JPS6032655A - One-surface metallic foil lined laminated board having improved warpage characteristic and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a paper-based single-sided metal foil-clad laminate having excellent mechanical and electrical properties and improved warping properties, and a method for producing the same.

In recent years, with the progress in automation of the manufacturing process of printed circuit boards and the automation of parts insertion into printed circuit boards, the requirements for preventing warpage and twisting of printed circuit boards have become increasingly severe.

Single-sided metal foil-covered laminates have an asymmetric structure in which metal foil is pasted on only one side of the laminate, so the metal foil may be exposed to heat or moisture absorption during the manufacturing of metal foil-covered laminates or printed circuit boards. Warping and twisting inevitably occur due to the difference in expansion and contraction between the substrate and the substrate. Warping due to heating occurs when the laminate shrinks compared to metal, resulting in a convex warp (plus warpage) with the metal foil side facing outward, and warping due to moisture absorption results in a convex warpage (positive warpage) due to expansion of the laminate, with the metal foil side facing inward. This results in a concave warp (minus warp). Conventionally, various attempts have been made to improve warpage characteristics, but single-sided products have low levels of both positive warpage due to heating and negative warpage due to moisture absorption, and have excellent mechanical and electrical properties. It has been extremely difficult to obtain metal foil-clad laminates.

For example, it is possible to use a resin that expands and contracts less when heated or absorbs moisture, or to increase the rigidity of the resin or base material to make it less likely to warp. This causes a decrease in mechanical properties such as impact strength, which poses a serious problem in practice.

In view of this current situation, the inventors of the present invention have carried out extensive testing and testing, and have found that by appropriately combining kraft paper as a base material as explained below, both positive warping due to heating and negative warping due to moisture absorption are small, and the mechanical properties are good. It has been discovered that a single-sided metal foil-clad laminate with excellent electrical properties can be obtained, leading to the present invention. That is, the present invention provides a single-sided metal foil-covered laminate formed by laminating and curing a plurality of base materials impregnated with a curable resin liquid and metal foil with an adhesive, in which the plurality of base materials are made of kraft paper and linter paper. The center of the base material of the linter paper, which consists of one or more sheets of linter paper, coincides with the center of the entire base material, or is located on the far side from the metal foil, and the outermost layer of the plurality of base materials is To provide a single-sided metal foil-covered laminate characterized in that both sides are made of kraft paper. An example of the structure of the base material of the present invention in the case of a single-sided metal foil-clad laminate consisting of five base materials is shown in FIGS. 1 to 5. The reason why the center of one or more base materials is aligned with the center of the entire base material or located on the side far from the metal foil is to reduce the occurrence of warping, especially negative warping due to moisture absorption. It's for a reason. The reason why warping is improved by introducing an asymmetric structure into the base material composition is not necessarily clear, but it is thought that the subtle differences in expansion and contraction due to moisture absorption and heating between kraft paper and linter paper are at play. Conceivable.

Next, one reason why the outermost layer of the plurality of base materials is made of kraft paper is to prevent deterioration of mechanical properties such as bending strength, rigidity, and impact strength due to linter paper. For example, in Figure 1, if a sheet of linter paper is used on the top layer closest to the copper foil or the bottom layer furthest from the copper foil, the bending strength, rigidity, and (h impact strength) of the laminate will decrease significantly. Another reason is that if the linter paper is placed on the layer farthest from the copper foil, the positive warpage due to heating tends to become too strong.There is no limit to the number of sheets of linter paper that can be used, but the total thickness of the linter paper It is preferable from the viewpoint of warping characteristics and mechanical properties to adjust the number of sheets so that the kraft paper is thinner than the total thickness of the kraft paper.

In the drawings, FIGS. 1 to 5 are enlarged exploded sectional views of the single-sided metal foil-clad laminate of the present invention.

1 is a metal foil, 2 is a linter paper layer, and 3 is a kraft paper layer. It can be seen that the center A-A of the entire base material excluding the metal foil 1 coincides with the center of the linter paper base material 2 in the examples of FIGS. 1, 4, and 5. Also, Figures 2 and 3
In the figure, it can be seen that the center B-B of the linter paper base material is located on the side farther from the metal foil 1 than the center A-A of the entire base material. In both cases, the outermost layer of the base material is composed of kraft paper 2. In particular, it has been found that it is preferable for the center B-B of the linter paper base material to be located farther from the metal foil 1 than the center A-A of the entire base material, since negative warping due to moisture absorption is reduced.

The kraft paper and linter paper used as the base material in the present invention are:
Any paper that is generally used as impregnated paper for electrical laminates may be used. Density is 0.45-0.60,
Particularly suitable is one having a thickness of 100 to 350 μm.

Before being impregnated with the curable resin, these base materials are pre-treated with resins that have an affinity for cellulose, mainly composed of melamine resins, phenolic resins, epoxy resins, etc., resulting in advanced electrical properties and water resistance. It is desirable to have good punching workability.

