Abstract:
A method for making a bonding tool is provided. The bonding tool includes a three dimensional surface configuration which is a mirror image of a three dimensional surface configuration of a circuit card assembly (CCA). The method includes creating a mirror image of the three dimensional surface configuration of the CCA. After producing the three dimensional surface configuration of the CCA, the method then produces a bonding tool surface with the mirror image of the three dimensional surface configuration. The mirror image of the three dimensional surface configuration isolates delicate components of the CCA during bonding and re-bonding operations of the CCA using the bonding tool.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to bonding tools for bonding boards of circuit card assemblies and more specifically to a method for manufacturing a bonding tool.  
           [0003]    2. Description of Related Art  
           [0004]    Many electronics used today include electronic control assemblies (ECAs) formed using circuit card assemblies (CCAs) having printed circuit boards (PCBs). The CCAs used for the ECAs include various components necessary for the functionality of the CCA and an electronic device using the CCA. These components include resistors, capacitors, inductors, RF components, output pins, and the like having delicate leads which facilitate connectivity and functionality of the components.  
           [0005]    During formation of the ECA, the CCA is bonded with a substrate, such as a heat sink, in order to provide a backbone to the structure and provide heat dissipating capabilities for the CCA. During production of ECAs, manufacturing defects may occur which may render the ECA non-functional for the intended use of the ECA. These defects include contamination and scratching of the substrate and/or CCA during bonding, and bubble formation within the CCA.  
           [0006]    To correct the defects caused during production, a user removes the CCA from the substrate and repairs the defect. Typically, the user removes the CCA from the substrate using well known processes, such as use of a wire in a guillotine manner which allows for removal of the CCA from the substrate. Upon removal of the CCA, the manufacturing defects are repaired and the CCA re-bonded to the substrate. In order to properly re-bond the CCA with the substrate, the CCA along with the substrate and bonding material are subjected to high pressure in order to facilitate re-bonding. However, the high pressure and the vacuum environment often times damages the components of the CCA, thereby necessitating replacement of the components. More specifically, the high pressure damages the delicate leads on the components, thereby rendering the component non-functional. The components with damaged leads can not be repaired, thereby additional components are required increasing overall costs. Likewise, costs associated with re-bonding are further increased due to the labor required to reinstall the components with standard manual soldering methods.  
           [0007]    To avoid the aforementioned problems and crushing components of the CCA during re-bonding of the CCA, the components were removed. Nonetheless, if the CCAs requiring re-bonding employed the previously described leads and other delicate components, the delicate components were not easily removable. To further illustrate, the leads typically have very little structural rigidity and used the CCA for structural support. As such, upon removal of the components from the CCA, the leads would curl into itself thereby negating re-soldering to the CCA. As a result, the CCA required replacement components in order to successfully re-bond the CCA to the substrate.  
         BRIEF SUMMARY OF THE INVENTION  
         [0008]    The present invention is directed towards providing a bonding tool for bonding a circuit card assembly (CCA) and a method for making the bonding tool. A configuration of the bonding tool complements a configuration of the CCA such that the bonding tool isolates delicate components of the CCA from pressure during a bonding or re-bonding operation.  
           [0009]    In one exemplary embodiment of the present invention, a method for producing a bonding tool for bonding a board of a CCA is disclosed. The CCA can include a three dimensional surface configuration defined by various components of the surface of the CCA, such as resistors, inductors and the like. An exemplary method comprises creating a mirror image of the three dimensional surface configuration of the board. After creation of the mirror image, a bonding tool surface with the mirror image of the three dimensional surface configuration is created. The mirror image of the bonding tool surface complements the surface of the CCA, such that during bonding and re-bonding operations, the bonding tool isolates components of the CCA from pressure.  
           [0010]    In another exemplary embodiment of the present invention, a bonding tool is disclosed. In this embodiment, the bonding tool bonds a CCA having a three dimensional surface configuration to a substrate during manufacturing of the CCA. In addition, the bonding tool can be used to re-bond a CCA during repair of a CCA. The bonding tool is a metal structure having a bonding tool surface. The bonding tool surface includes a three dimensional surface configuration which complements the CCA. As such, during bonding or re-bonding of the CCA to a substrate or heat sink with the bonding tool, the bonding tool minimizes the possibility of damaging components on the CCA.  
