Memory material base plate for PCB drilling and preparation method thereof

Abstract

The invention belongs to the technical field of PCB processing, and discloses a memory material base plate for PCB drilling and a preparation method thereof, the memory material base plate comprises the following raw materials by weight: 40-50 parts of ultra-high molecular weight polyethylene, 20-30 parts of EVA, 10-15 parts of low density polyethylene, 2-3 parts of modified hexagonal boron nitride, 3-4 parts of a toughening additive, 3-5 parts of a nucleating agent, 0.5-1.5 parts of a lubricant, and 0.1-0.3 part of an antioxidant; the ultrahigh molecular weight polyethylene, the EVA and the low-density polyethylene are blended to realize the characteristics of high toughness and rapid melting recovery, and meanwhile, the modified hexagonal boron nitride and the toughening additive are added for synergistic modification, so that the heat-conducting network construction and interface toughening and strengthening are realized, and the heat-conducting property is greatly improved. And good thermal conductivity, appropriate rigidity and toughness and an excellent burr inhibiting effect are achieved.

Description

Technical Field

[0001] This invention belongs to the field of PCB processing technology, specifically relating to a memory material pad for PCB drilling and its preparation method. Background Technology

[0002] With the rapid development of industries such as 5G communication, artificial intelligence, high-performance computing, and automotive electronics, PCBs are rapidly evolving towards high-density interconnect (HDI), multilayering, and miniaturization. Microvias with diameters less than 0.15mm have become standard in high-end PCBs. This presents unprecedented challenges to the quality of the drilling process, especially in controlling exit burrs and hole wall quality, which directly affect the electrical performance and reliability of the final product.

[0003] PCB drilling pads are essential auxiliary materials in the PCB drilling process. Placed under the PCB board, they play a crucial role in improving drilling quality and protecting the drill bit. Currently, commonly used PCB drilling pads include aluminum foil pads and wood pulp pads. Aluminum foil pads have high hardness but limited burr suppression capabilities, easily damaging the drill bit and potentially introducing metal contamination. Wood pulp pads have uneven material composition, poor cleaning ability, and are prone to generating drill smudges, while offering limited improvement in drill bit life. Therefore, there is an urgent need to develop a new type of PCB drilling pad that simultaneously addresses the problems of poor thermal conductivity, inadequate rigidity and toughness, high wear, and poor burr suppression, thereby improving PCB drilling efficiency and product yield. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a memory material pad for PCB drilling and its preparation method. The pad is made by blending ultra-high molecular weight polyethylene, EVA, and low-density polyethylene to achieve high toughness and rapid melt recovery characteristics. Simultaneously, modified hexagonal boron nitride and toughening additives are added for synergistic modification. Through the construction of a thermally conductive network and interface toughening enhancement, good thermal conductivity, suitable rigidity and toughness, and excellent burr suppression effect are achieved.

[0005] The objective of this invention can be achieved through the following technical solutions: A memory material pad for PCB drilling comprises the following raw materials in parts by weight: 40-50 parts ultra-high molecular weight polyethylene, 20-30 parts EVA, 10-15 parts low-density polyethylene, 2-3 parts modified hexagonal boron nitride, 3-4 parts toughening additive, 3-5 parts nucleating agent, 0.5-1.5 parts lubricant, and 0.1-0.3 parts antioxidant; The modified hexagonal boron nitride is produced by in-situ polymerization of a hydroxyl-terminated polybutadiene elastic layer onto the surface of hexagonal boron nitride, followed by grafting graphene oxide onto the surface using a silane coupling agent. The toughening additive is an organic-inorganic hybrid particle formed by surface modification of nano-silicon carbide with silane coupling agent and maleic anhydride-grafted polyolefin elastomer.

[0006] Preferably, the nucleating agent is a mixture of di(3,4-dimethylbenzyl)sorbitol and talc in a mass ratio of 1:9.

[0007] Preferably, the lubricant is a compound of zinc stearate and silicone masterbatch in a mass ratio of 2:1.

