding tool tip may move in arbitrary compass directions between first and succeeding bond sites. Thus, ball bonding tools, which feed bonding wire through a single capillary bore coaxial with the longitudinal axis of the tool may be translated in any direction between bond sites, without regard to the orientation of the tool, because of the azimuthal symmetry of the tool. For such applications, it is possible to translate the bonding tool in X and Y directions, as well as the Z direction, to make bonds between sites on a fixed workpiece. Thus, the present inventor disclosed in copending application, Ser. No. 09/570,196, filed May 12, 2000, an Automatic Ultrasonic Bonding Machine With Vertically Tiered Orthogonally Translatable Tool Support Platforms, which include a positioning mechanism for automatically translating the tip of an ultrasonic bonding tool by drive motors to precisely pre-determinable positions within a three-dimensional coordinate space containing a workpiece. The machine described in that application provides means for translating a bonding tool, in X-Y directions parallel to a plane containing a workpiece to position the tool tip over a particular bond site, translating the tool downwardly in a minus −Z direction to make an ultrasonic wire bond, translating the tool upwardly to withdraw its tip from the first bond site, and translating the tool in X-Y direction to position the tool over a subsequent intended bond site, and form thereat a subsequent bond. Thus, the disclosed machine eliminates the a requirement for a rotatable X-Y table for supporting a workpiece, and provides a highly effective method for making bonds on workpieces located on a conveyor, for example. The present invention was conceived of to further advance the wire bonding machine art, by providing a machine capable of making a sequence of wedge bonds without requiring either rotation or translation of a workpiece.  
         OBJECTS OF THE INVENTION  
         [0018]    An object of the present invention is to provide a machine for positioning an ultrasonic wire bonding tool at precisely determinable first bond site locations relative to a workpiece, orbiting the bonding tool about its longitudinal axis to an arbitrary compass direction, and translating the tool in the compass direction to precisely determinable second bond site locations while maintaining the tool irrotational in the plane of translation to the second bond site location, thus allowing a bonding wire to pay out through an aperture through the bonding tool from said first location to said second location without twisting from the translating plane.  
           [0019]    Another object of the invention is to provide an ultrasonic wire bonding machine having an orbital head which rotatably supports a wedge bonding tool having a wire feed bore which angles upwardly and rearwardly from the tip of the tool, whereby the head may be rotated to rotate a vertical plane containing the longitudinal axes of the tool and the wire feed bore to an arbitrary compass direction, thereby enabling the head to be translated rearwardly in that plane to pay out wire in the translation plane from a bond made at a first site on a workpiece by the tool to a second bond site, without requiring that the workpiece be rotated.  
           [0020]    Another object of the invention is to provide an automatic ultrasonic wire bonding machine which includes means for translating a bonding tool to an arbitrary location within a defined workspace, and means for rotating the tool to thereby enable wire fixed at one end to a first bond site on a workpiece and at the other end to a supply reel to a pay out through a wire feed bore disposed through the tool at an angle to the longitudinal axis of the tool, the wire remaining in a vertical plane containing the longitudinal and wire bore axes of the tool, thereby enabling the machine to translate the tool in that plane to position the wire above a second bond site on a workpiece, without twisting the wire.  
           [0021]    Another object of the invention is to provide an ultrasonic wire bonding machine which includes a cascaded stack of orthogonally translatable support platforms that support an orbital bonding head, the latter supporting a bonding tool, the machine including means for effecting translation motions of the support platforms, and rotation of the orbital bonding head, thereby enabling the ultrasonic bonding tool to be positioned at arbitrary positions within a workspace containing a workpiece, and at arbitrary angular orientations, thus enabling the tip of the bonding tool to be positioned at a first arbitrary bond site location on a workpiece, the tool rotated to align a wire feed bore with a second arbitrary bond site location, and translated thereto to make a second bond, the wire paying out through the wire feed bore without twisting.  
           [0022]    Various other objects and advantages of the present invention, and its most novel features, will become apparent to those skilled in the art by perusing the accompanying specification, drawings and claims.  
           [0023]    It is to be understood that although the invention disclosed herein is fully capable of achieving the objects and providing the advantages described, the characteristics of the invention described herein are merely illustrative of the preferred embodiments. Accordingly, I do not intend that the scope of my exclusive rights and privileges in the invention be limited to details of the embodiments described. I do intend that equivalents, adaptations and modifications of the invention reasonably inferable from the description contained herein be included within the scope of the invention as defined by the appended claims.  
         SUMMARY OF THE INVENTION  
         [0024]    Briefly stated, the present invention comprehends an automatic ultrasonic wire bonding machine which includes an orbital bonding tool support head and automatic means for translating the bonding tool head relative to a workpiece, and independent automatic means for rotating the head, thus enabling a bonding tool tip to form ultrasonic wire bonds at arbitrary locations within a workspace, rotating the tool to desired compass directions, and translating the tool without rotating to a second bond site location. Thus, the ultrasonic wire bonding machine according to the present invention is adapted to bonding wires between arbitrary locations on a workpiece by ultrasonic bonding using a wedge-type ultrasonic bonding tool, without requiring that the workpiece be translated or rotated.  
           [0025]    In a preferred embodiment of an automatic ultrasonic bonding machine with orbital bonding tool head according to the present invention, the orbital bonding tool head is supported by a positioning mechanism for translating the bonding tool head, and therefore the tip of an ultrasonic bonding tool, by drive motors to precisely predeterminable positions within a three-dimensional coordinate space containing a workpiece. The positioning mechanism of the wire bonding machine according to the present invention preferably includes a laterally oriented, upper support frame member or gantry, which supports a generally downwardly tiered or cascaded series of linearly translatable support platforms These include a first, upper X-axis tool support platform supported by a first pair of fore-and-aft opposed, front and rear, laterally disposed, parallel linear slide bearings having crossed rollers. This latter pair of bearings enables the Y-axes platform to be translatable in a fore-and-aft Y-axis direction by a Y-axis driver motor.  
           [0026]    The first, upper, X-axis tool support platform is translatable in a lateral direction by an X-axis drive motor. The positioning mechanism also includes a second, Y-axis translatable tool support platform which is suspended from the X-axis platform, by a second pair of crossed roller bearings. This pair of bearings consists of two fore-and-aft disposed, laterally opposed parallel linear slide bearings having crossed rollers. This latter pair of bearings enables the Y-axis platform to be translatable in a four-and-aft, Y-axis direction by a Y-axis drive motor.  
           [0027]    The positioning mechanism of the wire bonding machine according to the present invention also includes a third, Z-axis support platform which depends downwardly from the Y-axis support platform. The Z-axis support platform is supported from the X-axis platform by a third pair of bearings, consisting of two vertically disposed, fore-and-aft opposed parallel linear slide bearings having crossed rollers. In a preferred embodiment of the machine, the Z-axis support platform bearings are located near front and rear edges of an offset flange plate which depends vertically downwards from a side of the Y-axis supped platform. In an example embodiment, these bearings protrude inwards, i.e., to the right from a flange plate offset to the left side of the Y-axis platform. The Z-axis bearing pair enables the Z-axis platform to be translated in a vertical, Z-axis direction by a Z-axis drive motor.  
           [0028]    The orbital bonding head of the automatic ultrasonic wire bonding machine according to the present invention includes a head support assembly which is mounted to a lower front portion of the Z-axis support platform by a cantilever bar which protrudes forward from the Z-axis support platform. The orbital bonding head assembly includes structural components which rotatably support a head that in turn supports an ultrasonic transducer in which is mounted a bonding tool, particularly a wedge bonding tool, and a clamp mechanism for feeding bonding wire through a wire guide bore disposed obliquely through the bonding tool. The orbital bonding tool head includes a four-bar parallelogram linkage support frame which couples an upper portion of the head to the transducer, tool, and wire feed clamp assembly, the four-bar linkage enabling the tool tip to be displaced only vertically in response to a reaction force produced by translating the tool tip downwardly into contact with a workpiece, thus insuring that the tool tip is not displaced laterally and thus avoiding scuffing the workpiece.  
