A high-adhesion, low-moisture-absorption solid epoxy encapsulant, its preparation method and application

Abstract

The present invention relates to the technical field of semiconductor packaging materials, and particularly relates to a high-adhesion and low-moisture-absorption solid epoxy encapsulant and its preparation method and application. The high-adhesion and low-moisture-absorption solid epoxy encapsulant of the present invention comprises the following raw materials in parts by weight: 4-10 parts of epoxy resin, 2-10 parts of phenolic resin, 70-90 parts of inorganic filler, 0.1-0.3 part of colorant, 0.2-0.6 part of release agent, 0.05-0.5 part of modified curing accelerator, 0.2-1.5 parts of ion scavenger, 0.1-0.3 part of coupling agent, 1-5 parts of adhesion promoter, and 0.2-1.5 parts of stress improver. The high-adhesion and low-moisture-absorption solid epoxy encapsulant of the present invention, compared with the traditional epoxy encapsulant, shows relatively excellent mechanical strength, adhesion and extremely low water absorption under the same curing degree.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor packaging materials, and particularly relates to a high-adhesion, low-moisture-absorbing solid epoxy encapsulant, its preparation method and application. Background Art

[0002] As an insulating or structural material, epoxy resin is one of the most widely used integrated circuit packaging materials. Its basic components include epoxy resin, phenolic curing agent, curing accelerator, fused silica, coupling agent and mold release agent, etc. In recent years, about 90% of all semiconductor packaging materials are encapsulated with low-pressure transfer molding compounds made by curing epoxy resin with phenolic resin. This kind of epoxy molding compound usually contains a curing accelerator to accelerate the curing reaction of the resin and increase the molding cycle for mass production. However, due to the different types of curing accelerators used, the reliability of encapsulated semiconductors varies greatly. It is important to select an appropriate curing accelerator to improve the reliability of encapsulated semiconductors, especially in recent years with the emergence of high-end packages such as BGA, POP, Fan-out, and MUF, the selection of curing accelerators has become increasingly important. However, conventional accelerators often have problems such as poor high-temperature adhesion, high moisture absorption, and low reliability during the process of accelerating product curing. This affects their stability, lifespan, packaging effect, and product reliability in complex environments. Therefore, developing an epoxy encapsulant with excellent adhesion at high temperatures and low moisture absorption is of great significance for improving the quality and reliability of semiconductor packaging.

[0003] Patent technical literature CN108192285A improves the adhesion of EMC to the metal substrate by adding a tackifier. However, it needs to add 5 kinds of tackifiers simultaneously, with complex raw materials, poor adaptability, and is easily affected by changes in the supply and demand relationship of raw materials, which is not conducive to stable production.

[0004] Patent technical literature CN114437511A increases the batching process by adding two accelerators in combination, and only has a gain in mold opening strength and glass transition temperature; Patent technical literature CN107428914B discloses an epoxy resin composition, which uses the reaction product of a carbodiimide compound and an imidazole compound as a latent curing accelerator. Although it improves the storage stability and operability without reducing the properties of the resin cured product, the preparation steps of this curing accelerator are still relatively cumbersome and are not conducive to popularization and application in mass production.

[0005] In view of the many problems and deficiencies exposed by the prior art, there is an urgent need for a solid epoxy encapsulant with high stability, high adhesion, and low moisture absorption to cope with more complex and severe usage environments. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a solid epoxy encapsulant with high adhesion and low moisture absorption, as well as a preparation method and application thereof, so as to solve the problems of poor stability, insufficient adhesion and strong moisture absorption of traditional solid epoxy encapsulants.

[0007] Based on the above object, the present invention provides a solid epoxy encapsulant with high adhesion and low moisture absorption, which comprises the following raw materials in parts by weight: 4-10 parts of epoxy resin, 2-10 parts of phenolic resin, 70-90 parts of inorganic filler, 0.1-0.3 part of colorant, 0.2-0.6 part of mold release agent, 0.05-0.5 part of modified curing accelerator, 0.2-1.5 parts of ion scavenger, 0.1-0.3 part of coupling agent, 1-5 parts of adhesion promoter, 0.2-1.5 parts of stress improver;

[0008] The preparation steps of the modified curing accelerator are as follows:

[0009] Add 4-hydroxymethyl-5-methyl-2-phenylimidazole, triethylamine and tetrahydrofuran into a three-necked round-bottom glass flask respectively. Then dissolve 3-(3,5-dichlorophenyl)phenol in tetrahydrofuran and add it dropwise into the three-necked round-bottom glass flask at 60-70 °C, and continuously stir for 8-9 h. After the reaction is completed, carry out rotary evaporation, washing and drying to obtain the modified curing accelerator;

[0010] The dosage ratio of 4-hydroxymethyl-5-methyl-2-phenylimidazole, triethylamine, tetrahydrofuran and 3-(3,5-dichlorophenyl)phenol is 5.5-6 g: 6-7 g: 180-200 ml: 3.4-3.7 g.

[0011] Preferably, the epoxy resin is one or a mixture of any proportions of o-cresol novolac epoxy resin, dicyclopentadiene epoxy resin, polyaromatic epoxy resin, polyfunctional epoxy resin, biphenyl epoxy resin, naphthol novolac epoxy resin, thioether epoxy resin.

[0012] Preferably, the phenolic resin is one or a mixture of any proportions of phenol ether phenolic resin, o-methylphenol phenolic resin, biphenol phenolic resin, polyaromatic phenolic resin, phenol aralkyl phenolic resin.

[0013] Preferably, the inorganic filler is one or a mixture of any proportions of crystalline silica, fused silica, spherical silica, alumina, talc powder, kaolin, carbon fiber, glass fiber.

[0014] Preferably, the colorant is one of carbon black, titanium dioxide, aniline black.

[0015] Preferably, the mold release agent is a wax-based compound.

[0016] Further, the mold release agent is one of palm wax, montanic acid ester wax, polyethylene wax, oxidized polyethylene wax, and polyamide wax.

[0017] Preferably, the ion scavenger is an anion scavenger.

[0018] Preferably, the coupling agent is one or more of mercapto-type silicone coupling agent, amino-type silicone coupling agent, or epoxy-type silicone coupling agent.

[0019] Preferably, the adhesion promoter is one or more of methyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and methyltriethoxysilane.

[0020] Preferably, the stress improver is any one of silicone oil, silicone rubber, and liquid rubber.

[0021] Further, the present invention also provides a preparation method of a high-adhesion and low-moisture-absorption solid epoxy encapsulant, and the specific steps are as follows:

[0022] (1) Add the raw materials into a high-speed mixer and stir evenly to obtain a premix.

[0023] (2) Transfer the premix to an extruder, perform sufficient kneading and mixing, cool and crush to obtain a high-adhesion and low-moisture-absorption solid epoxy encapsulant.

[0024] Preferably, in step (1), the stirring speed of the high-speed mixer is 300 - 400 rpm, and the stirring time is 10 - 15 min.

[0025] Preferably, in step (2), the melting section temperature of the extruder is 100 - 130 °C, and the extrusion temperature is 85 - 100 °C.

[0026] Furthermore, the present invention also provides an application of a high-adhesion and low-moisture-absorption solid epoxy encapsulant, which is applied to the fields of chip packaging, semiconductor packaging, electronic devices, and electromechanical product packaging protection.

[0027] The beneficial effects of the present invention: The modified curing accelerator of the present invention can react with epoxy groups, reduce the reaction activity of epoxy groups, and optimize its compatibility with epoxy resins; at the same time, due to the introduction of phenyl groups, it is inert at room temperature and has no catalytic effect, and can release active components at high temperature to initiate the curing reaction of epoxy resins to ensure good stability during storage and processing.

[0028] The modified curing accelerator provided by the present invention, during the curing process, due to the presence of more nitrogen-containing heterocycles and hydroxymethyl groups in its structure, this polarity can form a strong interaction with the metal surface, such as hydrogen bonds or van der Waals forces, thereby improving the adhesion strength between the epoxy resin and the metal and increasing the adhesion of the epoxy molding compound for encapsulation to the Cu / Ag substrate; at the same time, this curing accelerator can introduce alkoxy ions that can further initiate polymerization reactions to construct a three-dimensional network structure, increasing the bonding points at the interface between the epoxy resin and the metal, and further increasing the adhesion force.