[0008] Preferably, the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0009] Preferably, the preparation method of modified hexagonal boron nitride includes the following steps: (1) Add hexagonal boron nitride to deionized water and ultrasonically disperse for 20-40 min to form a suspension. Add concentrated nitric acid, heat to 80℃ and stir for 3-5 h. After the reaction is complete, wash with deionized water by centrifugation until the pH is neutral, and vacuum dry at 60℃ for 10-12 h to obtain hydroxylated hexagonal boron nitride. (2) Hydroxylated hexagonal boron nitride was added to anhydrous ethanol and ultrasonically dispersed for 15-25 min. Hydroxyl-terminated polybutadiene and benzoyl peroxide were added. The mixture was heated to 70°C under nitrogen protection and stirred for 2-4 h. After the reaction was completed, the mixture was centrifuged, washed three times with anhydrous ethanol, and vacuum dried at 80°C for 4-6 h to obtain hexagonal boron nitride coated with hydroxyl-terminated polybutadiene. (3) Add graphene oxide to deionized water and ultrasonically exfoliate for 20-30 min to obtain graphene oxide dispersion. Add 3-glycidyl etheroxypropyltrimethoxysilane, adjust the pH to 4-5 with dilute hydrochloric acid, stir at 60℃ for 1.5-2.5 h, then add hexagonal boron nitride coated with hydroxyl-terminated polybutadiene, heat to 80℃ and stir for 3-5 h. After the reaction, centrifuge, wash with deionized water until neutral, and vacuum dry at 100℃ for 8-10 h to obtain modified hexagonal boron nitride.

[0010] Preferably, the mass ratio of hydroxylated hexagonal boron nitride to hydroxyl-terminated polybutadiene is 5:2, benzoyl peroxide accounts for 2.5% of the mass of hydroxyl-terminated polybutadiene, and the mass ratio of graphene oxide, 3-glycidyl etheroxypropyltrimethoxysilane, and hydroxyl-terminated polybutadiene-coated hexagonal boron nitride is 1:2.5:30.

[0011] Preferably, the method for preparing the toughening additive includes the following steps: A. Add nano-silicon carbide to acetone, ultrasonically disperse for 10-20 min, add 3-(methacryloyloxy)propyltrimethoxysilane, reflux and stir at 60℃ for 2-4 h, centrifuge, wash twice with acetone, and vacuum dry at 80℃ for 4-6 h to obtain modified nano-silicon carbide. B. Add POE to a twin-screw extruder, melt and plasticize it, then add maleic anhydride and dicumyl peroxide through side feeding. The extrudate is then water-cooled and pelletized to obtain maleic anhydride-grafted polyolefin elastomer particles. C. Add maleic anhydride-grafted polyolefin elastomer particles, modified nano-silicon carbide, and zinc stearate to a high-speed mixer and mix at 1000 rpm for 4-6 minutes to initially disperse the modified nano-silicon carbide. Add the mixture to a twin-screw extruder, and after water cooling and pelletizing, vacuum dry at 60°C for 3-5 hours to obtain the toughening agent.

[0012] Preferably, the mass ratio of POE to maleic anhydride is 12-13:1, and dicumyl peroxide accounts for 0.4% to 0.8% of the mass of POE.

[0013] Preferably, the mass ratio of maleic anhydride-grafted polyolefin elastomer to modified nano-silicon carbide is 4:1, and zinc stearate accounts for 1.2% to 1.3% of the mass of maleic anhydride-grafted polyolefin elastomer.

[0014] A method for preparing a memory material pad for PCB drilling includes the following steps: S1. First, add ultra-high molecular weight polyethylene, EVA, and low-density polyethylene to the mixing tank and mix at low speed for 1-2 minutes. Add lubricant and mix well. Then, add nucleating agent and antioxidant in sequence and mix at high speed for 3-5 minutes. Finally, add modified hexagonal boron nitride and toughening additive in batches and mix at high speed for 5-10 minutes until the materials are mixed evenly. S2. Add the uniformly mixed material into a twin-screw extruder, control the temperature of each section to 180~210℃ and the screw speed to 200~400rpm, melt extrusion, cool through a water tank, and then cut into uniformly sized particles by a pelletizer to obtain composite masterbatch; S3. Spread the composite masterbatch evenly in the preheated mold. Heat the mold to 180-200℃ under a low pressure of 2-5MPa and hold the pressure for 3-5 minutes. Then gradually increase the pressure to 10-15MPa and hold the pressure for 15-25 minutes. Finally, cool the mold to below 50℃ at a rate of 5-15℃ / min, slowly release the pressure, and take out the formed pad plate.

[0015] The beneficial effects of this invention are: The memory material pad for PCB drilling in this invention is made of a blend of ultra-high molecular weight polyethylene, EVA, and low-density polyethylene to achieve high toughness and rapid melt recovery characteristics. At the same time, modified hexagonal boron nitride and toughening additives are added for synergistic modification. Through the construction of a thermally conductive network and interface toughening enhancement, good thermal conductivity, suitable rigidity and toughness, and excellent burr suppression effect are achieved.

[0016] In this invention, ultra-high molecular weight polyethylene (UHMWPE) serves as the framework and primary memory material of the system. Its ultra-long molecular chains and extremely high entanglement provide excellent wear resistance, toughness, and impact resistance. It partially melts when heated and rapidly recovers its strength through recrystallization after cooling, which is the core of the memory effect. As a toughening and tackifying phase, the introduction of EVA lowers the overall melting temperature and melt viscosity, allowing the material to soften more quickly and encapsulate the drill bit during drilling. Its vinyl acetate segments provide the necessary viscosity for effectively adhering drill cuttings. Low-density polyethylene (LDPE) serves as a flow modifier and compatibilizer. Its branched structure helps improve the processing flowability of UHMWPE and helps it to better compatibility with EVA, forming a uniform island structure and preventing phase separation.

[0017] This invention uses hexagonal boron nitride as a heat-conducting core, and forms a buffer shell by in-situ polymerization and coating its surface with a hydroxyl-terminated polybutadiene elastic layer. Then, a graphene oxide sheet is anchored to the surface of the elastic shell using a silane coupling agent, constructing a three-dimensional core-shell structure to achieve a synergistic improvement in thermal conductivity and mechanical properties. The sheet-like structure of hexagonal boron nitride and graphene form a three-dimensional heat-conducting network combining point and surface layers. The high thermal conductivity of hexagonal boron nitride is responsible for controlling the main heat channels, while the graphene sheets fill the thermally conductive gaps between the hexagonal boron nitride layers, thus improving the thermal conductivity of the composite material. The hydroxyl-terminated polybutadiene elastic shell can absorb impact stress during drilling, reducing material brittleness caused by stress concentration; simultaneously, its terminal hydroxyl groups can form hydrogen bonds with the matrix resin, improving the interfacial bonding between the filler and the polyethylene matrix, avoiding the toughness reduction problem caused by traditional rigid fillers. The surface graphene sheets can reduce interfacial friction between the filler and the resin melt, forming a synergistic lubrication effect with the lubricant in the formulation, solving the problem of reduced processing fluidity caused by high thermal conductivity fillers.

[0018] This invention employs a melt grafting method to graft maleic anhydride onto the POE elastomer backbone, followed by ultrasonic-assisted dispersion to in-situ embed nano-silicon carbide into the inter-chain gaps of the grafted elastomer, forming an organic-inorganic hybrid structure. This achieves simultaneous improvement in toughness and rigidity. The maleic anhydride graft groups can undergo transesterification with the vinyl acetate groups in EVA, enabling the hybrid agent to chemically bond with the matrix resin, thus enhancing interfacial bonding strength and significantly strengthening the material's rigidity. The POE elastomer phase forms a micro-dispersion structure in the matrix, which can absorb impact energy through mechanisms such as crazing and shear band formation, thereby improving the material's notched impact strength. The nano-silicon carbide particles can further inhibit crack propagation, creating a synergistic effect of elastomer toughening and rigid particle crack arrest. The thermal conductivity of the nano-silicon carbide complements the thermal conductivity network of the modified hexagonal boron nitride, refining the heat conduction path, improving the material's thermal uniformity, and preventing pad deformation caused by localized overheating during drilling.

