Deformation-absorbing leadframe for semiconductor devices

Abstract

A leadframe structure for use with an integrated circuit chip, comprising a chip mount pad having an area smaller than said chip intended for mounting; a plurality of support members, each attached externally to the perimeter of said pad and internally to said leadframe; and each said support member having at least one portion located within the perimeter of said chip in a configuration operable to absorb thermally induced deformations of said support member.

We claim:  
     
         1 . A leadframe structure for use with an integrated circuit chip, comprising: 
 a chip mount pad having an area smaller than said chip intended for mounting;    a plurality of support members, each attached externally to the perimeter of said pad and internally to said leadframe; and    each said support member having at least one portion located within the perimeter of said chip in a configuration operable to absorb thermally induced deformations of said support member.    
     
     
         2 . The leadframe according to  claim 1  wherein two of said support members intersect at a point near the center of said chip mount pad.  
     
     
         3 . The leadframe according to  claim 2  wherein the thickness of said intersecting members is greater than the remaining portions thereof.  
     
     
         4 . The leadframe according to  claim 1  further having a support member portion located outside the perimeter of said chip, configured in a geometry to absorb thermally induced deformations of said support member.  
     
     
         5 . The leadframe according to  claim 1  wherein said structure comprises a sheet-like starting configuration having a thickness in the range from about 100 to 300 μm.  
     
     
         6 . The leadframe according to  claim 5  wherein said sheet-like starting configuration is selected from a group of metals consisting of copper, copper alloy, brass, aluminum, iron-nickel alloy, and invar.  
     
     
         7 . The leadframe according to  claim 1  wherein said support member portion has a meandering geometry.  
     
     
         8 . The leadframe according to  claim 1  wherein said support member portion has sinusoidal geometry.  
     
     
         9 . The leadframe according to  claim 1  wherein said support member can accommodate a plurality of bendings.  
     
     
         10 . A semiconductor device comprising: 
 a leadframe comprising a chip mount pad having an area smaller than said chip, and a plurality of support members, each attached externally to the perimeter of said pad and internally to said leadframe;    each said support members having at least one portion located within the perimeter of said chip in a configuration operable to absorb thermally induced deformations of said support member;    said leadframe further comprising a plurality of lead segments, each having a first end near said mount pad and a second end remote from said mount pad;    an integrated circuit chip, having an active and a passive surface, attached to said mount pad;    bonding wires interconnecting said active chip surface and said first ends of said lead segments;    encapsulation material surrounding said chip, said bonding wires and said first ends of said lead segments, whereby said passive chip surface has direct contact to said encapsulation material, and said support member portions are operational to absorb thermally induced deformations; and    said encapsulation material leaving said second ends of said lead segments exposed, whereby said second ends are suitable for solder attachment to other parts.    
     
     
         11 . The device according to  claim 10  wherein said bonding wires are selected from a group consisting of gold, copper, aluminum, and alloys thereof.  
     
     
         12 . The device according to  claim 11  wherein said encapsulation material is a polymeric material selected from a group consisting of epoxy-based molding compounds suitable for adhesion to said passive chip surface.