[0029] The modified curing accelerator provided by the present invention, as an imidazole-based curing accelerator, forms a more compact three-dimensional network structure during the curing process, reducing the porosity and free volume inside the material. At the same time, its structure contains phenyl groups, which promotes a higher crosslinking density. As the crosslinking density increases, the movement of polymer chains is restricted, which limits the penetration and diffusion of water molecules, reduces the adsorption of water molecules, and lowers the water absorption rate. In addition, a higher crosslinking density also provides higher strength. Detailed implementation mode

[0030] In order to make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the following further elaborates on the present invention in combination with specific embodiments.

[0031] The sources or properties of the raw materials used in the examples and comparative examples are as follows:

[0032] Epoxy resin: naphthalene-based epoxy resin (DIC, HP5000); XYLOK phenolic resin (Meiwa Kasei Co., Ltd., MEHC-7800M); Curing accelerator: 2MZ purchased from Jiangsu Kangle New Materials, 2P4MHZ, 2MZ-A purchased from Shikoku Kasei Kogyo Co., Ltd., phosphorus-based accelerator TPP-BQ, TPTP purchased from Shanghai Huichuang Trading Co., Ltd.; Carbon black MA-600 purchased from Mitsubishi Chemical Corporation; Palm wax (Toagosei Co., Ltd., WAX POWDER); Oxidized polyethylene wax (Clariant GmbH, LicowaxE PED); Anion scavenger: (Kyowa Chemical Industry Co., Ltd., DHT-4C).

[0033] Example 1: (1) Add 11 g of 4-hydroxymethyl-5-methyl-2-phenylimidazole, 6 g of triethylamine, and 80 ml of tetrahydrofuran to a three-necked round-bottom glass flask respectively. Subsequently, dissolve 2.9 g of 3,3',5,5'-tetrachlorobiphenyl in 100 ml of tetrahydrofuran and add it dropwise to the three-necked round-bottom glass flask at 60 °C, and continuously stir for 8 h. After the reaction is completed, perform rotary evaporation, rinse with deionized water, and then rinse with acetone. Repeat the operation 2-3 times, and then dry in a vacuum oven at 50 °C for 24 h to obtain the modified curing accelerator;

[0034] (2) Add 4 g of naphthalene-based epoxy resin, 2 g of XYLOK phenolic resin, 70 g of spherical silica with a particle size of 50 - 70 μm, 0.1 g of carbon black, 0.1 g of palm wax, 0.1 g of oxidized polyethylene wax, 0.2 g of anion scavenger, 0.1 g of 3-aminopropyltriethoxysilane, 0.5 g of methyltrimethoxysilane, 0.5 g of 3-mercaptopropyltrimethoxysilane, 0.2 g of silicone oil, and 0.5 g of modified curing accelerator into a high-speed mixer in sequence, and stir at 300 rpm for 10 min to obtain a premix;

[0035] (3) Transfer the premix to an extruder, conduct sufficient kneading and mixing, cool and pulverize to obtain a high-adhesion and low-moisture-absorption solid epoxy encapsulant; among them, the melting section temperature of the extruder is 100 °C, and the extrusion temperature is 85 °C.

[0036] Example 2: (1) Add 11.5 g of 4-hydroxymethyl-5-methyl-2-phenylimidazole, 6.5 g of triethylamine, and 90 ml of tetrahydrofuran into a three-necked round-bottom glass flask respectively. Subsequently, dissolve 2.95 g of 3,3',5,5'-tetrachlorobiphenyl in 100 ml of tetrahydrofuran, and dropwise add it to the three-necked round-bottom glass flask at 65 °C, continuously stir for 9 h. After the reaction is completed, perform rotary evaporation, rinse with deionized water, and then rinse with acetone. Repeat the operation 2 - 3 times, and then dry in a vacuum oven at 50 °C for 27 h to obtain a modified curing accelerator;

[0037] (2) Add 7 g of naphthalene-based epoxy resin, 6 g of XYLOK phenolic resin, 80 g of spherical silica with a particle size of 60 μm, 0.2 g of carbon black, 0.3 g of palm wax, 0.1 g of oxidized polyethylene wax, 1 g of anion scavenger, 0.2 g of 3-aminopropyltriethoxysilane, 2 g of methyltrimethoxysilane, 1 g of 3-mercaptopropyltrimethoxysilane, 1 g of silicone oil, and 0.5 g of modified curing accelerator into a high-speed mixer in sequence, and stir at 350 rpm for 13 min to obtain a premix;

[0038] (3) Transfer the premix to an extruder, conduct sufficient kneading and mixing, cool and pulverize to obtain a high-adhesion and low-moisture-absorption solid epoxy encapsulant; among them, the melting section temperature of the extruder is 120 °C, and the extrusion temperature is 90 °C.

