Patent Application
20070044062
The present invention relates to wiring design of a printed board, more specifically, to a method for checking a return path of a printed board and a CAD (computer aided design) apparatus for designing patterns of a printed board, which can take an EMC (electromagnetic compatibility) countermeasure for preventing unwanted emission noise from being generating out of a printed board
In order to reduce unwanted emission noise from electronics, such as digital audio-visual equipment or information equipment, it is important to figure out a wiring path in a circuit board which may constitute a noise source. In a conventional CAD for a printed board, when detecting a wiring error, a person visually checked whether a wiring path of clock wiring pattern violates EMC design condition to correct the violated point of the wiring path.
However, in the above-mentioned CAD for a printed board, since detection of error in EMC design depends on a person, there is a problem that leakage of detection is likely to occur and it takes much time to detect a error.
For this countermeasure, since recognition technology of pattern shapes is developed in CAD for a printed board, it is possible to detect a guard ground, that is a guard pattern with ground attribution, existing adjacent to a signal wiring. For a typical detection method, if there is a wiring section in which a guard ground does not exist within a defined guard ground discriminant value with respect to a signal wiring, an error is thought to occur.
A related prior art will be listed as follow.
However, in the above-mentioned method for detecting a guard ground, as shown in
To solve the above problem, it is an object of the present invention to provide a method for checking a return path of a printed board and a CAD apparatus for designing patterns of a printed board, which can check a return path without mistake more quickly than the conventional method.
To attain the above object, a method for checking a return path of a printed board, according to the present invention, includes steps of:
detecting a signal wiring pattern with reference to wiring information of the printed board;
tracing the signal wiring pattern along the longitudinal direction thereof, to detect whether or not a guard ground exists within a distance from the signal wiring pattern to a predetermined first discriminant value GL;
identifying a non-guard ground section in which no guard ground exists within the distance to the first discriminant value GL;
setting up a second discriminant value GU larger than the first discriminant value GL;
detecting whether or not a guard ground exists within another distance from the signal wiring pattern to the second discriminant value GU in the non-guard ground section; and
judging an error of guard ground when no guard ground exists within the distance to the second discriminant value GU in the non-guard ground section.
It is preferable in the checking method according to the present invention to include a step of judging an error of guard ground when a discontinued guard ground exists within the distance to the second discriminant value GU in the non-guard ground section.
It is preferable in the checking method according to the present invention to include a step of judging an error of guard ground when satisfying a relation: L≦2(GU2-G2)1/2 wherein L is a length of the non-guard ground section, and G is a distance from the signal wiring pattern on the border of the non-guard ground section to the guard ground.
It is preferable in the checking method according to the present invention that the printed board is a multilayer printed board including a wiring layer in which the signal wiring pattern resides, and a ground layer in which a ground plane resides, and the method further includes a step of judging an error of guard ground when no guard ground exists within the distance to the second discriminant value GU in the non-guard ground section and no ground, which is connected to the guard ground, exists in the ground layer.
It is preferable in the checking method according to the present invention that the first discriminant value GL is defined as a shortest distance between lines during pattern design of the printed board.
The above-mentioned checking method can be realized as a program executable on a computer, and the program can be recorded in a recording media.
Moreover, a CAD apparatus for designing patterns of a printed board, according to the present invention, includes:
a signal wiring pattern detecting unit for detecting a signal wiring pattern with reference to wiring information of the printed board;
a guard ground detecting unit for tracing the signal wiring pattern along the longitudinal direction thereof, to detect whether or not a guard ground exists within a distance from the signal wiring pattern to a predetermined first discriminant value GL, and for identifying a non-guard ground section in which no guard ground exists within the distance to the first discriminant value GL, and for detecting whether or not a guard ground exists within another distance from the signal wiring pattern to a second discriminant value GU, which is larger than the first discriminant value GL, in the non-guard ground section; and
a return path judging unit for judging an error of guard ground when no guard ground exists within the distance to the second discriminant value GU in the non-guard ground section.
According to this approach, it is possible to check quickly both of a splay portion and a short discontinued portion of the guard ground without mistake. Consequently, an EMC countermeasure for suppressing an electromagnetic wave generated from a high frequency current loop, which is configured of the signal wiring and the guard ground, can be effectively adopted.
