CN204887693U - Prepreg sandwich structure for circuit substrate and circuit substrate and printed circuit board prepared therefrom - Google Patents

Abstract

The utility model relates to a circuit substrate, printed circuit board that circuit substrate used preimpregnation sandwich structure and was prepared by it, circuit substrate used preimpregnation sandwich structure's structure from the top down is the thin layer + the same or close resin layer + the reinforcing material layer + the same or close resin layer + the thin layer with reinforcing material DK in proper order.

Description

Prepreg sandwich structure for circuit substrate and circuit substrate and printed circuit board prepared therefrom

technical field

The utility model relates to the technical field of electronic materials, and relates to a prepreg sandwich structure for circuit substrates, in particular to a microscopically uniform and isotropic prepreg sandwich structure for circuit substrates, more specifically to a medium A prepreg sandwich structure is used for circuit substrates with little difference in electrical constant between warp and weft directions.

Background technique

In recent years, with the development of electronic products in the direction of multi-function and miniaturization, the circuit boards used are developing in the direction of multi-layer, high-density wiring and high-speed signal transmission. , such as the comprehensive performance of copper clad laminates put forward higher requirements. Specifically, the dielectric constant (Dk) and dielectric loss (Df) of the medium are important indicators that affect the signal transmission speed and signal quality. For the transmission speed, the lower the dielectric constant value of the dielectric material, the faster the signal transmission speed; for the signal integrity, due to the dielectric loss characteristics of the material, the signal is lost during transmission, and with the The transmission frequency and the length of the transmission line increase sharply. For the substrate, the signal integrity is mainly related to the dielectric loss of the dielectric material and the surface roughness of the copper foil conductor. The lower the dielectric loss of the dielectric material, the lower the transmission loss of the signal. The smaller it is, especially in the case of high frequency and long link transmission.

At the same time, with the development of high-performance, high-functionality and networking of information and communication equipment, in the era of cloud computing and big data, the data transmission rate will become higher and faster. The data transmission rate has risen from the traditional 5Gbps to 10Gbps, and even 25Gbps. When the data transmission rate is getting higher and higher, the transmission wavelength of digital signals is getting shorter and shorter. When the transmission rate is low, due to the long transmission wavelength of the digital signal, the signal delay has little influence on the integrity of the signal; but when the transmission rate is higher than 10Gbps, the signal delay becomes a must be considered in the high-speed transmission link question.

As one of the carriers for communication equipment to transmit signals - copper clad laminate plays a key role in signal transmission, and the laminate material used as a transmission medium determines the quality of signal transmission. At present, copper-clad laminate materials are generally obtained by using electronic-grade glass fiber cloth as a reinforcing material, impregnated with thermosetting resin, dried, laminated, and hot-pressed. Due to the use of woven materials as reinforcing materials (such as glass fiber cloth), the woven fiber cloth is caused by weaving and the existence of cross nodes at the intersection of woven fibers, so that the insulating medium (such as glass components) in the circuit substrate is not evenly distributed.

To solve this problem, it is fundamentally necessary to obtain a uniform dielectric material in the plane direction. The main technical means include (1) increasing the degree of fiber opening of the glass fiber cloth; (2) replacing the fiber braided material with a membrane-shaped reinforcing material; (3) Use reinforcing materials with lower dielectric constants, such as low dielectric constant glass fiber cloth. Although the glass fiber cloth is further uniformed by opening fibers, due to the weaving process and structure of the glass fiber cloth, it can only be uniform in the weft direction, and it can only be compared with the traditional non-opening direction in the warp direction. The fiber cloth is looser and cannot be completely opened and homogenized, which leads to the inability of the glass fiber cloth to achieve complete uniformity in the plane direction; it is very difficult to implement the process in the form of a film: operation Poor, poor bonding with resin, easy to delaminate; by using low dielectric constant glass fiber cloth, the dielectric constant of the reinforcing material can be reduced to a certain extent, but it is still different from the low dielectric constant resin composition currently used. Large, unable to meet the uniformity of dielectric constant in the plane direction.