[0039] Example 3: (1) Add 12 g of 4-hydroxymethyl-5-methyl-2-phenylimidazole, 7 g of triethylamine, and 100 ml of tetrahydrofuran into a three-necked round-bottom glass flask respectively. Subsequently, dissolve 3 g of 3,3',5,5'-tetrachlorobiphenyl in 100 ml of tetrahydrofuran, and dropwise add it to the three-necked round-bottom glass flask at 70 °C, continuously stir for 9 h. After the reaction is completed, perform rotary evaporation, rinse with deionized water, and then rinse with acetone. Repeat the operation 2 - 3 times, and then dry in a vacuum oven at 50 °C for 30 h to obtain a modified curing accelerator;

[0040] (2) Add 10 g of naphthalene-based epoxy resin, 10 g of XYLOK phenolic resin, 90 g of spherical silica with a particle size of 50 - 70 μm, 0.3 g of carbon black, 0.5 g of palm wax, 0.1 g of oxidized polyethylene wax, 1.5 g of anion scavenger, 0.3 g of 3-aminopropyltriethoxysilane, 3 g of methyltrimethoxysilane, 2 g of 3-mercaptopropyltrimethoxysilane, 1.5 g of silicone oil, and 0.5 g of modified curing accelerator into a high-speed mixer in sequence, and stir for 15 min at 400 rpm to obtain a premix.

[0041] (3) Transfer the premix to an extruder, conduct sufficient kneading and mixing, cool and pulverize to obtain a high-adhesion and low-moisture-absorption solid epoxy encapsulant; among them, the melting section temperature of the extruder is 130 °C, and the extrusion temperature is 100 °C.

[0042] Comparative Example 1: The difference from Example 2 is that 3,3',5,5'-tetrachlorobiphenyl is replaced with an equal amount of 3,4',5-trichlorobiphenyl, and the specific steps are as follows:

[0043] (1) Add 11.5 g of 4-hydroxymethyl-5-methyl-2-phenylimidazole, 6.5 g of triethylamine, and 90 ml of tetrahydrofuran into a three-necked round-bottom glass flask respectively. Subsequently, dissolve 2.95 g of 3,4',5-trichlorobiphenyl in 100 ml of tetrahydrofuran, and dropwise add it to the three-necked round-bottom glass flask at 65 °C, continuously stir for 9 h. After the reaction ends, perform rotary evaporation, rinse with deionized water, and then rinse with acetone. Repeat the operation 2 - 3 times, and then dry in a vacuum oven at 50 °C for 27 h to obtain a modified curing accelerator.

[0044] (2) Add 7 g of naphthalene-based epoxy resin, 6 g of XYLOK phenolic resin, 80 g of spherical silica with a particle size of 60 μm, 0.2 g of carbon black, 0.3 g of palm wax, 0.1 g of oxidized polyethylene wax, 1 g of anion scavenger, 0.2 g of 3-aminopropyltriethoxysilane, 2 g of methyltrimethoxysilane, 1 g of 3-mercaptopropyltrimethoxysilane, 1 g of silicone oil, and 0.5 g of modified curing accelerator into a high-speed mixer in sequence, and stir for 13 min at 350 rpm to obtain a premix.

[0045] (3) Transfer the premix to an extruder, conduct sufficient kneading and mixing, cool and pulverize to obtain a high-adhesion and low-moisture-absorption solid epoxy encapsulant; among them, the melting section temperature of the extruder is 120 °C, and the extrusion temperature is 90 °C.

