High-thermal-conductivity insulating ink and preparation method thereof

Abstract

The invention relates to the technical field of novel ink, in particular to high-thermal-conductivity insulating ink and a preparation method thereof. The problem that the heat-conducting property and the insulating property of the ink cannot be well considered is solved. The ink is prepared by mixing and grinding modified low-viscosity epoxy resin serving as a binder, a surface modified functional mica main filler, a titanate modified spherical aluminum oxide auxiliary filler, hybrid microchips and auxiliaries. The rheological property of the ink is adjusted by introducing the hyperbranched polymer, and the problems of too high viscosity and poor thixotropy of the traditional heat-conducting ink under high solid content are solved by matching with the dense accumulation of the functional mica with the core-shell structure and the spherical filler; according to the preparation process, three-roller strong shear dispersion and vacuum defoaming are adopted, so that oriented arrangement of the filler in an ink layer is ensured; the prepared ink has excellent silk-screen printing adaptability, high breakdown voltage and low interface thermal resistance, and is suitable for efficient heat dissipation and insulation protection of electronic circuit boards.

Description

Technical Field

[0001] This invention relates to the field of novel ink technology, specifically to a high thermal conductivity insulating ink and its preparation method. Background Technology

[0002] With the rapid development of the electronics and information industry, screen printing inks, as key functional materials in the manufacturing of electronic components, face increasingly stringent performance requirements. In particular, the development of functional inks that combine high thermal conductivity and excellent electrical insulation, especially for the heat dissipation needs of high-power devices, has become a research hotspot in the industry. These inks typically consist of resin binders, curing agents, thermally conductive fillers, and additives. They are applied to the surface of a substrate via screen printing and, after curing, form a heat-dissipating and insulating coating.

[0003] However, in existing thermally conductive and insulating ink technologies, there is an irreconcilable contradiction between "high filler content" and "printability." To achieve ideal thermal conductivity, a large amount of inorganic thermally conductive filler is often added to the ink system. Extremely high solid content leads to a sharp increase in ink viscosity, making thixotropy difficult to control and significantly deteriorating flowability and leveling properties. In actual printing processes, this manifests as easy screen clogging, poor ink distribution, jagged edges on printed lines, and the cured ink layer is prone to pinholes or orange peel effects, severely impacting the insulation reliability and appearance quality of the coating.

[0004] In terms of filler selection, although metal powder inks have good thermal conductivity, they cannot provide insulation; single spherical ceramic powders (such as alumina) are prone to settling in the resin matrix, resulting in poor ink storage stability; while sheet-like fillers such as mica have excellent insulation and voltage resistance properties and barrier properties, ordinary mica powder has low thermal conductivity and an inert surface, making it difficult to form an effective phonon transport network in the resin; in addition, ordinary mica is prone to interlayer slippage or breakage during ink grinding and dispersion, leading to an abnormal increase in system viscosity.

[0005] Therefore, how to utilize modification techniques to prepare functional mica fillers that can both leverage the insulating advantages of their sheet-like structure and significantly improve the thermal conductivity of the cured film through synergistic effects with the resin matrix and other fillers, while ensuring the ink's low viscosity and ease of printing, is a pressing technical challenge in this field. To address this, a high thermal conductivity insulating ink and its preparation method are proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a high thermal conductivity insulating ink and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution: Unless otherwise specified, all parts in this invention are parts by weight.

[0008] This invention provides a method for preparing a high thermal conductivity insulating ink, the method being as follows: 25-35 parts of hyperbranched polyester-modified epoxy resin, 1.6 parts of dispersant BYK-111, and 0.8 parts of leveling agent BYK-333 are mixed and stirred at 400 rpm for 5 minutes. Then, 35-50 parts of functional mica filler, 30-45 parts of titanate-modified spherical alumina, 3-6 parts of hybrid microflakes, and 2-5 parts of latent curing agent are added sequentially, and the rotation speed is increased to 2000-3000 rpm. After stirring and dispersing for 40 minutes, a premixed ink slurry is obtained. During the dispersion process, circulating cooling water needs to be turned on to control the material temperature to not exceed 50℃. The premixed ink slurry is then passed through a three-roll mill to obtain a ground ink slurry. The roller gap is set as follows: 50μm for the first pass, 20μm for the second pass, and 5-10μm for the third pass. The cooling water temperature is controlled at 15℃. This process utilizes shear force to depolymerize and initially orient the flake mica. The ground ink slurry is then added to a vacuum mixer, along with 0.6 parts of defoamer BYK-A 530. Under a vacuum of -0.098MPa, the mixture is slowly stirred at 60rpm for 40-55 minutes to defoam. After discharge, the mixture is allowed to stand at room temperature for 24 hours to obtain a high thermal conductivity insulating ink. The functional mica filler is prepared from synthetic mica powder, hydroxylated boron nitride, and silane coupling agent KH-560.

