Special back-drilled composite aluminum foil for PCB (Printed Circuit Board) and preparation method thereof

Abstract

The invention discloses a special back-drilled composite aluminum foil for a PCB (Printed Circuit Board), which relates to the technical field of composite aluminum foils and comprises an aluminum foil layer, a hot-melt composite layer and a waterproof insulating layer which are sequentially laminated and attached, the hot-melt composite layer is prepared from the following components in percentage by weight: 40%-60% of hot-melt polymer particles, 15%-25% of a stabilizer, 10%-20% of nano reinforced particles and 5%-15% of an inorganic filler; the waterproof insulating layer is prepared from the following components in percentage by weight: 40%-50% of reinforced fiber fabric, 30%-40% of thermosetting resin, 8%-12% of a hydrophobic coupling agent and 8%-12% of nano filler. According to the back-drilled composite aluminum foil special for the PCB, the composite strength is improved, the defect of interlayer stripping is effectively overcome, and the occurrence rate of cloak and entangling is reduced; the waterproof performance is excellent, the moisture absorption problem of a traditional base material is solved, and the back drilling precision and the signal integrity are ensured.

Description

Technical Field

[0001] This invention relates to the field of composite aluminum foil technology, and in particular to a PCB-specific back-drill composite aluminum foil and its preparation method. Background Technology

[0002] In high-end PCB manufacturing, back-drilling is a crucial step in removing residual pads from through-holes to reduce signal interference and pinning effects. This process requires specialized composite aluminum foil as an entry or backup board to protect the PCB surface, absorb drilling heat, and prevent burrs. However, the glass fiber substrate in existing PCB-specific back-drilling composite aluminum foil is prone to moisture absorption, leading to interlayer delamination, and the composite interface has low strength, easily causing defects such as burrs (edge ​​warping) and entanglement (drill displacement), limiting its application in high-density, multilayer PCB processing. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a PCB-specific back-drilling composite aluminum foil and its preparation method. The specific technical solution is as follows: A PCB-specific back-drilling composite aluminum foil includes an aluminum foil layer, a hot-melt composite layer, and a waterproof insulating layer that are sequentially stacked and bonded together. The hot-melt composite layer is composed of the following components by weight percentage: 40%~60% hot-melt polymer particles, 15%~25% stabilizer, 10%~20% nano-reinforcing particles, and 5%~15% inorganic filler. The waterproof insulating layer is composed of the following components by weight percentage: 40%~50% reinforcing fiber fabric, 30%~40% thermosetting resin, 8%~12% hydrophobic coupling agent, and 8%~12% nano-filler.

[0004] Preferably: The hot-melt polymer particles are selected from PPS particles or PEEK particles, the stabilizer includes an antioxidant, the nano-reinforcing particles are nano-titanium dioxide particles, and the inorganic filler is calcium carbonate. The reinforcing fiber fabric is glass fiber fabric, the thermosetting resin is bisphenol A type epoxy resin, the hydrophobic coupling agent is silane coupling agent, and the nanofiller is nano-silica.

[0005] Preferably: The thickness of the aluminum foil layer is 0.1~0.12mm; The thickness of the waterproof insulation layer is 0.2~0.3mm.

[0006] The present invention also provides a preparation method for preparing PCB-specific back-drill composite aluminum foil as described in any one of the above claims, the preparation method comprising the following steps: S1. Hot melt polymer particles, stabilizers, nano-reinforcing particles, and inorganic fillers are mixed and then heated to melt to form a molten component; S2. The molten component is coated between the aluminum foil layer and the waterproof insulating layer to obtain a composite film layer; S3. The composite film layer is hot-pressed through multiple heating zones and then cooled and cured to obtain the final product.

[0007] Preferably, step S2, which involves coating the molten component between the aluminum foil layer and the waterproof insulating layer, specifically includes: The aluminum foil layer roll is placed at the first unwinding station, and the waterproof insulation layer is placed at the second unwinding station, wherein the first unwinding station and the second unwinding station are stacked one on top of the other. The aluminum foil layer roll and the waterproof insulation layer roll are unwound simultaneously, and the molten component is applied between the aluminum foil layer and the waterproof insulation layer by roller coating or doctor blade coating.

[0008] Preferably: In step S1, the heating temperature is 320~340℃, the heating time is 3~10min, and the viscosity of the molten component is 500~800mPa·s; In step S2, the coating amount of the molten component is 20~30 g / m². 2 ; In step S3, the number of heating zones is at least 5, and the heating temperatures of the 5 heating zones are 320~330℃, 330~335℃, 330~335℃, and 320~330℃ respectively. The hot pressing pressure is 2~5 MPa. The cooling and curing adopts water cooling method, the cooling temperature is controlled at 40~50℃, and the cooling time is 5~15 seconds.

