Structure of a ball bump for wire bonding and the formation thereof

Abstract

The ball bump mainly includes a body and a protrusion. The protrusion is located at the upper of the body and essentially consists of a flat upper surface with an annular inclination. The flat upper surface and the annular inclination together define the area for wire bonding. The method of the formation of the ball bump of wire bonding mainly comprises steps of: an end of a wire held by a bonding machine is melted to form a ball; the bonding machine bonds the ball onto the bonding pad to form a ball bump; the bonding tool moves upward a predetermined vertical distance and the clamp of the bonding tool is then opened; the bonding tool is moved a predetermined horizontal distance to reduce the connection part of wire connecting to the upper of the ball bump for the convenience of wire cutting, and this forms a protrusion on the ball bump consisting of a flat upper surface with an annular inclination; the bonding tool is again moved upward a predetermined vertical distance, and the clamp releases the wire for the ball bump process which follows; the clamp is closed to hold the wire and is moved upward to pull the wire, and the wire is cut along the heat affected zone and leaves a smaller tip on the ball bump.

What is claimed is:  
     
         1 . A method of formation of a ball bond of wire bonding comprising steps of: 
 an end of a wire held by a bonding machine is melted to form a ball;    the bonding machine which bonds the ball onto a bonding pad to form a ball bump;    the bonding tool which is moved upward a predetermined vertical distance to form an annular inclination on a top of the ball bump, and a clamp of the bonding tool is then opened;    the bonding tool which is moved a predetermined horizontal distance to reduce the connection part of wire for the convenience of wire cutting, and this forms a protrusion on the ball bump consisting of a flat upper surface and an annular inclination;    the bonding tool which is again moved upward a predetermined vertical distance, and the clamp releases the wire for the ball bump process which follows; and    the clamp which is closed to hold the wire and moved upward to pull the wire, and the wire is cut along the heat-affected zone.    
     
     
         2 . The method of formation of the ball bond of wire bonding as defined in    claim 1   , wherein the bonding tool is moved upward in vertical direction to a specified height to form the annular inclination on a upper of the ball bump; the height should be equal to the height of an inclination of an opening in the bonding tool.  
     
     
         3 . The method of formation of the ball bond of wire bonding as defined in    claim 1   , wherein the bonding tool is moved a predetermined horizontal distance to form a protrusion on the ball bump, whose width is preferably ⅔ - ⅞ of the diameter of the wire.  
     
     
         4 . A structure of a ball bump of wire bonding comprising: 
 a body, and    a protrusion located at the upper of the body and essentially consisting of a flat upper surface with an annular inclination which together define an area for wire bonding.    whereas the flat upper surface and the annular inclination provide a regular structure of the ball bump and thus reduce the variability of wire bonding.    
     
     
         5 . The structure of a ball bump of wire bonding as defined in    claim 4   , wherein the height of the protrusion of the ball bump is equal to a height of an opening of the bonding tool.  
     
     
         6 . The structure of a ball bump of wire bonding as defined in    claim 4   , wherein the width of the protrusion is equal to ⅔-⅞ of the diameter of a wire.  
     
     
         7 . The structure of a ball bump of wire bonding as defined in    claim 4   , wherein the protrusion further has a smaller tip at the edge of the flat upper surface of the protrusion.