Memory coating for PCB drilling cover base plate, PCB drilling cover base plate and preparation method of PCB drilling cover base plate

Abstract

The invention relates to the technical field of PCB drilling, in particular to a memory coating for a PCB drilling cover base plate, the PCB drilling cover base plate and a preparation method of the PCB drilling cover base plate. The memory coating comprises the following components in percentage by weight: 60-80% of thermosetting aliphatic isocyanate and 5-7% of NCO (isocyanate); 20-30% of polyethylene, the Mw of which is 100-120 kDa, and the crystallinity of which is 60-70%; 5% of nano TiO2; 1-2% of graphene; 1%-2% of a furan-maleimide system; 1%-1.5% of a water-based dispersant BYK-190, and 0.1%-0.5% of a defoaming agent; 0.2%-0.3% of a flatting agent; 0.1%-0.2% of a wetting auxiliary agent; according to the drilling hole cover plate cleaning agent, the damage of a drilling hole cover plate to a drill point can be effectively reduced, and the service life of the drill point is prolonged.

Description

Technical Field

[0001] This invention relates to the field of PCB drilling technology, specifically to a memory coating for PCB drilling cover plates, the PCB drilling cover plate, and a method for preparing the same. Background Technology

[0002] As the global printed circuit board (PCB) industry rapidly evolves towards high-density interconnect (HDI) and micro-via (≤0.05mm) processes, micro-via processing has placed new demands on the overall performance of drill cover plates: the cumulative error of stacked drilling needs to be controlled within ±10μm, and the 0.05mm micro drill needs to maintain the integrity of the cutting edge within a lifespan of ≥8000 holes to prevent warping and hole drift caused by local temperature rise.

[0003] However, the mainstream aluminum sheet cover plates and traditional phenolic / epoxy fiberboard cover plates currently used in the industry have obvious defects:

[0004] Aluminum sheets have high rigidity but poor resilience, and after repeated impacts, they will undergo permanent deformation, resulting in a positioning error of >20μm; fiberboard has low hardness and high wear, and the drill bit edge becomes dull quickly, with an actual lifespan of <5000 holes.

[0005] The existing cover plate has low thermal conductivity, and the drilling temperature rise is >150℃, which further aggravates board warping and hole drift. This has limited the large-scale manufacturing of high-end HDI boards, IC carrier boards and next-generation packaging substrates. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a memory coating for PCB drilling cover pads. A memory coating for PCB drilling cover pads, PCB drilling cover pads and their preparation methods are described, which can effectively reduce the damage of the drilling cover to the drill bit and improve the service life of the drill bit.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A memory coating is provided for use in PCB drill hole cover plates, the memory coating comprising the following components by weight percentage:

[0009] Thermosetting aliphatic isocyanates account for 60-80%, and their NCO content is 5-7%.

[0010] Polyethylene 20-30%, with Mw of 100-120 kDa and crystallinity of 60-70%;

[0011] Nano TiO2 4-5%

[0012] Graphene 1-2%

[0013] furan-maleimide system 1-2%

[0014] Aqueous dispersant BYK-1901 ~ 1.5%

[0015] Defoamer 0.1-0.5%

[0016] Leveling agent 0.2-0.3%

[0017] Wetting agent 0.1-0.2%

[0018] Replenish with deionized water to 100%.

[0019] The functions of the above components:

[0020] Thermosetting aliphatic isocyanates, as the hard segments and crosslinking sites of the PU backbone, can chemically crosslink with polyols, water, and reversible furan-maleimide bonds. After curing, they provide a stationary phase with high glass transition temperature (Tg≈80℃) and shape memory. The resulting aliphatic structure ensures weather resistance and low yellowing.

[0021] Polyethylene with a molecular weight of 100–120 kDa and a crystallinity of 60–70% is used to control reversible crystallization. It melts and softens upon heating, allowing deformation; upon cooling, it recrystallizes, providing recovery force and enabling shape memory cycling. High crystallinity ensures high recovery rate and low permanent deformation.

[0022] Nano-TiO2 improves surface hardness, provides UV shielding, enhances weather resistance, and its high refractive index provides contrast for visual inspection of micropores. As a heterogeneous nucleation point, it refines PE grains and improves dimensional stability.

[0023] Graphene can quickly dissipate drilling heat; it is mechanically reinforced, improving the coating's wear resistance and scratch resistance; its two-dimensional sheet structure provides synergistic lubrication, reducing the coefficient of friction; and it forms a conductive network, facilitating the dissipation of static electricity.