[0019] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1 A modified hexagonal boron nitride is prepared by in-situ polymerization of a hydroxyl-terminated polybutadiene elastic layer onto the surface of hexagonal boron nitride, followed by grafting graphene oxide onto the surface using a silane coupling agent. The preparation method includes the following steps: (1) Add 100g of hexagonal boron nitride to 500mL of deionized water and ultrasonically disperse for 30min to form a suspension. Add 10g of concentrated nitric acid, heat to 80℃ and stir for 4h. After the reaction is complete, wash with deionized water by centrifugation until the pH is neutral, and vacuum dry at 60℃ for 12h to obtain hydroxylated hexagonal boron nitride. (2) 50g of hydroxylated hexagonal boron nitride was added to 300mL of anhydrous ethanol and ultrasonically dispersed for 20min. Then, 20g of hydroxyl-terminated polybutadiene and 0.5g of benzoyl peroxide were added. The mixture was heated to 70℃ under nitrogen protection and stirred for 3h. After the reaction was completed, the mixture was centrifuged, washed 3 times with anhydrous ethanol, and vacuum dried at 80℃ for 6h to obtain hydroxyl-terminated polybutadiene-coated hexagonal boron nitride. (3) 2g of graphene oxide was added to 1000mL of deionized water and ultrasonically exfoliated for 30min to obtain a graphene oxide dispersion. 5g of 3-glycidyl etheroxypropyltrimethoxysilane was added, and the pH was adjusted to 4-5 with dilute hydrochloric acid. The mixture was stirred at 60℃ for 2h, and then 60g of hexagonal boron nitride coated with hydroxyl-terminated polybutadiene was added. The mixture was heated to 80℃ and stirred for 4h. After the reaction, the mixture was centrifuged, washed with deionized water until neutral, and vacuum dried at 100℃ for 8h to obtain the modified hexagonal boron nitride.

[0022] Example 2 A toughening additive, comprising organic-inorganic hybrid particles formed by surface modification of nano-silicon carbide with a silane coupling agent and grafting maleic anhydride with POE, and the preparation method includes the following steps: A. Add 50g of nano-silicon carbide to 500mL of acetone, sonicate for 15min, add 3g of 3-(methacryloyloxy)propyltrimethoxysilane, reflux and stir at 60℃ for 3h, centrifuge, wash twice with acetone, and vacuum dry at 80℃ for 6h to obtain modified nano-silicon carbide. B. Add 100g of POE (POE) to a twin-screw extruder. After melting and plasticizing, add 8g of maleic anhydride and 0.6g of dicumyl peroxide through side feeding. The extrudate is then water-cooled and pelletized to obtain maleic anhydride-grafted polyolefin elastomer particles. C. Add 80g of maleic anhydride-grafted polyolefin elastomer particles, 20g of modified nano-silicon carbide, and 1g of zinc stearate to a high-speed mixer and mix at 1000rpm for 5min to initially disperse the modified nano-silicon carbide. Add the mixture to a twin-screw extruder, and after water cooling and pelletizing, vacuum dry at 60℃ for 4h to obtain the toughening agent.

[0023] Example 3 A memory material pad for PCB drilling comprises the following raw materials in parts by weight: 40 parts ultra-high molecular weight polyethylene, 30 parts EVA, 10 parts low-density polyethylene, 3 parts modified hexagonal boron nitride, 3 parts toughening additive, 5 parts nucleating agent, 0.5 parts lubricant, and 0.3 parts antioxidant; the modified hexagonal boron nitride is prepared in Example 1, and the toughening additive is prepared in Example 2; the nucleating agent is a compound of di(3,4-dimethylbenzyl)sorbitol and talc in a mass ratio of 1:9; the lubricant is a compound of zinc stearate and silicone masterbatch in a mass ratio of 2:1; and the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0024] The above-mentioned method for preparing the memory material pad for PCB drilling includes the following steps: S1. First, add ultra-high molecular weight polyethylene, EVA, and low-density polyethylene to the mixing tank and mix at low speed for 1 minute. Add lubricant and mix well. Then, add nucleating agent and antioxidant in sequence and mix at high speed for 5 minutes. Finally, add modified hexagonal boron nitride and toughening additive in batches and mix at high speed for 5 minutes until the materials are mixed evenly. S2. Add the uniformly mixed material into a twin-screw extruder, control the temperature of each section to 180~210℃, the screw speed to 200rpm, melt extrusion, cool through a water tank, and then cut into uniformly sized particles by a pelletizer to obtain composite masterbatch; S3. Spread the composite masterbatch evenly in the preheated mold. Heat the mold to 180°C under a low pressure of 5MPa and hold the pressure for 5 minutes. Then gradually increase the pressure to 10MPa and hold the pressure for 25 minutes. Finally, cool the mold to below 50°C at a rate of 5°C / min, slowly release the pressure, and take out the formed pad plate.