[0009] Preferably, the preparation method of hyperbranched polyester modified epoxy resin is as follows: 100 parts of epoxy resin E-51 are added to a reaction vessel and heated to 90°C. 20-30 parts of hydroxyl-terminated hyperbranched polyester (model HyPer H202, purchased from Wuhan Hyperbranched Resin Technology Co., Ltd.) are added, along with 0.5 parts of dimethylbenzylamine catalyst. The mixture is stirred at 500 rpm for 2.5 hours at 110°C. After cooling, the mixture is discharged to obtain hyperbranched polyester modified epoxy resin with low viscosity characteristics.

[0010] Preferred method for preparing functional mica filler is as follows: 100 parts of ethanol aqueous solution (95wt%) are mixed with 4 parts of silane coupling agent KH-560, stirred evenly, and the pH value is adjusted to 4-5 with acetic acid. After hydrolysis for 30 min, 50 parts of synthetic mica powder (aspect ratio > 60) are added, and the mixture is stirred at 800 rpm for 1 h in a 60℃ water bath to activate its surface. 10-20 parts of hydroxylated boron nitride (purchased from Suzhou Beike Nanotechnology Co., Ltd.) are added, the temperature is raised to 80℃, and the stirring speed is increased to 1500 rpm for 2-4 h. Boron nitride is loaded onto the mica surface by utilizing the bridging effect of the coupling agent. The mixture is filtered, dried in an oven at 120℃ for 4 h, pulverized and sieved to obtain functional mica filler.

[0011] Preferably, the hybrid microsheet preparation method is as follows: Graphene oxide (sheet diameter 1-5 μm, thickness 0.8-1.2 nm, oxygen content 35%-45%) is dispersed in deionized water to prepare a graphene oxide suspension with a concentration of 2 mg / mL. This suspension is then mixed with hexagonal boron nitride micropowder (purchased from Forsmann Technology (Beijing) Co., Ltd., particle size 0.5-0.8 μm) at a mass ratio of 1:5-10. After ultrasonic dispersion at 800 W for 1 h, the mixture is spray-dried and then calcined at 800 °C for 2 h under nitrogen protection for thermal reduction to obtain hybrid microsheets. This step ensures that trace amounts of graphene are encapsulated by insulating boron nitride, utilizing the high thermal conductivity of graphene without compromising the overall insulation.

[0012] The preferred method for preparing titanate-modified spherical alumina is as follows: 100 parts of spherical alumina (α-phase, average particle size 2-5 μm) are added to a high-speed mixer and preheated to 85°C for 30 min to remove surface adsorbed water; 1.5-2.5 parts of phosphorus-containing titanate coupling agent isopropyltris(dioctylpyrophosphoyloxy) titanate (model KR-38S) are dissolved in 20 parts of anhydrous isopropanol to prepare a modification solution; the modification solution is sprayed evenly onto the surface of the spherical alumina in the form of a spray while stirring, and the reaction is carried out at a stirring speed of 1000 rpm for 35-50 min; the alumina is then vacuum dried at 110°C for 2 h to obtain titanate-modified spherical alumina.

[0013] Preferably, the latent curing agent is composed of dicyandiamide (average particle size < 5 μm) and 3-phenyl-1,1-dimethylurea in a mass ratio of 3:1.

[0014] Another aspect of the present invention provides a high thermal conductivity insulating ink, which is prepared by any of the above preparation methods; the raw materials for preparing the high thermal conductivity insulating ink include hyperbranched polyester modified epoxy resin, dispersant, leveling agent, functional mica filler, titanate modified spherical alumina, hybrid microflakes, latent curing agent and defoamer.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention constructs a functional mica filler with a "mica core and boron nitride shell" by in-situ growth of hydroxylated boron nitride on the surface of mica. This structure utilizes the excellent voltage breakdown resistance of mica sheets as an insulating framework, while utilizing the high thermal conductivity of the boron nitride shell to construct a high-speed channel for phonon transmission. Compared with direct mixing, this synergistic effect solves the problems of poor thermal conductivity of single mica and easy agglomeration of single boron nitride, enabling the ink to significantly improve the overall thermal conductivity while maintaining high volume resistivity and breakdown voltage.

