Differential line pair isometric structure based on HTCC

Abstract

The utility model discloses an HTCC-based differential line pair inner equal-length structure. Comprising a routing of a P-end differential line on a first wiring layer, a routing of an N-end differential line on the first wiring layer, a routing of the P-end differential line on a transition layer, a routing of the N-end differential line on the transition layer, a routing of the P-end differential line on a second wiring layer, a routing of the N-end differential line on the second wiring layer, and a via hole of a differential transmission line from the first wiring layer to the transition layer, and the differential transmission line passes through a via hole, a differential transmission line input end bonding pad and a differential transmission line output end bonding pad from the transition layer to the second wiring layer. The structure provided by the utility model has three significant advantages: firstly, the space required for wiring can be greatly reduced; secondly, a transmission path is scientifically optimized, so that the signal transmission distance is effectively shortened; and finally, high quality and stability of signal transmission are powerfully ensured by means of a symmetrical and equal-length ingenious design.

Description

Technical Field

[0001] This utility model relates to the field of HTCC packaging substrate design technology, specifically, to a differential line pair equal length structure based on HTCC. Background Technology

[0002] HTCC (High Temperature Co-fired Ceramic) substrates have become a key material in microwave circuit design due to their excellent mechanical stress resistance, geometric stability, flexible blind and buried vias, high stack-up count, and superior corrosion resistance. In recent years, with the surge in demand for miniaturization in communication systems and the continuous improvement in the integration density of high-density mixed-signal chips, the application ratio of differential transmission lines in HTCC substrate design has increased significantly. [1] .

[0003] Differential transmission technology, as a core solution in modern high-speed circuit design, essentially optimizes signal integrity through a two-wire coupled transmission mechanism. Unlike traditional single-ended transmission (single signal line + reference ground line), the two complementary signal lines of a differential pair simultaneously carry electromagnetic signals with equal amplitude and a 180° phase difference. The symmetry control of the differential transmission lines is a crucial factor determining system performance. If there is a length deviation or asymmetrical routing between the two lines, it will lead to signal edge misalignment, causing problems such as increased common-mode components and eye diagram closure. Therefore, HTCC substrate routing design must employ a strict equal-length matching strategy to control the differential pair line length deviation within requirements, thereby ensuring the timing accuracy and integrity of signal transmission.

[0004] In the differential pair design of HTCC substrates, achieving phase consistency mainly relies on serpentine trace topology optimization and end-line length compensation techniques. [2][3][4][5] However, such methods have two technical limitations: first, the inherent periodic bending of the serpentine structure will consume additional wiring area, exacerbating the space constraints of high-density interconnect designs; second, the parasitic inductance effect introduced by the compensation segment will degrade signal integrity indicators. When the compensation amount exceeds the critical value, it will lead to a chain reaction such as increased insertion loss and loss of impedance continuity, ultimately causing an increase in the system-level bit error rate.

[0005] References

[0006] [1] Lu Qi, Liu Yingkun, Qiao Zhizhuang, et al. Research status and new progress of ceramic substrates [J]. Semiconductor Technology, 2021, 46(4):257-268. DOI:10.13290 / j.cnki.bdtjs.2021.04.001.

[0007] [2] Zhuhai Yibo Technology Co., Ltd. A differential pair line for a PCB board: CN202223122879.6[P]. 2023-06-23.

[0008] [3] Shenzhen Yibo Technology Co., Ltd. A differential trace design method that optimizes internal equal length and takes into account impedance balance: CN202410045678.5[P]. 2024-05-24.

[0009] [4] Shenzhen Xingsen Fast Circuit Technology Co., Ltd., Guangzhou Xingsen Fast Circuit Technology Co., Ltd., Yixing Silicon Valley Electronics Technology Co., Ltd. A differential pair equal length compensation impedance matching method: CN201711483320.7[P]. 2021-01-19.

[0010] [5] Suzhou Inspur Intelligent Technology Co., Ltd. A method, apparatus, system and storage medium for calculating the length of differential lines: CN202110978212.7[P]. 2021-11-09. Utility Model Content

[0011] To address the issues of excessive wiring area and high parasitic inductance in existing differential pair serpentine equal-length routing, this invention provides a differential pair internal equal-length structure based on HTCC, which achieves internal equal length without serpentine routing and offers excellent transmission performance.

