Patent Abstract:
Methods and systems are described for enabling the efficient fabrication of wedge-bonding of integrated circuit systems and electronic systems.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of and claims priority to U.S. application Ser. No. 12/851,981, entitled “Wire Bonding Method and Device Enabling High-Speed Wedge Bonding of Wire Bonds” filed on Aug. 6, 2010, which is hereby incorporated by reference for all purposes. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to semiconductor device packaging and interconnection technologies. In particular wedge bonding technologies are discussed. More particularly, apparatus, methods, software, hardware, and systems are described for achieving high-speed wedge bonding of wire bonds. 
     BACKGROUND OF THE INVENTION 
     In the field of semiconductor packaging, wire bonding can be used to interconnect integrated circuits and other associated components together. In particular, two main modes of wire bonding are in common usage. Ball bonding and wedge bonding. Both methods are well known in the art and have been in use for many years. As is known, ball bonding is commonly known and is frequently used with gold materials. However gold is relatively expensive. Additionally, such gold ball bonding requires surface plating (for example using silver) and heat to maintain good adhesion to bond pad materials. Additionally, attempts have been made to use ball bonding with copper materials. However, at the high temperatures required for copper ball formation oxide formation is a common problem. The problem is quite pronounced as copper oxides are insulating materials that have proven difficult to bond. Additionally, deformation of the electrical connections made at high temperatures lead to reliability issues. Methods of avoiding oxide formation require the use of oxygen free ambient conditions. This comes with its own set of problems. Similar oxide formation issues make aluminum a difficult material for ball bonding applications as well. An advantage to ball bonding is its high rate of processing speed. In many applications, average bonding speeds of the order of 12-14 bonds per second can be attained. 
     However, because some materials are difficult to work with using high temperature ball bonding, an alternative wedge bonding approach can be used. A disadvantage of such prior art wedge bonding technique is that it is a comparatively slow process with average bonding speeds of the order of 2-3 bonds per second being common. 
     Moreover, although ball bonding and wedge bonding have been used in the industry for many years, wedge bonding has up until this point been a relatively slow process even after 30 years of use. Accordingly, ways of improving wedge bonding speeds would be advantageous. Thus, while existing systems and methods work well for many applications, there is an increasing demand for wedge bonding methodologies that enable increased speed using a variety of materials including aluminum. This disclosure addresses some of those needs. 
     SUMMARY OF THE INVENTION 
     In a first aspect, an embodiment of the invention describes method for high-speed wired bonding. The method involves positioning a distal end of a wire-bonding capillary near a first bonding site. Extruding a length of bonding wire from an aperture in the end of the capillary. Imposing a movable deflector against the extruded length of bonding wire to bend the bonding wire to form a bent portion at an end of the bonding wire. Moving the bent portion of the bonding wire into contact with first bonding site. Wedge bonding the bent portion of the bonding wire with the first bonding site. In one approach, the wedge bonding can comprise, compressing and/or ultra-sonic bonding the bent portion of the bonding wire between the bonding site and a facing surface of the capillary and ultrasonically bonding the bent portion of the bonding wire to the first bonding site. To further continue an example method, the capillary can be moved away from the first bonding site toward a second bonding site where another end of the bonding wire is wedge bonded to the second bonding site to establish a wire bond connection between the first and second bonding sites. 
     In another aspect, embodiments of the invention include a wire bonding apparatus comprising a support for holding wire bonding substrates, a wire bonding capillary with an aperture for carrying and extruding bond wire and enabling bond wire attachment to wire bonding substrates, a movable deflector element arranged to enable movement of the deflector element to bend an extruded length of bonding wire such that the bent extruded length of bonding wire can be articulated at different bond line angles while maintaining a constant rotational orientation for the capillary, and a controller configured to enable control the operation of the wire bonding apparatus. 
     In another aspect, embodiments of the invention describe a movable deflector element module for use in wire bonding operations. One such module includes a deflection member configured to enable movement in an x axis and y axis direction. The member includes an aperture oriented in a z-axis with the aperture having inner wall that defines a wire contact surface having a plurality of wire guide features. Also, a deflection actuator is configured to move the deflection member in said x and y axis directions as directed by a control element configured to specify x and y axis movement for the deflection actuator. 
     In another aspect, embodiments of the invention describe a capillary element for use in high speed wire bonding operations. One such capillary comprises a capillary including a facing surface at a tip end of the capillary. Also including an aperture that penetrates through the capillary to an opening in the facing surface of the shaft to enable a bond wire to pass through the aperture exiting the opening in the facing surface. The facing surface defines a substantially ring-shaped roughened surface area with a substantially flat surface angled in a range of about 0° to about 4°. 
     General aspects of the invention include, but are not limited to methods, systems, apparatus, and computer program products for enabling improved high speed wedge bonding of wire bonds. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention and the advantages thereof may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which: 
         FIGS. 1(   a ) and  1 ( b ) are views of a prior art wedge bonding bond head as shown in side and top section view. 
