Structure for improved capacitance and inductance calculation

• US 6,282,692 B1
• Filed: 12/03/1998
• Issued: 08/28/2001
• Est. Priority Date: 12/03/1998
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Rubin, Barry J.
• Primary Examiner(s): Smith, Matthew
• Assistant Examiner(s): Kik, Phallaka
• Application Number:
  US09/204,687
• Time in Patent Office: 999 Days
• Field of Search: 716/1-21
• US Class Current: 716/115
• CPC Class Codes: G06F 30/367 Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods

Abstract

A methodology and circuit modeling structure for analyzing the packaging of electrical circuits and determining electrical circuit properties, e.g., inductance, capacitance, of circuits and circuit structures found in VLSI chips, PC cards, boards, microwave circuits, etc. The methodology and circuit modeling structure includes modifying the original signal line structure in the circuit to be analyzed by including a shadow line structure in the analyzed circuit and locating the shadow line structure between a ground plane structure and an associated signal line structure at an infinitesimal distance above the ground plane. Additionally, for each shadow line structure, there is provided a first via structure for connecting a first end of said shadow line to the ground plane and, a second via structure connecting a second end of the shadow line to the ground plane. The modified shadow line structure is readily implemented in 3D circuit package analysis programs and provides a computationally efficient way to analyze complex types electrical/electronic/packaging circuits and structures.

Claims

1. A method for calculating electrical circuit parameters in a circuit to be analyzed, said circuit including a signal line structure capable of carrying current and a ground plane having a return current, said method including:

locating one or more signal line structures each for carrying current near a ground plane, said signal line structures located a height h relative to said ground plane;

associating one or more shadow line structures with each signal line structure and locating said one or more shadow line structures to run in parallel with said signal line structure between said ground plane and its associated signal line structure;

providing for each shadow line structure a first via structure for connecting a first end of said shadow line structure to said ground plane and, a second via structure connecting a second end of said shadow line structure to said ground plane, said associated shadow line structure and respective first and second vias permitting a re-distribution of said return current between said ground plane and said shadow line structure in a subsequent electrical circuit parameter calculation performed by a circuit analysis program, said return current substantially comprised within said shadow line structure;

inputting said ground plane, signal line structure, shadow line structure, respective first and second via structures and re-distributed return current into said circuit analysis program for performing said electrical circuit parameter calculation for a portion of said circuit comprising said signal line structure and said ground plane;

wherein said electrical circuit parameter is calculated with improved accuracy due to the return current being re-distributed to said shadow line structure.

2. The method as claimed in claim 1, wherein said signal line structure is situated at an angle relative to said ground plane.

3. The method as claimed in claim 1, wherein said shadow line structure is located an infinitesimal distance above or below said ground plane structure.

4. The method of claim 1, wherein a height h of said signal line structure above said ground plane determines a width of its corresponding shadow line structure.

5. The method as claimed in claim 1, wherein said first and second via structures have a length running orthogonal to said ground plane.

6. The method as claimed in claim 5, wherein said signal line structure is a conductor having width and length dimensions, each shadow line structure being a conductor having the same width as said signal line structure and having infinitesimal thickness.

7. The method as claimed in claim 5, wherein each shadow line structure is a conductor having a different width than that of said corresponding signal line structure and having infinitesimal thickness.

8. The method as claimed in claim 5, wherein an electrical parameter calculation includes an inductance calculation of said signal line structure.

9. The method as claimed in claim 8, wherein said analysis program includes technique for partitioning said ground plane into a rectangular grid, each rectangle of said grid having orthogonal current distributions used in calculation of said return current in said ground plane.

10. The method as claimed in claim 1, wherein said electrical parameter calculation includes a capacitance calculation of said signal line structure, said shadow line structure including a via structure connecting one end of said shadow line structure to said ground plane structure.

11. The method as claimed in claim 1, wherein said ground plane has a thickness and includes top and bottom surfaces, said associating step including associating two shadow line structures for a signal line structure, a first shadow line structure being located above a top surface of said ground plane and below said signal line structure, and a second shadow line structure being located below a bottom surface of said ground plane running parallel to said signal line structure, each first and second shadow line structure having respective via structures at corresponding first and second ends for connecting to said ground plane.

12. The method as claimed in claim 1, wherein said ground plane includes an aperture resulting in two conductive ground plane regions, said associating step including locating a first shadow line structure over a first conductive region of said ground plane, and locating a second shadow line structure over a second conductive region of said ground plane.

