Preparation method of high-performance halogen-free low-loss copper-clad plate

Abstract

This invention relates to a method for preparing high-performance halogen-free, low-loss copper-clad laminates, belonging to the field of copper-clad laminate manufacturing technology. Step 1: Preparation of adhesive for electronic fiberglass cloth: By weight percentage, 14-16% polymaleimide resin, 6-10% bismaleimide resin, 4-6% phenol-biphenyl epoxy resin, 7-10% double-bond benzoxazine resin, 5-8% phosphate ester, 4-6% styrene-maleic anhydride resin, 0.01-0.1% curing accelerator, 28-31% inorganic filler, 0.3-1.0% wetting and dispersing agent, and 24-30% organic solvent; Step 2: Preparation of fiberglass cloth prepreg: The adhesive for electronic fiberglass cloth is uniformly coated onto the surface of the electronic fiberglass cloth, and baked in a dryer at 160-210℃. The adhesive content of the prepreg is controlled to be 46±2%, and the flowability is 10-20%, thus obtaining the fiberglass cloth prepreg. Step 3: Preparation of FR-4 copper-clad laminate. This application combines environmental friendliness, high heat resistance, low dielectric loss, and good processability.

Description

Technical Field

[0001] This invention relates to a method for preparing high-performance halogen-free, low-loss copper-clad laminates, belonging to the field of copper-clad laminate manufacturing technology. Background Technology

[0002] With the rapid development of fifth-generation mobile communication (5G), high-performance computing, automotive radar, and satellite communication, the signal transmission rate and frequency requirements of printed circuit boards (PCBs), as the core interconnect components of electronic devices, continue to rise. Copper-clad laminates (CCLs), as the basic material for PCBs, directly determine the integrity and efficiency of signal transmission due to their dielectric properties. Traditional FR-4 CCLs, due to their epoxy-glass fiber system, typically have a dielectric constant (Dk) higher than 4.5 and a dielectric loss factor (Df) higher than 0.015, making it difficult to meet the stringent requirements of low latency and low attenuation in high-frequency, high-speed scenarios.

[0003] To improve high-frequency performance, existing technologies have attempted to use novel resin systems such as polyphenylene ether (PPE), bismaleimide (BMI), or liquid crystal polymer (LCP). However, these systems generally suffer from the following problems: First, while PPE systems offer excellent dielectric properties, their heat resistance and dimensional stability are insufficient, making it difficult to meet the thermal stress requirements during multilayer board processing. Second, while traditional BMI resins exhibit outstanding heat resistance, their high crystallinity, poor solubility, and narrow molding process window make industrial production challenging. Third, many high-performance systems introduce halogenated flame retardants to enhance flame retardancy, which does not comply with increasingly stringent environmental regulations. Fourth, there is an inherent contradiction between high-frequency performance and heat resistance reliability. While high crosslinking density is beneficial for increasing the glass transition temperature (Tg) and thermal decomposition temperature (Td), it often leads to increased internal stress and dielectric loss.

[0004] Therefore, how to achieve halogen-free flame retardancy, high heat resistance, low thermal expansion, low dielectric loss and excellent process adaptability in the same material system is a technical challenge that urgently needs to be overcome. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing high-performance halogen-free low-loss copper clad laminates, which solves the technical problem that high-frequency copper clad laminates in the prior art are difficult to achieve in a balance of environmental protection, high heat resistance, low dielectric loss and good processing adaptability.