[0016] 2. This invention resolves the contradiction between high filler content and printability through a dual approach of "resin modification" and "curing system optimization." On one hand, hyperbranched polyester-modified epoxy resin is introduced into the resin matrix. Its highly branched spherical three-dimensional structure acts as a "molecular ball bearing," significantly reducing the system viscosity. On the other hand, a latent curing agent system combining micronized dicyandiamide and organic urea accelerators is used. The micronization avoids physical clogging caused by curing agent particles, while the latent nature imparts excellent storage stability and an ultra-long pot life to the ink, preventing viscosity increases during printing due to pre-reaction. This synergistic effect of "physical viscosity reduction and chemical viscosity stabilization" ensures that the ink maintains excellent thixotropy and leveling properties even at high filler contents, resulting in smooth ink flow, clear line edges, and suitability for printing fine lines.

[0017] 3. This invention utilizes large-size sheet-like functional mica, spherical alumina, and micro-modified graphene / boron nitride hybrid flakes to achieve multi-level geometric spatial synergy of "large sheets + medium spheres + small flakes". Large-size sheet-like mica constructs the main insulating pathways; spherical alumina utilizes its rolling effect to fill the gaps between the mica sheets, preventing sedimentation and increasing packing density; micro-hybrid flakes further fill the dead corners where the spheres and sheets meet. This dense packing structure maximizes the effective contact area between the fillers, significantly reduces the thermal resistance inside the cured coating, and forms a continuous and stable thermal conduction path.

[0018] 4. This invention employs a differentiated dual-interface modification strategy, significantly optimizing interfacial thermal resistance and mechanical properties. Spherical alumina is treated with a phosphorus-containing titanate coupling agent, while functional mica is modified with a silane coupling agent. One end of the titanate reacts with the hydroxyl groups on the alumina surface, while the other end crosslinks with the epoxy resin matrix, establishing a strong chemical bond between the alumina and the organic resin. The long-chain structure of the titanate significantly reduces the viscosity increase caused by high-filler alumina, and its phosphorus-containing groups improve phonon modulus matching. This targeted chemical bridging effect, combined with the silane-modified layer on the mica surface, greatly reduces phonon scattering at the organic / inorganic interface, resulting in smoother heat transfer. Simultaneously, the comprehensive chemical bonding significantly enhances the adhesion between the ink and the substrate after curing, preventing coating peeling and detachment.

[0019] 5. This invention utilizes a specific process combination of "high-speed shear pre-dispersion + three-roll mill strong shearing + vacuum degassing" to induce the oriented arrangement of sheet-like functional mica along the planar direction within the coating using strong shearing force. This ordered arrangement maximizes the blocking path of electron migration by the mica, further improving insulation performance; simultaneously, the vacuum degassing process removes microbubbles (poor thermal conductors) from within the ink, ensuring the density and uniformity of the coating and avoiding hot spot concentration and insulation failure caused by pores. Attached Figure Description

[0020] Figure 1 The figures show the thermal conductivity test results of Examples 1-4 and Comparative Examples 1-3 and 7-11 of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see Figure 1 This invention provides a high thermal conductivity insulating ink and its preparation method, the technical solution of which is as follows: Example

[0023] 100 parts of epoxy resin E-51 were added to a reactor and heated to 90°C. 20 parts of terminal hydroxyl hyperbranched polyester and 0.5 parts of catalyst dimethyl benzylamine were added. The mixture was stirred at 500 rpm for 2.5 h at 110°C. The viscosity of the system was monitored. When the viscosity tended to stabilize, the mixture was immediately cooled and discharged to obtain hyperbranched polyester modified epoxy resin with low viscosity.

[0024] 100 parts of ethanol aqueous solution (95wt%) were mixed with 4 parts of silane coupling agent KH-560, stirred evenly, and the pH value was adjusted to 4-5 with acetic acid. After hydrolysis for 30 min, 50 parts of synthetic mica powder (diameter-to-thickness ratio > 60) were added, and the mixture was stirred at 800 rpm for 1 h in a 60℃ water bath. Then, 10 parts of hydroxylated boron nitride were added, the temperature was raised to 80℃, the stirring speed was increased to 1500 rpm, and the reaction was carried out for 2 h. The mixture was filtered, dried in an oven at 120℃ for 4 h, pulverized, and sieved to obtain the functional mica filler.

[0025] Graphene oxide was dispersed in deionized water to prepare a graphene oxide suspension with a concentration of 2 mg / mL. The suspension was then mixed with hexagonal boron nitride micro powder at a mass ratio of 1:5. After ultrasonic dispersion at 800 W for 1 h, the suspension was spray-dried and then thermally reduced by calcination at 800 °C for 2 h under nitrogen protection to obtain hybrid micro flakes.

[0026] 100 parts of spherical alumina (α-phase, average particle size 2-5 μm) were added to a high-speed mixer and preheated to 85℃ for 30 min to remove surface adsorbed water. 1.5 parts of phosphorus-containing titanate coupling agent isopropyltris(dioctylpyrophosphoryloxy) titanate (model KR-38S) were dissolved in 20 parts of anhydrous isopropanol to prepare a modification solution. The modification solution was sprayed evenly onto the surface of the spherical alumina under stirring, and the reaction was carried out at a stirring speed of 1000 rpm for 35 min. The mixture was then vacuum dried at 110℃ for 2 h to obtain titanate-modified spherical alumina.

[0027] 25 parts of hyperbranched polyester-modified epoxy resin, 1.6 parts of dispersant, and 0.8 parts of leveling agent were mixed and stirred at 400 rpm for 5 minutes. Then, 35 parts of functional mica filler, 30 parts of titanate-modified spherical alumina, 3 parts of hybrid microflakes, and 2 parts of latent curing agent were added sequentially. The speed was increased to 2000 rpm, and the mixture was stirred and dispersed for 40 minutes to obtain a premixed ink slurry. During dispersion, circulating cooling water was turned on to control the material temperature to not exceed 50℃. The premixed ink slurry was then passed through a three-roll mill to obtain a ground ink slurry. Roller gap: 50μm for the first pass, 20μm for the second pass, and 5-10μm for the third pass, with cooling water temperature controlled at 15℃; the grinding ink slurry is added to a vacuum mixer, along with 0.6 parts of defoamer, and stirred slowly at 60rpm for 40min under a vacuum of -0.098MPa to remove bubbles. After discharge, the material is left to stand and age at room temperature for 24h to obtain a high thermal conductivity insulating ink; the latent curing agent is composed of dicyandiamide (average particle size <5μm) and 3-phenyl-1,1-dimethylurea in a mass ratio of 3:1. Example

[0028] Referring to the preparation method and parameters of Example 1, the differences are as follows: when preparing functional mica filler, the amount of boron hydroxyl nitride is 13 parts, and the stirring speed is increased to 1500 rpm for 2.5 h; when preparing hybrid microplates, the graphene oxide suspension and hexagonal boron nitride micro powder are mixed at a mass ratio of 1:6.5; when preparing titanate-modified spherical alumina, the amount of phosphorus-containing titanate coupling agent is 1.8 parts, and the stirring speed is maintained at 1000 rpm for 40 min; when preparing high thermal conductivity insulating ink, the amount of functional mica filler is 40 parts, the amount of titanate-modified spherical alumina is 35 parts, and the amount of hybrid microplates is 4 parts. After mixing all materials, the stirring speed is increased to 2200 rpm, and the vacuum degassing time is 45 min. Example

[0029] Referring to the preparation method and parameters of Example 1, the differences are as follows: when preparing functional mica filler, the amount of boron hydroxyl nitride is 16 parts, and the stirring speed is increased to 1500 rpm for 3 hours; when preparing hybrid microflakes, the graphene oxide suspension and hexagonal boron nitride micro powder are mixed at a mass ratio of 1:8; when preparing titanate-modified spherical alumina, the amount of phosphorus-containing titanate coupling agent is 2.2 parts, and the stirring speed is maintained at 1000 rpm for 45 minutes; when preparing high thermal conductivity insulating ink, the amount of functional mica filler is 45 parts, the amount of titanate-modified spherical alumina is 40 parts, and the amount of hybrid microflakes is 5 parts. After mixing all materials, the stirring speed is increased to 2600 rpm, and the vacuum degassing time is 45 minutes. Example

[0030] Referring to the preparation method and parameters of Example 1, the differences are as follows: when preparing functional mica filler, the amount of boron hydroxyl nitride is 20 parts, and the stirring speed is increased to 1500 rpm for 4 hours; when preparing hybrid microflakes, the graphene oxide suspension and hexagonal boron nitride micro powder are mixed at a mass ratio of 1:10; when preparing titanate-modified spherical alumina, the amount of phosphorus-containing titanate coupling agent is 2.5 parts, and the stirring speed is maintained at 1000 rpm for 50 minutes; when preparing high thermal conductivity insulating ink, the amount of functional mica filler is 50 parts, the amount of titanate-modified spherical alumina is 45 parts, and the amount of hybrid microflakes is 6 parts. After mixing all materials, the stirring speed is increased to 3000 rpm, and the vacuum degassing time is 45 minutes.

