Differential transmission line wiring structure of circuit board

Abstract

The utility model relates to a differential transmission line wiring structure of a circuit board, the circuit board comprises a circuit layer, the circuit layer comprises a BGA area, a non-BGA area and two differential transmission lines which are oppositely arranged and extend from the BGA area to the non-BGA area, the BGA area comprises a plurality of through holes, wire clamping areas located between every two adjacent through holes and non-wire clamping areas located between every two adjacent wire clamping areas, and the differential transmission lines comprise a first differential transmission line located in the BGA area and a second differential transmission line located in the non-BGA area. The first differential transmission line comprises a narrow line located in the line clamping area and a wide line located in the non-line clamping area, and the line width of the narrow line is smaller than that of the wide line. According to the differential transmission line wiring structure of the circuit board, the problem that the impedance of the differential transmission line in the BGA area of the circuit board cannot meet the requirement and the high-speed signal transmission is influenced can be effectively avoided.

Description

Technical Field

[0001] This utility model relates to the field of circuit board technology, and in particular to a differential transmission line wiring structure for a circuit board. Background Technology

[0002] BGA (Ball Grid Assay) technology is increasingly widely used in chip packaging due to its excellent electrical performance, high I / O pin count, and small package size, gradually becoming the mainstream packaging form in high-end devices and high-density packaging fields. With the rapid development of the electronic communication industry, high-speed circuit boards are moving towards integration and high speed, which means higher requirements for the signal integrity (SI) performance of high-speed signals, and further increases the requirements for transmission lines. High-speed circuit boards often use differential transmission lines for signal transmission to improve their anti-interference capabilities. In existing technologies, differential transmission lines on high-speed circuit boards generally use the same linewidth design in both BGA and non-BGA areas. However, the smaller spacing of the vias in the pin array of the BGA area makes it impossible to achieve the same linewidth for differential transmission lines in both areas. Therefore, the linewidth of differential transmission lines in the BGA area needs to be reduced. This reduction in linewidth leads to a significant increase in impedance, which fails to meet the requirements and affects high-speed signal transmission. Utility Model Content

[0003] To address the aforementioned problems, the purpose of this invention is to design a differential transmission line wiring structure for a circuit board that can effectively prevent the differential transmission line impedance in the BGA area of ​​the circuit board from failing to meet requirements and affecting high-speed signal transmission.

[0004] The objective of this utility model is achieved through the following technical solution:

[0005] Design a differential transmission line routing structure for a circuit board. The circuit board includes a circuit layer, which includes a BGA region, a non-BGA region, and two differential transmission lines that are oppositely arranged and extend from the BGA region to the non-BGA region. The BGA region includes a plurality of vias, a clamping area between two adjacent vias, and a non-clamping area between two adjacent clamping areas. The differential transmission line includes a first differential transmission line located in the BGA region and a second differential transmission line located in the non-BGA region. The first differential transmission line includes a narrow line located in the clamping area and a wide line located in the non-clamping area, wherein the line width of the narrow line is smaller than the line width of the wide line.

[0006] This solution's differential transmission line routing structure achieves a balance between high-density routing and signal integrity in the BGA area of ​​the circuit board through zoned linewidth adjustment. In the limited routing space within the clamping area between adjacent vias in the BGA area, the impact of the high-density via layout is offset by reducing the linewidth (narrow lines). Narrow linewidths reduce parasitic capacitance effects between vias and prevent impedance abrupt changes due to excessive linewidth, thus maintaining impedance continuity of the differential pair. Simultaneously, for the dense via layout of the BGA solder ball array, the narrow line design in the clamping area avoids the risk of short circuits between the lines and vias. In the non-clamping area of ​​the BGA area, where routing space is more ample, a wider linewidth is restored to compensate for the losses of narrower segments. In non-BGA areas, the second differential transmission line can use a standard wide linewidth, reducing transmission loss and simplifying impedance matching design, suitable for long-distance routing. This design effectively solves the problem of insufficient impedance of differential transmission lines in the BGA area of ​​the circuit board, affecting high-speed signal transmission.