[0009] Preferably, the waterproof insulating layer is prepared by the following steps: A thermosetting resin, a hydrophobic coupling agent, and nanofillers are mixed to form an impregnation solution; The reinforcing fiber fabric is immersed in the impregnation solution. The impregnation is carried out under vacuum with a pressure of -0.05 to -0.1 MPa and an impregnation time of 15 to 30 min. The impregnated reinforcing fiber fabric is dried and cured at 100~130℃ for 30~60 min to obtain the waterproof insulation layer.

[0010] Preferably, the number of heating zones is 7, and the heating temperatures of the 7 heating zones are 320℃, 330℃, 330℃, 333℃, 333℃, 333℃, and 330℃ respectively.

[0011] Preferably, the hot-melt polymer particles are selected from PPS particles, which are obtained by modifying the PPS particles through the following steps: PPS particles and diisopropylbenzene peroxide were mixed evenly at a mass ratio of 100:(0.5~2); The mixture is heated to 310-350℃ in an extruder to melt and react, and then extruded. The extrudate was cooled, solidified, and then pulverized to obtain modified PPS particles with a particle size of 50~200μm.

[0012] Preferably, the stabilizer further includes a heat stabilizer and a flame retardant, wherein the heat stabilizer is selected from calcium stearate and the flame retardant is selected from ammonium polyphosphate.

[0013] The PCB-specific back-drill composite aluminum foil provided by this invention has the following beneficial effects: 1. Improved composite strength effectively solves interlayer delamination defects and reduces the incidence of sheathing and entanglement.

[0014] 2. Excellent waterproof performance, overcoming the moisture absorption problem of traditional substrates, ensuring back-drilling accuracy and signal integrity. Detailed Implementation

[0015] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0016] This embodiment provides a PCB-specific back-drilling composite aluminum foil, comprising an aluminum foil layer, a hot-melt composite layer, and a waterproof insulating layer, which are sequentially stacked and bonded together. The hot-melt composite layer is composed of the following components by weight percentage: 40%~60% hot-melt polymer particles, 15%~25% stabilizer, 10%~20% nano-reinforcing particles, and 5%~15% inorganic filler. The waterproof insulating layer is composed of the following components by weight percentage: 40%~50% reinforcing fiber fabric, 30%~40% thermosetting resin, 8%~12% hydrophobic coupling agent, and 8%~12% nano-filler.

[0017] The aluminum foil layer provides electromagnetic shielding and thermal conductivity, serving as the outer layer that directly contacts the drill bit. The hot-melt composite layer acts as an intermediate bonding interface, melting and penetrating under hot pressure. Nanoparticles and inorganic fillers disperse stress, forming a high-strength bonded network to prevent interlayer slippage. The waterproof insulating layer serves as the inner support layer, cured after vacuum impregnation. A hydrophobic coupling agent reduces surface energy, and nanofillers fill micropores, forming a hydrophobic barrier. During back-drilling, the hot-melt layer uniformly buffers the drilling impact, while the waterproof layer blocks moisture intrusion, achieving gradient optimization from the material interface to overall performance.

[0018] The PCB-specific back-drilling composite aluminum foil provided in this embodiment has the following beneficial effects: 1. Improved composite strength effectively solves interlayer delamination defects and reduces the incidence of sheathing and entanglement.

[0019] 2. Excellent waterproof performance, overcoming the moisture absorption problem of traditional substrates, ensuring back-drilling accuracy and signal integrity.

[0020] Furthermore: The hot-melt polymer particles are selected from PPS particles or PEEK particles, the stabilizers include antioxidants, the nano-reinforcing particles are nano-titanium dioxide particles, and the inorganic filler is calcium carbonate.

[0021] The reinforcing fiber fabric is glass fiber fabric, the thermosetting resin is bisphenol A type epoxy resin, the hydrophobic coupling agent is silane coupling agent, and the nanofiller is nano silica.

[0022] The hot-melt polymer particles, selected from PPS or PEEK particles, form a low-volatility melt upon heating and melting. This melt, in conjunction with the stabilizer, captures free radicals and inhibits oxidative degradation. Nano-reinforcing particles, acting as the dispersed phase, improve the melt's rheological properties and promote uniform particle distribution under hot pressing, forming a three-dimensional network structure. Inorganic fillers regulate viscosity, reduce internal stress, and prevent phase separation. Simultaneously, the reinforcing fiber fabric in the waterproof insulation layer provides a high-modulus skeleton. The thermosetting resin, after vacuum impregnation and curing, cross-links into a network. A hydrophobic coupling agent bridges the fiber-resin interface, and nanofillers fill micro-gaps, forming a hydrophobic surface. These components, through chemical bonding and physical dispersion, ensure that the composite layer exhibits no interfacial failure under back-drilling impact.