[0046] Comparative Example 2: The difference from Example 2 is that 3,3',5,5'-tetrachlorobiphenyl is replaced with 3,5-dichlorobiphenyl, and the specific steps are as follows:

[0047] (1) 11.5 g of 4-hydroxymethyl-5-methyl-2-phenylimidazole, 6.5 g of triethylamine, and 90 ml of tetrahydrofuran were respectively added to a three-necked round-bottom glass flask. Subsequently, 2.95 g of 3,5-dichlorobiphenyl was dissolved in 100 ml of tetrahydrofuran and added dropwise to the three-necked round-bottom glass flask at 65 °C, with continuous stirring for 9 h. After the reaction ended, rotary evaporation was carried out, followed by rinsing with deionized water and then with acetone. The operation was repeated 2 - 3 times, and then it was dried in a vacuum oven at 50 °C for 27 h to obtain a modified curing accelerator;

[0048] (2) 7 g of naphthalene-based epoxy resin, 6 g of XYLOK phenolic resin, 80 g of 60 μm spherical silica, 0.2 g of carbon black, 0.3 g of palm wax, 0.1 g of oxidized polyethylene wax, 1 g of anion scavenger, 0.2 g of 3-aminopropyltriethoxysilane, 2 g of methyltrimethoxysilane, 1 g of 3-mercaptopropyltrimethoxysilane, 1 g of silicone oil, and 0.5 g of the modified curing accelerator were successively added to a high-speed mixer and stirred at 350 rpm for 13 min to obtain a premix;

[0049] (3) The premix was transferred to an extruder, subjected to sufficient kneading and mixing, cooled and pulverized to obtain a high-adhesion, low-moisture solid epoxy encapsulant; among them, the melting section temperature of the extruder was 120 °C and the extrusion temperature was 90 °C.

[0050] Comparative Example 3: The difference from Example 2 is that 3,3',5,5'-tetrachlorobiphenyl was replaced by 3-chlorobiphenyl. The specific steps are as follows:

[0051] (1) 11.5 g of 4-hydroxymethyl-5-methyl-2-phenylimidazole, 6.5 g of triethylamine, and 90 ml of tetrahydrofuran were respectively added to a three-necked round-bottom glass flask. Subsequently, 2.95 g of 3-chlorobiphenyl was dissolved in 100 ml of tetrahydrofuran and added dropwise to the three-necked round-bottom glass flask at 65 °C, with continuous stirring for 9 h. After the reaction ended, rotary evaporation was carried out, followed by rinsing with deionized water and then with acetone. The operation was repeated 2 - 3 times, and then it was dried in a vacuum oven at 50 °C for 27 h to obtain a modified curing accelerator;

[0052] (2) 7 g of naphthalene-based epoxy resin, 6 g of XYLOK phenolic resin, 80 g of 60 μm spherical silica, 0.2 g of carbon black, 0.3 g of palm wax, 0.1 g of oxidized polyethylene wax, 1 g of anion scavenger, 0.2 g of 3-aminopropyltriethoxysilane, 2 g of methyltrimethoxysilane, 1 g of 3-mercaptopropyltrimethoxysilane, 1 g of silicone oil, and 0.5 g of the modified curing accelerator were successively added to a high-speed mixer and stirred at 350 rpm for 13 min to obtain a premix;

[0053] (3) Transfer the premix to an extruder, carry out sufficient kneading and mixing, cool and pulverize to obtain a high-adhesion and low-moisture-absorption solid epoxy encapsulant; wherein, the melting section temperature of the extruder is 120 °C and the extrusion temperature is 90 °C.

[0054] Comparative Example 4: The difference from Example 2 is that the curing accelerator is 4-hydroxymethyl-5-methyl-2-phenylimidazole, and the specific steps are as follows:

[0055] (1) Add 7 g of naphthalene-based epoxy resin, 6 g of XYLOK phenolic resin, 80 g of 60-μm spherical silica, 0.2 g of carbon black, 0.3 g of palm wax, 0.1 g of oxidized polyethylene wax, 1 g of anion capturer, 0.2 g of 3-aminopropyltriethoxysilane, 2 g of methyltrimethoxysilane, 1 g of 3-mercaptopropyltrimethoxysilane, 1 g of silicone oil, and 0.5 g of 4-hydroxymethyl-5-methyl-2-phenylimidazole to a high-speed mixer in sequence, and stir at 350 rpm for 13 min to obtain a premix;

[0056] (2) Transfer the premix to an extruder, carry out sufficient kneading and mixing, cool and pulverize to obtain a high-adhesion and low-moisture-absorption solid epoxy encapsulant; wherein, the melting section temperature of the extruder is 120 °C and the extrusion temperature is 90 °C.