[0024] The furan-maleimide system introduces reversible Diels-Alder bonds. These bonds break at temperatures above 90–110°C, softening the coating and self-healing microcracks. Upon cooling, the coating re-crosslinks, restoring mechanical properties and improving drill bit life. The aqueous dispersant BYK-190 is an anionic polymeric dispersant that adsorbs onto the surfaces of TiO2 and graphene, providing electrostatic and steric stabilization to ensure that a 2wt% solids slurry does not settle or agglomerate within 30 days.

[0025] Defoamers break down foam films, eliminate air bubbles generated during stirring and coating processes, prevent pinholes and craters, and improve surface smoothness. These defoamers can be silicone emulsions, etc.

[0026] Leveling agents reduce dynamic surface tension, promote rapid coating spread, eliminate brush marks and orange peel, and achieve a mirror-like finish. These leveling agents can be polyether-modified silicones, etc.

[0027] Wetting aid: Improves wetting of HDPE / graphite substrates, enhances adhesion, and prevents edge shrinkage and wrinkling. This wetting aid can be anionic polyether, etc.

[0028] Deionized water, as a continuous phase, provides the advantages of environmental protection and low VOC in water-based systems, and can adjust the solid content and application viscosity to meet the requirements of slot coating or spraying processes.

[0029] This embodiment includes the following steps:

[0030] Step 1: Disperse graphene in deionized water and homogenize it under a pressure of 60MPa to 80MPa to obtain a 1 to 3 wt% graphene mother liquor.

[0031] Step 2: Place the nano-TiO2 in an ethanol solution containing γ-methacryloxypropyltrimethoxysilane for 1-2 hours, and then dry it at 100-110℃ to obtain a nano-TiO2 dispersion.

[0032] Thermosetting aliphatic isocyanate is prepolymerized at 60-70°C for 1-2 hours, then polyethylene is added and blended, and reacted at 120-140°C for 20-40 minutes to obtain the prepolymer.

[0033] Add graphene mother liquor and TiO2 dispersion to the prepolymer, and stir at 600-700 rpm for 20-30 min until the viscosity of the resulting mixture is 500-600 cP.

[0034] The advantages of this preparation method are: graphene sheets and TiO2 particles are uniformly dispersed and physically entangled during high-speed shearing, forming a sheet-particle interpenetrating network, which increases the thermal conductivity by more than 30%, rapidly dissipates drilling heat, and reduces the temperature rise around the hole by 25-30℃, effectively suppressing plate warping and hole drift. Graphene provides a two-dimensional framework, and TiO2 provides rigid microspheres. Together with the PU-PE hard segments, the surface hardness of the coating increases from HV220 to ≥300, significantly improving scratch resistance during micro-hole drilling. The final viscosity of 500-600 cP meets the leveling requirements of slot coating or spraying, while avoiding sagging due to excessive thinness or clogging due to excessive thickness. The mild shearing of 600-700 rpm ensures the integrity of the filler structure without damaging the graphene sheet diameter or the silane layer on the TiO2 surface. The three functions of thermal conductivity, reinforcement, and wear resistance are introduced into the prepolymer system in one step, eliminating the need for subsequent secondary dispersion or high-temperature post-treatment, shortening the cycle time by 15% and reducing energy consumption by more than 10%.

[0035] In this embodiment, in step one, graphene is dispersed in deionized water using ultrasonic vibration at 400W to 500W. This ensures that the graphene is fully dispersed.

[0036] In this embodiment, the Zeta potential of the graphene mother liquor is ≤-40mV. A Zeta potential ≤-40mV can form a sufficiently thick electrostatic repulsion layer around the sheets, overcoming van der Waals forces, and ensuring that the graphene does not settle or agglomerate for 30 days at a high concentration of 2–3wt%, thus meeting the requirements of continuous coating processes.

[0037] In this embodiment, in step one, the resulting mixture is filtered through a 5μm filter element, which improves the fineness of the mixture.

[0038] A PCB drilling cover plate is also provided, comprising a substrate, the surface of which is coated with the memory coating as described in any one of claims 2 to 5.

[0039] In this embodiment, the substrate comprises a PET buffer layer, a first HDPE fiberboard, graphite paper, and a second HDPE fiberboard, which are sequentially stacked and connected.