So far, in order to adapt to the technical requirements of high-speed communication on copper-clad laminate materials, those skilled in the art are committed to reducing their dielectric constant and dielectric loss through various technical means, generally through two aspects: Traditional epoxy resins are replaced by modified epoxy resins, cyanate resins, bismaleimide resins, polyphenylene ether resins, hydrocarbon resins, and thermoplastic materials such as polytetrafluoroethylene and liquid crystal resins. These resin materials It has very low dielectric constant and dielectric loss characteristics, which can provide better high-speed transmission characteristics. In addition, the dielectric constant and dielectric loss of the copper-clad laminate material can also be reduced by changing the reinforcing material. Since the existing general reinforcing material is electronic-grade glass fiber cloth (E-type glass fiber cloth), the dielectric constant itself It is 6.2-6.6, which is much higher than the dielectric constant of the resin part used. The Dk of the copper clad laminate material produced in this way is generally between 3.5 and 4.5. In order to further reduce the dielectric constant of the laminate material, industry technology The staff also proposed to use low dielectric constant glass fiber cloth to replace traditional electronic grade glass fiber cloth. Since the Dk of low dielectric constant glass fiber cloth is 4.4-4.6, it can greatly reduce the dielectric constant of the entire laminate material, which can effectively Increase the transmission rate of the signal. In addition, because its dielectric loss (Df) value is lower than that of electronic-grade glass fiber cloth, it is also beneficial to improve the loss of the signal transmission process, and significantly improve the signal integrity due to the increase in signal transmission rate and frequency. sexual issues.

According to the foregoing, it can be seen that the copper clad laminate material includes two essential components: resin composition and reinforcement material. It is not difficult to see from the microstructure that the copper clad laminate material composed of the resin composition and the reinforcement material has a high Dk at the place where the warp and weft yarns are interwoven due to the inhomogeneity of the weave structure of the reinforcement material. The Dk is relatively high where there are warp or weft yarns, and the Dk is low where there is no yarn. This unevenness leads to microscopic differences in the dielectric constant of the dielectric layer.

The transmission time of the signal is determined by the transmission speed and the transmission distance. When the transmission distance is the same, the transmission speed is inversely proportional to the dielectric constant of the transmission medium. Due to the microscopic difference in the dielectric constant of the surrounding medium corresponding to the transmission line, it directly leads to The timing of the signal from the sending end to the receiving end is inconsistent, resulting in signal mismatch, that is, the delay effect. The signal delay is divided into warp signal delay and latitudinal signal delay. The warp signal delay refers to the signal delay when the transmission line is routed in the warp direction of the circuit substrate. Signal delay when routing in the weft direction.

To sum up, with the continuous improvement of data transmission rate, the delay problem has become a problem that must be faced for signal transmission in high-speed links. At present, some design methods can be used to reduce the delay. However, it will bring about a large increase in cost. Therefore, how to start from the dielectric material itself, improve the microscopic uniformity of the dielectric material—the laminate, and fundamentally solve the problem of signal delay has become a high-speed material technology research. important technical issue.

However, as mentioned above, due to the structural characteristics of the current reinforcement materials, the inhomogeneity of the plane direction of the laminate material is caused, resulting in anisotropic dielectric constant and dielectric loss of the laminate material on the microstructure, and in There are also huge differences in the microcosm of different places in the same plane direction. During the design process of high-speed digital circuits, engineers have taken various measures to solve signal integrity problems, and the method of using differential lines to transmit high-speed digital signals is one of them. The differential line in the PCB is a coupled stripline or a coupled microstrip line. When the signal is transmitted on it, it is an odd-mode transmission mode. Therefore, the differential signal has the advantages of strong anti-interference and easy matching. With the improvement of people's requirements for the information transmission rate of digital circuits, the differential transmission mode of signals will be more and more widely used. The main advantages of differential lines are: strong anti-interference ability, effective suppression of electromagnetic interference, accurate timing positioning, etc. , so the use of differential lines to transmit high-speed signals, on the one hand, is of great benefit to the signal integrity and low power consumption of the PCB system, on the other hand, it also puts forward higher requirements for the PCB design level.