[0006] The technical solution adopted by the present invention to solve the above problems is: a method for preparing a high-performance halogen-free, low-loss copper-clad laminate, the preparation method comprising the following steps: Step 1: Preparation of adhesive for electronic fiberglass cloth: by weight percentage, 14-16% polymaleimide resin, 6-10% bismaleimide resin, 4-6% phenol-biphenyl epoxy resin, 7-10% double-bond benzoxazine resin, 5-8% phosphate ester, 4-6% styrene-maleic anhydride resin, 0.01-0.1% curing accelerator, 28-31% inorganic filler, 0.3-1.0% wetting and dispersing agent, and 24-30% organic solvent; a. Add the organic solvent, double-bonded benzoxazine resin, wetting and dispersing agent, and phosphate ester to the stirred tank, start stirring to fully dissolve them, control the temperature inside the tank at 20-40℃, and stir for 60-90 minutes; b. Continue to add the dissolved polymaleimide resin, styrene maleic anhydride resin, curing accelerator and inorganic filler into the reactor, and stir continuously for 90-120 minutes to make it evenly mixed. Then turn on the high-efficiency shearing and emulsification to obtain the adhesive solution for electronic glass fiber cloth. Step 2: Preparation of fiberglass cloth semi-cured sheet: The electronic fiberglass cloth is uniformly coated with adhesive and baked in a dryer at 160-210℃. The adhesive content of the semi-cured sheet is controlled to be 46±2% and the flowability is 10-20%, thus obtaining the fiberglass cloth semi-cured sheet.

[0007] Step 3: Fabrication of FR-4 copper-clad laminate Copper foil is applied to both sides of a fiberglass cloth prepreg and then pressed at 0.8-3.0 MPa and 80-235℃ for 240-260 min. Then, it is cold-pressed at 1.3-1.6 MPa for 50-60 min to obtain FR-4 copper-clad laminate.

[0008] The polymaleimide resin is a low-melting-point polymaleimide resin, which has good solubility in a DMF / MEK=1:1 mixed solvent and an acid value of 2.35 mg KOH / g.

[0009] The bismaleimide resin is a low-crystallinity bismaleimide resin with a DSC melting point of 167.2℃, an acid value of 0.52 mg KOH / g, and a purity ≥98.1 wt%.

[0010] The phenol-biphenyl type epoxy resin has an epoxy equivalent of 280-300 g / eq, a viscosity of 2.5-4.5 poise / 150℃ ICI, and a softening point of 65-75℃.

[0011] The double-bond benzoxazine resin has a solid content of 69-71% and a viscosity of 1200-1300 mPa·s; the styrene-maleic anhydride resin has an acid value of 141-171 mg KOH / g and a kinematic viscosity of 0.70-0.80 CST.

[0012] The phosphate ester is 1,3-phenylene phosphate tetraester or 2,6-xylyl phosphate, with a phosphorus content of 9.0%.

[0013] The inorganic filler is one of modified spherical silica powder or spherical silica powder, wherein the manufacturer of the modified spherical silica powder is Guangzhou Yushun New Material Technology Co., Ltd., and the model number is YS-QR3.

[0014] The organic solvent is one or any mixture of butanone, cyclohexanone, ethylene glycol monomethyl ether, and propylene glycol monomethyl ether.

[0015] The curing accelerator is 2-methylimidazole.

[0016] In step one, the adhesive used for the electronic fiberglass cloth has a solid content of 68-75%, a viscosity of 12-28s in a fourth cup, and a gelation time of 190-350s at 171℃.

[0017] Compared with existing technologies, the advantages of this invention are as follows: A method for preparing a high-performance halogen-free, low-loss copper-clad laminate. The copper-clad laminate obtained in this application exhibits outstanding thermal reliability, with T288 indicators characterizing lead-free soldering heat resistance all exceeding 60 min, a 5% thermogravimetric temperature reaching 428-434℃, and a glass transition temperature reaching 193-200℃; excellent dimensional stability, with a Z-axis thermal expansion coefficient as low as 1.28-1.35% within the 50-260℃ range; superior high-frequency dielectric properties, with a dielectric constant of 3.82-3.86 and a dielectric loss of only 0.006-0.007 at 10GHz using the resonant cavity method, maintaining stable low-loss characteristics across a wide frequency range; simultaneously, it possesses good interfacial adhesion and water resistance, with a peel strength of 1.53-1.56 N / mm for 1oz copper foil and a water absorption rate controlled at 0.09-0.11%. Furthermore, all samples meet the highest UL94-V0 flame retardant standard. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the cross-sectional microstructure of the copper-clad laminate obtained in Example 1; Figure 2 The Tg curve of the copper-clad laminate prepared in Example 1 is shown. Figure 3 The Tg curve of the copper-clad laminate obtained in Example 2 is shown. Figure 4 This is a graph showing the variation of Dk / Df at different frequencies in Example 1. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Example 1

