A printed circuit board with anti-signal interference

Abstract

A printed circuit board with anti-signal interference belongs to the technical field of printed circuit boards, and includes a base layer, a transition layer, and an edge layer. The upper surface of the edges of the base layer of the printed circuit board is fixedly connected to the edge layer, and the inner side of the edge layer to the center direction of the upper surface of the printed circuit board is fixedly connected to the transition layer. The thickness of the base layer, the transition layer, and the edge layer at the connection is less than the thickness of the center of the base layer, so that the upper surface of the base layer, the transition layer, and the edge layer is a plane after the three layers are connected. The dielectric constant of the edge layer is less than the dielectric constant of the base layer, and the dielectric constant of the transition layer is between the dielectric constants of the edge layer and the base layer. The thickness of the transition layer increases from the direction close to the center of the printed circuit board to the direction close to the edge layer, and the thickness of the transition layer at the connection between the transition layer and the edge layer is consistent. Signal lines are arranged in the base layer, the transition layer, and the edge layer. The present invention effectively removes interference and improves signal integrity by optimizing the edge of the PCB.

Description

Technical Field

[0001] The invention belongs to the technical field of printed circuit boards, and in particular relates to a printed circuit board capable of resisting signal interference. Background Art

[0002] With the high integration and rapid development of electronic devices, the speed and frequency of signal transmission in printed circuit boards (PCBs) are constantly increasing. When signals propagate on PCBs, they will be reflected due to the dielectric properties of the material, the geometry of the conductors, and the impedance mismatch of the connection points. When the signal reaches the edge of the PCB, the sudden impedance will cause part of the signal to be reflected back to the source, forming interference. This reflection not only affects the quality of the signal, but may also interfere with other signals, resulting in data errors and reduced system performance.

[0003] In order to deal with these problems, the prior art has proposed a variety of methods to suppress signal interference, such as improving PCB layout, using shielding materials, adding filters, etc. Improving PCB layout is to optimize the layout design of the PCB, reduce the length and turns of the signal path, and reduce the possibility of signal reflection. Using shielding materials is to use shielding materials on the PCB to absorb or block the electromagnetic radiation of the signal and reduce interference. Adding filters is to add filters in the signal path to filter out high-frequency signals and reduce interference. However, these methods often require a lot of design modifications or increase costs. Summary of the invention

[0004] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a printed circuit board with resistance to signal interference, which effectively removes interference and improves signal integrity by optimizing the edge of the PCB.

[0005] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0006] A printed circuit board with anti-signal interference comprises a base layer, a transition layer and an edge layer. The upper surface of the four edges of the base layer of the printed circuit board is fixedly connected to the edge layer, the inner side of the edge layer toward the center of the upper surface of the printed circuit board is fixedly connected to the transition layer, the bottom of the transition layer is fixedly connected to the upper surface of the base layer, the thickness of the base layer, the transition layer and the edge layer at the connection is less than the thickness of the center of the base layer, so that the upper surface of the base layer, the transition layer and the edge layer after being connected is a plane, the dielectric constant of the edge layer is less than the dielectric constant of the base layer, the dielectric constant of the transition layer is between the dielectric constants of the edge layer and the base layer, the thickness of the transition layer increases from the direction close to the center of the printed circuit board to the direction close to the edge layer, the thickness of the transition layer at the connection with the edge layer is consistent, and signal lines are arranged in the base layer, the transition layer and the edge layer.

[0007] Furthermore, the four corners of the edge of the printed circuit board are configured as rounded corners.

[0008] Furthermore, the radius of the fillet is 5 mm.

[0009] Furthermore, the material of the base layer is FR-4, and the material of the edge layer is PTFE.

[0010] Furthermore, the dielectric constant of the base layer is 4.4, the dielectric constant of the edge layer is 2.1, and the dielectric constant of the transition layer is between 2.1 and 4.4.

[0011] Furthermore, the dielectric constant of the transition layer is determined according to the following formula:

[0012] ε r(x) = ε r1 + (ε r2 - ε r1 ) × x / W2

[0013] Where: r(x) is the dielectric constant of the transition layer; ε r1 is the dielectric constant of the substrate layer; ε r2 is the dielectric constant of the edge layer; x It is the vertical distance from a point on the transition layer to the lateral connection position between the transition layer and the base layer; W2 is the width of the transition layer.