           [0029]    Novel features of the orbital bonding tool head include minimization of the weight of rotatable components of the head by locating drive motors for head rotation and clamp actuation rearward of the head, on a non-rotating support arm. Bonding wire is fed to the bonding tool from a supply reel fixed to the Y-axis platform, through a bore concentric with the rotating axis of the head, thus insuring that the bonding wire is not twisted when the head is rotated.  
           [0030]    The bonding head is rotatable by an external drive motor coupled by a toothed belt to a spindle-drive sprocket wheel at the upper end of a spindle which supports the head. The head drive motor rotates the head plus and minus 180 degrees, allowing a plane containing the longitudinal axis and wire feed bore axis of the tool to be rotated to any azimuthal direction related to a workpiece.  
           [0031]    The orbital head of the bonding machine also includes a clamp actuator drive motor which is coupled to a hollow shaft which fits concentrically inside the head support spindle by a toothed belt which engages a clamp actuator sprocket which is located above the spindle-drive sprocket wheel. Mounted to a lower end of the hollow clamp-drive shaft is a cam wheel which engages a follower coupled by a bell crank assembly to a wire feed clamp, the jaws of which are alternatively openable and closeable onto feed wire in response to pressurization of a pneumatic actuator. Thus, the novel design of the bonding machine according to the present invention enables the wire feed clamp assembly to be operated independently of rotation angle of the head, thereby minimizing the mass of rotating head components by locating the cramp actuator drive motor off of the head. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]    [0032]FIG. 1 is a front perspective view of a gantry mounted ultrasonic wire bonding machine with orbital bonding tool head according to the present invention.  
         [0033]    [0033]FIG. 2 is a front elevation view of the machine of FIG. 1.  
         [0034]    [0034]FIG. 3 is a rear perspective view of the machine of FIG. 1.  
         [0035]    [0035]FIG. 4 is an upper plan view of the machine of FIG. 1.  
         [0036]    [0036]FIG. 5 is a right side elevation view of the machine of FIG. 1.  
         [0037]    [0037]FIG. 6 is a fragmentary lower left perspective view of the machine of FIG. 1 on an enlarged scale.  
         [0038]    [0038]FIG. 7 is a view similar to that of FIG. 6, but on a further enlarged scale.  
         [0039]    [0039]FIG. 8 is a right side elevation view of the structure of FIG. 6, on a further enlarged scale.  
         [0040]    [0040]FIG. 9 is a fragmentary upper left front perspective view of the machine of FIG. 1, showing an orbital bonding head thereof in a zero-degree orientation, with a wedge bonding tool protruding forward to contact a first bond site on a workpiece.  
         [0041]    [0041]FIG. 10 is a view similar to that of FIG. 9, but showing the orbital bonding head rotated ninety degrees clockwise, and translated to the right, and the bonding tool protruding leftwardly.  
         [0042]    [0042]FIG. 11 is a front elevation view of an orbital bonding tool head assembly for the wire bonder of FIG. 1.  
         [0043]    [0043]FIG. 12 is a left side elevation view of the bonding tool head assembly of FIG. 11.  
         [0044]    [0044]FIG. 13 is a rear elevation view of the bonding tool head assembly of FIG. 11.  
         [0045]    [0045]FIG. 14A is a right side elevation view of the bonding tool head assembly of FIG. 11.  
         [0046]    [0046]FIG. 14B is a fragmentary view of the structure of FIG. 14A, on an enlarged scale and showing wire drag tube of the apparatus.  
         [0047]    [0047]FIG. 15 is a lower plan view of the bonding tool head assembly of FIG. 1.  
         [0048]    [0048]FIG. 16 is an upper plan view of the bonding tool head assembly of FIG. 11.  
         [0049]    [0049]FIG. 17 is a view similar to that of FIG. 16, but showing a cover plate  57   a  installed.  
         [0050]    [0050]FIG. 18 is a fragmentary right side elevation view similar to that of FIG. 14, but showing the head moved downwardly to cause the bonding tool tip to contact a work surface.  
         [0051]    [0051]FIG. 19 is a left side elevation view of the orbital head assembly positioned as shown in FIG. 18.  
         [0052]    [0052]FIG. 20 is a fragmentary lower right-hand perspective view of the bonding tool head assembly of FIG. 11.  
         [0053]    [0053]FIG. 21 is a fragmentary lower rear perspective view of the bonding tool head assembly of FIG. 11.  
         [0054]    [0054]FIG. 22 is a fragmentary lower perspective view of the bonding tool head of FIG. 11, showing the eccentric surface of a wire feed clamp cam wheel at a minimum radius spacing relative to a rear laterally disposed cam follower.  
         [0055]    [0055]FIG. 23 is a fragmentary lower perspective view similar to that of FIG. 22, but showing the maximum radius of the cam wheel directed rearward, thus causing an upper laterally disposed bell crank arm to be displaced to a maximum rearward position, and a rear upwardly disposed vertical arm of the bell crank and attached rear portion of forward protruding clamp support bar to pivot downwardly relative to a lower, largest left-hand bar of a four-bar linkage.  
         [0056]    [0056]FIG. 24 is a fragmentary longitudinal sectional view of the head configured as shown in FIG. 22, taken along line  24 - 24 .  
         [0057]    [0057]FIG. 25 is a fragmentary longitudinal sectional view similar to that of FIG. 24, but showing the wire feed clamp disposed as shown in FIG. 23, and taken along line  25 - 25  of FIG. 23.  
         [0058]    [0058]FIG. 26 is a fragmentary upper plan view of the structure of FIG. 25, on a somewhat enlarged scale and showing details of the wire clamp mechanism.  
         [0059]    [0059]FIG. 27 is a front elevation view of the structure of FIG. 26.  
         [0060]    [0060]FIG. 28 is a longitudinal sectional view of the structure of FIG. 27, taken along line  28 - 28 .  
         [0061]    [0061]FIG. 29 is a fragmentary and partly schematic longitudinal sectional view of the article of FIG. 25, on an enlarged scale and showing a length of bonding wire disposed between jaw clamp blade and into a wire feed bore in a bonding tool.  
         [0062]    [0062]FIG. 30 is a view similar to that of FIG. 29, but showing the wire feed clamp blades closed to clamp on a wire preparatory to feeding it forward, and showing the wire feed clamp beginning to push wire through the wire feed bore of the bonding tool.  
         [0063]    [0063]FIG. 31 is a view similar to that of FIG. 30, but showing the clamp moved forward to thus push the wire through the front exit opening of the bonding tool.  
         [0064]    [0064]FIG. 32 is a fragmentary lower plan view of the bonding tool head of FIG. 11, similar to that of FIG. 15, but showing the head orbited 90 degrees clockwise as viewed from above, i.e., 90 degrees counterclockwise in FIG. 32.  
         [0065]    [0065]FIG. 33 is a fragmentary upper plan view showing the head orbited an additional 90 degrees for a total of 180 degrees clockwise from its position in FIG. 16 and viewed from above.  
         [0066]    [0066]FIG. 34 is a lower plan view of the bonding head of FIG. 11, showing the head orbited 90 degrees counterclockwise as viewed from below, i.e., to a position 270 degrees clockwise from the position shown in FIG. 16, as viewed from above.  
