CN114867192B

CN114867192B - High-frequency millimeter wave low-distortion type hybrid circuit board

Info

Publication number: CN114867192B
Application number: CN202210579158.3A
Authority: CN
Inventors: 张志强; 余康玲; 王东府
Original assignee: Shenzhen Jinshengda Electronics & Technology Co ltd
Current assignee: Shenzhen Jinshengda Electronics & Technology Co ltd
Priority date: 2022-05-26
Filing date: 2022-05-26
Publication date: 2023-10-13
Anticipated expiration: 2042-05-26
Also published as: CN114867192A

Abstract

The invention discloses a high-frequency millimeter wave low-distortion type mixed circuit board, which comprises: the circuit board is provided with a plurality of micropores, the micropores are used for connecting the first line layer with the second line layer or the third line layer, and the micropores are used for connecting the second line layer with the third line layer; the circuit board is sequentially from top to bottom: the first dielectric layer, the first line layer, the second dielectric layer, the third dielectric layer, the fourth dielectric layer, the second line layer, the fifth dielectric layer, the sixth dielectric layer, the seventh dielectric layer, the third line layer; and other components, to improve the efficiency of the antenna and the stability of the circuit operation.

Description

High-frequency millimeter wave low-distortion type hybrid circuit board

Technical Field

The invention relates to the technical field of circuit boards, in particular to a high-frequency millimeter wave low-distortion hybrid circuit board.

Background

Millimeter wave applications are becoming more and more popular with the popularity of 5G NR wireless networks and high frequency (77 GHz) automotive radar, while millimeter wave frequency signals can be transmitted entirely through highly integrated printed circuit boards. The circuit board processes different types of signals, including analog, digital, RF, and millimeter wave signals, simultaneously by providing a multi-layer structure. However, the millimeter wave application type circuit board mainly faces the problems of integration and miniaturization, and different circuit functions make the requirements of circuit board materials different, and the circuit board materials need to match the functions required to be realized by each circuit, such as: power circuits, high-speed digital circuits, low-frequency radio frequency circuits, microwave/high-frequency millimeter wave circuits, and the like.

The material selection of the circuit board generally needs to consider the electrical parameters of the material, such as: the dielectric constant Dk, loss factor Df/loss tangent, etc., and secondly, the mechanical properties of the materials (mainly affecting strength, transmission performance, transmission line spacing/size) and the connection between laminates of different materials, as well as other flow specifications of production and manufacturing processes, are considered according to the functions and the number of layers of the circuit, so as to ensure quality.

In the popularization of the application of the high-frequency millimeter wave, the influence of the high-speed digital circuit on the circuit board is more prominent, and the transmission delay, skew, timing difference and the like between adjacent signals are also influenced.

Accordingly, there is a need for a high frequency millimeter wave low distortion hybrid circuit board that solves one or more of the above problems.

Disclosure of Invention

The invention provides a high-frequency millimeter wave low-distortion type mixed circuit board for solving one or more problems in the prior art. The invention adopts the technical proposal for solving the problems that: a high frequency millimeter wave low distortion hybrid circuit board comprising: a circuit board, the circuit board comprising: the circuit board is provided with a plurality of micropores, the micropores are used for connecting the first line layer with the second line layer or the third line layer, and the micropores are used for connecting the second line layer with the third line layer;

the first wire layer, the second wire layer and the third wire layer are laminated plates composed of rolled copper and are connected by taking a chlorofluoroethylene copolymer or a fluoroethylene propylene copolymer as a bonding sheet;

the thicknesses of the first line layer, the second line layer, the third line layer, the second dielectric layer, the third dielectric layer, the fourth dielectric layer, the fifth dielectric layer, the sixth dielectric layer and the seventh dielectric layer are equal;

the first medium layer is a shielding layer, the second medium layer and the seventh medium layer are combined layers of flat open-fiber balance woven glass cloth and low-temperature co-fired ceramic particles, and the thickness density ratio of glass warp yarns on an X axis to weft yarns on a Y axis of glass fibers in the flat open-fiber balance woven glass cloth is in the range of 1 to 1.05;

the third medium layer and the sixth medium layer are flat open-fiber balance woven glass cloth and an improved resin combination layer;

the circuit board is sequentially from top to bottom: the first dielectric layer, the first line layer, the second dielectric layer, the third dielectric layer, the fourth dielectric layer, the second line layer, the fifth dielectric layer, the sixth dielectric layer, the seventh dielectric layer, the third line layer;

the base is arranged on the upper side of the first dielectric layer, an installation groove is formed in the base, a shielding layer is arranged on the bottom surface of the installation groove, and a wiring terminal is arranged at the edge of the base;

the antenna is fixedly arranged in the mounting groove;

the radio frequency chip and the signal wiring thereof are arranged on the third wire layer, and the radio frequency chip is connected with the antenna through the micropore and the wiring terminal.