[0023] Furthermore: The aluminum foil layer thickness is 0.1~0.12mm.

[0024] The thickness of the waterproof insulation layer is 0.2~0.3mm.

[0025] This embodiment also provides a preparation method for preparing PCB-specific back-drill composite aluminum foil as described in any of the above embodiments. The preparation method includes the following steps: S1. Hot melt polymer particles, stabilizers, nano-reinforcing particles, and inorganic fillers are mixed and then heated to melt to form a molten component.

[0026] S2. The molten component is coated between the aluminum foil layer and the waterproof insulation layer to obtain a composite film layer.

[0027] S3. The composite film is hot-pressed through multiple heating zones and then cooled and cured to obtain the final product.

[0028] In step S1, hot-melt polymer particles are mixed with stabilizers, nano-reinforcing particles and inorganic fillers, and heated to melt to form a low-volatility melt. The stabilizers inhibit free radical polymerization, and the nanoparticles regulate rheology. In step S2, the molten components are coated between the aluminum foil layer and the waterproof insulation layer to form a pre-composite film layer, which is driven by surface tension and capillary action. In step S3, under hot pressing in multiple heating zones, molecular chain diffusion and cross-linking are promoted, and water cooling solidifies the structure to quickly freeze it and avoid residual stress.

[0029] Furthermore, step S2, which involves coating the molten component between the aluminum foil layer and the waterproof insulating layer, specifically includes: The aluminum foil layer roll is placed at the first unwinding station, and the waterproof insulation layer is placed at the second unwinding station, wherein the first unwinding station and the second unwinding station are stacked one on top of the other.

[0030] The aluminum foil layer roll and the waterproof insulation layer roll are unwound simultaneously, and the molten components are applied between the aluminum foil layer and the waterproof insulation layer by roller coating or doctor blade coating.

[0031] Furthermore: In step S1, the heating temperature is 320~340℃, the heating time is 3~10min, and the viscosity of the molten component is 500~800mPa·s.

[0032] In step S2, the coating amount of the molten component is 20~30 g / m². 2 .

[0033] In step S3, the number of heating zones is at least 5, and the heating temperatures of the 5 heating zones are 320~330℃, 330~335℃, 330~335℃, and 320~330℃ respectively, with a hot pressing pressure of 2~5 MPa. Cooling and curing are carried out using water cooling, with the cooling temperature controlled at 40~50℃ and the cooling time at 5~15 seconds.

[0034] In step S3, a multi-segment heating zone constructs a precise thermal gradient field, achieving a gradual process from preheating to peak fusion: the first segment (320~330℃) pre-melts the hot-melt components to avoid cold adhesion; the three middle platform segments (330~335℃) extend the residence time, promoting molecular chain diffusion and uniform distribution of nano-reinforcing particles to form a cross-linked network. The platform design suppresses temperature overshoot and prevents local overheating-induced oxidation; the final segment (320~330℃) gradually decreases to release residual heat and reduce warpage. Water-cooled solidification induces rapid quenching, freezing the microstructure.

[0035] Furthermore, the waterproof insulating layer is prepared through the following steps: Thermosetting resin, hydrophobic coupling agent and nanofiller are mixed to form an impregnation solution.

[0036] The reinforcing fiber fabric is immersed in the impregnation solution under vacuum, with a pressure of -0.05 to -0.1 MPa and an immersion time of 15 to 30 minutes.

[0037] The impregnated reinforcing fiber fabric is dried and cured at 100~130℃ for 30~60 minutes to obtain a waterproof insulation layer.

[0038] The process involves three steps: First, a thermosetting resin (bisphenol A epoxy), a hydrophobic coupling agent (silane), and nanofiller (SiO2) are mixed to form an impregnation solution. The nanofiller is uniformly suspended, and the coupling agent is hydrolyzed into silanol groups to prepare for subsequent bridging. Second, a reinforcing fiber fabric (glass fiber) is impregnated in the solution. Air bubbles are removed under vacuum conditions, driving the resin to penetrate the fiber pores. The silane coupling agent chemically bonds the fiber-SiO2-resin to form a hydrophobic network. Third, the process involves drying and curing at 100~130℃ to induce an epoxy crosslinking reaction. Nano-SiO2 acts as a nucleating agent to accelerate crystallization, resulting in an overall layer thickness of 0.2~0.3 mm.

[0039] Furthermore, the heating zone has 7 sections, and the heating temperatures of the 7 sections are 320℃, 330℃, 330℃, 333℃, 333℃, and 330℃ respectively.

[0040] The first section preheats and softens the waterproof layer at 320℃; the double 330℃ fusion platform extends the melting residence, stabilizes the rheology of the hot melt components, and promotes the dispersion of nano-TiO2; the three 333℃ peak platforms maximize cross-linking and form a high-density network; and the final section gradually decreases to 330℃ to release thermal stress and prevent overcooling cracks.

[0041] Furthermore, the hot-melt polymer particles are selected from PPS particles, which are obtained through the following steps of modification: PPS particles and diisopropylbenzene peroxide were mixed evenly at a mass ratio of 100:(0.5~2).

[0042] The mixture is heated to 310-350°C in an extruder to melt and react, and then extruded.

[0043] The extrudate was cooled, solidified, and then pulverized to obtain modified PPS particles with a particle size of 50~200μm.

[0044] In this process, DCP (diisopropylbenzene peroxide) thermally decomposes during extrusion modification to generate free radicals, which induce β-cleavage and reconstruction of PPS chains, forming a network cross-linked structure, increasing the glass transition temperature and thermal decomposition threshold, and inhibiting oxidation chain reaction. The modified PPS particles maintain low volatility during heating and melting in step S1, and work synergistically with stabilizers / nano-reinforcing particles to regulate rheology and promote coating penetration in step S2. Under multi-stage hot pressing in step S3, the cross-linked network buffers stress, enhances interlayer bonding, and ensures that PPS forms a gradient buffer zone at the interface of the waterproof insulation layer.

[0045] Furthermore, the stabilizer also includes a heat stabilizer and a flame retardant, wherein the heat stabilizer is selected from calcium stearate and the flame retardant is selected from ammonium polyphosphate.

[0046] Among them, antioxidants capture free radicals, calcium stearate complexes acidic degradation products, and inhibits catalytic oxidation; ammonium polyphosphate phosphorylates PPS chains under hot pressing to form a carbonization barrier, which synergistically provides thermal shielding for nano-TiO2. These additives are compatiblely dispersed under melting in step S1, reducing activation energy, ensuring no volatilization of the melt, and enhancing the interfacial carbon layer under hot pressing in step S3.

[0047] Specific embodiments are provided below. These embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way.

[0048] Example 1 On a magnetic stirrer, 101.5g of bisphenol A epoxy resin, 29.0g of silane coupling agent, and 43.5g of nano-silica were added to 145mL of ethanol solvent. The stirring speed was 300rpm, the temperature was 25℃, and the mixture was stirred for 25min to form a uniform impregnation solution with no visible agglomeration. 116g of glass fiber fabric (pre-dried in an oven at 80℃ for 35min) was placed in a vacuum impregnation chamber, and the impregnation solution was poured in to cover the fabric. The vacuum degree was -0.08 MPa, and the impregnation time was 22min. During this period, bubbles were observed to be expelled, and the impregnation was saturated. The fabric was removed, excess liquid was drained, and the fabric was placed in an oven at 120℃ for drying and curing for 50min (turning it over every 15min to ensure uniformity). After cooling to room temperature, a 0.25mm thick waterproof insulation layer was obtained, with a smooth surface and no cracks.

[0049] Weigh 145.0 g of PEEK particles, 58.0 g of Irganox 1010 antioxidant, 43.5 g of nano-titanium dioxide particles, and 43.5 g of calcium carbonate. Add 30 mL of ethanol and premix. Stir magnetically at 250 rpm for 6 min at room temperature. Transfer to a heated mixing vessel, heat at a rate of 5 °C / min to 332 °C, stirring at 160 rpm for 7 min, until a molten component is formed. Nitrogen gas is used for protection during this process (flow rate 0.6 L / min), and no obvious bubbles are generated.

[0050] Take 0.58m 2Clean the surface of the 0.1mm thick aluminum foil with ethanol, and apply a release agent to the back. Apply approximately 58g of the molten component evenly to the front of the aluminum foil using a spatula, spreading it manually. Immediately layer a waterproof insulating layer onto the coated surface, apply a pre-pressure of 1.2MPa, and allow it to stand at room temperature for 3 minutes for initial adhesion. Transfer to a flatbed hot press and simulate 7 heating stages: Stage 1 (320℃, preheating 2.5min); Stages 2-3 (330℃, fusion 5min); Stages 4-6 (333℃, peak 7min); Stage 7 (330℃, transition 3.5min); total hot pressing pressure 3.5 MPa, static residence 18s / stage composite speed simulation. Immediately after hot pressing, water cool (42℃), and cool to room temperature to obtain a composite aluminum foil sample. Visually, there is no warping, and the surface is smooth.