           [0011]    As may be appreciated, exemplary embodiments provide a bonding tool which can minimize the possibility of damaging components located on a CCA during bonding and re-bonding operations. The configuration of the bonding tool can also minimize the time associated with re-bonding a CCA since a user does not remove components during the re-bonding operation , thereby saving the costs associated with having a user individually remove components from the CCA. The configuration of the bonding tool can also minimize material cost replacement components which have been damaged or do not have structural integrity to withstand removal and replacement. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    Many advantages of the present invention will be apparent to those skilled in the art with a reading of this specification in conjunction with the attached drawings, wherein like reference numerals are applied to like elements and wherein:  
         [0013]    [0013]FIG. 1 illustrates a circuit card assembly (CCA) having a board with components in accordance with an embodiment of the present invention.  
         [0014]    [0014]FIG. 2 illustrates a perspective view of a bonding tool in accordance with an exemplary embodiment of the present invention.  
         [0015]    [0015]FIG. 3 illustrates a schematic view of an exemplary embodiment of the present invention demonstrating the placement of a bonding tool onto a CCA.  
         [0016]    [0016]FIG. 4 is a flowchart showing an exemplary method for forming a bonding tool in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]    The present invention relates to a bonding tool and a method for forming a bonding tool. FIG. 1 is a perspective view illustrating a bonding tool  101  having a metal structure  100  in accordance with an embodiment of the present invention. The bonding tool  101  includes a bonding tool surface  110  having a three dimensional surface configuration which mirrors a three dimensional surface configuration of a circuit card assembly (CCA)  103 . The bonding tool  101  includes recesses  104 ′ through  108 ′ which mirror components on a board  102  of the CCA  103 . The configuration of the recesses  104 ′ through  108 ′ allows fitment of components  104  through  108  of the CCA  103  within the recesses  104 ′ through  108 ′ during use of the bonding tool  101 .  
         [0018]    The recesses  104 ′ through  108 ′ include dimensions which are a mirror image of the dimensions of the components  104  through  108  thereby providing the bonding tool  101  with a mirror image of the three dimensional surface configuration of the CCA  103 . The recess  104 ′ includes dimensions H 4′ , W 4′ , and L 4 ., the recess  106 ′ includes dimensions H 6′ , W 6′ , and L 6′ , and the recess  108 ′ includes dimensions H 8′ , W 8′ , and L 8′ . The dimensions of the recess  104 ′ correspond to the dimensions of the component  104 . The dimension H 4′ , corresponds to dimension H 4  of the component  104  while dimension W 4′ , corresponds to the dimension W 4  of the component  104  and dimension L 4′ , corresponds to dimension L 4  of the component  104 . Therefore, the recess  104 ′ forms a mirror image of the component  104 . However, the dimensions H 4′ , L 4′ , and W 4′ , of the recess  104 ′ are slightly larger than the dimensions H 4 , L 4  and W 4  of the component  104 . The slightly larger dimensions of the recess  104 ′ allow placement of the component  104  within the recess  104 ′ during bonding operations using the bonding tool  101  such that the bonding tool  101  does not contact the component  104 .  