         [0067]    [0067]FIG. 35 is a partly schematic, right-hand view of the orbital bonding tool head of FIG. 11, showing elements of a linkage mechanism thereof.  
         [0068]    [0068]FIG. 36 is a view similar to that of FIG. 35, but showing elements of the linkage mechanism and a bonding tool attached thereto translated upwardly an exaggerated distance in response to downward motion of the head causing contact of the bonding tool tip with a workpiece.  
         [0069]    [0069]FIG. 37 is a left-hand view showing the structure of FIG. 35.  
         [0070]    [0070]FIG. 38 is a left-hand view showing the structure of FIG. 36. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0071]    FIGS.  1 - 38  illustrate a gantry mounted ultrasonic wire bonding machine with orbital bonding tool head according to the present invention. The embodiment of the invention shown in the figures includes an underlying support structure for the gantry, which enables the machine to be supported on the upper surface of a structure such as a bench. However, as will be clear from the ensuing description, the novel design and construction of the machine according to the present invention particularly well adapts the machine to be located completely above a plane containing a workpiece, as for example, by being suspended from an overlying support structure and located over a work area of larger lateral extent, e.g., a conveyor.  
         [0072]    In preferred embodiments of an ultrasonic wire bonding machine with orbital bonding tool head according to the present invention, an orbital bonding tool head is supported by a vertically downwardly cascaded series of support platforms which are translatable with respect to a workpiece located below the head. Each of the platforms is supported by a separate pair of parallel, spaced apart linear bearing ways in which are fitted crossed cylindrical roller bearings. Each pair of linear bearings is disposed in a particular coordinate direction, e.g., laterally, for an X-axis platform, longitudinally for a Y-axis platform, and vertically for a Z-axis platform, the latter platform in turn supporting an orbital bonding tool head. Moreover, each of the platforms is translatable with respect to an overlying support structure or platform by a separate motor drive mechanism. In a preferred embodiment, the Y-platform and X platform motor drive mechanisms each include a lead screw or jack screw driven by a stepper motor mounted onto a support member, the screw threadingly engaging a follower nut mounted on the translatable platform. Also in the preferred embodiment, the Z-axis motor drive mechanism includes a spiral cam wheel driven by a stepper motor mounted on a support platform, and a roller bearing follower riding on the cam wheel and attached to the Z-axis platform.  
         [0073]    Details of the structure and function of the aforementioned bearings and motor drive mechanisms are substantially similar to those described in the present inventor&#39;s co-pending U.S. patent application Ser. No. 09/570,196, filed May 12, 2000, for an Automatic Ultrasonic Bonding Machine With Vertically Tiered Orthogonally Translatable Tool Support Platforms. Accordingly, the entire specification of the aforementioned co-pending U.S. patent application is hereby incorporated by reference into the present specification.  
         [0074]    Referring now to FIGS.  1 - 10 , a gantry mounted ultrasonic bonding machine  50  according to the present invention may be seen to include a positioning and actuating mechanism indicated generally by the numeral  51 . As shown in FIG. 1, machine  50  includes a laterally elongated, generally rectangularly-shaped upper horizontal support member or gantry  52 . Gantry  52  may be supported by any suitable means as for example, by support members located above the gantry. However, in the embodiment shown in FIG. 1, gantry  52  is supported by a pair of laterally spaced apart, vertically disposed, parallel support walls  52 L,  52 R which depend perpendicularly upwards from a base plate  52 B, and which are fastened to the underside of the gantry. This arrangement enables bonding machine  50  to be used in bench-top applications.  
         [0075]    Referring still to FIGS.  1 - 10 , it may be seen that bonding machine  50  includes a first, upper X-axis support platform  53  laterally translatably mounted to the underside of gantry  52 , and a second, Y-axis platform  54  mounted to the underside of the X-axis support platform in a manner permitting longitudinal, i.e., fore-and-aft, translation of the Y-axis platform relative to the X-axis platform. As may be seen best by referring to FIGS. 6 and 7, bonding machine  50  includes a third, Z-axis platform  55  vertically translatably mounted to the right side of a flange plate  55 A which depends vertically downwardly from the Y-axis platform  54  near the left edge wall of the Y-axis platform. Also, as may be seen best by referring to FIGS.  12 - 14  in addition to FIGS. 6 and 7, bonding machine  50  includes an orbital bonding head  56 . The latter is supported near the forward end of an orbital bonding tool head support assembly  57  which includes a rearwardly protruding cantilever support beam  58  that is attached near a rear end portion thereof to Z-axis platform  54 .  
         [0076]    As shown in FIGS. 1, 6, and  11 - 15 , bonding machine  50  includes an ultrasonic transducer  59  mounted to the underside of an ultrasonic transducer support assembly  60  which depends downwardly from the underside of orbital bonding head  56 , near the front end portion thereof. As shown in FIGS.  11 - 15 , ultrasonic transducer  59  has a longitudinally elongated, generally cylindrically-shaped body  61 , which has a radially inwardly and forwardly tapered front portion  62 . Front portion  62  of transducer  59  has therethrough near front face  63  thereof a vertically disposed bore  64  which holds therein a vertically disposed ultrasonic bonding tool  65 . As may be seen best by referring to FIG. 26 in addition to FIGS. 12 and 14, bonding tool  65  is a wedge-type bonding tool, having a generally cylindrically-shaped upper shank portion  66 , and a generally flat lower working surface or foot  67 . Tool  65  also has therethrough a diagonally disposed wire guide bore  68  which angles rearwardly and upwardly from a front exit opening  69  in foot  67  to a rear entrance opening  70  in shank  66 . Bonding wire payed out from a wire supply reel  71  mounted on Y-axis platform  54  and fed through rear entrance opening  70 , wire guide bore  68 , and front exit opening  69  is pressed against a bonding site by foot  67  of bonding tool  65 , and vibrated at an ultrasonic frequency to ultrasonically weld the end wire to a workpiece surface.  
         [0077]    Referring now to FIGS. 1, 2,  4 - 5 , and  9 - 10 , it may be seen that automatic gantry mounted ultrasonic bonding machine with orbital bonding tool head  50  preferably includes a stereoscopic microscope  72  which enables a human operator to view a workpiece, as for example a workpiece A supported by a pedestal B on table C or conveyor. In a preferred embodiment, microscope  72  is mounted on one end of an articulating arm  73 , the other end of which is attached to gantry  52  near a lateral end thereof, e.g., the left end as shown in the figures. This arrangement enables microscope  72  to be swung to the left of gantry  52 , allowing free access to a workspace containing workpiece A.  
         [0078]    Bonding machine  50  also preferably includes a television camera  74  for forming an electronic image of a workpiece area viewed by the camera, and a monitor  75  connected to the camera for displaying a visual image of the camera field to an operator. Ultrasonic bonding machine  50  also preferably includes a computer (not shown) which contains pattern recognition software effective in processing electronic images of a workpiece formed by camera  74 , and issuing command signals to positioning and actuating components of the machine which cause the bonding tool to make ultrasonic bonds at pre-determined locations of a workpiece referenced to initial sightings of reference features of a workpiece viewed on monitor  75  by an operator. Monitor  75  is also preferably operably interonnected with the computer (not shown) to provide a graphic user interface with the computer which facilitates operation of the machine. The use of a computer and pattern recognition software to position a machine component at pre-determined positions relative to a workpiece is a well-known expedient employed in many automatic manufacturing operations, is well understood by those skilled in the art, and therefore will not be described in detail in this specification.  
