JP2000327810A - Preparation of prepreg and prepreg prepared by the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a prepreg which does not cause uneven coating by impreg nating a fiber base material with a resin varnish containing an inorganic filler under mixing by agitation and/or circulation and/or circulatory mixing. SOLUTION: A prepreg is obtained by impregnating a fiber base material with a resin varnish containing an inorganic filler selected among alumina, silica, aluminum hydroxide, aluminum silicate and the like under agitating- mixing and/or circulatory mixing followed by drying. The ratio of the inorganic filler to the resin in the prepreg is almost equal to that in the resin varnish containing the inorganic filler and almost unchanged during coating for many hours and does not cause uneven coating or the like. As thermosetting resins employed for the resin varnish, there can be mentioned epoxy resins, phenol resins and the like, and if necessary, a curing agent, a curing accelerator, a flame-retardant, a solvent and the like are compounded. As the fiber base material, there can be exemplified paper, glass cloths, glass nonwoven fabrics, glass mats, synthetic fiber fabrics, synthetic fiber nonwoven fabrics, paper-glass mixed paper and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a prepreg.

[0002]

2. Description of the Related Art A prepreg is formed by laminating a plurality of fiber base materials, heating and pressurizing them to form a laminate, and forming a laminate between an inner layer circuit board and an outer layer board or an outer layer copper foil of a copper-clad laminate for a multilayer printed wiring board. It is used for bonding and bonding between inner circuit boards.

[0003] The prepreg is impregnated by impregnating a fiber base material into a resin varnish, and is then pulled up from the resin varnish.
The resin is adjusted by a resin adjusting bar or the like, and heated in a drying oven to remove the solvent in the resin varnish and semi-cured to produce the resin.

[0004] In recent years, printed wiring boards used inside electronic devices have recently been required to have various characteristics with the spread of various electronic devices, and in order to satisfy the required characteristics. It is not uncommon for printed wiring board materials to contain inorganic fillers. The purpose of blending the inorganic filler in the printed wiring board material is to obtain a material having both the excellent properties of the inorganic filler and the excellent properties of the resin. It becomes important to obtain necessary characteristics.

[0005] However, when a resin varnish containing an inorganic filler is impregnated into a fiber base material, due to the difference in specific gravity between the inorganic filler and the resin, an inorganic material having a high specific gravity is contained in the resin varnish during the production of the prepreg. The filler settles, and separation of the inorganic filler and the resin occurs. When the separation of the inorganic filler and the resin occurs in the resin varnish, the ratio of the inorganic filler and the resin in the manufactured prepreg also changes, and the amount of the inorganic filler contained in the manufactured prepreg is not constant. In addition, there arises a problem that stable production cannot be performed and required characteristics are not exhibited. In general, the separation of the inorganic filler and the resin is likely to occur when the viscosity of the resin varnish containing the inorganic filler is low. A prepreg is produced by impregnating a resin base material with a resin varnish while keeping the viscosity of the varnish high.

[0006]

However, when the viscosity of the resin varnish is high, the impregnating property of the resin varnish into the fiber base material is reduced, and the occurrence of uneven prepreg coating and the occurrence of voids are observed. As a result, inconveniences such as deterioration of moldability will occur, and if the viscosity of the resin varnish containing an inorganic filler is reduced as a countermeasure, the resin varnish is impregnated into the fiber base material to produce a prepreg. In the meantime, the inorganic filler settles, and the inorganic filler and the resin are separated, the amount of the inorganic filler contained in the manufactured prepreg is not constant, and stable production cannot be performed. Does not appear.

[0007] An object of the present invention is to provide a method for producing a prepreg free of uneven coating.

[0008]

The method for producing a prepreg of the present invention comprises impregnating a fiber base material with a resin varnish containing an inorganic filler in a resin impregnation section while stirring and / or circulating and mixing. Features.

[0009] The prepreg of the present invention is characterized in that a resin varnish containing an inorganic filler is impregnated into a fiber base material while stirring and / or circulating and mixing in a resin impregnated portion.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The fiber base used in the present invention may be a conventionally known fiber base, and is not particularly limited. For example, paper, glass cloth, glass nonwoven fabric, glass mat, synthetic fiber cloth, synthetic fiber nonwoven cloth, paper
Glass mixed paper and the like can be mentioned.

The thermosetting resin used for the resin varnish is as follows:
A conventionally known thermosetting resin can be used, and there is no particular limitation. For example, an epoxy resin, a phenol resin, an unsaturated polyester resin, a polyimide resin and the like can be mentioned.

As the inorganic filler compounded in the resin varnish, a conventionally known inorganic filler can be used, and there is no particular limitation. For example, alumina, silica, aluminum hydroxide,
Examples include aluminum silicate and mica. An inorganic filler is blended with these thermosetting resins, and if necessary, a curing agent, a curing accelerator, a flame retardant, a solvent, and the like are blended, and the fiber base material is impregnated as a resin varnish.

The resin varnish impregnation method can be carried out by installing a stirring device or a circulation device in a conventional resin varnish impregnation device, or by installing both a stirring device and a circulation device. The stirring device and the circulation device are not particularly limited, but desirably have a stirring ability and a circulation ability that can prevent the sedimentation of the inorganic filler.

Either stirring mixing or circulating mixing may be carried out, but it is preferable to use them together, and there is no particular limitation on the stirring method and circulation method.

