Hybrid circuit board for differential fractional-mode signals

Abstract

The invention provides a differential fractional-mode signal hybrid circuit board which comprises a multi-layer board, a digital signal line and an analog signal line which are distributed on the same layer, specifically, a top layer and a bottom layer, the second layer and the last but one layer are hollowed out, so that the differential impedance of the analog signal line and the digital signal line is the same under the condition that the line widths are different, and a ground shielding layer is arranged on the multi-layer board. The third layer of the multi-layer board is used as a ground shielding layer of a top-layer analog signal line, the last but one layer is used as a ground shielding layer of a bottom-layer analog signal line, the second layer of the multi-layer board is used as a ground shielding layer of a top-layer digital signal line, and the last but one layer is used as a ground shielding layer of a bottom-layer digital signal line; ground copper is laid on the inner side of each ground shielding layer; according to the hybrid circuit board, under the condition that the differential impedance of the analog signal and the differential impedance of the digital signal are the same, the transmission loss of the analog signal is reduced by increasing the medium thickness of the analog signal, and then the signal quality of the analog signal is improved.

Description

Technical Field

[0001] The invention relates to the technical field of PCBs, and in particular to a hybrid circuit board for differential digital-analog signals. Background Art

[0002] At present, the key indicators of high-speed PCB products include transmission line loss, impedance matching and delay consistency. Transmission line loss can be divided into dielectric loss, conductor loss and radiation loss. Dielectric loss mainly depends on the glass fiber and resin of the PCB board. The smaller the material DK (dielectric constant) and Df (loss factor), the smaller the loss; conductor loss is mainly affected by the "skin effect" and the roughness of the conductor surface; the smaller the roughness, the smaller the conductor loss. For differential digital-analog hybrid boards, it is often difficult to ensure the signal quality of analog signals if the wiring is done on the same layer. Summary of the invention

[0003] The present invention provides a hybrid circuit board for differential analog signals, aiming to reduce analog signal transmission loss and improve signal quality while satisfying the same impedance in the same layer wiring.

[0004] The present invention provides a hybrid circuit board for differential digital-analog signals, comprising:

[0005] Multilayer board;

[0006] The digital signal lines and the analog signal lines are distributed in the same layer, specifically the top layer and the bottom layer, wherein the second layer and the second to last layer are hollowed out so that the analog signal lines and the digital signal lines have the same differential impedance when the line widths are different;

[0007] The ground shielding layer is configured such that the third layer of the multilayer board is used as the ground shielding layer of the top-layer analog signal line, the third-to-last layer is used as the ground shielding layer of the bottom-layer analog signal line, the second layer of the multilayer board is used as the ground shielding layer of the top-layer digital signal line, and the second-to-last layer is used as the ground shielding layer of the bottom-layer digital signal line, and ground copper is laid on the inner side of each ground shielding layer.

[0008] In one embodiment, the differential impedance of the analog signal line and the digital signal line is 100 ohms.

[0009] In one of the embodiments, the hybrid circuit board for differential digital-analog signals according to claim 1 is characterized in that a ground copper foil is laid at a preset distance around the digital signal line and the analog signal line to shield interference between the signal lines.

[0010] In one of the embodiments, ground vias with preset apertures are distributed at a certain distance along the wiring lines of the digital signal lines and the analog signal lines, so that the signals can flow back nearby.

[0011] In one embodiment, the preset distance is 20 mi l.

[0012] In one embodiment, ground vias with preset apertures are distributed along the wiring lines of the digital signal lines and the analog signal lines at a certain distance so that the signals can flow back nearby, specifically:

[0013] Ground vias with an aperture of 10 mi l are distributed along the wiring lines of the digital signal lines and the analog signal lines at a center distance of 80 mi l, so that the signals can flow back nearby.

[0014] In one embodiment, the line width of the analog signal line is 17.1mil, the spacing of the differential pair is 13.9mil, the dielectric layer thickness of the top analog signal line is 12.684mil, the dielectric layer thickness of the bottom analog signal line is 12.735mil, and the dielectric constant is 3.8.