Further, the fourth medium layer and the fifth medium layer are low-temperature co-fired ceramic particles and an improved resin combination layer.

Further, a first connecting layer, a first middle layer and a first connecting layer are sequentially arranged in the third medium layer from top to bottom, the first connecting layer is an improved resin layer, and the first middle layer is a mixed layer of the improved resin layer and flat open-fiber balance woven glass cloth;

the sixth medium layer is sequentially provided with a second connecting layer, a second intermediate layer and a second connecting layer from top to bottom, wherein the second connecting layer is an improved resin layer, and the second intermediate layer is a mixed layer of the improved resin layer and flat open-fiber balance woven glass cloth.

Further, the thickness of the first connecting layer is smaller than or equal to the thickness of the first intermediate layer, and the thickness of the second connecting layer is smaller than or equal to the thickness of the second intermediate layer.

Further, the circuit board is processed through laser drilling, and the micro holes are punched.

The beneficial effects obtained by the invention are as follows: the invention connects the first line layer, the first dielectric layer and the like together through ingenious layout, ensures that the thickness of each line layer and each dielectric layer is consistent after combination, ensures that the mechanical characteristics of each layer are kept relatively consistent in material thickness, ensures that the mechanical characteristics of each layer are similar under the influence of millimeter wave frequency through the consistency of the thickness, and ensures that the consistent thickness in performance and economy is obtained, and simultaneously avoids the influence caused by inconsistent mechanical characteristics, such as: the difference of phase response and insertion loss is caused, and the stability of the transmission line performance is obtained; the first line layer and the second line layer are provided with two dielectric layers containing flat open-fiber balance woven glass cloth, the distribution of glass fibers is more even through the multi-layer flat open-fiber balance woven glass cloth, the influence of glass fiber effect on the line board along with the increase of frequency or at higher digital speed is reduced, the DK value of the same transmission line passing place cannot generate quite large performance difference, and the Dk on the circuit board material becomes more even through the low-temperature cofired ceramic particle layer matched with the low Dk, so that the influence caused by the glass fiber effect under high frequency is reduced. The flat open-fiber balance woven glass cloth is characterized in that the thickness density ratio of glass yarns on a X, Y shaft is 1 (in ideal state, a certain redundant space is actually reserved), and knuckle intersection areas (areas with relatively more glass fibers) and bundle opening areas (areas with relatively less glass fibers) on the glass cloth in a weaving mode and specification are fewer, so that the abrupt change range of Dk values is fewer; the conductor on the wire layer can obtain a relatively ideal antenna efficiency and improve the stability under the high-frequency state under the condition of not being far away from the glass fiber, so that the distortion of the wire is lower. The practical value of the invention is greatly improved.

Drawings

FIG. 1 is a schematic illustration of the present invention;

FIG. 2 is a cross-sectional view of the present invention;

fig. 3 is an enlarged partial view of a cross-sectional view of the present invention.

[ reference numerals ]

First thread layer

110 second wire layer

Third wire layer 120 ·

130.base

131.mounting groove

132.

201.first dielectric layer

301. Micro-pores

401.second dielectric layer

501 third dielectric layer

510 first connection layer

520 first intermediate layer

601.fourth dielectric layer

701.A fifth dielectric layer

801..sixth dielectric layer

810 second connection layer

820 second intermediate layer

901.A seventh dielectric layer.

Detailed Description

In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention briefly described above will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The invention may be embodied in many other forms than described herein without departing from the spirit or scope of the invention as defined in the following claims.

