Fluororesin base material copper-clad plate as well as preparation method and application thereof

Abstract

The invention relates to a fluororesin base material copper-clad plate as well as a preparation method and application thereof. The fluororesin base material copper-clad plate comprises a resin-coated copper foil prepared from fluororesin slurry A and an adhesive film composed of fluororesin slurry B, wherein the resin-coated copper foil and the adhesive film are formed by pressing; the resin-coated copper foil is formed by coating the rough surface of the copper foil with fluororesin slurry A, drying and sintering in a nitrogen atmosphere; and the adhesive film is formed by coating a release material with fluororesin slurry B, drying and sintering. The fluororesin base material copper-clad plate provided by the invention not only has good dielectric properties, but also has good adhesion and low-temperature lamination capability, and meanwhile, CTE data of a film is close to that of a copper foil through proportion regulation and control and preparation process regulation and control, so that the thermal stability of the copper-clad plate is further enhanced, and the use requirements of PCB customers on the copper-clad plate are met.

Description

Technical Field

[0001] This invention belongs to the field of electronic circuit technology, specifically relating to a copper-clad laminate with a fluororesin substrate, its preparation method, and its application. Background Technology

[0002] Copper-clad laminates (CCLs) are an important electronic substrate widely used in high-frequency, high-speed circuits and high-reliability electronic equipment. They consist of one or more layers of substrates coated with metal (usually copper), such as glass cloth, ceramics, and polyimide. Among these, fluoropolymer-based CCLs have become the preferred material for high-frequency, high-speed circuits and high-reliability electronic equipment due to their excellent dielectric properties, low dielectric constant, and low water absorption. Fluoropolymers are polymeric materials with excellent chemical stability and electrical insulation. They can be mixed with other materials and modified to produce various high-performance fluoropolymer-based CCLs.

[0003] However, due to the inherent properties of fluoropolymers, their coefficient of thermal expansion (CTE) at high temperatures is relatively high, differing significantly from that of copper foil. This can easily lead to warping and delamination of the copper-clad laminate at high temperatures, affecting its thermal stability and service life. Furthermore, because polytetrafluoroethylene (PTFE) has a highly symmetrical structure and is a non-polar polymer, it often requires high temperatures and pressures for extended periods during lamination with copper foil to achieve a tight bond with the copper teeth on the foil surface. Adding excessive amounts of tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer (PFA) emulsion to the PTFE emulsion also increases costs. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a copper-clad laminate based on a fluororesin substrate. By using two polytetrafluoroethylene (PTFE) emulsions of different molecular weights and combining them with appropriate ceramic fillers, the problem of adhesion to copper foil can be solved, the material delamination problem caused by insufficient cohesive strength can be overcome, and the CTE can be maintained at a level consistent with that of the copper foil. In addition, the intermediate layer uses a thin layer containing PFA, which can bond two resin-coated copper foils at a relatively low temperature, while keeping the overall cost under control and not increasing it too much.

[0005] Specifically, in addressing the adhesion issue between the insulation layer and the copper foil, this invention controls the content of relatively low molecular weight polytetrafluoroethylene (PTFE) in the PTFE emulsion. As the molecular weight of PTFE decreases, its particle size also decreases, allowing for better interlocking with the copper foil's teeth. During sintering, more time is needed near the melting point of the PTFE molecules to allow for sufficient flow and further integration with the copper teeth. The sintering process of this invention involves a heating rate of 1–2 °C / min within the temperature range of 320 °C to 340 °C. However, if all the polytetrafluoroethylene (PTFE) is of low molecular weight, the film's cohesive strength will be insufficient. This is especially true in this invention, which uses a large amount of ceramic filler to reduce its coefficient of thermal expansion. This can easily lead to insufficient interlayer adhesion due to insufficient cohesive strength within the film. To address this, this invention further uses a blend of relatively low molecular weight PTFE and relatively high molecular weight PTFE resin. This not only solves the problem of poor adhesion between the insulation layer and the copper foil but also overcomes the issue of poor interlayer adhesion caused by insufficient cohesive strength. The improved adhesion between the insulation layer and the copper foil does not increase the use of PTFE-perfluoroalkoxy vinyl ether copolymer, thus saving costs.