Chinese patent CN102548200A discloses a circuit substrate, including a glass film that has been roughened to form a rough layer, resin adhesive layers located on the rough layers on both sides of the glass film, and metal foil located outside the resin adhesive layer , the glass film, the resin adhesive layer and the metal foil are combined together by pressing. The glass film is easy to break when pressed; and the surface roughening process of the glass film is cumbersome and difficult to control. At the same time, the roughening treatment will destroy the isotropic characteristics of the glass film to a certain extent; The process is different from the conventional copper clad laminate production process, and equipment modification and adjustment are required.

European patent EP1140373A first impregnates glass fiber cloth with a solution containing a curable resin with a relatively low solid content, then impregnates it with a solution containing a curable resin with a relatively high solid content after drying, and finally solidifies it. Reduce the solid content of the resin solution to increase the solvent content and reduce the viscosity, the purpose is to increase the permeability of the resin, to reduce the number of voids in the prepreg and cured products, but how to reduce Dk and solve the signal delay problem is not mentioned.

Chinese patent CN101494949A discloses that before the gluing process of the glass cloth, fiber opening or flattening is performed on the glass cloth, and then the insulating material layer is obtained by dipping in the epoxy resin glue solution and drying to reduce the copper clad substrate. Signal loss, increased signal propagation speed and reduced production costs.

Chinese patent CN101570640B discloses that quartz glass cloth with sparse density of quartz glass fibers (preferably fiber-opened) is used as the base material, impregnated with a thermosetting resin composition with a dielectric loss of less than 0.003 to prepare a prepreg, which is applied to high-frequency materials to ensure dielectric strength. While improving the electric constant, improve the processing performance.

Chinese patent CN201410016714 discloses a method for preparing an adhesive sheet constituting a circuit substrate, comprising the following steps: (1) preparing a pretreatment glue whose dielectric constant (Dk) is the same or close to the Dk of the reinforcing material used; (2) pre-dipping the reinforcing material in the pre-treatment glue solution, and then drying the solvent to obtain a pre-treated reinforcing material; (3) performing main dipping of the pre-treatment reinforcing material, and then drying Dry the solvent to make a bonded sheet. This solution can effectively solve the problem of signal delay in the plane direction of the circuit substrate, that is, the warp and weft directions, but it needs to be dipped twice, the process is more complicated, the single weight control level of the bonding sheet is general, and the thickness of the pressed circuit substrate is uniform Average sex.

At present, there is an urgent need for circuit substrates and printed circuit boards that can solve the problem of signal delay in the plane direction, that is, the warp and weft directions, and have simple processes and good thickness uniformity.

Utility model content

The utility model provides a prepreg sandwich structure body for a circuit substrate, and a circuit substrate and a printed circuit board produced by using the structure. The circuit substrate and printed circuit board made of this prepreg sandwich structure have excellent dielectric properties, and the difference between the dielectric constant in the warp direction and the weft direction is very small, and the microscopic consistency of the dielectric constant is realized, and the process is simple. The uniformity of sheet thickness is effectively improved.

One of the purposes of this utility model is to provide a prepreg sandwich structure, its structure from top to bottom is a film layer + a resin layer that is the same as or similar to the reinforcing material DK + a reinforcing material layer + a layer that is the same or similar to the reinforcing material DK Resin layer + film layer.

In one embodiment, the reinforcing material is electronic-grade glass fiber cloth, glass fiber non-woven fabric, aramid or other organic fiber woven cloth for circuit substrates.

In one embodiment, the resin layer that is the same as or similar to the reinforcing material DK includes epoxy resin system, cyanate resin system, polyphenylene ether resin system, polybutadiene resin system, polybutadiene and styrene Copolymer resin system, polytetrafluoroethylene resin system, polybenzoxazine resin system, polyimide system, silicone resin system, bismaleimide resin system, liquid crystal polymer system, bismaleimide One or more of the amine triazine resin system and the thermoplastic resin system; preferably, the resin layer further includes a filler selected from the group consisting of silica, alumina, titanium dioxide, barium titanate, strontium titanate, One or more of magnesium titanate, calcium titanate, barium strontium titanate, lead titanate, and glass powder.

In one embodiment, the total thickness of the resin layer that is the same as or similar to the reinforcing material DK + the reinforcing material layer + the resin layer that is the same as or similar to the reinforcing material DK / the thickness of the reinforcing material = 1.01 to 1.5; preferably the The total thickness of the resin layer that is the same as or similar to the reinforcing material DK+the reinforcing material layer+the resin layer that is the same or similar to the reinforcing material DK/thickness of the reinforcing material=1.05˜1.2.