The curable resin in the present invention includes unsaturated polyester resin, diacrylphthalate resin, vinyl ester resin, phenol resin, melamine resin, epoxy resin, and the like.

Among these, the effects of the present invention are particularly remarkable in the case of unsaturated polyester resins, diallyl phthalate resins, vinyl ester resins, and epoxy resins that essentially do not generate reaction by-products such as moisture during curing. In the case of the above resin, since the moisture content of the laminate immediately after production is extremely low, it is easily affected by moisture absorption during the printed circuit board manufacturing process, the component mounting process on the printed circuit board, or during inventory. By combining linter paper and kraft paper, the occurrence of negative warping can be prevented.

As mentioned above, in the case of a curable resin that essentially does not generate reaction by-products during curing and is itself liquid at room temperature, the present inventors have already developed
As proposed in JP-A-8227, JP-A-56-98136, etc., a pressureless continuous manufacturing method can be applied and is a preferred embodiment of the present invention.

Metal foils include copper foil, aluminum foil, nickel foil,
Examples include iron foil, stainless steel foil, etc., but copper foil is usually used. Note that as the adhesive material, any of phenol resin adhesives, epoxy resin adhesives, vinyl ester adhesives, etc. may be used.

If the resin impregnated into the base is unsaturated polyester resin,
It is preferable to use an epoxy adhesive because it provides good soldering heat resistance, adhesive strength, and warpage characteristics.

Next, the present invention will be explained by examples.

Examples 1-5. Comparative Examples 1 to 3 An unsaturated polyester resin liquid was prepared containing 100 parts by weight of unsaturated polyester (Polymer 3311, manufactured by Narita Pharmaceutical Co., Ltd.), 1 part by weight of cumene hydroperoxide, and 0.2 parts by weight of 6% cobal naphthenate. Kraft paper (Desumi Kokusaku Pulp ZBS-135, 10 mils) pretreated with melamine resin (Nikaratsuku MX-031 manufactured by Sansho Chemical Co., Ltd.) and linter paper (
Daicel Chemical Co., Ltd. C-10, 10 mils) was impregnated with the above unsaturated polyester resin liquid, and the resin-impregnated base material and copper foil with epoxy resin adhesive were stacked with the base material composition shown in Table 1, and then fixed by a roll. After squeezing to a thickness, 110℃
The mixture was cured for 30 minutes at 150° C. and further for 15 minutes at 150° C. to obtain a single-sided copper foil-clad laminate having a thickness of about 1.6 mm. A circuit with a copper foil residual rate of 65% was formed on the obtained laminate by etching, and the warp was measured after heating at 160° C. for 10 minutes.

Further, this printed circuit board was left in a constant temperature and humidity machine at 40° C. and 85% RH for 4 days, and then warpage due to moisture absorption was measured. The dimensions of the board are 400mm long and 340u wide.
To measure warpage with +, the heights of the four corners were measured on a surface plate, and the average value was taken as the amount of warpage. In addition to warpage, bending strength and falling ball impact strength were also measured. Table 1 shows the performance of each copper-clad laminate for Examples and Comparative Examples.

(Margin below) 0

[Brief explanation of the drawing]

1 to 5 are cross-sectional views showing the structure of a base material of a single-sided metal foil-clad laminate according to an embodiment of the present invention. 1 is metal foil, 2 is linter paper, and 3 is kraft paper. 2 Figure 1 Figure 2 Figure 31"l!l Figure 4 Figure 5

Claims (1)

[Claims] [11] In a single-sided metal foil-covered laminate formed by laminating and curing a plurality of base materials impregnated with a curable resin liquid and a metal foil with an adhesive, the plurality of base materials are made of kraft paper and Consisting of linter paper, the center of the base material of one or more sheets of linter paper coincides with the center of the entire base material or is located on the far side from the metal foil, and the outermost part of the multiple base materials A single-sided metal foil-covered laminate characterized in that the layers are made of kraft paper. (2) The single-sided metal foil-clad laminate according to claim 1, wherein the curable resin liquid is a resin that essentially does not generate reaction by-products during curing. (3) The single-sided metal foil-clad laminate according to claim 2, wherein the cured resin liquid is an unsaturated polyester resin. (4) A single-sided metal foil-clad laminate according to any one of claims 1 to 3, wherein the adhesive is an epoxy resin-based adhesive. (5) A plurality of base materials are individually and continuously impregnated with a curable resin solution that essentially does not generate reaction by-products during curing and is itself liquid, and the impregnated base materials and adhesive-attached In a method of manufacturing a single-sided metal foil laminate by continuously laminating metal foils and curing them continuously under substantially no pressure conditions, the plurality of base materials are made of kraft paper and linter paper, The center of the base material of one or more sheets of linter paper coincides with the center of the entire base material or is located on the far side from the metal foil, and the outermost layer of the multiple sheets of base material is kraft paper. A method for producing a single-sided metal foil-clad laminate characterized by: