Abstract:
The present invention relates to a wire bonding structure, and more particularly to a manufacturing method for said wire bonding structure. The wire bonding structure comprises a die that connects with a lead via a bonding wire. At least one bond pad is positioned on an active surface of the die, and a gold bump is provided on the bond pad; furthermore, a ball bond can be positioned upon the gold bump. The bond pad and the gold bump can separate the ball bond and the die, which can avoid damaging the die during the bonding process.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of U.S. Provisional Application No. 61/098,292 filed on 19 Sep. 2008 under 35 U.S.C. §119(e), the entire contents of all of which are hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a wire bonding structure, and more particularly to a manufacturing method for said wire bonding structure. 
       BACKGROUND 
       [0003]      FIG. 1  is a diagrammatic illustration of a wire bonding structure in accordance with a prior art. The typical wire bonding structure  10  comprises a substrate  11  and a die  13 . The die  13  comprises an active surface  131  and a back surface  133 , and is positioned on the top surface of the substrate  11 . A bond pad  15  is positioned on the active surface  131  of the die  13 , and connected with a lead  19  by means of a ball bond  171  and a bonding wire  173 . 
         [0004]    In the manufacturing process of wire bonding structure  10 , the die  13  can be positioned on the top surface of the substrate  11  by means of an adhesive layer  12 . For example, the back surface  133  of the die  13  can connect with the top surface of the substrate  11  via the adhesive layer  12 . Thereafter, a capillary  18  can be used to form the ball bond  171  on the bond pad  15 , and then form the bonding wire  173  to connect the ball bond  171  and the lead  19 . 
         [0005]    In general, the ball bond  171  and the bonding wire  173  are both made of copper, so that the cost of the manufacturing process of the bonding structure  10  can be reduced. However, damage to the die  13  or the bond pad  15  may occur during the bonding process. For example, heat can be generated when the ball bond  171  is formed on the bond pad  15 , and in turn damage the die  13  and cause a reduction in the yield of the wire bonding structure  10 . 
       SUMMARY OF THE INVENTION 
       [0006]    It is the primary objective of the present invention to provide a wire bonding structure, wherein a bump is positioned between the bond pad and the ball bond, and the ball bond shall not touch the bond pad or the die to avoid damage to the die and/or the bond pad during the bonding process. 
         [0007]    It is a secondary objective of the present invention to provide a wire bonding structure, wherein the bump is made of gold, and the hardness of said gold is much lower than that of copper, tin, or aluminum, which can maintain the structure and the functionality of the die during the bonding process. 
         [0008]    It is another objective of the present invention to provide a wire bonding structure, wherein the bump is positioned between the bond pad and the ball bond to increase the distance between the ball bond and the bond pad, which can improve the yield of the wire bonding structure. 
         [0009]    It is another objective of the present invention to provide a manufacturing process for the wire bonding structure, wherein a capillary can be used to form the ball bond and the bonding wire, and the efficiency of the bonding process can be improved. 
         [0010]    It is another objective of the present invention to provide a manufacturing process for the wire bonding structure. A gold bump can be formed on the bond pad before bonding the ball bond and the bonding wire, which thus avoids the ball bond directly touching the bond pad. 
         [0011]    In an aspect of the present invention, a wire bonding structure is provided, comprising: a die comprising a first surface and a second surface; a bond pad positioned on said first surface of the die; a bump positioned on the bond pad, wherein the bump comprises gold; a ball bond positioned on the bump; and a bonding wire connecting the ball bond and a lead. 
         [0012]    In an aspect of the present invention, a wire bonding structure is provided, comprising: at least one first bond pad positioned on a first die; at least one second bond pad positioned on a second die; a first bump positioned on the first bond pad; a second bump positioned on the second bond pad, wherein the first bump and the second bump both comprise gold; a ball bond positioned upon the first bump; and a bonding wire connecting the ball bond and the second bump. 
         [0013]    In an aspect of the present invention, a manufacturing method of a wire bonding structure including a bond pad positioned on a die is provided, comprising the steps of: forming a bond pad on a die; forming a bump on the bond pad, wherein the bump comprises gold; forming a ball bond on the bump; and forming a bonding wire to connect the ball bond and a lead. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1  is a diagrammatic illustration of a wire bonding structure in accordance with a prior art. 
           [0015]      FIG. 2  is a diagrammatic illustration of a wire bonding structure in accordance with an embodiment of the invention. 
           [0016]      FIG. 3A  to  FIG. 3C  are diagrammatic illustrations of the manufacturing process of a wire bonding structure in accordance with an embodiment of the invention. 
           [0017]      FIG. 4  is a diagrammatic illustration of a wire bonding structure in accordance with an embodiment of the invention. 
           [0018]      FIG. 5  is a diagrammatic illustration of a wire bonding structure in accordance with an embodiment of the invention. 
           [0019]      FIG. 6  is a diagrammatic illustration of a wire bonding structure in accordance with an embodiment of the invention. 
           [0020]      FIG. 7A  to  FIG. 7D  are diagrammatic illustrations of the manufacturing process of a wire bonding structure in accordance with an embodiment of the invention. 
           [0021]      FIG. 8  is a diagrammatic illustration of a wire bonding structure in accordance with an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Referring to  FIG. 2 , there is shown a diagrammatic illustration of a wire bonding structure in accordance with an embodiment of the invention. The wire bonding structure  20  comprises a die  23  that connects with a first bond pad  29  via a bonding wire  273 . Further, the die  23  comprises a first surface  231  and a second surface  233 , wherein the first surface  231  can be an active surface and the second surface  233  can be a back surface. 
         [0023]    There is at least one bond pad  25  positioned on the first surface  231  of the die  23 , and a bump  26  is positioned on the bond pad  25 , wherein the bump  26  can be made of gold. A ball bond  271  can be positioned upon the bump  26 , and connected with the first bond pad  29  by means of a bonding wire  273 . 
         [0024]    In one embodiment of the invention, the ball bond  271  and the bonding wire  273  can be made of copper, tin, or aluminum, and so on. The hardness of gold is much lower than that of copper, tin, and aluminum, so by using gold damage to the bond pad  25  and/or die  23  can be avoided during the process of forming gold bump  26 . Moreover, the ball bond  271  is formed upon the bump  26  and does not touch the bond pad  25  and/or the die  23 , so that the structure and function of the die  23  and/or the bond pad  25  can be maintained after bonding the ball bond  271  and the bonding wire  273  on the bump  26 . 
         [0025]    Referring to  FIG. 3A  to  FIG. 3C , there are shown diagrammatic illustrations of the manufacturing process of a wire bonding structure in accordance with an embodiment of the invention. There is a bond pad  25  positioned on the first surface  231  of the die  23 , and a bump  26  can be formed on the bond pad  25  by ultrasonic vibration of metal diffusion technology. For example, a capillary  281  can be used to form the bump  26  on the bond pad  25 , wherein the bump  26  is made of gold, as shown in  FIG. 3A . In addition, the bump  26  also can be formed on the bond pad  25  by plating technology. 
         [0026]    A capillary  283  can be used to form a ball bond  271  upon the bump  26 , as shown in  FIG. 3B . For example, a wire  27  is carried through the capillary  283 , and threaded through the capillary  283  for use in the bonding process. The end of the wire  27  protruding from the capillary  283  is heated to a molten state by way of an electrical discharge or a hydrogen torch; the capillary  283  presses the molten wire  27  against the bump  26  to form the ball bond  271  upon the bump  26 . 
         [0027]    The capillary  283  can be used to form a bonding wire  273  to connect the ball bond  271  and the lead  29 , as shown in  FIG. 3C . For example, after forming the ball bond  271  on the bump  26 , the capillary  283  can be moved from the bump  26  to the lead  29 , and the wire  27  is pressed against the lead  29 , thereby forming the bonding wire  273  between the bump  26  and the lead  29 . In addition, the wire  27  can be a copper wire, tin wire, or aluminum wire, and the ball bond  271  and the bonding wire  273  can both be made of copper, tin, or aluminum. 
         [0028]    The die  23 , the bond pad  25 , and the lead  29 , may be heated during the bonding process for the benefit of melting the wire  27 . The capillary  283  may include an ultrasonic vibration unit to form the ball bond  271  and the bonding wire  273 . Furthermore, a capillary with metal diffusion technology may be used to form the ball bond  271  and the bonding wire  273 . 
         [0029]    The bump  26  is made of gold. As the hardness of gold is much lower than that of copper, tin, or aluminum, damage can be avoided to the die  23  and/or the bond pad  25  as the gold bump  26  is formed on the bond pad  25 . Otherwise, the bump  26  formed on the bond pad  25  can act as a buffer structure, so that the ball bond  271  cannot touch the bond pad  25  and/or the die  23  directly during the bonding process, which can protect the die  23  and/or the bond pad  25  from damage resulting from high temperatures. 