[0007] Furthermore, the two first differential transmission lines are located between the same two vias.

[0008] Two first differential transmission lines are located between the same two vias, sharing parasitic parameters between the vias, such as inter-via capacitance. By synchronously adjusting the line width and spacing, an equivalent LC resonant compensation structure is formed, reducing impedance abrupt changes between vias. Compared to two first differential transmission lines located between different vias, the influence of vias on signal transmission can be effectively avoided.

[0009] Furthermore, the two first differential transmission lines are axially symmetrical about the lines of symmetry of the two vias.

[0010] The two first differential transmission lines are located between the same two vias. The geometric consistency of the signal transmission path can be ensured by symmetrical design in the BGA area, that is, by making the two narrow lines and the wide line completely mirrored.

[0011] Furthermore, the line spacing between the two narrow lines is not less than the first line spacing threshold.

[0012] The first line spacing threshold is the minimum line spacing processing capability of two differential transmission lines in the BGA area, to avoid problems such as short circuits and high processing defect rates caused by excessively small line spacing between two narrow lines.

[0013] Furthermore, the spacing between the two narrow lines is less than or equal to the spacing between the two wide lines.

[0014] In the BGA region, the non-clipped area has ample routing space. While increasing the line width, the spacing between two wide lines can also be increased. By enhancing the coupling between differential pairs, the inductance increase caused by the reduction in line width can be compensated, and the odd-mode impedance can be kept constant.

[0015] Furthermore, the line spacing between the two second differential transmission lines is not less than the second line spacing threshold.

[0016] The second line spacing threshold is the optimal design line spacing for two differential transmission lines in the non-BGA area. By adjusting the line width and line spacing of the two second differential transmission lines, the stability of high-speed signal transmission is ensured, while avoiding problems such as short circuits and high manufacturing defect rates caused by excessively small line spacing between the two second differential transmission lines.

[0017] Furthermore, the spacing between the two second differential transmission lines is greater than the spacing between the two narrow lines.

[0018] In non-BGA areas, while meeting the differential impedance requirements of the circuit board, the width and spacing of the two second differential transmission lines should be maximized to improve the signal transmission performance of the circuit board.

[0019] Furthermore, the differential transmission line also includes a connecting line that is angled and connects the first differential transmission line and the second differential transmission line.

[0020] The spacing between the two first differential transmission lines is smaller than that between the two second differential transmission lines. They are connected by a slanted and gradually wide connecting line with a slant angle between 125° and 165°, forming a gradually varying impedance structure to reduce signal loss.

[0021] Compared with the prior art, the beneficial effects of this utility model are:

[0022] This solution's differential transmission line routing structure achieves a balance between high-density routing and signal integrity in the BGA area of ​​the circuit board through zoned linewidth adjustment. In the limited routing space within the clamping area between adjacent vias in the BGA area, the impact of the high-density via layout is offset by reducing the linewidth (narrow lines). Narrow linewidths reduce parasitic capacitance effects between vias and prevent impedance abrupt changes due to excessive linewidth, thus maintaining impedance continuity of the differential pair. Simultaneously, for the dense via layout of the BGA solder ball array, the narrow line design in the clamping area avoids the risk of short circuits between the lines and vias. In the non-clamping area of ​​the BGA area, where routing space is more ample, a wider linewidth is restored to compensate for the losses of narrower segments. In non-BGA areas, the second differential transmission line can use a standard wide linewidth, reducing transmission loss and simplifying impedance matching design, suitable for long-distance routing. This design effectively solves the problem of insufficient impedance of differential transmission lines in the BGA area of ​​the circuit board, affecting high-speed signal transmission. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a differential transmission line wiring structure according to an embodiment of the present invention. Figure 1 .

[0024] Figure 2 This is a schematic diagram of a differential transmission line wiring structure according to an embodiment of the present invention. Figure 2.

