High-thermal-conductivity environment-friendly molding compound and preparation method thereof

Abstract

The invention relates to a high thermal conductivity environment-friendly molding compound and a preparation method thereof, the molding compound takes polydimethylsiloxane as a matrix material and sodium alginate as a raw material to prepare a thermal conductive filler, and the molding compound comprises the following components in percentage by mass: 20-40% of PDMS composite microspheres, 5-20% of a curing agent, 1-20% of a cross-linking agent and 50-70% of other fillers; the PDMS composite microspheres are prepared from polydimethylsiloxane and a heat-conducting filler, and the heat-conducting filler is prepared by reacting sodium alginate with calcium chloride to form calcium alginate gel microspheres and carbonizing the calcium alginate gel microspheres; the mass ratio of the polydimethylsiloxane to the heat-conducting filler is (3-7): 1; according to the plastic packaging material, the heat-conducting property is improved, meanwhile, good mechanical strength and fluidity can still be kept, mechanical stress possibly borne in the packaging and using process of electronic devices can be effectively resisted, and the problems of cracking, deformation and the like are solved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor molding compound preparation technology, and in particular to a high thermal conductivity environmentally friendly molding compound and its preparation method. Background Technology

[0002] In the modern electronics industry, molding compounds play a crucial role as key materials for electronic packaging. From everyday smartphones and tablets to complex computer servers, industrial control equipment, and high-end electronic devices in fields such as automotive electronics and aerospace, molding compounds are widely used in the packaging of various electronic components. Like a "protective armor" for electronic devices, they effectively resist damage to internal electronic components from various external factors such as humid air, chemical corrosion, drastic temperature changes, and mechanical shocks, thus ensuring that electronic devices can operate stably and maintain high reliability in various complex environments.

[0003] As electronic devices rapidly evolve towards miniaturization, high performance, and multifunctionality, higher demands are being placed on the thermal conductivity of molding compounds. In highly integrated chips and power devices, significant amounts of heat can accumulate rapidly within confined spaces. For example, power amplifier chips in 5G communication base stations generate substantial heat under high-frequency, high-power operation. If this heat cannot be dissipated effectively and promptly, the chip temperature will rise sharply, exacerbating electron migration and leading to performance degradation, reduced reliability, and even potential device burnout, severely impacting the normal operation and lifespan of electronic devices. Therefore, improving the thermal conductivity of molding compounds has become crucial to meeting the demands of modern electronic equipment development.

[0004] Traditional molding compounds mostly use organic polymer materials such as epoxy resin as the matrix. Although they show certain advantages in terms of insulation and molding processability, their thermal conductivity is generally low, typically between 1 and 3.5 W / (m·K). This low thermal conductivity makes traditional molding compounds inadequate when facing the increasing heat dissipation requirements of electronic devices, severely limiting further improvements in the performance of electronic devices.

[0005] To improve the thermal conductivity of molding compounds, existing technologies typically add thermally conductive fillers, such as ceramic particles like alumina, aluminum nitride, and silicon nitride. Chinese patent document CN111073217A discloses a high thermal conductivity, low-stress epoxy molding compound for semiconductor packaging, comprising 10-90 parts by weight of epoxy resin, 20-70 parts by weight of phenolic resin (curing agent), 300-800 parts by weight of large-particle-size thermally conductive filler, 20-200 parts by weight of small-particle-size thermally conductive filler, 2-15 parts by weight of ion trapping agent, 0.5-5 parts by weight of low-stress modifier, 0.1-3 parts by weight of coupling agent, 0.1-5 parts by weight of accelerator, 0.1-5 parts by weight of release agent, 1-8 parts by weight of flame retardant, and 0.1-5 parts by weight of colorant; the large-particle-size thermally conductive filler has a size of 20-50 μm and includes one or more of spherical alumina and aluminum nitride; the small-particle-size thermally conductive filler has a size of 0.5-50 μm. The filler material has a particle size of 5 μm, including one or more of obtuse-angled silica, sheet-like alumina, boron nitride, and graphene; and the content of the thermally conductive filler is 70-90% of the total composition mass; the content of the small-particle-size thermally conductive filler is 5-20% of the total thermally conductive filler mass. However, these traditional thermally conductive fillers have many problems. On the one hand, their filling amount often needs to be very high to improve the thermal conductivity to a certain extent, but excessive filling amount will lead to poor processing performance of the molding compound, such as reduced fluidity, making it difficult to achieve uniform filling in complex electronic device packaging; at the same time, mechanical properties will also be affected, becoming more brittle and hard, and prone to cracking under mechanical stress. On the other hand, some traditional thermally conductive fillers have high energy consumption in the production process, and some synthesis processes may cause environmental pollution. These problems are becoming increasingly prominent in today's increasingly stringent environmental protection requirements. In addition, from a resource perspective, the raw materials of some traditional fillers are non-renewable resources, and with the continuous increase in usage, the resource shortage problem is gradually intensifying. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a high thermal conductivity, environmentally friendly molding compound and its preparation method.

[0007] The present invention also provides a polydimethylsiloxane composite microsphere with high thermal conductivity for use in high thermal conductivity environmentally friendly molding compounds.

[0008] The technical problems solved by this invention mainly include: how to improve the thermal conductivity of molding compounds and how to improve the environmental friendliness of molding compounds.

[0009] Terminology Explanation: Polydimethylsiloxane (PDMS) is used as a base material for molding compounds.

[0010] The technical solution of the present invention is as follows: A high thermal conductivity, environmentally friendly molding compound, comprising the following components by weight percentage: The PDMS composite microspheres comprise 20%-40% of the total composition. These microspheres are prepared from polydimethylsiloxane and a thermally conductive filler. The thermally conductive filler is obtained by reacting sodium alginate with calcium chloride to form calcium alginate gel microspheres, followed by carbonization. The mass ratio of the polydimethylsiloxane to the thermally conductive filler is (3-7):1. Hardener 5%-20%; Crosslinking agent 1%-20%; Other fillers account for 50%-70%.

[0011] According to a preferred embodiment of the present invention, the high thermal conductivity environmentally friendly molding compound has the following mass percentage composition: PDMS composite microspheres 30%-35%, curing agent 10%-15%, crosslinking agent 5%-10%, other fillers 55%-60%.

[0012] According to a preferred embodiment of the present invention, the mass ratio of the polydimethylsiloxane to the thermally conductive filler is (4-6):1; most preferably, the mass ratio of the polydimethylsiloxane to the thermally conductive filler is 5:1.

[0013] According to a preferred embodiment of the present invention, the particle size of the PDMS composite microspheres is 20-200 μm, and more preferably, the particle size of the PDMS composite microspheres is 100-150 μm.

[0014] According to a preferred embodiment of the present invention, the polydimethylsiloxane has a viscosity of 1000-10000 mPa·s and a purity of 95-99%.

[0015] According to a preferred embodiment of the present invention, the purity of the sodium alginate is greater than or equal to 98%.

[0016] According to a preferred embodiment of the present invention, the curing agent is dibutyl phthalate, dimethyl phthalate, or methyl methacrylate.

[0017] According to a preferred embodiment of the present invention, the crosslinking agent is vinyltrimethoxysilane or allyltrimethoxysilane.

[0018] According to a preferred embodiment of the present invention, the other filler is silica microspheres; Preferably, the silica microspheres have a particle size of 20-100 μm, and more preferably, the silica microspheres have a particle size of 50-100 μm.

[0019] Secondly, the present invention also provides a method for preparing the above-mentioned high thermal conductivity environmentally friendly molding compound.

[0020] A method for preparing a high thermal conductivity, environmentally friendly molding compound includes the following steps: (1) Sodium alginate is reacted with calcium chloride to prepare calcium alginate gel microspheres, and then the calcium alginate gel microspheres are carbonized to obtain calcium alginate carbonization products, i.e. thermally conductive fillers. (2) After mixing PDMS with the thermally conductive filler obtained in step (1), it is added dropwise to anhydrous ethanol under high-speed stirring to form PDMS composite microspheres, and then the anhydrous ethanol is separated and removed. (3) After mixing PDMS composite microspheres, curing agent, crosslinking agent and other fillers in proportion, the mixture is extruded by screw extrusion and then granulated to form granular products.

[0021] According to a preferred embodiment of the present invention, in step (1), the preparation conditions of the calcium alginate gel microspheres are as follows: a sodium alginate solution with a concentration of 10-30 wt% is added dropwise to a calcium chloride solution with a concentration of 4-8 wt%. Under the stirring of a magnetic stirrer, the mixture is continuously stirred at a speed of 200-400 rpm for 30-60 min to allow the sodium alginate and calcium chloride to react fully and form calcium alginate gel microspheres. After filtration, the microspheres are rinsed with water 3-5 times. The washed calcium alginate gel microspheres are placed in a vacuum drying oven and dried at a temperature of 60-80℃ for 12-24 h to reduce their moisture content to less than 5%.