[0051] Peel strength test after damp heat: Cut sample strips (25 mm wide and 150 mm long); expose to constant temperature and humidity chamber at 85℃ / 85%RH for 168 h, cool for 30 min; peel and clamp at 180° (initial distance 100 mm); stretch at a speed of 50 mm / min; calculate the average N / cm.

[0052] Dry peel strength test: Sample strip (25mm wide, 150mm long); 180° clamping (initial distance 100mm); tensile test at a speed of 50mm / min, calculate average N / cm.

[0053] Back-drilling simulated defect rate test: Sample fixed to PCB stack (1.6mm thick), marked with a 50-hole grid; drilling (speed 2m / min, rotation speed 2000rpm); microscopic inspection of the hole perimeter (1mm). 2 (Field of view), measure tarpaulin (>0.05mm warping) and tangling (>0.1mm offset); calculate defect rate.

[0054] The test data is shown in Table 1 below.

[0055] Example 2 101.5 g of bisphenol A epoxy resin, 29.0 g of silane coupling agent, and 43.5 g of nano-silica were added to 145 mL of ethanol solvent and stirred at 300 rpm for 25 min (25°C) on a magnetic stirrer to form a homogeneous impregnation solution with no visible agglomeration. 116 g of glass fiber fabric (pre-dried in an oven at 80°C for 35 min) was placed in a vacuum impregnation chamber, and the impregnation solution was poured in to cover the fabric. The fabric was impregnated under a vacuum of -0.08 MPa for 22 min, during which time air bubbles were observed to escape, until the impregnation was saturated. The fabric was removed, excess liquid was drained, and the fabric was dried and cured in an oven at 120°C for 50 min (turned over every 15 min to ensure uniformity). After cooling to room temperature, a waterproof insulation layer with a thickness of 0.25 mm was obtained, with a smooth surface and no cracks.

[0056] Weigh 145.0 g of PPS particles, 58.0 g of Irganox 1010 antioxidant, 43.5 g of nano-titanium dioxide particles, and 43.5 g of calcium carbonate. Add 30 mL of ethanol and premix. Stir at 250 rpm for 6 min (room temperature) on a magnetic stirrer. Transfer to a heated mixing vessel and heat to 332 °C at a heating rate of 5 °C / min. Stir at 160 rpm for 7 min to form a molten component. During this process, maintain nitrogen protection at a flow rate of 0.6 L / min. No significant bubbles were generated.

[0057] Take 0.58 m 2 The aluminum foil (0.1 mm thick) was cleaned by wiping its surface with ethanol, and a release agent was applied to the back. Approximately 58 g of the molten component was evenly spread on the front side of the aluminum foil using a spatula and manually spread. The waterproof insulating layer was immediately laminated onto the coated surface, and a pre-pressure of 1.2 MPa was applied. The foil was allowed to stand at room temperature for 3 minutes for initial bonding. The foil was then transferred to a flatbed hot press, simulating 7 heating stages: Stage 1 (320℃, preheating for 2.5 min); Stages 2-3 (330℃, fusion for 5 min); Stages 4-6 (333℃, peak for 7 min); Stage 7 (330℃, transition for 3.5 min); the total hot pressing pressure was 3.5 MPa, and the static residence time was 18 s / stage (simulating the composite speed). After hot pressing, the foil was immediately water-cooled (42℃ water) to room temperature to obtain the composite aluminum foil sample, which was visually inspected for no warping and had a smooth surface.

[0058] The test items and test methods are the same as in Example 1, and the test data are shown in Table 2 below.

[0059] Example 3 101.5 g of bisphenol A epoxy resin, 29.0 g of silane coupling agent, and 43.5 g of nano-silica were added to 145 mL of ethanol solvent and stirred at 300 rpm for 25 min (25°C) on a magnetic stirrer to form a homogeneous impregnation solution with no visible agglomeration. 116 g of glass fiber fabric (pre-dried in an oven at 80°C for 35 min) was placed in a vacuum impregnation chamber, and the impregnation solution was poured in to cover the fabric. The fabric was impregnated under a vacuum of -0.08 MPa for 22 min, during which time air bubbles were observed to escape, until the impregnation was saturated. The fabric was removed, excess liquid was drained, and the fabric was dried and cured in an oven at 120°C for 50 min (turned over every 15 min to ensure uniformity). After cooling to room temperature, a waterproof insulation layer with a thickness of 0.25 mm was obtained, with a smooth surface and no cracks.