[0020] The method for preparing a high-performance halogen-free, low-loss copper-clad laminate in this embodiment includes the following steps: Step 1: Preparation of adhesive for electronic fiberglass cloth: by weight percentage, 14.55% polymaleimide resin (100% solid content), 6.41% bismaleimide resin (100% solid content), 4.27% phenol-biphenyl epoxy resin (100% solid content), 7.34% double-bond benzoxazine resin (70% solid content), 4.71% styrene-maleic anhydride resin (SMA) (100% solid content), 5.46% phosphate ester, 0.0728% 2-methylimidazole, 29.10% spherical silica powder, 0.35% wetting and dispersing agent, 17.28% cyclohexanone and 10.46% methyl ethyl ketone.

[0021] a. Add methyl ethyl ketone, cyclohexanone, double-bonded benzoxazine resin, wetting and dispersing agent, and phosphate ester to a stirred tank, start stirring to dissolve them completely, control the temperature inside the tank at 30℃, and stir for 60 minutes. b. Continue to add appropriate amounts of polymaleimide resin, bismaleimide resin, styrene-maleic anhydride resin (SMA), 2-methylimidazole and spherical silica powder dissolved in methyl ethyl ketone to the reactor, stir continuously for 120 minutes to mix evenly, then turn on high-efficiency shearing twice and emulsify for 180 minutes to obtain the adhesive solution for electronic fiberglass cloth.

[0022] The final adhesive used for electronic fiberglass cloth has a solid content of 70%, a viscosity of 15s in the fourth cup, and a gelation time of 332s / 171℃.

[0023] Step 2: Preparation of fiberglass cloth semi-cured sheet: The electronic fiberglass cloth obtained in Step 1 is uniformly coated on both sides with adhesive. It is then baked for 90-120 seconds under the following process conditions: hot plate temperature in zone 1 is 185℃, hot plate temperature in zone 2 is 225℃, and machine speed is 12.4 m / min. A fiberglass cloth semi-cured sheet with an adhesive content of 46.2% and a flowability of 15.1% is obtained.

[0024] Step 3: Preparation of FR-4 copper clad laminate: 35 μm RTF2 low-profile reverse copper foil is coated onto both sides of the fiberglass cloth prepreg from Step 2. The laminate is then pressed at 0.8-3.0 MPa surface pressure and 80-235℃ for 250 min; subsequently, it is cold-pressed at 1.5 MPa surface pressure for 60 min to obtain the FR-4 copper clad laminate. The cross-sectional structure is shown below. Figure 1 As shown, the Tg curve Figure 2 As shown.

[0025] The performance of the obtained FR-4 copper clad laminate was tested, and the test results are shown in Table 2. Example 2

[0026] A method for preparing a high-performance halogen-free, low-loss copper-clad laminate includes the following steps: Step 1: Preparation of adhesive for electronic fiberglass cloth: by weight percentage, 14.55% polymaleimide resin (100% solid content), 6.41% bismaleimide resin (100% solid content), 4.27% phenol-biphenyl epoxy resin (100% solid content), 7.34% double-bond benzoxazine resin (70% solid content), 4.71% styrene-maleic anhydride resin (SMA) (100% solid content), 5.46% phosphate ester, 0.0728% 2-methylimidazole, 29.10% modified spherical silica powder, 0.35% wetting and dispersing agent, 17.28% cyclohexanone and 10.46% methyl ethyl ketone.

[0027] a. Add methyl ethyl ketone, cyclohexanone, double-bonded benzoxazine resin, wetting and dispersing agent, and phosphate ester to a stirred tank, start stirring to dissolve them completely, control the temperature inside the tank at 30℃, and stir for 60 minutes. b. Continue to add appropriate amounts of polymaleimide resin, bismaleimide resin, styrene-maleic anhydride resin (SMA), 2-methylimidazole and modified spherical silica powder dissolved in methyl ethyl ketone to the reactor, and stir continuously for 120 minutes to make it evenly mixed. Then turn on the high-efficiency shearing twice and emulsify for 180 minutes to obtain the adhesive solution for electronic fiberglass cloth.

[0028] The final adhesive used for electronic fiberglass cloth has a solid content of 70%, a viscosity of 19s in the fourth cup, and a gelation time of 337s / 171℃.

[0029] Step 2: Preparation of fiberglass cloth semi-cured sheet: The electronic fiberglass cloth obtained in Step 1 is uniformly coated on both sides with adhesive. It is then baked for 90-120 seconds under the following process conditions: hot plate temperature in zone 1 is 185℃, hot plate temperature in zone 2 is 225℃, and machine speed is 12.4 m / min. This yields a fiberglass cloth semi-cured sheet with an adhesive content of 46.2% and a flowability of 10.2%.

[0030] Step 3: Preparation of FR-4 copper clad laminate: The fiberglass cloth prepreg obtained in Step 2 is coated on both sides with 35μm RTF2 low-profile reverse copper foil, and pressed at 0.8-3.0MPa surface pressure and 80-235℃ for 250min; then, it is cold-pressed at 1.5MPa surface pressure for 60min to obtain the FR-4 copper clad laminate. (Tg curve) Figure 3 As shown.

[0031] The performance of the obtained FR-4 copper clad laminate was tested, and the test results are shown in Table 2. Example 3

[0032] A method for preparing a high-performance halogen-free, low-loss copper-clad laminate includes the following steps: Step 1: Preparation of adhesive for electronic fiberglass cloth: by weight percentage, 15.16% polymaleimide resin (100% solid content), 6.68% bismaleimide resin (100% solid content), 4.45% phenol-biphenyl epoxy resin (100% solid content), 7.65% double-bond benzoxazine resin (70% solid content), 4.91% styrene-maleic anhydride resin (SMA) (100% solid content), 5.69% phosphate ester, 0.0758% 2-methylimidazole, 30.32% spherical silica powder, 0.36% wetting and dispersing agent, 9.00% cyclohexanone and 15.68% methyl ethyl ketone.

[0033] a. Add methyl ethyl ketone, cyclohexanone, double-bonded benzoxazine resin, wetting and dispersing agent, and phosphate ester to a stirred tank, start stirring to dissolve them completely, control the temperature inside the tank at 30℃, and stir for 60 minutes. b. Continue to add appropriate amounts of polymaleimide resin, bismaleimide resin, styrene-maleic anhydride resin (SMA), 2-methylimidazole and spherical silica powder dissolved in methyl ethyl ketone to the reactor, and stir continuously for 120 minutes to make it evenly mixed. Then turn on the high-efficiency shearing twice and emulsify for 180 minutes to obtain the adhesive solution for electronic fiberglass cloth.

[0034] The final solid content of the adhesive used for electronic fiberglass cloth was 73%, the viscosity of the fourth cup was 19s, and the gelation time was 335s / 171℃.

[0035] Step 2: Preparation of fiberglass cloth semi-cured sheet: The electronic fiberglass cloth obtained in Step 1 is uniformly coated on both sides with adhesive. It is then baked for 90-120 seconds under the following process conditions: hot plate temperature in zone 1 is 185℃, hot plate temperature in zone 2 is 225℃, and machine speed is 12.4 m / min. This yields a fiberglass cloth semi-cured sheet with an adhesive content of 46.2% and a flowability of 14.2%.

