JPH04223113A - Manufacture of laminated sheet - Google Patents

Abstract

PURPOSE:To realize a laminated sheet by low pressure molding under effective reduced pressure atmosphere by a method wherein resin-impregnated base material having high resin content and that having low resin content are piled up alternately. CONSTITUTION:When metal foil is arranged at the outermost layer, resin-impregnated base material having high resin content is arranged so as to come into contact with the inside of said metal foil. Or when the laminated sheet concerned is made of a plurality of impregnated base materials and, in addition, inner layer plate is present, resin-impregnated base material having high resin content is arranged so as to come into contact with both the sides of the inner layer plate. As the resin used, all thermosetting resin or the like, which are generally used for laminated sheet, can be used. As the base material, paper, non-woven fabric or woven fabric made of glass fiber, cellulose fiber, synthetic fiber or the like can be used. The resin content of the resin-impregnated base material, which is arranged on both the sides of the inner layer plate, must be 42% or more. The resin content of the resin-impregnated base material having high resin content, which is provided so as to come into contact with the inside of the metal foil at the outermost layer, must be 38% or more. By piling up the resin-impregnated base material having high resin content and that having low resin content alternately, even at low pressure molding, effective deaeration can be realized under reduced pressure atmosphere.

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a laminate for printed wiring boards. 2. Description of the Related Art In recent years, as electronics have become more sophisticated and functional, the density of printed wiring boards has increased, and printed wiring boards with less warpage and dimensional changes are required. Laminated boards, which are the material for printed wiring boards, are manufactured by low-pressure molding, but low-pressure molding tends to cause voids and scratches on the surface of the laminate. In order to prevent this appearance defect, a method is used in which the press atmosphere is reduced in pressure. Further, when there is a metal foil around the inner layer plate or the outermost layer, the resin-impregnated base material used inside the metal foil is made to have a high resin content. However, such a method alone is insufficient to prevent voids and blurring. [0003] Problem to be Solved by the Invention: When performing low-pressure molding in a reduced-pressure atmosphere, the air between the stacked resin-impregnated base materials is removed, and then the resin flows and fills, which is effective. become. In conventional methods, sufficient consideration is not given to this principle of operation, and low-pressure molding is performed in a reduced-pressure atmosphere, resulting in insufficient effects. In view of the above problems, an object of the present invention is to provide a method for manufacturing a laminate for a printed wiring board by effective low-pressure molding in a reduced-pressure atmosphere. [Means for Solving the Problems] In order to achieve the above object, the present invention forms a laminated material made by stacking a plurality of resin-impregnated base materials under heat and pressure using a press in a reduced pressure atmosphere at low pressure. This is a method for manufacturing a laminate using a laminate in which a resin-impregnated base material with a high resin content and a resin-impregnated base material with a low resin content are alternately stacked. In the method of the present invention, when metal foil is provided as the outermost layer, a resin-impregnated base material with a high resin content is provided in contact with the inside of the metal foil. Moreover, it is composed of a plurality of resin-impregnated base materials, and if an inner layer plate is present, resin-impregnated base materials with a high resin content are arranged in contact with both sides of the inner layer plate. The resin used is generally a thermosetting resin or the like used for laminates. As the base material, paper, nonwoven fabric, or woven fabric such as glass fiber, cellulose fiber, or synthetic fiber can be used. The range of high resin content in the resin-impregnated base material varies depending on the type of resin and base material. Glass cloth epoxy laminate (FR-4)