[0060] 290 g of PPS granules were weighed and mixed evenly with 2.9 g of dicumyl peroxide (DCP). The mixture was heated to 330 °C in an extruder for 3 min to melt and react. After the reaction, the mixture was extruded, and the extrudate was water-cooled, solidified, and then pulverized to obtain modified PPS granules. 145.0 g of modified PPS granules, 58.0 g of Irganox 1010 antioxidant, 43.5 g of nano-titanium dioxide granules, and 43.5 g of calcium carbonate were added to 30 mL of ethanol for premixing. The mixture was stirred at 250 rpm for 6 min (room temperature) on a magnetic stirrer. The mixture was then transferred to a heated mixing vessel and heated to 332 °C at a heating rate of 5 °C / min. The mixture was stirred at 160 rpm for 7 min to form a molten component. Nitrogen protection was maintained during the process, with a flow rate of 0.6 L / min. No significant bubbles were generated.

[0061] Take 0.58 m 2 The aluminum foil (0.1 mm thick) was cleaned by wiping its surface with ethanol, and a release agent was applied to the back. Approximately 58 g of the molten component was evenly spread on the front side of the aluminum foil using a spatula and manually spread. The waterproof insulating layer was immediately laminated onto the coated surface, and a pre-pressure of 1.2 MPa was applied. The foil was allowed to stand at room temperature for 3 min for initial bonding. The foil was then transferred to a flatbed hot press, simulating 7 heating stages: Stage 1 (320℃, preheating for 2.5 min); Stages 2-3 (330℃, fusion for 5 min); Stages 4-6 (333℃, peak for 7 min); Stage 7 (330℃, transition for 3.5 min); the total hot pressing pressure was 3.5 MPa, and the static residence time was 18 s / stage (simulating the composite speed). After hot pressing, the foil was immediately water-cooled (42℃ water) to room temperature, yielding a composite aluminum foil sample with a total thickness of 0.36 mm. Visually, there was no warping, and the surface was smooth.

[0062] The test items and test methods are the same as in Example 1, and the test data are shown in Table 3 below.

[0063] Example 4 101.5 g of bisphenol A epoxy resin, 29.0 g of silane coupling agent, and 43.5 g of nano-silica were added to 145 mL of ethanol solvent and stirred at 300 rpm for 25 min (25°C) on a magnetic stirrer to form a homogeneous impregnation solution with no visible agglomeration. 116 g of glass fiber fabric (pre-dried in an oven at 80°C for 35 min) was placed in a vacuum impregnation chamber, and the impregnation solution was poured in to cover the fabric. The fabric was impregnated under a vacuum of -0.08 MPa for 22 min, during which time air bubbles were observed to escape, until the impregnation was saturated. The fabric was removed, excess liquid was drained, and the fabric was dried and cured in an oven at 120°C for 50 min (turned over every 15 min to ensure uniformity). After cooling to room temperature, a waterproof insulation layer with a thickness of 0.25 mm was obtained, with a smooth surface and no cracks.

[0064] 290 g of PPS granules were weighed and mixed evenly with 2.9 g of dicumyl peroxide (DCP). The mixture was heated to 330 °C in an extruder for 3 min to melt and react. After the reaction, the mixture was extruded, and the extrudate was water-cooled, solidified, and then pulverized to obtain modified PPS granules. 139.2 g of modified PPS granules, 52.2 g of Irganox 1010 antioxidant, 5.8 g of calcium stearate, 8.7 g of ammonium polyphosphate, 43.5 g of nano-titanium dioxide granules, and 40.6 g of calcium carbonate were added to 30 mL of ethanol for premixing. The mixture was stirred at 250 rpm for 6 min (room temperature) on a magnetic stirrer. The mixture was then transferred to a heated mixing vessel and heated to 332 °C at a heating rate of 5 °C / min. The mixture was stirred at 160 rpm for 7 min to form a molten component. Nitrogen protection was maintained during the process, with a flow rate of 0.6 L / min. No significant bubbles were generated.

[0065] Take 0.58 m 2 The aluminum foil (0.1 mm thick) was cleaned by wiping its surface with ethanol, and a release agent was applied to the back. Approximately 58 g of the molten component was evenly spread on the front side of the aluminum foil using a spatula and manually spread. The waterproof insulating layer was immediately laminated onto the coated surface, and a pre-pressure of 1.2 MPa was applied. The foil was allowed to stand at room temperature for 3 min for initial bonding. The foil was then transferred to a flatbed hot press, simulating 7 heating stages: Stage 1 (320℃, preheating for 2.5 min); Stages 2-3 (330℃, fusion for 5 min); Stages 4-6 (333℃, peak for 7 min); Stage 7 (330℃, transition for 3.5 min); the total hot pressing pressure was 3.5 MPa, and the static residence time was 18 s / stage (simulating the composite speed). After hot pressing, the foil was immediately water-cooled (42℃ water) to room temperature, yielding a composite aluminum foil sample with a total thickness of 0.36 mm. Visually, there was no warping, and the surface was smooth.