[0025] Example 4 A memory material pad for PCB drilling comprises the following raw materials in parts by weight: 50 parts ultra-high molecular weight polyethylene, 20 parts EVA, 15 parts low-density polyethylene, 2 parts modified hexagonal boron nitride, 4 parts toughening additive, 3 parts nucleating agent, 1.5 parts lubricant, and 0.1 parts antioxidant; the modified hexagonal boron nitride is prepared in Example 1, and the toughening additive is prepared in Example 2; the nucleating agent is a compound of di(3,4-dimethylbenzyl)sorbitol and talc in a mass ratio of 1:9; the lubricant is a compound of zinc stearate and silicone masterbatch in a mass ratio of 2:1; and the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0026] The above-mentioned method for preparing the memory material pad for PCB drilling includes the following steps: S1. First, add ultra-high molecular weight polyethylene, EVA, and low-density polyethylene to the mixing tank and mix at low speed for 2 minutes. Add lubricant and mix well. Then, add nucleating agent and antioxidant in sequence and mix at high speed for 3 minutes. Finally, add modified hexagonal boron nitride and toughening additive in batches and mix at high speed for 10 minutes until the materials are mixed evenly. S2. Add the uniformly mixed material into a twin-screw extruder, control the temperature of each section to 180~210℃, the screw speed to 400rpm, melt extrusion, cool through a water tank, and then cut into uniformly sized particles by a pelletizer to obtain composite masterbatch; S3. Spread the composite masterbatch evenly in the preheated mold. Heat the mold to 200°C under a low pressure of 2MPa and hold the pressure for 3 minutes. Then gradually increase the pressure to 15MPa and hold the pressure for 15 minutes. Finally, cool the mold to below 50°C at a rate of 15°C / min, slowly release the pressure, and take out the formed pad plate.

[0027] Example 5 A memory material pad for PCB drilling comprises the following raw materials in parts by weight: 45 parts ultra-high molecular weight polyethylene, 25 parts EVA, 12 parts low-density polyethylene, 2.5 parts modified hexagonal boron nitride, 3.5 parts toughening additive, 4 parts nucleating agent, 1 part lubricant, and 0.2 parts antioxidant; the modified hexagonal boron nitride was prepared in Example 1, and the toughening additive was prepared in Example 2; the nucleating agent is a compound of di(3,4-dimethylbenzyl)sorbitol and talc in a mass ratio of 1:9; the lubricant is a compound of zinc stearate and silicone masterbatch in a mass ratio of 2:1; and the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0028] The above-mentioned method for preparing the memory material pad for PCB drilling includes the following steps: S1. First, add ultra-high molecular weight polyethylene, EVA, and low density polyethylene to the mixing tank and mix at low speed for 1.5 minutes. Add lubricant and mix well. Then, add nucleating agent and antioxidant in sequence and mix at high speed for 4 minutes. Finally, add modified hexagonal boron nitride and toughening additive in batches and mix at high speed for 8 minutes until the materials are mixed evenly. S2. Add the uniformly mixed material into a twin-screw extruder, control the temperature of each section to 180~210℃, the screw speed to 300rpm, melt extrusion, cool through a water tank, and then cut into uniformly sized particles by a pelletizer to obtain composite masterbatch; S3. Spread the composite masterbatch evenly in the preheated mold. Heat the mold to 195°C under a low pressure of 3MPa and hold the pressure for 4 minutes. Then gradually increase the pressure to 13MPa and hold the pressure for 20 minutes. Finally, cool the mold to below 50°C at a rate of 10°C / min, slowly release the pressure, and take out the formed pad plate.

