Optimized via cutouts with ground references

• US 8,957,325 B2
• Filed: 01/15/2013
• Issued: 02/17/2015
• Est. Priority Date: 01/15/2013
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Hidaka, Yasuo, Thachile, Pradip
• Primary Examiner(s): Norris, Jeremy C
• Application Number:
  US13/742,168
• Publication Number:
  US 20140196941A1
• Time in Patent Office: 763 Days
• Field of Search: 174262-266, 174/255, 361792-795, 29852-853
• US Class Current: 174/262
• CPC Class Codes: G06F 2115/12 Printed circuit boards [PCB] or multi-chip modules [MCM]
• CPC Class Codes: G06F 30/00 Computer-aided design [CAD]
• CPC Class Codes: G06F 30/394 Routing G06F30/396 takes precedence
• CPC Class Codes: H05K 1/0225 Single or multiple openings in a shielding, ground or power plane H05K1/0227 takes precedence
• CPC Class Codes: H05K 1/0245 Lay-out of balanced signal pairs, e.g. differential lines or twisted lines
• CPC Class Codes: H05K 1/0251 related to vias or transitions between vias and transmission lines
• CPC Class Codes: H05K 1/0253 Impedance adaptations of transmission lines by special lay-out of power planes, e.g. providing openings H05K1/0251 takes precedence
• CPC Class Codes: H05K 1/116 Lands, clearance holes or other lay-out details concerning the surrounding of a via
• CPC Class Codes: H05K 2201/09718 Clearance holes
• CPC Class Codes: H05K 2201/09727 Varying width along a single conductor; Conductors or pads having different widths
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base

Abstract

The present disclosure relates to a method of optimizing via cutouts, including selecting a geometry of a via cutout on a first ground reference layer adjacent to a first differential trace, the geometry selected to provide an extension region extending in the direction of the first differential trace. Additionally, the method includes the steps of selecting a geometry of the first differential trace, wherein a spacing of the first differential trace in the extension region is different from a spacing of the first differential trace outside the extension region, and selecting a radial dimension of a first and second via cutout on a second ground reference layer adjacent to and between the first and second differential traces, the radial dimension of the first via cutout and the second via cutout selected such that the second ground reference layer remains intact in the area adjacent the second differential trace.

Claims

1. A printed circuit board comprising:

a first ground reference layer;

a second ground reference layer;

a via cutout on the first ground reference layer, the geometry of the via cutout selected to provide an extension region extending in the direction of a differential trace,

a first differential trace, the first differential trace adjacent a first ground reference layer and a second ground reference layer, wherein a spacing of the first differential trace in the extension region is different from a spacing of the first differential trace outside the extension region;

a second differential trace;

the second differential trace adjacent the second ground reference layer; and

a first via cutout and a second via cutout on the second ground reference layer, a radial dimension of the first via cutout and the second via cutout selected such that the second ground reference layer remains intact in the area adjacent the second differential trace.

2. The printed circuit board of claim 1, wherein the spacing of the first differential trace in the extension region is greater than the spacing of the first differential trace outside the extension region.

3. The printed circuit board of claim 1, wherein a width of the first differential trace in the extension region is narrower than a width of the first differential trace outside the extension region.

4. The printed circuit board of claim 1, wherein the extension region is rectangular.

5. The printed circuit board of claim 1, further comprising:

a third differential trace;

a third ground reference layer adjacent to and between the second differential trace and the third differential trace,

a first via cutout and a second via cutout on the third ground reference layer, a radial dimension of the first via cutout and the second via cutout selected such that the third ground reference layer remains intact in the area adjacent the third differential trace.

6. The printed circuit board of claim 1, further comprising:

a third ground reference layer adjacent to the second differential trace, but not between the second differential trace and a third differential trace;

a via cutout on the third ground reference layer, the geometry of the via cutout selected to provide an extension region extending in the direction of the second differential trace; and

wherein a spacing of the second differential trace in the extension region is different from a spacing of the second differential trace outside the extension region.

7. The printed circuit board of claim 6, wherein the spacing of the second differential trace in the extension region is greater than the spacing of the second differential trace outside the extension region.

8. The printed circuit board of claim 6, wherein a width of the second differential trace in the extension region is narrower than a width of the second differential trace outside the extension region.

9. The printed circuit board of claim 6, wherein the extension region is rectangular.

10. A method of optimizing via cutouts, comprising:

selecting a geometry of a via cutout on a first ground reference layer adjacent to a first differential trace, the geometry of the via cutout selected to provide an extension region extending in the direction of the first differential trace;

selecting a geometry of the first differential trace, wherein a spacing of the first differential trace in the extension region is different from a spacing of the first differential trace outside the extension region; and

selecting a radial dimension of a first via cutout and a second via cutout on a second ground reference layer adjacent to and between the first differential trace and a second differential trace, the radial dimension of the first via cutout and the second via cutout selected such that the second ground reference layer remains intact in the area adjacent the second differential trace.

11. The method of claim 10, wherein the spacing of the first differential trace in the extension region is greater than the spacing of the first differential trace outside the extension region.

12. The method of claim 10, wherein a width of the first differential trace in the extension region is narrower than a width of the first differential trace outside the extension region.

13. The method of claim 10, wherein the extension region is rectangular.

14. The method of claim 10, further comprising:

if there is a third ground reference layer adjacent to and between the second differential trace and a third differential trace, selecting a radial dimension of a first via cutout and a second via cutout on the third ground reference layer;

wherein the radial dimension of the first via cutout and the second via cutout is selected such that the third ground reference layer remains intact in the area adjacent the third differential trace.

15. The method of claim 10, further comprising:

if there is a third ground reference layer adjacent to the second differential trace, but not between the second differential trace and a third differential trace;

selecting a geometry of a via cutout on the third ground reference layer, the geometry of the via cutout selected to provide an extension region extending in the direction of the second differential trace; and

selecting a geometry of the second differential trace, wherein a spacing of the second differential trace in the extension region is different from a spacing of the second differential trace outside the extension region.

16. The method of claim 15, wherein the spacing of the second differential trace in the extension region is greater than the spacing of the second differential trace outside the extension region.

17. The method of claim 15, wherein a width of the second differential trace in the extension region is narrower than a width of the second differential trace outside the extension region.

18. The method of claim 15, wherein the extension region is rectangular.