Copper-based chip attach for chip-scale semiconductor packages

Abstract

A semiconductor device comprising a semiconductor chip having an active and a passive surface, the passive surface adhesively attached to a substrate film by means of a multilayer composite; this composite comprising a metal foil having first and second surfaces and an adhesive layer attached on each of these surfaces. The multilayer composite has an average modulus larger than the modulus of the encapsulating molding compound used in the semiconductor device. By applying the composite to assembling face-up chip-scale devices, stress in solder joints is reduced and solder fatigue life enhanced.

1 - 18 . (canceled)  
   
   
       19 : A method for assembling a semiconductor device, comprising the steps of: 
 providing a multilayer composite attachment film comprising a metal foil having first and second surfaces, a non-ultraviolet-curable adhesive layer attached on said first surface, and an ultraviolet-curable adhesive layer attached on said second surface;    providing a semiconductor wafer having an active and a passive surface;    placing said multilayer composite attachment film with said ultraviolet-curable adhesive layer onto a transparent support film;    attaching said passive surface of said semiconductor wafer onto said non-ultraviolet-curable adhesive layer of said multilayer composite attachment film; and    shining ultraviolet light through said transparent support film on said ultraviolet-curable adhesive layer in order to reduce the adhesive strength between said multilayer composite attachment film and said transparent support film.    
   
   
       20 : The method according to  claim 19  further comprising the steps of: 
 dicing said wafer and said multilayer composite attachment film into singulated chips;    providing an insulating substrate film, integral with electrically conductive routing lines, a first plurality of terminals on one surface of said insulating substrate film, and a second plurality of terminals on an opposite surface of said insulating substrate film;    picking one singulated chip at a time from said transparent support film and attaching said ultraviolet-curable adhesive layer on each singulated chip to said insulating substrate film;    curing said adhesive layers, creating hardened layers;    wire bonding said active surface of each chip to said first plurality of terminals on said insulating substrate film with bonding wires;    encapsulating each chip in molding compound so that said active surface of each chip, said bonding wires, and portions of said insulating substrate film are protected;    attaching solder balls to said second plurality of terminals on said insulating substrate film; and    singulating said insulating substrate film to create individual devices.    
   
   
       21 : The method according to  claim 20  wherein said step of singulating said insulating substrate film creates devices with outlines of chip-scale packages.