11: INPUT AND OUTPUT DEVICE
12: COMPUTER FOR DESIGN OF CIRCUIT PATTERNS
13: STORAGE DEVICE
14: PRINTED BOARD CAD PROGRAM FOR DESIGN OF CIRCUIT PATTERNS
21: GUARD GROUND DETECTING MEANS
22: SIGNAL WIRING PATTERN DETECTING UNIT
23: GUARD GROUND DETECTING UNIT
24: PLANE GROUND DETECTING UNIT
25: RETURN PATH JUDGING UNIT
31: SIGNAL WIRING PATTERN
32: GUARD GROUND
34: GUARD GROUND OK SECTION
35: GUARD GROUND NG SECTION
35
a: GUARD GROUND NG SECTION A
35
b: GUARD GROUND NG SECTION B
36
a: GUARD GROUND TERMINAL X
36
b: GUARD GROUND TERMINAL Y
37: CENTER LINE BETWEEN X AND Y
38: IC
39: GROUND PLANE
40: ADJACENT GROUND PLANE
41: VIA HOLE
42: RETURN PATH
43: SPLAY PORTION OF GUARD GROUND
44: DISCONTINUED PORTION OF GUARD GROUND
45: SEMICIRCLE OF RADIAL DISCRIMINANT VALUE
51: WIRING LAYER
52: GROUND LAYER
First, in
The guard ground detecting means 21 includes a signal wiring pattern detecting unit 22, a guard ground detecting unit 23, a plane ground detecting unit 24, and a return path judging unit 25.
The signal wiring pattern detecting unit 22 detects each of signal wiring patterns with reference to wiring information of the printed board to be designed. This wiring information is stored as design data of the printed board in the storage device 13.
The guard ground detecting unit 23 traces each of the signal wiring patterns, which are detected by the signal wiring pattern detecting unit 22, along the longitudinal direction thereof, to detect whether or not a guard ground, which functions as return path of the particular signal wiring pattern, exists on both sides of the signal wiring pattern. At this time, a first guard ground discriminant value GL for defining a search range is set up in advance, and existence of such a guard ground is detected within a distance from a center line of the signal wiring pattern to the first guard ground discriminant value GL.
And then, the guard ground detecting unit 23 identifies a section in which a guard ground exists within the distance to the first guard ground discriminant value GL, and another section in which no guard ground exists within the distance to the first guard ground discriminant value GL, to define the former as a guard ground OK section and the latter as a guard ground NG section, respectively. And then, in order to expand more the search range in the guard ground NG section, a second guard ground discriminant value GU, which is larger than the first guard ground discriminant value GL, is set up in advance. Existence of the guard ground is detected within another distance from a center line of the signal wiring pattern to the second guard ground discriminant value GU.
The return path judging unit 25 judges an error of guard ground when no guard ground exists within the distance to the second guard ground discriminant value GU in the guard ground NG section. Result of such error judgment may be represented to an operator through the input and output device 11, such as display, or be informed to another program.
Incidentally, in a case the printed board to designed is a multilayer printed board including a wiring layer in which the signal wiring pattern resides, and a ground layer in which a ground plane resides, there is a possibility that the return path of the signal wiring pattern is formed in the ground plane of the ground layer through a via hole or the like. Therefore, when the guard ground is discontinued in the wiring layer, the plane ground detecting unit 24 detects whether or not a ground, which is connected to the guard ground, exists in the ground layer.
Next, the flowchart shown in
Next, in a step a2, the first guard ground discriminant value GL is set up. The first guard ground discriminant value GL defines, as shown in
Next, in a step a3, the guard ground detecting unit 23 traces the signal wiring pattern along the longitudinal direction thereof, and then in a step a4, to detect whether or not a guard ground exists within the distance from the signal wiring pattern to the first guard ground discriminant value GL. When a guard ground exists within the distance to the first guard ground discriminant value GL throughout the traced section, the return path of the particular signal wiring pattern is meant to be secured. Transferring to a step a5, the return path judging unit 25 judges no error of guard ground to complete the return path checking routine.