[0014] Furthermore, the dielectric constant of the transition layer is 3-4, and the material of the transition layer is Rogers RO4350B or Rogers RO4350B.

[0015] Furthermore, the thickness of the edge layer is one third to one quarter of the central thickness of the base layer; and the thickness of the transition layer transitions from 0.1 mm to the thickness of the edge layer.

[0016] Furthermore, the edge layer width is determined according to the following formula:

[0017] W1 = 0.1 × λ× (ε r1 + ε r2 ) / (ε r1 - ε r2 )

[0018] Where: W1 is the edge layer width; λ is the signal wavelength; ε r1 : dielectric constant of the substrate layer; ε r2 : Dielectric constant of the edge layer.

[0019] Furthermore, the width of the transition layer is determined according to the following formula:

[0020] W2 = 0.5 × (ε r2 - ε r1 ) / (ε r1+ ε r2 )

[0021] Where: W2 is the width of the transition layer; ε r1 is the dielectric constant of the substrate layer; ε r2 is the dielectric constant of the edge layer.

[0022] The beneficial effects of the present invention are as follows: the present invention reduces signal reflection, reduces the influence of interference on signals, improves signal integrity, reduces bit error rate, and improves the stability and reliability of electronic equipment by optimizing the PCB edge structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the layer structure of the printed circuit board for resisting signal interference of the present invention;

[0024] Figure 2 The figure is a schematic diagram of the rounded corner structure of the printed circuit board for resisting signal interference of the present invention.

[0025] In the figure: 1 is the base layer, 2 is the transition layer, 3 is the edge layer, 4 is the signal line, and 5 is the fillet. DETAILED DESCRIPTION

[0026] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0027] like Figure 1 As shown, the present invention provides a printed circuit board with anti-signal interference, including a base layer 1, a transition layer 2, and an edge layer 3. The upper surface of the four edges of the base layer 1 of the printed circuit board is fixedly connected to the edge layer 3, which can be specifically bonded; the inner side of the edge layer 3 toward the center of the upper surface of the printed circuit board is fixedly connected to the transition layer 2, which can be specifically bonded; the bottom of the transition layer 2 is fixedly connected to the upper surface of the base layer 1, which can be specifically bonded. The thickness of the connection between the base layer 1 and the transition layer 2 and the edge layer 3 is less than the center thickness of the base layer 1, so that the upper surface of the base layer 1, the transition layer 2, and the edge layer 3 is a plane after the three are connected, and the edge layer 3 is directly in contact with the external environment. After the three are connected, a flat PCB board is formed.

[0028] The dielectric constant of the edge layer 3 is smaller than that of the base layer 1, the dielectric constant of the transition layer 2 is between the dielectric constants of the edge layer 3 and the base layer 1, the thickness of the transition layer 2 increases from the direction close to the center of the printed circuit board to the direction close to the edge layer 3, the thickness of the transition layer 2 and the edge layer 3 are consistent at the connection, and the signal line 4 is arranged in the base layer 1, the transition layer 2, and the edge layer 3.

[0029] The present invention realizes smooth signal transmission and reduces reflection by setting the edge of the PCB board to have a transition reduction in dielectric constant. The present invention utilizes the reflection characteristic to counter signal interference and realizes anti-signal interference through the edge reflection method.

[0030] Specifically, Figure 2 As shown, the four corners of the edge of the printed circuit board are set to rounded corners 5. The radius of the rounded corners 5 is 5mm, which reduces the reflection of the signal at the edge. The principle of reducing the reflection of the signal at the edge by the edge rounding is achieved by reducing the sudden change of the signal at the edge. When the signal reaches the edge of the PCB, if the edge is at a right angle, the signal will suddenly change direction, resulting in signal reflection and interference. By adding rounded corners at the edge of the PCB, the sudden change of the signal at the edge can be reduced, thereby reducing signal reflection and interference. The rounded corners can make the signal turn smoothly at the edge, reducing signal reflection and interference.

