An epoxy resin composition for high-frequency high-speed copper-clad plate with low thermal expansion and high peel strength

Abstract

This invention relates to the field of epoxy resin technology, specifically to an epoxy resin composition for high-frequency, high-speed copper-clad laminates that combines low thermal expansion and high peel strength. The composition comprises aliphatic cyclic epoxy resin, synergistically modified nano-silica, and spherical fused silica micropowder, among other components. The synergistic modification involves multi-step surface treatments (such as amination, epoxy grafting, triazole anchoring, siloxane shelling, and benzothiazole modification) to construct a rigid-flexible gradient interface structure. This design effectively reduces the coefficient of thermal expansion and dielectric constant, and enhances peel strength through a chemical anchoring mechanism, ensuring high reliability under thermal stress and humid conditions. Examples show that the product performs excellently in high-frequency applications such as 5G.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin technology, and more particularly to an epoxy resin composition for high-frequency, high-speed copper-clad laminates that combines low thermal expansion and high peel strength. Background Technology

[0002] High-frequency, high-speed copper-clad laminates (CCLs) are a core material in modern communication equipment, servers, and other high-frequency interconnect systems, and their performance directly affects signal transmission efficiency and equipment stability. With the development of 5G and higher-speed communication technologies, higher requirements are placed on the dielectric properties of CCLs, especially low insertion loss, which has become a key indicator. To achieve low insertion loss, the industry commonly uses low-roughness electrolytic copper foil to reduce electromagnetic wave scattering losses on the conductor surface. However, the smooth surface of low-roughness copper foil significantly weakens the traditional interface bonding mechanism that relies on the "mechanical interlocking" effect, leading to a significant decrease in the peel strength between the copper foil and the resin matrix. Furthermore, under humid and hot environments or thermal shock conditions, the interface is prone to delamination or failure, affecting the long-term reliability of the CCL. This interface weakening problem not only limits the application of low-roughness copper foil but also becomes a bottleneck in high-frequency circuit design.

[0003] To improve peel strength, existing technologies typically employ methods such as increasing the surface roughness of the copper foil or enhancing the polarity of the resin system. For example, while increasing the browning treatment strength of the copper foil or using high-roughness copper foil can temporarily improve interfacial bonding, the increased roughness of the copper foil exacerbates the skin effect during high-frequency signal transmission, introducing additional conductor losses and causing fluctuations in the effective dielectric constant, thus offsetting the advantage of low insertion loss. Furthermore, high-roughness surfaces are prone to localized electric field concentration, increasing the risk of signal distortion and making it difficult to meet the stringent signal integrity requirements of high-frequency, high-speed scenarios. This interfacial enhancement method, which sacrifices electrical performance, is clearly unsuitable for the future trend of high-frequency interconnect technology towards lower loss and higher density.

[0004] Another common approach is to introduce highly polar groups or interfacial reinforcing agents, such as strongly polar epoxy resins or coupling agents, into the resin system to improve the chemical interaction with the copper foil. While these methods can improve the initial peel strength to some extent, the highly polar components often lead to an increase in dielectric constant and loss tangent, because polar groups are prone to orientation polarization under alternating electric fields, increasing energy loss. Simultaneously, highly polar resins are highly hygroscopic; absorbing water in humid environments causes dielectric property drift, and moisture intrusion into the interface accelerates corrosion or hydrolysis reactions, reducing the moisture retention rate. More seriously, excessive polar components may disrupt the uniformity of the resin crosslinking network, leading to an increase in the coefficient of thermal expansion, generating internal stress during temperature cycling, and exacerbating interfacial fatigue.

[0005] Furthermore, to balance peel stress, some solutions attempt to introduce flexible toughening phases, such as siloxanes or rubber elastomers, to absorb interfacial energy through plastic deformation. However, the introduction of flexible phases easily leads to phase separation problems, resulting in microscopic defects in the resin matrix and reducing the glass transition temperature and thermal stability. Under high-temperature conditions, the movement of flexible segments intensifies, causing a decrease in the rigidity of the copper-clad laminate, uncontrolled thermal expansion, and low-polarity flexible phases may lack compatibility with the resin, thus weakening the overall interfacial integrity. Although this toughening method can alleviate instantaneous stress, it is difficult to achieve long-term synergy between low dielectric loss, low thermal expansion, and high peel strength, often resulting in a trade-off. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide an epoxy resin composition for high-frequency and high-speed copper-clad laminates that combines low thermal expansion and high peel strength, in order to solve the problem that existing high-frequency and high-speed copper-clad laminates use low-roughness copper foil to reduce insertion loss, but the interfacial mechanical interlocking is weakened, resulting in insufficient peel strength. In addition, conventional methods of increasing resin polarity or introducing flexible phases can easily lead to increased dielectric loss, increased moisture absorption and deterioration of the coefficient of thermal expansion, making it difficult to achieve both low loss and high reliability.