         [0019]    Likewise, the dimensions of the recess  106 ′ correspond to dimensions of the component  106 . The dimension H 6′  corresponds to dimension H 6  of the component  106  and the dimension W 6′ , corresponds to dimension W 6  of the component  106  while the dimension L 6 , corresponds to dimension L 6  of the component  106 . In addition, the dimensions H 8′ , W 8′ , and L 8′ , of the recess  108 ′ correspond to dimensions H 8 , W 8  and L 8  of the component  108 . The dimensions correspond such that the components  106  and  108  fit within the recesses  106 ′ and  108 ′ during application of the bonding tool  101  upon the CCA  103 . As discussed with reference to the recess  104 ′ and the component  104 , the dimensions H 6′ , L 6′ , W 6′ , H 8′ , L 8′ , and W 8′ , of the recesses  106 ′ and  108 ′ are slightly larger than the dimensions H 6 , L 6 , W 6 , H 8 , L 8  and W 8  of the components  106  and  108 . Therefore, upon placement of the bonding tool  101  onto the CCA  103 , the components  106  and  108  fit within the recesses  106 ′ and  108 ′. It should be noted that while the CCA  103  and the bonding tool  101  have been described to include the components  104  through  108  and the recesses  104 ′ through  108 ′, the CCA  103  may include any number of components having any type of configuration (e.g., a mix of resistors, capacitors, inductors, power supplies, etc.) to form a three dimensional surface configuration. In accordance with an embodiment of the present invention, the bonding tool  101  will be a mirror image of the CCA  103  irrespective of the amount and the configuration of the components on the CCA  103 . Thus, the bonding tool  101  will have any number of recesses corresponding to the three dimensional surface configuration of the CCA  103 . In addition to the recesses  104 ′ through  108 ′, the bonding tool  101  also includes a protrusion  210  as shown with reference to FIG. 2.  
         [0020]    [0020]FIG. 2 illustrates a perspective view of a bonding tool in accordance with an embodiment of the present invention. The protrusion  210  corresponds to a surface  302   a  of a CCA  303  (shown with respect to FIG. 3). As such, upon application of the bonding tool  201  to the CCA  303 , the protrusion  210  is adjacent the surface  302   a.  Therefore, during a bonding operation using the bonding tool  201  and the CCA  303 , the high pressures imparted by the bonding tool  201  transmit to the CCA  303  via the protrusions  210  and the surface  302   a.  Thus, recesses  204 ′ through  208 ′ of the bonding tool  201  isolate components  304  through  308  of the CCA  303  from high pressures imparted by the bonding tool  201 . The bonding tool  201  bonds the CCA  303  to a substrate such as a heat sink. In an embodiment of the present invention, the bonding tool  201  can be constructed of any material capable of withstanding high vacuum and pressure, such as metal or the like. It should be understood that the surface  302   a  of the CCA  303  is not limited to the configuration shown with respect to FIG. 3. Consequently, the protrusions  210  shown and described with reference to FIG. 2 are not limited to that particular configuration. As previously mentioned, the CCA  303  may have numerous configurations. Thus, the bonding tool  201  will have protrusions  210  which correspond to the numerous configurations of the surface  302   a  of the CCA  303 .  
         [0021]    The bonding tool  201  can be used for a variety of bonding operations, including bonding a substrate to a heat sink or the like. During the bonding operation, the recesses  204 ′ through  208 ′ allow bonding to the substrate under both pressure and vacuum while minimizing the possibility of damaging the components  304  through  308  of the CCA  303 . Moreover, the protrusions  210  provide a contact surface between the bonding tool  201  and the CCA  303  such that the bonding tool may impart bonding forces to the CCA  303  during a bonding operation. It should be noted that the bonding tool  201  includes a plurality of protrusions (not shown) which contact a plurality of surfaces (not shown) of the CCA  303 . Accordingly, the bonding tool  201  translates forces during bonding operations to the CCA  303  via the plurality of protrusions on the bonding tool  201  and the plurality of surfaces on the CCA  303 . As may be appreciated, the bonding tool  201  protects the components located on the CCA  302 , such as the component  304 , via recesses, such as the recess  304 ′, during bonding operations.  
         [0022]    [0022]FIG. 3 illustrates the CCA  303  having a board  302  and components  304  through  308 . In accordance with an embodiment of the present invention, the components  304  through  308  can be any components which provide functionality for the CCA  303 . These components include but are not limited to, electrical and/or mechanical inductors, resistors, capacitors, power sources, and other components. In addition, the components  304  through  308  can include leads  304   a  through  308   a  which provide connectivity and functionality for the components  304  through  308 . The components  304  through  308  protrude from a surface  302   a  of the board  302  thereby forming a three dimensional surface configuration for the CCA  303 . It should be noted that the previously described recesses isolate the leads  304   a  through  308   a  during application of a bonding tool made in accordance with the present invention to the CCA  303 .  