[0012] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0013] A differential pair with equal length structure based on HTCC includes: traces of P-terminal differential lines in the first routing layer, traces of N-terminal differential lines in the first routing layer, traces of P-terminal differential lines in a transition layer, traces of N-terminal differential lines in a transition layer, traces of P-terminal differential lines in a second routing layer, traces of N-terminal differential lines in a second routing layer, vias of differential transmission lines from the first routing layer to the transition layer, vias of differential transmission lines from the transition layer to the second routing layer, input pads of differential transmission lines, and output pads of differential transmission lines; the traces of P-terminal differential lines and N-terminal differential lines within the differential pair in the first routing layer. The traces are located on the first routing layer; the traces of the P-end differential lines and the N-end differential lines within the differential pair are located on the transition layer; the traces of the P-end differential lines and the N-end differential lines within the differential pair are located on the second routing layer; the bottom pad of the via from the first routing layer to the transition layer of the differential transmission line to the top pad of the via from the transition layer to the second routing layer of the differential transmission line; the starting end of a differential pair trace, i.e., the input pad of the differential transmission line, is located on the first routing layer; the ending end of a differential pair trace, i.e., the output pad of the differential transmission line, is located on the second routing layer.

[0014] Furthermore, the trace width of the P-terminal differential line and the trace width of the N-terminal differential line in the first wiring layer are both 75um, and the line spacing is 300um.

[0015] Furthermore, the vias of the differential transmission line from the first wiring layer to the transition layer are located at the ends of the differential pair traces in the first wiring layer, and are a pair of vias through which the differential pair passes from the first wiring layer to the transition layer.

[0016] Furthermore, the via diameter is 100um, the via pad diameter is 200um, and the via height exceeds 300um.

[0017] Furthermore, the vias of the differential transmission line from the transition layer to the second wiring layer are located at the end of the differential pair traces in the transition layer, and are a pair of vias through which the differential pair passes from the transition layer to the second wiring layer.

[0018] Furthermore, the via diameter is 100um, the via pad diameter is 200um, and the via height exceeds 300um.

[0019] Furthermore, from the bottom pad of the via on the transition layer to the output pad of the differential transmission line, the trace width is 75um and the line spacing is 300um.

[0020] Furthermore, the diameter of the input pads of the differential transmission line is 200µm.

[0021] Furthermore, the diameter of the output pads of the differential transmission line is 200µm.

[0022] Furthermore, from the differential transmission line input pad to the top pad of the via of the differential transmission line from the first wiring layer to the transition layer.

[0023] The beneficial effects of this utility model are reflected in:

[0024] This invention effectively eliminates the single-end transmission line length deviation caused by the orientation difference of the input / output pads of the differential transmission line through a reverse routing design in the transition layer. This allows the differential transmission line to achieve strict internal length equalization without the need for traditional length equalization methods such as serpentine winding. The structure of this invention has three core advantages: first, it reduces the wiring space required; second, it shortens the signal transmission distance by optimizing the transmission path; and third, it effectively ensures signal transmission quality through its symmetrical length equalization structure. Simulation verification shows that this structure performs excellently in key performance indicators such as S-parameters, fully meeting the engineering requirements of high-speed differential signal transmission. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of an inner equal-length differential line pair structure based on HTCC according to this utility model;

[0026] Figure 2 This is a side view schematic diagram of an inner equal-length differential line pair structure based on HTCC according to this utility model;

[0027] Figure 3 This figure shows the transmission performance simulation results of an application example of a differential line pair with equal length based on HTCC according to this utility model.

[0028] In the figure, 1 is the HTCC substrate; 21 is the trace of the P-terminal differential line on the first wiring layer; 22 is the trace of the N-terminal differential line on the first wiring layer; 31 is the trace of the P-terminal differential line on the transition layer; 32 is the trace of the N-terminal differential line on the transition layer; 41 is the trace of the P-terminal differential line on the second wiring layer; 42 is the trace of the N-terminal differential line on the second wiring layer; 51 is the via of the differential transmission line from the first wiring layer to the transition layer; 52 is the via of the differential transmission line from the transition layer to the second wiring layer; 61 is the input pad of the differential transmission line; 62 is the output pad of the differential transmission line. Detailed Implementation

[0029] To make the technical problems, technical solutions, and beneficial effects of this utility model clearer, the present utility model will now be described in detail with reference to the accompanying drawings and embodiments. It should be particularly noted that the specific embodiments described below are only for explaining this utility model and do not constitute a limitation on the scope of protection of this utility model.

[0030] It should be noted that the directional terms such as "P end" and "N end" used in this article are based on the directional definitions shown in the attached diagrams and are for descriptive purposes only, not as restrictive terms. The terms "first" and "second" are used only to distinguish the objects being described and do not indicate importance or quantity limitations.

[0031] A differential line pair with equal length based on HTCC mainly includes:

[0032] (1) The difference line pair with equal length is a three-dimensional structure, such as Figure 1 , 2 As shown, the differential pairs are routed inside the HTCC multilayer circuit, passing through the first routing layer, the transition layer, and the second routing layer.

[0033] (2) The starting end of a differential pair trace, namely the differential transmission line input pad 61, is located in the first wiring layer. The diameter of the differential transmission line input pad 61 is 200um.

[0034] (3) The end of a differential pair trace, namely the differential transmission line output pad 62, is located on the second wiring layer. The diameter of the differential transmission line output pad 62 is 200um.

[0035] (4) The P-end differential line in the differential pair is located in the first wiring layer. The trace 21 of the P-end differential line and the trace 22 of the N-end differential line in the first wiring layer are located in the first wiring layer. They are strip lines inside the HTCC. They run from the input pad 61 of the differential transmission line to the top pad 71 of the via 51 of the differential transmission line from the first wiring layer to the transition layer. The trace width of the P-end differential line in the first wiring layer and the trace 22 of the N-end differential line in the first wiring layer are both 75um and the line spacing is 300um. The shape of the differential pair traces of the P-end differential line in the first wiring layer and the trace 22 of the N-end differential line in the first wiring layer can be changed, but the lengths of the P-end differential line in the first wiring layer and the trace 22 of the N-end differential line in the first wiring layer are equal.

[0036] (5) The via 51 of the differential transmission line from the first wiring layer to the transition layer is located at the end of the differential pair trace in the first wiring layer. It is a pair of vias from the differential pair through the first wiring layer to the transition layer. The via diameter is 100um, the via pad diameter is 200um, and the via height exceeds 300um.

[0037] (6) The P-end differential line in the differential pair is located in the transition layer. The trace 31 and the N-end differential line in the transition layer are located in the transition layer. The trace width is 75um from the bottom pad 72 of the via 51 of the differential transmission line from the first wiring layer to the top pad 81 of the via 52 of the differential transmission line from the transition layer to the second wiring layer. The line spacing and line length are determined by the angle α formed by the center line of the input pad 61 and the center line of the output pad 62 of the differential transmission line. The range of α is 0 to 90 degrees. The trace 31 of the P-end differential line in the transition layer and the trace 32 of the N-end differential line in the transition layer are of equal length and the routing directions are 180 degrees apart.

[0038] (7) The via 52 of the differential transmission line from the transition layer to the second wiring layer is located at the end of the differential pair trace in the transition layer. It is a pair of vias from the differential pair through the transition layer to the second wiring layer. The via diameter is 100um, the via pad diameter is 200um, and the via height exceeds 300um.

[0039] (8) The P-end differential line in the differential pair is traced 41 in the second wiring layer and the N-end differential line is traced 42 in the second wiring layer. They are striplines inside the HTCC. The differential transmission line runs from the transition layer to the bottom pad 82 of the via 52 in the second wiring layer to the output pad 62 of the differential transmission line. The trace width is 75um and the line spacing is 300um. The differential pair trace shape of the P-end differential line trace 41 in the second wiring layer and the N-end differential line trace 42 in the second wiring layer can be changed, but the lengths of the P-end differential line trace 21 in the first wiring layer and the N-end differential line trace 22 in the first wiring layer are equal.

[0040] like Figures 1 to 2 As shown, this utility model also provides a method for designing differential transmission lines with equal internal lengths based on an HTCC substrate 1. The HTCC substrate 1 has at least one pair of differential transmission lines, wherein the traces of the P-end differential lines on different layers are identified by numbers 21, 31, and 41, respectively, and the traces of the N-end differential lines on different layers are identified by numbers 22, 32, and 42, respectively. The via 51 from the first wiring layer to the transition layer is a pair of vias for the differential transmission lines from the first wiring layer to the transition layer, and the via 52 from the transition layer to the second wiring layer is a pair of vias for the differential transmission lines from the transition layer to the second wiring layer. For ease of description, the input pad 61 of the differential transmission line on the first wiring layer is defined as the input terminal, and the output pad 62 of the differential transmission line on the second wiring layer is defined as the output terminal.

[0041] In this embodiment, the differential transmission line starts from the input pad 61 of the differential transmission line and extends along the first wiring layer via a symmetrical trace of equal length to the via 51 from the first wiring layer to the transition layer. Specifically, the trace 21 of the P-end differential line in the first wiring layer and the trace 22 of the N-end differential line in the first wiring layer have equal lengths, the same direction, and constant spacing. Furthermore, the direction of the center line connecting the two differential input pads 61 is consistent with the direction of the center line connecting the via 51 from the first wiring layer to the transition layer.