13. The method as claimed in claim 1, wherein said signal line structure includes two or more non-intersecting signal lines situated diagonally with respect to said ground plane and crossing each other, said method including associating one or more shadow line structures for each signal line structure at different heights in a manner so that said shadow structures do not intersect.

14. The method as claimed in claim 1, wherein said signal line structure includes two or more conductors situated diagonally with respect to said ground plane and intersecting each other, said method including associating one or more shadow line structures for each conductor at different heights, and providing a via for each shadow line structure at a location corresponding to the intersection of said conductors.

15. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps for calculating electrical circuit parameters in a circuit device to be analyzed, said circuit device including a signal line structure capable of carrying current and a ground plane having a return current, said method steps comprising:

locating one or more signal line structures each for carrying current near a ground plane and located a height h relative to said ground plane;

associating one or more shadow line structures with each signal line structure and locating said one or more shadow line structures to run in parallel with said signal line structure between said ground plane and its associated signal line structure;

providing, for each shadow line structure, a first via structure for connecting a first end of said shadow line structure to said ground plane and, a second via structure connecting a second end of said shadow line structure to said ground plane, said associated shadow line structure and respective first and second vias permitting a re-distribution of said return current between said ground plane and said shadow line structure in a subsequent electrical circuit parameter calculation performed by a circuit analysis program, said return current substantially comprised within said shadow line structure;

inputting said ground plane, signal line structure, shadow line structure, respective first and second via structures and re-distributed return current into said circuit analysis program for performing said electrical circuit parameter calculation for a portion of said circuit comprising said signal line structure and said ground plane;

wherein said electrical circuit parameter is calculated with improved accuracy due to the return current being re-distributed to said shadow line structure.

16. The program storage device readable by a machine as claimed in claim 15, wherein said signal line structure is situated at an angle relative to said ground plane.

17. The program storage device readable by a machine as claimed in claim 15, wherein said shadow line structure is located an infinitesimal distance above or below said ground plane.

18. The program storage device readable by a machine as claimed in claim 15, wherein a height h of said signal line structure above said ground plane determines a width of its corresponding shadow line structure.

19. The program storage device readable by a machine as claimed in claim 15, wherein said first and second via structures have a length running orthogonal to said ground plane.

20. The program storage device readable by a machine as claimed in claim 19, wherein said signal line structure is a conductor having width and length dimensions, each shadow line structure is a conductor having the same width as said signal line structure and having infinitesimal thickness.

21. The program storage device readable by a machine as claimed in claim 19, wherein each shadow line structure is a conductor having a different width than that of said corresponding signal line structure and having infinitesimal thickness.

22. The program storage device readable by a machine as claimed in claim 19, wherein said electrical parameter calculation includes an inductance calculation of said signal line structure.

23. The program storage device readable by a machine as claimed in claim 22, wherein said analysis program includes technique for partitioning ground plane into rectangular grid, each rectangle of said grid having orthogonal current distributions used in calculation of return current distribution in said ground plane.

24. The program storage device readable by a machine as claimed in claim 19, wherein said electrical parameter calculation includes a capacitance calculation of said signal line structure, said shadow line structure including a via structure connecting one end of said shadow line structure to said ground plane structure.

25. The program storage device readable by a machine as claimed in claim 19, wherein said ground plane has a thickness and includes top and bottom surfaces, said associating step including associating two shadow line structures for a signal line structure, a first shadow line structure being located above a top surface of said ground plane and below said signal line structure, and a second shadow line structure being located below a bottom surface of said ground plane running parallel to said signal line structure, each first and second shadow line structure having respective first and second ends, each first and second shadow line structure having first and second via structures at respective first and second ends for connecting to said ground plane.

26. The program storage device readable by a machine as claimed in claim 19, wherein said ground plane includes an aperture resulting in two conductive ground plane regions, said associating step including locating a first shadow line structure over a first conductive region of said ground plane, and locating a second shadow line structure over a second conductive region of said ground plane.

27. The program storage device readable by a machine as claimed in claim 19, wherein said signal line structure includes two or more non-intersecting signal lines situated diagonally with respect to said ground plane and crossing each other, said method steps including associating one or more shadow line structures for each signal line structure at different heights in a manner so that said shadow line structures do not intersect.

28. The program storage device readable by a machine as claimed in claim 19, wherein said signal line structure includes two or more conductors situated diagonally with respect to said ground plane and intersecting each other, said method steps including associating one or more shadow line structures for each conductor at different heights, and providing a via for each shadow line structure at a location corresponding to the intersection of said conductors.