         [0079]    Referring now to FIGS.  1 - 10 , it may be seen that positioning and actuating mechanisms  51  includes a positioning mechanism indicated generally by the numeral  78 , which includes structural components suspended from gantry  52 . A primary function of positioning mechanism  76  is to translate bonding tool tip  67  of bonding tool  65  in a three-dimensional coordinate space containing a workpiece to pre-determined points, e.g., sites on the workpiece where ultrasonic bonds are to be made by the machine. An example application of machine  50  is shown in FIG. 1, in which tool  65  is used to make bonds on workpiece A supported by a pedestal B on table C. Positioning and actuating mechanism  76  also includes individual actuator mechanisms indicated generally by the numeral  77  which are attached to orbital bonding tool head  52 , and which are described in detail below.  
         [0080]    Referring now to FIGS. 3 and 5, it may be seen that first, upper X-axis tool support platform  53  of bonding machine  50  is rollably translatably mounted to the underside of gantry  52 . As shown in FIGS. 1, 3 and  4 , gantry  52  has in upper plan view the shape of a laterally elongated rectangularly shaped plate. As is also shown in FIGS. 1 and 3, X-axis tool support platform  53  has protruding upwardly therefrom, near front and rear laterally disposed vertical edge walls  78 ,  79 , front and rear linear bearing ways  80  and  81 , respectively. Each of the two outer facing laterally disposed vertical walls (not shown) of bearing ways  80  and  81  has formed therein laterally disposed, generally V-shaped bearing groove (not shown), the sides of which groove are perpendicular to one another.  
         [0081]    As may be seen best by referring to FIGS. 1 and 3, gantry  52  has protruding downwardly therefrom, near front and rear laterally disposed vertical edge walls  86  and  87  thereof, a pair of front and rear linear bearing ways (not shown). Each of the two inner facing, laterally disposed vertical wails (not shown) of front and rear Z-axis gantry bearing ways (not shown) has formed therein a laterally disposed, generally V-shaped baring groove (not shown), me sides of which groove are perpendicular to one another. The fore-and-aft or longitudinal spacing between outer vertical wall surfaces (not shown) of bearing ways (not shown) protruding upwardly from X-axis platform  53  is slightly less than the longitudinal spacing between the inner facing vertical walls (not shown) of front and rear gantry bearing ways (not shown), which protrude downwardly from gantry  52 , enabling the lower, X-axis platform bearing way pair to be received in the longitudinal space between the upper gantry bearing way pair in parallel alignment therewith. Thus positioned, a V-shaped groove (not shown) if the front surface  82  of a front linear Y-axis platform  53  is laterally aligned with an adjacent V-shaped groove (not shown) in rear surface  92  of a front linear gantry bearing way (not shown), forming therewith a front laterally disposed composite X-axis bearing way (not shown) having a generally rectangularly-shaped cross section. Similarly, grooves (not shown) in rear X-axis platform bearing way  81  and rear gantry bearing way (not shown) form a rear laterally deposed composite X-axis bearing way (not shown). Each of the aforementioned composite bearing ways holds a laterally disposed row of laterally spaced apart, cylindrical roller bearings (not shown) held in a laterally elongated roller bearing cage (not shown). Roller bearings (not shown) are right circular cylinders each having a diameter equal to its height. The orientation of the axes of the cylinders alternate, with the axis of each cylinder being perpendicular to that of an adjacent cylinder. This arrangement of bearings enables translation of X-axis platform  53  in a lateral or X-axis direction with respect to gantry  52 , with a minimum of static and rolling friction, and a minimum degree of fore-and-aft, i.e., longitudinal run-out.  
         [0082]    Machine  50  includes a drive mechanism which utilizes a drive motor to translate X-axis platform  53  relative to gantry  52  under computer control. Thus, as shown in FIGS. 3 and 4, machine  50  includes an X-axis drive mechanism  96  which includes an X-axis stepper motor  97  mounted to gantry  52  and having a rotatable output shaft  98  coupled to an X-axis lead screw  99  coaxial with the output shaft. X-axis drive mechanism  96  also includes a drive block  100  which protrudes rearwardly from a rear face wall  101  of X-axis platform  53 . Drive block  100  has through its thickness dimension a laterally disposed threaded bore  102  which threadingly receives X-axis lead screw by. Thus, when X-axis stepper motor  97  is electrically energized to rotate lead screw  99  in a first rotation direction about it longitudinal axis, drive block  100  and X-axis platform  53  are extended laterally relative to gantry  52  in a first direction, and retracted when the drive motor rotation direction is reversed.  
         [0083]    Referring to FIGS.  1 - 6 , it may be seen that second, Y-axis tool support platform  54  of bonding machine  50  is rollably translatably mounted to the underside of X-axis tool support platform  53 , in a manner which will now be described.  
         [0084]    As shown in FIGS. 4 and 7, X-axis tool support platform  53  has a laterally elongated, generally rectangular shape which conformally underlies gantry  52 . Fastened to the underside of X-axis tool support platform  53  is a longitudinally elongated, generally rectangularly-shaped, horizontally disposed Y-axis support plate  103 . Y-axis support plate has a laterally disposed, vertical front face  104  which is parallel to front vertical face  105  of X-axis platform  53 . As shown in FIG. 3, Y-axis support plate  103  protrudes rearwardly of X-axis platform, having a rear vertical face  105  located rearward of rear vertical face  106  of X-axis platform  53 .  
         [0085]    As shown in FIGS. 1 and 3, Y-axis tool support platform  54  has protruding upwardly therefrom, laterally inwards of left and right longitudinally disposed side walls  107  and  108  thereof, a pair of left and right laterally opposed, longitudinally disposed left and right bearing ways (not shown). Each of the two laterally outwardly located vertical walls (not shown) of bearing ways (not shown) has formed therein a longitudinally disposed, generally V-shaped bearing groove (not shown), respectively, the sides of which grooves ate perpendicular to one another.  
         [0086]    Referring still to FIGS. 1 and 3, it may be seen that Y-axis support plate  103  has protruding downwardly therefrom, laterally inwardly located from left and right longitudinally disposed vertical edge walls (not shown) thereof, a pair of left and right laterally opposed, longitudinally disposed left and right bearing ways (not shown). Each of the two inner facing vertical walls (not shown) of Y-axis support plate bearing ways (not shown) has formed therein a longitudinally disposed, generally V-shaped bearing groove (not shown), the sides of which groove are perpendicular to one another.  
         [0087]    The lateral spacing between outer vertical wall surfaces (not shown) of left and right Y-axis platform bearing ways (not shown) protruding upwardly from Y-axis platform  54  is slightly less than the lateral spacing between the inner facing vertical walls (not shown) of left and right Y-axis support plate bearing ways (not shown) which protrude downwardly from Y-axis support plate  103 . Thus, with Y-axis tool support platform bearing ways (not shown) positioned between Y-axis support plate bearing ways (not shown), composite left and right Y-axis bearing way grooves (not shown) are formed which hold bearings (not shown) in bearing cages (not shown), exactly similar to those described above for X-axis platform  53 . This arrangement enables translation of Y-axis platform  54  in fore-and-aft, i.e., longitudinal directions with respect to X-axis platform  53 , with a minimum of static and rolling friction, and a minimum degree of lateral run-out.  
         [0088]    Machine  50  includes a Y-axis drive mechanism which utilizes a drive motor to translate Y-axis platform  54  relative to X-axis platform  53  under computer control. Thus as shown in FIG. 3, machine  60  includes a Y-axis drive  122  mechanism which includes a Y-axis stepper motor  123  mounted to Y-axis support plate  103 . Y-axis stepper motor  123  has an output shaft  124  which protrudes rearwardly of Y-axis support plate  103 , and a toothed drive pulley  125  pinned to the output shaft Y-axis drive mechanism  122  also includes a longitudinally disposed lead screw  126  rotatably mounted in front and rear bearing blocks  127  and  128  which protrude laterally outwardly from the right side of Y-axis support platform  103 . Lead screw  126  has pinned to a rear longitudinal end thereof a toothed drive pulley  129  which is driven by stepper motor drive pulley  125  through a toothed drive belt  130  which encircles the two pulleys.  