         FIG. 1(   c ) is a top down diagrammatic view of a prior art bonding tool showing the changing rotational orientation of the wedge bonding tool as it progresses around a die forming a series of wire bonds. 
         FIG. 2  is a block diagram illustrating an example wedge bonding apparatus in accordance with the principles of the present invention. 
         FIG. 3(   a ) is a block diagram illustrating an operational relationship between an inventive deflector element and associated actuator element in a deflector module in accordance with the principles of the present invention. 
         FIG. 3(   b ) is illustration of a specific embodiment of a deflector module in accordance with the principles of the present invention. 
         FIGS. 3(   c )- 3 ( e ) are a set of illustrations depicting a method embodiment of using selected embodiments of a deflector module to position and deflect a wire bond wire in accordance with the principles of the present invention. 
         FIGS. 4(   a )- 4 ( g ) are a set of illustrations illustrating one example process embodiment of using a wedge bonding tool in accordance with the principles of the present invention in conjunction with a deflector element to form directional wire bonds used for connecting IC elements with external connectors such a lead frames. 
         FIG. 4(   h ) shows an example of a bond angle and an alignment approach for one embodiment of wedge bonding in accordance with the principles of the invention. 
         FIGS. 5(   a ) and  5 ( b ) show an example embodiment of deflector element and aperture in accord with one example embodiment of the invention. 
         FIG. 6  is a flow diagram illustrating one approach to implementing wedge bonding in accordance with the principles of the invention. 
         FIGS. 7(   a )- 7 ( d ) illustrate some aspects of one embodiment of a wedge bonding capillary suitable for employment in accordance with the principles of the invention. 
     
    
    
     In the drawings, like reference numerals are sometimes used to designate like structural elements. It should also be appreciated that the depictions in the figures are diagrammatic and not to scale. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Reference is made to particular embodiments of the invention. Examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with particular embodiments, it will be understood that it is not intended to limit the invention to the described embodiments. To contrary, the disclosure is intended to extend to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
     Aspects of the invention pertain to methods and apparatus for enabling high speed wedge bonding in semiconductor wire bonding applications. 
     The diagrammatic illustrations of  FIGS. 1(   a )- 1 ( c ) provide an understanding of some of the problems inherent in state of the art wedge bonding technologies.  FIG. 1(   a ) is a diagrammatic side view of a portion of a wedge bonding tool  100 . A bond head  101  feeds a bonding wire  102  downward and can use a guide  103  to help position the wire  102  in desired proximity to a bond pad  104 . When the bond head  101  is moved in a direction toward the bond pad  104  and downward pressure is applied against the bond pad  104  and the wire  102  and typically ultrasonic energy is applied to the wire  102  to bond the wire  102  to the pad  104 . The tool  100  lifts the bond head  101  and moves it to an associated lead (or other bonding site) that is to be connected with the bond pad  104  by a wire bond. The wire is then typically broken off to complete the wire bond between the two bonding pads. 
       FIGS. 1(   a ) and  1 ( b ) illustrate a facing surface  101   f  of the bond head  101 .  FIG. 1(   b ) is a top down section view of the bond head  101  of  FIG. 1(   a ). The wire  102  runs under the bond head  101 . In particular, this view shows that during wedge bonding the head move  105  in a direction toward the eventual other end of the wire bond connection (i.e., the other bonding surface). Thus, the motion of the wire and head is essentially a straight line motion between the first bonding site and the target bonding site. 
     As shown in  FIG. 1(   c ), it is this straight line motion between beginning bond pad bonding site and target bond location that defines a “bond line” between the two locations.  FIG. 1(   c ) presents a simplified top down view of an integrated circuit die  110  and bond connections to external contacts. As shown here the die  110  includes a plurality of bond pads  111  arranged around a top surface of the die  110 . Also shown are a few of the many electrical connectors ( 112 - 114 ) arranged around the circumference of the die  110 . 
     In examining a first wire bond connection  122  connecting one of the pads  111  with a first external connector  112  the wire bond  122  defines a bond line between the two contact locations. Here we arbitrarily identify the bond line  122  as having angle of 0°. The diagrammatic illustration includes a first bubble  131  that shows a top down view of the associated bond head  101  and the bond wire  102 . During wedge bonding, the bond head is moved in direction  141  from the bond pad  111  toward the final bonding site at connector  112 . In the wedge bonding process, this process is repeated for each pair of pads and contact for the die  110 . Thus, the bonding proceeds around the circumference of the die until completed. 
     For example, as the process has moved clockwise around the die another wire bond  123  is briefly discussed. A second external bond site  113  is wire bonded with an associated one of the pads  111  thereby defining the wire bond  123  and its associated bond line. With reference to the first bond line ( 122 ) it is shown that the bond angle has changed. Here that angle change  135  is represented as 90°. Thus the bond line  123  lies at 90° from the first bond line  122 . This has consequences in how the wire bond is formed. The diagrammatic illustration includes a second bubble  132  that shows a top down view of the associated of the same bond head  101  and a bond wire  102 . Because the bond line is significantly changed, the rotational orientation of the bond head  101  must also significantly rotate. This rotation enables wedge bonding between the external bond site  113  and its associated bond pad. During wedge bonding, the bond head  101  is moved in second direction  142  from the bond pad  111  toward the final bonding site at connector  113 . 