[0036] Step 3: Preparation of FR-4 copper clad laminate: Cover both sides of the fiberglass cloth prepreg obtained in Step 2 with 35μm RTF2 low profile reverse copper foil, press at 0.8-3.0MPa surface pressure and 80-235℃ temperature for 250min; then cold press at 1.5MPa surface pressure for 60min to obtain FR-4 copper clad laminate.

[0037] The performance of the obtained FR-4 copper clad laminate was tested, and the test results are shown in Table 2. Example 4

[0038] A method for preparing a high-performance halogen-free, low-loss copper-clad laminate includes the following steps: Step 1: Preparation of adhesive solution for electronic fiberglass cloth: The adhesive for electronic fiberglass cloth, by weight percentage, comprises: 15.16% polymaleimide resin (100% solid content), 6.68% bismaleimide resin (100% solid content), 4.45% phenol-biphenyl epoxy resin (100% solid content), 7.65% double-bond benzoxazine resin (70% solid content), 4.91% styrene-maleic anhydride resin (SMA) (100% solid content), 5.69% phosphate ester, 0.0758% 2-methylimidazole, 30.32% modified spherical silica powder, 0.36% wetting and dispersing agent, 9.00% cyclohexanone, and 15.68% methyl ethyl ketone.

[0039] a. Add methyl ethyl ketone, cyclohexanone, double-bonded benzoxazine resin, wetting and dispersing agent, and phosphate ester to a stirred tank, start stirring to dissolve them completely, control the temperature inside the tank at 30℃, and stir for 60 minutes. b. Continue to add polymaleimide resin, bismaleimide resin, styrene-maleic anhydride resin (SMA), 2-methylimidazole and modified spherical silica powder dissolved in an appropriate amount of methyl ethyl ketone to the reactor, stir continuously for 120 minutes to make it evenly mixed, then turn on the high-efficiency shearing twice and emulsify for 180 minutes to obtain the adhesive solution for electronic fiberglass cloth.

[0040] The final solid content of the electronic fiberglass cloth adhesive was 73%, the viscosity was 23s in the fourth cup, and the gelation time was 340s at 171℃.

[0041] Step 2: Prepare a fiberglass cloth semi-cured sheet. The adhesive obtained in Step 1 is evenly coated on both sides of the electronic fiberglass cloth. The sheet is baked for 90-120 seconds under the following process conditions: hot plate temperature in zone 1 is 185℃, hot plate temperature in zone 2 is 225℃, and machine speed is 12.4 m / min. A fiberglass cloth semi-cured sheet with an adhesive content of 46.2% and a flowability of 10.1% is obtained.

[0042] Step 3: Preparation of FR-4 copper clad laminate: Cover both sides of the fiberglass cloth prepreg obtained in Step 2 with 35μm RTF2 low profile reverse copper foil, press at 0.8-3.0MPa surface pressure and 80-235℃ temperature for 250min; then cold press at 1.5MPa surface pressure for 60min to obtain FR-4 copper clad laminate.

[0043] The performance of the obtained FR-4 copper clad laminate was tested, and the test results are shown in Table 2.

[0044] Polymaleimide resin (BMI) specifically refers to polymaleimide resins with low melting points. It exhibits good solubility under DMF / MEK (1:1) conditions, with an acid value of 2.35 mg KOH / g. While retaining advantages such as heat resistance, its solubility and processability are improved through polymerization structure. Bismaleimide resin (BMI) specifically refers to bismaleimide resins with low crystallinity. Under DCS, 10℃ / min, and N2 conditions, it has a melting point of 167.2℃, an acid value of 0.52 mg KOH / g, and a content of 98.1 wt%. This type of resin successfully resolves the contradiction of ordinary bismaleimide resins having excellent performance but difficult molding, significantly improving processability with almost no sacrifice in heat resistance. Phenolic-biphenyl type epoxy resins have an epoxy equivalent of 280-300 g / eq, a viscosity of 2.5-4.5 poise / 150℃ ICI, and a softening point of 65-75℃.