[0040] The memory coating is applied to the PET buffer layer.

[0041] The functions of the aforementioned PCB drilling cover plate are as follows: PET and memory coating have similar polarities, with a peel strength ≥6N / cm, ensuring no delamination over long-term use. The memory coating, as the outermost layer, serves both as the adhesion substrate and absorbs the instantaneous impact of the drill bit, reducing the edge chipping rate at the hole opening by more than 40%. The high-density polyethylene fiberboard provides overall rigidity and dimensional support, ensuring a flatness of ≤0.05mm after hot pressing, meeting the requirements for continuous roll-to-roll processing. The graphite paper forms a longitudinal heat conduction channel, rapidly dissipating drilling heat laterally, reducing the temperature rise around the hole by 25-30℃, and suppressing hole position drift caused by thermal expansion and contraction.

[0042] A method for preparing a PCB drilling cover plate is also provided, including the following steps:

[0043] Step 1: Apply an epoxy resin film between the first HDPE fiberboard, graphite paper, and the second HDPE fiberboard. Press the fiberboard at 150-180°C with a pressure of 2-3 MPa for 4-5 minutes. Then, cold press the fiberboard at 15-20°C for shaping, apply a pressure of 1-2 MPa, and hold the pressure for 2-3 minutes to obtain a pre-formed substrate.

[0044] Step 2: Place the preformed substrate into the coating of the memory coating and leave it for 40-60 minutes. Then, drill holes in the PCB and cover it with a pad.

[0045] Under conditions of 150–180℃, 2–3MPa, and 4–5min, the epoxy resin film completely melts and penetrates into the micropores of the HDPE fiberboard and graphite paper, forming a peel strength of ≥30N / cm. Cold pressing at 15–20℃, 1–2MPa, and 2–3min rapidly sets the structure, eliminating internal stress and ensuring a substrate flatness of <0.05mm. Subsequent high-speed drilling does not result in edge bursting or delamination. The HDPE / graphite paper / HDPE sandwich structure achieves densification during hot pressing, with no voids in the graphite paper's thermal conductivity channels, increasing the overall λ to ≥150W·m. -1 • K-1: Drilling heat is dissipated laterally, reducing the temperature rise around the hole by 25-30℃ and suppressing hole displacement caused by thermal expansion and contraction. Immersion for 40-60 minutes allows the 25-50μm thick PU / PE-SMP memory coating to penetrate uniformly along the PET buffer layer and micropores, forming a "pinning" interface with a peel strength ≥6N / cm; simultaneously retaining the coating's thermal response lubrication, self-healing, and ±10μm high positioning accuracy functions.

[0046] The three-step process of hot pressing, cold pressing, and impregnation is integrated, eliminating the need for secondary coating or high-temperature post-curing. This reduces cycle time by 15% and energy consumption by 10%, meeting the requirements for continuous roll-to-roll production at a width of 600mm and a speed of 50m / min.

[0047] In this embodiment, a laser is used to etch microchannels on the surface of the PET buffer layer, and the coating of the memory coating adheres to the microchannels.

[0048] Laser etching 50μm-level microchannels on the surface of the PET buffer layer allows the memory coating to be mechanically anchored to the PET like a "dovetail groove," significantly improving adhesion (peel strength ≥20%). At the same time, the microchannels become a chip removal / heat conduction micronetwork, reducing drilling temperature rise and chip accumulation, further extending drill bit life and maintaining positioning accuracy of ±10μm.

[0049] In this embodiment, the width of the microchannel is 50 μm.

[0050] The beneficial effects of the memory coating for PCB drilling cover plates of the present invention are as follows:

[0051] In this invention, the shape memory coating is applied to the surface of the substrate. Because this coating contains thermosetting aliphatic isocyanate, polyethylene, nano-TiO2, and graphene, it effectively reduces friction, resulting in a ≥30% reduction in micro-drill wear and increasing the lifespan of a 0.05mm drill bit from 5000 holes to ≥8000 holes, directly reducing tool costs by over 37%. Furthermore, the shape memory recovery force eliminates plastic deformation around the hole, with a cumulative positioning error ≤±10μm after 50 cycles, meeting the ≥99% alignment yield requirement for HDI ultra-fine holes. In addition, the graphene / nano-TiO2 reinforced network increases surface hardness by 40%, thermal conductivity by 30%, and reduces drilling temperature rise by 25-30℃, suppressing board warping and hole drift. Moreover, this coating is an aqueous system with VOC ≤10mg / m³. 3 It complies with RoHS / REACH; it is 100% recyclable and meets the requirements of green manufacturing.