[0022] According to a preferred embodiment of the present invention, in step (1), the carbonization conditions of the calcium alginate gel microspheres are as follows: the dried calcium alginate gel microspheres are transferred to a tube furnace and carbonized under a nitrogen protective atmosphere. The temperature is raised to 500-800℃ at a heating rate of 5-10℃ / min and maintained at this temperature for 1-3 hours. After carbonization, the microspheres are cooled to room temperature with the furnace to obtain the calcium alginate carbonized product, i.e., the thermally conductive filler. By controlling the carbonization temperature and time, the degree of graphitization and pore structure of the carbonized product can be adjusted, thereby optimizing its thermal conductivity.

[0023] According to a preferred embodiment of the present invention, in step (2), the preparation conditions for the PDMS composite microspheres are as follows: the thermally conductive filler is ground into fine powder and passed through a 500-1000 mesh sieve; the PDMS and thermally conductive filler powder are added to a mixer and stirred at a speed of 300-500 rpm for 3-5 h to mix evenly; the mixed solution is subjected to vacuum degassing treatment; then the mixed solution is added dropwise to anhydrous ethanol at a flow rate of 0.5-2 mL / min using a peristaltic pump, with a stirring speed of 1000-2000 rpm; at the instant the droplets enter the anhydrous ethanol, due to the shear force, the droplets rapidly disperse and form PDMS composite microspheres; after the droplets are added, stirring is continued for 30-60 h. The PDMS composite microspheres were further stabilized by centrifugation. The anhydrous ethanol solution containing the PDMS composite microspheres was cooled to room temperature, and the composite microspheres were separated from the anhydrous ethanol by centrifugation. The microspheres were washed repeatedly with anhydrous ethanol 3-5 times to remove surface residues, and then dried in a vacuum drying oven at 40-60℃ for 6-12 h to obtain the PDMS composite microspheres.

[0024] According to a preferred embodiment of the present invention, in step (3), the preparation conditions of the high thermal conductivity environmentally friendly molding compound are as follows: the prepared PDMS composite microspheres, curing agent, crosslinking agent, and other fillers are added to a twin-screw extruder; the temperature is controlled at 80-120℃ and the screw speed is 100-200 rpm, so that the components are fully mixed and uniformly extruded, and the molding compound is granulated by a granulator to obtain the final high thermal conductivity environmentally friendly molding compound.

[0025] On the other hand, the present invention also provides a composite microsphere for preparing a high thermal conductivity environmentally friendly molding compound, which is prepared by polydimethylsiloxane and thermally conductive filler; the thermally conductive filler is obtained by reacting sodium alginate and calcium chloride to form calcium alginate gel microspheres and then carbonizing them; the preparation conditions of the composite microsphere are the same as steps (1) and (2) of the above preparation method.

[0026] The technical features and beneficial effects of this invention are as follows: 1. High thermal conductivity: By introducing calcium alginate carbonization products as thermally conductive fillers, the thermal conductivity of the molding compound prepared in this invention is significantly improved. Compared with traditional molding compounds based on epoxy resin without the addition of highly efficient thermally conductive fillers, the increased thermal conductivity allows the molding compound to more effectively conduct away the heat generated by electronic devices, reducing device operating temperature and improving its performance and reliability; The molding compound of this invention, when used in high-power LED packaging, can reduce the junction temperature of the LED chip by 10-20°C, thereby extending the lifespan of the LED and improving its luminous efficiency.

[0027] 2. Environmental friendliness: Sodium alginate, as a natural polysaccharide, is widely available and biodegradable. Its carbonization process is carried out under nitrogen protection, avoiding the generation of harmful substances. Compared to traditional non-degradable molding compounds whose production processes may pollute the environment, the molding compound of this invention can gradually degrade in the natural environment after disposal, reducing the burden on the environment and meeting environmental protection requirements.

[0028] 3. Good mechanical properties: The molding compound of this invention improves thermal conductivity while maintaining good mechanical properties, effectively resisting mechanical stress that may occur during the packaging and use of electronic devices, and avoiding problems such as cracking and deformation. This invention innovatively provides a method for preparing PDMS composite microspheres, which enables PDMS and calcium alginate carbonization products to form a uniform and stable network structure. This network structure is beneficial to both the thermal conductivity and mechanical properties of the molding compound.

