JPS63315234A - Polyolefin metallic laminated sheet - Google Patents

Abstract

PURPOSE:To enable application of the title sheet to a high-frequency circuit board by improving adhesion between polyolefin superior in dielectric characteristics and a metallic foil, by a method wherein the metallic foil, a polyolefin adhesive film, glass fiber cloth and a polyolefin sheet are superposed upon one another in order, which are integrated through heating and pressurization. CONSTITUTION:A metallic foil 1, a polyolefin adhesive film 2, glass fiber cloth 3 and a polyolefin sheet 4 are superposed upon one another for example, in the order, of the metallic foil 1-polyolefin adhesive film 2-glass fiber cloth 3-polyolefin sheet 4-glass fiber cloth 3-polyolefin adhesive film 2-metallic foil. Then a laminated sheet of about 1.5mm thick is formed by integrating these through heating and pressurizing by a flat plate press. The polyolefin adhesive film 2 is used for making adhesion between the metallic foil 1 and an insulation base material favorable. In this instance, as content of carboxylic acid is 1% or lower and adheres to a metal strongly, bad effect is not given to dielectric characteristics in a high-frequency zone. Then the glass fiber cloth 3 can prevent a warp or a twist to be generated on the laminated sheet due to a difference between thermal expansion coefficients ar specific heat of the metallic foil and insulation base material and a distortion to be generated at the time of molding processing such as heating-cooling processes.

Description

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

``Conventional technology 1: With the transition to an advanced information society, remarkable technological innovations have been made in various fields, and the fields of electronics and communications industries are no exception, and are said to be some of the biggest technological innovations. 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 gigahertz.

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 range. .

For wiring boards used in the megahertz or gigahertz band, it is necessary to select an insulating base material with excellent dielectric constant, conduction loss, and resonance characteristics, and fluoroplastics have been developed as an insulating base material. Ta. However, in addition to being an expensive material, fluororesin 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.

The present invention has been made based on the above, and provides a polyolefin metal laminate that can be applied to high-frequency circuit boards by improving the adhesiveness between inexpensive polyolefin with excellent dielectric properties and metal foil. It is intended for the purpose of providing.

[Means for Solving Problem 1] The polyolefin metal laminate of the present invention is constructed by sequentially overlapping metal foil, polyolefin adhesive film, glass fiber cloth, and polyolefin sheet, and integrating these by heating and pressurizing. This is what I did.

Copper is the most preferred 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, AC etching treatment, etc. to improve adhesion. Metal foil materials other than steel sales 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. Specific materials include polyolefins such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, and ethylene-ethyl acrylate copolymer, as well as inorganic compounds such as maleic anhydride and acrylic acid. Examples include copolymerization, kraft copolymerization, and friends of saturated carboxylic acids. 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 the above, polyolefins such as polyketones, glycidyl methacrylate, and silanes shown in graph 1 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 an alkali-free or low-alkali glass that does not contain an alkali component such as Na2O 20. There are no particular restrictions on the weaving method of glass fiber cloth, and the number of warp and weft threads, density,
The number of weaves and the texture 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 polyolefin sheet constitutes an insulating base material together with glass fiber cloth, and specific materials include α-olefin polymers such as polyethylene, polypropylene, polybutene-1, and poly4-methylpentene-1, ethylene and propylene, Copolymers with α-olefins such as butene-1, pentene-1,4-methylpentene-1, heptene-1, hexene-1, octene-1, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer These may be used alone or in combination of two or more.

[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. Film with a diameter of 0.1 mm, thickness of glass fiber cloth of 0.1 mm, density (number of warp threads x number of weft threads in a length of 25 mm) 40 x 32, plain woven cloth with a silanized surface, high density of 0.945 as a polyolefin sheet Using sheets made of polyethylene molded to a thickness of 1°3 mm, as shown in Figure 1, metal foil 1 - polyolefin adhesive film 2 - glass fiber cloth 3 - polyolefin sheet 4 - glass fiber cloth 3 - polyolefin adhesive A laminate having a thickness of 1.5 mm was manufactured by stacking the film 2 and the metal foil 1 in this order and heating and pressing them together using a flat plate press at 200° C. for 10 minutes.

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

Comparative Example 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.

The evaluation results for the laminates of Examples and Comparative Examples are as follows.
As shown in the table. Normal peel strength is JIS-C-
6481, and the dielectric constant and dielectric loss tangent are J
Measurements were made at a frequency of 30 MHz in accordance with IS-6760.

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 the insulating substrate, adhesiveness with metal foil can be ensured. As a result, a polyolefin metal laminate suitable for application to high frequency circuit boards can be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view showing an example of the laminated state of each layer in the polyolefin metal laminate of the present invention. Metal foil 2: Polyolefin adhesive film 3 Glass fiber cloth 4: Polyolefin sheet

Claims (1)

[Claims] (1) A polyolefin metal laminate, characterized in that a metal foil, a polyolefin adhesive film, a glass fiber cloth, and a polyolefin sheet are sequentially laminated, and these are integrated by heating and pressure.