Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2001-02-01
2003-09-16
Cuneo, Kamand (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S255000, C174S260000, C174S262000, C361S760000, C361S761000, C361S763000, C361S782000, C361S794000
Reexamination Certificate
active
06621012
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the field of printed circuit boards, and more particularly to a printed circuit board comprising an internal electrical component positioned within a via of the printed circuit board to suppress impedance and/or save space.
BACKGROUND INFORMATION
A printed circuit board is a board that may hold integrated circuits commonly referred to as chips and other electronic components. Typically, a printed circuit board is made of conductive layers separated by non-conductive dielectric. Conductive pathways commonly referred to as vias may interconnect electrical components on different layers of the board. The vias may be created by drilling through the printed circuit board at the appropriate place where two or more layers will interconnect and allowing conductive material, e.g., copper, to run through the hole. The conductive material, e.g., copper, may coat only the side of the hole or fill the entire hole.
When high frequency Alternating Current (AC) signals change layers in a printed circuit board, an undesirable electrical disturbance commonly referred to as electromagnetic interference is produced as illustrated in FIG.
1
.
FIG. 1
illustrates a prior art printed circuit board
100
comprising a plurality of conductive layers
110
A-F separated by non-conductive dielectric. Printed circuit board
100
further comprises a plurality of vias
150
A-C. Layers
110
A-F may collectively or individually be referred to as layers
110
or layer
110
, respectively. Vias
150
A-C may collectively or individually be referred to as vias
150
or via
150
, respectively. As stated above, electromagnetic interference may result when high frequency AC signals change layers in a printed circuit board. For example, an input signal, e.g., high frequency AC signal, may travel along a path commonly referred to as a transmission line from a source
120
to a load
130
. The transmission line may be formed from two separate conductive paths. The first conductive path, commonly referred to as the signal path, may be from the etch, i.e., trace, on the top signal layer
110
, i.e., layer
110
A, of printed circuit board
100
to the etch, i.e., trace, on the bottom signal layer
110
, i.e., layer
110
F, through via
150
A of printed circuit board
100
. The second conductive path, commonly referred to as the reference path, may be between the reference layers
110
nearest to the conductive signal path, e.g., path between layers
110
E and
110
B. As the difference between the impedance of the input signal and reference layers
110
, e.g., layers
110
B,
110
E, increases, energy may be lost. The lost energy may appear as undesirable noise commonly referred to as electromagnetic interference. When a high frequency AC signal changes layers
110
in printed circuit board
100
, an impedance break may occur at the reference layer
110
, e.g., layer
110
B, nearest to the signal line, e.g., layer
110
A. The impedance break may result in a large impedance difference increasing undesired electromagnetic interference.
In prior art printed circuit boards, electromagnetic interference may be reduced by placing a surface mount capacitor on the outside layer of the printed circuit board as illustrated in
FIG. 1. A
surface mount capacitor
140
may be mounted on the surface layer
110
, e.g., layer
110
A, of printed circuit board
100
to reduce the undesirable impedance of the reference path side of the transmission line. Typically, surface mount capacitor
140
may be placed near the bus or data path commonly referred to as the high frequency via
150
, e.g., via
150
A, where the input signal, i.e., source signal, travels from the top signal layer
110
, i.e., layer
110
A, to the bottom signal layer
110
, i.e., layer
110
F. By placing surface mount capacitor
140
near the high frequency via
150
, i.e., via
150
A, an AC low impedance path between reference layers
110
B and
110
E through surface mount capacitor
140
may be formed thereby reducing the electromagnetic interference generated.
As the frequency of the source signal increases the impedance of the vias
150
, e.g., vias
150
B-C, used to connect surface mount capacitor
140
between the reference layers
110
, e.g., layers
110
B,
110
E, increases. As the impedance of the vias
150
, e.g., vias
150
B-C, increases, the impedance mismatch of the transmission line may be increased thereby creating electromagnetic interference. Subsequently, the frequency range of the input signal may be limited.
It would therefore be desirable to reduce the impedance within the reference path side of the high frequency transmission line. It would further be desirable to save space in the printed circuit board.
SUMMARY
The problems outlined above may at least in part be solved in some embodiments by embedding an electrical component within a via of the printed circuit board to reduce the impedance within the reference path and/or saving space within the printed circuit board.
In one embodiment, a printed circuit board comprises a plurality of conductive layers where one of the plurality of conductive layers is a first layer, e.g., top signal layer, and one of the plurality of conductive layers is a second layer, e.g., bottom signal layer. The printed circuit board further comprises two or more vias for interconnecting two or more conductive layers. One of the two or more vias is part of a signal path configured to carry a source signal from the first layer to the second layer. Furthermore, one of the two or more vias is part of a reference path configured to carry the source signal from a third layer to a fourth layer. The printed circuit board further comprises an electrical component embedded in the via that is part of the reference path between two conductive layers to reduce the impedance within the reference path.
In another embodiment of the present invention, a printed circuit board comprises a plurality of conductive layers. The printed circuit board further comprises two or more vias for interconnecting two or more conductive layers. The printed circuit board further comprises an electrical component embedded in a particular via between two conductive layers instead of placing the electrical component on the surface of the printed circuit board thereby saving space within the printed circuit board.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.
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Crockett Timothy Wayne
Minikel Harry Thomas
Cuneo Kamand
International Business Machines - Corporation
Patel I B
Schelkopf J. Bruce
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