         [0089]    Referring still to FIG. 3, it may be seen that Y-axis drive mechanism  122  includes a drive block  131  which protrudes laterally outwards from Y-axis platform  54 . Drive block  131  has through its thickness dimension a longitudinally disposed threaded bore  132  which threadingly receives Y-axis lead screw  126 . With this arrangement, when Y-axis stepper motor  123  is electrically energized to rotate lead screw  125  in a first rotation direction, drive block  13  and Y-axis platform  54  are extended longitudinally forwardly of X-axis platform, and retracted rearwardly when the drive motor rotation direction is reversed.  
         [0090]    Referring now to FIGS. 1 and 6- 8 , it may be seen that third, Z-axis tool support platform  55  of bonding machine  50  is rollably translatably mounted to the underside of Y-axis tool support platform  54 , in a manner which will now be described.  
         [0091]    As shown in FIGS. 1 and 6- 8 , Y-axis tool support platform  54  has protruding perpendicularly downwardly from lower surface  134  thereof, and near left longitudinally disposed vertical edge wall  135  thereof, a Z-axis support flange plate  136 . The latter has a generally square outline, and generally vertically disposed flat outer and inner parallel wall surfaces  137 ,  138 , respectively. As may be seen best by referring to FIGS.  8  Z-axis platform  55  includes a longitudinally disposed left-hand vertical plate portion  139  having a generally square outline and generally vertically disposed, parallel outer (left-hand) and inner (right-hand) wall surfaces  140 ,  141 . Z-axis platform  55  also has a laterally disposed front plate portion  142  which has a rear vertically disposed surface  143  and a front vertically disposed surface  144 , to which is mounted orbital bonding head  56 , in a manner described below. Front plate portion  142  of Z-axis platform  55  is disposed laterally inwardly, i.e., to the right in FIGS.  6 - 8 , of left-hand, longitudinally disposed plate portion  139 .  
         [0092]    As shown in FIGS.  6 - 8 , Z-axis support flange plate  136  has protruding laterally inwardly therefrom, a longitudinally opposed pair of parallel front and rear vertically disposed bearing ways  145 ,  146 , located near front and rear vertical edge walls  147 ,  148 , respectively, of the Z-axis platform. Front and rear Z-axis support flange late bearing ways  145 ,  146  have rear and front facing surfaces (not shown), respectively, each of which has formed therein a vertically disposed, generally V-shaped bearing groove (not shown), the sides of each of which grooves are mutually perpendicular.  
         [0093]    Referring still to FIGS.  6 - 8 , it may be seen that Z-axis support platform  55  has protruding laterally outwardly (to the left in FIGS.  1 - 3 ) a longitudinally opposed pair of front and rear vertical bearing ways (not shown), located inwardly of front and rear vertical edge walls  155 ,  156 , respectively, of the Z-axis support flange plate. Front and rear Z-axis platform bearing ways (not shown), have front and rear surfaces (not shown), each of which has formed therein a vertically disposed, generally V-shaped bearing groove (not shown), the sides of each of which groove are mutually perpendicular.  
         [0094]    The longitudinal, i.e., fore-and-aft spacing between outer vertical wall surfaces (not shown) of front and rear Z-axis support platform bearing ways (not shown) protruding laterally outwardly from Z-axis support platform  55  is slightly less than the longitudinal spacing between inner facing vertical walls (not shown) of front and rear Z-axis support flange plate bearing ways  145 ,  146  which protrude laterally inwardly from Z-axis support flange plate  136 . Thus, with Z-axis support platform bearing ways (not shown) positioned between Z-axis support flange plate bearing ways  146 ,  146 , composite front and rear Z-axis bearing way grooves (no shown), are formed which hold bearings (not shown) in bearing cages (not shown), exactly similar to those described above for X-axis platform  53 . This arrangement enables translation of Z-axis platform  55  in up-and-down, i.e., plus and minus Z directions with respect to Y-axis platform  54 , with a minimum of static and rolling friction, and a minimum degree of fore-and-aft, or longitudinal run-out.  
         [0095]    Machine  50  includes a Z-axis drive mechanism which utilizes a drive motor to translate Z-axis platform  55  relative to Y-axis platform  54  upwardly and downwardly in plus Z and minus Z directions, respectively. Thus, as shown in FIGS. 1 and 6- 8 , machine  50  has a Z-axis drive mechanism  164  which includes a Z-axis stepper motor  164  mounted to a Z-axis motor support plate  165  that protrudes perpendicularly downwardly from Y-axis tool support plate  54 , rearward of Z-axis support flange plate  136 . As shown in FIGS.  6 - 8 , Z-axis stepper motor  164  has an output shaft  166  which protrudes forward of Z-axis motor support plate  165 , through a bore [ 166 ] (not shown) disposed longitudinally through the motor support plate. Z-axis stepper motor output shaft  166  has pinned thereto near the front end thereof a spiral cam wheel  167  having a uniform longitudinal thickness and spiral plan view shape.  
         [0096]    As may be seen best by referring to FIG. 8, Z-axis drive mechanism  163  also includes a roller bearing follower  168  which protrudes rearwardly from rear edge wall  169  of Z-axis platform  55 , in vertical alignment with the longitudinal axis of stepper motor output shaft  165 , and in longitudinal alignment with cam wheel  167 . With this arrangement, when Z-axis drive stepper motor  164  is energized to rotate cam wheel  167  to an angular position in which the largest radius surface of the cam wheel is vertically above and aligned with motor shaft  166 , as shown in FIG. 8, cam follower  168  and Z-axis platform  55  are elevated to their maximum height in a plus-Z direction. Conversely, when stepper motor  164  is energized to rotate cam wheel  167  so that a smaller radius surface of cam wheel  167  is contacted by cam follower  168 , the weight of the Z-axis platform and components mounted thereto causes the Z-axis platform to move downwardly, i.e., in a minus-Z direction.  
         [0097]    The novel structure and function of orbital bonding tool head assembly  56  may be best understood by referring to FIGS.  11 - 37 . Referring first to FIGS. 4 and 6, in addition to FIGS.  11 - 16 , it may be seen that orbital bonding tool head assembly  56  includes a support assembly  57  which has depending downwardly from a front end portion thereof a rotatable bonding tool head  171 . As shown in FIGS. 12 and 15, orbital bonding tool head assembly support assembly  57  has a longitudinally elongated support beam member  172 , which includes a rear vertically oriented plate-like portion  173  having parallel, vertical right and left side walls  174 ,  175 , respectively. As shown in FIG. 4, rear plate-like member  173  serves as a cantilever mount for orbital head support assembly  57 , being secured to the right-hand side of a vertical support wall  174 , which protrudes forward from Z-axis platform  55  near the left side thereof, by bolts  176  which pass through holes  177  disposed transversely through the rear plate-like beam member.  
         [0098]    As may be seen best by referring to FIGS. 12, 15, and  16 , rear plate portion  173  of support beam member  172  has a generally flat vertical rear face  178 , and is terminated at a front transverse end  179  thereof by a laterally thickened, block-shaped portion  180  which has a generally rectangular shape. Block-shaped portion  180  has one longitudinally disposed vertical face, e.g., a right face  181  which is coextensive with right face  174  of rear plate-like portion  173  of beam  172 . Block-shaped portion  180  of support beam member  172  also has a second longitudinally disposed face, e.g., a face  182  left, which is parallel to left vertical face  175  of rear plate portion  173  of beam  172 , but offset laterally outwardly, i.e., to the left of the rear left face, being joined thereto by a transversely disposed, vertical abutment face  183 .  