[0029] 4. Excellent processing performance: Due to the significant reduction in the amount of thermally conductive filler required by this invention, the prepared molding compound exhibits excellent flowability and filling properties during molding, enabling uniform filling in complex electronic device encapsulation. The molding compound of this invention can be smoothly processed in common processing equipment such as twin-screw extruders and injection molding machines, with short molding cycles and high production efficiency. Detailed Implementation

[0030] The present invention will be further described below with reference to embodiments, but is not limited thereto. The described embodiments are some embodiments of the present invention. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. Unless otherwise specified in the embodiments of the present invention, all other aspects are based on existing technology. Additionally, unless otherwise specified, the reagents and equipment used in the embodiments are based on existing technology. Unless otherwise specified, all concentrations in the embodiments are mass percentage concentrations.

[0032] The equipment used in the embodiments of the present invention is as follows: Magnetic stirrer (model: IKE HS10), vacuum drying oven (model: DZF-6050), tube furnace (model: SG-GS1200), peristaltic pump (model: BT100F).

[0033] According to one embodiment of the present invention, a high thermal conductivity environmentally friendly molding compound comprises the following components by weight percentage: 20%-40% PDMS composite microspheres, 5%-20% curing agent, 1%-20% crosslinking agent, and 50%-70% other fillers; more preferably, the high thermal conductivity molding compound comprises the following components by weight percentage: 30%-35% PDMS composite microspheres, 10%-15% curing agent, 5%-10% crosslinking agent, and 55%-60% other fillers.

[0034] The PDMS composite microspheres are prepared from polydimethylsiloxane and thermally conductive filler. The thermally conductive filler is obtained by reacting sodium alginate with calcium chloride to form calcium alginate gel microspheres and then carbonizing them. The mass ratio of polydimethylsiloxane to thermally conductive filler is (3-7):1. More preferably, the mass ratio of polydimethylsiloxane to thermally conductive filler is (4-6):1.

[0035] The particle size of the PDMS composite microspheres is 20-200 μm, and more preferably, the particle size of the PDMS composite microspheres is 100-150 μm.

[0036] Polydimethylsiloxane (PDMS): PDMS with moderate viscosity and high purity is selected. It is liquid at room temperature and possesses good chemical stability, insulation, and flexibility. Preferably, PDMS with a purity of 95-99% and a viscosity of 1000-10000 mPa·s is preferred. This viscosity range is beneficial for the uniformity of subsequent mixing with other materials and for the flowability during molding, ensuring that the molding compound can fully fill the various fine structures of electronic devices and provide good encapsulation results. Before use, PDMS needs to undergo vacuum degassing treatment to remove any possible air bubbles. Place the PDMS in a vacuum drying oven at a vacuum degree of -0.1 MPa for 30-60 minutes to allow the air bubbles to escape completely.

[0037] Sodium alginate: Select high-purity, low-impurity sodium alginate powder, preferably with a purity of ≥98%. The molecular weight of sodium alginate is 216 g / mol. The molecular weight and degree of polymerization of sodium alginate affect the performance of its carbonization products. Therefore, it is necessary to select products with a moderate molecular weight and a narrow degree of polymerization distribution to ensure the consistency of the carbonization process and the stability of the carbonization product performance.

[0038] The curing agent is selected from dibutyl phthalate, dimethyl phthalate, or methyl methacrylate, and the crosslinking agent is selected from vinyltrimethoxysilane or allyltrimethoxysilane, which are used to enhance the network structure of PDMS and improve the mechanical properties of the molding compound. Other fillers are selected from silica microspheres with a particle size of 50-100μm to ensure the mechanical strength, heat resistance, and abrasion resistance of the molding compound.

[0039] The preparation method of the above-mentioned high thermal conductivity environmentally friendly molding compound includes the following steps: (1) To ensure the uniform dispersion of sodium alginate, it needs to be dissolved in deionized water before use to prepare a solution with a mass fraction of 10-30 wt%. Under stirring conditions, slowly add sodium alginate powder to deionized water and continue stirring for 2-4 hours until it is completely dissolved and forms a uniform and transparent solution. A 10-30 wt% sodium alginate solution was added dropwise to a 4-8 wt% calcium chloride solution. The mixture was stirred continuously at 200-400 rpm for 30-60 minutes using a magnetic stirrer to ensure complete reaction between the sodium alginate and calcium chloride, forming calcium alginate gel microspheres. After filtration, the microspheres were rinsed 3-5 times with water. The washed microspheres were then placed in a vacuum drying oven and dried at 60-80℃ for 12-24 hours until the moisture content was below 5%. The dried calcium alginate gel microspheres were transferred to a tube furnace and carbonized under a nitrogen atmosphere. The temperature was increased to 500-800℃ at a rate of 5-10℃ / min and maintained at this temperature for 1-3 hours. After carbonization, the microspheres were cooled to room temperature in the furnace to obtain the carbonized calcium alginate product, which is a thermally conductive filler. By controlling the carbonization temperature and time, the degree of graphitization and pore structure of the carbonized product can be adjusted, thereby optimizing its thermal conductivity.

