Post in ring interconnect using 3-D stacking

Abstract

A post in ring interconnect used for 3-D stacking. A retaining ring is formed on a pad on a bottom surface of a top PCB substrate to be stacked with a bottom PCB substrate. A post is formed on a pad on a top surface of the bottom PCB substrate. A conductive paste is applied on the pad on the bottom surface of the top PCB substrate and retained in a pocket partially defined by the retaining ring. The retaining ring is aligned with the post. By performing a compression step, a eutectic bond is formed between the top and bottom PCB substrates by the post and the conductive paste.

What is claimed is:  
     
         1 . A post in ring interconnect, comprising: 
 two pads disposed on two adjoining surfaces of two stacked substrates, an upper one of the two pads including a peripheral retaining ring which partially defines a pocket, and a lower one of the two pads including a central post, the post being aligned with the retaining ring; and    a conductive paste filled within a pocket defined by the retaining ring of the upper one of the two pads.    
     
     
         2 . The post in ring interconnect according to  claim 1 , further comprising: 
 an adhesive layer accommodating the post and bonding the two adjoining surfaces of the two substrates.    
     
     
         3 . The post in ring interconnect according to  claim 1 , wherein each of the two substrates has a distal surface including a pad formed thereon and electrically connected to the pad on the surface adjoining the other substrate by a conductive via.  
     
     
         4 . The post in ring interconnect according to  claim 2 , wherein the adhesive is selected from the group consisting of polyester, epoxy, acrylic, phenolic/butyral, and polyimide.  
     
     
         5 . The post in ring interconnect according to  claim 1 , wherein the two pads are formed of copper.  
     
     
         6 . The post in ring interconnect according to  claim 1 , wherein the retaining ring is formed of copper.  
     
     
         7 . The post in ring interconnect according to  claim 1 , wherein the post is formed of copper.  
     
     
         8 . The post in ring interconnect according to  claim 1 , wherein the post has an outer diameter smaller than an inner diameter of the retaining ring.  
     
     
         9 . A post in ring interconnect process, comprising: 
 a) providing a top substrate having a top surface and a bottom surface which are each provided with a pad thereon;    b) forming a retaining ring on a peripheral portion of the pad on the bottom surface of the top substrate;    c) applying a conductive paste within the retaining ring on the pad on the bottom surface of the top substrate;    d) providing a bottom substrate having a top surface and a bottom surface which are each provided with a pad thereon;    e) forming a post on a central portion of the pad on the top surface of the bottom substrate;    f) aligning the post and the pad on the bottom surface of the top substrate; and    g) stacking the two substrates such that the conductive paste is compressed between the pad on the bottom surface of the top substrate and the post.    
     
     
         10 . The post in ring interconnect process according to  claim 9 , wherein step (a) comprises providing a via to connect the pads on the top and bottom surfaces to each other.  
     
     
         11 . The post in ring interconnect process according to  claim 9 , wherein step (d) comprises providing a via to connect the pads on the top and bottom surfaces to each other.  
     
     
         12 . The post in ring interconnect process according to  claim 9 , wherein step (g) includes forming a eutectic bond of the conductive paste between the pad on the bottom surface of the top substrate and the post by controlling pressure and temperature.  
     
     
         13 . The post in ring interconnect process according to  claim 9 , wherein step (f) comprises applying an adhesive layer to the top surface of the bottom substrate.  
     
     
         14 . The post in ring interconnect process according to  claim 13 , wherein step (f) further comprises forming a lased hole in the adhesive layer to accommodate the post.  
     
     
         15 . The post in ring interconnect process according to  claim 13 , wherein step (f) comprises drilling a hole in the adhesive layer to accommodate the post.  
     
     
         16 . The post in ring interconnect process according to  claim 13 , wherein the step (g) comprises reflowing the adhesive layer via a lamination process to tightly bond the bottom surface of the top substrate to the top surface of the bottom substrate.