[0007] To achieve the above objectives, the present invention provides an epoxy resin composition for high-frequency and high-speed copper clad laminates that combines low thermal expansion and high peel strength. By weight, it comprises the following raw materials: 100 parts aliphatic epoxy resin, 10-30 parts synergistically modified nano silica, 250-350 parts spherical fused silica micro powder, 110 parts acid anhydride curing agent, 2 parts 2-methylimidazole, 60 parts anhydrous toluene, and 70 parts 2-butanone.

[0008] Preferably, the aliphatic epoxy resin is of type ARALDITE CY179-1.

[0009] Preferably, the D50 of the spherical fused silica micropowder is 1-5 μm.

[0010] Preferably, the anhydride curing agent is a methyltetrahydrophthalic anhydride-based anhydride curing agent.

[0011] Furthermore, the preparation steps of the synergistically modified nano-silica are as follows: the surface of aminated silica is modified by ring-opening grafting with aliphatic ring epoxy resin to obtain aliphatic ring epoxy resin modified nano-silica, which is then reacted with 3-mercapto-1,2,4-triazole through a mercapto-epoxy click reaction to obtain pre-anchored nano-silica, which is then reacted with polydimethylsiloxane containing aliphatic ring epoxy functional through ring-opening grafting to obtain siloxane-shelled nano-silica, and finally reacted with 2-mercaptobenzothiazole through a mercapto-epoxy click reaction to obtain synergistically modified nano-silica.

[0012] Preferably, the aminated silica is obtained by treating spherical molten silica with 3-aminopropyltriethoxysilane, and the weight ratio of 3-aminopropyltriethoxysilane to spherical molten silica is 30-60:200.

[0013] Preferably, the particle size of the spherical fused silica is 10-15 nm.

[0014] Preferably, in the raw materials for preparing the alicyclic epoxy resin modified nano-silica, the mass ratio of aminated silica surface to alicyclic epoxy resin is 200:80-160; in the raw materials for preparing the pre-anchored nano-silica, the mass ratio of alicyclic epoxy resin modified nano-silica to 3-mercapto-1,2,4-triazole is 200:15-50; in the raw materials for preparing the siloxane-shelled nano-silica, the mass ratio of pre-anchored nano-silica to polydimethylsiloxane containing alicyclic epoxy functionalization is 200:60-180; and in the raw materials for preparing the synergistically modified nano-silica, the mass ratio of siloxane-shelled nano-silica to 2-mercaptobenzothiazole is 200:10-35.

[0015] Preferably, the polydimethylsiloxane containing aliphatic ring epoxy functional is prepared by reacting terminal hydrogen polydimethylsiloxane with 4-vinyl-1-cyclohexene-1,2-epoxy in the presence of a platinum catalyst; and the mass ratio of terminal hydrogen polydimethylsiloxane to 4-vinyl-1-cyclohexene-1,2-epoxy is 300:120.

[0016] Preferably, the hydrogen-terminated polydimethylsiloxane is of model DMS-H05.

[0017] Furthermore, the present invention also provides a method for preparing an epoxy resin composition for high-frequency and high-speed copper-clad laminates that combines low thermal expansion and high peel strength, comprising the following steps: mixing aliphatic epoxy resin with anhydrous toluene and 2-butanone, then adding synergistically modified nano-silica for dispersion, then adding spherical molten silica micropowder in batches for mixing, degassing, adding an acid anhydride curing agent for mixing, then adding 2-methylimidazole and degassing to obtain an epoxy resin composition.

[0018] The beneficial effects of this invention are: This invention modifies nano-silica through ring-opening grafting with aliphatic ring epoxy resin, forming a rigid and low-polarity interfacial layer. This effectively suppresses the free volume expansion of resin segments under thermal stress, thereby significantly reducing the coefficient of thermal expansion of the copper-clad laminate (CCL). The rigid configuration of the aliphatic ring structure enhances interfacial bonding, reduces deformation caused by thermal stress, and maintains the dimensional stability of the CCL during temperature changes, avoiding delamination or warping caused by thermal expansion mismatch. Simultaneously, the nano-silica and spherical fused silica micropowder synergistically construct a continuous inorganic network, constraining the movement of resin molecules and further improving heat resistance and mechanical strength.

[0019] Regarding interfacial bonding, the coordination anchoring layer formed by 3-mercapto-1,2,4-triazole and 1-methylimidazole introduced in the pre-anchoring step can form a stable chemical bond with the copper foil surface, replacing the traditional mechanical interlocking mechanism, thereby achieving high peel strength under low-roughness copper foil conditions. This chemical anchoring effect is not easily affected by damp heat or thermal shock, maintaining interfacial integrity, and its low polarity avoids an increase in dielectric loss. In addition, the reactive sites of the coordination layer and the resin matrix can be programmably controlled, ensuring uniform and reliable interfacial bonding.