     Likewise, as the process continues moving clockwise around the die another wire bond  124  is briefly discussed. Here, an example third external bond site  114  is shown wire bonded with an associated one of the pads  111  thereby defining the wire bond  124  and its associated bond line. With reference the to the first bond line ( 122 ), it is shown here that the bond angle  136  has further to about 120°. Thus the bond line  124  lies at 90° from the first bond line  122 . Again, this has consequences in how the wire bond is formed. The diagrammatic illustration includes a third bubble  133  that shows a top down view of the associated of the same bond head  101  and a bond wire  102 . Because the bond line is again significantly changed, the rotational orientation of the bond head  101  must also significantly rotate. At this point the rotation is about 120 degrees. Also, as before, this rotation enables wedge bonding between the external bond site  114  and its associated bond pad. During wedge bonding, the bond head  101  is moved in third direction  143  from the bond pad  111  toward the final bonding site at connector  114 . And so it continues until the die  110  is completely bonded. 
     It is very important to consider that the bond head  101  realignment process takes a considerable amount of time. In fact, it is what accounts for the majority of the disparity in bond rates between the ball bonding process (e.g., about 14 bonds/s) and the prior art wedge bonding process (e.g., about 2-3 bonds/s). Accordingly, an approach for removing this step from the process has considerable advantage in a wedge bonding process. 
     Accordingly,  FIG. 2  is a block diagram describing a novel wedge bonding apparatus  200  in accordance with one embodiment of the invention. Several of the many listed components are optional or can be substituted for other elements. The apparatus includes a wedge bonding module  210  arranged to enable wedge bonding of an IC chip  202  to another substrate during a wedge bonding process. The wedge bonding module includes a control arm  211 , an associated wire bonding capillary  213 , and a deflector module  220  arranged to enable deflection of a portion of supplied by a capillary  213  as needed. The wedge bonding device  200  typically includes a control module  230  configured to run software and change operating conditions and parameters prior to and during use. The apparatus can also include a viewing station  204  that enables viewing and can be used to assist in adjusting, and positioning of bonding module  210 . 
     The wedge bonding module  210  typically includes a control arm  211  that can include an ultrasonic head (not shown in this view) with a capillary  213  used as a bonding tool mounted on a distal end thereon. The module  210  can include a linear motor (not shown) that drives the capillary  213  and bonding arm  211  (as can optionally move the deflector module  220 ) in the vertical direction, that is, in the Z-direction. The linear motor is but one of many examples of a suitable motive device that can be used to accomplish the desired movement in the module  210 . This Z-axis movement enables the bond tool  213  to apply wire to various locations on the substrate  202 . An XY table  214  is used as an XY positioning unit that holds the bonding module  210  (including control arm  211 , bonding capillary  213 , deflector module  220 , and image pickup unit  204 ) and moves the module two-dimensionally a substantially horizontally arranged X-direction and Y-direction, and positions the same capillary  213  for wire bonding. 
     The control module  230  can include one or more microprocessors for controlling the entire wire bonding apparatus  210 . For example, a drive device  231  can provide control signals to the bonding head  213  and the XY table  214  in response to a command signal from a controller  232 . Commonly, software (or firmware) is executed on a microprocessor of the controller  232  and the operation of wire bonding or the like is performed by implementing the program. A support  205  holds the IC device  202  so that it can be wire bonded to another substrate. In this depicted embodiment, the other substrate comprises a lead frame  203 . Additionally, in some embodiments, the support can include a heater unit. In one implementation, the semiconductor chip  202  is mounted on a lead frame  203  which can be mounted on the heater plate of a heater unit at the top of the support  205 . The lead frame  203  can be heated by the heater unit. 
     Also, the wire bonding apparatus  200  typically includes an operation panel  233  having, for example, data input features that can include, but are not limited to track balls, alphanumeric value entering keys, and operating switches for enabling input and output of data such as process parameters and further display of the data for operation of the device  200 . Such data can be input into the controller  232  to, for example using a track ball, enable manual movement of the XY table  214 . The control unit  232  and the operation panel  233  are collectively referred to as an operating unit, hereinafter. The wire bonding apparatus  200  can be operated manually or automatically by the operation of the operating unit. 
     The wedge bonding module  210  which drives the bonding arm  211  vertically in the Z-direction includes a position detection sensor  216  for detecting the position of the bonding arm  211 , and the position detection sensor  216  is adapted to output the position of the capillary  213  mounted to the distal end of the bonding arm  211  from the position of a preset original point of the bonding arm  211  to the control device  232 . The linear motor of the wedge bonding module  210  drives the bonding arm vertically in response to instructions from the controller  232  which also controls the magnitude and the duration of a load to be applied to the capillary  211  at the time of bonding. 
