Abstract:
A tool for attaching fine preformed probes to a substrate for use with a vacuum source is disclosed. The apparatus comprises a body portion; a tip portion disposed at one end of the body portion; a first orifice extending from a first end of the body portion to the working tip; and at least one second orifice extending from an outer portion of the working tip and communicating with the first orifice, wherein the vacuum source is coupled to the body portion so that a vacuum generated by the vacuum source is provided to the at least one second orifice.

Description:
This application claims priority on provisional application Ser. No. 60/568,036, filed on May 4, 2004. 

   FIELD OF THE INVENTION 
   The present invention relates to fine wire bonding on a substrate. More particularly, the present invention is related to bonding a preformed probe to a substrate to facilitate testing of the substrate. 
   BACKGROUND OF THE INVENTION 
   Traditionally, fine wires of gold and aluminum are employed in wire bonding to make electrical interconnections between two or more electrodes on semiconductor devices. The most common wire interconnection made on a semiconductor is made between the conductive pad on a semiconductor chip and a conductive terminal which is adjacent the chip and which serves as an output lead to the connector pins of the package in which the semiconductor chip is contained. One well-known device commonly used to make such connections is a wedge bonding tool. In wedge bonding an end of a fine wire supplied from a spool of wire is fed through a hole in the bonding tool. The end of the wire is then pressed against the bonding pad and scrubbed at a high frequency to create the bond by the transfer of molecules between the pad and the wire. The fine wire is then severed by tearing or breaking the fine wire at the second bond. 
   In instances where testing of integrated circuit chips is required, it is desirable to connect test leads or probes to select points on the chip&#39;s testcard substrate. As mentioned above, conventional wedge bonding tools connect a length of wire to a bond pad, but then must be cut or otherwise severed from the supply wire spool. This has several drawbacks including possible break of the bond at the testcard substrate, inconsistent wire lengths and increased time to complete the many connections necessary to adequately populate the chip with probes. 
   Accordingly, there is a need to provide an apparatus and method for attaching precut or singulated preformed probes to devices to facilitate testing. 
   SUMMARY OF THE INVENTION 
   In view of the deficiencies in the prior art, the present invention is a tool for attaching fine preformed probes to a substrate for use with a vacuum source. The apparatus comprises a body portion with a tip portion disposed at one end of the body portion. A first orifice extends from a first end of the body portion to the working tip, and at least one second orifice extends from an outer portion of the working tip and communicates with the first orifice. The vacuum source is coupled to the body portion so that a vacuum generated by the vacuum source is provided to the at least one second orifice. 
   According to another embodiment of the present invention, the tip portion has a profile that substantially matches a profile of the probes. 
   According to still another embodiment of the present invention, the vacuum is communicated to the at least one second orifice to secure a probe to the tip portion. 
   According to yet another embodiment of the present invention, the at least one second orifice is a plurality of second orifices, with a first portion of the plurality of second orifices disposed along a first portion of the tip portion and a second portion of the plurality of second orifices disposed along a second portion of the tip portion. 
   According to a further embodiment of the present invention, the tip portion comprises a first wedge portion formed at a first face of the tip portion and a second wedge portion projecting from a second face of the tip portion. 
   According to still a further embodiment of the present invention, the is first face is disposed on an opposite side of the tip portion from the second face of the tip portion. 
   According to yet a further embodiment of the present invention, the tip portion further comprises a slot disposed within a face of the second wedge portion, such that the second orifices communicate with the slot. 
   According to another embodiment of the present invention, the first orifice extends from the top through the bottom of the tool, and a lower portion of the orifice is sealed to permit fluid tight communication with the at least one second orifice. 
   According to still a further embodiment of the present invention, a working tip is disposed at a lower portion of the tip portion. 
   According to yet another embodiment of the present invention, the at least one second orifice extends through the working tip, and an end portion of the at least one second orifice is sealed to provide fluid tight communication with the first orifice. 
   According to still another embodiment of the present invention, the tip portion comprises a plurality of facets. A first facet being formed at a first angle relative to the longitudinal axis of the body portion, two second facets being formed adjacent opposite sides of the first facet and having at an overall angle relative to the longitudinal axis of the body portion, and a third facet adjacent each of the two second facets and formed at an angle relative to the longitudinal axis of the body portion. 