In this case, the resin-impregnated base materials disposed on both sides of the inner layer must have a resin content of 42% or more. Preferably it is 45 to 50%. Further, the resin content of the high resin content resin-impregnated base material provided in contact with the inner side of the outermost metal foil is required to be 38% or more, preferably 42 to 45%. As a resin-impregnated base material with a low resin content, a resin content of 42% or less is good, but if it is 35% or less, there is no effect, and 35 to 42% is preferable. [Function] According to the present invention, by alternately layering resin-impregnated base materials with high resin content and resin-impregnated base materials with low resin content, even in low-pressure molding, air can be effectively removed by creating a reduced-pressure atmosphere. can be removed. In addition, when the laminated material includes an inner layer plate or when metal foil is placed on the outermost layer, a resin-impregnated base material with a high resin content is placed in direct contact with the inner layer plate or metal foil in order to fill in unevenness caused by circuits, etc. It is effective if [Example] Example 1 100 parts by weight of brominated epoxy resin (hereinafter referred to as parts),
3 parts of dicyandiamide as a curing agent, 0.16 parts of 2-methyl-4-ethylimidazole as a curing accelerator,
30 parts of N-dimethylformamide, 2 parts of methyl cellosolve
A varnish was obtained by dissolving 0 parts. Spread this varnish on a glass cloth (
Nittobo, WE-18K-RB84) resin content 44.0±
Prepreg A is obtained by impregnating and drying to a concentration of 2.0%.
Prepreg B was obtained by adjusting the ratio to 37.0±2.0%. In addition, the above varnish was applied to glass cloth (Nittobo, WE-116
K-RB84) was adjusted to 47.0±2.0% to prepare prepreg C, and prepreg D was adjusted to 37.0±2.0%. One sheet of prepreg A was placed on both sides of the one sheet of prepreg B obtained, and 35 μm copper foil was placed on both outside sides of the prepreg A sheet.
In a reduced pressure atmosphere, the product was heated and pressed at 40 kg/cm 2 at 175° C. for 60 minutes, and then cooled for 30 minutes to obtain a double-sided copper-clad laminate with a thickness of 0.6 mm. A circuit was formed on this by an etching method to obtain an inner layer board, and the circuit was processed for multilayer adhesion. Prepreg C was placed on both sides of this inner layer board, and prepreg D, prepreg A, and 18 μm copper foil were placed on the outside in this order, and heated and pressed at 40 kg/cm2 in a reduced pressure atmosphere at 175°C for 60 minutes, and then cooled for 30 minutes. A four-layer board was obtained. Example 2 Two sheets of prepreg B obtained in Example 1 were placed in the order of prepregs A, B, A, and 18 μm copper foil on both sides, and heated at 40 kg/cm 2 at 175° C. and 60° C. in a reduced pressure atmosphere. After heating and pressurizing for a minute, the product was cooled for 30 minutes to obtain a double-sided copper-clad laminate having a thickness of 1.6 mm. Comparative Example 1 Three sheets of prepreg A obtained in Example 1 were used.
A double-sided copper-clad laminate with a thickness of 0.6 mm was obtained under the same lamination conditions as . Two sheets of prepreg C were placed on both sides of the inner layer board obtained in the same manner as in Example 1, and prepreg A and 18 μm copper foil were placed on the outside in that order, and a four-layer board was obtained under the same lamination conditions as in Example 1. Ta. Comparative Example 2 8 sheets of prepreg A obtained in Example 1 were stacked together Example 2
A double-sided copper-clad laminate with a thickness of 1.6 mm was obtained under the same lamination conditions as described above. Table 1 shows the characteristics of Examples 1 and 2 and Comparative Examples 1 and 2. After treatment in the table means pressure cooker (121℃
, 1.2 atm) after 4 hours of treatment. [Table 1] ---┘ [0010] [Effects of the Invention] Table 1 shows that the laminate produced by the method of the present invention has a good appearance when used for printed wiring boards. In the example of the present invention, no voids or scratches were produced in the sample, and the insulation resistance characteristics were the same as in the comparative example, that is, the conventional method. On the contrary, the comparative example produced voids, indicating insufficient air removal.

Claims (3)

[Claims] Claim 1: In the production of a laminate in which a laminate consisting of a plurality of resin-impregnated base materials stacked together is heated and pressure-molded in a reduced pressure atmosphere at low pressure using a press, a resin-impregnated base material with a high resin content and a resin with a low resin content are used. A method for producing a laminate, characterized by using a laminate made by alternately laminating impregnated base materials. 2. The method for manufacturing a laminate according to claim 1, wherein when metal foil is arranged on the laminate, a resin-impregnated base material in contact with the metal foil has a high resin content. 3. The method for manufacturing a laminate according to claim 1, wherein when an inner laminate is added to the laminate, a resin-impregnated base material in contact with the inner laminate has a high resin content.