Meanwhile, in a case there is a section in which no guard ground exists within the distance to the first guard ground discriminant value GL, and then transferring to a step a10, the guard ground detecting unit 23 defines the section in which the guard ground exists within the distance to the first guard ground discriminant value GL as a guard ground OK section, and the section in which no guard ground exists within the distance to the first guard ground discriminant value GL as a guard ground NG section, respectively.
For example, as shown in
Next, in steps a11 and a12, the second guard ground discriminant value GU is set up as larger than the first guard ground discriminant value GL. The second guard ground discriminant value GU is preferably set up, as shown in
Next, in a step a13, the guard ground detecting unit 23 re-traces it in a range of the guard ground NG section to detect whether or not the guard ground exists within the distance to the second guard ground discriminant value GU. When there is a section in which no guard ground exists within the distance to the second guard ground discriminant value GU in the guard ground NG section, transferring to a step a15, the return path judging unit 25 judges an error of guard ground, and then displaying it for an operator by means of the input and output device 11 to complete the return path checking routine.
Meanwhile, in the step a13, when the guard ground exists within the distance to the second guard ground discriminant value GU in the guard ground NG section, transferring to a step a14, it is detected whether the guard ground is continuous or not in the guard ground NG section. When the guard ground is continuous, the return path of the particular signal wiring pattern is meant to be secured. Transferring to the step a5, the return path judging unit 25 judges no error of guard ground to complete the return path checking routine.
Meanwhile, in the step a14, if the guard ground is discontinuous in the guard ground NG section, the return path of the particular signal wiring pattern is meant to be lost. Transferring to the step a15, the return path judging unit 25 judges an error of guard ground, and then displaying it for an operator by means of the input and output device 11 to complete the return path checking routine.
For example, as shown in
As described above, continuity of the guard ground is judged by employing the two larger and smaller guard ground discriminant values GL and GU, thereby reliably checking the return path of the signal wiring pattern.
Incidentally, the first embodiment exemplifies a case where the second guard ground discriminant value GU is set up based on a length of the guard ground NG section. But the second guard ground discriminant value GU may be set up based on a signal frequency or a signal current flowing in the signal wiring pattern, resulting in a similar effect.
In this embodiment, in a step b14 shown in
In a step b1 of
Next, in a step b2, the first guard ground discriminant value GL is set up. The first guard ground discriminant value GL defines, as shown in
Next, in a step b3, the guard ground detecting unit 23 traces the signal wiring pattern along the longitudinal direction thereof, and then in a step b4, to detect whether or not a guard ground exists within the distance from the signal wiring pattern to the first guard ground discriminant value GL. When a guard ground exists within the distance to the first guard ground discriminant value GL throughout the traced section, the return path of the particular signal wiring pattern is meant to be secured. Transferring to a step b5, the return path judging unit 25 judges no error of guard ground to complete the return path checking routine.
Meanwhile, in a case there is a section in which no guard ground exists within the distance to the first guard ground discriminant value GL, and then transferring to a step b10, the guard ground detecting unit 23 defines the section in which the guard ground exists within the distance to the first guard ground discriminant value GL as a guard ground OK section, and the section in which no guard ground exists within the distance to the first guard ground discriminant value GL as a guard ground NG section, respectively.
For example, as shown in
Next, in steps b11 and b12, the second guard ground discriminant value GU is set up as larger than the first guard ground discriminant value GL. The second guard ground discriminant value GU is preferably set up, as shown in
Next, in a step b13, the guard ground detecting unit 23 re-traces it in a range of the guard ground NG section to detect whether or not the guard ground exists within the distance to the second guard ground discriminant value GU. When there is a section in which no guard ground exists within the distance to the second guard ground discriminant value GU in the guard ground NG section, transferring to a step b15, the return path judging unit 25 judges an error of guard ground, and then displaying it for an operator by means of the input and output device 11 to complete the return path checking routine.
Meanwhile, in the step b13, when the guard ground exists within the distance to the second guard ground discriminant value GU in the guard ground NG section, transferring to the step b14, as shown in
Meanwhile, in the step b14, when L>2(GU2-G2)1/2 is satisfied, transferring to the step b5, the return path judging unit 25 judges no error of guard ground to complete the return path checking routine.
As described above, both employment of the two larger and smaller guard ground discriminant values GL and GU, and numerical comparison of the length L of the guard ground NG section with the distance G from the signal wiring pattern on the border of the guard ground NG section to the guard ground facilitate reliable checking of the return path of the signal wiring pattern.
