System and method for improving isolation in high-density laminated printed circuit boards

Abstract

A system and method of isolating a layer-to-layer transition between conductors in a multilayer printed circuit board includes formation of a first ground via at least partially surrounding a first signal conductor in at least one layer of the printed circuit board and formation of a second ground via at least partially surrounding a second signal conductor in another layer of the printed circuit board. The first and second ground vias are plated with a conductive material.

What is claimed is: 
     
         1 . A method of manufacturing a multilayer printed circuit board comprising:
 forming a first signal conductor on a surface of a first dielectric layer;   forming a second dielectric layer on the first signal conductor;   forming a first metal layer on a surface of the second dielectric layer opposite the first signal conductor;   forming a third dielectric layer on the first metal layer;   forming a second signal conductor on a surface of the third dielectric layer opposite the first metal layer;   forming a via extending through at least a portion of the first, second and third dielectric layers and electrically connecting a first end of the first signal conductor to a first end of the second signal conductor;   forming a first ground via at least partially surrounding the first end of the second signal conductor; and   forming a second ground via at least partially surrounding the first end of the first signal conductor and extending from the first metal layer through the first dielectric layer.   
     
     
         2 . The method of  claim 1 , wherein the first ground via comprises a C-shaped profile. 
     
     
         3 . The method of  claim 2 , wherein the second ground via comprises a C-shaped profile. 
     
     
         4 . The method of  claim 1 , wherein the steps of forming the first and second ground vias further comprise plating the first ground via and the second ground via with a conductive material. 
     
     
         5 . The method of  claim 1 , wherein the step of forming the second signal conductor comprises forming a waveguide in a second metal layer arranged on the third dielectric layer, wherein the via extends only from the first end of the first signal conductor to the first end of the second signal conductor. 
     
     
         6 . The method of  claim 5 , wherein the first ground via extends from the second metal layer through the third dielectric layer. 
     
     
         7 . The method of  claim 6 , further comprising electrically connecting the first ground via to the first metal layer. 
     
     
         8 . The method of  claim 1 , wherein the step of forming the first signal conductor comprises forming a stripline. 
     
     
         9 . The method of  claim 1 , further comprising electrically connecting the second ground via to a metal layer arranged on a surface of the third dielectric layer opposite the first signal conductor. 
     
     
         10 . A method of isolating layer-to-layer transitions between conductors in a multilayer printed circuit board comprising:
 forming a printed circuit board including: a plurality of dielectric layers including first, second and third dielectric layers; a first signal conductor arranged on a surface of the first dielectric layer, and a second signal conductor arranged between the second dielectric layer and the third dielectric layer; and a via extending through at least a portion of the plurality of dielectric layers and electrically connecting a first end of the first signal conductor to a first end of the second signal conductor;   surrounding the first end of the first signal conductor at least partially with a first ground via; and   surrounding the first end of the second signal conductor at least partially with a second ground via, the second ground via extending from a metal layer arranged between the first dielectric layer and the second dielectric layer and through the third dielectric layer.   
     
     
         11 . The method of  claim 10 , wherein the first ground via comprises a C-shaped profile uniformly extending through a first portion of the plurality of dielectric layers and having first and second free ends connected by a curved portion. 
     
     
         12 . The method of  claim 11 , wherein the first and second free ends of the C-shaped first ground via define an opening having a length less than that of the curved portion. 
     
     
         13 . The method of  claim 12 , wherein the second ground via comprises a C-shaped profile having first and second free ends connected by a curved portion, and wherein the first and second free ends of the C-shaped second ground via define an opening having a length less than that of the curved portion. 
     
     
         14 . The method of  claim 13 , wherein the curved portion of each of the C-shaped first ground via and second ground via comprises a constant radius of curvature. 
     
     
         15 . The method of  claim 13 , wherein the first and second signal conductors are arranged through the openings of the first ground via and the second ground via, respectively. 
     
     
         16 . The method of  claim 10 , wherein the first signal conductor comprises a waveguide defined in a metal layer arranged on the first dielectric layer. 
     
     
         17 . The method of  claim 16 , wherein the first ground via extends from the metal layer arranged on the first dielectric layer and through the first dielectric layer. 
     
     
         18 . The method of  claim 17 , wherein the first ground via is electrically connected to the metal layer arranged between the first dielectric layer and a second dielectric layer. 
     
     
         19 . The method of  claim 18 , wherein the second signal conductor comprises a stripline embedded in the plurality of dielectric layers. 
     
     
         20 . The method of  claim 10 , wherein the second ground via is electrically connected to a metal layer arranged on a surface of the third dielectric layer opposite the second signal conductor.