[0057] Comparative Example 5: The difference from Example 2 is that the curing accelerator is 0.1 g of 2MZ, and the specific steps are as follows:

[0058] (1) Add 7 g of naphthalene-based epoxy resin, 6 g of XYLOK phenolic resin, 80 g of 60-μm spherical silica, 0.2 g of carbon black, 0.3 g of palm wax, 0.1 g of oxidized polyethylene wax, 1 g of anion capturer, 0.2 g of 3-aminopropyltriethoxysilane, 2 g of methyltrimethoxysilane, 1 g of 3-mercaptopropyltrimethoxysilane, 1 g of silicone oil, and 0.1 g of 2MZ to a high-speed mixer in sequence, and stir at 350 rpm for 13 min to obtain a premix;

[0059] (2) Transfer the premix to an extruder, carry out sufficient kneading and mixing, cool and pulverize to obtain a high-adhesion and low-moisture-absorption solid epoxy encapsulant; wherein, the melting section temperature of the extruder is 120 °C and the extrusion temperature is 90 °C.

[0060] Comparative Example 6: The difference from Example 2 is that the curing accelerator is 0.1 g of 2MZ-A, and the specific steps are as follows:

[0061] (1) Add 7 g of naphthalene-based epoxy resin, 6 g of XYLOK phenolic resin, 80 g of 60-μm spherical silica, 0.2 g of carbon black, 0.3 g of palm wax, 0.1 g of oxidized polyethylene wax, 1 g of anion scavenger, 0.2 g of 3-aminopropyltriethoxysilane, 2 g of methyltrimethoxysilane, 1 g of 3-mercaptopropyltrimethoxysilane, 1 g of silicone oil, and 0.1 g of 2MZ-A into a high-speed mixer in sequence, and stir at 350 rpm for 13 min to obtain a premix;

[0062] (2) Transfer the premix to an extruder, conduct sufficient kneading and mixing, cool and crush to obtain a high-adhesion and low-moisture-absorption solid epoxy encapsulant; among them, the melting section temperature of the extruder is 120 °C and the extrusion temperature is 90 °C.

[0063] Comparative Example 7: The difference from Example 2 is that the curing accelerator is 0.1 g of TPP-BQ, and the specific steps are as follows:

[0064] (1) Add 7 g of naphthalene-based epoxy resin, 6 g of XYLOK phenolic resin, 80 g of 60-μm spherical silica, 0.2 g of carbon black, 0.3 g of palm wax, 0.1 g of oxidized polyethylene wax, 1 g of anion scavenger, 0.2 g of 3-aminopropyltriethoxysilane, 2 g of methyltrimethoxysilane, 1 g of 3-mercaptopropyltrimethoxysilane, 1 g of silicone oil, and 0.1 g of TPP-BQ into a high-speed mixer in sequence, and stir at 350 rpm for 13 min to obtain a premix;

[0065] (2) Transfer the premix to an extruder, conduct sufficient kneading and mixing, cool and crush to obtain a high-adhesion and low-moisture-absorption solid epoxy encapsulant; among them, the melting section temperature of the extruder is 120 °C and the extrusion temperature is 90 °C.

[0066] Comparative Example 8: The difference from Example 2 is that the curing accelerator is 0.1 g of TPTP, and the specific steps are as follows:

[0067] (1) Add 7 g of naphthalene-based epoxy resin, 6 g of XYLOK phenolic resin, 80 g of 60-μm spherical silica, 0.2 g of carbon black, 0.3 g of palm wax, 0.1 g of oxidized polyethylene wax, 1 g of anion scavenger, 0.2 g of 3-aminopropyltriethoxysilane, 2 g of methyltrimethoxysilane, 1 g of 3-mercaptopropyltrimethoxysilane, 1 g of silicone oil, and 0.1 g of TPTP into a high-speed mixer in sequence, and stir at 350 rpm for 13 min to obtain a premix;

[0068] (2) Transfer the premix to an extruder, conduct sufficient kneading and mixing, cool and crush to obtain a high-adhesion and low-moisture-absorption solid epoxy encapsulant; among them, the melting section temperature of the extruder is 120 °C and the extrusion temperature is 90 °C.