         [0099]    As may be seen best by referring to FIGS. 12 and 16, support beam member  172  of orbital head support assembly  57  includes a front longitudinally disposed beam member  184  which protrudes perpendicularly forward from front vertical transverse face  185  of block-shaped portion  180  of beam member  172 . Front beam member  184  has a horizontal, longitudinally disposed upper face  186  which is coextensive with upper face  187  of block-shaped portion  180  of support beam  172 . Moreover, upper face  187  of block-shaped portion  180  is coextensive with upper face  188  of rear vertical plate portion  173  of beam support member  172 .  
         [0100]    As may be seen best by referring to FIG. 12, front longitudinally disposed beam member  184  is of a generally uniform vertical thickness, less than that of block-shaped portion  180  of support beam member  172 . Thus, front longitudinally disposed beam member  184  has a flat, horizontally disposed lower surface  189  parallel to upper surface  186  of the front beam member, which is offset vertically upwards from the lower surface  190  of block-shaped portion  180  of support beam member  172 .  
         [0101]    As may be seen best by referring to FIGS. 11, 12, and  14 A, front longitudinally disposed beam member  184  has formed in the front end portion thereof a circular cross section boss  191  which has a flat lower face  192  that is parallel to and offset vertically downwards of lower face  189  of the front longitudinally disposed beam member. Boss  191  has a front vertically disposed, generally circular arc-shaped front face  193  which comprises the front end face of front support beam member  184 .  
         [0102]    As shown in FIGS. 11, 12,  14 A, and  16 , orbital bonding tool head  171  of orbital bonding tool head assembly  56  has a generally cylindrically-shaped upper base portion  194  which has a flat, horizontally disposed upper face  195 . Upper base portion  194  of bonding tool head  171  is mounted concentrically below boss  191  by a spindle  196  which is rotatably held within a bore  197  disposed vertically through the boss. For reasons which are described below, spindle  196  has a hollow cylindrical shape, having through its length a bore  198 .  
         [0103]    As shown in FIGS.  11 - 14 A, spindle  196  protrudes upwardly of upper face  186  of front longitudinal beam member  184  through bore  197 , and has pinned concentrically thereto a first, lower, spindle-drive toothed pulley  199 , and a first lower spindle-drive shaft angle encoder disk  200 , located below the pulley. As shown in the same figures, orbital bonding tool head assembly  56  includes a first, spindle-drive stepper motor  201  fastened to right side  174  of central block-shaped portion  180  of upper beam member  172 . Spindle-drive stepper motor  201  has a vertically disposed output shaft  202  which protrudes upwardly of upper face  203  of the stepper motor, to which shaft is pinned a toothed drive pulley  204 . The latter is coupled to spindle pulley  199  by a first endless flexible toothed, spindle-drive belt  205 .  
         [0104]    As may be seen best by referring-to FIGS.  26 - 28 , in addition to FIGS.  11 - 16 , orbital bonding tool head assembly includes a wire feed clamp assembly  206  including a pair of wire clamp jaws  207  located rearward of ultrasonic bonding tool  65 , and means for longitudinally reciprocally translating the clamp fore-and-aft relative to the bonding tool, as will now be described.  
         [0105]    As shown in FIGS. 11 and 12, wire feed clamp assembly  206  includes a vertically disposed, hollow drive shaft  208  which is rotatably held within bore  198  which extends axially through head drive spindle  196 , concentric therewith. As shown in FIG. 11, head clamp assembly drive shaft  208  protrudes perpendicularly outwardly below lower transverse face wall  209  of upper base support portion  194  of orbital bonding tool head  171 .  
         [0106]    As may be seen best by referring to FIGS.  22 - 25  in addition to FIG. 11, a circular cam wheel  210  is eccentrically mounted to that portion of drive shaft  208  which protrudes downwardly from lower face wall  209  of upper base support portion  194  of head  171 . As is also shown in those figures, drive shaft  208  has extending through its length a coaxial central wire feed bore  211  which has a lower exit opening  212  located above clamp jaws  207 . The function of cam wheel  210  and wire feed bore  211  will be described later.  
         [0107]    FIGS.  11 - 13  illustrate a mechanism for rotating clamp-drive shaft  208  and cam wheel  210 . As shown in FIGS. 11 and 12, clamp-drive shaft  208  protrudes upwardly above first, lower spindle-drive toothed pulley  199 , and has pinned thereto a second, upper clamp-drive pulley  214 , and a second, upper clamp-drive shaft angle encoder disk  215 , located above the pulley. As shown in the figures, the clamp-drive mechanism includes a second, clamp-drive stepper motor  216  fastened to the left side  182  of central block-shaped portion  180  of upper beam member  172 . Clamp-drive stepper motor  216  has a vertically disposed output shaft  218  which protrudes upwardly of upper face  219  of the stepper motor, to which shaft is pinned a toothed drive pulley  220 . The latter is coupled to clamp-drive pulley  214  by a second endless flexible toothed, clamp-drive belt  221 .  
         [0108]    As may be seen best by referring to FIG. 13, both spindle-drive stepper motor  201  and clamp-drive stepper motor  216  are provided with shaft angle encoders. Thus, as shown in FIGS. 13, a lower end of output shaft  202  of spindle-drive stepper motor  201  protrudes below lower end plate  222  of the drive motor, to which protruding shaft end is pinned a spindle-drive motor shaft angle encoder disk  223 . An outer edge of encoder disk  223  is rotatable within a slot provided in an optical pick-off assembly  224 , which contains a light source such as an LED and a photodetector such as a photo-transistor, for providing electrical signals when the disk is rotated to positions which allow light to pass through encoding apertures provided through the disk and impinge on the photodetector. Similarly, clamp-drive stepper motor  216  has a lower output shaft end  218  which protrudes below lower end plate  225  of the drive motor, to which protruding shaft end is pinned a clamp-drive motor shaft angle encoder disk  226 . An outer edge of encoder disk  226  is rotatable within a slot provided in optical pick-off assembly  227 , which contains a light source such as an LED and a photodetector such as a photo-transistor, to provide electrical signals when the disk is rotated to positions which allow light to pass through encoding apertures provided through the disk and impinge on the photodetector.  
         [0109]    Machine  50  according to the present invention includes a novel linkage assembly which suspends transducer mount assembly  60  from cylindrical upper base portion  194  of bonding tool head  171 . As will be described in detail below, the novel linkage assembly enables orbital bonding tool head assembly  56  to be translated vertically downwards toward a workpiece and thereby cause tip  67  of ultrasonic bonding tool  65  to contact the workpiece, in a manner which enables the tool tip to move resiliently upwards relative to the bonding tool head in response to downwardly directed bonding forces exerted by the tool on the workpiece. As shown in FIGS.  35 - 38 , the novel design and construction of linkage assembly  228  also positions wire feed bore  211  and the axis of bonding tool  65  collinearly with the rotation axis of head-drive spindle  196  thus allowing the head to be orbited to any angle without twisting bonding wire, yet still constraining the bonding tool tip to move resiliently and solely in a vertical direction in response to bonding forces, and thereby preventing the tool tip from scuffing a bonding site. Moreover, the novel design and construction of linkage assembly  228  enables wire feed clamp assembly  206  to function properly for any vertical displacement of the bonding tool tip relative to the bonding head.  
