Computer-aided design and analysis of circuits and semiconductor – Nanotechnology related integrated circuit design
Reexamination Certificate
2000-11-24
2003-04-29
Smith, Matthew (Department: 2825)
Computer-aided design and analysis of circuits and semiconductor
Nanotechnology related integrated circuit design
C716S030000, C716S030000, C361S763000, C361S764000, C361S780000, C174S260000
Reexamination Certificate
active
06557154
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a printed circuit board (hereinafter, simply referred to as PCB) design support system, a PCB design method and a storage medium storing a control program for a same and more particularly to the PCB design support system and PCB design method to reduce emission of unwanted electromagnetic waves caused by variations in voltages between a power plane and a ground plane on a multilayer PCB by controlling voltage variations, and an equivalent circuit model expressed by an equivalent circuit to implement the above system and method.
2. Description of the Related Art
A PCB is generally composed of electronic parts or elements such as ICs (Integrated Circuits), LSIs (Large Scale Integrated Circuits) or a like and of wirings used to connect these electronic parts or elements and is mounted on almost all electronic devices as their core portions. When an electronic circuit on a PCB is operated, a voltage is generated and a current flows, causing an electromagnetic wave to be emitted. As high-speed processing of signals becomes widespread, higher frequencies are increasingly used for circuit operations, which causes emission of unwanted electromagnetic waves in electronic devices, thus creating problems associated with electromagnetic interference in wireless communications, radio, TV or a like in environments surrounding such electronic devices. Therefore, VCCI (Voluntary Control Council for Interference by Information Technology Equipment in Japan) obliges manufacturers of electronic devices to reduce emission of unwanted electromagnetic waves from electronic devices to a controlled level or less.
It is well known that, in a multilayer PCB, a ground plane to provide a reference potential in circuits and a power plane to provide operating power to ICs and/or LSIs are, generally, of a plane structure and the ground plane and power plane function as parallel-plate lines and that variations in voltages between the power plane and ground plane causes emission of unwanted electromagnetic waves (refer to Transaction of the Institute of Electronics, Information and Communication Engineers, Vols. E-80-B, No.11, November 1997, p. 1645-1651). To reduce the emission of unwanted electromagnetic waves caused by variations in voltages between the power plane and ground plane, PCBs having various kinds of structures are introduced and various kinds of methods for designing the PCB are available accordingly.
One example of conventional technology is disclosed in Japanese Patent Application Laid-open No. Hei 11-145569 entitled “Printed Circuit Board and Method for Designing Same”, in which, as shown in
FIGS. 30A and 30B
, a plurality of conductive patterns
102
a
and signal lines
105
a
both extending in a direction of length of a base material
101
are formed on a part-mounting surface of a rectangular and plate-like, base material
101
. On a soldering surface disposed opposite to the part-mounting surface of the base material
101
is formed a plurality of conductive patterns
102
b
and signal lines
105
b
extending in a direction perpendicular to the direction of the length of the base material
101
as shown in FIG.
30
B. The conductive patterns
102
a
and
102
b
are used as a power pattern or a ground pattern. Moreover, separated parts of the conductive patterns
102
a
and
102
b
are connected to each other via a chip-type resistor
104
. By using this chip-type resistor
104
, a decrease in impedance of the conductive patterns
102
a
and
102
b
occurring at a frequency of a standing wave generated from a relationship between a size of the base material
101
and a wavelength of radiation noise is suppressed by loss factor induced by the chip-type resistor
104
, thus resulting in a decrease of a Q value (resonance frequency) in resonance of the standing wave, leading to reduction of emissions of unwanted electromagnetic waves.
Another example of the conventional technology is disclosed in Japanese Patent Application Laid-open No. Hei 11-40905 entitled “Printed Circuit Board and Electronic Device”, in which, as shown in
FIG. 31
, the PCB
110
is composed of a power layer
111
, a ground layer
112
and dielectrics
113
a
and
113
b
disposed between the power layer
111
and the ground layer
112
. There ate mounted two kinds of dielectrics
113
a
and
113
b
each having a different dielectric constant and is configured so that their dielectric constants are in a distributed state on plane faces of the power layer
111
and the ground layer
112
to make resonance weak in a widely distributed state on an axis of frequencies by giving a different resonance condition to each point of the plane face, thus achieving reduction in emissions of strong unwanted electromagnetic waves at a specified frequency.
Moreover, another example of the conventional technology is disclosed in Japanese Patent Application Laid-open No. Hei 10-275981 entitled“Multilayer Printed Circuit Board”, in which, as shown in
FIG. 32
, capacitors
124
adapted to cause high frequency current flowing in a power layer
122
to flow into a ground layer
123
are mounted on edge portions of the power layer
122
and of the ground layer
123
in continuous or discrete positions, thereby achieving reduction of emissions of unwanted electromagnetic waves from the multilayer PCB, having a signal layer
121
, the power layer
122
and the ground layer
123
.
Another example is disclosed in Japanese Patent Application Laid-open No. Hei 6-203102 entitled “Printed Circuit Board Wiring Method”, in which, as shown in
FIG. 33
, each of blocks
132
,
133
, . . . ,
143
are disposed on a multilayer PCB
131
in a manner that digital signals containing much higher frequency components can be sent or received in a straight-line manner in an X or Y direction among these blocks. In this method, therefore, by forbidding cut lines
161
and
162
disposed orthogonal to a direction of wirings to allow digital signals containing much higher frequency components to flow in regions overlapping other regions
151
,
152
or
153
disposed adjacent respectively to a layer having wirings to allow digital signals containing much higher frequency components to flow among blocks mounted on a power layer and a ground layer (not shown), overlap each other, emissions of unwanted electromagnetic waves are reduced.
Furthermore, another example disclosed in the Japanese Patent Application Laid-open No. Hei 10-97560 entitled “Computer Aided Design System”, in which, as shown in
FIG. 34
, by using a tool
171
for evaluation on an arrangement of a bypass condenser incorporated in the CAD (Computer Aided Design) system, parameters associated with a wiring path of the bypass condenser is determined based on information obtained through a substrate data device
174
required for layout of a PCB and then, based on an impedance characteristic calculated from determined parameters, a range of effectiveness that can be provided by the bypass condenser is determined. Parameters associated with the wiring path of the bypass condenser include a wiring length, resistivity, wiring width, wiring thickness or a like. The above tool
171
has a function to display determined range of effectiveness provided by the bypass condenser, which is approximated by an ellipse, on a display device
175
. The CAD system, by using this function, designs the PCB in which emissions of unwanted electromagnetic waves are reduced.
However, each of the above examples of conventional technologies has a problem.
In technology disclosed in the Japanese Patent Application Laid-open No. Hei 11-145569 (FIG.
30
A and FIG.
30
B), though resonance occurring among wirings can be reduced by insertion of the resistor
104
, since a voltage drop occurs due to the insertion of the resistor
104
, it is impossible to reduce resonance in power lines. Therefore, the emissions of unwanted electromagnetic waves caused by variations in voltages between the power plane and the ground plane cannot be fully reduced.
Asao Kiyoshi
Hankui Eiji
Harada Takashi
Sasaki Hideki
NEC Corporation
Rossoshek Helen
Smith Matthew
Young & Thompson
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