         [0023]    The components  304  through  308  include the dimensions H 4  through H 8 , W 4  through W 8  and L 4  through L 8 . The dimensions H 4  through H 8  correspond to a protrusion height of the components  304  through  308  from the surface  302   a  of the board  302 . The dimensions W 4  through W 8  correspond to a width of the components  304  through  308 . It is to be understood that the dimensions H 4  through H 8 , W 4  through W 8  and L 4  through L 8  can be formed to any dimension. The dimensions L 4  through L 8  correspond to a length of the components  304  through  308 . The CCA  303  can include any number of components having a variety of dimensions. A user can generate a schematic and topographical layout of the CCA  303  using an electronic tool capable of generating an electronic layout, such as Pro/ENGINEER® (CAD/CAM) software available from Parametric Technology Corporation located in Needham, MA or CATIA-CADAM® software available from Dassault Systems located in Woodland Hills, CA or the like. As a user generates the CCA  303 , the various dimensions for the CCA  303  can be stored within a database created by the electronic tool. Using the electronic tool, a user forms a mirror image of the CCA  303  using the various dimensions stored in the database created by the electronic tool.  
         [0024]    [0024]FIG. 4 illustrates a method  400  for making a bonding tool. In an exemplary operation  402 , a user determines a three dimensional surface configuration of a CCA board. The three dimensional surface configuration includes various components on a surface of the CCA board, such as resistors, capacitors, inductors, power supplies or the like. During this operation, the user determines what areas of the CCA may be subjected to pressure (e.g., bare areas of the CCA) and the location of components that are not capable of resisting bonding pressure forces. In an embodiment of the present invention, a user makes this determination using an electronic layout of the board with the previous described software. The electronic layout of the board includes various dimensions of the components, including, height, width and length of the components.  
         [0025]    For example, Pro/ENGINEER® can be used to generate an electronic layout of the CCA  303  used to fabricate the CCA  303  shown with respect to FIG. 3. The electronic layout includes the various dimensions of the components  304  through  308  and the surface  302   a.  In the operation  402 , a user accesses a Pro/ENGINEER® database having data corresponding to the various dimensions of the components  304  through  308  and the surface  302   a  of the CCA  303 . Using the Pro/ENGINEER® database, the user determines the three dimensional surface configuration of the CCA  303 .  
         [0026]    Once the user determines the three dimensional surface configuration of the CCA  303 , an operation  404  is performed. In the operation  404 , a user creates a mirror image of the three dimensional surface configuration using the three dimensional surface configuration of the CCA board determined in the operation  402 .  
         [0027]    Turning back to the example, a user creates a mirror image of the CCA  303  using the Pro/ENGINEER® database having the dimensions of the various components of the CCA  303 . The user reads data from the Pro/ENGINEER® database and creates a mirror image of the data in a separate file. If the dimensions L 4 , W 4  and H 4  of the component  304  have values of 0.25 inches, 0.25 inches and 0.125 inches, the user creates a recess having dimensions slightly larger than L 4 , W 4  and H 4  (e.g., 0.26 inches, 0.26 inches and 0.135 inches) in a separate Pro/ENGINEER® database. As such, when the user places a bonding tool formed with these dimensions over the CCA  303 , the bonding tool will not contact the component  304 . It should be noted that during the operation  404 , the user creates recesses for all components of the CCA  303 , such as the components  306  and  308  and any other components. In accordance with an embodiment of the present invention, components are structures which may be damaged during a bonding operation performed on the CCA  303 . For surfaces that will not be damaged (e.g., bare areas of the CCA  303 ), the user does not incorporate recesses into the mirror image of the three dimensional surface configuration of the mirror image.  
         [0028]    Once the user creates the mirror image of the three dimensional surface configuration of the CCA  100 , the user can produce a bonding tool surface with the adjusted mirror image of a three dimensional surface configuration. In accordance with an embodiment of the present invention, the user can form the mirror image bonding tool using any suitable stereo lithography technique. Typically, a stereo lithography assembly (SLA) grows a mirror image bonding tool. In this embodiment, the user sends an electronic version of the Pro/ENGINEER® database file to an SLA machine which grows the bonding tool mirror image. Upon formation of the mirror image bonding tool, an operation  406  is performed.  
