JPH04358805A - Manufacture of prepreg - Google Patents

Abstract

PURPOSE:To cause foam or volatile component not to remain inside even when the curing of a prepreg is advanced so as to suppress resin-flow in forming of the prepreg in which the resin composition containing inorganic filler is made into varnish, and an unwoven cloth is coated with said composition and is dried. CONSTITUTION:When an unwoven cloth is coated with the thermosetting resin varnish containing inorganic filler, its coating amount is decreased in first coating, and its curing is also suppressed, and then coating and drying process is repeated until prescribed resin amount is obtained.

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 prepreg using nonwoven fabric as a base material.

0002

[Prior art] CEM using glass nonwoven fabric as a base material
-3 material allows the assembly of boards using V-cuts, and has a great economical advantage in processing wiring boards. Furthermore, by using a resin containing an inorganic filler, it has become possible to obtain a material that is almost equivalent to FR-4 using glass woven fabric in terms of through-hole reliability, warpage, dimensional accuracy, and other properties.

[0003] Nonwoven fabric has a low density, and a large amount of resin is impregnated per unit volume. When a laminate is manufactured using such prepreg, the thickness of the end portion becomes smaller. Therefore, in order to suppress resin flow during molding, conventionally the drying temperature was higher than that of general prepreg to increase the degree of curing of the resin.

0004

[Problem to be solved by the invention] When a laminate is manufactured using a prepreg with a highly cured resin, the resin flow in the center is reduced and the curing time is shortened, resulting in voids and scratches in the center. . Further, since the degree of curing is different from that of the glass woven fabric base material prepreg used for the surface layer of the laminate, the adhesion between the glass woven fabric base material layer and the glass nonwoven fabric base material layer may be insufficient. Furthermore, since the surface layer of the prepreg receives more heat energy than the inside, the surface layer hardens first while trapping the internal voids and volatile components that would otherwise volatilize during drying. This can cause voids and blisters.

[0005] This phenomenon is conspicuous because thermosetting resin varnishes containing inorganic fillers have high viscosity. The present invention attempts to solve such problems.

[0006]

[Means for Solving the Problems] The present invention provides a method for applying a thermosetting resin varnish containing an inorganic filler to a nonwoven fabric base material, drying it, and then applying a thermosetting resin varnish containing an inorganic filler. , the drying process is repeated one or more times.

[0007] The resin used in the present invention is a general resin used for electrical insulating boards, such as phenol resin, epoxy resin, polyimide resin, or polyester resin. In addition, conditions such as resin viscosity, resin content, drying conditions, etc. for each coating are individually selected to be optimum values depending on the type of resin. The coating amount of the resin is preferably 1/2 or less of the final coating amount in the first step, and it is better to suppress curing in the first step as much as possible. The greater the number of repeated steps, the better the results, but because the number of manufacturing steps increases, it is preferable to repeat the steps 2 to 3 times.

[0008]

[Operation] Normally, all the required amount of resin is applied and dried in one process, but it is done in two or more processes.
The amount of resin applied to the base material in one process can be reduced. In particular, by reducing the amount of resin applied for the first time, a thin film of resin is formed on the surface of the base fiber, and the affinity between the resin and the base material increases in the second and subsequent applications. Therefore, the air in the base material is easily replaced by the resin, and a prepreg with fewer voids can be obtained. Also,
By reducing the amount of resin applied in one step, the thickness of the resin becomes smaller, and the difference in the degree of curing between the surface layer and the inside of the resin in the drying step becomes smaller.

[0009]

【Example】

Example 1 100 parts by weight of brominated epoxy resin for laminates, 4 parts by weight of dicyandiamide and 0.15 parts by weight of 2-methyl-4-ethylimidazole were mixed with 30 parts by weight of N,N-dimethylformamide and 30 parts by weight of methyl cellosolve. It was dissolved in a solvent. Furthermore, aluminum hydroxide (CL-
310) was added and stirred.