[0052] The beneficial effects of the PCB drilling cover pad of the present invention are as follows:

[0053] In this invention, the PCB drilling cover plate uses the aforementioned memory coating, which effectively improves the service life of the drill bit.

[0054] The beneficial effects of the method for preparing a PCB drilling cover plate of the present invention are as follows:

[0055] The method for preparing the PCB drilling cover plate in this invention can efficiently produce PCB drilling cover plates, is easy to operate, and is suitable for large-scale production and application. Detailed Implementation

[0056] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention have been shown, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0057] The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a” and “the” as used in this invention and the appended claims are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0058] It should be understood that although the terms "first," "second," "third," etc., may be used in this invention to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this invention, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0059] Example 1

[0060] This embodiment discloses a memory coating for a PCB drill hole cover plate, the memory coating comprising the following components by weight percentage: 70% thermosetting aliphatic isocyanate with 6% NCO; 20.5% polyethylene with a Mw of 110 kDa and a crystallinity of 65%; 4.5% nano-TiO2; 1.5% graphene; and 1.5% furan-maleimide system.

[0061] Water-based dispersant BYK-190 1.2%; defoamer 0.4%; leveling agent 0.25%; wetting agent 0.15%;

[0062] Replenish with deionized water to 100%.

[0063] In this embodiment, the method for preparing the memory coating for the PCB drilling cover plate includes the following steps:

[0064] Graphene was dispersed in deionized water and uniformly dispersed under a pressure of 70 MPa to obtain a 2 wt% graphene mother liquor.

[0065] Nano-TiO2 was placed in an ethanol solution containing γ-methacryloxypropyltrimethoxysilane for 1–2 h, and then dried at 105 °C to obtain a nano-TiO2 dispersion.

[0066] Thermosetting aliphatic isocyanate was prepolymerized at 65°C for 1.5 h, then added to polyethylene for blending, and reacted at 135°C for 30 min to obtain the prepolymer.

[0067] Graphene mother liquor and TiO2 dispersion were added to the prepolymer and stirred at 600-700 rpm for 25 min until the viscosity of the resulting mixture was 550 cP, thus obtaining a memory coating.

[0068] In this embodiment, graphene dispersed in deionized water is first dispersed using ultrasonic vibration at 400W to 500W.

[0069] In this embodiment, the Zeta potential of the graphene mother liquor is ≤-40mV.

[0070] In this embodiment, the resulting mixture is filtered through a 5μm filter element.

[0071] This embodiment also discloses a PCB drilling cover plate, which includes a substrate, the surface of which is coated with the aforementioned memory coating.

[0072] In this embodiment, the substrate comprises a PET buffer layer, a first HDPE fiberboard, graphite paper, and a second HDPE fiberboard, which are sequentially stacked and connected.

[0073] The memory coating is applied to the PET buffer layer.

[0074] The method for preparing the above-mentioned PCB drilling cover plate includes the following steps:

[0075] Step 1: Apply epoxy resin film to the connection points between the first HDPE fiberboard and the graphite paper, and between the graphite paper and the second HDPE fiberboard. Press the film at 170°C with a pressure of 2.5MPa for 4 minutes, then cold press at 16°C for shaping, apply 1MPa and hold for 2 minutes to obtain the pre-formed substrate.

[0076] Step 2: Place the preformed substrate into the coating of the memory coating, leave it for 40-60 minutes, and then allow it to cure naturally to obtain the PCB drilling cover plate.

[0077] In this embodiment, a laser is used to etch microchannels on the surface of the PET buffer layer, and the coating of the memory coating adheres to the microchannels.

[0078] In this embodiment, the width of the microchannel is 50 μm.

[0079] The results obtained in this embodiment are shown in Table 1:

[0080] Table 1

[0081]

[0082]

[0083] Example 2

[0084] This embodiment discloses a memory coating for a PCB drill hole cover plate, the memory coating comprising the following components by weight percentage: 60% thermosetting aliphatic isocyanate with 5% NCO; 20% polyethylene with 100kDa Mw and 60% crystallinity; 4% nano-TiO2; 1% graphene; and 1% furan-maleimide system.

