Method for forming a plated microvia interconnect

Abstract

A method for forming a plated microvia interconnect. An external dielectric layer (EDL) is mounted on a substrate in direct mechanical contact with a conductive element thereon. An opening in the EDL exposes the conductive element and create a microvia in the EDL. A sidewall and bottom wall surface of the microvia are treated to promote adhesion of copper and are plated with a layer of copper that includes a copper layer on a copper seed layer and is in direct mechanical and electrical contact with the conductive element. A wet solder paste is deposited on the layer of copper to overfill a remaining portion of the microvia. The solder paste is reflowed to form a solder bump in and over the remaining portion of the microvia to form the plated microvia interconnect. A stiffener is attached to the EDL using a first adhesive.

1 . A method for forming a plated microvia interconnect, comprising: 
 mounting an external dielectric layer (EDL) on a surface of a substrate such that the EDL is in direct mechanical contact with a conductive element comprised by the surface of the substrate;    forming an opening in the EDL to expose the conductive element and create a microvia in the EDL;    treating a sidewall surface and a bottom wall surface of the microvia to promote adhesion of copper to the sidewall surface and the bottom wall surface;    plating the sidewall surface and the bottom wall surface of the microvia to form a layer of copper on the sidewall surface and the bottom wall surface, wherein the layer of copper is in direct mechanical and electrical contact with the conductive element, wherein said plating comprises: depositing a copper seed layer on the sidewall surface and the bottom wall surface of the microvia; and plating a copper layer on the copper seed layer such that the layer of copper comprises the copper seed layer and the copper layer;    depositing a wet solder paste on the layer of copper to overfill a remaining portion of the microvia;    reflowing the solder paste to form a solder bump in and over the remaining portion of the microvia to form the plated microvia interconnect; and    attaching a stiffener to the EDL using a first adhesive to adhere the stiffener to the EDL.    
   
   
       2 . The method of  claim 1 , wherein the method further comprises after said reflowing: 
 visually inspecting the microvia to determine whether the solder bump is missing.    
   
   
       3 . The method of  claim 1 , wherein the layer of copper has a thickness of about 1 mil on the sidewall surface and a thickness of about 0.7 mils on the bottom wall surface.  
   
   
       4 . The method of  claim 1 , wherein the method further comprise: 
 coupling a chip to the substrate by attaching the chip to the solder bump.    
   
   
       5 . The method of  claim 1 , wherein the method further comprises: 
 disposing an encapsulation material on the EDL, wherein the encapsulation material is in direct mechanical contact with the first adhesive.    
   
   
       6 . The method of  claim 1 , wherein the method further comprises: 
 disposing a cover plate over the stiffener using a second adhesive to adhere the cover plate to the stiffener.