In one embodiment, the resin layer included in the film layer has a thickness of 5 um to 100 um.

In one embodiment, the glass fiber cloth is an E-type glass fiber cloth, and its Dk (10 GHz) is 6.2-6.6.

In one embodiment, the glass fiber cloth is NE type glass fiber cloth, and its Dk (10 GHz) is 4.4-4.6.

The second purpose of this utility model is to provide a circuit substrate made of the above-mentioned prepreg sandwich structure. In one embodiment, one or more of the prepreg sandwich structures are stacked and assembled, and then Copper foil is coated on one or both sides of the circuit board, and sent to a press for hot pressing to obtain a circuit substrate.

The third purpose of the present utility model is to provide a printed circuit board made of the above-mentioned prepreg sandwich structure.

The fourth object of the present utility model is to provide a printed circuit board made of the above-mentioned circuit substrate.

The beneficial effects of the utility model are: the circuit substrate and the printed circuit board made of the prepreg sandwich structure have excellent dielectric properties, and the difference between the dielectric constant in the warp direction and the weft direction is very small, and the dielectric constant is realized. Microcosmic consistency; and the manufacturing process is simple, and the thickness uniformity of the circuit substrate and the printed circuit board is good.

Description of drawings

Fig. 1 is a schematic structural view of the prepreg sandwich structure of the present invention.

1. Reinforcement material; 2. Resin layer; 3. Film layer.

Detailed ways

The utility model provides a prepreg sandwich structure, and a circuit substrate and a printed circuit board produced by using the structure. The circuit substrate and printed circuit board made of this prepreg sandwich structure have excellent dielectric properties, and the difference between the dielectric constant in the warp direction and the weft direction is very small, and the microscopic consistency of the dielectric constant is realized, and the process is simple. The uniformity of sheet thickness is effectively improved.

One of the purposes of this utility model is to provide a prepreg sandwich structure, the prepreg sandwich structure

It is: film layer + resin layer that is the same as or similar to reinforcing material DK + reinforcing material + resin layer that is the same as or similar to reinforcing material DK + film layer.

In order to achieve the above purpose, the following technical solutions are adopted:

(1) Prepare the resin composition glue, make the resin composition DK after the heat treatment of the glue is similar or the same as the reinforcing material;

(2) impregnating the reinforcing material in the glue solution, and then drying the solvent to obtain a prepreg;

(3) Cover the film on both sides of the prepreg.

In some embodiments, the glue solution is a glue solution obtained by dissolving a resin composition in an organic or inorganic solvent; the resin composition is a thermoplastic resin composition or a thermosetting resin composition; preferably, the glue solution also contains filler.

The resin layer that is the same as or similar to the reinforcing material DK means: the dielectric constant (Dk) of the resin layer obtained by heat treatment after the reinforcing material is dipped in the glue solution is within the range of Dk±10% of the reinforcing material, preferably, the The Dk of the resin layer is within the range of Dk±5% of the reinforcing material.

The heat treatment is determined according to the characteristics of the resin composition. If the resin composition is a thermoplastic resin composition, the heat treatment refers to heating the glue solution to remove the solvent; if the resin composition is a thermosetting resin composition, the heat treatment refers to After the glue is heated to remove the solvent, the curing reaction proceeds.

In the prepreg sandwich structure, the total thickness of the resin layer identical to or similar to the reinforcing material DK+the reinforcing material layer+the resin layer identical to or similar to the reinforcing material DK/thickness of the reinforcing material=1.01˜1.5. Preferably, the total thickness of the resin layer that is the same as or similar to the reinforcing material DK+the reinforcing material layer+the resin layer that is the same as or similar to the reinforcing material DK/thickness of the reinforcing material=1.05˜1.2.