[0040] (2) Grind the thermally conductive filler into fine powder and pass it through an 800-mesh sieve; add PDMS and thermally conductive filler powder into a mixer and stir at 300-500 rpm for 3-5 h to mix evenly. Perform vacuum degassing treatment on the mixed solution; then add the mixed solution dropwise to anhydrous ethanol at a flow rate of 0.5-2 mL / min using a peristaltic pump. The stirring speed is 1000-2000 rpm. At the moment the droplets enter the anhydrous ethanol, due to the shear force, the droplets quickly disperse and form PDMS composite microspheres. After the droplets are added, continue stirring for 30-60 min to make the morphology of the PDMS composite microspheres more stable; finally, cool the anhydrous ethanol solution containing PDMS composite microspheres to room temperature, separate the PDMS composite microspheres from the anhydrous ethanol by centrifugation, and wash repeatedly with anhydrous ethanol 3-5 times to remove surface residues. Dry in a vacuum drying oven at 40-60℃ for 6-12 h.

[0041] (3) Add the prepared PDMS composite microspheres, curing agent, crosslinking agent and other fillers into a twin-screw extruder; control the temperature at 80-120℃ and the screw speed at 100-200 rpm, so that the components are fully mixed and uniformly extruded, and the molding compound is made into granules by a granulator.

[0042] Sodium alginate, a natural polysaccharide sodium salt extracted from seaweed, possesses advantages such as good biocompatibility, biodegradability, and wide availability, making it an environmentally friendly polymer material. Carbonization of sodium alginate yields carbon materials with unique structures and properties. This carbonization product may exhibit high intrinsic thermal conductivity, and due to its unique porous structure and surface characteristics, it can effectively combine with polydimethylsiloxane (PDMS), improving the thermal conductivity of molding compounds while maintaining good processability and mechanical properties. Furthermore, the environmentally friendly characteristics of calcium alginate carbonization products align with current green development concepts, providing a new direction for addressing the environmentally unfriendly nature of traditional molding compound fillers. An innovative droplet-stirring method for preparing composite microspheres of PDMS and calcium alginate carbonization products can further optimize the composite structure, fully leveraging the advantages of calcium alginate carbonization products to produce high-performance, environmentally friendly novel molding compounds.

[0043] The present invention will be further described below with reference to preferred embodiments and comparative examples.

[0044] Example 1: A high thermal conductivity molding compound, with the following composition by weight percentage: The composition comprises 30% PDMS composite microspheres, 10% dibutyl phthalate as a curing agent, 2% vinyltrimethoxysilane as a crosslinking agent, and 58% silica microspheres as filler. The PDMS composite microspheres are prepared from polydimethylsiloxane and a thermally conductive filler. The particle size of the PDMS composite microspheres is 100-150 μm. The thermally conductive filler is prepared by reacting sodium alginate with calcium chloride to form calcium alginate gel microspheres, followed by carbonization. The mass ratio of polydimethylsiloxane to the thermally conductive filler is 5:1.

[0045] Polydimethylsiloxane (PDMS): viscosity 5000 mPa·s, purity 99%; Sodium alginate: purity 98%, molecular weight 216 g / mol; Calcium chloride: analytical grade, purity 99%; Anhydrous ethanol: analytical grade, purity 99.7%.

[0046] The curing agent is dibutyl phthalate; the crosslinking agent is vinyltrimethoxysilane; and the other filler is silica microspheres with a particle size of 50 μm.