[0031] Comparative Example 1 The preparation method and parameters of Example 1 were used, except that 25 parts of hyperbranched polyester modified epoxy resin were replaced with 25 parts of ordinary epoxy resin E-51.

[0032] Comparative Example 2 The preparation method and parameters of Example 1 were used, except that in-situ growth grafting on the mica surface was not performed. Instead, 50 parts of synthetic mica powder and 10 parts of hydroxylated boron nitride were directly physically mixed and stirred in ethanol, and then dried before use.

[0033] Comparative Example 3 The preparation method and parameters of Example 1 were used, except that 35 parts of functional mica filler were replaced with an equal amount of synthetic mica powder.

[0034] Comparative Example 4 The preparation method and parameters are the same as in Example 1, except that no functional mica filler is added.

[0035] Comparative Example 5 The preparation method and parameters of Example 1 are the same, except that hexagonal boron nitride powder is not added during the preparation of the hybrid microsheets, and graphene oxide is directly used for spray drying and reduction.

[0036] Comparative Example 6 The preparation method and parameters of Example 1 are the same, except that the graphene oxide and hexagonal boron nitride micro powders are not made into hybrid micro powders, but are added directly during the ink preparation process. The mass ratio of the two is 1:5, and a total of 3 parts are added.

[0037] Comparative Example 7 The preparation method and parameters of Example 1 were used, except that 3 parts of hybrid micro flakes were replaced with 3 parts of hexagonal boron nitride micro powder.

[0038] Comparative Example 8 The preparation method and parameters were the same as in Example 1, except that no hybrid microplates were added.

[0039] Comparative Example 9 The preparation method and parameters of Example 1 are the same, except that the spherical alumina used in the preparation of titanate-modified spherical alumina is β-phase.

[0040] Comparative Example 10 The preparation method and parameters of Example 1 were used, except that the spherical alumina was not modified.

[0041] Comparative Example 11 The preparation method and parameters of Example 1 were used, except that titanate-modified spherical alumina were not added.

[0042] Experiment Example 1: Insulation Performance Test The inks prepared in the examples and comparative examples were printed onto the substrate using a 120-mesh polyester screen. The printing squeegee had a hardness of 75 degrees and a printing angle of 75°. After printing, the inks were allowed to stand at room temperature for 15 minutes to level, and then placed in a forced-air drying oven for heat curing according to the procedure of "holding at 80°C for 30 minutes → raising the temperature to 150°C and holding for 60 minutes → cooling with the oven". The thickness of the cured dry film was controlled at 50 μm to form test samples. Volume resistivity was tested according to GB / T 1410 standard; electrical strength was tested according to GB / T 1408.1-2016 standard, with a step-up rate of 500V / s; the results are shown in Table 1.

[0043] Table 1 Insulation performance tests of Examples 1-4 and Comparative Examples 4-6 Group Volume resistivity / Ω·cm Electrical strength / kV / mm Example 1 <![CDATA[2.8×10 14 ]]> 35.1 Example 2 <![CDATA[5.2×10 14 ]]> 35.6 Example 3 <![CDATA[8.5×10 14 ]]> 36.5 Example 4 <![CDATA[7.4×10 14 ]]> 36.0 Comparative Example 4 <![CDATA[3.7×10 11 ]]> 14.8 Comparative Example 5 <![CDATA[4.6×10 5 ]]> ＜0.1 Comparative Example 6 <![CDATA[2.1×10 9 ]]> 5.6 As shown in Table 1, in Examples 1-4, while pursuing high thermal conductivity, insulation reliability was ensured through the strategies of "structural isolation" and "path blocking." The core contribution lies in the preparation of modified graphene / boron nitride hybrid microsheets. Through spray drying and calcination processes, the insulating boron nitride tightly encapsulates the conductive graphene, physically blocking electronic transitions between graphene sheets and preventing the formation of conductive pathways. This fundamentally solves the risk of insulation failure caused by the addition of carbon-based materials. In addition, the process employs "strong shear orientation" technology to induce the orderly arrangement of sheet-like functional mica along the planar direction within the coating. This layered structure significantly extends the electron breakdown path (torsional effect), greatly improving the voltage withstand capability. Combined with the vacuum degassing process, microbubbles (air is easily ionized) are thoroughly removed, eliminating the risk of partial discharge. Ultimately, the ink maintains a volume resistivity of 10 even with high filling levels. 4 The electrical strength reached 36.5 kV / mm. In Comparative Example 4, no functional mica filler was added, leaving only spherical alumina and hybrid microflakes in the insulation system. The spherical filler could not form a continuous layered barrier, allowing electrons to migrate along straight or shorter paths through the resin matrix between the spheres under the influence of the electric field. This shortened path directly led to an increase in leakage current. In Comparative Example 5, hexagonal boron nitride powder was not added during the preparation of the hybrid microflakes; instead, graphene oxide was directly spray-dried and reduced. When the conductive graphene oxide dispersed and overlapped in the ink, it quickly reached the conductive percolation threshold, forming a connected conductive network in the insulating resin matrix. At this point, the ink transformed from an insulator into a semiconductor or even a conductor, with a sharp drop in volume resistivity, losing its insulating function. In Comparative Example 6, graphene oxide and hexagonal boron nitride micropowder were not prepared as hybrid micropowders, but were added directly during the ink preparation process. The mass ratio of the two was 1:5, with a total of 3 parts added. During the ink dispersion process, the hexagonal boron nitride micropowder and graphene oxide were dispersed independently. Due to the lack of a strong coating structure, there was a high probability that the exposed graphene oxide sheets would come into direct contact, or that BN would fail to effectively isolate the overlap between the graphene oxide sheets. This randomness led to uncontrollable insulation performance: some areas may have good insulation, but some micro-regions would form conductive paths, resulting in local leakage. Compared with Example 1, its volume resistivity would decrease significantly.

