High-strength epoxy molding compound for aluminum capacitor and preparation method therefor

Abstract

The present invention relates to the technical field of electronic packaging, and specifically relates to a high-strength epoxy molding compound for an aluminum capacitor and a preparation method therefor. Preparation raw materials at least comprise: 3-5 parts of an epoxy resin 1, 1-3 parts of an epoxy resin 2, 3-5 parts of a curing agent, 80-89 parts of silicon dioxide, 0.1-0.5 parts of a coupling agent, and 0.1-0.5 parts of a release agent, wherein the epoxy resin 1 has a structure represented by formula (1), the epoxy resin 2 has a structure represented by formula (2). The actual application requirements of increasingly thinner aluminum capacitor products are met, the product strength is high, thereby effectively avoiding the problem of cracking, and having high market application value.

Description

A high-strength epoxy molding compound for aluminum capacitors and its preparation method Technical Field

[0001] This invention relates to the field of electronic packaging technology, specifically to a high-strength epoxy molding compound for aluminum capacitors and its preparation method. Background Technology

[0002] As aluminum capacitors become smaller and thinner, cracking becomes increasingly serious. This is because aluminum capacitors contain liquid electrolytes, some of which evaporate at high temperatures. If the molding compound is not strong enough, cracking will occur. Chinese patent (authorization announcement number CN114276651B) discloses an epoxy resin composition suitable for low-pressure encapsulation and its preparation method. It mainly optimizes the epoxy resin, phenolic resin, silica powder filler, and reinforcing filler in the system to provide products with excellent crack resistance under low encapsulation pressure (30-40 kg). However, the obtained epoxy resin composition needs further improvement in two aspects: firstly, the spiral flow length needs to be further increased to meet actual injection molding requirements; secondly, the flexural strength of the product needs further improvement. Summary of the Invention

[0003] To address the aforementioned issues, this invention provides a high-strength epoxy encapsulant for aluminum capacitors, meeting the practical application needs of increasingly thinner aluminum capacitors. The product boasts high strength, effectively preventing cracking and possessing significant market application value.

[0004] This invention provides a high-strength epoxy molding compound for aluminum capacitors, comprising, by weight, at least the following raw materials: 3-5 parts epoxy resin 1, 1-3 parts epoxy resin 2, 3-5 parts curing agent, 80-89 parts silica, 0.1-0.5 parts coupling agent, and 0.1-0.5 parts release agent, wherein epoxy resin 1 has the structure shown in formula (1), and epoxy resin 2 has the structure shown in formula (2).

[0005] Equation (1):

[0006] Equation (2):

[0007] As a preferred technical solution, the curing agent includes at least the curing agent described in formula (3).

[0008] Equation (3): n = 2 - 10.

[0009] As a preferred technical solution, the curing agent further includes the curing agent described in formula (3).

[0010] Equation (4): n = 2 - 6.

[0011] As a preferred technical solution, the maximum particle size of the silica is 45 μm.

[0012] As a preferred technical solution, the silane coupling agent is selected from at least one of γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, and γ-aminopropyltriethoxysilane, preferably γ-glycidoxypropyltrimethoxysilane.

[0013] As a preferred technical solution, the release agent includes at least high-density oxidized polyethylene wax.

[0014] This invention utilizes an epoxy resin combination of 3-5 parts by weight of epoxy resin 1 and 1-3 parts by weight of epoxy resin 2, which has good compatibility with the curing agent in the system. This results in a product with suitable flowability, and the product cured in a short time exhibits high flexural strength and flexural modulus, avoiding cracking problems in thin aluminum capacitors during subsequent applications. Furthermore, this invention further shortens the curing time by controlling the curing agent to include at least the curing agent described in formula (3), avoiding mold sticking problems and meeting the application requirements of thin packaging.

[0015] Furthermore, by introducing silica with a maximum particle size of 45 μm into the system, and with the combined effect of silane coupling agent and high-density oxidized polyethylene wax in the system, the present invention provides a product with good flowability and high flexural strength, while having a relatively low coefficient of thermal expansion.

[0016] Another aspect of the present invention provides a method for preparing a high-strength epoxy molding compound for aluminum capacitors, comprising at least the following steps:

[0017] (1) Mix epoxy resin 1 and epoxy resin 2 and then pulverize them to obtain epoxy resin powder. Pulverize the curing agent to obtain curing agent powder.

[0018] (2) After mixing the raw materials other than epoxy resin and curing agent, add epoxy resin mixture and curing agent powder and mix to obtain a mixture;

[0019] (3) The epoxy molding compound is obtained by extruding, cooling and crushing the mixture.

[0020] As a preferred technical solution, in step (1), a resin pulverizer is used for pulverization, the pulverization temperature is ≤25℃, and the pulverization fineness is below 3.0mm.

[0021] As a preferred technical solution, in step (2), a high-speed mixer is used for stirring and mixing, with a stirring speed of 150-250 rpm and a time of 20-40 min, and the stirring and mixing temperature is controlled to be ≤25℃.

[0022] As a preferred technical solution, in step (3), the extrusion is carried out using a twin-screw extruder, and the extrusion temperature is controlled at 90-120℃;

[0023] As a preferred technical solution, the particle size of the epoxy molding compound in step (3) is 0.5-2.0 mm. Beneficial effects

[0024] 1. This invention provides a high-strength epoxy molding compound for aluminum capacitors, which meets the practical application needs of increasingly thinner aluminum capacitor products. The product has high strength, effectively avoids cracking problems, and has high market application value.

[0025] 2. This invention uses an epoxy resin combination of 3-5 parts by weight of epoxy resin 1 and 1-3 parts by weight of epoxy resin 2, which has good compatibility with the curing agent in the system, so that the provided product has suitable fluidity, and the product cured in a short time has high flexural strength and flexural modulus, thus avoiding the cracking problem of thin aluminum capacitors in subsequent applications.

[0026] 3. By controlling the curing agent to include at least the curing agent described in formula (3), the present invention further shortens the curing time, avoids the problem of sticking to the mold, and meets the application requirements of thin packaging.

[0027] 4. By introducing silica with a maximum particle size of 45 μm into the system, and with the combined effect of silane coupling agent and high-density oxidized polyethylene wax in the system, the present invention provides a product with good flowability and high flexural strength, while having a relatively low coefficient of thermal expansion. Detailed Implementation

[0028] Examples 1-4

[0029] Embodiments 1-4 of the present invention provide a high-strength epoxy molding compound for aluminum capacitors, the formulation of which is shown in Table 1 by weight.

[0030] Table 1

[0031] Embodiments 1-4 of the present invention provide a method for preparing a high-strength epoxy molding compound for aluminum capacitors, comprising the following steps:

[0032] (1) Mix epoxy resin 1 and epoxy resin 2 and then pulverize them to obtain epoxy resin powder. Pulverize the curing agent to obtain curing agent powder.

[0033] (2) After mixing the raw materials other than epoxy resin and curing agent, add epoxy resin mixture and curing agent powder and mix to obtain a mixture;

[0034] (3) The epoxy molding compound is obtained by extruding, cooling and crushing the mixture.

[0035] In step (1), a resin pulverizer is used for pulverization, with a pulverization temperature ≤25℃ and a pulverization fineness of 3.0 or less.

[0036] In step (2), a high-speed mixer is used for mixing. The mixing speed is 180 rpm and the time is 30 min. The mixing temperature is controlled to be ≤25℃.

[0037] In step (3), a twin-screw extruder is used for extrusion, and the extrusion temperature is controlled at 100°C.

[0038] The particle size of the epoxy molding compound in step (3) is 0.5-2.0 mm.

[0039] Performance testing

[0040] The epoxy molding compounds provided in Examples 1-4 were subjected to the performance tests shown in Table 2. The test methods are as follows, and the test results are shown in Table 2.

[0041] (1) Referring to GB / T40564-2021, the spiral flow length of the epoxy molding compound in the test example was measured.

[0042] (2) Referring to GB / T40564-2021, the curing time of the epoxy molding compound in the test example at 175°C was measured.

[0043] (3) Referring to GB / T40564-2021, test the flexural strength and flexural modulus of the epoxy molding compound in the example.

[0044] (4) Referring to GB / T40564-2021, the glass transition temperature of the epoxy molding compound in the example was tested.

[0045] (5) At a molding temperature of 175℃, the injection pressure is 6.86MPa (70kgf / cm²). 2 Under the conditions of ), the epoxy resin composition was added into the injection molding cylinder and compressed into a cylinder with a diameter of 5 mm and a height of 5 mm. After curing at 175°C for 6 hours, the coefficient of thermal expansion 1 (temperature range of 40 to 80 degrees Celsius) and the coefficient of thermal expansion 2 (200 to 240 degrees Celsius) were tested using PerkingElmer TMA4000.

[0046] (6) Referring to GB / T40564-2021, the molding shrinkage rate of the epoxy molding compound in the test example was tested.

[0047] Table 2

[0048] Analysis of the table above shows that the epoxy molding compound products provided in Example 1 have a more balanced flexural strength and flexural modulus, spiral flow length, curing time, glass transition temperature, coefficient of thermal expansion and molding shrinkage compared to Examples 2, 3 and 4, thus better meeting the needs of practical applications.

Claims

1. A high-strength epoxy molding compound for aluminum capacitors, characterized in that, The raw materials for its preparation, by weight, include at least: 3-5 parts of epoxy resin 1, 1-3 parts of epoxy resin 2, 3-5 parts of curing agent, 80-89 parts of silica, 0.1-0.5 parts of coupling agent, and 0.1-0.5 parts of release agent, wherein: epoxy resin 1 has the structure shown in formula (1), and epoxy resin 2 has the structure shown in formula (2), formula (1): Equation (2):

2. The high-strength epoxy encapsulant for aluminum capacitors according to claim 1, characterized in that, The curing agent includes at least the curing agent of formula (3), formula (3): n = 2 - 10.

3. The high-strength epoxy encapsulant for aluminum capacitors according to claim 1, characterized in that, The curing agent also includes the curing agent of formula (3), formula (4): n = 2 - 6.

4. The high-strength epoxy encapsulant for aluminum capacitors according to claim 1, characterized in that, The maximum particle size of the silica is 45 μm.

5. The high-strength epoxy encapsulant for aluminum capacitors according to claim 1, characterized in that, The silane coupling agent is selected from at least one of γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, and γ-aminopropyltriethoxysilane.

6. The high-strength epoxy encapsulant for aluminum capacitors according to claim 1, characterized in that, The release agent comprises at least high-density oxidized polyethylene wax.

7. A method for preparing a high-strength epoxy molding compound for aluminum capacitors according to any one of claims 1-6, characterized in that, At least the following steps are included: (1) Mix epoxy resin 1 and epoxy resin 2 and then pulverize them to obtain epoxy resin powder. Pulverize the curing agent to obtain curing agent powder. (2) After mixing the raw materials other than epoxy resin and curing agent, add epoxy resin mixture and curing agent powder and mix to obtain a mixture; (3) The epoxy molding compound is obtained by extruding, cooling and crushing the mixture.

8. The method for preparing the high-strength epoxy molding compound for aluminum capacitors according to claim 7, characterized in that, In step (1), a resin pulverizer is used for pulverization, with a pulverization temperature ≤25℃ and a pulverization fineness of less than 3.0mm.

9. The method for preparing high-strength epoxy molding compound for aluminum capacitors according to claim 7, characterized in that, In step (3), a twin-screw extruder is used for extrusion, and the extrusion temperature is controlled at 90-120℃.

10. The method for preparing the high-strength epoxy molding compound for aluminum capacitors according to claim 7, characterized in that, In step (3), the particle size of the epoxy molding compound is less than 3.0 mm.

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