[0085] Water-based dispersant BYK-190 1%; defoamer 0.1%; leveling agent 0.2%; wetting agent 0.1%;

[0086] Replenish with deionized water to 100%.

[0087] In this embodiment, the method for preparing the memory coating for the PCB drilling cover plate includes the following steps:

[0088] Graphene was dispersed in deionized water and uniformly dispersed under a pressure of 60 MPa to 80 MPa to obtain a 1 to 3 wt% graphene mother liquor.

[0089] Nano-TiO2 was placed in an ethanol solution containing γ-methacryloxypropyltrimethoxysilane for 1–2 h, and then dried at 100 °C–110 °C to obtain a nano-TiO2 dispersion.

[0090] Thermosetting aliphatic isocyanate was prepolymerized at 60°C for 1 hour, then polyethylene was added and blended, and the mixture was reacted at 120°C for 20 minutes to obtain the prepolymer.

[0091] Graphene mother liquor and TiO2 dispersion were added to the prepolymer and stirred at 600 rpm for 20 min until the viscosity of the resulting mixture was 500 cP, thus obtaining a memory coating.

[0092] In this embodiment, graphene dispersed in deionized water is first dispersed using ultrasonic vibration at 400W to 500W.

[0093] In this embodiment, the Zeta potential of the graphene mother liquor is ≤-40mV.

[0094] In this embodiment, the resulting mixture is filtered through a 5μm filter element.

[0095] This embodiment also discloses a PCB drilling cover plate, which includes a substrate, the surface of which is coated with the aforementioned memory coating.

[0096] In this embodiment, the substrate comprises a PET buffer layer, a first HDPE fiberboard, graphite paper, and a second HDPE fiberboard, which are sequentially stacked and connected.

[0097] The memory coating is applied to the PET buffer layer.

[0098] The method for preparing the above-mentioned PCB drilling cover plate includes the following steps:

[0099] Step 1: Apply epoxy resin film to the connection points between the first HDPE fiberboard and the graphite paper, and between the graphite paper and the second HDPE fiberboard. Press the film at a temperature of 150-180℃ with a pressure of 2-3MPa for 4-5 minutes. Then, cold press the film at 16℃ for shaping, apply a pressure of 1MPa, and hold the pressure for 2 minutes to obtain a pre-formed substrate.

[0100] Step 2: Place the preformed substrate into the coating of the memory coating, leave it for 40-60 minutes, and then allow it to cure naturally to obtain the PCB drilling cover plate.

[0101] In this embodiment, a laser is used to etch microchannels on the surface of the PET buffer layer, and the coating of the memory coating adheres to the microchannels.

[0102] In this embodiment, the width of the microchannel is 50 μm.

[0103] The results shown in Table 2 are as follows:

[0104] Table 2

[0105] Test Project Target value Memory recovery rate (180° bend) ≥90% (recovery rate at 25℃ for 24 hours) Drill hole wear rate (FR4 board) ≤0.05mm / 1000 holes Surface resistance <![CDATA[10 6 -10 9 Ω / sq (Antistatic range) Dynamic bond reversibility Tanδ peak can be reversibly varied by ±10% (DMA)

[0106] Example 3

[0107] This embodiment discloses a memory coating for a PCB drill hole cover plate, the memory coating comprising the following components by weight percentage: 75% thermosetting aliphatic isocyanate with 7% NCO; 15% polyethylene with a Mw of 120 kDa and a crystallinity of 70%; 25% nano-TiO; 2% graphene; 2% furan-maleimide system; 1.5% aqueous dispersant BYK-190; 0.5% defoamer; 0.3% leveling agent; 0.2% wetting agent; and deionized water to make up to 100%.

[0108] In this embodiment, the method for preparing the memory coating for the PCB drilling cover plate includes the following steps:

[0109] Graphene was dispersed in deionized water and uniformly dispersed under a pressure of 80 MPa to prepare a 1-3 wt% graphene mother liquor.

[0110] Nano-TiO2 was placed in an ethanol solution containing γ-methacryloxypropyltrimethoxysilane for 2 hours, and then dried at 110 °C to obtain a nano-TiO2 dispersion.

[0111] Thermosetting aliphatic isocyanate was prepolymerized at 70°C for 2 hours, then blended with polyethylene and reacted at 140°C for 40 minutes to obtain the prepolymer.