[0044] Experiment Example 2: Thermal Conductivity Test Thermal conductivity was tested according to ASTM E1461 standard; the results are shown in Table 2 and... Figure 1 As shown.

[0045] Table 2 Thermal conductivity test results of Examples 1-4 and Comparative Examples 1-3 and 7-11 Group Thermal conductivity / W / m·K Example 1 2.2 Example 2 2.5 Example 3 3.0 Example 4 2.8 Comparative Example 1 1.5 Comparative Example 2 1.2 Comparative Example 3 0.8 Comparative Example 7 1.8 Comparative Example 8 1.7 Comparative Example 9 1.0 Comparative Example 10 1.6 Comparative Example 11 1.1 From Table 2 and Figure 1As can be seen, in Examples 1-4, the thermal conductivity was significantly improved through two major strategies: "multi-level geometric stacking" and "interface phonon matching." First, a three-dimensional dense stacking network of "sheet-sphere-sheet" was constructed macroscopically. Large-size modified mica served as the thermally conductive framework, while micron-sized spherical alumina filled the framework gaps using the "ball effect," and nano-sized hybrid microflakes further filled the dead zones. This multi-level arrangement maximized the effective contact area between the fillers, significantly reducing contact thermal resistance. Second, the phonon scattering problem was solved microscopically. On the one hand, a "core-shell" structure was constructed by in-situ grafting of highly thermally conductive boron nitride onto the mica surface, compensating for the poor thermal conductivity of the mica body. On the other hand, the ultra-high intrinsic thermal conductivity of graphene in the hybrid microflakes was used as a "thermal bridge." Finally, the dual chemical modification with phosphorus titanate and silane coupling agent improves the interfacial compatibility between inorganic fillers and organic resins, reduces phonon scattering at the interface, and ensures that heat flow can form a continuous and high-speed transport path within the composite material, thereby achieving a thermal conductivity of 3.0 W / m·K. In Comparative Example 1, 25 parts of hyperbranched polyester modified epoxy resin were replaced with 25 parts of ordinary epoxy resin E-51. Thermal conductivity depends not only on the filler but also on the distribution of the filler in the matrix. Ordinary epoxy resin has high viscosity and poor wettability for high-filler content fillers, which leads to two consequences: first, it is difficult for the filler to be arranged into a dense "plate-sphere-plate" structure, reducing the number of contact points; second, the high viscosity causes microbubbles to remain inside the ink, and the thermal conductivity of air is extremely low, which is like inserting countless "circuit breakers" in the heat conduction path, significantly hindering heat flow transfer. In Comparative Example 2, no in-situ growth grafting was performed on the mica surface. 50 parts of synthetic mica powder and 10 parts of hydroxylated boron nitride were directly physically mixed and stirred in ethanol, dried, and then used. Although the composition was the same, the lack of chemical bonding caused the boron nitride nanoparticles to easily agglomerate, failing to uniformly cover the mica surface. When heat flowed from the mica to the boron nitride and then to the resin, it faced significant interfacial thermal resistance. Phonons were severely scattered at the chaotic physical interface, preventing the formation of a continuous pathway like the "mica framework-boron nitride high-speed shell" seen in Example 1. In Comparative Example 3, 35 parts of functional mica filler were replaced with an equal amount of synthetic mica powder. Mica itself has low intrinsic thermal conductivity. Removing the highly thermally conductive boron nitride made the largest volumetric framework material a bottleneck for heat flow, preventing a breakthrough in overall thermal conductivity. In Comparative Example 7, 3 parts of hybrid microsheets were replaced with 3 parts of hexagonal boron nitride powder. Even though hexagonal boron nitride has excellent thermal conductivity, the in-plane thermal conductivity of graphene is much higher than that of boron nitride. After replacing it with pure hexagonal boron nitride powder, although the insulation is safer, the ultra-high thermal conductivity gain brought by graphene is lost, and the heat transfer efficiency of the micro-nodes is reduced.In Comparative Example 8, the absence of hybrid microflakes disrupted the three-tiered dense packing model of "large flakes + medium spheres + small flakes." The tiny gaps between the mica and alumina spheres, which should have been filled by hybrid microflakes, were instead filled by a low-thermal-conductivity resin matrix. This increased the phonon transmission distance in the low-thermal-conductivity medium and reduced the overall effective thermal conductivity. In Comparative Example 9, the spherical alumina used in the preparation of titanate-modified spherical alumina was β-phase. α-phase alumina has a dense corundum structure with high thermal conductivity; however, the β-phase alumina has a loose crystal structure, resulting in slow phonon transmission and an intrinsic thermal conductivity far lower than that of the α-phase. In Comparative Example 10, the unmodified spherical alumina exhibited a polarity difference with the epoxy resin, causing phonons to be reflected or scattered when passing through the "inorganic-organic" interface. Furthermore, the agglomeration caused by uneven dispersion of the unmodified filler also disrupted the thermal conductivity network. In Comparative Example 11, without the addition of titanate-modified spherical alumina, the "spherical support" and "ball effect" were lost, and large-sized mica sheets would directly stack or collapse, resulting in a reduction in contact area. Furthermore, due to the excessive viscosity, a high filling amount could not be achieved, and the lack of geometric bridging by spherical fillers led to a sparse and unstable macroscopic heat conduction network.