[0006] The technical solution adopted in this invention is as follows:

[0007] This invention provides a copper-clad laminate based on a fluororesin substrate, comprising a resin-coated copper foil prepared by fluororesin slurry A and an adhesive film composed of fluororesin slurry B, wherein the resin-coated copper foil and the adhesive film are laminated together.

[0008] The resin-coated copper foil is formed by coating the rough surface of the copper foil with fluororesin slurry A, drying, and sintering in a nitrogen atmosphere; the adhesive film is formed by coating the release material with fluororesin slurry B, drying, and sintering.

[0009] The fluororesin slurry A comprises the following components in weight percentage:

[0010] Polytetrafluoroethylene slurry 25-40%, ceramic filler 55-75%, additives 0-5%;

[0011] The fluororesin slurry B comprises the following components in weight percentage:

[0012] 25-40% tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, 55-75% ceramic filler, and 0-5% additives.

[0013] The tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer of the present invention is commercially available and can be Daikin AW1000 or Asahi Glass EA2000.

[0014] The highest temperature during the lamination process of the resin-coated copper foil and adhesive film is between 320 and 340°C, and the duration of holding the highest temperature is between 30 and 60 minutes. Specific temperatures can be 320°C, 325°C, 330°C, 335°C, 340°C, etc., and specific durations of holding the highest temperature are 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, etc.; the lamination pressure is 15–50 kg / cm². 2 Specifically, it could be 15 kg / cm 2 20kg / cm 2 25kg / cm 2 30kg / cm 2 ,

[0015] 35kg / cm 2 40kg / cm 2 45kg / cm 2 50kg / cm 2 etc.

[0016] The polytetrafluoroethylene (PTFE) is composed of PTFE with relatively high molecular weight and PTFE with relatively low molecular weight. The relatively high molecular weight refers to PTFE with a molecular weight of 2 million to 10 million, more preferably, it refers to PTFE with a molecular weight of 5 million to 8 million, specifically 5 million, 5.5 million, 6 million, 6.5 million, 7 million, 7.5 million, 8 million, etc. The relatively low molecular weight refers to PTFE with a molecular weight of 10,000 to 500,000, more preferably, it refers to PTFE with a molecular weight of 30,000 to 200,000, specifically 30,000, 50,000, 80,000, 100,000, 130,000, 150,000, 180,000, 200,000, etc.

[0017] The mass ratio of the relatively high molecular weight polytetrafluoroethylene to the relatively low molecular weight polytetrafluoroethylene is (3-7):(3-7); specifically, it can be 3:7, 4:6, 5:5, 6:4, 7:3, etc.

[0018] The ceramic filler is any one or a mixture of at least two of silicon dioxide, titanium dioxide, aluminum oxide, boron nitride, silicon nitride, and barium titanate. More preferably, the ceramic filler is a mixture of silicon dioxide, titanium dioxide, and / or boron nitride. The particle size of the ceramic filler in this invention is preferably 0.5-100 μm.

[0019] The additive is a fluorinated silane coupling agent, such as trifluoropropylmethyldimethoxysilane or heptadecafluorodecyltrimethoxysilane, used for pretreatment of ceramic fillers.

[0020] The drying temperature of the resin-coated copper foil is 50–150℃, specifically 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, etc. The maximum sintering temperature is between 360–380℃, and the holding time at the maximum temperature during sintering is 5–25 minutes. More preferably, a programmed temperature rise is performed during sintering, with a heating rate ≤2℃ / min within the temperature range of 320℃–340℃; considering production efficiency, a rate of 1–2℃ / min is preferred.

[0021] The thickness of the resin layer after sintering the resin-coated copper foil is 5-200 μm, specifically, it can be 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, etc.

