Warpage-reducing packaging design

Abstract

A flange and packaging assembly characterized by a structural lip configured to impart resistance to thermal-induced deformation (i.e. “stiffness”) to the flange during elevated temperature die attachment processes. The stiffness is achieved through appropriate configuration of the lip (height, width and shape) and is sufficient to at least partially counteract the stresses generated from coefficient of thermal expansion differentials between the flange and a die attached to it. The lip may be molded or otherwise formed with the flange as a unitary lip-stiffened flange, or may be a separate structure that is affixed to the flange. The flange has a lip-stiffened region for die attachment. This region may be raised above the first surface of the substrate base for enhanced stiffening, and may be in the form of a single pedestal supporting a single or multiple die, or may be a series of raised pedestals, each supporting one or more die. The leads may be embedded in a polymetric material that is attached to the flange that is of sufficient thickess to provide the required stiffness. The embedded leads may be shaped and formed so that the desired seating plane height is achieved. The lead form placement can be either on the interior or exterior of the embedded polymetric material. The polymetric material can be supported along the edge of the flange or be seated on a part of an extrusion from the flange.

1 . A packaging flange comprising: 
 a flange having a first surface and a second surface opposed to the first, the first surface of the flange comprising a first region having a lip extending thereon, the first region spaced from a second region adapted to receive at least one die, the lip configured to impart stiffness to the flange, the stiffness sufficient to at least partially counteract thermally-induced stresses generated from coefficient of thermal expansion differentials between the flange and a die during an elevated temperature die attachment process.    
     
     
         2 . The flange of  claim 1 , wherein the second region comprises a pedestal comprising a surface sized and shaped to support at least one die thereon.  
     
     
         3 . The flange of  claim 2 , wherein the second region comprises a plurality of pedestals.  
     
     
         4 . The flange of  claim 1 , wherein the lip extends around a peripheral region of the first surface of the flange to form a frame surrounding the second region.  
     
     
         5 . The flange of  claim 4 , wherein the second region comprises a pedestal comprising a surface sized and shaped to support at least one die thereon.  
     
     
         6 . The flange of  claim 4 , wherein the second region comprises a plurality of pedestals.  
     
     
         7 . The flange of  claim 1 , wherein the lip is molded in one piece with the flange base.  
     
     
         8 . The flange of  claim 1 , wherein the ratio of stiffening lip height to flange thickness is from about 0.15 to about 0.25.  
     
     
         9 . A die assembly comprising: 
 a flange having a first surface and a second surface opposed to the first, the first surface of the flange comprising a first region having a lip extending thereon, the first region spaced from a second region adapted to receive at least one die, the lip configured to impart stiffness to the flange, the stiffness sufficient to at least partially counteract thermally-induced stresses generated from coefficient of thermal expansion differentials between the substrate and a die to be mounted thereon in an elevated temperature die attachment process;    at least one die mounted in the second region; and    leads for electrical contact with the die, the leads configured to preserve a seating plane, the seating plane spaced from a plane of the second surface of the flange.    
     
     
         10 . The assembly of  claim 9 , wherein the leads are embedded in an organic composition and the molded leads have end-portions embedded in the lip.  
     
     
         11 . The assembly of  claim 9 , wherein the leads are embedded in an organic composition and the molded leads extend from raised inboard end lead portions nearest the die to lower out board lead end portions aligned substantially within the seating plane.  
     
     
         12 . The assembly of  claim 9 , wherein the second region comprises a pedestal comprising a surface adapted to support at least one die thereon.  
     
     
         13 . The assembly of  claim 9 , wherein the second region comprises a plurality of pedestals.  
     
     
         14 . A die assembly comprising: 
 a packaging flange having a first surface and a second surface opposed to the first, the first surface of the flange comprising a first region having a lip extending thereon, the first region spaced from a second region adapted to receive at least one die, the flange having a body configured to impart stiffness to the flange, the stiffness sufficient to at least partially counteract thermally-induced stresses generated from coefficient of thermal expansion differentials between the flange and a die to be mounted thereon during an elevated temperature die attachment process.    
     
     
         15 . The assembly of  claim 14 , wherein the body of the flange has thickness in the rage from about 65 to about 100 mils.  
     
     
         16 . The assembly of  claim 14 , wherein the first region extends along a side of the flange and the lip extends upward above the upper surface of the flange.  
     
     
         17 . The assembly of  claim 16 , further comprising leads, the leads having inboard end portions embedded along a length of a lip wall and extending to an upper surface of the lip to permit attachment of connections to die on the flange.  
     
     
         18 . The assembly of  claim 14  wherein the first region extends along a side of the flange, and the flange comprises a platform in the first region, the lip resting on the platform.  
     
     
         19 . The assembly of  claim 18  further comprising leads, the leads having inboard end portions embedded along a length of a lip wall and extending to an upper surface of the lip to permit attachment of connections to die on the flange.  
     
     
         20 . The assembly of  claim 14 , further comprising at least one pedestal in the second region.