   According to a further embodiment of the present invention, the bonding tool comprises a plurality of facets, i) a first facet formed at a first angle relative to the longitudinal axis of the body portion, and ii) two second facets adjacent opposite sides of the first facet and formed at an overall angle relative to the longitudinal axis, a first projection adjacent each of the two second facets and extending a predetermined distance from the tip portion; and a slot disposed along a length of the first projection, the at least one second orifice terminating at the slot. 
   An exemplary method for attaching a preformed probe to a substrate according to the present invention comprises the steps of: providing a vacuum to the bonding tool; communicating at least a portion of the vacuum to an exterior surface of the bonding tool; coupling the preformed probe to a portion of the exterior surface of the bonding tool based on the vacuum; bonding a portion of the probe to the substrate; removing the vacuum from the bonding tool; and releasing the probe from the bonding tool. 
   These and other aspects of the invention will become apparent from the detailed description and accompanying drawing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is best understood from the following detailed description when read in connection with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawings are the following Figures: 
       FIGS. 1A-1H  are various illustrations of a first exemplary embodiment of the present invention; 
       FIGS. 2A-2G  are various illustrations of a second exemplary embodiment of the present invention; 
       FIGS. 3A-3B  are perspective views of a tip of a bonding tool according to another exemplary embodiment of the present invention; and 
       FIGS. 4A-4C  are views illustrating a bonding probe captured by a bonding tool according to the present invention prior to bonding. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to  FIGS. 1A-1G  a first exemplary embodiment of the present invention is illustrated. As shown in  FIG. 1A , wedge bonding tool  100  comprises a body portion  102  and a tip portion  106  having an overall length L between about 0.437 and 2.5 inches. In one desirable non-limiting embodiment overall length L is about 0.86 inches. Wedge bonding tool  100  may be formed from any suitable material, such as Titanium Carbide or Tungsten Carbide, for example. Wedge bonding tool  100  is used to attach fine wires, such as singulated probe leads (not shown in this figure), to a substrate such as a semiconductor device (not shown). The aforementioned probe leads may be supplied from a magazine (not shown) with the bonding tool and magazine being moved toward one another to provide the probe leads to the bonding tool. The bonding tool and magazine are subsequently separated from one another and the probe is moved into position for bonding. 
     FIG. 1B  illustrates a side view of bonding tool  100 . As shown in  FIG. 1B , body portion  102  may include planar area  104  disposed at a lower portion of body portion  102  and above tip portion  106 . In the embodiment as illustrated, planar portion  104  continues into tip portion  106 . As can be seen, tip portion  106  is multifaceted and comprises a rear face  110  having a predetermined angle Sa relative to the longitudinal axis of the tool. Angle Sa is referred to herein as the “Tool Throat Angle” and, in one non-limiting exemplary embodiment, is between about 10 and 30 degrees. In one desirable non-limiting embodiment angle Sa is about 10 degrees. To facilitate positioning in the bonding machine (not shown) a locating flat LF may be provided. In general LF may be between 0.046 and 0.11 inches. In one non-limiting embodiment LF is about 0.059 inches. As illustrated in  FIG. 1B , in one exemplary embodiment locating flat LF extends from the top of bonding tool  100  to planar area  104 . 
     FIG. 1C  illustrates a front view of bonding tool  100 . As shown in  FIG. 1C , bonding tool  100  has an outside diameter OD of between about 0.0625 and 0.125 inches and planar portion  104  having an overall length Rh (also referred to as the “release height”) of between about 0.1 and 2.0 inches. When viewed from the front of tool  100 , tip portion  106  has a V shape forming an overall angle Wa (Wedge Angle) of between about 10 and 50 degrees. In one non-limiting exemplary embodiment body portion  102  has an outside diameter OD of about 0.0625 inches, Rh is about 0.25 inches and Wa is about 30 degrees. As shown in  FIG. 1H , the combination of locating flat LF and outside diameter OD may result in bonding tool  100  having a non-uniform cross section. 
   Referring now to  FIGS. 1D ,  1 F and  1 G a detailed perspective view, a detailed side view and a detailed front view, respectively, of tip portion  106  are illustrated. As shown in  FIG. 1D , tip portion  106  comprises side faces  112  and  114 , rear face  110  and front face  117 . Each of these faces is set at an angle with respect to the longitudinal axis of bonding tool  100 . Rear face  110  has an angle Sa of between about 10 and 30 degrees, side faces  112  and  114  form an overall angle Wa of between about 10 and 50 degrees, and front face  117  has an angle a of between about 10 and 55 degrees. This latter angle a is termed by the inventors as “the foot clearance” and chosen to avoid interference with adjacent probes. In one non-limiting exemplary embodiment, Sa is about 10 degrees, Wa is about 30 degrees, and α is about 34 degrees. 