         [0110]    Referring now to FIGS.  11 - 14 A and  35 - 38 , bonding tool head  171  of ultrasonic bonding machine  50  may be seen to include a linkage assembly  228  which supports ultrasonic transducer  59  from upper support base  194  of the bonding tool head. As may be seen best by referring to FIGS. 11 and 14A, upper support base  194  has protruding from the right side  229  thereof a downwardly depending, relatively large, wedge-shaped right-hand support plate  230  having parallel vertically disposed right (outer) and left (inner) faces  231 ,  232 , respectively. Right-hand support plate  230  has a relatively wide upper end, which tapers downwardly to a lower end having less longitudinal width.  
         [0111]    As shown in FIGS. 11 and 12, upper support base  194  has protruding from the left side  233  thereof a downwardly depending, relatively short left support plate  234  having parallel vertically disposed left (outer) and right (inner) faces  235 ,  236 , respectively.  
         [0112]    As shown in FIGS. 11, 14A, and  35 , right-hand vertical support plate  230  has pivotably fastened to right-hand face  231  thereof a first, lower right horizontal linkage bar  237 . The latter has a parallel vertically disposed right (outer) and left (inner) faces  238 ,  239 , respectively. As shown in FIGS. 11 and 14A, lower right linkage bar  237  is connected to right-hand vertical support plate  231  by a first, lower front right pivot joint  240  having a transversely disposed pivot axle  241  which enables the lower right linkage bar to pivot in a vertical plane relative to right vertical support plate  230 .  
         [0113]    As may be seen best by referring to FIGS. 14A, 15,  21 , and  35 , lower right-hand linkage bar  237  is pivotably coupled at a rear end thereof by a lower left rear pivot joint  237 A having a transversely disposed pivot axis  237 B to a transducer support block  242 . The latter has a substantially great lateral thickness, and an L-shaped uniform cross section including a forwardly disposed lower horizontal leg section  243 , and an upstanding rear vertical leg section  244 . As may be seen best by referring to FIGS. 12, 14A and  15 , transducer support block  242  has formed in front horizontally disposed leg section  243  thereof a transversely centrally located, generally rectangularly-shaped front slot  245  which extends rearwardly of front face  246  of the leg section, the slot penetrating lower face  247  of the transducer support block. Also, transducer support block  242  has formed therein a transversely centrally located, generally rectangularly-shaped rear slot  248  of greater width than front slot  245 , the rear slot extending forward from rear face  249  of the transducer support block, penetrating lower face  247  of the support block and communicating with front slot  245 . Rear and front slots  248  and  245  provide clearance for a cylindrically-shaped rear stack  250  of piezoelectric disks comprising part of ultrasonic transducer  59 , and for cylindrically-shaped intermediate longitudinal portion  61  of the transducer, respectively. Intermediate longitudinal portion  61  of transducer  59  is secured within a circular aperture  251  provided through a transversely disposed clamp plate  252 . The latter is located at a vibration node of transducer  59 , and is secured to front face  246  of transducer support block  242 , by screws  243 A for example. As shown in FIG. 15, transducer support block  242  has vertically disposed, parallel right and left faces  253 ,  254 , respectively.  
         [0114]    Referring now to FIGS. 11, 12,  15 , and  37 , it may be seen that linkage assembly  228  for suspending transducer mount assembly  60  from upper head support base member  194  includes a second, lower left horizontal linkage bar  255 . The latter has longitudinally disposed parallel, vertical, left (outer) and right (inner) faces  256 ,  257 , respectively. As shown in FIGS. 12 and 15, lower left linkage bar  255  is secured irrotationally to transducer support block  242  by a pair of longitudinally spaced apart and aligned Allen screws  258 , in parallel alignment with lower face  247  of the transducer support block.  
         [0115]    Referring now to FIGS. 35 and 37 in addition to FIGS. 12 and 15, it may be seen that lower left linkage bar  255  is longer than lower right linkage bar  237 . Thus, as shown in FIG. 15, lower right-hand linkage bar  237  has a convex arcuately curved front face  258  which is located just slightly forward of bonding tool tip  67 , while lower left linkage bar  255  has a similarly shaped front face  259  which is located substantially forward of the bonding tool tip.  
         [0116]    As shown in FIGS. 11, 12,  15 , and  24 ,  25 , an L-shaped left front bell crank  260  is pivotably coupled to a front end portion  261  of lower left horizontal linkage bar  255 , in a manner which will now be described. Bell crank  260  serves to couple eccentric motion of cam wheel  210  to clamp jaws  207 , as will be described below.  
         [0117]    Referring to FIGS. 12, 15, and  24 , it may be seen that L-shaped front left bell crank  260  has a generally longitudinally disposed, forwardly protruding lower front portion  262 , and a rear upstanding portion  263  which depends perpendicularly upwards from the rear end of the front portion. Lower left linkage bar  255  is pivotably connected near front end  259  thereof to longitudinally disposed portion  262  of L-shaped bell crank  260 , near their respective front ends, by a lower left front pivot joint  264  having a transversely disposed pivot axle  265  which enables relative pivotable motion in a vertical plane between the lower left linkage bar and the L-shaped bell crank.  
         [0118]    As shown in FIGS. 11 and 24 rears upwardly disposed portion  263  of L-shaped bell crank  260  has an upper rear transversely disposed generally rectangular bar-shaped arm  266  which protrudes perpendicularly inwardly from vertical portion  262 , i.e., to the right in FIG. 11. Arm  266  has protruding longitudinally forward of the front, transversely disposed vertical, surface  267  thereof, near inner longitudinally disposed vertical end face  288  thereof, a boss  269  having disposed laterally therethrough a transversely disposed cam follower axe bore  291 . The latter protrudes perpendicularly rightward from boss  269  rearwards of cm wheel  210 . A cam follower comprising a roller bearing  290  is rotatably mounted on axle  291 , and has a front vertical tangent surface which is urged against rear peripheral surface  293  of cam wheel  210  by a tension spring  270 . Thus, as shown in FIGS. 24 and 25, tension spring  270  is disposed longitudinally between front hook  270 A which protrudes downwards from base  194  of bonding tool head  271  and a rear hook  270 A which protrudes forward from upper bell crank arm  266 , thus urging the upper bell crank arm and cam follower  290  forward. This arrangement enables upstanding vertical upper portion  263  of L-shaped left front bell crank  260  to pivot in a vertical plane relative to upper boss portion  194  of head  171 , in response to eccentric rotation of cam wheel  210 .  
         [0119]    Referring now to FIGS. 11, 12 and  37 , it may be seen that linkage assembly  228  includes a fourth, upper ft longitudinal linkage bar  273 . Upper left linkage bar  273  has generally parallel, longitudinally disposed vertical left (outer) and right (inner) fares  274 ,  275 , respectively. Upper left linkage bar  273  is pivotably connected near a front end thereof to short left-hand support plate  234 , which depends downwardly from the left side of upper bonding tool head support bar  194 , by a front upper left pivot joint  276 , which has a transversely disposed pivot axle  277 . Also, upper let linkage bar  273  is pivotably connected near a rear end thereof to rear upstanding portion  244  of L-shaped transducer support block  242 , near an upper end of  244 , by a rear upper left pivot joint, the latter having a transversely disposed pivot axle  279 . Front and rear pivot joints  276 ,  278  enable front and rear ends of upper left horizontal linkage bar  273  to pivot in a vertical plane relative to upper bonding tool head support base  194  and transducer support block  242 , respectively.  