[0031] Specifically, the dielectric constant of the base layer 1 is 4.4. The base layer 1 has a relatively high dielectric constant and can provide good signal transmission performance. The dielectric constant of the edge layer 3 is 2.1, and the dielectric constant of the transition layer 2 is between 2.1 and 4.4. More specifically, the material of the base layer 1 is FR-4, and the material of the edge layer 3 is PTFE. The edge layer 3 has a relatively low dielectric constant and can provide good signal shielding and reduce interference. Specifically, the dielectric constant of the transition layer 2 is determined according to the following formula:

[0032] ε r(x) = ε r1 + (ε r2 - ε r1 ) × x / W2

[0033] where ε r1 is the dielectric constant of the substrate layer, ε r2 is the dielectric constant of the edge layer, x It is the vertical distance from a point on the transition layer to the lateral connection position between the transition layer and the base layer, and W2 is the width of the transition layer.

[0034] More specifically, the material of the transition layer 2 can be Rogers RO4350B or Rogers RO4350B, the dielectric constant of the transition layer 2 is 3-4, the dielectric loss angle is about 0.0037, and the transition layer 2 has a dielectric constant gradient, which can achieve smooth signal transmission and reduce reflection.

[0035] The width of the edge layer 3 is set according to the actual PCB design requirements and signal frequency. The width of the edge layer is determined by the following formula:

[0036] W1 = 0.1 × λ× (εr1 + ε r2 ) / (ε r1 - ε r2 )

[0037] Where: W1 is the edge layer width; λ is the signal wavelength; ε r1 : dielectric constant of the substrate layer; ε r2 : Dielectric constant of the edge layer.

[0038] Specifically, the thickness of the edge layer 3 is one third to one quarter of the thickness of the center of the base layer 1; the thickness of the transition layer 2 transitions from 0.1 mm to the thickness of the edge layer 3, and the thickness of the transition layer 2 gradually increases from the side close to the center of the base layer 1 to the side close to the edge layer 3, forming a gradual change in dielectric constant to achieve the purpose of reducing reflection. More specifically, the width of the edge layer 3 can be 1-2 mm.

[0039] The width of the transition layer 2 is set according to the PCB design requirements and signal frequency, and is adapted to achieve dielectric constant transition and smooth signal transmission, so as to achieve smooth signal transmission and reduce reflection. The width of the transition layer is determined by the following formula:

[0040] W2 = 0.5 × (ε r2 - ε r1 ) / (ε r1 + ε r2 )

[0041] Where: W2 is the width of the transition layer; ε r1 is the dielectric constant of the substrate layer; ε r2 is the dielectric constant of the edge layer.

[0042] The present invention adopts a three-layer structure, so that the signal can be smoothly transmitted between the base layer 1 and the transition layer 2, reducing reflection and interference. At the same time, the edge layer 3 can provide good signal shielding, further reducing interference.

[0043] Example 1

[0044] Take the PCB design of a high-frequency wireless communication device as an example. The operating frequency of the device is 2.4 GHz, and the signal transmission loss is required to be less than 1 dB. However, when the PCB was performing signal integrity analysis, it was found that the interference caused by edge reflection caused the signal loss to reach 2 dB, which exceeded the design requirements. To this end, this embodiment provides a printed circuit board that is resistant to signal interference, wherein the base layer 1 is FR-4 with a dielectric constant of approximately 4.4; the transition layer 2 is Rogers RO4350B with a dielectric constant of approximately 3.48; and the edge layer 3 is PTFE with a dielectric constant of approximately 2.1. The thickness of the base layer 1 FR-4 is 1.6 mm, the thickness of the edge layer 3 is 0.5 mm, the width of the edge layer 3 is about 1-2 mm, and the thickness of the transition layer 2 gradually changes from 0.1 mm to 0.5 mm. The four corners of the PCB are rounded to change the edge of the PCB from a right angle to a rounded corner with a radius of 5 mm.

[0045] A network analyzer and a signal generator are used to perform a signal integrity simulation test on the PCB board of this embodiment. The input signal frequency is 2.4 GHz, the input signal source characteristic impedance is 50Ω, and the reflection coefficient is checked after the simulation signal passes through the gradient edge.

[0046] The test steps are as follows:

[0047] 1. Signal transmission test:

[0048] 1-1. Connect a signal generator to the input end of a PCB sample that does not adopt the configuration of the present invention.