[0046] Experiment Example 3 Adhesion Test Adhesion was tested according to ISO 2409 standard; the results are shown in Table 3.

[0047] Table 3 Adhesion tests of Examples 1-4 and Comparative Example 10 Group Adhesion / Grade Example 1 0 Example 2 0 Example 3 0 Example 4 0 Comparative Example 10 3 As shown in Table 2, in Examples 1-4, the spherical alumina was specifically modified by introducing a phosphorus-containing titanate coupling agent. The unique molecular structure of the titanate allows one end to chemically react with the hydroxyl groups on the alumina surface, while the long-chain groups at the other end penetrate the epoxy resin matrix and participate in cross-linking and curing. This strong "molecular rivet" effect greatly enhances the bonding force between the inorganic filler and the resin matrix, as well as between the ink layer and the substrate. Simultaneously, the introduction of the hyperbranched polyester modified resin reduces the system viscosity, giving the ink excellent fluidity and wetting ability on the substrate surface. Good wetting is the basis of physical adsorption, and combined with the enhanced chemical bonding, the adhesion of the cured coatings reaches an excellent level. In the adhesion test, the cut edges are very smooth, and none of the blocks in the grid peel off (grade 0). In Comparative Example 10, the spherical alumina was not modified, lacking the coupling effect of the phosphorus-containing titanate, resulting in poor inorganic / organic interfacial bonding and decreased adhesion. Example

[0048] The preparation method and parameters of Example 3 are the same, except that when preparing hyperbranched polyester modified epoxy resin, the amount of hydroxyl-terminated hyperbranched polyester is 25 parts; and when preparing high thermal conductivity insulating ink, the amount of hyperbranched polyester modified epoxy resin is 30 parts and the amount of latent curing agent is 3.5 parts. Example

[0049] The preparation method and parameters of Example 3 are the same, except that when preparing hyperbranched polyester modified epoxy resin, the amount of hydroxyl-terminated hyperbranched polyester is 30 parts; and when preparing high thermal conductivity insulating ink, the amount of hyperbranched polyester modified epoxy resin is 35 parts and the amount of latent curing agent is 5 parts.

[0050] Experiment Example 4 Viscosity Test Viscosity was tested at 25℃ using a BH type rotational viscometer; the results are shown in Table 4.

