JPH10287755A - Production of prepreg sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a prepreg for thin laminates excellent in electrical insulating properties by dispersing an uncured thermosetting resin powder having a specified particle size or lower in water, heating the dispersion to a temp. in a specified range to cause the powder to agglomerate, and forming the resultant agglomerates together with substrate fibers into paper in wet. SOLUTION: The particle size of the resin powder is 300 μm or lower. The dispersion is heated to 30 deg.C or higher but not higher than the m.p. of the powder. The resin is an epoxy resin, a phenol resin, etc., and its level of degree of curing is the A- or B-stage and its gel time at 150 deg.C is 30 sec or longer. A suitable amt. of the resin used is 40-90 pts.wt. based on 100 pts.wt. substrate fibers. Any kind of electrically insulating fibers can be used without any specific limitation, an example being wood pulp. Chapped strands or wooly fibers having lengths of 3-25 mm and thicknesses of 2-9 μm are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a prepreg sheet for an electric insulating material such as a printed wiring board.

[0002]

2. Description of the Related Art With the miniaturization and thinning of electric equipment, printed wiring boards have been multi-layered and thinned.
The necessity of forming an insulating layer of 0 μm or less tends to increase. Conventionally, various printed wiring boards, such as kraft paper, glass paper, and glass cloth, are impregnated with thermosetting resins such as phenolic resin and epoxy resin, and dried.
A method of preparing a prepreg sheet in a B-stage state and hot-pressing the same together with a copper foil to manufacture the prepreg sheet is generally performed.
However, when a prepreg sheet that forms an insulating layer of 100 μm or less after molding is manufactured by a conventional impregnation method, since the strength of the base sheet is very weak, a meticulous tension control is performed when impregnating the resin varnish, and In addition, the production efficiency is significantly reduced due to production at a low impregnation speed.

In order to cope with thinning of an insulating layer, Japanese Patent Application Laid-Open Nos. 8-109272, 3-3431, and 2-9
5847, a method of internally adding uncured thermosetting resin powder to various fibers as disclosed in Japanese Patent Application Laid-Open No. 62-41399 and performing wet papermaking without impregnation step has been proposed. Was. However, in the method disclosed in JP-A-8-109272, Japanese Patent Publication No. 3-3431, and Japanese Patent Publication No. 2-95847, since the means for fixing the resin powder to the base fiber is not specified, the resin yield is low. As a result, a large amount of resin powder is discharged out of the system, which adversely affects not only the production cost but also the environment.

As a method for solving the problem of the yield, a method in which various polymer coagulants are used in combination as disclosed in JP-A-62-41399 is usually used. When the prepreg sheet for the insulating layer of the high multilayer printed wiring board is manufactured by using the prepreg sheet, the long-term electrical insulation reliability seen in the electrolytic corrosion phenomenon is significantly reduced, and the prepreg sheet satisfying the characteristics of the printed wiring board is obtained. Did not get.

[0005]

DISCLOSURE OF THE INVENTION The present invention is a papermaking method suitable for the production of thin prepregs, which reduces the resin powder falling off from the papermaking wire, which has been a problem, without reducing the electrical insulation during sheeting. It is another object of the present invention to provide a manufacturing method for increasing the yield of resin powder.

[0006]

In order to solve the above problems, the present invention employs the following manufacturing method. That is, the present invention is to disperse an uncured thermosetting resin powder having a particle diameter of 300 μm or less in water, and then heat the dispersion to 30 ° C. or more and a resin softening temperature or less to form a resin powder aggregate. The present invention also relates to a method for producing a prepreg sheet, which comprises wet-making the aggregate with a base fiber.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, the resin powder to be internally added is 3
After dispersing in water at 0 ° C or lower, heat treatment is performed to soften the surface of the resin powder, form agglomerates by bonding the particles appropriately, and then perform wet papermaking with the base fibers to generate electrolytic corrosion. The present invention is characterized in that the yield of resin powder is improved without using a fixing agent which causes a problem.

The thermosetting resin powder used in the present invention is an uncured thermosetting resin such as an epoxy resin, a phenol resin, a melamine resin and a polyimide resin, and has a particle diameter of 30%.
It is a resin powder of 0 μm or less. As the level of the degree of curing of the uncured thermosetting resin shown here, a resin powder of A stage or B stage and a gel time at 150 ° C. in JIS-K-6910 of 30 seconds or more is targeted.

Although it depends on the method of press-molding a printed wiring board, if the gel time is 30 seconds or less, a fading phenomenon occurs, and the gel time is not suitable as a prepreg. The optimum resin dispersion temperature for forming flocs depends on the type of resin and the degree of polymerization, but aggregation is performed in the range of 30 ° C to the resin softening temperature. If the dispersion temperature is raised beyond the softening temperature, the resin will be in a lump and a uniform aggregate cannot be obtained. The softening temperature shown here is evaluated based on the start temperature of an endothermic peak that appears when the resin is melted by DSC (differential calorimetry). The holding time depends on the water temperature, but is preferably at least 5 minutes or more and 30 minutes or more.

The amount of the resin powder to be added is 40 to 90 parts by weight, preferably 50 to 80 parts by weight, based on 100 parts by weight of the base fiber.
A range of parts by weight is appropriate. If the amount of the resin is less than 40 parts by weight, the flow of the resin becomes insufficient, so that the fading phenomenon occurs as in the case where the gel time is short. On the other hand, if it exceeds 90 parts by weight, the base fiber is insufficient, so that the paper strength is insufficient and the paper cannot be made.