[0029] Comparative Example 1 A memory material pad for PCB drilling comprises the following raw materials in parts by weight: 45 parts ultra-high molecular weight polyethylene, 25 parts EVA, 12 parts low-density polyethylene, 3.5 parts toughening additive, 4 parts nucleating agent, 1 part lubricant, and 0.2 parts antioxidant; the toughening additive is prepared in Example 2; the nucleating agent is a compound of di(3,4-dimethylbenzyl)sorbitol and talc in a mass ratio of 1:9; the lubricant is a compound of zinc stearate and silicone masterbatch in a mass ratio of 2:1; and the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0030] The preparation method of the memory material pad for PCB drilling is the same as in Example 5, except that modified hexagonal boron nitride is not added in the mixing step S1.

[0031] Comparative Example 2 A memory material pad for PCB drilling comprises the following raw materials in parts by weight: 45 parts ultra-high molecular weight polyethylene, 25 parts EVA, 12 parts low-density polyethylene, 2.5 parts modified hexagonal boron nitride, 4 parts nucleating agent, 1 part lubricant, and 0.2 parts antioxidant; the modified hexagonal boron nitride is prepared in Example 1; the nucleating agent is a compound of di(3,4-dimethylbenzyl)sorbitol and talc in a mass ratio of 1:9; the lubricant is a compound of zinc stearate and silicone masterbatch in a mass ratio of 2:1; and the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0032] The preparation method of the memory material pad for PCB drilling is the same as in Example 5, except that no toughening additive is added in the mixing step S1.

[0033] Performance testing The memory material pads for PCB drilling prepared in Example 5, Comparative Example 1, and Comparative Example 2 were subjected to the following performance tests: (1) Thermal conductivity test: The thermal conductivity of the pad was tested according to the ASTM D5470-17 standard. The thermal conductivity meter was used. The pad was processed into a sample of 50mm×50mm×3mm. The sample was placed horizontally on the instrument test table. The hot wire probe was vertically attached to the center of the sample surface. The initial test temperature was 23℃, the heating power was 0.5W, and the test time was 60s. Heat was generated after the hot wire was energized. The thermal diffusivity was calculated by recording the curve of the hot wire temperature change over time. The thermal conductivity was calculated by combining the sample density and specific heat capacity. Each sample was tested 3 times and the average value was taken. (2) Mechanical property test: According to GB / T9341-2008 standard, the bending strength and bending modulus of the pad were tested. A universal testing machine was used to process the pad into 80mm×10mm×3mm samples. The samples were placed horizontally on two supports. The loading head was aligned with the center of the sample. The testing machine was started and the loading head descended at a uniform speed of 2mm / min. The load-displacement curve was recorded until the sample broke or the deformation reached 10% of the span. The bending strength and bending modulus were calculated. Five samples were tested in each group, and the average value was taken. According to GB / T1043.1-2008 standard, the notched impact strength of the pad was tested. A simple beam impact testing machine was used to process the pad into 80mm×10mm×3mm samples. A notched sample preparation machine was used to process a V-shaped notch in the middle of the sample. The sample notch was placed on the testing machine support with the pendulum impact direction facing the pendulum. The pendulum was released and impacted at the notch of the sample. The sample was recorded as to whether it broke and the energy consumed. The notched impact strength was calculated. Five samples were tested in each group, and the average value was taken. (3) Drilling performance test: PCB CNC drilling machine was used for testing. The pad was processed into a sample of 100mm×100mm×3mm. The initial mass of the pad was weighed with an electronic balance. A 1.6mm thick FR-4 copper-clad board was placed on top of the pad to simulate a PCB board. The pad and the FR-4 board were stacked and fixed on the drilling machine table. The drilling parameters were set as follows: rotation speed 30000rpm, feed speed 50mm / min, drilling depth 2.0mm. 25 holes were drilled in a 5×5 matrix (a total of 500 holes, completed in 20 times). After each drilling, the surface debris of the pad was cleaned. After drilling, the pad was cleaned with alcohol, dried, and weighed to calculate the wear amount. The FR-4 board after drilling was removed. The edge burrs of each hole were observed with an optical microscope. The protrusion height of the hole wall edge > 50μm was considered a hole with burrs. The number of holes with burrs was counted and the burr rate was calculated.

[0034] The obtained data is shown in Table 1 below.