[0049] 1-2. Use a network analyzer to measure the transmission characteristics of the signal, including signal loss and signal reflection coefficient.

[0050] 1-3. Record the initial value.

[0051] 2. Edge reflection test:

[0052] 2-1. Use the PCB sample set up by the edge reflection method of this embodiment 1, and connect the signal generator to the input end of the PCB sample set up in this embodiment 1.

[0053] 2-2. Repeat the testing process in step 1-2.

[0054] 2-3. Record the improved value.

[0055] 3. Signal transmission quality test:

[0056] 3-1. Use a signal generator to generate a high-frequency signal.

[0057] 3-2. Input the signal to the input end of the PCB sample using the present invention.

[0058] 3-3. Use a network analyzer to measure the signal transmission quality, including the signal amplitude and phase.

[0059] 3-4. Record the improved value.

[0060] The test results are shown in Table 1.

[0061] Table 1 Test results

[0062] Test items Initial Value After Improvement Signal loss 2dB 0.8dB Signal reflection coefficient -10 dB -20 dB

[0063] The results show that the signal loss is reduced from 2 dB to 0.8 dB, the reflection coefficient is increased from -10 dB to -20dB, and the signal integrity is significantly improved.

[0064] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. Alterations, modifications, substitutions and variations of the above embodiments by a person skilled in the art are all within the scope of the present invention.

Claims

1. A printed circuit board with resistance to signal interference, characterized in that: The printed circuit board comprises a base layer (1), a transition layer (2), and an edge layer (3), wherein the upper surface of the four edges of the base layer (1) of the printed circuit board is fixedly connected to the edge layer (3), the inner side of the edge layer (3) in the direction of the center of the upper surface of the printed circuit board is fixedly connected to the transition layer (2), the bottom of the transition layer (2) is fixedly connected to the upper surface of the base layer (1), and the thickness of the connection between the base layer (1), the transition layer (2), and the edge layer (3) is less than the center thickness of the base layer (1), so that the base layer (1), the transition layer (2), and the edge layer (3) are connected. After the three edge layers (3) are connected, the upper surface is a plane, the dielectric constant of the edge layer (3) is smaller than the dielectric constant of the base layer (1), the dielectric constant of the transition layer (2) is between the dielectric constants of the edge layer (3) and the base layer (1), the thickness of the transition layer (2) increases from a direction close to the center of the printed circuit board to a direction close to the edge layer (3), the thickness of the transition layer (2) and the edge layer (3) at the connection is consistent, and the signal line (4) is arranged in the base layer (1), the transition layer (2), and the edge layer (3).

2. A printed circuit board with resistance to signal interference according to claim 1, characterized in that: The four corners of the edge of the printed circuit board are configured as rounded corners (5).

3. A printed circuit board with resistance to signal interference according to claim 2, characterized in that: The radius of the rounded corner (5) is 5 mm.

4. The printed circuit board with anti-signal interference according to claim 1, characterized in that: The material of the base layer (1) is FR-4, and the material of the edge layer (3) is PTFE.

5. A printed circuit board with resistance to signal interference according to claim 4, characterized in that: The dielectric constant of the base layer (1) is 4.4, the dielectric constant of the edge layer (3) is 2.1, and the dielectric constant of the transition layer (2) is between 2.1 and 4.

4.

6. The signal interference resistant printed circuit board according to claim 1, characterized in that: The dielectric constant of the transition layer (2) is 3-4, and the material of the transition layer (2) is Rogers RO4350B.

7. The signal interference resistant printed circuit board according to claim 1, characterized in that: The thickness of the edge layer (3) is one third to one quarter of the central thickness of the base layer (1); and the thickness of the transition layer (2) transitions from 0.1 mm to the thickness of the edge layer (3).

8. The signal interference resistant printed circuit board according to claim 1, characterized in that: The width of the edge layer (3) is determined according to the following formula: W1 = 0.1 × λ× (ε r1 + e r2 ) / (e r1 - eh r2 ) Where: W1 is the edge layer width; λ is the signal wavelength; ε r1 : dielectric constant of the substrate layer; ε r2 : Dielectric constant of the edge layer.

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