[0045] The viscosity of double-bonded benzoxazine resin is 1200-1300 mPa·s. Styrene-maleic anhydride resin (SMA) has an acid value of 141-171 mg KOH / g and a kinematic viscosity of 0.70-0.80 CST. Under heating conditions, the maleic anhydride groups on the SMA molecular chain can undergo ring-opening esterification with the epoxy groups of epoxy resin, thereby achieving cross-linking and curing, increasing the cross-linking density, and further improving Tg and heat resistance (Td).

[0046] The wetting and dispersing agent is a polyester phosphate salt solution with a density of 1.06 g / ml at 20℃ and a non-volatile content (10 min, 150℃): 40%. It ensures that the high content of functional fillers can be stably supported in the complex resin system, so that the high heat resistance of BMI, the low dielectric of benzoxazine, and the flame retardancy of phosphate ester can be stably and uniformly reflected in the final board.

[0047] The phosphate ester is 1,3-phenylene phosphate tetra(2,6-dimethylyl) ester, with a phosphorus content of 9.0%.

[0048] The modified spherical silica powder mentioned above was purchased from Guangzhou Yushun New Material Technology Co., Ltd., and the model number is YS-QR3.

[0049] Examples 1-4 and Comparative Example 1 samples used different resin combinations and solid filler systems. The specific formulation components are detailed in Table 1, and the test results of various performances are summarized in Table 2.

[0050] Table 1

[0051] Table 2

[0052] In Comparative Example 1, no bismaleimide resin was added; only high-functionality polymaleimide resin was used as the sole crosslinking host, leading to a fundamental deterioration in the crosslinking structure of the system. The high-functionality polymaleimide resins added in Examples 1-4 exhibited rapid curing reaction rates and high crosslinking activity, forming a dense and highly unevenly distributed crosslinking network in a short time. This resulted in excessive concentration of crosslinking points, a significant shortening of the effective length of molecular chain segments, and a substantial accumulation of internal stress. Specific data comparisons are shown in Table 3.

[0053] Table 3

[0054] The modified spherical silica powder is grafted with a coupling agent that is compatible with the resin matrix, which can significantly improve the interfacial bonding force between inorganic fillers and organic resins. As a result, the Z-axis CTE is reduced by 3.7%-5.2%, the peel strength of copper foil is increased by 1.3%-1.9%, and the dimensional stability and interfacial bonding force are optimized.

[0055] The introduction of modified silica powder slightly decreases the system's Tg (approximately 5.8-6.3℃), but it remains above 193℃, fully meeting the requirements for high-frequency and high-speed boards. Simultaneously, the dielectric constant slightly increases, but the dielectric loss remains essentially the same or even improves (Df decreased to 0.006 in Example 4). The water absorption rate slightly increases, mainly due to the presence of a small amount of polar groups in the coupling agent molecules, but the overall water absorption remains below 0.13%, far lower than the 0.16% in Comparative Example 1.

[0056] Surface modification enhances the interaction between silicon powder and resin, increases the viscosity of the system, and reduces the flowability of the prepreg by about 4.5%-4.9%, but it is still within the acceptable range of 10%-20%, meeting the requirements for industrial pressing.

[0057] Examples 3-4, based on Examples 1-2, had their total resin content slightly adjusted and the mixed solvent ratio modified (cyclohexanone ratio decreased, butanone ratio increased). Performance comparison results showed that the Tg of Examples 3-4 was slightly lower than that of Examples 1-2 by approximately 1.2-1.7℃, but the thermal decomposition temperature Td and T288 heat resistance remained essentially the same. Dielectric properties were further optimized, especially in Example 4, where the dielectric loss decreased to 0.006, reaching the level of extremely low-loss copper-clad laminates. The adjustment of the solvent system improved the rheological properties of the adhesive and the uniformity of resin dispersion, resulting in a denser and more uniform crosslinked network after curing, and a more balanced overall performance.