[0042] The vias 51 of the differential transmission lines from the first wiring layer to the transition layer adopt uniform specifications, including the same height, aperture, and pad diameter. When the differential transmission lines pass through the transition layer, the traces 31 of the P-end differential lines and 32 of the N-end differential lines in the transition layer maintain the same length, but their routing directions are arranged in opposite directions of 180°. The trace length in the transition layer is determined by the spacing between the vias 51 of the differential transmission lines from the first wiring layer to the transition layer and the vias 52 of the differential transmission lines from the transition layer to the second wiring layer, as well as the included angle between the two center lines, resulting in a shorter overall path characteristic.

[0043] After the transition layer signal is transmitted from the transition layer to the second routing layer via the via of the differential transmission line, the P-end differential line trace 41 and the N-end differential line trace 42 of the second routing layer extend symmetrically to the differential transmission line output pad 62 in an equal-length manner, with their routing direction and spacing remaining constant. At this time, the center connection direction of the two differential output pads 62 corresponds to the center connection direction of the differential transmission line from the transition layer to the second routing layer via 52.

[0044] Figure 3 The figure shows the simulation results of the transmission performance in this embodiment. Figure 3 As can be seen, the S-parameters of the design method are excellent and can meet the differential signal transmission requirements of most application scenarios.

[0045] It should be noted that those skilled in the art can adjust and improve the implementation scheme according to actual needs. For example, the included angle formed by the center line connecting the via 51 of the differential transmission line from the first wiring layer to the transition layer and the center line of the via 52 of the differential transmission line from the transition layer to the second wiring layer can be arbitrarily taken in the range of 0°-90°, and such improved schemes should be considered to fall within the protection scope of the claims of this utility model.

Claims

1. A differential line pair of equal length structure based on HTCC, characterized in that, include: The routing of the P-terminal differential line in the first routing layer, the routing of the N-terminal differential line in the first routing layer, the routing of the P-terminal differential line in the transition layer, the routing of the N-terminal differential line in the transition layer, the routing of the P-terminal differential line in the second routing layer, the routing of the N-terminal differential line in the second routing layer, the via of the differential transmission line from the first routing layer to the transition layer, the via of the differential transmission line from the transition layer to the second routing layer, the input pad of the differential transmission line, and the output pad of the differential transmission line; the routing of the P-terminal differential line and the N-terminal differential line within the differential pair in the first routing layer are located in the first routing layer; The P-terminal differential line and the N-terminal differential line within the differential pair are located in the transition layer; the P-terminal differential line and the N-terminal differential line within the differential pair are located in the second routing layer; the bottom pad of the via from the first routing layer to the transition layer of the differential transmission line to the top pad of the via from the transition layer to the second routing layer of the differential transmission line; the starting end of a differential pair trace, i.e., the input pad of the differential transmission line, is located in the first routing layer; the ending end of a differential pair trace, i.e., the output pad of the differential transmission line, is located in the second routing layer.

2. The differential line pair equal length structure based on HTCC according to claim 1, characterized in that, The trace width of the P-terminal differential line and the trace width of the N-terminal differential line on the first wiring layer are both 75um and the line spacing is 300um.

3. The differential line pair equal length structure based on HTCC according to claim 1, characterized in that, The vias of the differential transmission line from the first wiring layer to the transition layer are located at the end of the differential pair traces in the first wiring layer. They are a pair of vias through which the differential pair passes from the first wiring layer to the transition layer.

4. The differential line pair equal length structure based on HTCC according to claim 3, characterized in that, The via diameter is 100um, the via pad diameter is 200um, and the via height exceeds 300um.

5. The differential line pair equal length structure based on HTCC according to claim 1, characterized in that, The vias of the differential transmission line from the transition layer to the second routing layer are located at the end of the differential pair traces in the transition layer. They are a pair of vias through which the differential pair passes from the transition layer to the second routing layer.

6. The differential line pair equal length structure based on HTCC according to claim 5, characterized in that, The via diameter is 100um, the via pad diameter is 200um, and the via height exceeds 300um.

7. The differential line pair equal length structure based on HTCC according to claim 1, characterized in that, From the bottom pad of the via on the transition layer to the output pad of the differential transmission line, the trace width is 75um and the line spacing is 300um.

8. The differential line pair equal length structure based on HTCC according to claim 1, characterized in that, The diameter of the input pads of the differential transmission line is 200um.

9. The differential line pair equal length structure based on HTCC according to claim 1, characterized in that, The diameter of the output pads of the differential transmission line is 200um.

10. The differential line pair equal length structure based on HTCC according to claim 1, characterized in that, From the input pad of the differential transmission line to the top pad of the via of the differential transmission line from the first wiring layer to the transition layer.

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