         [0030]    In one embodiment of the invention, the die  23  can be positioned on the top surface of a substrate  21 . For example, the second surface  233  of the die  23  can connect with the top surface of the substrate  21  via an adhesive layer  22 , and the lead  29  may be positioned on the same or different substrate  21 . In addition, the substrate  21  can also be a leadframe, and the die  23  and/or the lead  29  can be positioned on the leadframe. 
         [0031]    Referring to  FIG. 4 , there is shown a diagrammatic illustration of a wire bonding structure in accordance with an embodiment of the invention. The wire bonding structure  200  comprises a die  23  and a substrate  21 , and the die  23  may connect with the substrate  21  via an adhesive layer  22 . Further, the die  23  comprises a first surface  231  and a second surface  233 , wherein the first surface  231  can be an active surface and the second surface  233  can be a back surface. 
         [0032]    There are a lead  29  and a bond pad  25  positioned on the substrate  21  and the first surface  231  of the die  23  respectively. A bump  26  that is made of gold can be positioned on the bond pad  25 . Furthermore, a ball bond  271  can be positioned upon the bump  26 , and connected with the lead  29  by means of a bonding wire  273 . 
         [0033]    Referring to  FIG. 5 , there is shown a diagrammatic illustration of a wire bonding structure in accordance with an embodiment of the invention. The wire bonding structure  30  comprises a first die  331  and a second die  333  that connect to each other. There is at least one first bond pad  351  positioned on the first die  331 , and at least one second bond pad  353  positioned on the second die  333 . 
         [0034]    A first bump  361  and a second bump  363  are positioned on the first bond pad  351  and the second bond pad  353  respectively; the first bump  361  and the second bump  363  are both made of gold. A bump  365  is positioned upon the second bump  363 , and a ball bond  371  is positioned upon the first bump  361 , and the ball bond  371  connects with the bump  365  by means of a bonding wire  373 . The ball bond  371  and the bump  365  are both made of copper, tin, or aluminum. 
         [0035]    In another embodiment of the invention, there is no bump  365  positioned upon the second bump  363 , and the ball bond  371  can connect with the second bump  363  by means of a bonding wire  373  directly, as shown in  FIG. 6 . 
         [0036]    Referring to  FIG. 7A  to  FIG. 7D , there are shown diagrammatic illustrations of the manufacturing process of a wire bonding structure in accordance with an embodiment of the invention. The first bond pad  351  and the second bond pad  353  can be positioned on the first die  331  and the second die  333  respectively. Thereafter, a capillary  381  can be used to form the first bump  361  on the first bond pad  351 , and form the second bump  363  on the second bond pad  353 , wherein the first bump  361  and the second bump  363  are both made of gold, as shown in  FIG. 7A . 
         [0037]    After forming the first bump  361  and the second bump  363 , a capillary  383  can be used to form a bump  365  upon the second bump  363 , as shown in  FIG. 7B . Furthermore, the capillary  383  also can be used to form the ball bond  371  upon the first bump  361 , wherein the bump  365  and the ball bond  371  both can be made of copper, tin, or aluminum, as shown in  FIG. 7C . 
         [0038]    After bonding the ball bond  371  on the first bump  361 , the capillary  383  can be moved from the first bump  361  to the bump  365 . The wire  37  carried in the capillary  383  can be pressed against the bump  365 , thereby forming the bonding wire  373  between the first die  331  and the second die  333 , as shown in  FIG. 7D . In addition, the wire  37  can be a copper wire, tin wire, or aluminum wire, so that the ball bond  371 , the bonding wire  373 , and/or the bump  365  can be made of copper, tin, or aluminum. 
         [0039]    Referring to  FIG. 8 , there is shown a diagrammatic illustration of a wire bonding structure in accordance with an embodiment of the invention. The wire bonding structure  40  comprises a die  43  that connects with a lead  49 , wherein the die  43  can be positioned on a substrate  411  and the lead  49  can be positioned on a leadframe  413 . The die  43  comprises a first surface  431  and a second surface  433 ; the first surface  431  can be an active surface and the second surface  433  can be a back surface. 
         [0040]    There is at least one bond pad  45  positioned on the first surface  431  of the die  43 , and a bump  46  positioned on the bond pad  45 , wherein the bump  46  can be made of gold. A ball bond  471  can be positioned upon the bump  46 , and connected with the lead  49  by means of a bonding wire  473 . 
         [0041]    The present invention is not limited to the above-described embodiments. Various alternatives, modifications, and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.