JPS63315213A - Manufacture of polyolefin metallic laminated sheet - Google Patents

Abstract

PURPOSE:To make favorable adhesion of polyolefin, which is inexpensive and superior in dielectric characteristics, to a metallic foil and to contrive an improvement in heat resistance, by a method wherein the metallic foil, a specific adhesive film and a fiber are laminated, to which crosslinking treatment is performed. CONSTITUTION:A metallic foil 1, a polyolefin adhesive film 2, glass fiber cloth 3 and a polyolefin sheet 4 are superposed upon one another in order. After those have been integrated through heating and pressurization, crosslinking treatment is performed by holding them within moisture atmosphere. Copper is favorable as a material of the metallic foil and oxygen-free copper is suitable especially for transmission at a high-frequency zone. A copper foil whose surface has been roughed is preferable from a view point of an improvement in adhesion. Then the polyolefin adhesive film is used to make favorable adhesion between the metallic foil and an insulation base material. The glass fiber cloth is indispensable for prevention of a warp or a twist to be generated on a laminated sheet due to a distortion generated at the time of molding processing such as a difference between thermal expansion coefficients or specific heat between those of the metallic foil and insulation base material or in heating-cooling processes.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for manufacturing a polyolefin metal laminate suitable for application to high frequency circuit boards.

[Conventional technology] With the transition to an advanced information society, remarkable technological innovations have been made in various fields, and the fields of electronics and communication industries are no exception, and are said to be the fields where the greatest technological innovations have been made. It is no exaggeration to say that. An example of this is that the frequency band in use is gradually shifting to higher frequency bands, from kilohertz to megahertz and, in recent years, to kilohertz.

Conventionally, laminates made of an insulating base material such as paper-phenol or epoxy glass and metal foil have been most commonly used for wiring boards for electronic circuits. However, since these are inherently inferior in dielectric constant, dielectric loss, and resonance characteristics (quality factor Q), they suffer from disadvantages such as loss of transmission energy, insufficient transmission speed, and increased loss distortion in the high frequency region. .

For wiring boards used in the megahertz or gigahertz bands, it is necessary to select an insulating base material with excellent dielectric constant, conduction loss, and resonance characteristics, and an insulating base material made of fluorine fiber resin has been developed. Ta. However, in addition to being an expensive material, fluorine thread resin has problems in that the processing process for laminating it with metal foil is complicated.

Under these circumstances, laminates using polyolefin as an insulating base material have been attracting attention.

[Problems to be Solved by the Invention] However, polyolefin inherently has poor adhesion to other substances, and when polyester, polyurethane, or epoxy adhesives are used to bond polyolefin and metal foil, The dielectric properties in the high frequency band deteriorate, making it impractical.

Furthermore, since polyolefins soften and melt at relatively low temperatures, resulting in deformation and shrinkage, they are required to withstand high-temperature processes such as soldering of circuit boards.

The present invention has been made based on the above, and aims to provide a method for producing a polyolefin metal laminate that is inexpensive and has excellent dielectric properties, can improve the adhesiveness between the polyolefin and metal foil, and has excellent heat resistance. This is the purpose.

[Means for Solving the Problems] The method for producing a polyolefin metal laminate of the present invention includes sequentially laminating metal foil, polyolefin adhesive film, glass fiber cloth, and water-crosslinkable polyolefin sheet I,
It is characterized in that these are integrated by heating and pressurizing, and then maintained in a moisture atmosphere for crosslinking treatment.

Copper is the most preferable material for the metal foil, and oxygen-free copper is especially suitable for transmission in high frequency bands.

It is preferable that the surface of the copper foil be roughened by anodizing treatment, chemical treatment, alternating current etching treatment, or the like in order to improve adhesiveness. Metal foil materials other than copper include gold,
Silver, platinum, nickel, stainless steel, aluminum, copper alloys (cupronickel, bronze, brass), etc. can also be used upon request.

A polyolefin adhesive film is used to improve adhesion between a metal foil and an insulating base material. Specifically, the side slopes are mainly made of polyolefins such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, and ethylene-ethyl acrylate copolymer. Copolymerization of unsaturated carboxylic acids, graph I・
Examples include copolymerized or blended materials. In this case, since the carboxylic acid content is 1% or less and strongly adheres to the metal, it does not adversely affect the dielectric properties in the high frequency band. In addition to those mentioned above, polyolefins made by crafting polyketones, cricidyl methacrylate, silanes, etc. are also useful.

The glass fiber cloth constitutes the insulating base material together with the polyolefin sheet described below, but there are differences in thermal expansion coefficient and specific heat between the metal foil and the insulating base material, and distortions that occur during the molding process such as heating and cooling. This is essential for preventing warpage and twisting that occurs in laminates due to such factors. The dielectric properties of the glass fiber cloth are also important, and it is preferable to use alkali-free or low-alkali glass that does not contain alkali components such as Na2O, I, and O. There are no particular restrictions on the weaving method of the glass fiber cloth (the number of warp and weft threads, density, number of weaves, and cloth thickness are not particularly limited as long as the laminate does not warp or twist. Furthermore, the surface of the glass fiber cloth may be treated with vinyl silane, amino silane, acrylic silane, etc. in order to improve adhesion to polyolefin sheets and the like.

The water-crosslinkable polyolefin sheet constitutes an insulating base together with glass fiber cloth, and specific materials for the base polymer include α-olefin-based materials such as polyethylene, polypropylene, polybutene-1, and poly-4-methylpentene-1. Polymers, ethylene and propylene, butene-1, pentene-1,4-methylpentene-1, heptene-1,
Examples include copolymers with α-olefins such as hexene-1 and octene-1, ethylene-vinyl acetate copolymers, and ethylene-ethyl acrylate copolymers, which can be used alone or in combination of two or more. good. The water-crosslinkable polyolefin has the above-mentioned base polymer with the general formula RR'
5iY2 (wherein R is a monovalent olefinically unsaturated group bonded to the silicon atom by a silicon-carbon bond and constituted by carbon, hydrogen and optionally oxygen,
Y is a hydrolyzable organic group, R' is a monovalent hydrocarbon group or group Y containing no fatty acid unsaturated group) at a temperature of 140°C or higher, and the half-life at that temperature is The graft reaction was carried out in the presence of a free radical generating compound for 6 minutes or less. in particular,
Manufactured by reacting polyolefin containing 0.5 to 5% of vinyl silane such as vinyltrimethoxysilane and 0.05 to 0.5% of dicumyl peroxide in an extruder at around 200°C according to graph 1. be done. This water-crosslinkable polyolefin is
By contacting with water in the presence of a silanol condensation catalyst such as dibutyltin dilaure-1, a crosslinking reaction occurs and three-dimensionalization of the polymer is achieved.

[Examples of the invention] Example 1 A 35 μm thick copper foil whose surface was etched after rolling oxygen-free copper as a metal foil, and a thick one made of a copolymer of polyethylene and maleic anhydride as a polyolefin adhesive film. A film with a diameter of 0.1 mm and a thickness of 0.1 mm as a glass fiber cloth. ] mm, density (number of warp threads x number of weft threads in 25 mm length) 40 x 32, hand-woven fabric with silane treated surface, density 0.
94-5 high-density polyethylene, 2 parts by weight of vinyltrimethoxysilane, and 0 parts by weight of dicumyl peroxide.
．． 2 parts by weight added to barrel zone 120-220°C
As shown in Fig. 1, metal foil 1-polyolefin-based Adhesive film 2 - glass fiber cloth 3 - water-crosslinkable polyolefin sheet 4 - glass fiber cloth 3 - water-crosslinkable polyolefin sheet 1-4 were stacked in this order, and heated using a flat plate press at 200°C for 10 minutes. They were integrated under pressure to produce a laminate with a thickness of 1.5 mm. Subsequently, dibutyltin dilaure-1 was applied to the surface of the laminate where the metal foil 1 was not present, and the laminate was kept in steam at a vapor pressure of 0.4 kg/cm2 for 20 hours, and slowly cooled to obtain a finished product.

Example 2 A laminate was produced in the same manner as in Example 1, except that the base polymer of the water-crosslinkable polyolefin sheet was polypropylene instead of high-density polyethylene.

Comparative Example 1 A laminate was produced in the same manner as in Example 1, except that a polyester adhesive (based on polyethylene terephthalate) was used instead of the copolymer of polyethylene and maleic anhydride as the material for the polyolefin adhesive film.

Comparative Example 2 A laminate was produced in the same manner as in Example 1, except that a non-crosslinkable sheet made of high-density polyethylene was used in place of the water-crosslinkable polyolefin sheet.

The evaluation results for the laminates of Examples and Comparative Examples are as follows.
As shown in the table. Normal peel strength and solder resistance were measured in accordance with JIS-C-64.81, and dielectric constant and dielectric loss tangent were measured in accordance with JIS-6760.
Measurements were made at a frequency of MHz.

Table 1 [Effects of the Invention] As is clear from the above explanation, according to the present invention, even when polyolefin, which is inexpensive and has excellent dielectric properties, is used for an insulating substrate, adhesiveness with metal foil can be ensured. It also shows excellent heat resistance, making it possible to obtain a polyolefin metal laminate suitable for application to high-frequency circuit boards.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view showing an example of the laminated state of each layer in the present invention. 1: Metal foil 2: Polyolefin adhesive film 3: Glass fiber cloth

Claims (1)

[Claims] (1) Metal foil, polyolefin adhesive film, glass fiber cloth, and water-crosslinkable polyolefin sheet are layered one after another, integrated by heating and pressure, and then held in a moisture atmosphere for crosslinking treatment. A method for producing a polyolefin metal laminate.