     Additionally, an ultrasonic oscillator (not shown) can be located within the arm  211  which, in one embodiment, can use a piezoelectric transducer to cause the capillary  213  to generate the requisite ultrasonic oscillations that can be applied to the capillary  213 , for example, upon reception of a control signal from the controller  232 . 
     Additionally, the controller  232  provides signals to the deflector module  220  that enable it to deflect wire extruded from the capillary  213  in accord with certain aspects of the invention. This will be discussed in greater detail in the following paragraphs. 
     In general, the wire bonding apparatus  200  is configured to connect bond pads of the IC device  202  to external bonding sites, for example, bonding sites on a lead frame  203 . These bond connections are made using bond wire such as aluminum wire. Also, gold and copper can be used in accord with this invention. Aluminum being attractive because it is a softer material than both copper and gold thus reducing stress on the underlying substrate (the die  202 ) during wedge bonding. The approach disclosed in this application has several advantages over prior art methods. Unlike ball bonding, the present invention can be practiced at room temperature thus removing a large array of heat related problems from the system. Additionally, the need for non-oxygen ambient is also removed from the system. Also, it provides a high-speed method for achieving wedge bonding which has been a slow process for over 30 years. Thus, this invention meets a long unmet need and is particularly advantageous when used with materials like aluminum bonding wires. 
     A novel feature of the invention includes a deflector element  220  which is position in an operational arrangement with a bonding capillary  213 . Typically, but not exclusively, the deflector element  220  is mounted with the bonding arm  211 . The deflector element  220  comprises a movable deflector member and an associated actuator that enables controlled motion for the movable deflector member. The motion of the movable deflector member is intended to execute x-axis and y-axis movement and bending of an extruded portion of a bond wire extending from a capillary  213 . 
     In general, the deflector element  220  and capillary  213  are controlled by software and hardware enabling their integrated operation with the wire bonding recipe of the bonding processes executed by the apparatus  200 . 
     Such a movable deflector member can comprise one or more separate elements configured alone or in combination to enable such x, y movement and bending in a bond wire. The actuator can comprise a drive motor(s), magnetic actuators, and other motive elements.  FIG. 3(   a ) is a block diagram schematically illustrating an embodiment of a deflector element  220 . In particular there is a movable deflector member  301  and an associated actuator system  302 . 
       FIG. 3(   b ) is a diagrammatic depiction schematically illustrating an embodiment of a deflector element  220 . In particular there is a movable deflector member  311  and an associated actuator system  312 . In this particular embodiment, the member  311  includes an aperture  313  used to manipulate the position of the bond wire. In such case the bond wire is deflected by the inner surfaces of the aperture  313 . For example, the aperture  313  is made in a working end of a deflector wand  311  that includes an arm portion  311   a  used to engage the working end with the actuator  312 . The actuator system can comprise any system of motive devices suitable for moving the deflector member (or wand)  311  in the desired directions. 
       FIGS. 3(   c ) &amp;  3 ( d ) are diagrammatic depictions of the deflector member  311  embodiment such as shown in  FIG. 3(   b ). The aperture  313  has a diameter that is greater than a diameter of an associated capillary  213 . One example of a set of ranges for capillary outer diameter is on the order of about 2-100 mils. Such ranges are very flexible and depend largely on the size of the bonding wires and bonding pads (or other contacts) used. A complementary aperture  313  has a larger aperture. In one embodiment, the aperture can range from about 10-25% larger than the capillary diameter. For example, an aperture diameter for a 10 mil diameter capillary is on the order of about 11-13 mils. In one example, a capillary has an outer diameter of about 30 mils, with an associated deflector inner diameter of about 40 mils. Referring back to  FIG. 3(   b ), in one example the thickness of the deflector  311  can be on the order of about 4-30 mils. It should be specifically pointed out that although specific dimensions are identified, a considerably larger range of dimensions, shapes, and configurations are expressly contemplated by this patent. Additionally, such deflector members can be made using a number of different materials or combinations of materials. In one example, the deflector member  311  can be made of a tungsten material. 
       FIG. 3(   d ) is a bottom up view of an example embodiment. The aperture  313  of the deflector member  311  includes an inner surface  313   d  that can operatively deflect the bond wire  314 . Also, the cross-section  315  of  FIG. 3(   d ) is used to describe the process illustrated in  FIG. 4 . 
       FIG. 3(   e ) is a simplified view (as in  FIG. 3(   d )) of an example embodiment showing deflection of a wire  314 . The deflector member  311  moves in an arbitrary direction  316 , shown here as having an x-component and a y-component. Importantly, the wire  314  is deflected by a surface of the inner wall of the aperture  313   d . Thus, the wire  314  is bent and orient in a desired direction. Importantly, the orientation of the capillary  213  does not change (in an x, y direction) to accommodate changing angles of the bent bond wire. The capillary  213  maintains the same orientation regardless of bond angle (or wire angle) in the bent bonding wire. 
