Ribbon bonding tool and process

Abstract

An ultrasonic bond is formed using a bond tool foot having a waffle shape of thin protrusions and gaps between the protrusions. The tool is brought in contact with the ribbon to a depth to create depressions in a ribbon approximately 150 μm or less from the underlying bonding surface. The tool is then brought down further into the ribbon to contact the portions of the ribbon between the depressions, such as an additional 25 to 50 μm. The result is lightly bonded regions underneath the groove portions and highly bonded regions underneath the protrusions and around the perimeter of the bond. In another embodiment, an ultrasonic bond is formed along a partial width of a ribbon.

1 . A bonding tool for ultrasonic bonding a conductive material to an underlying surface, the tool, comprising: 
 a substrate adapted to impart ultrasonic power and a bonding force to the conductive material;    a plurality of protrusions extending from the substrate, wherein the length of the protrusions is the thickness of the conductive material less approximately 150 μm or less; and    a plurality of grooves between the protrusions.    
     
     
         2 . The bonding tool of  claim 1 , wherein the length of the protrusions is the thickness of the conductive material less approximately 100 μm.  
     
     
         3 . The bonding tool of  claim 1 , wherein the conductive material is a ribbon.  
     
     
         4 . The bonding tool of  claim 1 , wherein the cross-section of the protrusions is approximately 0.01 mm 2 .  
     
     
         5 . The bonding tool of  claim 1 , wherein the protrusions are approximately circular shaped.  
     
     
         6 . The bonding tool of  claim 1 , wherein the protrusions are approximately rectangular-shaped.  
     
     
         7 . The bonding tool of  claim 1 , wherein the protrusions are tapered.  
     
     
         8 . The bonding tool of  claim 1 , wherein a boundary between the substrate and the protrusions is curved.  
     
     
         9 . The bonding tool of  claim 1 , wherein a boundary between the substrate and the protrusions is angled.  
     
     
         10 . A method of ultrasonically bonding a conductive material to an underlying surface, the method comprising: 
 (a) forming a plurality of indentations in the conductive material, wherein the distance between the underlying surface and the bottom of the indentations is approximately 150 μm or less;    (b) depressing portions of the conductive material between the indentations, wherein the depressing is approximately 50 μm or less; and    (c) forming a first bond, wherein the bottom of the indentations are approximately 100 μm or less from the underlying surface.    
     
     
         11 . The method of  claim 10 , wherein the conductive material is a ribbon.  
     
     
         12 . The method of  claim 10 , wherein the forming and depressing are by ultrasonic power and bond force.  
     
     
         13 . The method of  claim 10 , further comprising repeating operations (a) to (c) at a location directly adjacent to the first bond to form a second bond next to the first bond.  
     
     
         14 . The method of  claim 10 , wherein the plurality of indentations form a waffle shape.  
     
     
         15 . The method of  claim 10 , wherein forming the first bond comprises forming lightly bonded areas between the indentations and strongly bonded areas below the indentations.  
     
     
         16 . The method of  claim 10 , wherein the indentations are approximately circular shaped.  
     
     
         17 . The method of  claim 10 , wherein the indentations are approximately rectangular shaped.  
     
     
         18 . The method of  claim 15 , wherein forming the first bond further comprises forming strongly bonded areas along the perimeter of the first bond.  
     
     
         19 . The method of  claim 11 , wherein the first bond is formed only on the inner portion of the ribbon.  
     
     
         20 . The method of  claim 19 , wherein the first bond is approximately circular shaped.  
     
     
         21 . The method of  claim 19 , wherein the first bond is approximately square shaped.  
     
     
         22 . A method of bonding a conductive material to an underlying surface using a bonding tool having a waffle shaped bond foot, the method comprising: 
 bringing the bonding tool into the conductive material, with a bond force and ultrasonic power, to a distance approximately 150 μm or less from the underlying surface to form a plurality of depressions in the conductive material;    bringing the bonding tool further into the conductive material, with a bond force and ultrasonic power, a distance approximately 50 μm or less to depress portions of the conductive material between the depressions; and    forming lightly bonded areas underneath areas between the depressions and strongly bonded areas underneath the depressions and along the perimeter of the conductive material.    
     
     
         23 . The method of  claim 22 , wherein the conductive material is a ribbon.  
     
     
         24 . A bond for electrically connecting a conductive material to an underlying surface, the bond comprising: 
 an upper surface comprising a plurality of indentations, the area underneath the indentations forming first bonds with the underlying surface of a first strength and the area underneath portions between the indentations forming second bonds with the underlying surface of a second strength less than the first strength; and    a lower surface contacting the underlying surface, wherein the indentations are approximately 100 μm or less from the underlying surface.    
     
     
         25 . The bond of  claim 24 , further comprising a perimeter forming third bonds with the underlying surface of a third strength greater than the second strength.  
     
     
         26 . The bond of  claim 24 , wherein the bond does not extend along the complete width of the conductive material.  
     
     
         27 . The bond of  claim 26 , wherein the conductive material is a ribbon.  
     
     
         28 . The bond of  claim 26 , wherein the bond is approximately circular shaped.  
     
     
         29 . The bond of  claim 26 , wherein the bond is approximately square shaped.  
     
     
         30 . A method of forming a bond on a conductive material using a bonding tool, the method comprising: 
 bringing the bonding tool onto an inner area of the conductive material with a bond force and ultrasonic power, and    forming a bond only at the inner area of the conductive material.    
     
     
         31 . The method of  claim 30 , wherein the bond is approximately circular shaped.  
     
     
         32 . The method of  claim 30 , wherein the bond is approximately square shaped.  
     
     
         33 . The method of  claim 30 , wherein the conductive material is a ribbon at least 2 mm wide.  
     
     
         34 . A bond structure for electrically connecting a conductive material to an underlying surface, the bond structure comprising: 
 a bonded portion on an interior portion of the conductive material; and    an unbonded portion along an outer portion of the conductive material.    
     
     
         35 . The bond structure of  claim 34 , wherein the bonded portion is approximately square shaped.  
     
     
         36 . The bond structure of  claim 34 , wherein the bonded portions is approximately circular shaped.  
     
     
         37 . The bond structure of  claim 34 , wherein the conductive material is a ribbon.  
     
     
         38 . The bond structure of  claim 37 , wherein the ribbon is at least 2 mm wide.