[0022] The drying temperature of the adhesive film is 50–150℃, specifically, it can be 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, etc. The maximum sintering temperature is between 360–380℃, and the maximum sintering temperature holding time is 5–25 minutes. More preferably, a programmed temperature rise is performed during sintering, with a heating rate ≤2℃ / min within the temperature range of 320℃–340℃. Considering production efficiency, a rate of 1–2℃ / min is preferred.

[0023] The thickness of the adhesive film is 5 to 25 μm, specifically, it can be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, etc.

[0024] The release material is any one of polyimide film, aluminum foil, iron foil, and steel foil. More preferably, the release material is a polyimide film with a Tg higher than 400°C and a CTE less than 20ppm / K.

[0025] The adhesive film is peeled off from the release material after sintering.

[0026] The preparation method of the copper-clad laminate with fluororesin substrate includes the following steps:

[0027] (1) Cut the resin-coated copper foil and adhesive film to the required size and stack them together. The structure from top to bottom is resin-coated copper foil / adhesive film / resin-coated copper foil. Depending on the thickness requirements, the middle layer of adhesive film can be composed of one or more layers.

[0028] (2) Place the above structure into a laminator, maintaining a maximum temperature between 320 and 340°C for 30 to 60 minutes and a pressure of 15 to 50 kg / cm². 2 Under certain conditions, copper-clad laminates with fluororesin substrates can be obtained by lamination. Detailed Implementation

[0029] To enable those skilled in the art to gain a clearer and more intuitive understanding of the present invention, further descriptions will be provided below. Experimental methods in the following embodiments, unless otherwise specified, were performed according to conventional methods and conditions, or as selected in the product manual.

[0030] Example 1

[0031] This embodiment of a fluororesin-based copper-clad laminate includes a resin-coated copper foil prepared by fluororesin slurry A and an adhesive film composed of fluororesin slurry B, which are formed by pressing the resin-coated copper foil and the adhesive film together.

[0032] The resin-coated copper foil is formed by coating the rough surface of the copper foil with fluororesin slurry A, drying, and sintering in a nitrogen atmosphere; fluororesin slurry A comprises the following components by weight percentage:

[0033] Polytetrafluoroethylene slurry 35%, ceramic filler 60%, additives 5%;

[0034] The adhesive film is formed by coating, drying, and sintering fluororesin slurry B onto a release material; fluororesin slurry B comprises the following components by weight percentage:

[0035] The composition consists of 35% tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer (Daikin AW1000), 60% ceramic filler, and 5% additives.

[0036] The polytetrafluoroethylene (PTFE) is composed of PTFE with relatively high molecular weight and PTFE with relatively low molecular weight. In this embodiment, relatively high molecular weight refers to a molecular weight of 2 million.

[0037] Polytetrafluoroethylene with a molecular weight of approximately 10 million. Relatively low molecular weight refers to polytetrafluoroethylene with a molecular weight of 10,000 to 500,000.

[0038] The mass ratio of relatively high molecular weight polytetrafluoroethylene (PTFE) to relatively low molecular weight PTFE is (3-7):(3-7); in this embodiment, the ratio is 3:7, the molecular weight of the relatively high molecular weight PTFE is 2-3 million, and the molecular weight of the relatively low molecular weight PTFE is 100,000-100,000.

[0039] The ceramic filler is any one or a mixture of at least two of silicon dioxide, titanium dioxide, aluminum oxide, boron nitride, silicon nitride, and barium titanate. In this embodiment, the ceramic filler is a mixture of silicon dioxide and titanium dioxide in a mass ratio of 1:1. The amount of silicon dioxide used is related to the dielectric properties, and its amount can be adjusted according to the product performance requirements in actual operation.

[0040] The additive is trifluoropropylmethyldimethoxysilane, used for pretreatment of ceramic fillers.