     It is particularly pointed out that the deflection of the wire  314  is achieved by the relative motion of the wire with respect to the deflector  311 . In other words, it can be that the capillary  213  itself is moved relative to a stationary deflector  311 . 
       FIGS. 4(   a )- 4 ( g ) illustrate an implementation of a process used to establish a high speed wedge bond. 
       FIG. 4(   a ) shows a capillary  213  in position above a bond pad  401  preparatory to bonding a wire  314  to the pad. This view is similar to the cross-section axis  315  shown in  FIG. 3(   d ). In this embodiment, a deflector member  311  is in position to deflect an extruded portion  314   e  of a bonding wire  314  extending from a capillary. 
     In one feature of the invention, the facing surface of the capillary  317  is a substantially flat surface. The surface  317  generally having a face angle of in the range of about 0-4°. This is important because it is desirable to have the greatest amount of surface area of the facing surface applied against a bend bonding wire. 
     In describing the process, the capillary  213  is positioned above the desired bonding site  401 , a portion of wire  314   e  is extruded from the wire in a desired length. For example, the length  314   e  is on the order of a radius of a flat facing surface  317  of the capillary. For example, using an 8 mil diameter capillary, the extruded portion  314   e  can be on the order of about 3-4 mils in length. The bonding wire can be made of any material and any thickness. Gold, copper, aluminum, and allots of the same provide some examples of suitable materials. Such wires are on the order of 15 μm-to 2 mil as well as other thicknesses. In one example, a capillary  213  extrudes a portion of a bond wire  314   e  a desired length through the aperture  313  and then fixed in length. For example, the wire can be extruded through an open wire clamp to the desired length, then the wire clamp fixes the wire in place (stabilizing the length) and then relative movement of the deflector and capillary bend the wire as appropriate. 
     The bond angle required to connect the bond pad  401  to a desired external bonding site is determined. This enables the correct x, y deflection to be applied to the bent portion of the wire  403 . Then, as shown in  FIG. 4(   b ), the deflector  311  is moved in direction  402  that bends the extruded wire portion  314   e  in the desired direction to form a bent wire portion  403  oriented in a desired direction. 
     After bending, as shown in  FIG. 4(   c ), the deflector  311  is moved back  404  into a centered position (centered on the capillary  213 ). 
     Then, as shown in  FIG. 4(   d ), the capillary  213  is stamped downward  405  into the bonding site  401  such that the bent wire  403  is compressed (See,  FIG. 4(   e )) between the facing surface  317  of the capillary  213  and the surface of the bond pad  401 . One advantage of using aluminum wire is that aluminum is softer than gold and copper. Relative to gold, this means that the downward force applied to an aluminum wire and bond pad  401  is less than half the pressure applied to a similar diameter gold wire. This places a good deal less stress on the underlying semiconductor device. This lack of stress is particularly advantageous in that it substantially reduces stress induced damage in the underlying devices. 
     Thus, as is shown in  FIG. 4(   e ) the stamping process compresses the bent portion of bond wire. Additionally, to establish a solid bond ultrasonic energy is applied to the wire to ultrasonically bond  314   b  the wire to the bond pad  401 . 
     Once bonded, as shown in  FIG. 4(   f ), the wire  314  is lifted away from the wedge bond  314   b  and moved to the complementary bonding site (e.g., on an associated lead frame). Once, the capillary is moved to the complementary bonding site a second wedge bond is made and then the wire  314  is broken off. The capillary  213  is retracted back upward through the deflector aperture  313  (See,  FIG. 4(   g )). The capillary is also moved to a next bond pad and a new length of wire  314   e  is extruded for bonding to the second bond pad. The illustrated process is repeated again and again until a desired number of wire bonds are made with the die substrate. 
     Additionally, when the wire portion  403  ( 314   e ) is bent in direction  402  (See, e.g.,  FIG. 4(   b )) the direction of deflector  311  movement  402  is generally aligned to facilitate a direct connection between the subject bond site (bond pad  401 ) and the desired target bond site (e.g., the lead frame attachment point). For example, with reference to  FIG. 4(   h ) a bond pad  111  is positioned in an example arrangement with an associated connector  115  (e.g., a portion of a lead frame) onto which a second bond site is located and a second wire bond is to be made. A bond wire  116  is bent in an appropriate direction (as shown) generally aligned with a direct line to the second bond site  115 . The bond angle  117  can change for each wire bond connection between first site (e.g.,  111 ) and second associated bond site (e.g.,  115 ) as a wire bonding process is executed around an integrated circuit die. The methods and devices described herein are flexible and robust enabling a 360° change in bond angles. Advantageously, the disclosed embodiments do not require any change in rotational bond head configuration as the process proceeds around the circumference of the die. This allows the process to continue with no rotational adjustment of the bond head (the capillary) as it moves from wire bond to wire bond to wire bond. This eliminates the constant readjustments required of prior art wedge bonding tools as they move from wire bond to wire bond. Thus, it is far faster than these tools, having bond rate similar to that of ball bonding tools and processes. This has been a major jump forward solving a 30 year old problem and will likely find broad wedge bonding application across the entire semiconductor industry. 
     It is pointed out that the wire can be positioned and held in place using standard clamp and wire tensioners as can be found in ball bonding tools. The clamp holds the wire in place while the deflector bends the wire into the desired configuration and then releases the wire once it is positioned at the desired bonding site. Moreover, in some embodiments the wire tensioner (or other associated vacuum systems) can be dispensed with altogether. 
       FIG. 5(   a ) shows another embodiment of a deflector aperture. In this depiction, a deflector arm  511   a  supports a working end  512  of a deflector element  511 . In particular, a different embodiment of aperture is shown. The aperture  513  comprises a flower-shaped aperture  513  arranged with a plurality of wire guiding features  514 . The inner surface of the aperture  513  is shaped generally like a “flower” having petal portions. These petal portions  514  are the guide features  514 . They are arranged such that when the aperture is moved across ( 402 ) the extruded wire (e.g.,  314   e ) the wire can be generally centered at a nadir  515  of one of the features  514 . Importantly, the presence of apexes  516  between the petals can prevent the wire from deviating from one petal to another as the deflector moves across the capillary. As shown in this embodiment, the aperture  513  includes 8 “petals” that serve as the guide features  514 . Different embodiments can, of course, have more or fewer petals. Also, a wide range of petal shapes or configurations can be employed as might be suggested to one of ordinary skill by this disclosure. 
     An example depiction of the operation of a guide feature  514  is shown with reference to  FIG. 5(   b ) which shows a portion of an aperture of one possible embodiment of a deflector element  511 . As shown here each of the petals  514  has a curvature defining a nadir  515  portion located at the sidewall of the aperture  513  for each petal  514 . Moreover, separations between petals  514  are defined at each petal end by an apex feature  516 . In one example bending operation, as the deflection aperture  513  begins to deflect an extruded length of wire  314   e , the wire  314   e  may attempt to move or bend in an undesirable direction. To assist in keeping the wire  314   e  on track, the shape of the guide feature  514  guides the wire  314   e  into a more desirable location to achieve bending at a desired angle. In one embodiment, each petal  514  can have a curvature with outer nadir  515  and a series of apex features  516  separating the petals  514 . Thus, during bending the wire  314   e  is caught with one of the guide features  514  (for example at a starting position  540  wherein during the bending operation the wire  314   e  slides (e.g., in direction  541 ) to a desired position  542 . In particular, the apexes  516  can serve as restraining members ( 516 ) between the petals  514  prevent free motion of the wire  314   e  from petal to petal, thereby working to restrain the radial motion of the wire  314   e  as it is bent. This assists the deflector element  511  in correctly aligning the bent wire during use. 
     It is specifically pointed out that many different implementations of such guide features can be used. For example, the inner surface of the aperture can comprise a set of slots or grooves in the inner surface to engage and fix the wire during wire bonding. In one example implementation a series of notches can be arranged in a spaced apart arrangement around the inner surface of the aperture. For example, the spacing can be such that grooves are spaced every 5°, 4°, 3°, 2°, 1°, or even tighter. It is pointed out that these intervals are examples only and that the invention is not limited to these intervals with those of ordinary skill appreciating that the spacing can be set at any desired interval. It is also pointed out, that alignment features can also be arranged on the capillaries. However, the inventors note that it is advantageous to place them on the deflector element. This is because the formation of the guide features is time consuming and difficult. Additionally, the lifespan of an average capillary is considerably less than that of a deflector. Thus, although the invention contemplates the placement of alignment features on the capillaries and/or the deflector element  511 , there are certain advantages to placing them on the longer lived deflector element. 
     In a continuing description of the invention one method of applying this technology is described. In one embodiment, a method of employing a wire bonding apparatus  200  in accordance with an aspect of the invention is described. This embodiment describes a wedge bonding method and associated method of establishing wire bonds between bond sites. An aspect of this invention will be discussed in association with the embodiment addressed in the flow diagram of  FIG. 6 . 
     Once the die (or other target subject) is positioned on the inventive wedge bonding tool bonding can begin. It is to be noted that appropriate adjustments and software instructions can be applied to the tool  200 . 
     Accordingly, the distal end of a wire-bonding capillary is positioned near a first bonding site (Step  601 ). The capillary supports a bonding wire and can have an entire strand of appropriate wire in readiness for a bonding process. The wire can be of any material, with aluminum, copper, and even gold providing attractive materials. Aluminum in particular provides some process advantages. In particular, aluminum is soft and also aluminum is compatible with many bond pad and bonding site materials (e.g., copper). Accordingly, it is not necessary to plate the target bond pads to obtain good bond adhesion between wire and pad as is the case with some other materials (e.g., gold). Generally, such positioning involved positioning the capillary right above the bond site. The capillary head must be positioned above the bond pad a distance that is thicker (e.g.,  316 ) than the thickness (height) of the associated deflector arm (e.g.,  311 ). Thus, for a deflector arm 30 mils thick, the capillary head will be at least 35 mil and possibly much higher above the bond pad. In one example implementation the capillary head (the tip of the capillary) is positioned about 50 mils above the target surface (the bond site) in readiness for bonding. In general, the capillary head is a distance above the bond pad that takes into consideration the height of the deflector above the bond pad, the thickness of the deflector, the thickness of the wire, and any desired tolerances. 