As shown in fig. 1 to 3, the present invention discloses a high-frequency millimeter wave low-distortion hybrid circuit board, which comprises: a circuit board, the circuit board comprising: the circuit board is provided with a plurality of micropores 301, the micropores 301 connect the first line layer 101 with the second line layer 110 or the third line layer 120, and the micropores 301 connect the second line layer 110 with the third line layer 120;

the first wire layer 101, the second wire layer 110 and the third wire layer 120 are laminated boards made of rolled copper and are connected by using a vinyl chloride-vinyl fluoride copolymer or a vinyl fluoride-propylene copolymer as a bonding sheet (the vinyl chloride-vinyl fluoride copolymer or the vinyl fluoride-propylene copolymer has small dielectric constant in the Z-axis direction and small loss factor at high frequency, and the expansion coefficient of the Z-axis is low, so that the reliability of the plated through holes can be ensured, and the laminated boards are compatible with flat open-fiber balanced woven glass cloth materials, so that the connection reliability can be ensured);

the thicknesses of the first line layer 101, the second line layer 110, the third line layer 120, the second dielectric layer 401, the third dielectric layer 501, the fourth dielectric layer 601, the fifth dielectric layer 701, the sixth dielectric layer 801, and the seventh dielectric layer 901 are equal;

the first dielectric layer 201 is a shielding layer, the second dielectric layer 401 and the seventh dielectric layer 901 are combined layers of flat open-fiber balance woven glass cloth and low-temperature co-fired ceramic particles, and the thickness density ratio of glass warp yarns on an X axis to weft yarns on a Y axis of glass fibers in the flat open-fiber balance woven glass cloth is in a range of 1 to 1.05;

the third dielectric layer 501 and the sixth dielectric layer 801 are flat open-fiber balance woven glass cloth and an improved resin combination layer;

the circuit board is sequentially from top to bottom: the first dielectric layer 201, the first line layer 101, the second dielectric layer 401, the third dielectric layer 501, the fourth dielectric layer 601, the second line layer 110, the fifth dielectric layer 701, the sixth dielectric layer 801, the seventh dielectric layer 901, and the third line layer 120;

the base 130 is arranged on the upper side of the first dielectric layer 201, an installation groove 131 is arranged in the base 130, a shielding layer is arranged on the bottom surface of the installation groove 131, and a wiring terminal 132 is arranged on the edge of the base 130;

an antenna fixedly installed in the installation recess 131;

the radio frequency chip and the signal wiring thereof are disposed on the third wire layer 120, and the radio frequency chip is connected with the antenna through the micro-hole 301 and the connection terminal 132.

It should be noted that, the first dielectric layer 201 is a shielding layer, which is not only used to reduce the influence of millimeter waves on the first line layer 101, but also serves to isolate the first line layer 101 from the outside. The conductor on the first line layer 101 forms an entire electromagnetic environment with the external air under the high frequency condition, so that the dielectric constant is increased (under the high frequency condition, the electric field and the magnetic field generated by the conductor on the first line layer 101 can propagate out of the page, and then form the entire electromagnetic environment with the air, and at this time, the effective dielectric constant is the combination of the dielectric constant of the substrate material and the dielectric constant of the air, that is, the dielectric constant is unstable or increased, so that the stability of the circuit is poor or the efficiency of the antenna is poor). The improved resin is an improved epoxy resin, which is applied to the FR5 type glass cloth substrate in the prior art, and will not be described in detail herein.

In the millimeter wave range, the mechanical properties of the circuit board material, such as: the thickness and consistency of thickness will have an impact on circuit performance and therefore, by maintaining consistent thicknesses of the various dielectric layers and wire layers, the mechanical properties are tuned to improve circuit performance. Also, at small wavelengths, the roughness of the conductor also affects the performance of the circuit, the average surface roughness of the rolled copper is about 0.35 μm RMS, the average surface roughness of the conventional standard electrolytic copper is about 2.0 μm RMS, and the smooth copper foil surface has less effect on conductor loss (the rougher the copper foil, the more the electromagnetic wave propagation path of the circuit will increase, and the slow wave effect is formed, so that the dielectric constant on the circuit is higher than the nominal value thereof, and further the phase delay of signal propagation is caused), thus the effect on the insertion loss is also small, and the circuit performance can be improved under high-frequency millimeter waves.

At millimeter wave frequencies, particularly at high frequencies, even if the dielectric constant of the wiring board material changes little, it may cause a change in electrical properties.

The flat open-fiber balance woven glass cloth is a glass cloth adopting a flat open-fiber weaving mode, wherein the balance means that the thickness density ratio of glass warp yarns on an X axis and weft yarns on a Y axis of glass fibers is within a certain range, and the range is about 1 to 1.05, so that certain error redundancy is provided for actual production. The flat open-fiber balanced woven glass cloth is smaller in dielectric constant and more even in glass fiber distribution compared with the glass cloth in a standard weaving mode; the glass fiber yarns generally have different geometric structures in the bundling and opening areas between the bundling and the opening areas, but the thickness of the glass fiber yarns determines whether the glass fiber yarns are balanced, namely, the change of the dielectric constant of the balanced woven glass cloth on a horizontal plane is smoother, so that the same transmission line is less influenced (the generated signal delay and phase difference are reduced) when passing, and the performances of the antenna and the transmission line are improved (the working efficiency of the antenna is mainly influenced by the dielectric constant of a material on a circuit board, and the conductor is smaller when being far away from the dielectric constant of the glass fiber, so that the working efficiency is better).