[0020] The shelling of nano-silica is achieved using polydimethylsiloxane containing aliphatic cyclic epoxy functional groups. Introducing a flexible siloxane layer at the interface dissipates peel and thermal stresses, reducing microcrack initiation. The low surface energy of polydimethylsiloxane improves interfacial wettability and promotes uniform dispersion of resin and filler, thereby enhancing the flexural strength and fatigue resistance of the copper-clad laminate. This rigid-flexible interfacial structure maintains low dielectric loss while improving impact toughness.

[0021] Furthermore, the synergistic modification with sulfur-containing groups such as 2-mercaptobenzothiazole enhances the affinity between the interface and the copper foil, as well as its moisture resistance. The strong interaction between sulfur atoms and the copper surface forms a protective layer, inhibiting the intrusion of environmental moisture and significantly improving the peel strength retention rate after damp heat. The gradient design of the multi-layer interface structure achieves a division of labor and synergy between chemical bonding and stress buffering, ensuring that the copper-clad laminate has the comprehensive advantages of low loss, low thermal expansion, and high reliability in high-frequency and high-speed applications. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0023] Figure 1 Infrared spectra of aminated silica (a), aliphatic epoxy resin modified nano silica (b), pre-anchored nano silica (c), siloxane-shelled nano silica (d), and synergistically modified nano silica (e) provided in Example 1 of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0025] Raw material source, model and key parameters: Aliphatic cyclic epoxy resin: Huntsman's ARALDITE CY179-1, epoxy equivalent 135 g / eq.

[0026] Anhydride curing agent: Huntsman ARADUR 917-1, a methyltetrahydrophthalic anhydride curing agent.

[0027] Hydrogen-terminated polydimethylsiloxane: Gelester DMS-H05, viscosity 5 cSt, molecular weight 650 g / mol, hydrogen content 0.3 wt%.

[0028] Platinum catalyst: Gelester SIP6831.2, platinum-divinyltetramethyldisiloxane complex, 2% Pt / xylene.

[0029] Spherical fused silica: Denka FB-3SDC, D50 is 3µm.

[0030] Electronic grade glass fiber cloth: TGF series electronic grade glass fiber cloth from Taiwan, China, specification 2116.

[0031] Electrolytic copper foil: JX Advanced Metals HLP-II, smooth electrolytic copper foil, 12µm thick, surface roughness Rz approximately 1.3µm.

[0032] Example 1:

[0033] Step S1: Add 1800g of anhydrous ethanol and 200g of deionized water to a three-necked flask. Under nitrogen protection, add 200g of spherical molten silica. After mechanical stirring at 800rpm and ultrasonic dispersion at 40kHz and 500W for 20min, add 40g of 3-aminopropyltriethoxysilane dropwise at 25℃ and continue stirring for 30min. Then raise the temperature to 60℃ and stir for 4h. After the reaction is completed, cool down to 30℃ and filter. Wash the filter cake with deionized water and anhydrous ethanol in turn. Finally, dry at 120℃ and vacuum degree -90kPa for 6h to obtain aminated silica. Step S2: Add 3000g of anhydrous tetrahydrofuran to a three-necked flask, add 200g of aminated silica under nitrogen protection, stir mechanically at 700rpm and disperse ultrasonically at 40kHz and 500W for 30min, then heat to 60℃ and add 120g of alicyclic epoxy resin in batches over 40min, maintain the reaction at 60℃ for 4h; after the reaction is completed, cool and filter, wash successively with anhydrous tetrahydrofuran and anhydrous toluene, and dry at 120℃ and vacuum degree -90kPa for 8h to obtain alicyclic epoxy resin modified nano silica; Step S3: Add 300g of hydrogen-terminated polydimethylsiloxane and 300g of anhydrous toluene to a three-necked flask, stir at 400rpm under nitrogen protection and heat to 80℃, add 120g of 4-vinyl-1-cyclohexene-1,2-epoxy dropwise over 60min, then add 200mg of platinum catalyst and maintain the reaction at 80℃ for 4h; after the reaction, cool to 30℃ and remove toluene and unreacted small molecules under 70℃ and vacuum of -90kPa for 2h to obtain polydimethylsiloxane containing aliphatic ring epoxy functionalization; Step S4: Add 2000g of anhydrous N,N-dimethylformamide to a three-necked flask, add 200g of aliphatic epoxy resin modified nano-silica and stir at 700rpm. After ultrasonic dispersion at 40kHz and 500W for 30min, add 30g of 3-mercapto-1,2,4-triazole and 10g of 1-methylimidazole and react at 50℃ for 2h. After the reaction is completed, filter and wash with anhydrous tetrahydrofuran and anhydrous toluene in sequence. Dry at 110℃ and vacuum degree -90kPa for 6h to obtain pre-anchored nano-silica. Step S5: Add 1500g of anhydrous toluene to a three-necked flask, add 200g of pre-anchored nano-silica under nitrogen protection and stir at 700rpm. After ultrasonic dispersion at 40kHz and 500W for 20min, heat to 90℃ and add 120g of polydimethylsiloxane containing aliphatic ring epoxy functional within 30min. Maintain the reaction at 90℃ for 6h. After the reaction, filter, wash successively with anhydrous toluene and anhydrous isopropanol, and dry at 120℃ and vacuum degree -90kPa for 8h to obtain siloxane-shelled nano-silica. Step S6: Add 1500g of anhydrous toluene to a three-necked flask, add 200g of siloxane-coated nano-silica under nitrogen protection and stir at 700rpm, add 20g of 2-mercaptobenzothiazole and 5g of 1-methylimidazole, and react at 70℃ for 2h; after the reaction is complete, filter, wash successively with anhydrous toluene and acetone, and dry at 120℃ and vacuum degree -90kPa for 6h to obtain synergistically modified nano-silica; Step S7: Add 1000g of aliphatic epoxy resin, 600g of anhydrous toluene and 600g of 2-butanone to a planetary vacuum mixer. Premix at 200rpm for 20min at 60℃, then add 200g of co-modified nano silica and disperse at 800rpm for 30min. Then add 3000g of spherical molten silica powder in four portions, dispersing at 1000rpm for 15min after each addition while maintaining 60℃. Degas under a vacuum of -90kPa for 30min, then add 1100g of anhydride curing agent and mix at 300rpm for 20min. Then add 20g of 2-methylimidazole and 100g of 2-butanone, mix at 300rpm for 10min under nitrogen protection, and degas under a vacuum of -90kPa for 10min to obtain an epoxy resin composition for high-frequency and high-speed copper-clad laminates with both low thermal expansion and high peel strength. Step S8: Cut 30cm*30cm electronic-grade glass fiber and place it in an impregnation machine containing 3500g of a high-frequency, high-speed epoxy resin composition for copper-clad laminates that combines low thermal expansion and high peel strength. Ensure that the effective wetting time of each unit area of ​​glass fiber cloth in the resin composition is 30s. Then, scrape it through a 1mm gap between the extrusion rollers; pre-dry it in an 80℃ hot air zone for 10 minutes to remove the solvent, and semi-cur it in a 150℃ hot air zone for 6 minutes to obtain a pre-cured sheet; cut the pre-cured sheet into 8 sheets of 300mm×300mm size, stack them, and then electrolyze them. Two copper foil sheets (12µm thick, surface roughness Rz approximately 1.3µm) were cut into 300mm×300mm sizes. They were laid out in a symmetrical structure of copper foil / prepreg / copper foil stack. The side in contact with the resin was wiped with acetone to remove grease and then immediately placed into the mold. The stack was placed in a vacuum hot press and evacuated to a vacuum degree of -90kPa. A pressure of 1MPa was applied at 100℃ and held for 30 minutes. The temperature was then raised to 180℃ and a pressure of 2MPa was applied to cure for 2 hours. The stack was then cooled to 80℃ while maintaining a pressure of 2MPa and demolded to obtain a high-frequency, high-speed copper-clad laminate.

[0034] Example 2:

[0035] Compared with Example 1, the amount of 3-aminopropyltriethoxysilane used in step S1 was 30g; the amount of alicyclic epoxy resin used in step S2 was 100g; the amount of 3-mercapto-1,2,4-triazole used in step S4 was 20g and the amount of 1-methylimidazole used was 8g; the amount of polydimethylsiloxane containing alicyclic epoxy functional group used in step S5 was 100g; the amount of 2-mercaptobenzothiazole used in step S6 was 15g and the amount of 1-methylimidazole used was 4g; the amount of synergistically modified nano-silica used in step S7 was 150g and the amount of spherical fused silica powder used was 3200g; the remaining conditions were the same as in Example 1.

[0036] Example 3:

[0037] Compared with Example 1, the amount of 3-aminopropyltriethoxysilane used in step S1 was 50g; the amount of alicyclic epoxy resin used in step S2 was 150g; the amount of 3-mercapto-1,2,4-triazole used in step S4 was 45g and the amount of 1-methylimidazole used was 12g; the amount of polydimethylsiloxane containing alicyclic epoxy functional group used in step S5 was 160g; the amount of 2-mercaptobenzothiazole used in step S6 was 30g and the amount of 1-methylimidazole used was 7g; the amount of synergistically modified nano-silica used in step S7 was 250g and the amount of spherical fused silica micropowder used was 2800g; the remaining conditions were the same as in Example 1.

[0038] Example 4:

[0039] Compared with Example 1, the amount of 3-aminopropyltriethoxysilane used in step S1 was 60g; the amount of alicyclic epoxy resin used in step S2 was 160g; the amount of 3-mercapto-1,2,4-triazole used in step S4 was 50g and the amount of 1-methylimidazole used was 15g; the amount of polydimethylsiloxane containing alicyclic epoxy functional group used in step S5 was 180g; the amount of 2-mercaptobenzothiazole used in step S6 was 35g and the amount of 1-methylimidazole used was 9g; and the amount of synergistically modified nano-silica used in step S7 was 300g and the amount of spherical fused silica micropowder used was 3500g. In S8, the pre-drying conditions in the 80℃ hot air zone were adjusted to 85℃ for 12 minutes, and the semi-curing conditions in the 150℃ hot air zone were adjusted to 155℃ for 7 minutes. The thickness of the electrolytic copper foil used was 12µm and the surface roughness Rz was 1.8µm. The hot-pressing curing conditions of the vacuum hot press were adjusted as follows: vacuum was drawn to a vacuum degree of -90kPa and pressure of 1.2MPa was applied at 105℃ and held for 35 minutes. Then the temperature was raised to 185℃ and pressure of 2.5MPa was applied for curing for 2 hours. Subsequently, the temperature was maintained at 2.5MPa and cooled to 80℃ for demolding. The remaining conditions were the same as in Example 1.

[0040] Example 5:

[0041] Compared with Example 1, the amount of aliphatic epoxy resin used in step S2 was 80g; the amount of 3-mercapto-1,2,4-triazole used in step S4 was 15g and the amount of 1-methylimidazole used was 6g; the amount of polydimethylsiloxane containing aliphatic epoxy functional group used in step S5 was 60g; the amount of 2-mercaptobenzothiazole used in step S6 was 10g and the amount of 1-methylimidazole used was 3g; the amount of synergistically modified nano-silica used in step S7 was 100g and the amount of spherical fused silica powder used was 2500g; and the pre-drying conditions in step S8 were in an 80℃ hot air zone. The pre-drying conditions were adjusted to 75℃ for 12 min, and the semi-curing conditions in the hot air zone were adjusted to 145℃ for 8 min. The thickness of the electrolytic copper foil used was 12µm and the surface roughness Rz was 0.9µm. The hot pressing curing conditions of the vacuum hot press were adjusted as follows: vacuum was drawn to a vacuum degree of -90kPa and pressure of 0.8MPa was applied at 95℃ and held for 25 min, then the temperature was raised to 175℃ and pressure of 2.0MPa was applied for curing for 2.5 h, and then cooled to 80℃ while maintaining pressure of 2.0MPa for demolding. The remaining conditions were the same as in Example 1.

[0042] Comparative Example 1: The difference from Example 1 is that the 200g of synergistically modified nano-silica added in step S7 is replaced with 200g of spherical molten silica; the other conditions are the same as in Example 1.

[0043] Comparative Example 2: The difference from Example 1 is that the 200g of synergistically modified nano-silica added in step S7 is replaced with 200g of aminated silica; the other conditions are the same as in Example 1.

[0044] Comparative Example 3: The difference from Example 1 is that the 200g of synergistically modified nano-silica added in step S7 is replaced with 200g of aliphatic epoxy resin modified nano-silica; the other conditions are the same as in Example 1.

[0045] Comparative Example 4: The difference from Example 1 is that the 200g of synergistically modified nano-silica added in step S7 is replaced with 200g of pre-anchored nano-silica; the other conditions are the same as in Example 1.

[0046] Comparative Example 5: The difference from Example 1 is that the 200g of synergistically modified nano-silica added in step S7 is replaced with 200g of siloxane-shelled nano-silica; the other conditions are the same as in Example 1.

[0047] Comparative Example 6: The difference from Example 1 is that the 30g of 3-mercapto-1,2,4-triazole added in step S4 is replaced with 30g of 2-mercaptobenzothiazole, and the 20g of 2-mercaptobenzothiazole added in step S6 is replaced with 20g of 3-mercapto-1,2,4-triazole, so that the order of adding 3-mercapto-1,2,4-triazole and 2-mercaptobenzothiazole is reversed compared to Example 1; the other conditions are the same as in Example 1.

[0048] Fourier transform infrared spectroscopy characterization: 1.0 mg each of the amino-modified silica, aliphatic epoxy resin-modified nano-silica, pre-anchored nano-silica, siloxane-shelled nano-silica, and synergistically modified nano-silica prepared in Example 1 were mixed with 100 mg of spectrally pure potassium bromide, ground for 2 min, and then compressed into tablets. The mixture was then subjected to Fourier transform infrared spectroscopy at a wavenumber of 4000 cm⁻¹. -1 -400cm -1 Scan within range, resolution 4cm -1 Using air as the background and performing baseline correction, the results are as follows: Figure 1 As shown.

[0049] Linear coefficient of thermal expansion (CTE) determination: Performed according to GB / T 36800.2-2018. Three 20mm × 5mm × thickness samples were cut from the copper-free laminate samples along the board surface direction. The expansion mode of a thermomechanical analyzer was used for testing. A static load of 0.05N was applied, and the temperature program was 30℃ to 250℃ at a heating rate of 5℃ / min. The board surface CTE (CTE0) in the 30-80℃ range was calculated. x-y Simultaneously, three 5mm × 5mm × thickness samples were cut from the copper-free laminate, with the measurement direction being the thickness direction. A static load of 0.02N was applied, and the same heating program was used to calculate the thickness direction CTE (CTE) in the 50-150℃ range. z ).

[0050] Dielectric constant and loss tangent in the microwave band. Tests were conducted according to GB / T 43801-2024, using a split dielectric resonator fixture coupled with a vector network analyzer. The test frequency was 10.0 GHz, and the test temperature was 23℃. Three 50 mm × 50 mm samples were cut from the copper-free laminate of each sample, and the thickness was measured using a micrometer and recorded to 0.001 mm. Cavity calibration, layout measurement, and data inversion were completed according to standard procedures to obtain the relative dielectric constant Dk and loss tangent Df.

[0051] Copper foil peel strength and its environmental retention rate: Tested according to GB / T 4722-2017, including peel strength, peel strength after thermal stress, and peel strength after damp heat. Five 100mm × 15mm strips were cut from each copper-clad laminate sample. A 3mm wide and 100mm long strip of copper foil was etched at one end of each strip. Peeling was performed on a universal testing machine using a 90° peeling fixture at a peeling speed of 50mm / min. The test environment was 23℃ and 50% relative humidity. The average force of the stable 50mm segment in the middle of the peel curve was taken and converted to peel strength. For the peel strength after thermal stress test, the strip was first float-soldered in a 288℃ molten solder bath for 10s, then cooled at 23℃ for 30min before peeling under the same conditions. For the peel strength after damp heat test, the strip was first peeled according to GB / T 4722-2017. 2423.3-2016 was placed at 85℃ and 85% relative humidity for 168 hours, then removed and equilibrated at 23℃ for 2 hours before being peeled off under the same conditions.

[0052] Appearance integrity and peel retention rate after temperature change cycling: According to GB / T 2423.22-2012, five 100mm×15mm test strips were cut from each copper-clad laminate sample. The cycling conditions were set as -40℃ for 30min and 125℃ for 30min, with a transition time of 3min, and 100 cycles were performed. After cycling, the peel strength was measured under 90° peel conditions, and the peel retention rate (%) was calculated.

[0053] Bending strength: According to GB / T 9341-2008, five 80mm×10mm×thickness specimens were cut from each copper-clad laminate sample. A three-point bending fixture was used with a span of 64mm and a loading speed of 2mm / min. The test environment was 23℃ and 50% relative humidity. The maximum load was recorded and the bending strength was calculated.

[0054]

[0055] Data Analysis: As can be seen from the data in Table 1, the high-frequency high-speed copper-clad laminate prepared by the present invention exhibits a low coefficient of thermal expansion in both the surface and thickness directions, maintains a low dielectric constant and loss tangent in the microwave band, and maintains high copper foil peel strength and good temperature change cycle retention in the acceptance state, under thermal stress, and after damp heat treatment. The underlying reason is that the synergistic modification of nano-silica and spherical fused silica micropowder together form an inorganic constraint network with high filler content and low free volume fluctuation, which significantly suppresses the scale-up effect of aliphatic epoxy resin segments during the heating process. At the same time, the pre-anchored nano-silica introduces a coordination anchoring layer formed by 3-mercapto-1,2,4-triazole and 1-methylimidazole on the surface, making the chemical interaction between nano-silica and copper foil more stable. Furthermore, the shell is formed by polydimethylsiloxane containing aliphatic epoxy functional group, so that the interface forms a flexible energy dissipation layer, reducing thermal stress concentration and microcrack initiation. Finally, sulfur-containing groups such as 2-mercaptobenzothiazole are introduced to enhance the affinity and moisture resistance of the copper surface, thereby achieving a synergistic balance between low thermal expansion, low dielectric loss and high peel strength.

[0056] As can be seen from the data in Example 1 and Comparative Examples 1-3 in Table 1, when the synergistically modified nano-silica degenerates into unmodified nano-silica, aminated silica, or nano-silica modified only by aliphatic epoxy resin, the overall performance of the copper clad laminate in terms of dielectric loss, thermal expansion, and peeling-related indicators deteriorates to varying degrees. The main reasons are: unmodified nano-silica is more prone to agglomeration and introduces interfacial porosity, resulting in discontinuity of the inorganic constraint network; while aminated silica improves dispersion, the polar groups bring stronger water affinity and interfacial polarization loss; and while modification with only aliphatic epoxy resin enhances compatibility with the resin, it lacks subsequent multi-layered interfacial regulation through coordination anchoring and shell formation, making it difficult to continuously suppress interfacial crack propagation under thermal stress and temperature cycling. Therefore, this invention does not rely on a single surface modification, but rather achieves more stable overall gains through a multi-step construction of interfacial layers.

[0057] As can be seen from the data in Table 1 for Example 1 and Comparative Example 4, while using only pre-anchored nano-silica without siloxane shelling and subsequent synergistic modification can improve peel strength to some extent, it is difficult to achieve a better balance between dielectric loss and environmental retention. This may be because the anchoring layer formed by 3-mercapto-1,2,4-triazole and 1-methylimidazole is relatively rigid and highly polar, making the interface more prone to local stress concentration and moisture-induced micro-defects under thermal cycling and humid heat. Simultaneously, the lack of the compliance buffer and improved interfacial wetting provided by polydimethylsiloxane shelling makes it difficult to fully convert the initial adhesion advantage brought by "strong coordination" into long-term reliability. Therefore, the anchoring layer needs to work synergistically with the compliance shell layer to achieve a synergistic interface stabilization effect greater than the sum of its parts.

[0058] As can be seen from the data in Table 1 for Example 1 and Comparative Example 5, when only siloxane-coated nano-silica is used without pre-anchoring and synergistic modification, dielectric loss and thermal expansion can be maintained within a relatively good range, but the improvement in peel strength and retention after thermal stress is limited. This may be because polydimethylsiloxane coating mainly provides interfacial compliance and low-polarity shielding, which can alleviate stress and suppress interfacial polarization, but its chemical anchoring effect on the copper surface is insufficient. When the interface mainly relies on physical interlocking and weak interactions, thermal shock is more likely to trigger interfacial slip and defect propagation. Therefore, coating needs to be combined with coordination anchoring by 3-mercapto-1,2,4-triazole / 1-methylimidazole and the sulfur-containing copper affinity of 2-mercaptobenzothiazole to achieve a synergistic leap from low loss to high peel strength and high reliability.

[0059] As can be seen from the data in Table 1 for Example 1 and Comparative Example 6, when the order of introduction of 3-mercapto-1,2,4-triazole and 2-mercaptobenzothiazole is reversed compared to Example 1, the peel strength and retention rate of the copper-clad laminate decrease, and the dielectric loss changes unfavorably. This may be because: if the preferential anchoring and reaction localization formed by 3-mercapto-1,2,4-triazole and 1-methylimidazole is lacking in the pre-anchoring stage, the subsequent sulfur-containing groups are more likely to produce non-uniform coverage on the nano-silica surface, resulting in insufficient reaction coupling between the shell layer and the resin phase; the strong inner and tough outer structure at the interface level is difficult to form, thus making the interface more prone to fatigue under thermal stress and temperature cycling. This indicates that the order of steps in this invention is not arbitrarily interchangeable, and there is a synergistic effect brought about by the order of interface layer construction.

[0060] from Figure 1 It can be seen that, compared with unmodified silica, the aminated silica prepared in Example 1 has a higher growth rate at 2930 cm⁻¹. -1 and 2870cm -1 An absorption peak for the -CH2- stretching vibration appears at 3320 cm⁻¹. -1 An absorption peak for the -NH2 stretching vibration appears nearby, and at 1600 cm⁻¹ -1 The presence of characteristic absorptions from the -NH2 bending vibration on both sides indicates that 3-aminopropyltriethoxysilane has been successfully grafted onto the silica surface; further grafting with aliphatic epoxy resin resulted in the sample exhibiting absorption at 1725 cm⁻¹. -1 A distinct absorption peak for the ester group C=O appears at 1250 cm⁻¹. -1 With 1180cm -1 A COC stretching vibration peak appears at 915 cm⁻¹. -1 The presence of characteristic absorption of the epoxy ring at the 915 cm⁻¹ indicates that the aliphatic epoxy resin has been coupled to the aminated surface. After pre-anchoring treatment with 3-mercapto-1,2,4-triazole, the absorption at 915 cm⁻¹... -1The intensity of the characteristic peak of epoxy is significantly reduced, and at 1590 cm⁻¹... -1 and 1500cm -1 The presence of triazole ring skeletal vibrational absorption nearby indicates that some epoxy groups have undergone ring-opening addition with sulfur-containing heterocycles, forming the first coordination anchoring layer at the nano-silica interface. Based on this, the introduction of polydimethylsiloxane with aliphatic ring epoxy functionalization further enhanced the sample's absorption at 2960 cm⁻¹. -1 2905cm -1 Si-CH3 stretching vibration absorption occurs at 1260 cm⁻¹. -1 With 1010cm -1 The presence of characteristic peaks indicating Si-CH3 deformation and enhanced Si-O-Si framework vibration at 915 cm⁻¹ indicates the further formation of a flexible siloxane shell on the surface of the nano-silica; finally, after synergistic modification with 2-mercaptobenzothiazole, the peak at 915 cm⁻¹... -1 Epoxy absorption has essentially disappeared, 1600cm -1 1500cm -1 and 1330cm -1 The region exhibits distinct aromatic ring and C=N / C=S skeletal vibration peaks, at 750 cm⁻¹. -1 The presence of aromatic CH out-of-plane bending vibration absorption nearby, combined with the retention of characteristic peaks of Si-O-Si and Si-CH3, proves that a multi-level interface structure composed of an amino coupling layer, an aliphatic ring epoxy graft layer, a nitrogen-containing heterocyclic anchoring layer, and a siloxane / benzothiazole synergistic layer has been constructed on the surface of nano-silica.