     A length of wire is extruded from the aperture in the end of the capillary (Step  603 ). In one implementation, a bond wire is fed down through an inner diameter of the capillary to extend a distance beyond a facing surface of the capillary. The extruded length can be on the order of about the radius of the capillary face. Thus, for a capillary having a diameter of about 6 mils, an extruded length of up to 3-4 mils can be used. It is pointed out that greater or shorter extruded lengths can be used. In particular, for greater diameter capillaries greater lengths can be used and vice versa. As mentioned above, aluminum, copper, gold and other materials can be used with aluminum being a particularly attractive candidate. Additionally, a wide range of wire thicknesses can be employed with this methodology. One example range of wire thicknesses can include wire diameters ranging from about 5 μm to about 2 mils and other thicknesses. One example can be a 50 μm aluminum wire extruded to a length of about 3 mils using a capillary having a diameter of about 6 mils. Of course this is but one example with many others apparent to those of ordinary skill. 
     Once the desired length of wire is extruded, a movable deflector is imposed against the extruded length of bonding wire to bend the bonding wire to form a bent portion at an end of the bonding wire (Step  605 ). A deflector (for example, a deflector  311  as is shown in  FIGS. 4(   a )- 4 ( g )) is brushed under the extruded portion of wire (for example, the wire  314   e  of  FIGS. 4(   a )- 4 ( g )) bending the wire against the bottom face of the capillary (for example, capillary  213  of  FIGS. 4(   a )- 4 ( g )) to form the bent portion of the wire (for example, bent wire  403  of  FIGS. 4(   a )- 4 ( g )). Importantly, as already discussed, the deflector bends the wire to attain the desired orientation (bond angle) relative to the associated second bond site to which the wire is to be connected in the wire bonding process. 
     Additionally, the bending process requires that the deflector pass beneath the capillary. For example, in one embodiment the facing surface of the capillary can lie a distance of about 1.1 to about 1.5 wire diameters above the top surface of the deflector  311 . Of course, the distance can be less or greater. The general idea being that the desired amount of bend is imparted to the bent portion of wire  403  by the motion of the deflector under the capillary. 
     Once bent, the deflector is repositioned such that the capillary can pass through the aperture of the deflector. Then the capillary is moved through the aperture toward the bonding site such that the bent portion of the bonding wire is moved into contact with the first bonding site (Step  607 ). Additionally, the facing surface of the capillary compresses the bent portion of the bonding wire between the bonding site and a facing surface of the capillary to establish a wedge bond of the bonding wire with the first bonding site (Step  609 ). This process is typically enhanced using ultrasonic energy. For example ultrasonic bonding or scrubbing can enhance the bond between the wire and bonding surface. Also, in some embodiments thermosonic bonding can be used enhance the bond between the wire and bonding surface. This will be discussed in some detail below with respect to certain capillary heads. This process results in a low temperature wedge bond that can be established in any direction without need for changing the rotational orientation of the capillary. This first novel aspect of this embodiment is completed in the formation of this novel type of wedge bond. 
     Once the bond is established, the method can move the bonding wire to a second bonding site to establish a completed wire bond electrical connection with another circuit element. For example, the capillary is moved away from the first bonding site (the location of the first bond) toward a second bonding site (where the bond that completes the connection can be made) (Step  611 ). Once in the desired location the capillary is positioned operative arrangement with the second bonding site and the wire is wedge bonded to the second bonding site to establish a wire bond connection between the first and second bonding sites (Step  613 ). A standard wedge bonding technique can be used here and the wire can be broken off in a standard fashion to complete the bond. At this point the capillary can be removed to another bonding site to repeat the process. Importantly, the rotational orientation of the capillary is not changed in this move. 
       FIG. 7(   a ) is a cross-section view of one example of a capillary device  213  suitable for use with some embodiments described in this specification. The capillary  213  can be made of any material. But when used with aluminum wire, a hard material like aluminum oxide crystals (ruby, sapphire, etc.) can provide an excellent capillary material. In aluminum applications such materials are harder than aluminum oxide materials that sometimes form on bond wires. Such oxides are damaging to prior art ceramic capillaries. And such ruby materials also suffer from less aluminum build up. Additionally, similar advantages can be obtained with tungsten carbide capillary materials. It is pointed out that this technology has applicability beyond aluminum wedge bonding and can be used with copper, gold, silvers, their alloys as well as various other materials. In addition to the materials described above, in some implementations capillaries formed of ceramics (e.g., Zirconar ceramic and others) can also be used. 