[0041] The drying temperature of the resin-coated copper foil is 50–150°C, and in this embodiment, a drying temperature of 100°C is used. The maximum sintering temperature is a programmed temperature rise of 370°C, and the maximum sintering temperature is held for 15 minutes. More preferably, the sintering process involves programmed temperature rise, with a heating rate of 2°C / min within the temperature range of 320°C–340°C, which prolongs the sintering time and improves the fit between the polytetrafluoroethylene and the copper foil.

[0042] The thickness of the resin layer after sintering the resin-coated copper foil is 5-200 μm. Specifically, it can be 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, etc. In this embodiment, the resin layer thickness is 100 μm.

[0043] The drying temperature of the adhesive film is 50-150℃, and 100℃ is used in this embodiment. The maximum sintering temperature is 370℃, and the maximum temperature is held for 15 minutes during sintering. The temperature is programmed during sintering, and the heating rate is 2℃ / min between 320℃ and 340℃.

[0044] The thickness of the adhesive film is 5-25 μm, and the thickness of the adhesive film prepared in this embodiment is 15 μm.

[0045] The release material uses polyimide film with a Tg higher than 400℃ and a CTE less than 20ppm / K, such as the GF200 polyimide film produced by PIAM.

[0046] The adhesive film is peeled off from the release material after sintering.

[0047] The preparation method of the copper-clad laminate with fluororesin substrate includes the following steps:

[0048] (1) Cut the resin-coated copper foil and adhesive film to the required size and stack them together. The structure from top to bottom is resin-coated copper foil / adhesive film / resin-coated copper foil, with the adhesive film in the middle being a single layer.

[0049] (2) Place the above structure into a laminator, using a maximum temperature of 340℃, a maximum temperature holding time of 30min, and a pressure of 15kg / cm. 2 Copper-clad laminates with fluororesin substrates can be obtained by laminating under the specified lamination conditions.

[0050] Example 2

[0051] The difference between this embodiment and Embodiment 1 is that in this embodiment, the mass ratio of relatively high molecular weight PTFE to relatively low molecular weight PTFE is 4:6, the molecular weight of the relatively high molecular weight PTFE is 2-3 million, and the molecular weight of the relatively low molecular weight PTFE is 10-100,000. Furthermore, the highest sintering temperature for the resin-coated copper foil and adhesive film in this embodiment is 375°C, and the holding time at the highest sintering temperature is 10 min. The sintering of the resin-coated copper foil and adhesive film involves programmed temperature increases, with a heating rate of 1.8°C / min within the temperature range of 320°C to 340°C. Compared to Embodiment 1, this embodiment uses a heating rate of 1.8°C / min in the sintering of the resin-coated copper foil, which prolongs the sintering process time and improves the fit between the PTFE and the copper teeth. The pressing conditions for the adhesive film and resin-coated copper foil are: a maximum temperature of 335°C, a maximum temperature holding time of 35 min, and a pressure of 20 kg / cm². 2 .

[0052] Example 3

[0053] The difference between this embodiment and Embodiment 1 is that in this embodiment, the mass ratio of relatively high molecular weight PTFE to relatively low molecular weight PTFE is 5:5, the molecular weight of the relatively high molecular weight PTFE is 2-3 million, and the molecular weight of the relatively low molecular weight PTFE is 10,000-100,000. Furthermore, the maximum sintering temperature of the resin-coated copper foil and adhesive film in this embodiment is 380°C, and the holding time at the maximum sintering temperature is 5 minutes. The sintering of the resin-coated copper foil and adhesive film involves programmed temperature increases, with a heating rate of 1.5°C / min within the temperature range of 320°C to 340°C. Compared to other embodiments, this embodiment uses a heating rate of 1.5°C / min in the sintering of the resin-coated copper foil to further extend the sintering process time and improve the fit between the PTFE and the copper teeth. The pressing conditions for the adhesive film and resin-coated copper foil are: a maximum temperature of 330°C, a maximum temperature holding time of 40 minutes, and a pressure of 30 kg / cm². 2 .