In a case the printed board to designed is a multilayer printed board including a wiring layer in which the signal wiring pattern resides, and a ground layer in which a ground plane resides, there is a possibility that the return path of the signal wiring pattern is formed in the ground plane of the ground layer through a via hole or the like.
In this embodiment, when the guard ground residing in the wiring layer is discontinuous, the plane ground detecting unit 24 detects whether or not the ground which is connected with the guard ground exists in the ground layer.
Firstly, in a step cl of
Next, in a step c2, the first guard ground discriminant value GL is set up. The first guard ground discriminant value GL defines, as shown in
Next, in a step c3, a plane ground discriminant value GPG is set up. The plane ground discriminant value GPG defines, as shown in
Next, in a step c4, the plane ground detecting unit 24 extracts a plane ground which exists in a range from the wiring layer, in which the particular signal wiring pattern resides, to the plane ground discriminant value GPG.
Next, in a step c5, the guard ground detecting unit 23 traces the signal wiring pattern along the longitudinal direction thereof, and then in a step c6, to detect whether or not a guard ground exists within the distance from the signal wiring pattern to the first guard ground discriminant value GL. When a guard ground exists within the distance to the first guard ground discriminant value GL throughout the traced section, the return path of the particular signal wiring pattern is meant to be secured. Transferring to a step c7, the return path judging unit 25 judges no error of guard ground to complete the return path checking routine.
Meanwhile, in a case there is a section in which no guard ground exists within the distance to the first guard ground discriminant value GL, and then transferring to a step c10, the guard ground detecting unit 23 defines the section in which the guard ground exists within the distance to the first guard ground discriminant value GL as a guard ground OK section, and the section in which no guard ground exists within the distance to the first guard ground discriminant value GL as a guard ground NG section, respectively.
As shown in
Next, in steps c11 and c12, the second guard ground discriminant value GU is set up as larger than the first guard ground discriminant value GL. The second guard ground discriminant value GU is preferably set up, as shown in
Next, in a step c13, the guard ground detecting unit 23 re-traces it in a range of the guard ground NG section to detect whether or not the guard ground exists within the distance to the second guard ground discriminant value GU. When there is a section in which no guard ground exists within the distance to the second guard ground discriminant value GU in the guard ground NG section, the process is transferred to a step c15.
Meanwhile, in the step c13, when the guard ground exists within the distance to the second guard ground discriminant value GU in the guard ground NG section, transferring to a step c14, it is judged whether or not the guard ground is continuous in the guard ground NG section. When the guard ground is continuous, the return path of the particular signal wiring pattern is meant to be secured. Transferring to a step c7, the return path judging unit 25 judges no error of guard ground to complete the return path checking routine.
Meanwhile, in the step c14, when the guard ground is discontinuous in the guard ground NG section, the return path of the particular signal wiring pattern is meant to be lost. The process is transferred to the step c15.
In the step c15, the plane ground detecting unit 24 searches for a plane ground extracted in the step c4 to detect whether or not the plane ground which is connected with the guard ground exists in the ground layer. When the above plane ground exists, the return path of the particular signal wiring pattern is meant to be secured. Transferring to the step c7, the return path judging unit 25 judges no error of guard ground to complete the return path checking routine.
For example, as shown in
Meanwhile, in the step c15, when no plane ground which is connected with the guard ground exists, transferring to a step c16, the return path judging unit 25 judges an error of guard ground, and then displaying it for an operator by means of the input and output device 11 to complete the return path checking routine.
As described above, both employment of the two larger and smaller guard ground discriminant values GL and GU, and judgment of continuity of the guard ground by taking account of the plane ground residing in another layer facilitate reliable checking of the return path of the signal wiring pattern.
By employing the method for checking a return path of a printed board and the CAD apparatus for designing patterns of a printed board according to the present invention, it is possible to check quickly both of a splay portion and a short discontinued portion of the guard ground without mistake. Consequently, an EMC countermeasure for suppressing an electromagnetic wave generated from a high frequency current loop, which is configured of the signal wiring and the guard ground, can be effectively adopted.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-029049 | Feb 2004 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP05/01593 | 2/3/2005 | WO | 11/7/2005 |
