Circuit board via structure for high speed signaling

Abstract

One embodiment of the invention comprises an improved via structure for use in a printed circuit board (PCB), and method for fabricating the same. The via allows for the passage of a signal from one signal plane to another in the (PCB), and in so doing transgresses the power and ground planes between the signal plane. To minimize EM disturbance between the power and ground planes, signal loss due to signal return current, and via-to-via coupling, the via is shielded within two concentric cylinders, each coupled to one of the power and ground planes.

1 . A via structure in a circuit structure having different planes, comprising: 
 a first signal trace at a first plane,    a first voltage at a second plane    a second voltage at a third plane;    a second signal trace at a fourth plane;    a via coupling the first signal trace to the second signal trace through the second and third planes,    wherein the first voltage is coupled to a first shield around the via, and wherein the second voltage is coupled to second shield around the first shield.    
   
   
       2 . The via structure of  claim 1 , wherein the first voltage is power or ground, and wherein the second voltage is the other of power or ground.  
   
   
       3 . The via structure of  claim 1 , wherein at least one of the first and second shields are cylindrical.  
   
   
       4 . The via structure of  claim 1 , wherein the first and second shields are concentric with the via.  
   
   
       5 . The via structure of  claim 1 , wherein the via comprises an axis, and wherein the first shield substantially encompasses the via perpendicular to the axis.  
   
   
       6 . The via structure of  claim 5 , wherein the second shield substantially encompasses the first shield perpendicular to the axis.  
   
   
       7 . The via structure of  claim 1 , wherein the first and second shields span through a dielectric between the second and third planes.  
   
   
       8 . The via structure of  claim 1 , wherein the circuit structure comprises a printed circuit board.  
   
   
       9 . A via structure, comprising: 
 a signal path transgressing through a via, wherein the via passes through a power plane and a ground plane along an axis;    a first conductor coupled to either the power plane or the ground plane, wherein the first conductor surrounds the via perpendicular to the axis; and    a second conductor coupled to the other of the power plane or the ground plane, wherein the second conductor surrounds the first conductor perpendicular to the axis.    
   
   
       10 . The via structure of  claim 9 , wherein the via comprises a circuit board via.  
   
   
       11 . The via structure of  claim 9 , wherein at least one of the first and second conductors are cylindrical.  
   
   
       12 . The via structure of  claim 9 , wherein the first and second conductors are concentric with the via.  
   
   
       13 . The via structure of  claim 9 , wherein the first and second conductors span through a dielectric between the power and ground planes.  
   
   
       14 . A via structure, comprising: 
 a signal path passing through a via in a circuit board, wherein the via passes through a power plane and a ground plane along an axis; and    a shield structure for preventing the via from electromagnetic disturbance, wherein the shield structure comprises a first conductor coupled to the power plane and a second conductor coupled to the ground plane.    
   
   
       15 . The via structure of  claim 14 , wherein at least one of the first and second conductors is cylindrical.  
   
   
       16 . The via structure of  claim 14 , wherein the first and second conductors are concentric with the via.  
   
   
       17 . The via structure of  claim 14 , wherein the via comprises an axis, and wherein the first and second shields substantially encompasses the via perpendicular to the axis.  
   
   
       18 . The via structure of  claim 14 , wherein the first and second conductors span through a dielectric between the power and ground planes.  
   
   
       19 . A via structure, comprising: 
 a signal path transgressing through a via in a circuit board, wherein the via passes through a power plane and a ground plane along an axis; and    a means for shielding the via from electromagnetic disturbance.    
   
   
       20 . The via structure of  claim 19 , wherein the means for shielding substantially encompasses the via perpendicular to the axis.  
   
   
       21 . The via structure of  claim 19 , wherein the means for shielding is coupled to a power and a ground potential.  
   
   
       22 . The via structure of  claim 19 , wherein the wherein the means for shielding is concentric with the axis.  
   
   
       23 . The via structure of  claim 19 , wherein the means for shielding is cylindrical.  
   
   
       24 . A method for forming a via, comprising: 
 forming a first shield coupled to a power plane on a first side of a circuit board;    forming a second shield coupled to a ground plane on a second side of the circuit board; and    forming a via within the first and second shields.    
   
   
       25 . The method of  claim 24 , wherein forming either shield on either side of the board comprises: 
 forming a hole in the side of the circuit board, wherein the hole comprises vertical edges and a horizontal edge;    positioning a conductor only on the edges of the hole.    
   
   
       26 . The method of  claim 25 , further comprising filling the hole with a dielectric after the conductor has been positioned on the edges of the hole.  
   
   
       27 . The method of  claim 25 , wherein the conductor couples to either a power or ground plane.  
   
   
       28 . The method of  claim 24 , wherein forming both shields on both sides of the board comprises: 
 forming a hole in the side of the circuit board, wherein the hole comprises vertical edges and a horizontal edge;    positioning a conductor only on the edges of the hole.    
   
   
       29 . The method of  claim 28 , further comprising filling the hole with a dielectric after the conductor has been positioned on the edges of the hole.  
   
   
       30 . The method of  claim 28 , wherein a first of the conductors couples to a power plane, and wherein a second of the conductors couples to a ground plane.  
   
   
       31 . A method for forming a via, comprising: 
 forming a via;    enclosing the via in a first conductor coupled to either a power or ground potential; and    enclosing the first conductor in a second conductor coupled to the other of the power and ground potential.    
   
   
       32 . The method of  claim 31 , wherein at least one of the first and second conductors are cylindrical.  
   
   
       33 . The method of  claim 31 , wherein the first and second conductors are concentric with the via.  
   
   
       34 . The method of  claim 31 , wherein the via comprises an axis, and wherein the first and second conductors substantially encompasses the via perpendicular to the axis.  
   
   
       35 . The method of  claim 31 , wherein the first and second conductors are positioned in a dielectric perpendicularly to a plane of the circuit board.  
   
   
       36 . The method of  claim 35 , wherein the first and second conductors span through a dielectric between planes defined by the power and ground potential.  
   
   
       37 . The method of  claim 31 , wherein the via is formed in a circuit board.