JPH0145414B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a laminate that can be easily stamped, a so-called composite laminate or a metal foil-clad composite laminate. In recent years, printed wiring boards have become thinner and smaller in line width and land area as electronic devices become more densely packaged. There has also been a noticeable movement towards lower costs of printed wiring boards. Therefore, when drilling holes in land portions, punching with hole diameters of 2φ and 1.8φ is increasingly used instead of conventional drilling. As a laminate for punching, a composite laminate is produced by heating and press-molding prepreg made of a glass cloth base material impregnated with epoxy resin on both sides of a prepreg layer made of a glass cloth base material impregnated with epoxy resin. be. However, even with this laminate, if the land diameter is small, the peeling strength of the land after punching will be significantly reduced during punching, which applies a stronger impact than drilling, and the land will peel off during component mounting. . An object of the present invention is to provide a laminate that can be punched out well without causing the above-mentioned inconveniences. When the cross-section of the composite laminate is viewed under a microscope after being punched, the strength of the glass fibers is strong, so the glass fibers break inside the lands, causing the glass fibers and resin to separate. It was found that the land peeling strength was reduced due to the presence of In the drawings, 1 is an epoxy resin layer whose base material is glass cloth or paper, 2 is an epoxy resin layer whose base material is glass cloth on the surface, and 3
is a land, and 4 is a punched hole. The glass fibers 5 constituting the glass cloth are bent, and the epoxy resin layer 2 and the glass fibers 5 are separated to form a cavity 6. The present invention was made as a result of detailed research based on the above knowledge, and it is possible to apply a 25 mm width per 25 mm width in the vertical and horizontal directions on both sides of a prepreg layer made of a glass nonwoven fabric or paper base material impregnated with epoxy resin. It is characterized by stacking a prepreg impregnated with an epoxy resin on a glass cloth base material with a total tensile strength of 20 to 70 kg and heating and pressurizing it. In other words, the conventionally used high-strength glass cloth (the total tensile strength is
100Kg or more), by using a glass cloth with low strength on the surface, the glass fibers are cut without breaking during the punching process, and a good punching process is achieved without creating cavities due to separation of the epoxy resin layer and the glass fibers. It can be done. Therefore,
The metal foil-clad laminate for printed circuits to which the present invention is applied has the advantage that the adhesive strength of the formed lands does not decrease even after punching. In the present invention, the vertical and horizontal directions of the glass cloth are
If the total tensile strength per 25 mm width is less than 20 kg, cavities will not occur due to separation of the epoxy resin layer and glass fiber after punching, but the bending strength of the composite laminate will decrease, making it difficult to mount heavy parts. Intolerable. On the other hand, if the total strength exceeds 70 kg, the peeling of the epoxy resin layer and glass fiber after punching will be significant, so a range of 20 to 70 kg is appropriate. The glass nonwoven fabric base material used in the present invention is one that is commonly used, such as glass mat, glass nonwoven fabric using a thermosetting resin binder, glass nonwoven fabric using a thermoplastic resin binder, cellulose-mixed glass nonwoven fabric, or synthetic fiber-mixed glass nonwoven fabric. be. Further, when a paper base material is used, commonly used materials such as kraft paper, linter paper, and reinter-mixed kraft paper are used. The glass cloth used in the present invention has lower strength than conventional glass cloth, and the following methods can be used to reduce the strength. That is, (1) mechanically pulling the glass cloth to partially cut it and reduce its strength. (2) 400~ for glass cloth or glass fiber before weaving
Apply heat to 600℃ to reduce strength. (3) Treat glass cloth or glass fibers before weaving with strong acids to reduce their strength. The epoxy resin used in the present invention is an epoxy resin mixed with a curing agent and a curing accelerator, and may also contain fillers and colorants. Next, examples of the present invention will be described. Example 1 Plain woven glass fabric A and glass nonwoven fabric shown in Table 1 were impregnated with an epoxy resin varnish containing 100 parts by weight (hereinafter simply referred to as "parts") of epoxy resin, 4 parts of dicyandiamide, and 0.2 parts of dimethylbenzylamine and dried. , the respective prepregs were obtained. One glass cloth base material prepreg was placed on each of the upper and lower surfaces of the thus obtained glass nonwoven base material prepreg layer,
Place copper foil on one side, temperature 160℃, pressure 30Kg/cm ²
Lamination molding was carried out for 30 minutes to obtain a single-sided copper-clad laminate with a thickness of 1.6 mm. Example 2 The epoxy resin varnish used in Example 1 was impregnated into linter paper and dried to form a prepreg. A predetermined number of the prepregs were stacked, and one glass cloth base material prepreg used in Example 1 was placed on each of the upper and lower surfaces. , with copper foil placed on one side at a temperature of 160℃ and pressure.
Lamination molding was carried out for 60 minutes at 50 kg/cm ² to obtain a single-sided copper-clad laminate with a thickness of 1.6 mm. Comparative Example 1 The epoxy resin varnish used in Example 1 was
Plain woven glass cloth B shown in the table was impregnated and dried to obtain a prepreg. One prepreg was placed on each of the upper and lower surfaces of a predetermined number of stacked linter paper base prepregs used in Example 2, and lamination molding was performed in the same manner as in Example 2 to obtain a single-sided copper-clad laminate with a thickness of 1.6 mm. Ta. Comparative Example 2 The epoxy resin varnish used in Example 1 was
Plain woven glass cloth C shown in the table was impregnated and dried to obtain a prepreg. One prepreg was placed on each of the upper and lower surfaces of a predetermined number of stacked linter paper base prepregs used in Example 2, and lamination molding was performed in the same manner as in Example 2 to form a single-sided copper-clad laminate with a thickness of 1.6 mm. Obtained.

【table】

[Table] Comparative Example 3 One sheet each of the glass cloth base material prepreg used in Comparative Example 1 was placed on the top and bottom surfaces of a predetermined number of stacked glass nonwoven fabric base material prepregs used in Example 1, and the same procedure as in Example 1 was carried out. A single-sided copper-clad laminate with a thickness of 1.6 mm was obtained by lamination molding. Comparative Example 4 The glass fabric base material prepreg used in Comparative Example 2 was placed on each of the upper and lower surfaces of a predetermined number of stacked glass nonwoven fabric base material prepregs used in Example 1, and laminated molding was performed in the same manner as in Example 1. A single-sided copper-clad laminate with a thickness of 1.6 mm was obtained. The single-sided copper-clad laminates obtained in Examples 1 and 2 and Comparative Examples 1, 2, 3, and 4 were etched to form a 2.0φ land, with a punch diameter of 1.0φ and a clearance of 10/100.
Punching was performed using the test molds (on both sides). Table 1 shows the bending strength, bending elastic modulus, land peeling strength, and punched appearance of each laminate. Also shown is the land peeling strength when a land of 2.0φ was formed on the single-sided copper-clad laminates of Comparative Examples 1 and 3 and drilled with a drill diameter of 0.9φ.

[Table] As is clear from Table 2, according to the present invention,
It is possible to obtain a laminate that does not peel off even after punching, has a good appearance at the punched portion, and has sufficient mechanical strength. In addition, when applied to metal foil-clad laminates, there is no decrease in peel strength of the metal foil even after punching, and it has extremely high industrial value in efficiently manufacturing high-density printed wiring boards. It is a big thing.

[Brief explanation of drawings]

The drawing is a sectional view showing the state of punched holes in a conventional composite laminate. 1 is an epoxy resin layer based on glass nonwoven fabric or paper, 2 is an epoxy resin layer based on glass cloth, 3 is a land, 4 is a hole, 5 is glass fiber, 6
is hollow.

Claims (1)

[Scope of Claims] 1. A laminate in which prepreg layers made of a glass cloth base material impregnated with an epoxy resin are placed on both sides of a prepreg layer made of a glass nonwoven fabric or paper base material impregnated with an epoxy resin, and integrally laminated and molded, A laminate characterized in that the glass cloth base material has a total tensile strength of 20 to 70 kg per 25 mm width in the longitudinal and lateral directions.