[0069] Performance Test

[0070] According to the standard of GB / T 40564-2021 "Determination Methods for Epoxy Molding Compounds for Electronic Packaging", the spiral flow length, gelation time and strength modulus of the epoxy resin compositions prepared in the examples and comparative examples were determined, and the test results are shown in the following table.

[0071] Water absorption rate: According to GB / T 40564-2021, the epoxy molding compounds prepared in the examples and comparative examples were tested by the autoclave test (PCT) at a temperature of 121 °C, a humidity of 100%, and an experiment time of 120 h under two standard atmospheres. The requirements for the sample size are diameter: 50 ± 1 mm, thickness: 3 ± 0.2 mm. Weigh the mass of the sample before and after the test, calculate the water absorption rate, and the test results are shown in the following table.

[0072] Glass transition temperature: The glass transition temperature of the epoxy molding compound was determined using a static thermomechanical analyzer (TMA) in the bending mode. The size of the test sample was 4 × 4 × 10 mm. Starting from a temperature of 25 °C, the heating rate was 5 °C / min, and the termination temperature was 220 °C. The test results are shown in the following table.

[0073] Adhesion: Using a molding press, under the conditions of a mold temperature of 175 ± 2 °C, an injection pressure of 7.0 ± 0.2 MPa, and a curing time of 120 s, the obtained epoxy molding compound was formed on the surfaces of different substrates, and a copper substrate and a silver-plated substrate were selected respectively;

[0074] Test operation: According to the SEMI G69-0996 standard, at a speed of 10 mm / min, a shear force was applied along the surface of the sample, and the maximum value before the molding compound was separated from the sample was tested. The number of each test sample was 10, and the average value of the 10 test results was taken as the adhesion test result of each example. The test results are shown in the following table.

[0075] Table 1 Performance Test Results of Examples and Comparative Examples 1-4

[0076]

[0077]

[0078] Table 2 Performance Test Results of Example 2 and Existing Products

[0079]

[0080] Data analysis shows that from the data obtained in the examples of Table 1, by adding a modified curing accelerator, under the same degree of curing, the obtained epoxy molding compound exhibits relatively excellent mechanical strength, adhesion, and extremely low water absorption. Moreover, due to the good latency of the modified curing accelerator, it shows a longer fluidity, enabling the epoxy molding compound of the present invention to exhibit better storage stability during actual use. From the data obtained in the examples of Table 2, it can be seen that the high-adhesion and low-moisture solid epoxy molding compound of the present invention, compared with the traditional epoxy molding compound, under the same degree of curing, the adhesion of the epoxy molding compound for encapsulation in Example 2 to the Cu / Ag substrate is improved most significantly, showing good flexural strength and low moisture absorption. And due to its good latency, under the same degree of curing, the addition amount of Example 2 is much more than that of the accelerators in Comparative Examples 5-8, and it shows good fluidity in the early stage, while the gelation time is basically the same as that of the traditional epoxy molding compound.

[0081] From the test results of Example 2 and Comparative Examples 1-4 in Table 1, it can be seen that different modifiers are used to modify 4-hydroxymethyl-5-methyl-2-phenylimidazole respectively, and then it is added as a curing accelerator to the raw materials, which greatly improves the storage stability, adhesion, and waterproof performance of the epoxy molding compound. And as the halogen groups contained in the modified substance increase, the effect becomes more obvious. This is mainly because as the halogen groups contained in the modified substance continue to increase, the high polarity of tetrachlorobiphenyl can significantly enhance the compatibility between the modified imidazole and the epoxy resin, reduce the interfacial defects, and at the same time, the interfacial combination can be strengthened through van der Waals forces and hydrogen bonds. And the high-substitution-degree biphenyl structure can form a dense cross-linked network during the curing process of the epoxy resin, reducing the porosity and free volume inside the material, thereby reducing the water penetration channels. In addition, a higher cross-linking density also provides higher strength. At the same time, the polyphenyl groups contained in the modified molecule itself are very likely to further promote a higher cross-linking density in large quantities. As the cross-linking density increases, the movement of polymer chains is restricted, which restricts the penetration and diffusion of water molecules, reduces the water adsorption, lowers the water absorption rate, and at the same time, endows higher strength.