[0051] Table 4 Viscosity tests of Examples 3, 5-6 and Comparative Example 1 Group Viscosity (Pa·s) Surface condition Example 3 45.6 Smooth Example 5 44.7 Smooth Example 6 45.0 Smooth Comparative Example 1 182.2 Orange peel / stringy Comparative Example 10 92.5 Orange peel As shown in Table 4, in Examples 3 and 5-6, on the one hand, hyperbranched polyester-modified epoxy resin was introduced into the resin matrix, and its highly branched spherical three-dimensional structure acted as a "molecular ball bearing," significantly reducing the viscosity of the system. On the other hand, a latent curing agent system composed of micronized dicyandiamide and organic urea accelerator was used. The micronization feature avoided physical screen clogging caused by curing agent particles, while the latent feature endowed the ink with excellent storage stability and ultra-long pot life, preventing the ink viscosity from climbing due to pre-reaction during the printing process. The resulting ink viscosity was [value missing], which has ideal screen printing adaptability, and the surface of the ink after printing is smooth and flat. In Comparative Example 1, replacing 25 parts of hyperbranched polyester-modified epoxy resin with 25 parts of ordinary epoxy resin E-51 resulted in problems such as inability to pass through the screen, severe stringing during printing, and poor leveling (orange peel effect) under the same high filler content. This demonstrates the importance of the "hyperbranched structure acting as a molecular ball bearing" in this application, indicating that the modified resin is key to achieving good printability under high filler content. In Comparative Example 10, without modification of the spherical alumina, the friction between fillers was high, resulting in poor flowability and orange peel effect on the printed surface. This demonstrates that the phosphorus-containing titanate coupling agent significantly reduced the friction coefficient of the filler surface, exhibiting excellent viscosity reduction effect.

[0052] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high thermal conductivity insulating ink, characterized in that: The preparation method is as follows: hyperbranched polyester modified epoxy resin, dispersant and leveling agent are mixed and stirred, functional mica filler, titanate modified spherical alumina, hybrid micro flakes and latent curing agent are added in sequence, and the stirring speed is increased to disperse and obtain a premixed ink slurry; the premixed ink slurry is passed through a three-roll mill to obtain a ground ink slurry; the ground ink slurry is added to a vacuum mixer, defoamer is added, and the mixture is stirred to remove bubbles. After discharge, the mixture is allowed to stand and age at room temperature to obtain the high thermal conductivity insulating ink; The functional mica filler is prepared from synthetic mica powder, hydroxylated boron nitride, and silane coupling agent KH-560.

2. The method for preparing a high thermal conductivity insulating ink according to claim 1, characterized in that: The preparation method of the hyperbranched polyester modified epoxy resin is as follows: epoxy resin E-51 is added to a reaction vessel, heated, and then hydroxyl-terminated hyperbranched polyester and catalyst dimethylbenzylamine are added. After heating, the mixture is stirred and reacted, cooled, and discharged to obtain the hyperbranched polyester modified epoxy resin.

3. The method for preparing a high thermal conductivity insulating ink according to claim 1, characterized in that: The preparation method of the functional mica filler is as follows: ethanol aqueous solution is mixed with the silane coupling agent KH-560, stirred evenly, pH value is adjusted for hydrolysis, the synthetic mica powder is added, stirred under water bath, the hydroxylated boron nitride is added, the mixture is heated to react, filtered, dried, pulverized and sieved to obtain the functional mica filler.

4. The method for preparing a high thermal conductivity insulating ink according to claim 1, characterized in that: The hybrid micro-sheets are prepared as follows: a graphene oxide suspension is mixed with hexagonal boron nitride micro powder, ultrasonically dispersed, spray-dried, and calcined under nitrogen protection to obtain the hybrid micro-sheets.

5. The method for preparing a high thermal conductivity insulating ink according to claim 1, characterized in that: The method for preparing the titanate-modified spherical alumina is as follows: the spherical alumina is added to a high-speed mixer and dried; a phosphorus-containing titanate coupling agent is dissolved in anhydrous isopropanol to prepare a modification solution; the modification solution is sprayed evenly onto the surface of the spherical alumina in a spray form under stirring, and then vacuum dried after reaction to obtain the titanate-modified spherical alumina.

6. The method for preparing a high thermal conductivity insulating ink according to claim 1, characterized in that: The latent curing agent is composed of dicyandiamide and 3-phenyl-1,1-dimethylurea.

7. A high thermal conductivity insulating ink, characterized in that: The high thermal conductivity insulating ink is prepared by the preparation method described in any one of claims 1-6; the raw materials for preparing the high thermal conductivity insulating ink include hyperbranched polyester modified epoxy resin, dispersant, leveling agent, functional mica filler, titanate modified spherical alumina, hybrid microflakes, latent curing agent and defoamer.

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