[0010] This inorganic filler-containing varnish was applied to a glass nonwoven fabric (EPM-4060N manufactured by Nippon Vilene Co., Ltd.).
Coated with a resin content of 30.0±2.0%,
It was dried at 0°C for 3 minutes. In addition, the resin content was 90.0±2.
The inorganic filler-containing varnish was applied again so that the concentration was 0%, and dried at 170° C. for 10 minutes to obtain a glass nonwoven fabric prepreg. A varnish with the same composition as the above varnish except that it does not contain aluminum hydroxide is applied to glass cloth (WE-18K-RB84 manufactured by Nittobo Co., Ltd.) with a resin content of 41.0 ± 3.0%.
The glass fabric prepreg was coated and dried to obtain a glass woven fabric prepreg.

[0011] Three sheets of the glass nonwoven fabric prepreg obtained as described above were stacked, glass woven fabric prepregs were stacked above and below, and an electrolytic copper foil (manufactured by Nippon Denki Co., Ltd.) with a thickness of 18 μm was placed on the outermost layer. Temperature 170℃, pressure 2.94MP
A copper-clad laminate with a thickness of 1.6 mm was obtained by heating and pressurizing for 70 minutes.

Example 2 The same inorganic filler-containing varnish as in Example 1 was applied to the same glass nonwoven fabric so that the resin content was 30.0±2.0%.
After drying at 50℃ for 3 minutes, the resin content is 60.0±2.0 again.
%, apply varnish containing inorganic filler to 150%
It was dried at 170° C. for 3 minutes, coated with an inorganic filler-containing varnish at a third time to a resin content of 90.0±2.0%, and dried at 170° C. for 10 minutes to obtain a glass nonwoven fabric prepreg.

[0013] Three sheets of this glass nonwoven fabric prepreg were stacked,
The same glass woven fabric prepreg as in Example 1 was layered above and below it, and a copper foil with a thickness of 18 μm was placed as the outermost layer, and a copper-clad laminate with a thickness of 1.6 mm was obtained under the same lamination conditions as in Example 1.

Comparative Example 1 The same inorganic filler-containing varnish as in Example 1 was applied to the same glass nonwoven fabric in one coat so that the resin content was 90.0%.
It was dried at 0° C. for 12 minutes to obtain a glass nonwoven fabric prepreg.

[0015] Three sheets of this glass nonwoven fabric prepreg were stacked,
The same glass woven fabric prepreg as in Example 1 was layered on top and bottom of this, and the same procedure as in Example 2 was carried out to obtain a copper-clad laminate having a thickness of 1.6 mm.

Comparative Example 2 Three sheets of the same glass nonwoven fabric prepreg as in Comparative Example 1 were stacked, and glass woven fabric prepregs were stacked above and below, and the outermost layer had a thickness of 1
8μm copper foil placed, temperature 170℃, pressure 5.88M
It was heated and pressurized at Pa for 70 minutes to obtain a copper-clad laminate having a thickness of 1.6 mm. Table 1 shows the properties of the copper-clad laminate obtained as described above. In addition, some of the laminates obtained in Comparative Examples 1 and 2 were prone to peeling between the glass woven fabric base material layer and the glass nonwoven fabric base material layer.

[0017]

[Table 1] Substrate heat resistance: Pressure cooker test 121℃
0.12MPa solder dip at 260℃ for 20 seconds

0
018]

[Effect of the invention] If coating and drying is performed in one time, it is not possible to obtain a glass nonwoven fabric prepreg with good moldability, but by repeating the process of coating and drying two or more times, the degree of resin curing of the glass nonwoven fabric prepreg can be improved. It is evened out and moldability is improved.

Claims (1)

[Claims] Claim 1: After applying a thermosetting resin varnish containing an inorganic filler to a nonwoven fabric base material and drying, repeating the application and drying of the thermosetting resin varnish containing an inorganic filler one or more times. A prepreg manufacturing method characterized by: