JP2658406B2 - Manufacturing method of electrical equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an electric device, and more particularly, to a method for manufacturing an electric device having excellent thermal conductivity and greatly improved crack resistance.

[Conventional technology]

2. Description of the Related Art Conventionally, as a method of insulating an electric device, a potting method is known in which an electric device is set in a plastic or metal case, and a uniform mixture of an inorganic filler and a thermosetting resin composition is injected under normal pressure or reduced pressure to be cured. Have been.

However, in this method, there is a limit to the amount of the inorganic filler to be mixed from the viewpoint of workability, so that there is a disadvantage that the product price increases. In addition, when the thermosetting resin composition cures, volume shrinkage occurs, causing cracks in the cured product, easily causing peeling or cracking in the built-in electric components and case, and also having poor thermal conductivity, resulting in an electric current. There is a problem that the temperature of the device becomes high and the temperature used is limited. Furthermore, in order to perform the injection work after mixing the thermosetting resin composition and the inorganic filler and defoaming under vacuum, it is necessary to use a thermosetting resin composition having a long curing time, and therefore, after the injection. The curing time becomes longer, and there is a limit to the rationalization of the work process and energy saving.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for manufacturing an electric device which eliminates the drawbacks of the above-described conventional technology and has excellent curability, crack resistance and thermal conductivity.

[Means for solving the problem]

The present invention provides a thermosetting resin composition (B) after previously filling silica sand (A) having an AFS particle size of 7 to 75 into a case containing an electric component, an electronic component, or a circuit board.
Having a weight ratio of (A) to the silica sand (A):
(B) = 1.0: 0.4 to 0.2 is injected and cured, and relates to a method for manufacturing an electric device.

The silica sand (A) used in the present invention has an AFS particle size of 7 to 75. In the present invention, silica sand means natural silica sand having a SiO ₂ content of 90% by weight or more. AFS flow rate is measured according to JIS Z2602-1976. If the AFS particle size is less than 7, the filling amount per unit volume is small because the particles are coarse, and when the thermosetting resin composition is injected, voids between silica sands (filler) increase and cracks occur. Also, since the filler does not enter into the gaps between the parts or elements, the thermosetting resin composition is injected, and the linear expansion coefficient of the cured product when cured becomes non-uniform as a whole. Separation and cracks occur during the process. When the AFS particle size exceeds 75, the amount of filler per unit volume increases because the particles are fine particles, but the impregnating property of the thermosetting resin composition into the silica sand is deteriorated, and the thermosetting resin is partially removed. The composition is not impregnated, resulting in poor insulation between components or elements.

As the silica sand (A), for example, Pearl No. 4, Pearl No. 6, manufactured by Tochu Co., Ltd., and Mikawa Silica Sand V-3 are used.

The thermosetting resin composition (B) used in the present invention is not particularly limited, but a polyurethane resin composition, an epoxy resin composition, an unsaturated polyester resin composition, a silicone resin composition, and the like having excellent curability can be used. It is preferably used.

As the polyurethane resin composition, for example, a polyurethane resin obtained by a reaction between a polyhydroxy compound and an isocyanate compound is used. As the polyhydroxy compound, polyester polyol, polyether polyol, acrylic polyol, castor oil or its derivative, tall oil derivative and the like are used. Examples of the isocyanate compound include 2,4-tolylene diisocyanate, diphenylmethane 4,4'-diisocyanate, polymethylene polyphenyl polyisocyanate, and derivatives thereof.

As the epoxy resin composition, for example, a composition containing an epoxy resin having at least one epoxy group in a molecule and a curing agent is used. Examples of the curing agent include an aliphatic polyamine or a derivative thereof, an aromatic diamine or a derivative thereof, a bisspirocyclic diamine or a derivative thereof,
A mixture of an acid anhydride and a tertiary amine or an imidazole compound, a polyamide resin, an imidazole compound, an amine complex of boron fluoride, or the like is used.

As the unsaturated polyester resin composition, for example, an esterified product of an unsaturated polybasic acid or an anhydride thereof and a saturated polybasic acid or an anhydride thereof, and a glycol,
Those to which a crosslinking agent such as a vinyl monomer and a peroxide as a curing agent are added are used.

As the silicone resin composition, for example, a silicone polymer having a siloxane bond, an alkoxide resin, an acrylic resin, an epoxy resin, a polyester resin,
A resin obtained by copolymerizing or mixing a thermosetting resin such as a urethane resin with a curing agent such as a peroxide and a curing initiator such as a platinum compound is used.

The thermosetting resin composition is blended with a flexibilizing agent, a reactive diluent, a non-reactive diluent, a coupling agent and the like in order to improve properties, and a halogen in order to impart flame retardancy. A flame retardant such as a compound or a phosphorus compound can be blended.

The thermosetting resin composition (B) is used so that the weight ratio to the silica sand (A) 1.0 is in the range of 0.4 to 0.2. If the weight ratio is less than 0.2, the thermosetting resin composition cannot sufficiently impregnate the entire silica sand filled in the electric device, and an unimpregnated portion is formed at a lower portion, and insulation failure occurs between parts or elements. I do. Also, if the weight ratio exceeds 0.4, the thermosetting resin composition remains on the upper part of the electrical equipment, and the silica sand is settled, so that the thermal conductivity is poor, and the linear expansion coefficients of the upper and lower parts of the cured product are significantly different. Peeling or cracking occurs between components or elements during a heat cycle.

In the method for manufacturing an electric device according to the present invention, the thermosetting resin composition (B) is injected after the silica sand (A) is filled. For example, first, silica sand (A) having an AFS particle size in the range of 7 to 75 and previously dried at 100 ° C. for 1 hour or more is filled in a case containing electric components, electronic components, or a circuit board. Pre-dry at a temperature of at least ℃ and dehumidify sufficiently. Next, a predetermined amount of the thermosetting resin composition (B) is sufficiently mixed, and air bubbles entrained under a reduced pressure of 10 mmHg or less are removed. In order to improve the impregnating property and reduce the bubbles in the cured product, the mixture is injected in a vacuum chamber at a degree of vacuum of 5 to 20 mmHg. Thereafter, the pressure is returned to normal pressure, and the mixture is put into a furnace having a predetermined curing temperature to be cured.

The electric device obtained in this way is one in which the filler in the case is uniformly and sufficiently impregnated with the thermosetting resin composition, and the cured product has no air bubbles and is in close contact with components, elements, substrates, etc. The conventional potting method, that is, there is almost no difference between the impregnating property and the adhesion when the thermosetting resin composition and the filler are mixed in advance and then injected into the case and cured. is there. In the conventional potting method, the weight ratio of the thermosetting resin composition (B) to silica sand (A) 1.0 is limited to 0.4 in terms of viscosity and mixing workability at the time of mixing. According to the method of the present invention, since the amount of silica sand can be increased, the total cost can be reduced, and the curing shrinkage during curing is small, and the thermal conductivity of the cured product and the cracking property during a heat cycle are improved, The performance of electrical equipment is greatly improved.

Examples of the electric device in the present invention include a transformer or solenoid coil, a high-voltage transformer, an electromagnetic clutch, a ballast, a module, an igniter, a controller, a regulator, an airbag sensor, etc., in which a plastic or metal case contains electric and electronic components. Examples include electric equipment, electric equipment including a circuit board such as a ceramic substrate and a printed circuit board, and the like.

〔Example〕

Hereinafter, the present invention will be described with reference to examples. "Parts" in the following examples means parts by weight.

The AFS particle size of the silica sand is the percentage Wi (%) of each particle size measured according to JIS Z 2602-1976 "Testing method for particle size distribution of foundry sand". And AFS of each sieve size (mesh) shown in Table 1.
It was determined as follows from the particle size coefficient (Si).

Table 2 shows the AFS particle size of the silica sand used in Examples and Comparative Examples.

The model impregnation, model impregnation rate, sedimentation, thermal conductivity, crack resistance, and coefficient of linear expansion were measured as follows.

(1) Model impregnation rate: A silica beaker is charged into a beaker made of polyethylene having a diameter of 50 mm while vibrating while vibrating, and then weighed to obtain the weight (Wo g) of the silica sand. Next, the thermosetting resin composition was injected, and the mixture was left under reduced pressure of 10 mmHg for 10 minutes.
Cure in 3 hours. Then, the cured product was taken out from the polyethylene beaker, the weight (W ₁ g) of the silica sand separated from the cured product without being impregnated with the lower thermosetting resin composition was determined, and the model impregnation was calculated from the following equation.

The model impregnation rate is a value obtained by impregnating the filler with the thermosetting resin composition. If the amount of the filler in the non-impregnated portion is small, the model impregnation rate is high, indicating that the impregnating property is excellent.

(3) Model sedimentation: Sand silica is filled into a polyethylene beaker having a diameter of 50 mm while vibrating. Next, the thermosetting resin composition was injected, left under a reduced pressure of 10 mmHg for 10 minutes, cured at 80 ° C. for 3 hours under normal pressure, and the appearance was observed as follows.

：: no separation of the filler, no sedimentation ×: separation of the filler, sedimentation (4) Thermal conductivity: 50 m in diameter cast by the same method as (3)
m, a disk-shaped test piece with a thickness of 10 mm was prepared, and the thermal conductivity (cal / cm · sec.
° C).

(5) Crack resistance: A test piece was prepared by casting in the same manner as in (3), and the test piece was tested according to the crack resistance test of JIS C 2105 “Testing method for solvent-free liquid resin for electrical insulation”.
The number of crack test pieces was five, and a predetermined cooling / heating cycle was performed. The presence or absence of cracks was confirmed for each cycle, and the number of cycles in which cracks occurred first was described.

(6) Coefficient of linear expansion: 5 mm using a test piece for measuring thermal conductivity
A test piece of × 5 mm × 2 mm was cut out, and the coefficient of linear expansion (° C. ⁻¹ ) was determined using a TMA thermophysical tester (manufactured by Rigaku Corporation).

Examples 1 to 3 A reactive diluent (DY-02 manufactured by Chise Nagase) was added to 80 parts of a bisphenol A type epoxy resin (Epicoat 828 manufactured by Yuka Shell Co., Ltd.).
2, an epoxy resin (a) mixed with 20 parts of a diglycidyl ether-based diluent), 100 parts of methyltetrahydrophthalic anhydride (HN-2200 manufactured by Hitachi Chemical Co., Ltd.) and 2-ethyl-4
-Methyl imidazole (Curesol 2E4M manufactured by Shikoku Chemicals)
Z) a curing agent (b) in which 2 parts are mixed, and (a)
/ (B) = 100/85 to obtain an epoxy resin composition (B-1).

100 parts of this epoxy resin composition (B-1) were mixed with silica sands (A-1), (A-2) and (A) shown in Table 2.
A test piece was prepared using 350 parts of each of -3), and the thermal conductivity, the coefficient of linear expansion, and the crack resistance were measured in accordance with the above test method, and the model impregnation rate and the model settling property were measured by a predetermined method. . The results are shown in Table 3. As a result, the model impregnating property and the model settling property in each silica sand were good, the thermal conductivity was high, the linear expansion coefficient was small, and the crack resistance was good.

Example 4 Bisphenol A type epoxy resin (manufactured by Asahi Denka Kogyo Co., Ltd.
Adeka Resin EP-4000) 80 parts of flexible agent (Adeka Resin)
ED-506) An epoxy resin (c) mixed with 20 parts and a modified aromatic polyamine (ADEKA EH-531, curing agent) (d) were obtained by weight ratio (c) / (d) = 100/40. The resulting mixture was mixed to obtain an epoxy resin composition (B-2).

Various characteristics were measured in the same manner as in Example 1 using 100 parts of this epoxy resin composition (B-2) and 350 parts of silica sand (A-1). The results are shown in Table 3. As a result, the model impregnating property and the model settling property in each silica sand were good, the thermal conductivity was high, the linear expansion coefficient was small, and the crack resistance was good.

Example 5 Castor oil (e) as a hydroxy compound and polymethylene polyphenyl polyisocyanate (Nippon Polyurethane MR-100) as an isocyanate compound (f),
The polyurethane resin composition (B-3) was obtained by mixing so that (e) / (f) = 100/34 in weight ratio.

Various characteristics were measured in the same manner as in Example 1 using 100 parts of this polyurethane resin composition (B-3) and 350 parts of silica sand (A-1). The results are shown in Table 3,
The model impregnating property and the model settling property in each silica sand were good, the thermal conductivity was high, the coefficient of linear expansion was small, and the crack resistance was good.

Example 6 To an ester compound obtained by reacting 98 parts of maleic anhydride, 148 parts of phthalic anhydride and 223 parts of diethylene glycol until the acid value becomes 50 at 190 to 200 ° C., styrene monomer 152 was added.
To about 20 poise of unsaturated polyester (g). The unsaturated polyester (g) and methyl ethyl ketone peroxide (h) were prepared by weight ratio of (g) / (h)
= 100/1 to obtain an unsaturated polyester resin composition (B-4).

Example 1 using 100 parts of this unsaturated polyester resin composition (B-4) and 350 parts of silica sand (A-1)
Various characteristics were measured in the same manner as described above. The results are shown in Table 3. As a result, the model impregnating property and the model settling property in each silica sand were good, the thermal conductivity was high, the linear expansion coefficient was small, and the crack resistance was good.

Example 7 Silicone resin manufactured by Shin-Etsu Chemical Co., Ltd., RTV rubber KE-106 (i)
And CRT-RG (manufactured by Shin-Etsu Chemical Co., Ltd.) (j) as a catalyst were mixed at a weight ratio of (i) / (j) = 100/1 to obtain a silicone resin composition (B-5). .

Various characteristics were measured in the same manner as in Example 1 using 100 parts of the silicone resin composition (B-5) and 350 parts of silica sand (A-1). The results are shown in Table 3. As a result, the model impregnating property and the model settling property in each silica sand were good, the thermal conductivity was high, the linear expansion coefficient was small, and the crack resistance was good.

Comparative Example 1 An epoxy resin composition (B) obtained in the same manner as in Example 1
-1) 100 units and silica sand with AFS particle size of 80.1 (A
-4) Various characteristics were measured in the same manner as in Example 1 using 350 parts. The results are shown in Table 3. As a result, the impregnating property of the model was poor, and the resin-unimpregnated portion was found in the silica sand, and the crack resistance was poor.

Comparative Example 2 Same as Example 1 using 100 parts of the polyurethane resin composition (B-3) obtained in the same manner as in Example 3 and 350 parts of silica sand (A-5) having an AFS particle size of 6.1. And various characteristics were measured. The results are shown in Table 3. As a result, the model sedimentation property was poor, separation and sedimentation of the filler were observed, and the crack resistance was poor.

Comparative Example 3 An epoxy resin composition (B) obtained in the same manner as in Example 1
-1) The ratio of 150 parts of silica sand (A-1) to 100 parts (that is, (B-1) to (A-1)) is 0.6.
Various characteristics were measured in the same manner as in Example 1 using 7). The results are shown in Table 3. As a result, the model sedimentation was poor, separation and sedimentation of the filler were observed, the coefficient of linear expansion was large, and the crack resistance was poor.

Comparative Example 4 An epoxy resin composition (B) obtained in the same manner as in Example 1
-1) Various properties were measured in the same manner as in Example 1 using 100 parts and 550 parts of silica sand (A-1) (that is, the ratio of (B-1) to (A-1) was 0.18). did. The results are shown in Table 3. The impregnating property of the model was poor, and unimpregnated portions of the resin were found in the silica sand.

Comparative Example 5 An epoxy resin composition (B) obtained in the same manner as in Example 2
-2) 200 parts of silica sand (A-1) is blended with 100 parts,
The mixture was stirred at room temperature using a stirrer until the silica sand (A-1) was sufficiently mixed with the epoxy resin composition (B-2).
Next, various characteristics were measured in the same manner as in Example 1 using the mixture. The results are shown in Table 3, which showed that the thermal conductivity was low, the coefficient of linear expansion was large, and the crack resistance was poor.

[Effects of the Invention] According to the method for manufacturing an electric device of the present invention, it is possible to obtain an electric device having excellent thermal conductivity and excellent crack resistance, and material costs and process costs as compared with conventional methods. Can be significantly reduced.

Continuation of front page (72) Inventor Yasunori Okada 4-3-1-1, Higashicho, Hitachi City, Ibaraki Pref. Hitachi Chemical Co., Ltd. Yamazaki Factory (56) References JP-A-58-29858 (JP, A) JP-A-63 −297436 (JP, A)

Claims (1)

(57) [Claims] 1. A thermosetting resin composition (B) after previously filling silica sand (A) having an AFS particle size of 7 to 75 into a case containing an electric component, an electronic component or a circuit board.
Having a weight ratio of (A) to the silica sand (A):
(B) = 1.0: A method for manufacturing an electric device, wherein the injection is performed so as to satisfy 0.4 to 0.2 and the mixture is cured.