Microelectronic assemblies and methods of making microelectronic assemblies

Abstract

A microelectronic subassembly includes a substrate having a first surface, and one or more microelectronic elements positioned above the first surface of the substrate, each microelectronic element having a contact bearing face confronting the first surface of the substrate and a back surface remote therefrom. The subassembly includes a substantially rigid plate attached to the back surfaces of the microelectronic elements, an array of flexible leads extending between the substrate and the microelectronic elements, the leads having first ends attached to the substrate and second ends attached to the contacts of the microelectronic elements, and an at least partially cured spacer material sandwiched between the substantially rigid plate and the substrate for holding the contact bearing faces of the microelectronic elements at a precise height above the substrate.

1 . A microelectronic subassembly comprising: 
 a substrate having a first surface;    one or more microelectronic elements positioned above the first surface of said substrate, each said microelectronic element having a contact bearing face confronting the first surface of said substrate and a back surface remote therefrom;    a substantially rigid plate attached to the back surfaces of said microelectronic elements;    an array of flexible leads extending between said substrate and said microelectronic elements, said leads having first ends attached to said substrate and second ends attached to the contacts of said microelectronic elements; and    an at least partially cured spacer material sandwiched between said substantially rigid plate and said substrate for holding the contact bearing faces of said microelectronic elements at a precise height above said substrate.    
   
   
       2 . The microelectronic assembly as claimed in  claim 1 , wherein said at least partially cured spacer material is fast curing.  
   
   
       3 . The microelectronic assembly as claimed in  claim 1 , wherein said at least partially cured spacer material is substantially rigid.  
   
   
       4 . The microelectronic assembly as claimed in  claim 1 , wherein said at least partially cured spacer material has a low coefficient of thermal expansion.  
   
   
       5 . The microelectronic assembly as claimed in  claim 1 , wherein said spacer material is disposed at a perimeter of said substantially rigid plate.  
   
   
       6 . The microelectronic subassembly as claimed in  claim 1 , wherein said at least partially cured spacer material is acrylic.  
   
   
       7 . The microelectronic subassembly as claimed in  claim 1 , wherein said substantially rigid plate is made of a material selected from the group consisting of copper, nickel, their alloys, plastics and combinations thereof.  
   
   
       8 . The microelectronic subassembly as claimed in  claim 1 , wherein said substantially rigid plate is thermally conductive.  
   
   
       9 . The microelectronic subassembly as claimed in  claim 1 , wherein said substantially rigid plate is adhered to the back surfaces of said microelectronic elements with an adhesive.  
   
   
       10 . The microelectronic subassembly as claimed in  claim 9 , wherein said adhesive is thermally conductive.  
   
   
       11 . The microelectronic subassembly as claimed in  claim 1 , wherein said one or more microelectronic elements are selected from the group consisting of semiconductor wafers, semiconductor chips, packaged semiconductor chips, and packaged semiconductor wafers.  
   
   
       12 . The microelectronic subassembly as claimed in  claim 1 , wherein said substrate comprises a flexible dielectric sheet, a FR4 board, a FR5 board, or a ceramic plate.  
   
   
       13 . The microelectronic subassembly as claimed in  claim 1 , wherein said conductive leads are made of a material selected from the group consisting of aluminum, gold, copper, tin, their alloys and combinations thereof.  
   
   
       14 . A method of making microelectronic packages comprising: 
 providing a substrate having a plurality of conductive leads at a first surface thereof, said conductive leads having first ends permanently attached to said substrate and second ends remote from the first ends, the second ends of said leads being movable relative to said first ends;    providing a microelectronic element having contacts on a front surface thereof and a back surface remote therefrom and juxtaposing the front contact bearing surface of said microelectronic element with the first surface of said substrate;    connecting the first ends of said leads with the contacts of said microelectronic element;    moving said microelectronic element away from said substrate so as to vertically extend said leads between said substrate and said microelectronic element, wherein said microelectronic element is moved to a precise height above said substrate; and    while maintaining said microelectronic element at the precise height above said substrate, dispensing a spacer material between said microelectronic element and said substrate and at least partially curing said spacer material, wherein said at least partially cured spacer material holds said microelectronic element at the precise height above said substrate.    
   
   
       15 . The method as claimed in  claim 14 , wherein said microelectronic element is a semiconductor wafer or one or more semiconductor chips.  
   
   
       16 . The method as claimed in  claim 14 , wherein said substrate comprises a flexible dielectric sheet, a FR4 board, a FR5 board, or a ceramic plate.