[0054] Example 4

[0055] The difference between this embodiment and Embodiment 1 is that in this embodiment, the mass ratio of relatively high molecular weight PTFE to relatively low molecular weight PTFE is 6:4, the molecular weight of the relatively high molecular weight PTFE is 2-3 million, and the molecular weight of the relatively low molecular weight PTFE is 10-100,000. Furthermore, the highest sintering temperature for the resin-coated copper foil and adhesive film in this embodiment is 365°C, and the holding time at the highest sintering temperature is 20 min. The sintering of the resin-coated copper foil and adhesive film involves programmed temperature increases, with a heating rate of 1.2°C / min within the temperature range of 320°C to 340°C. Compared to other embodiments, this embodiment further extends the sintering time in the resin-coated copper foil sintering process, improving the fit between the PTFE and the copper teeth. The pressing conditions for the adhesive film and resin-coated copper foil are: a maximum temperature of 325°C, a maximum temperature holding time of 45 min, and a pressure of 40 kg / cm². 2 .

[0056] Example 5

[0057] The difference between this embodiment and Embodiment 1 is that in this embodiment, the mass ratio of relatively high molecular weight PTFE to relatively low molecular weight PTFE is 7:3, the molecular weight of the relatively high molecular weight PTFE is 2-3 million, and the molecular weight of the relatively low molecular weight PTFE is 10,000-100,000. Furthermore, the highest sintering temperature for the resin-coated copper foil and adhesive film in this embodiment is 360°C, the maximum sintering temperature holding time is 25 min, and the sintering program temperature rise for the resin-coated copper foil and adhesive film is 1.0°C / min within the temperature range of 320°C-340°C. Compared to other embodiments, this embodiment further extends the sintering process time in the resin-coated copper foil sintering, improving the interlocking degree between PTFE and copper teeth. The pressing conditions for the adhesive film and resin-coated copper foil are: a maximum temperature of 320°C, a maximum temperature holding time of 60 min, and a pressure of 50 kg / cm². 2 .

[0058] Example 6

[0059] The difference between this embodiment and Embodiment 1 is that in this embodiment, the heating rate from 320℃ to 340℃ is adjusted to 1.8℃ / min.

[0060] Example 7

[0061] The difference between this embodiment and Embodiment 1 is that in this embodiment, the heating rate from 320℃ to 340℃ is adjusted to 1.5℃ / min.

[0062] Example 8

[0063] The difference between this embodiment and Embodiment 1 is that in this embodiment, the heating rate from 320℃ to 340℃ is adjusted to 1.2℃ / min.

[0064] Example 9

[0065] The difference between this embodiment and Embodiment 1 is that in this embodiment, the heating rate from 320℃ to 340℃ is adjusted to 1.0℃ / min.

[0066] Example 10

[0067] The difference between this embodiment and Embodiment 1 is that in this embodiment, the molecular weight of the relatively high molecular weight polytetrafluoroethylene is 4 million to 6 million, and the molecular weight of the relatively low molecular weight polytetrafluoroethylene is 100,000 to 200,000.

[0068] Example 11

[0069] The difference between this embodiment and Embodiment 1 is that in this embodiment, the molecular weight of the relatively high molecular weight polytetrafluoroethylene is 6 million to 8 million, and the molecular weight of the relatively low molecular weight polytetrafluoroethylene is 200,000 to 300,000.

[0070] Example 12

[0071] The difference between this embodiment and Embodiment 1 is that in this embodiment, the molecular weight of the relatively high molecular weight polytetrafluoroethylene is 8 million to 10 million, and the molecular weight of the relatively low molecular weight polytetrafluoroethylene is 300,000 to 400,000.

[0072] Example 13

[0073] The difference between this embodiment and Embodiment 1 is that in this embodiment, the molecular weight of the relatively high molecular weight polytetrafluoroethylene is 8 million to 10 million, and the molecular weight of the relatively low molecular weight polytetrafluoroethylene is 400,000 to 500,000.