[0047] The preparation method of the above-mentioned high thermal conductivity environmentally friendly molding compound includes the following steps: (1) Accurately weigh 10 g of sodium alginate powder and slowly add it to 100 mL of deionized water. Stir continuously at 300 rpm for 3 h on a magnetic stirrer until the sodium alginate is completely dissolved and a uniform and transparent sodium alginate solution is formed. Slowly add the prepared sodium alginate solution to a 6% calcium chloride solution at a flow rate of 1 mL / min using a peristaltic pump. At the same time, stir continuously at 300 rpm for 45 min on a magnetic stirrer to allow the sodium alginate and calcium chloride to react fully and form calcium alginate gel microspheres. Filter the calcium alginate gel microspheres through a filter device and rinse them repeatedly with deionized water 5 times to remove residual calcium chloride on the surface. Then place the washed microspheres in a vacuum drying oven and dry them at 70℃ for 18 h. Transfer the dried calcium alginate gel microspheres to a tube furnace and perform carbonization treatment under an argon protective atmosphere. The temperature was increased to 650℃ at a heating rate of 8℃ / min and held at this temperature for 3 hours. After carbonization, the furnace was cooled to room temperature to obtain the calcium alginate carbonization product, i.e., the thermally conductive filler. (2) The thermally conductive filler was placed in a grinding mortar and ground into a fine powder, then passed through an 800-mesh sieve. PDMS and the thermally conductive filler powder were added to a beaker and placed on a magnetic stirrer at 400 rpm for 4 h to ensure thorough mixing. The mixture was then degassed under vacuum and placed in a vacuum drying oven at -0.1 MPa for 30-60 min. The mixture was then added dropwise to anhydrous ethanol at a flow rate of 1 mL / min using a peristaltic pump. The temperature of the anhydrous ethanol was controlled at 25℃, and the stirring speed was 1500 rpm. At the instant the droplets entered the anhydrous ethanol, the droplets rapidly dispersed and formed PDMS composite microspheres due to shear force. After the droplets were added, stirring was continued for 45 min to further stabilize the morphology of the PDMS composite microspheres. The anhydrous ethanol solution containing the PDMS composite microspheres was centrifuged at 2000 rpm for 15 min using a high-speed centrifuge to separate the PDMS composite microspheres from the anhydrous ethanol. The composite microspheres were then washed five times with anhydrous ethanol. The washed composite microspheres were then placed in a vacuum drying oven and dried at 50°C for 9 hours.

[0048] (3) The prepared PDMS composite microspheres are mixed with curing agent, crosslinking agent and other fillers in a container. The mixed material is added to a twin-screw extruder. The temperature of the extruder is controlled at 100℃ and the screw speed is 150rpm to ensure that the components are fully mixed and uniform. Then the material is extruded and granulated to form granules with a particle size of 300-500 μm through a granulator to obtain the final high thermal conductivity environmentally friendly plastic sealant.

[0049] Application example: Using the molding compound from Example 1 in high-power LED packaging can reduce the junction temperature of the LED chip by 15-20°C, thereby extending the lifespan of the LED and improving its luminous efficiency.

[0050] Terminology Explanation: The junction temperature of an LED chip refers to the actual operating temperature of the LED's core light-emitting region (i.e., the semiconductor PN junction).

[0051] Example 2: As described in Example 1, the difference is: A high thermal conductivity molding compound, comprising the following components by weight percentage: The composition consists of 20% PDMS composite microspheres, 10% curing agent, 2% crosslinking agent, and 68% other fillers. The composite microspheres are prepared from polydimethylsiloxane and thermally conductive fillers. The thermally conductive fillers are prepared by reacting sodium alginate with calcium chloride to form calcium alginate gel microspheres and then carbonizing them.

[0052] The mass ratio of polydimethylsiloxane to thermally conductive filler is 4:1.

[0053] The curing agent is dimethyl phthalate.

[0054] The crosslinking agent is allyltrimethoxysilane.

[0055] The preparation method is the same as described in Example 1, except that: In step (1), during the reaction of sodium alginate and calcium chloride, the mixture is stirred continuously at 300 rpm for 45 min; during the carbonization of calcium alginate gel microspheres, the temperature is raised to 600℃ at a heating rate of 10℃ / min and maintained at this temperature for 3 h.

[0056] In step (2), during the formation of PDMS composite microspheres, a mixed solution of PDMS and calcium alginate carbonization product powder is added dropwise to anhydrous ethanol being stirred at high speed using a peristaltic pump at a flow rate of 1 mL / min and a stirring speed of 500 rpm.

[0057] Example 3: As described in Example 1, the difference is: A high thermal conductivity molding compound, comprising the following components by weight percentage: The composition consists of 40% PDMS composite microspheres, 10% curing agent, 2% crosslinking agent, and 48% other fillers. The composite microspheres are prepared from polydimethylsiloxane and thermally conductive fillers. The thermally conductive fillers are prepared by reacting sodium alginate with calcium chloride to form calcium alginate gel microspheres and then carbonizing them.

[0058] The mass ratio of polydimethylsiloxane to thermally conductive filler is 7:1.

[0059] The curing agent is methyl methacrylate.