[0025] Diagram description: 1. Line layer; 2. BGA area; 21. Via; 22. Trace area; 23. Non-trace area; 3. Non-BGA area; 4. Differential transmission line; 41. First differential transmission line; 411. Narrow line; 412. Wide line; 42. Second differential transmission line; 43. Connector. Detailed Implementation

[0026] To facilitate understanding of this invention, a more comprehensive description will be provided below with reference to the accompanying drawings. The drawings illustrate preferred embodiments of the invention. However, this invention can be implemented in many different forms and is not limited to the embodiments described herein.

[0027] like Figure 1 and Figure 2 As shown, this embodiment provides a differential transmission line wiring structure for a circuit board. The circuit board includes a circuit layer 1, which includes a BGA region 2, a non-BGA region 3, and two differential transmission lines 4 that are arranged opposite to each other and extend from the BGA region 2 to the non-BGA region 3. The BGA region 2 includes a plurality of vias 21, with a clamping region 22 formed between two adjacent vias and a non-clamping region 23 formed between two adjacent clamping regions 22. The differential transmission line 4 includes a first differential transmission line 41 located in the BGA region 2 and a second differential transmission line 42 located in the non-BGA region 3. The first differential transmission line 41 includes a narrow line 411 located in the clamping region 22 and a wide line 412 located in the non-clamping region 23. The line width of the narrow line 411 is smaller than the line width of the wide line 412, and the line width of the narrow line 411 is also smaller than the line width of the second differential transmission line 42.

[0028] In this embodiment, the two first differential transmission lines 41 are located between the same two vias 21, sharing parasitic parameters between the vias 21, such as inter-via capacitance. By synchronously adjusting the line width and spacing, an equivalent LC resonant compensation structure is formed, reducing impedance abrupt changes between the vias 21. Compared to the two first differential transmission lines 41 being located between different vias 21, the influence of the vias 21 on signal transmission can be effectively avoided. The two first differential transmission lines 41 are axially symmetrical about the symmetry line of the two vias 21. Through the symmetrical design of the BGA region 2, i.e., the two narrow lines 411 and the wide line 412 are completely mirrored, the geometric consistency of the signal transmission path is ensured.

[0029] In this embodiment, the line spacing between the two narrow lines 411 is not less than the first line spacing threshold, such as... Figure 1 As shown, the spacing between the two narrow lines 411 is equal to the spacing between the two wide lines 412; Figure 2As shown, the spacing between the two narrow lines 411 is less than the spacing between the two wide lines 412. The first spacing threshold is the minimum spacing processing capability of the two differential transmission lines 4 in BGA region 2, avoiding problems such as short circuits and high processing defect rates caused by excessively small spacing between the two narrow lines 411. In the non-clamped area 23 of BGA region 2, the wiring space is relatively spacious. While increasing the line width, the spacing between the two wide lines 412 can also be increased. By enhancing the coupling between differential pairs, the inductance increase caused by the reduction in line width is compensated, and the odd-mode impedance remains constant.

[0030] In this embodiment, the line spacing between the two second differential transmission lines 42 is not less than the second line spacing threshold, and the line spacing between the two second differential transmission lines 42 is greater than the line spacing between the two narrow lines 411. In the non-BGA region 3, under the condition of meeting the differential impedance requirements of the circuit board, the line width and line spacing of the two differential transmission lines are maximized as much as possible, thereby improving the signal transmission performance of the circuit board. The second line spacing threshold is the optimal design line spacing of the two differential transmission lines in the non-BGA region 3. By adjusting the line width and line spacing of the two second differential transmission lines 42, the stability of high-speed signal transmission is ensured, while avoiding problems such as short circuits and high manufacturing defect rates caused by excessively small line spacing between the two second differential transmission lines 42. Furthermore, the differential transmission line 4 also includes a connecting line 43 that is inclined and connects the first differential transmission line 41 and the second differential transmission line 42. The spacing between the two first differential transmission lines 41 is smaller than that between the two second differential transmission lines 42. The two are connected by a sloping and gradually wide connecting line 43. The sloping angle of the connecting line 43 is between 125° and 165°, forming a gradually changing impedance structure to reduce signal loss.