[0066] The test items and test methods are the same as in Example 1, and the test data are shown in Table 4 below.

[0067] Comparative Example 1 174.0 g of bisphenol A epoxy resin was added to 145 mL of ethanol solvent and stirred at 300 rpm for 25 min (25°C) on a magnetic stirrer to form an impregnation solution, which showed no visible agglomeration. 116 g of glass fiber fabric (pre-dried in an oven at 80°C for 35 min) was placed in a vacuum impregnation chamber, and the impregnation solution was poured in to cover the fabric. The fabric was impregnated under a vacuum of -0.08 MPa for 22 min, during which time air bubbles were observed to escape, until the impregnation was saturated. The fabric was removed, excess liquid was drained, and the fabric was dried and cured in an oven at 120°C for 50 min (turning it over every 15 min to ensure uniformity). After cooling to room temperature, a waterproof insulation layer with a thickness of 0.25 mm was obtained, with a smooth surface and no cracks.

[0068] Take 0.58 m 2 The surface of the aluminum foil (0.1 mm thick) was cleaned by wiping with ethanol, and a release agent was applied to the back. A waterproof insulating layer was directly laminated onto the aluminum foil, and a pre-pressure of 1.2 MPa was applied. The foil was allowed to stand at room temperature for 3 minutes for initial adhesion. The foil was then transferred to a flatbed hot press and hot-pressed at 300°C for 15 minutes at a pressure of 3.5 MPa. Immediately after hot pressing, the foil was water-cooled (to 42°C) to room temperature, yielding a composite aluminum foil sample with a total thickness of 0.35 mm. Visually, no warping was observed, and the surface was smooth.

[0069] The test items and test methods are the same as in Example 1, and the test data are shown in Table 5 below.

[0070] Comparative Example 2 101.5 g of bisphenol A epoxy resin, 29.0 g of silane coupling agent, and 43.5 g of nano-silica were added to 145 mL of ethanol solvent and stirred at 300 rpm for 25 min (25°C) on a magnetic stirrer to form a homogeneous impregnation solution with no visible agglomeration. 116 g of glass fiber fabric (pre-dried in an oven at 80°C for 35 min) was placed in a vacuum impregnation chamber, and the impregnation solution was poured in to cover the fabric. The fabric was impregnated under a vacuum of -0.08 MPa for 22 min, during which time air bubbles were observed to escape, until the impregnation was saturated. The fabric was removed, excess liquid was drained, and the fabric was dried and cured in an oven at 120°C for 50 min (turned over every 15 min to ensure uniformity). After cooling to room temperature, a waterproof insulation layer with a thickness of 0.25 mm was obtained, with a smooth surface and no cracks.

[0071] Weigh 145.0 g of PEEK particles, 58.0 g of Irganox 1010 antioxidant, 43.5 g of nano-titanium dioxide particles, and 43.5 g of calcium carbonate. Add 30 mL of ethanol and premix. Stir at 250 rpm for 6 min (room temperature) on a magnetic stirrer. Transfer to a heated mixing vessel and heat to 332 °C at a heating rate of 5 °C / min. Stir at 160 rpm for 7 min to form a molten component. During this process, maintain nitrogen protection at a flow rate of 0.6 L / min. No significant bubbles were generated.

[0072] Take 0.58 m 2 Clean the surface of the aluminum foil (0.1 mm thick) with ethanol, and apply a release agent to the back. Apply approximately 58 g of the molten component evenly to the front of the aluminum foil using a spatula, spreading it manually. Immediately layer a waterproof insulating layer onto the coated surface, apply a pre-pressure of 1.2 MPa, and allow it to stand at room temperature for 3 minutes for initial adhesion. Transfer to a flatbed hot press and hot press at 300°C for 15 minutes at a pressure of 3.5 MPa. Immediately after hot pressing, water cool (42°C water) to room temperature to obtain a composite aluminum foil sample with a total thickness of 0.36 mm. Visually, there is no warping, and the surface is smooth.

[0073] The test items and test methods are the same as in Example 1, and the test data are shown in Table 6 below.

[0074] The data above show that the average peel strength after wet heat in Examples 1-4 is 57.0 N / cm, with a decay rate of <10%, effectively blocking moisture penetration; Comparative Example 1 is only 24.5 N / cm, and Comparative Example 2 is 45.4 N / cm, verifying that the hydrophobic mechanism solves the moisture absorption problem. The average dry peel strength in Examples 1-4 is 60.6 N / cm, while Comparative Example 1 is only 30.0 N / cm, and Comparative Example 2 is 53.5 N / cm, confirming that hot-melt + modified PPS solves the low strength problem. The average back-drilling simulated defect rate in Examples 1-4 is 0.9%, while Comparative Example 1 is 4.0%; Comparative Example 2 is 2.3%, verifying that the multi-stage hot-pressing mechanism + modified components solve the processing defect problem.