     In one important attribute, the face surface  701  of the capillary is flat or very near flat. The face angle  702  (not drawn to scale) that describes an angle that the facing surface  701  makes with a perfectly flat plane should be less than about 4-5°. This very flat surface enables a maximum contact area of the surface  701  with the bent wire. Additional implementations can include faces with slight inverse angles (those having surfaces that become higher as they extend inward from the face edges). In general, these more flat surfaces are very different from capillaries used to ball bond gold wires. Such ball bonding capillaries are designed to optimize ball formation. Accordingly, they have relatively steep face angles. In a typical gold ball bonding application the face angle will be 8°, 12°, 15°, or even steeper. These tools cannot provide the needed contact area required to enable the present methodology. Additionally, when using gold processes, the facing surface  701  is very smooth. However, in an aluminum bonding capillary, a great deal of “scrubbing” is required to break up the surface oxides present on aluminum wires. Hence a rough surface is required. This is amplified through the effect of ultrasonic scrubbing. Such a roughened matte surface can be used with a ruby or tungsten carbide capillary. 
     It is also noted that a pattern of raised features can be used to good effect in this manner. For example a criss-crossed (cross-hatched) pattern of raised features (e.g., a waffle-shaped pattern) can provide good results.  FIG. 7(   b ) is a side-section view of a facing surface  701  having a number of raised features  703 . Such a pattern is particularly useful when used with tungsten carbide capillaries. For example, in the embodiment shown, the pattern of features  703  can comprise a series of ridges that are spaced and sized at dimensions that are dependent on the diameter of wire used. For example, the ridges can be spaced a distance about 10-25% of the wire diameter, on center, and can have a height of about 10-25% of the wire diameter, width a ridge width of on the order of about 4-15% of the wire diameter. For example, when applied to a 1 mil wire, example features can include ridges spaced apart by about 0.20 mils, with a height of about 0.20 mils, and being about 0.05 mils wide. It will be readily appreciated that smaller feature dimensions as well as larger can be used. 
     In another embodiment,  FIGS. 7(   c ) and  7 ( d ) depict a facing surface (e.g.,  701 ) of another capillary  713  facing surface  701 . The facing surface  701  includes a series of guide features formed in the facing surface  701 . As shown here, the guide features comprise positioning grooves  711  arranged in the facing surface  701 . The grooves  711  are configured to aid in the position of bonding wires as the wired will slide into the grooves during bonding making the wire positioning more secure and precise. In the depicted embodiment, the grooves  711  are arranged like spokes around a centralized aperture  714  through which the extruded wire is supplied for wire bonding. Depending on the needs of the user more (or less) spokes can be employed. 
     Referring to side section view of  FIG. 7(   d ), the seating grooves can be configured having shallow or deep depths. Preferred embodiments are arranged with the depth of seating grooves  711  being in the range of about 25-405 of the thickness of the wire used. In one example, a 15 μm wire can have a groove  711  depth of on the order of about 5 μm. The idea being that a wire will slide into the groove, during bonding, and prevented from further substantial radial movement once lodged in the groove  711 . As for the remaining portions of the surface, they can be smooth or roughened depending on the needs of the user. 
     Returning to a discussion of  FIG. 7(   a ), the outer edges  704  of the capillary are also different from known geometries. This difference is intended to provide a larger surface area for contacting the wire. Thus, a radius of curvature for the outer edge  704  of the capillary is much less than that used for a gold ball bonder. For example, in the present invention, the radius of curvature for the outer edge  704  is on the order of 12 μm or less. This, radius is very small as compared with the 20 μm or greater radii commonly found in gold ball bonding capillaries. 
     Additionally, the chamfer angle in the present capillary is steeper than that of an ordinary ball bond capillary. This can be characterized by the interior chamfer angle (ICA) depicted in  FIG. 7(   a ) as ICA  704 . In a suitable embodiment used for the wedge bonding applications described here, angles in the range of about 0° to about 120° can be suitable. With angles of 70° of less being preferred in some implementations. This enables a tighter chamfer and thereby increases the surface area of the facing surface  701 . In this application, a chamfer diameter  705  is about 1.5 times the diameter of the bond wire used. Additionally, the bore diameter  706  is sized to be in the range of about 6-10 μm more than the diameter of the bond wire used. However, in some implementations the outer chamfer diameter  705  may be arranged only slightly larger or of the same diameter as that of the bore  706 . Another feature is a bore length  707  that defines a length of the bore shaft that is vertical walled to enable the wire to remain straight as the deflector bends the wire. In one implementation this is one the order of about 1-2× the bond wire diameter. It is pointed out that this is just one example implementation and is not the only way such a capillary can be formed. In one embodiment, it is important that the facing surface be flat (or nearly so), that the facing surface have a roughened or patterned surface rather than a smooth face, and that the facing surface be generally round (a typical facing surface being shown for  213  in  FIG. 3) . 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the invention. Thus, the foregoing descriptions of specific embodiments of the present invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings. 
     The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.

Technology Classification (CPC): 7