[0035] Table 1 Performance test results of memory material pads used for PCB drilling

[0036] As can be seen from the data in Table 1, the thermal conductivity of Example 5 is 4 times that of Comparative Example 1, indicating that the modified hexagonal boron nitride is the core of constructing a high-efficiency thermal conductive network, and the thermal conductive path formed by hexagonal boron nitride and graphene can significantly reduce thermal resistance. The thermal conductivity of Comparative Example 2 is close to that of Example 5, indicating that the toughening additive has a small direct contribution to thermal conductivity, and mainly assists in the stability of the thermal conductive network through interfacial compatibility.

[0037] Example 5 showed a significant improvement in both flexural strength and modulus compared to Comparative Example 2, indicating that the toughening additive, through chemical interfacial bonding (reaction of maleic anhydride with EVA) and reinforcement by nano-silicon carbide, is key to improving rigidity. Comparative Example 1 showed a decrease in rigidity due to the lack of rigid support from hexagonal boron nitride. Example 5 also exhibited higher impact strength than Comparative Example 2, demonstrating that the POE elastomer phase of the toughening additive effectively absorbs impact energy. Comparative Example 1 showed slightly lower impact strength due to localized stress concentration caused by the absence of the hydroxyl-terminated polybutadiene buffer layer.

[0038] The burr rate in Example 5 was much lower than that in Comparative Example 1 because the high thermal conductivity allowed for timely dissipation of drilling heat, preventing resin from melting and sticking together to form burrs. The burr rate in Comparative Example 2 was slightly higher because insufficient rigidity resulted in poor support of the pad during drilling, leading to localized deformation and slight burrs. Example 5 had the lowest wear because the lubricating effect of modified hexagonal boron nitride and the rigidity enhancement of the toughening additives synergistically improved wear resistance. Comparative Example 2 had the most severe wear because insufficient toughness made the material easily scraped and peeled off by the drill bit.

[0039] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0040] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A memory material pad for PCB drilling, characterized in that, The raw materials include the following weight parts: 40-50 parts of ultra-high molecular weight polyethylene, 20-30 parts of EVA, 10-15 parts of low-density polyethylene, 2-3 parts of modified hexagonal boron nitride, 3-4 parts of toughening additive, 3-5 parts of nucleating agent, 0.5-1.5 parts of lubricant, and 0.1-0.3 parts of antioxidant; The modified hexagonal boron nitride is obtained by in-situ polymerization to coat an end-hydroxyl polybutadiene elastic layer on the surface of hexagonal boron nitride and then grafting graphene oxide through a silane coupling agent; The toughening additive is an organic-inorganic hybrid particle formed by compounding nano silicon carbide modified by a silane coupling agent and POE elastomer grafted with maleic anhydride.

2. The memory material cushion plate for PCB drilling according to claim 1, wherein, The nucleating agent is a compound of di(3,4-dimethylbenzylidene)sorbitol and talc at a mass ratio of 1:

9.

3. The memory material cushion plate for PCB drilling according to claim 1, wherein, The lubricant is a compound of zinc stearate and silicone master particles at a mass ratio of 2:

1.

4. The memory material cushion plate for PCB drilling according to claim 1, wherein, The antioxidant is a compound of antioxidant 1010 and antioxidant 168 at a mass ratio of 1:

1.

5. The memory material cushion plate for PCB drilling according to claim 1, wherein, The preparation method of the modified hexagonal boron nitride comprises the following steps: (1) Hexagonal boron nitride is added to deionized water and ultrasonically dispersed for 20-40 min to form a suspension, concentrated nitric acid is added, the temperature is raised to 80℃, and stirring is performed for 3-5 h. After the reaction is completed, the product is washed with deionized water by centrifugation until the pH is neutral, and vacuum drying is performed at 60℃ for 10-12 h to obtain hydroxylated hexagonal boron nitride; (2) The hydroxylated hexagonal boron nitride is added to anhydrous ethanol and ultrasonically dispersed for 15-25 min, end-hydroxyl polybutadiene and dibenzoyl peroxide are added, the temperature is raised to 70℃ under nitrogen protection, and stirring is performed for 2-4 h. After the reaction is completed, centrifugal separation is performed, the product is washed with anhydrous ethanol for 3 times, and vacuum drying is performed at 80℃ for 4-6 h to obtain hexagonal boron nitride coated with end-hydroxyl polybutadiene; (3) Graphene oxide is added to deionized water and ultrasonically exfoliated for 20-30 min to obtain a graphene oxide dispersion, 3-glycidyloxypropyltrimethoxysilane is added, the pH is adjusted to 4-5 with dilute hydrochloric acid, stirring is performed at 60℃ for 1.5-2.5 h, hexagonal boron nitride coated with end-hydroxyl polybutadiene is added, the temperature is raised to 80℃, and stirring is performed for 3-5 h. After the reaction, centrifugal separation is performed, the product is washed with deionized water until the pH is neutral, and vacuum drying is performed at 100℃ for 8-10 h to obtain the modified hexagonal boron nitride.