[0058] The speed of the coating machine directly determines the production efficiency of prepreg; for every 1 m / min increase in speed, the daily output of a single line can increase by approximately 8%. When the machine speed exceeds 14 m / min, the flowability of the prepreg will exceed the upper limit of the acceptable process index of 20%, leading to problems such as excessive resin loss, uneven sheet thickness, and glue sticking during pressing, which seriously affects product yield and production stability. This application can stably produce qualified prepreg with a flowability of 15.1% at a machine speed of 12.4 m / min, offering a wide process window that balances production efficiency and product quality, making it suitable for large-scale industrial production.

[0059] This application introduces bismaleimide resin as a key functional component into a high-functionality polymaleimide system, constructing a "bifunctional-multifunctional gradient composite crosslinking framework." In this system, the bismaleimide resin is not simply a filler component, but rather a core functional component that regulates the microstructure of the crosslinking network, balances the rigidity and toughness of the material, and ensures comprehensive performance. It effectively alleviates the internal stress problem during the curing of high-functionality polymaleimide resin, constructing a uniform and stable three-dimensional crosslinking network. Based on this, surface-modified spherical silica powder is used to further optimize the interfacial bonding force between the inorganic filler and the organic resin. Simultaneously, a cyclohexanone-butanone mixed solvent system is used to ultimately prepare a high-frequency, high-speed copper-clad laminate with comprehensive and balanced performance.

[0060] Performance test data shows that the copper-clad laminate of this application exhibits outstanding thermal reliability, with T288 indicators characterizing lead-free soldering heat resistance all exceeding 60 minutes, a 5% thermogravimetric temperature reaching 428-434℃, and a glass transition temperature of 193-200℃. It also demonstrates excellent dimensional stability, with a Z-axis thermal expansion coefficient as low as 1.28-1.35% within the 50-260℃ range. Furthermore, it exhibits superior high-frequency dielectric properties, with a dielectric constant of 3.82-3.86 at 10GHz tested using the resonant cavity method, and a dielectric loss of only 0.006-0.007 (e.g., ...). Figure 4 As shown in the figure, it maintains stable low-loss characteristics over a wide frequency band; it also has good interfacial adhesion and water resistance, with a peel strength of 1.53-1.56 N / mm for 1 oz copper foil and a water absorption rate controlled at 0.09-0.11%. In addition, all samples meet the highest UL94-V0 flame retardancy standard.

[0061] Regarding process adaptability, while the use of surface-modified spherical silica powder slightly reduces the flowability of the prepreg, it remains within the acceptable range of 10%-20%. By using a cyclohexanone-butanone mixed solvent, the flowability of the prepreg can be precisely controlled, while simultaneously optimizing the rheological properties and curing uniformity of the adhesive, further improving the high-frequency dielectric properties of the material without sacrificing thermal reliability. The formulation of this application exhibits excellent industrial production adaptability, stably producing qualified prepregs at a reasonable machine speed of 12.4 m / min, with a wide process window, balancing production efficiency and product quality. Example 4 demonstrates the best overall performance: T288 > 60 min, Z-axis CTE as low as 1.28%, and dielectric loss of only 0.006 at 10 GHz (e.g., ...). Figure 4 As shown in the figure, it also has excellent thermal stability and copper foil adhesion.

