JPS63315233A - Manufacture of polyolefin metallic laminated sheet - Google Patents

Abstract

PURPOSE:To contrive an improvement in manufacturing efficiency by improving adhesion between polyolefin superior in dielectric properties and a metallic foil, by laminating the metallic foil, a polyolefin adhesive film, glass fiber cloth and a crosslinkable polyolefin sheet in order and they are integrated through heating and pressurization. CONSTITUTION:A metallic foil 1, a polyolefin adhesive film 2, glass fiber cloth 3 and a crosslinkable 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- crosslinkable polyolefin sheet 4-glass fiber cloth 3-polyolefin adhesive film 2-metallic foil 1. Then after passing them through a hot roll 6 of a preheating tank 5, they are integrated by passing them through a rotary pressure roll 7 and formed into the laminated sheet of about 1.5mm thick. The glass fiber cloth 3 can prevent a warp or a twist to be generated on the laminated sheet due to a distortion to be generated at the time of molding processing such as heating-cooling processes. As the polyolefin sheet 4 becomes hard to melt thermally due to use of the same crosslinked beforehand, it becomes possible to perform continuously heating and pressurizing operations at the time of monolithic molding, and manufacturing efficiency can be improved as compared with that of press molding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing 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 considered to be the most technologically innovative. 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 mechahertz and, in recent years, to gigahertz.

Conventionally, laminates made of insulating substrates such as paper-phenol or epoxy glass and metal foils have been most commonly used for wiring boards for electronic circuits. Due to poor loss and resonance characteristics (quality factor Q), disadvantages such as loss of transmission energy, insufficient transmission speed, and increase in loss distortion occur in the high frequency region.

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. 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.

In addition, since polyolefin softens and melts at relatively low temperatures, press molding is the only way to integrally mold it with metal foil, which poses a problem in production efficiency.

The present invention has been made based on the above, and aims to provide a method for manufacturing a polyolefin metal laminate that is inexpensive and has excellent dielectric properties, can improve the adhesiveness between polyolefin and metal foil, and can improve manufacturing efficiency. There is something to be said.

Means for Solving Problem 1] The method for producing a polyolefin metal laminate of the present invention involves sequentially stacking metal foil, polyolefin adhesive film, glass fiber cloth, and crosslinked polyolefin sheet, and heating and pressurizing these layers. It is characterized by being integrated.

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, alternating current etching treatment, or the like in order to improve adhesiveness. 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 mainly polyolefins such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, and ethylene-ethyl acrylate copolymer, as well as maleic anhydride and acrylic acid. Examples include those obtained by copolymerizing, graft copolymerizing, or blending unsaturated carbonic 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 grafted with polyketones, glycidyl methacrylate, silanes, etc. are also useful. The polyolefin adhesive film may be crosslinked or non-crosslinked, but it is preferable to use a crosslinked film in order to improve heat resistance. The gel fraction in the case of crosslinking is 30 to 7
0% is preferable, and if the gel fraction exceeds 70%, adhesiveness tends to decrease. In addition, the film thickness is O, 1mm
As long as it is below, even if the solder is melted by heating, it will not affect shrinkage or deformation, so it may be non-crosslinked.

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 warping and twisting that occur 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 alkaline components 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, inventory, etc. are not particularly limited as long as the laminate does not warp or twist. Further, 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 crosslinked polyolefin sheet constitutes an insulating base material together with glass fiber cloth, and specific materials for the base polymer include α-olefin-based materials such as polyethylene, polypropylene, poly7ten-1, and poly4-methylpentene-1. Polymers, copolymers of ethylene and alpha olefins such as propylene, butene-1, pentene-1,4-methylpentene-1, heptene-1, hexene-1, octene-1, ethylene-vinyl acetate copolymers, Examples include ethylene-ethyl acrylate copolymer, and these may be used alone or in combination of two or more. By using a polyolefin sheet that has been cross-linked in advance, it is difficult to melt under heat (this makes it possible to continuously perform heating and pressing operations during integral molding using rolls, which is faster than press molding). This will greatly improve manufacturing efficiency.

The crosslinking may be chemical crosslinking by adding organic peroxide or the like, crosslinking by irradiation with ionizing radiation such as an electron beam, or water crosslinking by grafting silane and bringing it into contact with moisture. With chemical crosslinking, it is difficult to crosslink medium-high density polyethylene and polypropylene due to the reaction temperature of organic peroxide, and with crosslinking by radiation irradiation, it is difficult to apply to collapsing type polypropylene, so water crosslinking is preferred in the present invention. It is.

The crosslinking method by water crosslinking is based on the above-mentioned base polymer having the general formula RR'SiY, where R is bonded to the silicon atom by a silicon-carbon bond and is composed of a monovalent compound composed of carbon, hydrogen and optionally oxygen. olefinically unsaturated group, Y is a hydrolyzable organic group, and R' is a monovalent hydrocarbon group or group Y containing no fatty acid unsaturated group) at 140°C or higher. grafting reaction in the presence of a free radical-generating compound with a half-life of 6 minutes or less at a temperature of It is something. As a specific example of the graft reaction, 0.5 to 5% of vinylsilane such as vinyl trime I xysilane or vinyltriethoxysilane and 0.0% of dicumyl peroxide are used.
．． Polyolefin containing 05-0.5% at 200°C
One example is a graft reaction in a nearby extruder.

[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, a thickness of 0.1 mm as a glass fiber cloth, a density (number of warp threads x number of weft threads in a length of 25 mm) 40 x 32, a plain woven cloth whose surface is silane treated, a density of 0.94 as a crosslinked polyolefin sheet.
A mixture of 100 parts by weight of high-density polyethylene, 2 parts by weight of vinyltrimethoxysilane, and 0.2 parts by weight of dicumyl peroxide was added to an extruder with a barrel zone of 120 to 220°C, a head of 210°C, and a die of 21°C. The grafted product was molded into a 1.3 mm thick sheet, coated with siftyltin dilaure-1.The vapor pressure was 0.
Each sheet was crosslinked by being kept in water vapor at 4 kg/crn2 for 20 hours. As shown in FIG.
Glass fiber cloth 3 - Polyolefin adhesive film 2 -
The metal foils 1 were stacked one on top of the other in this order, heated by passing through a heating roll 6 in a preheating tank 5, and then passed through a rotating pressure roll 7 to be integrated, thereby continuously manufacturing a laminate with a thickness of 1.5 mm.

Example 2 A laminate was prepared in the same manner as in Example 1, except that the polyolefin adhesive film was a pre-crosslinked film with a gel fraction of 40%, and the base polymer of polyolefin seam 1 was polypropylene instead of high-density polyethylene. was manufactured.

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 and solder resistance are measured in accordance with JIS-C-6481, and dielectric constant and dielectric loss tangent are 30 M in accordance with JIS-6760.
Measurements were made at a frequency of Hz.

Table 1 [Effects of the Invention] As is clear from the explanation below, the present invention makes it possible to improve the adhesion between inexpensive polyolefin with excellent dielectric properties and metal foil, and to improve manufacturing efficiency. Become.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of an embodiment of the present invention. 1: Metal foil 2: Polyolefin adhesive film 3. Glass fiber cloth 4: Crosslinked polyolefin sheet 5: Preheating tank 6: Heat roll 7: Pressure roll

Claims (1)

[Claims] (1) A method for producing a polyolefin metal laminate, which comprises sequentially laminating metal foil, polyolefin adhesive film, glass fiber cloth, and crosslinked polyolefin sheet, and integrating these by heating and pressurizing.