[0015] In one embodiment, the line width of the digital signal line is 4.4mil, the spacing of the differential pair is 8.1mil, the dielectric layer thickness of the top digital signal line is 2.992mil, the dielectric layer thickness of the bottom digital signal line is 2.992mil, and the dielectric constant is 3.2.

[0016] In one embodiment, the multi-layer board is a 10-layer mixed-pressed board, wherein the 1st to 2nd layers and the 9th to 10th layers are PCB board R-5775G, and the inner layer is PCB board TU768.

[0017] In one embodiment, the multilayer board is 1.8 mm thick.

[0018] The present invention discloses a hybrid circuit board for differential digital-analog signals, comprising a multilayer board, wherein digital signal lines and analog signal lines are distributed in the same layer, specifically a top layer and a bottom layer, wherein the second layer and the penultimate layer are hollowed out so that the analog signal lines and the digital signal lines have the same differential impedance when the line widths are different, and a ground shielding layer, wherein the third layer of the multilayer board is used as the ground shielding layer for the top layer analog signal line, the penultimate layer is used as the ground shielding layer for the bottom layer analog signal line, the second layer of the multilayer board is used as the ground shielding layer for the top layer digital signal line, the penultimate layer is used as the ground shielding layer for the bottom layer digital signal line, and ground copper is laid on the inner side of each ground shielding layer; while satisfying the requirement that the differential impedance of analog signals and digital signals is the same, the hybrid circuit board reduces the transmission loss of analog signals by increasing the dielectric thickness of analog signals, thereby improving the signal quality of analog signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. The drawings described below are only drawings corresponding to some embodiments of the present invention. For ordinary technicians in this field, drawings of other embodiments can be obtained based on these drawings without creative work.

[0020] Figure 1 This is a schematic diagram of the structure of a hybrid circuit board for differential digital-analog signals in one of the embodiments of the present invention;

[0021] Figure 2 A schematic diagram of the wiring of analog signal lines in another embodiment of the present invention;

[0022] Figure 3 yes Figure 2 An enlarged view of region A;

[0023] Figure 4 This is a schematic diagram of the wiring of digital signal lines in one embodiment of the present invention;

[0024] Figure 5 yes Figure 4 Magnified view of area B. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0026] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0027] See also Figure 1 The present invention provides a hybrid circuit board for differential digital-analog signals, comprising:

[0028] Multilayer board;

[0029] The digital signal lines and the analog signal lines are distributed in the same layer, specifically the top layer and the bottom layer, wherein the second layer and the second to last layer are hollowed out so that the analog signal lines and the digital signal lines have the same differential impedance when the line widths are different. The digital signal lines and the analog signal lines are specifically differential digital signal lines and differential analog signal lines.

[0030] The ground shielding layer is configured such that the third layer of the multilayer board is used as the ground shielding layer of the top-layer analog signal line, the third-to-last layer is used as the ground shielding layer of the bottom-layer analog signal line, the second layer of the multilayer board is used as the ground shielding layer of the top-layer digital signal line, and the second-to-last layer is used as the ground shielding layer of the bottom-layer digital signal line, and ground copper is laid on the inner side of each ground shielding layer.

[0031] Specifically, the multilayer board of this embodiment is a 10-layer mixed pressure board. Figure 1 Layer 1 to layer 10 are used to represent the PCB material R-5775G for layers 1-2 and 9-10, and PCB material TU768 for the inner layer. PCB material R-5775G uses polyphenylene ether resin as the base resin, which has good low dielectric constant and low dielectric loss angle. PCB material TU768 has many excellent properties, such as stable thermal expansion coefficient, good resistance to CAF (Conductivity Anodized Filation, ion migration), strong resistance to chemical corrosion, excellent heat resistance, low water absorption, etc.

[0032] In this embodiment, the thickness of the 1st, 5th, 6th and 10th layers is 1.2mil, and the thickness of the other 5 layers is 0.6mil. The total thickness of the 10-layer mixed board is about 70.80mil.

[0033] The copper clad core board (Core) is covered between the 1st and 2nd layers, between the 3rd and 4th layers, between the 5th and 6th layers, between the 7th and 8th layers, and between the 9th and 10th layers, with thicknesses of 2.992mil, 4.33mil, 5.12mil, 4.33mil, and 2.992mil, respectively, and the overall structure is symmetrical.

