Retaining ring interconnect used for 3-D stacking

Abstract

A retaining ring interconnect. A retaining ring is formed on a perimeter of a pad on each of two adjoining surfaces of two PCB substrates. A conductive paste is applied between the pads on the two adjoining surfaces. The retaining rings are aligned and facing with each other. By performing a heat compression process, the retaining rings are connected to encompass the conductive paste. A eutectic bond is thus formed to bond the two PCB substrates.

What is claimed is:  
     
         1 . A retaining ring interconnect, comprising: 
 two pads disposed on two adjoining surfaces of two stacked substrates, each of the two pads including a peripheral retaining ring, the two retaining rings being aligned with and connected to each other; and    a conductive paste disposed between the two pads and contained by the two retaining rings thereof.    
     
     
         2 . The retaining ring interconnect according to  claim 1 , further comprising an adhesive layer bonding the two adjoining surfaces of the two substrates to each other.  
     
     
         3 . The retaining 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 retaining ring interconnect according to  claim 3 , wherein each pad formed on the distal surface has a height of about 0.0007 inches.  
     
     
         5 . The retaining ring interconnect according to  claim 1 , wherein the adhesive layer includes a glass resin pregreg.  
     
     
         6 . The retaining ring interconnect according to  claim 1 , wherein each of the two pads including the retaining ring has a total height of about 0.001 inches.  
     
     
         7 . The retaining ring interconnect according to  claim 6 , wherein each of the retaining rings of the two pads has a height of about 0.0005 inches.  
     
     
         8 . The retaining ring interconnect according to  claim 1 , wherein each of the retaining rings has an inner diameter of about 0.0006 inches and an outer diameter of about 0.0008 inches.  
     
     
         9 . The retaining ring interconnect according to  claim 1 , wherein the retaining rings are formed of copper.  
     
     
         10 . The retaining ring interconnect according to claim  2 , wherein the adhesive layer has a thickness of about 0.002 inches.  
     
     
         11 . A retaining ring interconnect process, comprising the steps of: 
 (a) providing two substrates, each of the substrates having at least one first pad on one surface thereof;    (b) forming a retaining ring on a peripheral portion of each of the first pads;    (c) aligning and facing the retaining rings of the two substrates with each other;    (d) applying a conductive paste between the facing retaining rings; and    (e) stacking the two substrates such that the conductive paste is compressed between the first pads.    
     
     
         12 . The retaining ring interconnect process according to  claim 11 , wherein step (a) comprises providing a second pad on a distal surface of each of the two substrates.  
     
     
         13 . The retaining ring interconnect process according to  claim 12 , wherein step (a) further comprises electrically connecting the first and the second pads of each of the two substrates by a conductive via therethrough.  
     
     
         14 . The retaining ring interconnect process according to  claim 11 , wherein step (d) comprises applying an adhesive layer between the surfaces of the two substrates to bond the substrates to each other.  
     
     
         15 . The retaining ring interconnect process according to  claim 14 , wherein step (d) comprises applying the conductive paste within the adhesive layer using a lased via technique.  
     
     
         16 . The retaining ring interconnect process according to  claim 11 , wherein step (e) comprises forming an eutectic bond of the conductive paste between the two first pads by controlling pressure and temperature.