It should be noted that the purposes of the second dielectric layer 401, the seventh dielectric layer 901, the third dielectric layer 501, and the sixth dielectric layer 801 including the flat open-fiber balance woven glass cloth are: multiple layers of glass fibers are arranged between the first, second and third wire layers (for example, the second dielectric layer 401 and the third dielectric layer 501 are arranged between the first wire layer 101 and the second wire layer 110, and the sixth dielectric layer 801 and the seventh dielectric layer 901 are arranged between the second wire layer 110 and the third wire layer 120), because the multiple layers of glass fibers can lead the glass to be distributed more uniformly under the superposition effect, and the generated glass fiber effect is smaller (namely, the dielectric constant change is more gradual) than that of a single layer. And the second dielectric layer 401 and the seventh dielectric layer 901 are further filled with low-temperature co-fired ceramic particles with low dielectric constant as a combined layer, and the dielectric constant distribution on the circuit board material is more uniform by the additional material, so that the influence of the glass fiber effect under high frequency is reduced.

Specifically, as shown in fig. 2-3, the fourth dielectric layer 601 and the fifth dielectric layer 701 are low-temperature co-fired ceramic particles and modified resin composite layers. The fourth dielectric layer 601 and the fifth dielectric layer 701 serve as two dielectric layers containing the flat open-fiber balance woven glass cloth, and a transition layer between the two dielectric layers and an intermediate wire layer (the second wire layer 110) provides a good transition effect through low-temperature co-fired ceramic particles.

Because, in actual production and transportation, the flat open-fiber balance woven glass cloth is difficult to avoid deformation, and knuckle intersection areas (areas with relatively more glass fibers) and bundle opening areas (areas with relatively less glass fibers) generated by deformation can cause uneven transition of dielectric constants on a horizontal plane, and the knuckle intersection areas have higher dielectric constants than the bundle opening areas. Here, in addition to the relief by providing a plurality of glass cloths (relief is achieved by superposition), the dielectric constant distribution is further balanced by a plurality of dielectric layers (the second dielectric layer 401, the fourth dielectric layer 601) containing low-temperature co-fired ceramic particles, which act on the first wire layer 101, the second wire layer 110.

As shown in fig. 3, in the third dielectric layer 501, a first connection layer 510, a first middle layer 520, and a first connection layer 510 are sequentially arranged from top to bottom, where the first connection layer 510 is an improved resin layer, and the first middle layer 520 is a mixed layer of the improved resin layer and a flat open-fiber balance woven glass cloth;

the sixth dielectric layer 801 sequentially comprises a second connection layer 810, a second intermediate layer 820 and a second connection layer 810 from top to bottom, wherein the second connection layer 810 is an improved resin layer, and the second intermediate layer 820 is a mixed layer of the improved resin layer and flat open-fiber balance woven glass cloth;

the thickness of the first connection layer 510 is less than or equal to the thickness of the first intermediate layer 520, and the thickness of the second connection layer 810 is less than or equal to the thickness of the second intermediate layer 820.

When the third dielectric layer 501 and the sixth dielectric layer 801 are formed as a whole, the thicknesses of the third dielectric layer 501 and the sixth dielectric layer 801 are consistent with those of other layers, so that the mechanical properties of the third dielectric layer 501 and the sixth dielectric layer 801 are not greatly different; the thickness of the first and second connection layers is very thin, which is used as a connection, and the difference of mechanical characteristics generated by the connection is very small, but the connection can be smoothly transited to the dielectric layers (such as the second dielectric layer 401 and the fourth dielectric layer 601) containing low-temperature co-fired ceramic particles at the upper side and the lower side, so that the reliability is improved, the influence on the conductor on the line layer (such as the second line layer 110) is avoided, the surface roughness of the conductor is avoided, and the influence on the circuit performance caused by the surface roughness of the conductor on the material surface of the circuit board under the small wavelength is further reduced, such as: phase response and insertion loss.

It should be noted that, the circuit board is processed by laser drilling, and the micro holes 301 are punched, so that the processing of the micro holes 301 is ensured to have high consistency. The radio frequency chip, the antenna, the matched wiring, the resistor, the capacitor and other components arranged on the circuit board are the conventional common technology. And will not be described in detail herein. The main circuits and components on the circuit board are mainly connected to the third wire layer 120, for example: a coil for wireless charging is disposed on the third wire layer 120.