[0034] Between the 2nd and 3rd layers, between the 4th and 5th layers, between the 6th and 7th layers, and between the 8th and 9th layers, there are covered semi-cured sheets (Prepreg), with thicknesses of 9.092mil, 10.492mil, 10.457mil, and 9.143mil, respectively.

[0035] For differential digital-analog hybrid circuit boards, if the digital signal lines and analog signal lines have the same differential impedance control requirements when they are routed on the same layer, usually the digital signal routing has a higher utilization rate of space, the routing distribution is denser, and the routing line width is thinner to reasonably utilize the space. However, when routing analog signals, a wider routing is required under the same medium to reduce the insertion loss caused by signal transmission. At this time, the dielectric thickness referenced by the digital signal differential and the RF signal differential routing is different. The thicker the medium, the thicker the line width of the analog signal line, and the smaller the transmission differential loss.

[0036] The hybrid circuit board of differential digital-analog signals of this embodiment distributes digital signal lines and analog signal lines on the same layer, specifically the 1st layer and the 10th layer, hollows out the 2nd layer and the 9th layer, uses the 3rd layer as the ground shielding layer of the 1st layer analog signal line, the 8th layer as the ground shielding layer of the 10th layer analog signal line, uses the 2nd layer as the ground shielding layer of the 1st layer digital signal line, and the 9th layer as the ground shielding layer of the 10th layer digital signal line, and ground copper is laid on the inner side of each ground shielding layer. The hybrid circuit board increases the dielectric thickness of the analog signal line, satisfies the same differential impedance of the analog signal line and the digital signal line, and enables the analog signal line to have a wider line width, thereby reducing the transmission loss of the analog signal.

[0037] Specifically, the differential impedance of the analog signal line and the digital signal line is 100 ohms.

[0038] See also Figure 2 and Figure 3 In one embodiment, the line width W1 of the analog signal line is 17.1mil, the spacing D1 (edge ​​to edge) of the differential pair is 13.9mil, the avoidance distance D2 (edge ​​to edge) between the wiring and the ground copper foil 11 is 20mil, the center spacing D3 of the via hole 12 is 80mil, the diameter D4 of the via hole 12 is 10mil, the dielectric layer thickness of the top analog signal line is 12.684mil, the dielectric layer thickness of the bottom analog signal line is 12.735mil, and the dielectric constant is 3.8.

[0039] See also Figure 4 and Figure 5 In one embodiment, the line width W2 of the digital signal line is 4.4mil, the spacing D6 (edge ​​to edge) of the differential pair is 8.1mil, the avoidance distance D7 (edge ​​to edge) between the wiring and the ground copper foil 21 is 20mil, the center spacing D8 of the via hole 22 is 80mil, the diameter D7 of the via hole 22 is 10mil, the dielectric layer thickness of the top digital signal line is 2.992mil, the dielectric layer thickness of the bottom digital signal line is 2.992mil, and the dielectric constant is 3.2.

[0040] According to the Si9000 software, it can be calculated that the differential impedance of the analog signal line and the digital signal line is 100 ohms. Among them, the parameter values ​​of the analog signal line and the digital signal line are not unique, and other parameter values ​​that satisfy the differential impedance of the analog signal line and the digital signal line are both 100 ohms are also within the conception of the embodiments of the present application.

[0041] In one embodiment, a ground copper sheet is laid around the digital signal line and the analog signal line at a preset distance, including Figure 2 The ground copper foil 11 and Figure 4The copper ground 21 around the digital signal line is shown to shield interference between the signal lines.

[0042] Specifically, the preset distance is 20 mi l, but the embodiments of the present application are not limited to this distance.

[0043] In one embodiment, ground vias with preset apertures are distributed at a certain distance along the wiring lines of the digital signal lines and the analog signal lines, including Figure 2 The ground vias 12 and Figure 4 The ground vias 22 distributed along the wiring lines of the digital signal lines as shown enable the signals to flow back nearby, thus improving the signal quality.

[0044] The signal return path has a great influence on the impedance of the signal. By adding ground vias near the transmission line and its vias, the impedance discontinuity can be effectively reduced, thereby improving the reflection phenomenon caused by impedance discontinuity, reducing EMC problems, and improving the signal quality of analog and digital signals.