[0061] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. An epoxy resin composition for high-frequency, high-speed copper-clad laminates that combines low thermal expansion and high peel strength, characterized in that, By weight, it includes the following raw materials: 100 parts aliphatic epoxy resin, 10-30 parts synergistically modified nano silica, 250-350 parts spherical fused silica micro powder, 110 parts acid anhydride curing agent, 2 parts 2-methylimidazole, 60 parts anhydrous toluene and 70 parts 2-butanone. The preparation steps of the synergistically modified nano-silica are as follows: the surface of aminated silica is modified by ring-opening grafting with aliphatic epoxy resin to obtain aliphatic epoxy resin modified nano-silica, which is then reacted with 3-mercapto-1,2,4-triazole through a mercapto-epoxy click reaction to obtain pre-anchored nano-silica, which is then reacted with polydimethylsiloxane containing aliphatic epoxy functional group through ring-opening grafting to obtain siloxane-shelled nano-silica, and finally reacted with 2-mercaptobenzothiazole through a mercapto-epoxy click reaction to obtain synergistically modified nano-silica.

2. The epoxy resin composition for high-frequency, high-speed copper-clad laminates with both low thermal expansion and high peel strength according to claim 1, characterized in that, The aliphatic epoxy resin is designated as ARALDITE CY179-1.

3. The epoxy resin composition for high-frequency, high-speed copper-clad laminates with both low thermal expansion and high peel strength according to claim 1, characterized in that, The D50 of the spherical fused silica micropowder is 1-5 μm.

4. The epoxy resin composition for high-frequency, high-speed copper-clad laminates with both low thermal expansion and high peel strength according to claim 1, characterized in that, The anhydride curing agent is a methyltetrahydrophthalic anhydride-based anhydride curing agent.

5. The epoxy resin composition for high-frequency, high-speed copper-clad laminates with both low thermal expansion and high peel strength according to claim 1, characterized in that, The aminated silica is obtained by treating spherical molten silica with 3-aminopropyltriethoxysilane, and the weight ratio of 3-aminopropyltriethoxysilane to spherical molten silica is 30-60:

200.

6. The epoxy resin composition for high-frequency, high-speed copper-clad laminates with both low thermal expansion and high peel strength according to claim 5, characterized in that, The spherical molten silica has a particle size of 10-15 nm.

7. The epoxy resin composition for high-frequency, high-speed copper-clad laminates with both low thermal expansion and high peel strength according to claim 1, characterized in that, The mass ratio of aminated silica surface to alicyclic epoxy resin in the raw materials for preparing alicyclic epoxy resin modified nano-silica is 200:80-160; the mass ratio of alicyclic epoxy resin modified nano-silica to 3-mercapto-1,2,4-triazole in the raw materials for preparing pre-anchored nano-silica is 200:15-50; the mass ratio of pre-anchored nano-silica to polydimethylsiloxane containing alicyclic epoxy functional group in the raw materials for preparing siloxane-shelled nano-silica is 200:60-180; and the mass ratio of siloxane-shelled nano-silica to 2-mercaptobenzothiazole in the raw materials for preparing synergistically modified nano-silica is 200:10-35.

8. The epoxy resin composition for high-frequency, high-speed copper-clad laminates with both low thermal expansion and high peel strength according to claim 1, characterized in that, The polydimethylsiloxane containing aliphatic ring epoxy functional group is prepared by reacting terminal hydrogen polydimethylsiloxane with 4-vinyl-1-cyclohexene-1,2-epoxy in the presence of a platinum catalyst; and the mass ratio of terminal hydrogen polydimethylsiloxane to 4-vinyl-1-cyclohexene-1,2-epoxy is 300:

120.

9. The epoxy resin composition for high-frequency, high-speed copper-clad laminates with both low thermal expansion and high peel strength according to claim 8, characterized in that, The type of the hydrogen-terminated polydimethylsiloxane is DMS-H05.

10. A method for preparing an epoxy resin composition for high-frequency, high-speed copper-clad laminates that combines low thermal expansion and high peel strength according to any one of claims 1-9, characterized in that, Includes the following steps: Aliphatic epoxy resin was mixed with anhydrous toluene and 2-butanone, and then synergistically modified nano-silica was added for dispersion. Spherical molten silica micropowder was then added in batches and mixed. After degassing, an acid anhydride curing agent was added and mixed. Then 2-methylimidazole was added and degassed to obtain an epoxy resin composition.

Images