And the antenna is mounted through the base 130, so that the antenna is prevented from being directly mounted on the first dielectric layer 201, and the direct mounting is easy to cause tearing of the first dielectric layer 201 and has low connection strength; the base 130 is generally fixedly connected to the first wire layer 101, so that the bottom surface of the base is not provided with a shielding layer, and therefore, the shielding layer is disposed on the bottom surface of the mounting groove 131 in the base 130, the base 130 also plays a certain role in isolation, and the antenna is electrically connected to the first wire layer 101 through the connection terminal 132. The radio frequency chip is arranged away from the antenna, so that the mutual influence between the high-frequency millimeter wave and the high-speed digital circuit is avoided, the circuit board is prevented from being heated and concentrated on a single side surface, and the circuit board is prevented from being bent due to thermal expansion under long-time use, so that the flat open-fiber balance woven glass cloth is prevented from being further broken.

In summary, (dielectric constant: dk) the present invention connects the first wire layer 101 and the first dielectric layer 201 together by smart layout, and makes the thicknesses of the wire layer and the dielectric layer uniform after combination, so that the mechanical properties of each layer keep relatively uniform in material thickness, and makes the mechanical properties of each layer approach the same under the influence of millimeter wave frequency by the uniformity of the thickness, so as to obtain a uniform thickness in performance and economy, and avoid the influence caused by non-uniformity of the mechanical properties, such as: the difference of phase response and insertion loss is caused, and the stability of the transmission line performance is obtained; the first line layer and the second line layer are provided with two dielectric layers containing flat open-fiber balance woven glass cloth, the distribution of glass fibers is more even through the multi-layer flat open-fiber balance woven glass cloth, the influence of glass fiber effect on the line board along with the increase of frequency or at higher digital speed is reduced, the DK value of the same transmission line passing place cannot generate quite large performance difference, and the Dk on the circuit board material becomes more even through the low-temperature cofired ceramic particle layer matched with the low Dk, so that the influence caused by the glass fiber effect under high frequency is reduced. The flat open-fiber balance woven glass cloth is characterized in that the thickness density ratio of glass yarns on a X, Y shaft is 1 (in ideal state, a certain redundant space is actually reserved), and knuckle intersection areas (areas with relatively more glass fibers) and bundle opening areas (areas with relatively less glass fibers) on the glass cloth in a weaving mode and specification are fewer, so that the abrupt change range of Dk values is fewer; the conductor on the wire layer can obtain a relatively ideal antenna efficiency and improve the stability under the high-frequency state under the condition of not being far away from the glass fiber, so that the distortion of the wire is lower. The practical value of the invention is greatly improved.

The foregoing examples are merely representative of one or more embodiments of the present invention and are described in more detail and are not to be construed as limiting the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of the invention should be assessed as that of the appended claims.

Claims

1. A high-frequency millimeter wave low-distortion hybrid circuit board, comprising: a circuit board, the circuit board comprising: the circuit board is provided with a plurality of micropores, the micropores are used for connecting the first line layer with the second line layer or the third line layer, and the micropores are used for connecting the second line layer with the third line layer;

the base is arranged on the upper side of the first dielectric layer, an installation groove is formed in the base, another shielding layer is arranged on the bottom surface of the installation groove, and a wiring terminal is arranged at the edge of the base;

the antenna is fixedly arranged in the mounting groove;

2. The high-frequency millimeter wave low-distortion hybrid circuit board according to claim 1, wherein the fourth dielectric layer and the fifth dielectric layer are low-temperature co-fired ceramic particles and modified resin composite layers.

3. The high-frequency millimeter wave low-distortion hybrid circuit board according to claim 1, wherein a first connecting layer, a first intermediate layer and a first connecting layer are sequentially arranged in the third dielectric layer from top to bottom, the first connecting layer is an improved resin layer, and the first intermediate layer is a hybrid layer of the improved resin layer and flat open-fiber balance woven glass cloth;

4. The high-frequency millimeter wave low-distortion hybrid circuit board according to claim 3, wherein the thickness of said first connection layer is less than or equal to the thickness of said first intermediate layer, and the thickness of said second connection layer is less than or equal to the thickness of said second intermediate layer.

5. The high-frequency millimeter wave low-distortion hybrid circuit board according to claim 1, wherein said circuit board is processed by laser drilling, and said micro-holes are punched.