[0112] Graphene mother liquor and TiO2 dispersion were added to the prepolymer and stirred at 700 rpm for 30 min until the viscosity of the resulting mixture was 600 cP, thus obtaining a memory coating.

[0113] In this embodiment, graphene is dispersed in deionized water using 500W ultrasonic vibration.

[0114] In this embodiment, the Zeta potential of the graphene mother liquor is ≤-40mV.

[0115] In this embodiment, the resulting mixture is filtered through a 5μm filter element.

[0116] This embodiment also discloses a PCB drilling cover plate, which includes a substrate, the surface of which is coated with the aforementioned memory coating.

[0117] In this embodiment, the substrate comprises a PET buffer layer, a first HDPE fiberboard, graphite paper, and a second HDPE fiberboard, which are sequentially stacked and connected.

[0118] The memory coating is applied to the PET buffer layer.

[0119] The method for preparing the above-mentioned PCB drilling cover plate includes the following steps:

[0120] Step 1: Apply epoxy resin film to the connection points between the first HDPE fiberboard and the graphite paper, and between the graphite paper and the second HDPE fiberboard. Press the film at 180°C with a pressure of 3MPa for 5 minutes, then cold press at 20°C for shaping, apply a pressure of 2MPa, and hold the pressure for 3 minutes to obtain a pre-formed substrate.

[0121] Step 2: Place the preformed substrate into the coating of the memory coating, leave it for 60 minutes, and then allow it to cure naturally to obtain the PCB drilling cover plate.

[0122] In this embodiment, a laser is used to etch microchannels on the surface of the PET buffer layer, and the coating of the memory coating adheres to the microchannels.

[0123] In this embodiment, the width of the microchannel is 50 μm.

[0124] The results shown in Table 3 are as follows:

[0125] Table 3

[0126] parameter This embodiment Drilling life (0.3mm drill bit) 5000 holes Hole position accuracy (Cpk) 1.67 Coating wear rate (μm / 1000 pores) 0.03 Burr height (μm) ≤15

[0127] Example 4

[0128] This embodiment discloses a memory coating for a PCB drill hole cover plate, the memory coating comprising the following components by weight percentage: 40% thermosetting aliphatic isocyanate with 60% NCO; 15% polyethylene with 120 kDa Mw and 45% crystallinity; 25% nano-TiO; 2% graphene; 2% furan-maleimide system; 1.5% aqueous dispersant BYK-190; 0.5% defoamer; 0.3% leveling agent; 0.2% wetting agent; and deionized water to make up to 100%.

[0129] In this embodiment, the method for preparing the memory coating for the PCB drilling cover plate includes the following steps:

[0130] Graphene was dispersed in deionized water and uniformly dispersed under a pressure of 80 MPa to prepare a 1-3 wt% graphene mother liquor.

[0131] Nano-TiO2 was placed in an ethanol solution containing γ-methacryloxypropyltrimethoxysilane for 2 hours, and then dried at 110 °C to obtain a nano-TiO2 dispersion.

[0132] Thermosetting aliphatic isocyanate was prepolymerized at 70°C for 2 hours, then blended with polyethylene and reacted at 140°C for 40 minutes to obtain the prepolymer.

[0133] Graphene mother liquor and TiO2 dispersion were added to the prepolymer and stirred at 700 rpm for 30 min until the viscosity of the resulting mixture was 600 cP, thus obtaining a memory coating.

[0134] In this embodiment, graphene is dispersed in deionized water using 500W ultrasonic vibration.

[0135] In this embodiment, the Zeta potential of the graphene mother liquor is ≤-40mV.

[0136] In this embodiment, the resulting mixture is filtered through a 5μm filter element.

[0137] This embodiment also discloses a PCB drilling cover plate, which includes a substrate, the surface of which is coated with the aforementioned memory coating.

[0138] In this embodiment, the substrate comprises a PET buffer layer, a first HDPE fiberboard, graphite paper, and a second HDPE fiberboard, which are sequentially stacked and connected.

[0139] The memory coating is applied to the PET buffer layer.

[0140] The method for preparing the above-mentioned PCB drilling cover plate includes the following steps:

[0141] Step 1: Apply epoxy resin film to the connection points between the first HDPE fiberboard and the graphite paper, and between the graphite paper and the second HDPE fiberboard. Press the film at 185°C with a pressure of 2MPa for 5 minutes, then cold press at 20°C for shaping, apply pressure of 2MPa, and hold for 3 minutes to obtain a pre-formed substrate.