[0031] Specifically, in this embodiment, in BGA region 2, the spacing between the two vias 21 is 31.5 mil, the aperture of the via 21 is 8 mil, the spacing between the via 21 and the first differential transmission line 41 is designed to be 7 mil, and the wiring space in the clamping area 22 is 9.5 mil. In the design worksheet, the following can be used: Figure 1 The wiring structure shown has the following characteristics: In BGA region 2, the narrow line 411 has a line width of 3.75 mil, the spacing between two narrow lines 411 is 2 mil, and the wide line 412 has a line width of 5.45 mil; in non-BGA region 3, the second differential transmission line 42 has a line width of 5.6 mil, and the spacing between two second differential transmission lines 42 is 5.4 mil. In the design worksheet, a similar approach can also be adopted. Figure 2The wiring structure shown has the following characteristics: In BGA region 2, the narrow line 411 has a line width of 3.75 mil and a line spacing of 2 mil between two narrow lines 411; the wide line 412 has a line width of 6.6 mil and a line spacing of 4.4 mil between two wide lines 412. In non-BGA region 3, the second differential transmission line 42 has a line width of 5.6 mil and a line spacing of 5.4 mil between two second differential transmission lines 42. The line width and line spacing designs may vary in other possible embodiments and are not specifically limited here.

[0032] This solution's differential transmission line routing structure achieves a balance between high-density routing and signal integrity in the BGA region 2 of the circuit board through zoned linewidth adjustment. In the limited routing space of the clamping area 22 between adjacent vias 21 in BGA region 2, the impact of the high-density layout between vias 21 is offset by reducing the linewidth (narrow line 411). The narrow linewidth reduces the parasitic capacitance effect between vias, avoiding impedance abrupt changes due to excessive linewidth, thus maintaining the impedance continuity of the differential pair. Simultaneously, for the dense via 21 layout of the BGA solder ball array, the narrow line design in the clamping area 22 avoids the risk of short circuits between lines and vias. In the non-clamping area 23 of BGA region 2, where routing space is more ample, a wider linewidth is restored to compensate for the loss of narrow line segments. In the non-BGA region 3, the second differential transmission line 42 can use a standard wide linewidth, reducing transmission loss and simplifying impedance matching design, suitable for long-distance routing. This design effectively solves the problem of insufficient impedance of differential transmission lines in the BGA region 2 of the circuit board, affecting high-speed signal transmission.

[0033] In the description of this utility model, it should be understood that terms such as "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0034] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, the inclusion of "first," "second," etc., in a feature may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0035] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A differential transmission line wiring structure of a circuit board, the circuit board including a wiring layer, characterized by, The line layer includes a BGA region, a non-BGA region, and two differential transmission lines that are arranged opposite to each other and extend from the BGA region to the non-BGA region. The BGA region includes a plurality of vias, a clamping area between two adjacent vias, and a non-clamping area between two adjacent clamping areas. The differential transmission line includes a first differential transmission line located in the BGA region and a second differential transmission line located in the non-BGA region. The first differential transmission line includes a narrow line located in the clamping area and a wide line located in the non-clamping area. The line width of the narrow line is smaller than the line width of the wide line.

2. The differential transmission line wiring structure of claim 1, wherein, The two first differential transmission lines are located between the same two vias.

3. The differential transmission line routing structure of claim 2, wherein, The two first differential transmission lines are axially symmetrical about the lines of symmetry of the two vias.

4. The differential transmission line wiring structure of claim 1, wherein, The distance between the two narrow lines is not less than the first distance threshold.

5. The differential transmission line routing structure of claim 4, wherein, The spacing between the two narrow lines is less than or equal to the spacing between the two wide lines.

6. The differential transmission line routing structure of claim 4, wherein, The line spacing between the two second differential transmission lines is not less than the second line spacing threshold.

7. The differential transmission line routing structure of claim 6, wherein, The spacing between the two second differential transmission lines is greater than the spacing between the two narrow lines.

8. The differential transmission line routing structure of claim 7, wherein, The differential transmission line also includes a connecting line that is angled and connects the first differential transmission line and the second differential transmission line.

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