   Orifice  108  having a diameter VH of between about 0.003 and 0.04 inches extends from the top of body portion  102  into tip portion  106 . In one desirable embodiment, VH is about 0.007 inches. For ease of manufacture it may be desirable to allow orifice  108  to extend through the bottom of tip  106 . A plug  119  or other means to seal the bottom of tip  106  may then be inserted into the lower portion of orifice  108 . Protrusion  116 , having a width EPw between about 0.003 and 0.02 inches, extends from front face  117  and comprises orifices  122 , having diameter H between about 0.001 and 0.02 inches, extending inwardly from the outside of protrusion  116 . It is also desirable to have more that one orifice  122  spaced apart from one another with a pitch P between about 0.0015 and 0.025 inches. By having multiple orifices  122 , vacuum can be provided at various positions along the length of the singulated probe lead ensuring adequate retention to tip portion  106 . In one desirable non-limiting embodiment, EPw is about 0.005 inches, H is about 0.0025 inches, and/or P is about 0.0025 inches. 
   Orifices  122  intersect and are in fluid tight communication with orifice  108 . In one non-limiting embodiment, orifices  122  intersect orifice  108  at about a right angle. In one non-limiting exemplary embodiment, the lower edge of protrusion  116  is set at a desired angle a (also referred to by the inventors as “foot clearance”), between about 10 and 55 degrees in order to avoid interference with adjacent probes. In one embodiment, foot clearance a is about 34 degrees. The contour of protrusion  116  is desirably similar to the shape of at least a portion of the probe (as shown in  FIGS. 4A-4B  for example) to be bonded to the substrate. A slot   120  having a width BSw, termed by the inventors as “Bottom Slot Width,” below the vicinity of orifices  122 , of between about 0.0015 and 0.015 inches, a width VSw in the vicinity of the orifices  122 , termed by the inventors as “Vacuum Slot Width,” of between about 0.0015 and 0.015 inches, and a depth Sd, between about 0.0005 and 0.01 inches, may also be disposed along some or all of the face of protrusion  116  to accommodate a portion of a singulated lead probe (not shown in this figure); thus, aiding in positive positioning of the singulated probe adjacent orifices  122  and working face  121 . In one non-limiting exemplary embodiment, VSw is about 0.0035 inches, BSw is about 0.0035 inches, and/or Sd is about 0.0015 inches. Further, slot  120  has a dimension VSH as measured from the bottom of tip portion  106  to the top of slot  122 , termed by the inventors as the “Vacuum Slot Height,” of between about 0.01 and 0.15 inches. In one non-limiting embodiment, VSH is about 0.058 inches. It should be noted that the cross section of slot  120  (best shown in  FIG. 2E  as slot   220 ) may comprise a substantially flat bottom or a somewhat curved bottom depending on the type of tool used to form slot  120 . 
   The inventors have determined that it is desirable to use vacuum as a means for extracting individual singulated probes from the magazine (not shown) and to hold the probe in place as the probe is moved into place and bonded to the substrate (not shown). As can be appreciated from the above description and drawings, a vacuum applied to orifice  108  will be presented at the openings of orifices  122  and may be used to capture and retain the singulated lead probe for bonding. 
   At the bottom of tip  106  working face  121  is provided. Working face  121  comprises a width W between about 0.003 and 0.02 inches and a foot size F between about 0.004 and 0.02 inches. Distance BI, as measured from the bottom of slot  120  to the edge of working face  121 , is between about 0.002 and 0.01 inches and determines the bond length of the singulated probe. In a non-limiting embodiment, width W is about 0.005 inches, foot size F is about 0.005 inches and distance BI is about 0.003 inches. 
     FIG. 1E  is an exploded side view of working tip  106  illustrating the position G, of approximately ⅓ of bond length BL, and width GW, between about 0.0005 and 0.003 inches, of groove  123  disposed on the bottom of tip  121 . In one non-limiting embodiment, G is about 0.0013 inches and GW is about 0.0005 inches. 
   A second exemplary embodiment of the present invention is illustrated in  FIGS. 2A-2G . As shown in  FIGS. 2A-2G , wedge bonding tool  200  is similar to bonding tool  100  with respect to its general features. The significant difference is in the contour and implementation of tip portion  206 .  FIG. 2A  illustrates a front view of bonding tool  200 ,  FIG. 2B  illustrates a side view of Bonding tool  200  and  FIG. 2C  illustrates a bottom view of bonding tool  200 . 
     FIGS. 2D and 2G  illustrate detailed side views and cross sectional views of tip portion  206 , respectively. As shown in  FIGS. 2D and 2G , rear face  210  is set at an angle Sa of between about 10 and 30 degrees (desirably about 10 degrees) relative to the longitudinal axis of bonding tool  200 . Similar to the first exemplary embodiment, orifice  208  extends from the top of bonding tool  200  to the vicinity of orifices  222  and  223 , which in turn extend inwardly from the outside edge of protrusion  216 . As mentioned above with respect to the first exemplary embodiment, although orifice  208  is shown as extending through the bottom of bonding tool  208 , although not required to implement the present invention, this may be done for ease of manufacturing, and that in practice a plug or other type of seal is provided to ensure fluid tight communication of a vacuum from orifice  208  into orifices  222  and  223 . 
   A first set of orifices  222  are disposed at the upper portion of protrusion  222  and a second set of orifices  223 . Similar to the first exemplary embodiment, slot  220  may be provided in the vicinity of orifices  222  and/or  223  as desired to provide for positive alignment of the singulated probe with the orifice. As can be appreciated, the addition of orifices  223  provides greater means for retaining the singulated probe to bonding tool  200 . As can also be appreciated, still additional orifices may be included at other points along the contour of protrusion  216  as desired where the probe is expected to contact protrusion  216 , such as along portion   224 . Placing orifices along portions of protrusion  216  where the probe will not contact the protrusion will result in reduced holding power along the portions where the probe does contact the protrusion. In order to provide maximum coverage to desired portions of protrusion  216  it may be necessary to set orifices  222  and/or  223  at an angle relative to the normal of orifice  208 . This can be seen in  FIGS. 2D and 2G  where orifices  223  are angled upward. Further, although orifices  222  could be oriented downward, because such a downward angle would undoubtedly cross into orifices  223  and possibly create occlusions due to the small size of the openings, it is desirable to avoid situations where the orifices  222  and  223  would cross into one another. In order to conform the profile of tip portion  206  to a substantial portion of the singulated probe, angle α for the upper portion of slot  220  may be different from the generalized angle  244  of the lower portion of slot  220 . 
   Working tip  226  is disposed at the bottom of tip portion  206 . As illustrated, working tip  226  comprises a first angled portion  228  and a second angled portion  230  adjacent angled portion  228 . In one non-limiting embodiment, angled portion  228  has an angle  240  of about 5 degrees and second angled portion  230  has an angle  242  of about 15 degrees. 
     FIG. 2E  illustrates a detailed plan view of the bottom of tip portion  206 . As shown in  FIG. 2E , groove  232  having a width GW and a depth GD is formed in the bottom face of tip  206  and offset from the bottom of slot  220  by distance G. In one non-limiting embodiment, G is about 0.007 inches, GW is about 0.005 inches, GD is about 0.003 inches and/or the depth of slot  220  is about 0.002 inches at an upper portion and about 0.0015 inches along its interface with orifices  222  and/or  223 . 
     FIGS. 3A and 3B  are perspective views of the tip portion of yet another exemplary embodiment of the present invention. As shown in  FIG. 3A , tip portion  306  comprises facets  310 ,  312 ,  314  and  316 , working tip  326  as well as slot  320  and orifices  322 . In this exemplary embodiment, rather than having protrusion along which a singulated probe will be coupled by vacuum, the singulated probe will be disposed within slot  320  and coupled thereto by the vacuum. The dimensions of slot  320  are desirably based on the profile of the singulated probe to be bonded. As is understood by those skilled in the art, a portion of the singulated probe will wrap under working tip  326  in order to facilitate bonding to the device (not shown). In one exemplary embodiment, working tip  326  includes a groove  332  similar to that discussed above with respect to the aforementioned embodiments. In all other respects this embodiment is similar to the first and second exemplary embodiments. 
   Referring now to  FIG. 3B , a rear perspective view of tip portion  306  is illustrated. As shown in  FIG. 3B , for ease of manufacturing, orifices  320  may extend from one side of tip  306  at front face  316  through to rear face  310 . In order to ensure that an adequate amount of vacuum is provided to the side of orifices  320  at slot  320 , a sealant or plug may be used along face  310 . The sealant or plug may be any of several well-know types. 
     FIGS. 4A-4C  illustrate the coupling of a singulated probe to the bonding tool of the present invention. As shown in  FIG. 4A , tip portion  406   a  is provided with a vacuum from a vacuum source (not shown), which vacuum is in turn communicated to orifices  422   a  and  423   a . The vacuum drawn into these orifices is in turn used to maintain singulated probe  401   a  in place against a portion of the contour of tip portion  406   a . As illustrated, singulated probe  401   a  does not specifically match the contour of the entirety of tip portion  406   a , but has sufficient correlation thereto so that the vacuum is able to hold probe  401   a  in place as the probe is moved from the dispensing magazine (not shown) to the bonding site (not shown). As is also shown in  FIG. 4A , a tail portion  403   a  of probe  401   a  is disposed adjacent to working tip   426   a  to facilitate bonding. Also shown is plug  419   a  to ensure that sufficient vacuum flows thorough orifices  422   a  and  423   a . As noted above, plug  419   a  may not be needed if orifice  408   a  does not extent trough the bottom of the bonding tool. 
     FIG. 4B  illustrates another exemplary embodiment in which the bonding tool has a tip portion  406   b  and a profile differing from that of  FIG. 4A  and with orifices  423   b  that intersect orifice  408   b  at an angle. 
   Table 1 is a listing of abbreviations and their associated meanings, as used herein and with reference to the drawing, as well as exemplary non-limiting dimensional ranges and desirable non-limiting dimensions. 
   
     
       
             
             
             
             
           
             
             
             
             
           
         
             
               TABLE 1 
             
             
                 
             
             
               Abbre- 
                 
               Range 
               Dimension 
             
             
               viation 
               Meaning 
               [inches] 
               [inches] 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               L 
               Tool length 
               0.4370-2.5   
               0.8600 
             
             
               P 
               Vacuum hole Pitch 
               0.0015-0.025  
               0.0025 
             
             
               VH 
               Vertical Vacuum Hole Diameter 
               0.003-0.04  
               0.0070 
             
             
               Sd 
               Slot Depth 
               0.0005-0.01  
               0.0015 
             
             
               H 
               Vacuum Hole Diameter 
               0.001-0.02  
               0.0025 
             
             
               VSH 
               Vacuum Slot Height 
               0.01-0.15 
               0.058 
             
             
               BI 
               Bond Length 
               0.002-0.01  
               0.003 
             
             
               F 
               Foot Size 
               0.004-0.02  
               0.005 
             
             
               á° 
               Foot Clearance 
               10°-55° 
               34° 
             
             
               VSw 
               Vacuum Slot Width 
               0.0015-0.015  
               0.0035 
             
             
               EPw 
               External Profile Width 
               0.003-0.02  
               0.005 
             
             
               W 
               Tool Tip Width 
               0.003-0.02  
               0.005 
             
             
               BSw 
               Bottom Slot Width 
               0.0015-0.015  
               0.0035 
             
             
               LF 
               Shank Locating Flat 
               0.046-0.11  
               0.059 
             
             
               OD 
               Shank Out Diameter 
               0.0625-0.125  
               0.0625 
             
             
               Sa° 
               Tool Throat Angle 
               10°-30° 
               10° 
             
             
               G 
               Groove Location 
               ~⅓ BL 
               0.0013 
             
             
               GW 
               Groove Width 
               0.0005-0.003  
               0.0005 
             
             
               Wa° 
               Tool Tip Width Angle 
               10°-50° 
               30° 
             
             
               Rh 
               Release Height 
               0.1-2.0 
               0.25 
             
             
                 
             
           
        
       
     
   
   While preferred embodiments of the invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those skilled in the art without departing from the spirit of the invention. Accordingly, it is intended that the appended claims cover all such variations as fall within the spirit and scope of the invention.