         [0029]    In the operation  406 , a user performs a fit check of the formed mirror image. Returning to the example, after formation of the mirror image of the three dimensional surface configuration of the board using a SLA machine, the user fit checks the model against the board. In this example, the user performs the fit check at an electrostatic discharge (ESD) workstation. The user places the formed mirror image over the CCA  303  to ensure that the components  304  through  308  do not touch the formed mirror image. Once the user completes the fit check during the operation  406  and determines proper fitment over the CCA  100 , an operation  408  is performed.  
         [0030]    During the operation  408 , the bonding tool is produced using dimensions of the mirror image of the three dimensional surface configuration of the board created in the operation  404 . The bonding tool can be formed using any suitable technique or fabrication device capable of forming tools of a material which withstands high vacuum and pressure, such as metal. The tools which may be used to form the bonding tool include a milling machine, a computer numerically controlled (CNC) machine, or the like. A user transfers data for the bonding tool to the fabrication device using any suitable method such as electronic transfer of an electronic file to the fabrication machine. It should be noted that in accordance with alternative embodiments of the present invention, data can be transferred using any suitable technique, including hard data (e.g., printed layouts, etc.), to a user of a machine where the machine is capable of fabricating the bonding tool.  
         [0031]    After the various dimensions of the bonding tool are transferred, the CNC machine fabricates the bonding tool according to the dimensions. Upon fabrication of the bonding tool, the bonding tool is deburred and any sharp edges of the tool are broken. Deburring and removal of sharp edges removes slivers and metallic fleck created during production of the bonding tool. As such, deburring and removal of slivers minimizes the possibility of injuring the user during handling of the bonding tool, puncture of the bonding vacuum pressure system, and damaging the CCA (e.g., slivers, flecks, etc. coming into contact with CCA). Once all sharp edges are broken and the tool is deburred, a coating is applied on a side of the bonding tool which contacts the CCA. The coating provides a cushion between the bonding tool and the CCA to protect the CCA from friction which may occur during bonding or re-bonding operations.  
         [0032]    Turning back to the example and FIG. 2, the dimensions used to form the readjusted mirror image of the CCA  303  of FIG. 3 are used to produce the bonding tool  201  shown with reference to FIG. 2 in the operation  408 . As previously described, the user formed the mirror image of the CCA  303  using Pro/ENGINEER®. As such, the user transfers an electronic file having the Pro/ENGINEER® database to a CNC machine which fabricates the bonding tool  201  shown with respect to FIG. 2. Once the CNC machine completes fabrication of the bonding tool  201  and the bonding tool  201  is deburred, all sharp edges are broken, and coating applied, the bonding tool  200  can be used for bonding operations.  
         [0033]    Exemplary embodiments of the present invention can reduce overall time and costs associated with manufacturing CCAs due to necessity of hand installation of delicate components after bonding. Exemplary embodiments of the present invention can reduce time required to repair manufacturing defects. Exemplary embodiments can be used to obviate the need for removal of individual components of a CCA by a user prior to re-bonding since the bonding tool can be fit over individual components. Exemplary embodiments can reduce the possibility of introducing workmanship defects which may be caused during reattachment of the individual components to the CCA.  
         [0034]    An exemplary tool of the present invention can apply high pressure in a vacuum environment to a CCA having delicate components. Likewise, a bonding tool made in accordance with an exemplary embodiment of the present invention can reduce the possibility of damaging delicate components of the CCA, thereby obviating the need for removal of components from the CCA during initial bonding or re-bonding of the CCA with a substrate. A bonding tool made in accordance with the present invention can be configured for any number of configurations of CCAs.  
         [0035]    The above are exemplary modes of carrying out the invention and are not intended to be limiting. It will be apparent to those of ordinary skill in the art that modifications thereto can be made without departure from the spirit and scope of the invention as set forth in the accompanying claims.