After passing through the resin varnish in the resin varnish impregnated portion, the fiber base material is sent to a drying step and dried to be prepreg. The conditions of this step may be the same as those in the related art, and are not particularly limited. The ratio of the inorganic filler to the resin in the obtained prepreg is almost the same as that of the resin varnish containing the inorganic filler, and the ratio is substantially constant even after long-time coating, and there is no occurrence of uneven coating. Therefore, it is particularly useful for keeping the effect of blending the inorganic filler constant.

[0016]

Example 1 90 parts by weight of a brominated epoxy resin Epicoat 5040B80 (trade name, manufactured by Yuka Shell Epoxy Co., Ltd.), cresol novolac type epoxy resin N-673-80M
(Product name, manufactured by Dainippon Ink and Chemicals, Inc.) 10 parts by weight, 1.5 parts by weight of dicyandiamide and 2-ethyl-
A mixture of 0.05 parts by weight of 4-methylimidazole and 50 parts by weight of methyl ethyl ketone was mixed with 80 parts by weight of silica for the purpose of improving moisture absorption solder heat resistance, and the solid content was 69.6.
A weight percent resin varnish was prepared. As the fiber base material, a glass cloth (MIL standard: 7629 type) having a basis weight of 210 g / m ² , a width of 1050 mm, and a thickness of 0.2 mm was used. As shown in FIG. Both of the circulating mixers are arranged to perform both stirring mixing and circulating mixing to adjust the resin solid content (including inorganic filler) of the prepreg to 60%, and at a speed of 9 m / min in a 170 ° C. drying tower To make a prepreg. The viscosity of the resin varnish is about 70 cP or more in consideration of the occurrence of uneven coating and the like.
80 cP.

Example 2 In the resin-impregnated part, only the stirring device was used, and
A prepreg was prepared in the same manner as described above.

Comparative Example 1 A prepreg was prepared in the same manner as in Example 1 except that neither the stirring mixing device nor the circulation mixing device was used in the resin impregnated section.

Comparative Example 2 90 parts by weight of a brominated epoxy resin Epicoat 5040B80 (trade name, manufactured by Yuka Shell Epoxy Co., Ltd.), cresol novolak type epoxy resin N-673-80M
(Manufactured by Dainippon Ink and Chemicals, Inc., trade name) 10 parts by weight, dicyandiamide 1.5 parts by weight, 2-ethyl-4-
0.05 parts by weight of methyl imidazole and 20 parts by weight of methyl ethyl ketone were mixed, and 80 parts by weight of silica was blended for the purpose of improving moisture absorption solder heat resistance to prepare a resin varnish having a solid content of 80.0% by weight. As a fiber base material, basis weight 21
Using a glass cloth (MIL standard: 7629 type) having a thickness of 0 g / m ² , a width of 1050 mm, and a thickness of 0.2 mm, in the resin impregnated section, without using a stirring and mixing device or a circulating mixing device, the resin solid content (inorganic 6 including filler)
The prepreg was adjusted to 0% and passed through a drying tower at 170 ° C. at a speed of 9 m / min to produce a prepreg. The viscosity of the resin varnish is approximately 200 cP-250 in consideration of the sedimentation of the inorganic filler.
cP.

The weight ratio of the resin and the inorganic filler of the prepregs prepared in Examples and Comparative Examples was determined, and the presence or absence of occurrence of uneven coating of the prepreg was visually checked. Table 1 shows the results. The weight ratio between the resin and the inorganic filler was determined from the weight loss rate when the obtained prepreg was heated at 600 ° C. for 1 hour in an electric furnace. The weight ratio between the resin and the inorganic filler was determined by the equation (3).
This is the average value of ten mx 100 mm size sheets. A: Weight of prepreg-weight of prepreg after heating B: weight of prepreg x prepreg solids-A Weight ratio of prepreg resin and inorganic filler: B / A

Further, three prepregs prepared as described above were stacked, and a copper foil having a thickness of 35 μm was stacked on both surfaces thereof at a temperature of 170 μm.
A double-sided copper-clad laminate was prepared by heating and pressing at 90 ° C. and a pressure of 2.5 MPa for 90 minutes. Then, the entire surface of the copper foil is etched, cut into a size of 50 mm × 50 mm, and subjected to a constant-temperature and constant-humidity treatment at 40 ° C. and 90% for 192 hours. The sex was evaluated. The number of evaluation sheets was three, and the results are also shown in Table 1.

[0022]

[Table 1] Note) Ratio of inorganic filler to resin in resin varnish, theoretically 0.
981. Heat resistance evaluation criteria ○: No abnormality, Δ: Mesling occurred, ×: Blistering occurred

From Table 1, it can be seen that the prepregs prepared in Examples 1 and 2 showed a small difference in the mixing ratio of the inorganic filler and the resin even after long-time coating compared to Comparative Example 1, and contained in the prepreg. The ratio of the inorganic filler to be almost constant,
It is shown that the effect of the inorganic filler compounded for the purpose of improving the heat resistance is more remarkable as compared with Comparative Example 1.
In Comparative Example 2, although the difference in the blending ratio between the inorganic filler and the resin contained in the prepreg was smaller than that in Comparative Example 1, it was larger than that in Examples 1 and 2, and uneven coating occurred. And the heat resistance is reduced.

[0024]

As described above, according to the present invention, it is possible to provide a method for producing a prepreg having a stable inorganic filler content without causing uneven coating.

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Claims (2)

[Claims] 1. A method for producing a prepreg, comprising impregnating a fiber base material with a resin varnish containing an inorganic filler while stirring and / or circulating and mixing. 2. A prepreg, wherein a resin varnish containing an inorganic filler is impregnated into a fiber base material while stirring and / or circulating and mixing.