The base fiber used in the present invention is not particularly limited as long as it has electrical insulation properties.
For example, any of wood pulp, glass fiber, aramid fiber, polyester fiber, polyimide fiber and the like can be used. Although the fiber length and fiber diameter of the base fiber are not particularly limited, in order to obtain a sheet with good formation by a wet papermaking method, usually, the fiber length is 3 mm to 25 mm, and the fiber diameter is 2 μm to 9 μm.
Chopped strands in the range of μm or wool fibers are used. Further, in order to improve the dispersion of the base fibers, it is also possible to add various dispersants as needed to make paper.

Various coupling agents and binders for chemically bonding the fiber and the thermosetting resin, and flame-retardants, plasticizers, pigments, and the like are added as necessary to impart various functions. Is also possible.

When the sheet is formed by a wet papermaking method, a sheet having a uniform formation can be obtained. The paper machine to be manufactured is not particularly limited. For example, a fourdrinier paper machine, a circular net paper machine, an inclined short net paper machine, and the like can be manufactured.

[0014]

The present invention will be described in more detail with reference to the following examples.

<Example 1> A phenolic resin (Bellpearl S-890, manufactured by Kanebo Co., Ltd., average particle diameter 20 μm, softening temperature 50 ° C.) was used as a resin powder, and the dispersion concentration in water at a water temperature of 10 ° C. was 0.5. % By weight, and after the dispersion, the water temperature is 45 ° C.
And kept for 30 minutes to form aggregates. Glass fiber as base fiber (UP
Using a DE1 / 4ZA508 fiber diameter of 6 μm and a fiber length of 6 mm), a polyethylene glycol distearate (Kao Co., Ltd. Emanon 3299) was added as a dispersant at 0.5% by weight of the fiber to prepare a fiber dispersion. Then, a slurry of resin and fiber was mixed with 70 parts by weight of phenol resin powder and glass fiber 3
The mixture was mixed at a ratio of 0 parts by weight, and wet papermaking was performed so that the basis weight was 75 g / m ² .

After forming the wet sheet, γ-glycidoxypropyltrimethoxysilane (A-187, manufactured by Nippon Unicar Co., Ltd.) was added as a coupling agent at 1% to the sheet, and then heated and dried at 120 ° C. to prepare a prepreg sheet. I got Ten sheets of the obtained prepreg sheets were stacked, and 18 μm copper foil was arranged on both surface layers.
gf / cm ² under pressure and heat to make the insulating layer thickness 0.4t
A copper-clad laminate was obtained. Using this copper-clad laminate, the insulation resistance was measured, and the electrolytic corrosion was measured. Table 1 shows the results.
Shown in

<Comparative Example 1> A paper laminate was prepared in the same manner as in Example 1 except that the resin powder slurry in Example 1 was not heated. The resin yield at this time was 10%, and the laminate was prepared by applying heat and pressure, but it could not be formed due to fading.

<Comparative Example 2> In Example 1, the resin powder slurry was dispersed together with the glass fiber without heating, and the cationic polymer coagulant Crifix CP-633 (manufactured by Kurita Kogyo Co., Ltd.) was added to the resin. Paper was made by adding 0.3 parts by weight to the total of 100 parts by weight of the powder and the glass fiber to fix the resin to the fiber. The obtained prepreg sheet was laminated and pressed in the same manner as in Example 1 to produce a laminated board, which was evaluated in the same manner as in Example. Table 1 shows the results.

<Comparative Example 3> The resin powder slurry of Example 1 was heated to 60 ° C to form an agglomerate, but it could not be formed into a lump having a diameter of 1 cm or more.

Example 2 As a resin powder, an epoxy resin powder was dispersed at a water temperature of 20.degree.
The mixture was heated to ℃ and kept for 30 minutes to form an aggregate. The epoxy resin used at this time was 100 parts by weight of a bisphenol novolak type epoxy resin (Epiclon N-865: manufactured by Dainippon Ink and Chemicals), and a phenol novolak resin (TD-2131: manufactured by Dainippon Ink and Chemicals) as a curing agent 35 Parts by weight, and a resin obtained by melt-mixing 0.15 parts by weight of phenylimidazole as a curing accelerator with an average particle diameter of 50 parts.
Resin powder that was dry-pulverized to μm was used. (Average particle size: 50 μm, softening temperature: 40 ° C.) Lamination was made in the same manner as in Example 1 for sheeting and lamination.
The same was done. Table 1 shows the results.

[0021]

[Table 1]

[0022]

According to the present invention, the resin powder slurry to be internally added is dispersed in heated water to form an aggregate, and then wet papermaking is performed together with the base fiber to obtain a sheet having a thickness of 100 μm, which is excellent in electrical insulation. The following thin prepregs for laminated boards can be easily manufactured.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 63/02 B29C 67/14 G // B29L 9:00

Claims (1)

[Claims] After dispersing an uncured thermosetting resin powder having a particle diameter of 300 μm or less in water, the dispersion
A method for producing a prepreg sheet, comprising heating a resin powder agglomerate at a temperature of not lower than the resin softening temperature and a resin powder aggregate, and wet-making the aggregate with the base fiber.