JPS5831757B2 - Manufacturing method for electrical insulating laminates and metal foil laminates for printed circuits - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an electrically insulating laminate having a novel structure or a metal foil-clad laminate for printed circuits made of the electrically insulating laminate and metal foil. Therefore, it is an object of the present invention to provide an electrical laminated board or a metal foil-covered laminated board for printed circuits which has excellent electrical insulation properties, dimensional stability, and heat resistance.

In the present invention, the electrical insulating laminate refers to a laminate used as a substrate or support plate for various electronic components and devices, and the metal foil-covered laminate for printed circuits is used to mount electronic circuit components, etc. means a printed circuit board that constitutes a printed circuit used in

Conventionally, these materials are made of thermosetting resin phenolic resin and paper as a base material, or epoxy resin and paper, or epoxy resin and glass cloth, etc., and these resin varnishes are applied to the base material such as paper or glass cloth. It is manufactured by impregnating the prepreg, then constructing a prepreg, and then layering a large number of sheets of these or further metal foil, such as electrolytic copper foil, and laminating them in a heated and pressurized press to fully cure the resin. .

Conventional electrical laminates or metal foil laminates for printed circuits manufactured in this way have a structure as shown in Fig. 1, for example, when they are made of phenol resin and paper. FIG. 1 shows a cross-sectional state of a conventional insulating laminate.

That is, although paper composited with resin is laminated in multiple layers, the paper fibers are substantially in contact with or entangled with each other between the layers, and the reality is that the paper is not separated between each layer.

On the other hand, it is well known that the electrical insulation properties, heat resistance, dimensional stability, etc. of electrical insulating laminates and metal foil-clad laminates for printed circuits are impaired due to moisture absorption and water absorption.

This is not desirable from a practical standpoint. Water mainly enters the board through the surface layer of the board, but the presence of fibers in the base material, such as paper, and the presence of an interfacial area between the fibers and the resin make it easier for water to enter.

For example, this means that the paper fibers are exposed on the surface layer, and the surface layer is formed with an adhesive for bonding metal foil, or a layer made of resin equivalent to that used for insulating plates. When measuring the surface insulation resistance of a surface under moisture absorption, the rate of decrease in the former case is extremely large.

This indicates that the presence of paper fibers reduces the resistivity and therefore
It can be said that it acts as a dominant factor in the surface area of water and the penetration of water into the board.

Therefore, in conventional products, the paper fibers are intertwined between each layer and can be considered as a substantially continuous structure in cross section, so in such a state, water that enters from the surface is continuously connected. Therefore, products with a structure similar to conventional products easily absorb moisture and water, and their electrical insulation properties, especially in such cases, are poor. JIS-C-648
This causes a large decrease in the volume resistivity and insulation resistivity specified in 1. Furthermore, the amount of moisture absorbed increases, which impairs heat resistance, such as solder heat resistance. The foil-clad laminate has several drawbacks, such as increased volume of the insulating plate, poor dimensional stability, and increased warping of the board.

In view of the current situation, the inventors of the present invention conducted extensive research and found that, as in conventional products, the structure in which each base material layer comes into contact with each other and is essentially a continuum when viewed in cross section has been eliminated. , when a thermosetting resin layer is formed between each base material to substantially cut off contact between each base material layer, it becomes an electrical insulating laminate or a printed circuit insulating laminate with excellent properties. find out what will become,
A method for manufacturing such a laminate has been invented.

In the present invention, a resin liquid-impregnated base material is prepared by impregnating and/or coating a base material excessively with a thermosetting resin that is itself liquid at room temperature, and these are superimposed, and metal foil is applied if necessary. After stacking, the electricity is passed through slits having a predetermined interval so that a continuous resin layer is formed over substantially the entire area between each base material, and then cured. This is a method for manufacturing insulating boards for industrial use or metal foil-clad laminates for printed circuits.

In the insulating laminate having the structure of the present invention, the resin layer existing between the first layer base material and the second layer base material prevents water from entering the inside more clearly from the surface. It can be said that it is interrupted, sequentially, etc.

Therefore, the intrusion of water into the interior of the insulating plate becomes slight, and the above-mentioned deterioration of properties due to moisture absorption and water absorption can be greatly improved.

As the base material, for example, known materials such as linter paper or kraft paper containing cellulose fiber as a main component, glass cloth, or asbestos cloth can be used.

The use of paper is inexpensive and inherently has high hygroscopicity, so it is one of the preferred embodiments to which the present invention can be applied very effectively.

In the present invention, the resin layer existing between the multiple base materials is in an uncured state, and when using an epoxy resin or unsaturated polyester resin that is liquid at room temperature, it is impregnated with a liquid of these resins. When stacking the base materials, a resin liquid is applied or excessively impregnated with the resin liquid, and the spacing is calculated in advance from the thickness and number of base materials, or the thickness of the resin layer between the base materials, etc. This can be achieved by forming a laminate by passing it through slits, etc., and curing it.

Since such a resin does not contain volatile components such as a solvent, it does not require drying of the solvent, and in addition, it is easy to control the thickness of the resin layer between each base material, and is suitable for the present invention. .

Furthermore, the viscosity of the uncured resin liquid is also a factor in controlling the impregnation into the base material and the resin layer between the base materials, but the resin liquid has a wide viscosity range, for example, 0.05 to 15 poise. An unsaturated polyester resin that is liquid at room temperature when uncured and can be easily adjusted is suitable in the present invention.

Of course, these resins may be blended with additives such as flame retardants, flame retardant aids, fillers, colorants, and curing catalysts, which are usually blended into electrical laminates.

The fact that the resin is thermosetting does not necessarily mean that the actual curing is carried out by heat, and the actual curing may be carried out by room temperature curing, light beam, electron beam, radiation, etc.

The thickness of the resin layer between each base material is usually preferably about 1 to 100 μm.

If the thickness of this resin layer is excessively thick, other properties such as punching properties may be impaired.

The thickness of this resin layer is preferably equal to or less than the thickness of each base material used.

In addition, to confirm the existence of this resin layer and its thickness, it is possible to scrape the cross section with a sharp knife, or fix the specimen using resin for embedding the specimen, cut it, and lightly polish it. Accurate observation is usually possible using a well-known method using an optical microscope with a magnification of about 10 to 100 times.

The metal foil used in the present invention is preferably an aluminum foil or a copper foil in terms of conductivity, mechanical strength, etc., and a so-called electrolytic copper foil is preferable due to its adhesive properties.

In the case of single-sided metal foil or insulating laminates (excluding double-sided metal foil cladding), the laminate is supported and the peroxide blocks oxygen from the air during resin curing, and the resin also stains the slit walls, etc. In order to avoid this, it is preferable to laminate metal foil or other sheet-like material to the surface where metal foil is not laminate, and peel it off after curing.

Furthermore, in the present invention, in addition to the presence of a resin layer between each base material layer, a resin layer is also present on one or both surface layers of an insulating laminate, or on the bonding surface with metal foil in a metal foil-covered laminate for printed circuits. Needless to say, it is preferable that a resin layer is present.

It goes without saying that it is preferable that each base material layer is completely separated by a resin layer, but the effects of the present invention can still be achieved even if the base materials come into contact with each other to some extent.

In the present invention, for example, when paper with a thickness of about 200 to 300 μm is used as a base material, for example, by laminating 2 to 10 sheets of paper, an electrical laminate with a thickness of about 0.5 to 3 μm or these A metal foil-clad laminate for printed circuits having a thick insulating plate can be easily constructed.

The present invention will be explained in more detail with reference to Examples below.

Example 1 The following resin composition is liquid at room temperature: epoxy resin (Epicote 828 manufactured by Shell Oil Co., Ltd.) 100 weights 1 HN-220080 manufactured by Hitachi Chemical Co., Ltd. (Methyltetrahydrophthalic anhydride) Dimethylbenzylamine 0° 1.
Impregnated kraft paper with a thickness of 270 μm and a basis weight of 150 g/m2 was placed on an aluminum foil with a thickness of 100 μm held horizontally, and then this resin liquid was applied onto the impregnated paper to a thickness of about 1 inch. By repeating the process of impregnating the paper with the resin liquid and applying the resin liquid, a stack of six sheets of impregnated paper excessively impregnated with the resin liquid was obtained.
Furthermore, after applying resin liquid on top of this, the thickness is 100 μm.
Layer m aluminum foil, then set the clearance to 1
Pass it between rolls set at 800 μm, then,
It was cured at 150° C. for 60 minutes, and then the aluminum foil was peeled off to obtain a laminated insulating board with a thickness of about 1.6 peaks.

This product had a resin layer with a thickness of about 20 μm between each layer of paper as a base material.

Comparative Example 1 The paper used in Example 1 was impregnated with the resin liquid used in Example 1 using a curtain flow method so that the resin adhesion was 50%, and seven sheets of this impregnated paper were stacked one on top of the other. Aluminum foils with a thickness of 100 μm are stacked on both sides and passed between rolls with a clearance of 1800 μm, and then hardened in the same manner as in Example 1, resulting in a thickness of approximately 1,671 μm! I+!
An insulating laminate was obtained.

This product had substantially no resin layer between each layer of paper as a base material.

Example 2 Using a resin liquid consisting of 100 parts by weight of a commercially available unsaturated polyester resin (Polymer 6304 manufactured by Narita Pharmaceutical Co., Ltd.) and 1 part by weight of cumene hydroperoxide, six sheets of impregnated paper were stacked together in the same manner as in Example 1. Finally, an electrolytic copper foil with a thickness of 35 μm was layered, passed between two rolls with a clearance of 1730 μm, and heated at 100°C x 30
After curing at 85° C. for 10 hours, the aluminum foil on one side was peeled off to obtain a copper-clad laminate having a thickness of about 1.6 mm.

This product had a resin layer with a thickness of about 20 μm between each paper layer as a base material.

Comparative Example 2 The resin liquid used in Example 2 was treated using a curtain flow method.
The paper used in Example 1 was impregnated to obtain impregnated paper with a resin adhesion content of 53%, and seven sheets of this paper were laminated, and then one side was coated with a thickness of 1.
00 μm aluminum foil and 35 μm thick electrolytic copper foil on the other side, passed through two rolls with a clearance of 1730 μm, and then cured in the same manner as in Example 2 to increase the thickness. A copper-clad laminate having a length of about 1.6 mm was obtained.

This product did not have a substantial resin layer between each layer of paper as a base material.

The test results of these Examples and Comparative Examples are shown in Table 1.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a cross section of an insulating plate part of a conventional electrical insulating laminate or printed circuit laminate, and FIG. 2 is a sectional view of a laminate with a resin layer formed on the surface. FIG. 3 is a sectional view showing a cross section of an insulating laminate or an insulating laminate portion according to the present invention. 1 is a resin-impregnated paper, 2 is a superimposed portion of the resin-impregnated paper, 3 is a resin layer on the surface of the laminate, and 4 is a resin layer that separates the laminated base materials.

Claims (1)

[Claims] 1. A thermosetting resin that is itself liquid at room temperature,
A base material impregnated with a resin liquid is made by impregnating the base material excessively by impregnating it and/or coating it, and after stacking these and, if necessary, overlapping a metal foil, substantially the entire area is covered between each of the base materials. A method for manufacturing an electrical insulating board or a metal foil-clad laminate for printed circuits, which comprises passing the resin through slits having a predetermined interval so as to form a continuous resin layer, and curing the resin. 2. The method according to claim 1, wherein the thermosetting resin is an unsaturated polyester resin. 3. The method according to claim 1, wherein the thermosetting resin is an epoxy resin. 4. The method of claim 2, wherein the unsaturated polyester resin is itself liquid at room temperature before curing. 5. The method of claim 3, wherein the epoxy resin itself is liquid at room temperature before curing. 6. The method according to claim 1, wherein the base material is paper mainly composed of cellulose fibers. 7. The method according to claim 1, wherein the thickness of the resin layer existing between each base material layer is smaller than the thickness of each base material layer, and is 1 to 100 μm. 8. The method according to claim 1, wherein the resin present between the base material layers and the resin impregnated into the base material are the same type of thermosetting resin.