[0082] Those of ordinary skill in the art should understand that: the discussion of any above embodiment is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A high-adhesion, low-moisture-absorption solid epoxy encapsulant, characterized in that, It includes the following raw materials in parts by weight: 4 - 10 parts of epoxy resin, 2 - 10 parts of phenolic resin, 70 - 90 parts of inorganic filler, 0.1 - 0.3 part of colorant, 0.2 - 0.6 part of mold release agent, 0.05 - 0.5 part of modified curing accelerator, 0.2 - 1.5 parts of ion scavenger, 0.1 - 0.3 part of coupling agent, 1 - 5 parts of adhesion promoter, 0.2 - 1.5 parts of stress improver; The preparation steps of the said modified curing accelerator are as follows: Add 4 - hydroxymethyl - 5 - methyl - 2 - phenylimidazole, triethylamine and tetrahydrofuran into a three - necked round - bottom glass flask respectively. Then dissolve 3,3',5,5' - tetrachlorobiphenyl in tetrahydrofuran and dropwise add it into the three - necked round - bottom glass flask at 60 - 70 °C, and continuously stir for 8 - 9 h. After the reaction is completed, perform rotary evaporation, washing and drying to obtain the modified curing accelerator; The dosage ratio of the said 4 - hydroxymethyl - 5 - methyl - 2 - phenylimidazole, triethylamine, tetrahydrofuran and 3,3',5,5' - tetrachlorobiphenyl is 11 - 12 g: 6 - 7 g: 180 - 200 ml: 2.9 - 3 g.

2. The high-adhesion, low-moisture-absorption solid epoxy encapsulant according to claim 1, characterized in that The said epoxy resin is one of o - cresol novolac epoxy resin, dicyclopentadiene epoxy resin, biphenyl epoxy resin, naphthol novolac epoxy resin, thioether epoxy resin or a mixture of several of them in any proportion; the said phenolic resin is one of phenol ether phenolic resin, o - methylphenolic resin, biphenol phenolic resin or a mixture of several of them in any proportion.

3. The high-adhesion and low-moisture-absorption solid epoxy encapsulant according to claim 1, wherein The said inorganic filler is one of crystalline silica, fused silica, spherical silica, alumina, talcum powder, kaolin, carbon fiber, glass fiber or a mixture of several of them in any proportion.

4. The high-adhesion and low-moisture-absorption solid epoxy encapsulant according to claim 1, wherein The said colorant is one of carbon black, titanium dioxide, aniline black; the said mold release agent is one of palm wax, montanic acid ester wax, polyethylene wax, oxidized polyethylene wax, polyamide wax.

5. The high-adhesion, low-moisture-absorption solid epoxy molding compound according to claim 1, characterized in that, The said ion scavenger is an anion scavenger; the said coupling agent is one or several of mercapto - type siloxane coupling agent, amino - type siloxane coupling agent or epoxy - type siloxane coupling agent.

6. The high-close-contact and low-moisture-absorption solid epoxy encapsulant according to claim 1, wherein The said adhesion promoter is one or several of methyltrimethoxysilane, 3 - mercaptopropyltrimethoxysilane, methyltriethoxysilane; the said stress improver is any one of silicone oil, silicone rubber, liquid rubber.

7. A preparation method of the high-adhesion and low-moisture-absorption solid epoxy encapsulant according to any one of claims 1-6, characterized in that, The specific steps are as follows: (1) Add the raw materials into a high - speed mixer and stir evenly to obtain a premix; (2) Transfer the premix to an extruder, conduct sufficient kneading and mixing, cool and pulverize to obtain a high - adhesion and low - moisture - absorption solid epoxy encapsulant.

8. The preparation method of the high-adhesion and low-moisture-absorption solid epoxy encapsulant according to claim 7, characterized in that, In step (1), the stirring speed of the said high - speed mixer is 300 - 400 rpm, and the stirring time is 10 - 15 min.

9. The preparation method of the high-adhesion and low-moisture-absorption solid epoxy encapsulant according to claim 7, wherein In step (2), the melting section temperature of the said extruder is 100 - 130 °C, and the extrusion temperature is 85 - 100 °C.

10. Application of the high-adhesion and low-moisture-absorption solid epoxy encapsulant according to any one of claims 1-6, characterized in that, It is applied to the fields of chip packaging, semiconductor packaging, electronic device or electromechanical product packaging protection.

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