In some preferred embodiments, the resin composition includes a resin and a curing agent, wherein the resin is selected from the group consisting of epoxy resin, cyanate resin, polyphenylene ether resin, polybutadiene resin, polybutadiene and styrene Copolymer resin, polytetrafluoroethylene resin, polybenzoxazine resin, polyimide, silicone resin, bismaleimide resin, liquid crystal polymer, bismaleimide triazine resin, thermoplastic resin One or more in; The curing agent is selected from one or more of phenolic curing agent, amine curing agent, polymer anhydride curing agent, active ester, free radical initiator; Preferably, the The resin layer also includes a filler, which is selected from one of silicon dioxide, aluminum oxide, titanium dioxide, barium titanate, strontium titanate, magnesium titanate, calcium titanate, barium strontium titanate, lead titanate, and glass powder. one or more species.

In some preferred embodiments, the film is an organic film, including polyester film, polyamine film, polyacrylic film, polyimide film, aramid film, polytetrafluoroethylene film, syndiotactic polystyrene film one or more of .

In some preferred embodiments, the reinforcing material is electronic-grade glass fiber cloth, glass fiber non-woven fabric, aramid or other organic fiber woven cloth for circuit substrates; more preferably, the reinforcing material is electronic-grade glass fiber cloth.

In other preferred embodiments, the glass fiber cloth is E-type glass fiber cloth, and its (10 GHz) range is 6.2-6.6.

In some other preferred embodiments, the glass fiber cloth is NE type glass fiber cloth, and its Dk (10 GHz) is 4.4-4.6.

The second purpose of the present utility model is to provide a circuit substrate prepared according to the prepreg sandwich structure.

One or more prepreg sandwich structures are stacked and combined, and then one or both sides of the stacked combination are coated with RCC or copper foil, and sent to a press for hot pressing to obtain a circuit substrate.

The third object of the present utility model is to provide a printed circuit board prepared according to the circuit substrate.

The above prepreg sandwich structure is directly used in the production of printed circuit boards.

The fourth objective of the present utility model is to provide a printed circuit board made according to the circuit substrate.

The above-mentioned circuit substrate made of the prepreg sandwich structure was used for the production of printed circuit boards.

The Dk used in the utility model refers to the dielectric constant, which is the value tested by the SPDR method at a frequency of 10 GHz.

The glass fiber cloth used in this utility model refers to glass fiber cloth, referred to as glass fiber cloth, glass fiber cloth includes E type glass fiber cloth, NE type glass fiber cloth, S type glass fiber cloth, D type glass fiber cloth and other types, each This type of glass fiber cloth can be divided into 7628, 2116, 1080, 106, 1037, 1078, 2112, 3313, 1500 and other specifications and models. Those skilled in the art know that when glass fiber cloth is used in the field of circuit substrates, its main function It is used as a reinforcing material for circuit substrates.

The so-called prepreg in this utility model refers to the reinforced material obtained by heat treatment after immersion in the resin composition glue, and its structure is the same or similar to the reinforced material DK resin layer+reinforced material layer+and reinforced Resin layers with the same or similar material DK.

The technical scheme of the utility model is further illustrated below through the examples.

Example 1:

Prepreg sandwich structure: PTFE film + prepreg (the reinforcement material is E-type 1080 glass fiber cloth, its Dk is 6.6; the resin system is epoxy system, its Dk is 6.5) + PTFE film

Circuit substrate production method: copper foil + 2*prepreg sandwich structure + copper foil

Example 2:

Prepreg sandwich structure: PTFE film + prepreg (the reinforcement material is NE type 2116 glass fiber cloth, its Dk is 4.6; the resin system is cyanate ester system, its Dk is 4.4) + PTFE film

Circuit substrate production method: copper foil + 1*prepreg sandwich structure + copper foil

Example 3:

Prepreg sandwich structure: PI film + prepreg (the reinforcement material is E-type 50 non-woven fabric, its Dk is 6.6; the resin system is epoxy system, its Dk is 6.5) + PI film

Circuit substrate production method: copper foil + 2*prepreg sandwich structure + copper foil

Comparative example 1:

Prepreg sandwich structure: PTFE film + prepreg (the reinforcement material is E-type 1080 glass fiber cloth, its Dk is 6.6; the resin system is epoxy system, its Dk is 3.8) + PTFE film

Circuit substrate production method: copper foil + 2*prepreg sandwich structure + copper foil

The resin layer DK in the epoxy prepreg in Comparative Example 1 is 3.8, the resin layer in Example 1 is 6.5, and the others are the same as Example 1; compared with Example 1, the signal delay phenomenon is obvious.