[0060] The preparation method is the same as described in Example 1, except that: In step (1), during the reaction of sodium alginate and calcium chloride, the mixture is stirred continuously at 300 rpm for 45 min; during the carbonization of calcium alginate gel microspheres, the temperature is raised to 700℃ at a heating rate of 10℃ / min and maintained at this temperature for 3 h.

[0061] In step (2), during the formation of PDMS composite microspheres, a mixed solution of PDMS and thermally conductive filler powder is added dropwise to anhydrous ethanol being stirred at high speed using a peristaltic pump at a flow rate of 1 mL / min. The stirring speed is 2000 rpm.

[0062] Comparative Example 1: As described in Example 1, the difference is: Step (2) does not involve the preparation of PDMS composite microspheres; In step (3), PDMS, thermally conductive filler powder, curing agent, crosslinking agent and other fillers are added to the twin-screw extruder; The other steps and conditions are the same as in Example 1.

[0063] Comparative Example 2: As described in Example 1, the difference is: In step (1), the calcium alginate gel microspheres are not carbonized; In step (2), the preparation of PDMS composite microspheres is not performed; In step (3), PDMS, thermally conductive filler powder, curing agent, crosslinking agent and other fillers are added to the twin-screw extruder.

[0064] The other steps and conditions are the same as in Example 1.

[0065] Experimental example: The molding compound samples prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests, including thermal conductivity, flexural strength, elongation at break and flowability. The results are shown in Table 1.

[0066] Table 1

[0067] As shown in Table 1, the thermal conductivity of the molding compounds in Examples 1-3 is all above 4.5 W / (m·K), with a maximum of 5.6 W / (m·K); the flexural strength is all above 140 MPa; the elongation at break is all above 120%; and the flowability is up to 131 cm. Therefore, the molding compounds of the present invention have excellent thermal conductivity, mechanical properties, and flowability. Compared with Comparative Examples 1 and 3, Example 1 has higher thermal conductivity, flexural strength, and elongation at break, indicating that calcium alginate carbonization products, as thermally conductive fillers, can significantly improve the thermal conductivity of the molding compounds, effectively meeting the heat dissipation requirements of electronic devices. Furthermore, the PDMS and calcium alginate carbonization product powder form a uniform and stable composite structure, enabling the molding compounds to maintain good mechanical strength and flexibility while improving thermal conductivity. This effectively resists the mechanical stress that may be experienced during the packaging and use of electronic devices, reducing cracking, deformation, and other problems.

[0068] Compared with traditional molding compounds, the molding compound of the present invention is biodegradable after disposal, has minimal impact on the environment, and has obvious environmental advantages.

[0069] In summary, the molding compound prepared by this invention exhibits excellent performance in terms of thermal conductivity, mechanical properties, and environmental indicators, effectively verifying the effectiveness and advantages of this invention and demonstrating broad application prospects.

Claims

1. A high thermal conductive environmentally friendly plastic encapsulation material, characterized in that, A heat-conducting filler is prepared by using polydimethylsiloxane as a base material and sodium alginate as a raw material, and includes the following components by mass percentage: PDMS composite microspheres 20%-40%, which are prepared from polydimethylsiloxane and a heat-conducting filler, the heat-conducting filler being prepared by carbonizing calcium alginate gel microspheres formed by reacting sodium alginate with calcium chloride; the mass ratio of the polydimethylsiloxane to the heat-conducting filler being (3-7):1; a curing agent 5%-20%; a crosslinking agent 1%-20%; other fillers 50%-70%.

2. The high thermal conductive environmentally friendly plastic encapsulation material of claim 1, wherein, The high-heat-conducting plastic sealing material includes the following components by mass percentage: PDMS composite microspheres 30%-35%, a curing agent 10%-15%, a crosslinking agent 5%-10%, and other fillers 55%-60%.

3. The high thermal conductive environmentally friendly plastic encapsulation material of claim 1, wherein, The mass ratio of the polydimethylsiloxane to the heat-conducting filler is (4-6):1; most preferably, the mass ratio of the polydimethylsiloxane to the heat-conducting filler is 5:

1.

4. The high thermal conductive environmentally friendly plastic encapsulation material of claim 1, wherein, The particle size of the PDMS composite microspheres is 20-200 μm, and further preferably, the particle size of the PDMS composite microspheres is 100-150 μm.

5. The high thermal conductive environmentally friendly plastic encapsulation material of claim 1, wherein, One or more of the following conditions are included: i. the curing agent is dibutyl phthalate, dimethyl phthalate or methyl methacrylate; ii. the crosslinking agent is vinyltrimethoxysilane or allyltrimethoxysilane; iii. the other fillers are silica microspheres.