[0142] Step 2: Place the preformed substrate into the coating of the memory coating, leave it for 60 minutes, and then allow it to cure naturally to obtain the PCB drilling cover plate.

[0143] In this embodiment, a laser is used to etch microchannels on the surface of the PET buffer layer, and the coating of the memory coating adheres to the microchannels.

[0144] In this embodiment, the width of the microchannel is 50 μm.

[0145] The results shown in Table 4 are as follows:

[0146] Table 4

[0147] parameter This embodiment Memory recovery rate (25℃) 92％ Drilling life (0.3mm drill bit) 5000 holes Surface resistance <![CDATA[10 6 Ohm / sq]]> Coating brittleness (impact test) No cracks thermal conductivity 10W / m·K

[0148] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0149] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on orientation or positional relationship and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0150] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation described for the device. The exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0151] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this application.

[0152] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A memory coating for PCB drilling cover plates, characterized in that, The memory coating comprises the following components by weight percentage: Thermosetting aliphatic isocyanates account for 60-80%, and their NCO content is 5-7%. Polyethylene 20-30%, with Mw of 100-120 kDa and crystallinity of 60-70%; Nano TiO2 4-5% Graphene 1-2% furan-maleimide system 1-2% Aqueous dispersant BYK-190 1-1.5% Defoamer 0.1-0.5% Leveling agent 0.2-0.3% Wetting agent 0.1-0.2% Replenish with deionized water to 100%.

2. The method for preparing the memory coating for PCB drilling cover plate according to claim 1, characterized in that, Includes the following steps: Graphene was dispersed in deionized water and uniformly dispersed under a pressure of 60 MPa to 80 MPa to obtain a 1 to 3 wt% graphene mother liquor. Nano-TiO2 was placed in an ethanol solution containing γ-methacryloxypropyltrimethoxysilane for 1–2 h, and then dried at 100 °C–110 °C to obtain a nano-TiO2 dispersion. Thermosetting aliphatic isocyanate was prepolymerized at 60-70°C for 1-2 hours, then polyethylene was added and blended, and the mixture was reacted at 120-140°C for 20-40 minutes to obtain the prepolymer. Graphene mother liquor and TiO2 dispersion are added to the prepolymer and stirred at 600-700 rpm for 20-30 min until the viscosity of the resulting mixture is 500-600 cP, thus obtaining a memory coating.

3. The method for preparing the memory coating for PCB drilling cover plate according to claim 2, characterized in that, Graphene was dispersed in deionized water using ultrasonic vibration at 400W–500W.

4. The method for preparing the memory coating for a PCB drilling cover plate according to claim 2, characterized in that, The zeta potential of the graphene mother liquor is ≤-40mV.

5. The method for preparing a memory coating for a PCB drilling cover plate according to claim 2, characterized in that, The resulting mixture was filtered through a 5μm filter cartridge.

6. A PCB drilling cover plate, characterized in that, Includes a substrate, the surface of which is coated with the memory coating as described in any one of claims 2 to 5.

7. The PCB drilling cover plate according to claim 6, characterized in that, The substrate comprises a PET cushioning layer, a first HDPE fiberboard, graphite paper, and a second HDPE fiberboard, which are sequentially stacked together. The memory coating is applied to the PET buffer layer.

8. The method for preparing the PCB drill hole cover plate according to claim 6 or 7, characterized in that, Includes the following steps: Step 1: Apply epoxy resin film to the connection points between the first HDPE fiberboard and the graphite paper, and between the graphite paper and the second HDPE fiberboard. Press the film at a temperature of 150-180℃ with a pressure of 2-3MPa for 4-5 minutes. Then, cold press the film at 15-20℃ for shaping, apply a pressure of 1-2MPa, and hold the pressure for 2-3 minutes to obtain a pre-formed substrate. Step 2: Place the preformed substrate into the coating of the memory coating, leave it for 40-60 minutes, and then allow it to cure naturally to obtain the PCB drilling cover plate.

9. The method for preparing the PCB drilling cover plate according to claim 8, characterized in that, Microchannels are etched on the surface of a PET buffer layer using a laser, and the coating of the memory coating adheres to the microchannels.

10. The method for preparing the PCB drilling cover plate according to claim 9, characterized in that, The width of the microchannel is 50 μm.

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