[0074] Example 14

[0075] The difference between this embodiment and Embodiment 1 is that fluoropolymer slurry A includes 33% polytetrafluoroethylene slurry, 65% ceramic filler, and 2% additives; fluoropolymer slurry B includes 33% perfluoropropyl perfluorovinyl ether-polytetrafluoroethylene copolymer, 65% ceramic filler, and 2% additives.

[0076] Example 15

[0077] The difference between this embodiment and Embodiment 1 is that fluoropolymer slurry A includes 25% polytetrafluoroethylene slurry, 72% ceramic filler, and 3% additives; fluoropolymer slurry B includes 25% perfluoropropyl perfluorovinyl ether-polytetrafluoroethylene copolymer, 72% ceramic filler, and 3% additives.

[0078] Example 16

[0079] The difference between this embodiment and Embodiment 1 is that fluoropolymer slurry A includes 40% polytetrafluoroethylene slurry, 56% ceramic filler, and 4% additives; fluoropolymer slurry B includes 40% perfluoropropyl perfluorovinyl ether-polytetrafluoroethylene copolymer, 56% ceramic filler, and 4% additives.

[0080] The main process parameters for each embodiment are shown in Table 1.

[0081] Table 1 Main process parameters of Examples 1-16

[0082]

[0083]

[0084] In this context, A1, A2, and A3 represent polytetrafluoroethylene slurry, ceramic filler, and additives, respectively; B1, B2, and B3 represent perfluoropropyl perfluorovinyl ether-polytetrafluoroethylene copolymer, ceramic filler, and additives, respectively.

[0085] The copper-clad laminates prepared in Examples 1-16 above were subjected to relevant performance tests. The performance test methods are as follows:

[0086] Coefficient of thermal expansion (CTE): Tested using IPC-TM-650 2.4.41 method, unit ppm / K;

[0087] Thermal stress: Tested using IPC-TM-650 2.6.8.1 method.

[0088] Interlayer bond strength: Cut the material into 5*15mm samples using a knife. Burn one end with a flame source (lighter or acetylene lamp) to separate the PTFE layer from the PFA layer. After the sample cools, gently peel them apart. Then place both sides on a material tensile tester to separate them in a "T" shape. Test the adhesion force. Divide the obtained force value by 5mm to get the interlayer bond strength result, in N / mm.

[0089] Peel strength: Tested using IPC-TM-650 2.4.8 method, unit N / mm;

[0090] Dielectric constant (Dk), dielectric loss (Df): Tested using IPC-TM-650 2.5.5.5 method.

[0091] The performance test results of the copper-clad laminates prepared in Examples 1 to 16 are shown in Table 2.

[0092] Table 2 Performance test results of copper-clad laminates prepared in Examples 1-16

[0093]

[0094] Examples 1-9 investigated the effects of varying the ratio of high and low molecular weight PTFE and the heating rate during the 320℃-340℃ stage on the performance of the copper-clad laminate. The results showed that using different ratios of high and low molecular weight PTFE, and extending the sintering time during the 320℃-340℃ stage, could control the interlocking degree between PTFE and the copper contacts, thus adjusting the peel strength of the product. Specifically, the peel strength increased with increasing low molecular weight PTFE content and decreased with increasing heating rate during the 320℃-340℃ stage. Therefore, in the preparation of fluoropolymer-based copper-clad laminates, to improve the peel strength, the content of low molecular weight PTFE should be maximized while minimizing the heating rate during the 320℃-340℃ stage.

[0095] Therefore, to further investigate the effect of heating rate on the performance changes of copper-clad laminate, comparative examples 1-5 were set up by modifying the heating rate parameter of 320℃~340℃ based on Examples 1 and 6-10. In addition, to further investigate the effect of the ratio of large and small molecular weights of polytetrafluoroethylene on the performance changes of copper-clad laminate, comparative examples 6 and 7 were set up by modifying the ratio of large and small molecular weights of polytetrafluoroethylene based on Examples 1 and 5. The main process parameters of comparative examples 1-7 are shown in Table 3.