         [0120]    Linkage assembly  228  enables tip  67  of bonding tool  65 , which is located below and axially aligned with the rotation axis of head support spindle  196 , to translate resiliently upwardly along that axis, with no radial motion component which might cause the tool tip to scuff a bonding site. Thus, as shown in FIGS.  18 - 20  and particularly FIGS. 36 and 38, when orbital bonding head assembly  56  is translated downwardly to press tool tip  67  against a workpiece A with a predetermined force to effect a bond, the tool tip, ultrasonic transducer  59 , and ultrasonic transducer support block  242  all translate vertically upwards with respect to upper support base  194  for bonding tool head assembly  171 . As shown in FIGS. 20, 36 and  38 , this resilient response motion occurs with lower surface  281  of lower left horizontal linkage bar  255  positioned parallel to the surface of workpiece A. Therefore, since rear surface  282  of ultrasonic transducer support block  242  is perpendicular to lower linkage bar surface  281 , that surface translates in a vertical plane, while L-shaped linkage bar  260  and upper left linkage bar  273  pivot about their respective pairs of end joints, as shown in FIGS. 20, 36 and  38 . Also, during this motion, as shown in FIGS. 16 and 36, lower right longitudinal linkage bar  237  pivots in a vertical plane about front pivot joint  241  relative to right-hand support plate  230 , while the rear end of the lower right longitudinal linkage bar pivot in a vertical plane with respect to transducer support block  242 .  
         [0121]    [0121]FIGS. 11, 12,  21 , and  23 - 29  show details of the structure and function of wire feed clamp assembly  206 .  
         [0122]    Referring first to FIG. 12, wire  283  from a wire supply spool  284  is fed through the upper entrance opening  285  of wire guide bore  211  which extends axially through the entire length of spindle  196  and cam wheel drive shaft  208 . As shown in FIG. 14B, automatic wire bonding machine  50  includes a drag tube  300  for frictionally resisting motion of wire supplied from wire supply spool  284  and fed through wire guide bore  68  of ultrasonic bonding tool  65 . This frictional resistance, or drag, is created by friction between the wire and the inner wall surface of a capillary bore through the drag tube. As shown in FIG. 14B, drag tube  300  consists essentially of an elongated tube of uniform cross section having a straight lower portion  301  which is secured in a bore  287  disposed vertically through ultrasonic transducer  59 . Drag tube  300  also has an arcuately curved intermediate portion  302  which connects at its lower end to straight lower portion  301 , and at its upper end to a relatively straight front end portion  303  which angles upwardly and forwardly from the intermediate portion.  
         [0123]    Drag tube  300  has disposed through its length a small diameter, i.e., capillary, bore  304 . In an example embodiment, drag tube  300  has an outer diameter of 0.028 inch, and bore  304  has a diameter of about 0.016 inch, i.e., about 0.0144 inch larger than the 0.00125 inch diameter of gold bonding wire machine  50  is intended to be used with.  
         [0124]    As shown in FIGS. 12 and 14B, front portion  303  of drag tube  300  is angled at about 60 degrees upwardly and forwardly from lower vertical portion  301  of the drag tube, and has an upper entrance opening  305  located below and rearward of the lower exit opening  306  of wire guide bore  211  through wire feed clamp drive shaft  208 . With this arrangement, wire  283  exiting from lower exit opening  306  of wire guide bore  211  angles rearward and enters opening  305  of bore  304  through drag tuber  300 , and is bent sufficiently in transition section  302  of the drag tube for a frictional retarding force to be exerted on the wire by the capillary bore walls, the force being smaller than required to bend the wire beyond its elastic limit. Wire exiting vertically from bottom exit opening  305  of capillary bore  304  through drag tube  300  angles downwardly and forwardly between left and right wire clamp blades  207 L,  207 R. A front end portion of wire  283  protruding forward from clamp blades  207 L,  207 R enters a rear entrance opening  70  of wire feed guide bore  68  disposed diagonally through ultrasonic bonding tool  65 , exits that bore through front exit opening  69  of the bore, and underlies front lower working face or toe  67  of the bonding tool.  
         [0125]    As described above and shown in FIGS. 11, 24, and  25 , wire feed mechanism  206  includes a cam follower comprising a circular roller bearing  290  having a transversely disposed bearing axle  291 , the roller bearing having an outer circumferential surface  292  which resiliently contacts an outer circumferential surface  293  of eccentrically mounted, circular cam wheel  210 . Since the axis of rotation of cam wheel  210  is vertically disposed, a tangent plane defining the contact area of cam follower surface  290  with cam wheel surface lies in a vertical plane. As shown in FIGS. 24 and 25, this arrangement enables cam follower bearing  290  to precisely track eccentric rotation of cam wheel  210 , for various relative vertical displacements between the cam follower and cam wheel, as long as the cam follower longitudinally contacts some portion of the surface of circumferential cam wheel  210 .  
         [0126]    FIGS.  35 - 38  illustrate the novel construction and function of linkage mechanism  228 , which enables bonding tool  65  to be located colinearly below the rotation axis of orbital bonding tool head  171  and axially aligned with the vertical translation axis of the head, yet constrains tip  67  of the bonding tool to move resiliently upward solely along the common axis of vertical translation and rotation, when the head is translated downwardly to contact a workpiece with the tip of the bonding tool.  
         [0127]    As shown in FIGS.  35 - 38 , novel linkage mechanism  228  includes a first, lower right longitudinally disposed linkage bar  237  pivotably coupled at a front end thereof by a first, lower right pivot joint  240  to vertically disposed plate member  231 . First linkage bar  237  is pivotably coupled at a rear end thereof to the right-hand face of a second, laterally disposed rear bar member  242  having a relatively thick, L-shaped cross section, by a second, lower right rear pivot joint  237 A.  
         [0128]    As shown in FIGS. 37 and 38, linkage mechanism  228  includes a third, lower left longitudinally disposed linkage bar  255  which is rigidly coupled at right angles to the left side of laterally disposed rear bar member  242 . The front end of lower left longitudinally disposed linkage bar  255  is not required to be connected to any other element of linkage mechanism  228 . Accordingly, linkage bar  255  can be of any length, and, as shown in FIGS. 37 and 38, may extend substantially forward of other elements of the linkage mechanism and provide a pivot attachment point  264  for L-shaped bell crank  260  of wire clamp assembly  206 .  
         [0129]    As shown in FIGS. 37 and 38, linkage mechanism  228  according to the present invention includes a fourth, upper left, longitudinally disposed linkage bar  273 . Linkage bar  273  is pivotably coupled at a rear end thereof to the left side of rear transverse linkage bar  242 , near the upper end thereof, by a pivot joint  278 . Also, linkage bar  273  is coupled near a front end thereof by a pivot joint  276  to the left side of upper base portion  194  of bonding tool head  171 . With this novel construction of linkage mechanism  228 , as shown in FIGS.  34 - 37 , the lower surface of rear transverse linkage bar  242 , which supports ultrasonic transducer  59 , is constrained to remain horizontal as the rear linkage bar translates vertically with respect to upper base portion  194 , thus ensuring that tip  87  of bonding tool  65  moves only in a vertical direction.  
         [0130]    [0130]FIG. 20 shows a tension spring  307  which biases wire clamp jaws  207 R,  207 L to a closed, clamping position.  
         [0131]    [0131]FIG. 18 illustrates resilient upward motion of bonding tool tip  67  in response to a downwardly directed bonding force exerted by the bonding toot tip on a workpiece, in which a compression spring  309  is compressed. FIG. 14A shows spring  309  in an uncompressed state. FIGS. 14A and 18 also illustrate the separation of upper and lower electrical contact buttons  310  and  311  in response to contact of tool tip  67  with a workpiece, to thereby initiate application of a pulse of electrical energy of predetermined magnitude to ultrasonic transducer  54 .