6. The memory material cushion plate for PCB drilling according to claim 5, wherein, The mass ratio of the hydroxylated hexagonal boron nitride and the end-hydroxyl polybutadiene is 5:2, the mass fraction of dibenzoyl peroxide in the end-hydroxyl polybutadiene is 2.5%, and the mass ratio of the graphene oxide, 3-glycidyloxypropyltrimethoxysilane, and hexagonal boron nitride coated with end-hydroxyl polybutadiene is 1:2.5:

30.

7. The memory material cushion plate for PCB drilling according to claim 1, wherein, The preparation method of the toughening additive comprises the following steps: A. Nano silicon carbide is added to acetone and ultrasonically dispersed for 10-20 min, 3-(methacryloyloxy)propyltrimethoxysilane is added, stirring is performed at 60℃ for 2-4 h, centrifugal separation is performed, the product is washed with acetone for 2 times, and vacuum drying is performed at 80℃ for 4-6 h to obtain modified nano silicon carbide; B. POE is added to a twin-screw extruder, melted and plasticized, maleic anhydride and dicumyl peroxide are added through side feeding, the extrudate is water-cooled and pelletized to obtain maleic anhydride grafted polyolefin elastomer particles. C. Maleic anhydride grafted polyolefin elastomer particles, modified nanosilicon carbide, zinc stearate are added into a high-speed mixer, mixed at 1000 rpm for 4-6 min to preliminarily disperse the modified nanosilicon carbide, and the mixture is added into a twin-screw extruder, the extrudate is cooled by water and then granulated, and the granules are vacuum dried at 60°C for 3-5 h to obtain the toughening agent.

8. The memory material cushion plate for PCB drilling according to claim 7, wherein, The mass ratio of the POE and the maleic anhydride is 12-13:1, and the dicumyl peroxide accounts for 0.4%-0.8% of the mass of the POE.

9. The memory material cushion plate for PCB drilling according to claim 7, wherein, The mass ratio of the maleic anhydride grafted polyolefin elastomer and the modified nanosilicon carbide is 4:1, and the zinc stearate accounts for 1.2%-1.3% of the mass of the maleic anhydride grafted polyolefin elastomer.

10. A method of manufacturing a memory material pad for PCB drilling according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: S1. First, the ultrahigh molecular weight polyethylene, EVA, and low-density polyethylene are added into a mixing tank, mixed at low speed for 1-2 min, and then a lubricant is added and mixed uniformly, and then a nucleating agent and an antioxidant are added in sequence and mixed at high speed for 3-5 min, and finally the modified hexagonal boron nitride and the toughening additive are added in batches and mixed at high speed for 5-10 min until the materials are uniformly mixed; S2. The uniformly mixed materials are added into a twin-screw extruder, the temperature of each section is controlled at 180-210°C, and the screw rotation speed is controlled at 200-400 rpm, and then the materials are melt-extruded, cooled by a water tank, and then cut into uniformly sized granules by a granulator to obtain the composite master batch; S3. The composite master batch is uniformly spread in a preheated mold, the mold is heated to 180-200°C under a low pressure of 2-5 MPa, and the pressure is maintained for 3-5 min, then the pressure is gradually increased to 10-15 MPa, and the pressure is maintained for 15-25 min, finally the mold is cooled to below 50°C at a rate of 5-15°C / min, the pressure is slowly released, and the formed mat plate is taken out.

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