[0096] Table 3 Main process parameters of Comparative Examples 1-7

[0097]

[0098]

[0099] In this context, A1, A2, and A3 represent polytetrafluoroethylene slurry, ceramic filler, and additives, respectively; B1, B2, and B3 represent perfluoropropyl perfluorovinyl ether-polytetrafluoroethylene copolymer, ceramic filler, and additives, respectively.

[0100] Similarly, the performance test results of the copper-clad laminates prepared in Comparative Examples 1 to 7 are shown in Table 4.

[0101] Table 4. Performance test results of copper-clad laminates prepared in Comparative Examples 1–7

[0102]

[0103] Based on the performance changes of the copper-clad laminates in Comparative Examples 1-5, a slower heating rate is beneficial to improving the peel strength, because a slower heating rate indicates a longer reaction time, which is beneficial to improving the bonding strength. Considering production efficiency, the present invention preferably uses a heating rate of 1-2℃ / min.

[0104] The performance changes of the copper-clad laminates in Comparative Examples 6 and 7 show that both excessively high and low proportions of low molecular weight PTFE in the polytetrafluoroethylene (PTFE) significantly impact the peel strength of the products. In particular, a higher content of low molecular weight PTFE is beneficial for improving peel strength; however, excessive low molecular weight PTFE can lead to insufficient cohesive strength of the film. Especially given the use of a large amount of ceramic filler in this invention to reduce its coefficient of thermal expansion, insufficient interlayer adhesion due to inadequate internal cohesive strength is highly likely to occur.

[0105] Examples 10-13 investigated the effect of different molecular weights of polytetrafluoroethylene (PTFE) on the performance of copper-clad laminates. The results showed that lower molecular weight PTFE could better integrate with the copper foil teeth. At the same time, PTFE with even lower molecular weight had better integration and greater peel strength.

[0106] To further investigate the effect of polytetrafluoroethylene (PTFE) molecular weight on the performance of copper-clad laminates, the molecular weights of high-molecular-weight PTFE and low-molecular-weight PTFE were adjusted based on Examples 1, 12, and 13, and corresponding comparative examples 8-10 were set up. The main process parameters of comparative examples 8-10 are shown in Table 5.

[0107] Table 5 Main process parameters of Comparative Examples 8-10

[0108]

[0109] Similarly, the performance test results of the copper-clad laminates prepared in Comparative Examples 8 to 10 are shown in Table 6.

[0110] Table 6 shows the performance test results of the copper-clad laminates prepared in Comparative Examples 8-10.

[0111]

[0112]

[0113] Based on the performance changes of copper-clad laminates in Comparative Examples 8-10, the molecular weight of high-molecular-weight PTFE and low-molecular-weight PTFE affects the peel strength. Both excessively high and low molecular weights are detrimental to improving the peel strength of the copper-clad laminate. Considering the structural characteristics of PTFE, the following reasons may exist:

[0114] Polytetrafluoroethylene (PTFE) is a polymer whose molecular weight is determined by its degree of polymerization. High molecular weight PTFE molecules have restricted chain movement, making it difficult to form a good physical bond with the copper foil surface, resulting in weakened interfacial adhesion. Low molecular weight PTFE molecules have shorter chains and less interchain entanglement, leading to weaker cohesive strength. Furthermore, in PTFE copper-clad laminates, PTFE with excessively low molecular weight has poor interfacial adhesion to the substrate and is prone to delamination at the interface. Therefore, the molecular weight of PTFE should be strictly controlled in copper-clad laminate production.