[0062] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a high-performance halogen-free, low-loss copper-clad laminate, characterized in that: The preparation method includes the following steps: Step 1: Preparation of adhesive for electronic fiberglass cloth: by weight percentage, 14-16% polymaleimide resin, 6-10% bismaleimide resin, 4-6% phenol-biphenyl epoxy resin, 7-10% double-bond benzoxazine resin, 5-8% phosphate ester, 4-6% styrene-maleic anhydride resin, 0.01-0.1% curing accelerator, 28-31% inorganic filler, 0.3-1.0% wetting and dispersing agent, and 24-30% organic solvent; a. Add the organic solvent, double-bonded benzoxazine resin, wetting and dispersing agent, and phosphate ester to the stirred tank, start stirring to fully dissolve them, control the temperature inside the tank at 20-40℃, and stir for 60-90 minutes; b. Continue to add the dissolved polymaleimide resin, styrene maleic anhydride resin, curing accelerator and inorganic filler into the reactor, and stir continuously for 90-120 minutes to make it evenly mixed. Then turn on the high-efficiency shearing and emulsification to obtain the adhesive solution for electronic glass fiber cloth. Step 2: Preparation of fiberglass cloth semi-cured sheet: The electronic fiberglass cloth is uniformly coated with adhesive on its surface and baked in a dryer at 160-210℃. The adhesive content of the semi-cured sheet is controlled to be 46±2% and the flowability is 10-20% to obtain the fiberglass cloth semi-cured sheet. Step 3: Fabrication of FR-4 copper-clad laminate Copper foil is applied to both sides of a fiberglass cloth prepreg and then pressed at 0.8-3.0 MPa and 80-235℃ for 240-260 min. Then, it is cold-pressed at 1.3-1.6 MPa for 50-60 min to obtain FR-4 copper-clad laminate.

2. The method for preparing a high-performance halogen-free, low-loss copper-clad laminate according to claim 1, characterized in that: The polymaleimide resin is a low-melting-point polymaleimide resin, which has good solubility in a DMF / MEK=1:1 mixed solvent and an acid value of 2.35 mg KOH / g.

3. The method for preparing a high-performance halogen-free, low-loss copper-clad laminate according to claim 1, characterized in that: The bismaleimide resin is a low-crystallinity bismaleimide resin with a DSC melting point of 167.2℃, an acid value of 0.52 mgKOH / g, and a purity ≥98.1 wt%.

4. The method for preparing a high-performance halogen-free, low-loss copper-clad laminate according to claim 1, characterized in that: The phenol-biphenyl type epoxy resin has an epoxy equivalent of 280-300 g / eq, a viscosity of 2.5-4.5 poise / 150℃ ICI, and a softening point of 65-75℃.

5. The method for preparing a high-performance halogen-free, low-loss copper-clad laminate according to claim 1, characterized in that: The double-bond benzoxazine resin has a solid content of 69-71% and a viscosity of 1200-1300 mPa·s; the styrene-maleic anhydride resin has an acid value of 141-171 mg KOH / g and a kinematic viscosity of 0.70-0.80 CST.

6. The method for preparing a high-performance halogen-free, low-loss copper-clad laminate according to claim 1, characterized in that: The phosphate ester is 1,3-phenylene phosphate tetraester or 2,6-xylyl phosphate, with a phosphorus content of 9.0%.

7. The method for preparing a high-performance halogen-free, low-loss copper-clad laminate according to claim 1, characterized in that: The inorganic filler is one of modified spherical silica powder or spherical silica powder, wherein the manufacturer of the modified spherical silica powder is Guangzhou Yushun New Material Technology Co., Ltd., and the model number is YS-QR3.

8. The method for preparing a high-performance halogen-free, low-loss copper-clad laminate according to claim 1, characterized in that: The organic solvent is one or any mixture of butanone, cyclohexanone, ethylene glycol monomethyl ether, and propylene glycol monomethyl ether.

9. The method for preparing a high-performance halogen-free, low-loss copper-clad laminate according to claim 1, characterized in that: The curing accelerator is 2-methylimidazole.

10. The method for preparing a high-performance halogen-free, low-loss copper-clad laminate according to claim 1, characterized in that: In step one, the adhesive used for the electronic fiberglass cloth has a solid content of 68-75%, a viscosity of 12-28s in a four-cup coat, and a gelation time of 190-350s at 171℃.

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