Systems and methods for maximizing signal integrity on circuit boards
A circuit board may include a plurality of electrically-conductive layers separated and supported by layers of insulating material laminated together and a via electrically coupled to a first layer of the circuit board and coupled to a second layer of the circuit board, the via comprising a first via portion comprising electrically-conductive material and having a first diameter and a first depth from a surface of the circuit board and a second via portion comprising electrically-conductive material and having a second diameter smaller than the first diameter and a second depth from the first depth.
1. A circuit board, comprising:
a plurality of electrically-conductive layers separated and supported by layers of insulating material laminated together;
a first via having a uniform diameter throughout; and
a second via electrically coupled to a first layer of the circuit board and coupled to a second layer of the circuit board, the second via comprising:
a first via portion comprising electrically-conductive material and having a first diameter and a first depth from a surface of the circuit board; and
a second via portion comprising electrically-conductive material and having a second diameter smaller than the first diameter and a second depth from the first depth; wherein both the first diameter and the second diameter of the second via are smaller than the uniform diameter of the first via.
2. The circuit board of claim 1 , wherein:
the first via portion comprises a first cylindrical tube of the first diameter; and
the second via portion comprises a second cylindrical tube of the second diameter in series with the first via portion.
3. The circuit board of claim 2 , wherein together the first cylindrical tube and the second cylindrical tube form one continuous tube of differing diameters.
4. The circuit board of claim 1 , wherein the first diameter and the second diameter are approximately concentric.
5. The circuit board of claim 1 , wherein the second via comprises a layer of electrically-conductive material formed on interior walls of an opening through the circuit board.
6. The circuit board of claim 1 , wherein a sum of the first depth and the second depth equals a thickness of the circuit board.
7. An information handling system comprising:
an enclosure; and
a circuit board housed in the enclosure, the circuit board comprising:
a plurality of electrically-conductive layers separated and supported by layers of insulating material laminated together;
a first via having a uniform diameter throughout; and
a second via electrically coupled to a first layer of the circuit board and coupled to a second layer of the circuit board, the second via comprising:
a first via portion comprising electrically-conductive material and having a first diameter and a first depth from a surface of the circuit board; and
a second via portion comprising electrically-conductive material and having a second diameter smaller than the first diameter and a second depth from the first depth;
wherein both the first diameter and the second diameter of the second via are smaller than the uniform diameter of the first via.
8. The information handling system of claim 7 , wherein:
the first via portion comprises a first cylindrical tube of the first diameter; and
the second via portion comprises a second cylindrical tube of the second diameter in series with the first via portion.
9. The information handling system of claim 8 , wherein together the first cylindrical tube and the second cylindrical tube form one continuous tube of differing diameters.
10. The information handling system of claim 7 , wherein the first diameter and the second diameter are approximately concentric.
11. The information handling system of claim 7 , wherein the second via comprises a layer of electrically-conductive material formed on interior walls of an opening through the circuit board.
12. The information handling system of claim 7 , wherein a sum of the first depth and the second depth equals a thickness of the circuit board.
13. A method for forming a circuit board, comprising:
forming a plurality of conductive layers separated and supported by layers of insulating material laminated together;
forming a first via between layers of the circuit board; the first via having a uniform diameter throughout; and
forming a second via electrically coupled to a first layer of the circuit board and coupled to a second layer of the circuit board, the second via comprising:
a first via portion comprising electrically-conductive material and having a first diameter and a first depth from a surface of the circuit board; and
a second via portion comprising electrically-conductive material and having a second diameter smaller than the first diameter and a second depth from the first depth;
wherein both the first diameter and the second diameter of the second via are smaller than a diameter of the first via.
14. The method of claim 13 , wherein:
the first via portion comprises a first cylindrical tube of the first diameter; and
the second via portion comprises a second cylindrical tube of the second diameter in series with the first via portion.
15. The method of claim 14 , wherein together the first cylindrical tube and the second cylindrical tube form one continuous tube of differing diameters.
16. The method of claim 13 , wherein the first diameter and the second diameter are approximately concentric.
17. The method of claim 13 , wherein the second via comprises a layer of electrically-conductive material formed on interior walls of an opening through the circuit board.
18. The method of claim 13 , wherein a sum of the first depth and the second depth equals a thickness of the circuit board.
19. The method of claim 13 , wherein forming the second via comprises:
forming a first hole with the first diameter from the surface of the circuit board to the first depth;
forming a second hole with the second diameter from the first depth; and
plating interior surfaces exposed by the hole with electrically-conductive material.
20. The method of claim 13 , wherein:
forming the first hole comprises drilling the first hole with a first drill bit having approximately the first diameter; and
forming the second hole comprises drilling the second hole with a second drill bit having approximately the second diameter.