[0115] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the embodiments described herein, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A copper-clad laminate with a fluororesin substrate, characterized in that, The adhesive film consists of a resin-coated copper foil prepared with fluororesin slurry A and a fluororesin slurry B, and the resin-coated copper foil and the adhesive film are laminated together. The resin-coated copper foil is formed by coating the rough surface of the copper foil with fluororesin slurry A, drying, and sintering in a nitrogen atmosphere; the adhesive film is formed by coating the release material with fluororesin slurry B, drying, and sintering. The fluororesin slurry A comprises the following components in weight percentage: Polytetrafluoroethylene slurry 25-40%, ceramic filler 55-75%, additives 0-5%; The fluororesin slurry B comprises the following components in weight percentage: 25-40% tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, 55-75% ceramic filler, and 0-5% additives; The polytetrafluoroethylene (PTFE) is composed of PTFE with relatively high molecular weight and PTFE with relatively low molecular weight. The PTFE with relatively high molecular weight refers to PTFE with a molecular weight of 2 million to 10 million, and the PTFE with relatively low molecular weight refers to PTFE with a molecular weight of 10,000 to 500,000.

2. The copper-clad laminate with a fluororesin substrate according to claim 1, characterized in that, The maximum temperature for laminating the resin-coated copper foil and adhesive film is between 320 and 340°C, the duration of holding the maximum temperature during lamination is 30 to 60 minutes, and the lamination pressure is 15 to 50 kg / cm². 2 .

3. The copper-clad laminate with a fluororesin substrate according to claim 1, characterized in that, The relatively high molecular weight polytetrafluoroethylene refers to polytetrafluoroethylene with a molecular weight of 5 million to 8 million; the relatively low molecular weight polytetrafluoroethylene refers to polytetrafluoroethylene with a molecular weight of 30,000 to 200,000.

4. The copper-clad laminate with a fluororesin substrate according to claim 1, characterized in that, The mass ratio of the relatively high molecular weight polytetrafluoroethylene to the relatively low molecular weight polytetrafluoroethylene is (3-7):(3-7).

5. The copper-clad laminate with a fluororesin substrate according to claim 1, characterized in that, The ceramic filler is any one or a mixture of at least two of the following: silicon dioxide, titanium dioxide, aluminum oxide, boron nitride, silicon nitride, and barium titanate.

6. The copper-clad laminate with a fluororesin substrate according to claim 1, characterized in that, The additive is a fluorinated silane coupling agent selected from trifluoropropylmethyldimethoxysilane and heptadecafluorodecyltrimethoxysilane; the release material is any one of polyimide film, aluminum foil, iron foil, and steel foil.

7. The copper-clad laminate with a fluororesin substrate according to claim 1, characterized in that, The drying temperature of the resin-coated copper foil is 50-150℃; the maximum sintering temperature is between 360-380℃, the holding time of the maximum temperature during sintering is 5-25 min, and the temperature is programmed during sintering, with a heating rate ≤2℃ / min in the temperature range of 320℃-340℃, preferably 1-2℃ / min.

8. The copper-clad laminate with a fluororesin substrate according to claim 1, characterized in that, The drying temperature of the adhesive film is 50-150℃; the maximum sintering temperature is between 360-380℃, the holding time of the maximum temperature during sintering is 5-25 min, and the temperature is programmed during sintering; preferably, the heating rate is ≤2℃ / min in the temperature range of 320℃-340℃, and more preferably 1-2℃ / min.

9. A method for preparing a copper-clad laminate with a fluororesin substrate according to any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Preparation of resin-coated copper foil and adhesive film; (2) Cut the resin-coated copper foil and adhesive film to the required size, and peel the adhesive film off the release material. The resin-coated copper foil and adhesive film are then laminated together. The structure from top to bottom is resin-coated copper foil / adhesive film / resin-coated copper foil. Depending on the thickness requirements, the middle layer adhesive film can be composed of one or more layers. (3) Place the above structure into a laminator, maintaining a maximum temperature between 320 and 340°C for 30 to 60 minutes and a pressure of 15 to 50 kg / cm². 2 Under certain conditions, copper-clad laminates with fluororesin substrates can be obtained by lamination.

10. The application of a fluoropolymer-based copper-clad laminate according to any one of claims 1 to 8 in the production of printed circuit boards.

Images