[0045] Specifically, ground vias with an aperture of 10 mi l are distributed along the wiring lines of the digital signal lines and the analog signal lines at a center distance of 80 mi l, so that the signal can flow back nearby.

[0046] Specifically, in one of the embodiments, the multilayer board is 1.8 mm thick.

[0047] The hybrid circuit board of differential digital-analog signals in the embodiment of the present application proposes a 100-ohm RF differential microstrip line wiring design method, which increases the line width of the analog signal by hollowing out the dielectric layer and reducing the transmission loss of the analog signal, while achieving consistent analog-digital differential impedance. Copper foil is distributed on the wiring lines of the analog signal lines and the digital signal lines to shield the interference between the signal lines, and vias are evenly distributed, so that the signal flows back nearby, further improving the signal quality, and a hybrid circuit board of differential analog-digital signals with low loss and excellent signal quality can be obtained.

[0048] To sum up, although the present invention has been disclosed as above in the form of preferred embodiments, the protection scope of the present invention is not limited thereto, and any technician familiar with the technical field can make equivalent substitutions or changes according to the concept of the technical solution of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0049] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A hybrid circuit board for differential digital-analog signals, characterized in that: include: Multilayer board; The digital signal lines and the analog signal lines are distributed in the same layer, specifically the top layer and the bottom layer, wherein the second layer and the second to last layer are hollowed out so that the analog signal lines and the digital signal lines have the same differential impedance when the line widths are different; The ground shielding layer is configured such that the third layer of the multilayer board is used as the ground shielding layer of the top-layer analog signal line, the third-to-last layer is used as the ground shielding layer of the bottom-layer analog signal line, the second layer of the multilayer board is used as the ground shielding layer of the top-layer digital signal line, and the second-to-last layer is used as the ground shielding layer of the bottom-layer digital signal line, and ground copper is laid on the inner side of each ground shielding layer.

2. The hybrid circuit board for differential digital-analog signals according to claim 1, characterized in that: The differential impedance of the analog signal line and the digital signal line is 100 ohms.

3. The hybrid circuit board for differential digital-analog signals according to claim 1, characterized in that: A ground copper sheet is laid at a preset distance around the digital signal line and the analog signal line to shield interference between the signal lines.

4. The hybrid circuit board for differential digital-analog signals according to claim 1, characterized in that: Ground vias with preset apertures are distributed at a certain distance along the wiring lines of the digital signal lines and the analog signal lines, so that the signals can flow back nearby.

5. The hybrid circuit board for differential digital-analog signals according to claim 3, characterized in that: The preset distance is 20 mil.

6. The hybrid circuit board for differential digital-analog signals according to claim 4, characterized in that: Said Ground vias with preset apertures are distributed along the wiring lines of the digital signal lines and the analog signal lines at a certain distance, so that the signals can flow back nearby, specifically: Ground vias with an aperture of 10 mils are distributed along the wiring lines of the digital signal lines and the analog signal lines at a center distance of 80 mils, so that the signals can flow back nearby.

7. The hybrid circuit board for differential digital-analog signals according to claim 2, characterized in that: The line width of the analog signal line is 17.1 mil, the spacing of the differential pair is 13.9 mil, the dielectric layer thickness of the top analog signal line is 12.684 mil, the dielectric layer thickness of the bottom analog signal line is 12.735 mil, and the dielectric constant is 3.

8.

8. The hybrid circuit board for differential digital-analog signals according to claim 2, characterized in that: The line width of the digital signal line is 4.4 mil, the spacing of the differential pair is 8.1 mil, the dielectric layer thickness of the top digital signal line is 2.992 mil, the dielectric layer thickness of the bottom digital signal line is 2.992 mil, and the dielectric constant is 3.

2.

9. The hybrid circuit board for differential digital-analog signals according to claim 1, characterized in that: The multilayer board is a 10-layer mixed-pressed board, wherein the 1st to 2nd layers and the 9th to 10th layers are PCB board R-5775G, and the inner layer is PCB board TU768.

10. The hybrid circuit board for differential digital-analog signals according to claim 9, characterized in that: The multilayer board has a thickness of 1.8 mm.

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