[0075] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be within the scope of protection of the present invention.

Claims

1. A PCB-specific back-drill composite aluminum foil, characterized in that, The material comprises, in sequence, an aluminum foil layer, a hot-melt composite layer, and a waterproof insulating layer; the hot-melt composite layer is composed of the following components by weight percentage: 40%~60% hot-melt polymer particles, 15%~25% stabilizer, 10%~20% nano-reinforcing particles, and 5%~15% inorganic filler; the waterproof insulating layer is composed of the following components by weight percentage: 40%~50% reinforcing fiber fabric, 30%~40% thermosetting resin, 8%~12% hydrophobic coupling agent, and 8%~12% nano-filler.

2. The PCB-specific back-drill composite aluminum foil according to claim 1, characterized in that: The hot-melt polymer particles are selected from PPS particles or PEEK particles, the stabilizer includes an antioxidant, the nano-reinforcing particles are nano-titanium dioxide particles, and the inorganic filler is calcium carbonate. The reinforcing fiber fabric is glass fiber fabric, the thermosetting resin is bisphenol A type epoxy resin, the hydrophobic coupling agent is silane coupling agent, and the nanofiller is nano-silica.

3. The PCB-specific back-drill composite aluminum foil according to claim 1, characterized in that: The thickness of the aluminum foil layer is 0.1~0.12mm; The thickness of the waterproof insulation layer is 0.2~0.3mm.

4. A preparation method, characterized in that, The method for preparing the PCB-specific back-drill composite aluminum foil as described in any one of claims 1 to 3 includes the following steps: S1. Hot melt polymer particles, stabilizers, nano-reinforcing particles, and inorganic fillers are mixed and then heated to melt to form a molten component; S2. The molten component is coated between the aluminum foil layer and the waterproof insulating layer to obtain a composite film layer; S3. The composite film layer is hot-pressed through multiple heating zones and then cooled and cured to obtain the final product.

5. The preparation method according to claim 4, characterized in that, Step S2, which involves coating the molten component between the aluminum foil layer and the waterproof insulating layer, specifically includes: The aluminum foil layer roll is placed at the first unwinding station, and the waterproof insulation layer is placed at the second unwinding station, wherein the first unwinding station and the second unwinding station are stacked one on top of the other. The aluminum foil layer roll and the waterproof insulation layer roll are unwound simultaneously, and the molten component is applied between the aluminum foil layer and the waterproof insulation layer by roller coating or doctor blade coating.

6. The preparation method according to claim 4, characterized in that: In step S1, the heating temperature is 320~340℃, the heating time is 3~10min, and the viscosity of the molten component is 500~800mPa·s; In step S2, the coating amount of the molten component is 20~30 g / m². 2 ; In step S3, the number of heating zones is at least 5, and the heating temperatures of the 5 heating zones are 320~330℃, 330~335℃, 330~335℃, and 320~330℃ respectively. The hot pressing pressure is 2~5 MPa. The cooling and curing adopts water cooling method, the cooling temperature is controlled at 40~50℃, and the cooling time is 5~15 seconds.

7. The preparation method according to claim 4, characterized in that, The waterproof insulating layer is prepared by the following steps: A thermosetting resin, a hydrophobic coupling agent, and nanofillers are mixed to form an impregnation solution; The reinforcing fiber fabric is immersed in the impregnation solution. The impregnation is carried out under vacuum with a pressure of -0.05 to -0.1 MPa and an impregnation time of 15 to 30 min. The impregnated reinforcing fiber fabric is dried and cured at 100~130℃ for 30~60 min to obtain the waterproof insulation layer.

8. The preparation method according to claim 6, characterized in that, The number of heating zones is 7, and the heating temperatures of the 7 heating zones are 320℃, 330℃, 330℃, 333℃, 333℃, 333℃, and 330℃ respectively.

9. The preparation method according to claim 4, characterized in that, The hot-melt polymer particles are selected from PPS particles, which are obtained by modifying the PPS particles through the following steps: PPS particles and diisopropylbenzene peroxide were mixed evenly at a mass ratio of 100:(0.5~2); The mixture is heated to 310-350℃ in an extruder to melt and react, and then extruded. The extrudate was cooled, solidified, and then pulverized to obtain modified PPS particles with a particle size of 50~200μm.

10. The preparation method according to claim 9, characterized in that, The stabilizer also includes a heat stabilizer and a flame retardant, wherein the heat stabilizer is selected from calcium stearate and the flame retardant is selected from ammonium polyphosphate.

Images