Comparative example 2:

Secondary dipping structure: prepreg (reinforcement material is E-type 1080 glass fiber cloth, its Dk is 6.6; resin system is epoxy system, its Dk is 6.5) the structure made by secondary dipping.

Circuit substrate production method: copper foil + 2* epoxy prepreg secondary dipping structure + copper foil

The resin layer DK in the prepreg in Comparative Example 2 is 6.5, and the impregnation resin is an epoxy system; compared with Example 1, this process can also obviously improve the signal delay problem, but the epoxy prepreg needs to be Re-dipping, then drying and semi-curing to make impregnated sheets, the process is more complicated, and the range of the pressed plates is larger.

The technical principles of the present utility model are described above in conjunction with specific embodiments. These descriptions are only for explaining the principles of the present utility model, and cannot be interpreted as limiting the protection scope of the present utility model in any way. Based on the explanations herein, those skilled in the art can think of other specific implementation modes of the present utility model without creative work, and these modes will all fall within the protection scope of the present utility model.

Claims (12)

1. a circuit board use preimpregnation sandwich structure body, its structure is followed successively by thin layer, the resin bed identical or close with reinforcing material DK, layers of reinforcement, resin bed, the thin layer identical or close with reinforcing material DK from top to bottom.

2. preimpregnation sandwich structure body as claimed in claim 1, is characterized in that, described reinforcing material is the electronic-grade glass fiber cloth of circuit board use, glass fibre non-woven or aramid fiber.

3. preimpregnation sandwich structure body as claimed in claim 1, it is characterized in that, described film is the one in polyester film, polyamine film, polyacrylic film, polyimide film, aramid fiber film, polytetrafluoroethylene film, syndiotactic polytyrene film.

4. preimpregnation sandwich structure body as claimed in claim 1, it is characterized in that, the described resin bed identical or close with reinforcing material DK comprises the one in epoxy-resin systems, cyanate ester resin system, polyphenylene oxide resin system, polybutadiene system, polybutadiene and styrene copolymer resin system, polyflon system, Polybenzoxazine resin system, polyimides system, containing silicone resin system, bismaleimide resin system, polymerizable mesogenic objects system, bismaleimide-triazine resin system, thermoplastic resin system.

5. preimpregnation sandwich structure body as claimed in claim 4, it is characterized in that, described resin bed also comprises filler, and described filler is selected from the one in silica filler, alumina packing, titanium dioxide filler, barium titanate filler, strontium titanates filler, magnesium titanate filler, calcium titanate filler, barium strontium titanate filler, lead titanates filler, glass dust filler.

6. preimpregnation sandwich structure body as claimed in claim 1, is characterized in that, thickness=1.01 ~ 1.5 of the gross thickness/reinforcing material of the described resin bed identical or close with reinforcing material DK, layers of reinforcement, the resin bed identical or close with reinforcing material DK.

7. preimpregnation sandwich structure body as claimed in claim 6, is characterized in that, thickness=1.05 ~ 1.2 of the gross thickness/reinforcing material of the described resin bed identical or close with reinforcing material DK, layers of reinforcement, the resin bed identical or close with reinforcing material DK.

8. preimpregnation sandwich structure body as claimed in claim 1, it is characterized in that, the thickness of described thin layer is 5um to 200um.

9. preimpregnation sandwich structure body as claimed in claim 1, it is characterized in that, described reinforcing material is E type glass-fiber-fabric, and its Dk under 10GHz is 6.2 ~ 6.6.

10. preimpregnation sandwich structure body as claimed in claim 1, it is characterized in that, described reinforcing material is NE type glass-fiber-fabric, and its Dk under 10GHz is 4.4 ~ 4.6.

11. 1 kinds of circuit substrates, is characterized in that, it is covered with Copper Foil at the single-side/double-side of one or folded multiple preimpregnation sandwich structure bodies according to any one of claim 1-10 of joining.

12. 1 kinds of printed circuit boards, is characterized in that, it is made up of the preimpregnation sandwich structure body according to any one of claim 1-10 or circuit substrate according to claim 11.