6. A preparation method of the high-thermal-conductivity environment-friendly plastic encapsulating material, for preparing the high-thermal-conductivity environment-friendly plastic encapsulating material according to any one of claims 1-5, characterized in that, The steps include the following: (1) reacting sodium alginate with calcium chloride to prepare calcium alginate gel microspheres, and then carbonizing the calcium alginate gel microspheres to obtain a calcium alginate carbonization product, i.e., a heat-conducting filler; (2) mixing PDMS with the heat-conducting filler powder prepared in step (1), and then dropping the mixture into high-speed stirring anhydrous ethanol to form PDMS composite microspheres, and then separating and removing the anhydrous ethanol; (3) mixing the PDMS composite microspheres, the curing agent, the crosslinking agent and the other fillers in a proportion, and then screw extruding and granulating to obtain a granular product.

7. The preparation method of the high-thermal-conductivity environmentally friendly plastic packaging material according to claim 6, characterized in that, One or more of the following conditions are included: a. In step (1), the preparation conditions of the calcium alginate gel microspheres are as follows: A sodium alginate solution with a concentration of 10-30 wt% is dropped into a calcium chloride solution with a concentration of 4-8 wt%, and stirring is continuously performed at a speed of 200-400 rpm for 30-60 min under the stirring of a magnetic stirrer, so that the sodium alginate and the calcium chloride are fully reacted to form calcium alginate gel microspheres, which are then filtered and washed with water for 3-5 times, and the washed calcium alginate gel microspheres are placed in a vacuum drying oven and dried at a temperature of 60-80℃ for 12-24 h, so that the water content is less than 5%; b. In step (1), the carbonization conditions of the calcium alginate gel microspheres are as follows: The dried calcium alginate gel microspheres are transferred to a tube furnace, and carbonization treatment is carried out under a nitrogen protective atmosphere, the temperature is raised to 500-800 DEG C at a heating rate of 5-10 DEG C / min, and the temperature is kept at this temperature for 1-3 h, after the carbonization is completed, the furnace is cooled to room temperature, and the calcium alginate carbonization product, i.e. the heat-conducting filler, is obtained; by controlling the carbonization temperature and time, the graphitization degree and pore structure of the carbonization product can be controlled, and the heat-conducting performance is optimized.

8. The preparation method of the high-thermal-conductivity environmentally friendly plastic packaging material according to claim 6, characterized in that, In the step (2), the preparation conditions of the PDMS composite microspheres are as follows: The heat-conducting filler is ground into fine powder and sieved through a 500-1000 mesh sieve; the PDMS and the heat-conducting filler powder are added to a blender, and stirred at a speed of 300-500 rpm for 3-5 h to mix uniformly, the mixed solution is subjected to vacuum degassing treatment, and then the mixed solution is added dropwise to anhydrous ethanol under high-speed stirring at a flow rate of 0.5-2 mL / min, the stirring speed is 1000-2000 rpm, at the moment when the droplets enter the anhydrous ethanol, the droplets are rapidly dispersed and form PDMS composite microspheres due to the action of shear force, after the droplets are added, the stirring is continued for 30-60 min to make the morphology of the PDMS composite microspheres more stable; the anhydrous ethanol solution containing the PDMS composite microspheres is cooled to room temperature, the PDMS composite microspheres are separated from the anhydrous ethanol by centrifugal separation, and washed repeatedly with anhydrous ethanol for 3-5 times to remove the surface residues, and dried in a vacuum drying oven at 40-60 DEG C for 6-12 h.

9. The preparation method of the high-thermal-conductivity environmentally friendly plastic packaging material according to claim 6, characterized in that, In the step (3), the preparation conditions of the high-heat-conducting environment-friendly plastic encapsulating material are as follows: The prepared PDMS composite microspheres, curing agent, crosslinking agent and other fillers are added to a twin-screw extruder, the temperature is controlled at 80-120 DEG C, and the screw rotation speed is 100-200 rpm, the components are fully mixed and uniformly extruded, the plastic encapsulating material is made into granules by a granulator, and the final high-heat-conducting environment-friendly plastic encapsulating material is prepared.

10. A high thermal conductive environment-friendly composite microsphere, characterized in that, The high-heat-conducting environment-friendly plastic encapsulating material for preparing the high-heat-conducting environment-friendly plastic encapsulating material of any one of claims 1-5 is prepared from polydimethylsiloxane and heat-conducting filler; the heat-conducting filler is prepared by carbonizing calcium alginate gel microspheres which are formed by the reaction of sodium alginate and calcium chloride.

Images