JPS63283181A - Laminate for printed wiring board - Google Patents

Abstract

PURPOSE:To facilitate the selection of dielectric characteristics responsive to utility by combining a fluorine resin layer containing silica fiber and a fluorine resin layer containing no silica fiber. CONSTITUTION:A laminate having at least one layer of fluorine resin containing silica fiber and at least one layer of fluorine resin containing no silica fiber and containing a metal layer at least outermost layer in some cases is provided. The resin layers use those with excellent dielectric characteristic, and the fluorine resin containing the silica fiber is obtained by impregnating fluorine resin solution or dispersion solution with silica fiber assembly, drying solvent and removing it. The laminate contains at least one layer of fluorine resin containing silica fiber and at least one layer of fluorine resin containing no silica fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a laminate for a printed wiring board used in child devices and the like.

[Prior art and its problems] Conventionally, fluororesin laminates for printed wiring boards are made by impregnating polytetrafluoroethylene with glass cloth made of alkali-free glass (for example, as described in JIS R3413) and firing it. Layer the required number of films,
Furthermore, it is known that copper foil is provided on both sides, and these are manufactured by heating and pressing.

However, although polytetrafluoroethylene has excellent dielectric properties at high frequencies, alkali-free glass has poor dielectric properties compared to polytetrafluoroethylene. It has been difficult to make the dielectric properties, especially the dielectric loss tangent, sufficiently low.

[To solve the problem - L step here This invention was made to improve the dielectric properties of printed wiring boards at high frequencies, especially the dielectric loss tangent (tan δ), and includes at least one layer of fluororesin containing silica fibers. at least one layer of fluororesin containing no silica fibers, and optionally with a small outermost layer.
The present invention relates to a laminate for a printed wiring board, which is a laminate including a metal layer.

Examples of the fluororesin used in the silica fiber-containing fluororesin layer in the present invention include polytetrafluoroethylene, tetrafluoroethylene-perfluorovinylether copolymer, tetrafluoroethylene-hexafluoroethylene copolymer, and tetrafluoroethylene-ethylene copolymer. Although various fluororesins such as polymers can be used without limitation, tetrafluoroethylene-perfluorovinyl ether copolymer is preferred because of its excellent interlayer adhesion, and in order to improve the electromagnetic properties of the laminate. Polytetrafluoroethylene is preferred.

The fluororesin used for the fluororesin that does not contain silica fibers may be the same as the various fluororesins described above, and is preferably polytetrafluoroethylene, which has excellent dielectric properties.

The silica fiber preferably has a silicon dioxide content of about 98 to 99 wt%, but is not limited to this range. Silica fibers may be dispersed in the fluororesin as single fibers, but from the viewpoint of strength, it is preferable to use silica fiber aggregates.

The shapes of silica fiber aggregates are cross-like, mat-like,
It may be in any form such as paper, but matte or paper is preferable from the viewpoint of drill pressability, and cross is preferable from the viewpoint of strength. Cross-shaped silica fibers are usually used with a unit weight of 25 to 200 g/m2.
03/m2, but is not limited to these ranges.The manufacturing method of silica fiber is not limited at all, but the dimensional stability of the fluororesin containing silica fiber is Silica fibers made by the sol-gel direct spinning method and having a dogleg-shaped cross-sectional shape are preferable to the melting method because of their good quality.

The silica fiber-containing fluororesin in the present invention can be prepared by impregnating a silica fiber aggregate with a solution or dispersion of the fluororesin and drying and removing the solvent, or by integrating the fluororesin powder and silica fibers by pressure and heating, or By pressurizing and integrating molten two-component resin and silica fiber, it is possible to obtain a product in which silica fibers are dispersed in a fluororesin, or a silica fiber aggregate impregnated with a fluororesin. The content of silica fiber in the silica fiber-containing fluororesin is approximately 1 to 50w, which is less when emphasis is placed on dielectric properties, and more when emphasis is placed on strength.
t%, preferably from 5 to 25 wt%.

The laminate of the present invention includes at least one layer of a fluororesin containing silica fiber and at least IFf! of a fluororesin that does not contain silica fibers. However, the reason why these are combined is that if only layers of fluororesin containing silica fibers are laminated, there is no freedom in construction and the attraction properties cannot be sufficiently improved. That is,
The dielectric characteristics can be considerably improved by changing from alkali-free glass cloth etc. to silica fiber, but by combining fluororesin which does not contain silica fiber, the dielectric characteristics can be further improved. This is because it is possible to easily create products with special characteristics. The thickness of one fluororesin layer containing silica fiber is 0.01
~0.50 mm, preferably 0.03~0.1 mm, and one fluororesin layer containing no silica fibers.
The value is 0.01 to 0.5, preferably 0.03 to 0.
1■■, but is not limited to this range.

The combination of the silica fiber-containing fluororesin layer and the silica fiber-free fluororesin layer is arbitrary.
For example, one layer may be alternately laminated, or several layers may be laminated in blocks. In addition, a metal layer such as copper foil, aluminum foil, or iron-based alloy foil may be provided on at least one of the outermost layers. In the case of a three-dimensional shape, the metal layer of the wiring circuit portion may be provided by electroless plating or the like instead of laminating metal foil such as copper foil.

The laminate of the present invention can be obtained by pressurizing and heating each of the layers using a multistage press that operates discontinuously, or by continuously pressurizing and heating between endless belts. The pressure and heating conditions may vary depending on the number of layers to be laminated, the content of silica fiber in the fluororesin, etc., but usually 1 to 100 kg.
/cm2.250-450℃, preferably 5-40kg
/cm2, preferably from a range of about 360 to 400°C.

The printed wiring board laminate of the present invention is particularly dielectric, that is, has excellent dielectric constant and dielectric loss tangent, and is therefore suitable as a low dielectric constant substrate for communications and computers.

[Example code] Embodiments of the present invention will be explained below.

Example 1 Silica fiber cloth (plain weave, unit weight 80g1-2
) was impregnated with polytetrafluoroethylene dispersion (Asahi Fluoropolymer (a), AD-1) and dried.
It was fired at 80° C. for 10 minutes to obtain a resin-containing polytetrafluoroethylene-impregnated silica fiber cloth with Q50 wt%. (12 pots thick) 6 sheets of this and 50 l thick tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer film (Toyoflon PFA, Toshishiku Co., Ltd.)
Laminate 7 sheets (films) alternately, make the same film on both sides, and then layer 35mm thick electrolytic copper foil on the outside, heat under pressure at 365℃ 10kg/c2 for 60 minutes and laminate. I got a body.

Example 2 Impregnated cloth was made in the same manner as in Example 1, and 6 sheets of this and 5 sheets of polytetrafluoroethylene cutting film with a thickness of 50 mm were laminated alternately so that the impregnated cloth was on the outside.
Further, on the outside thereof, a tetrafluoroethylene-perfluorovinylether copolymer film with a thickness of 50 JL similar to that in Example 1 and an electrolytic copper foil with a thickness of 35 JL were laminated.
A laminate was obtained by pressurizing and heating at 10 kg/c Layer 2 for 60 minutes.

Comparative Example 1 E-glass m-fiber cloth (plain weave unit weight 80 g/cm2)
A polytetrafluoroethylene-impregnated E-glass fiber cloth with a resin content of 80 wt% was obtained by impregnating, drying, and baking seven times with polytetrafluoroethylene disperge (Asahi Fluoropolymer Co., Ltd.'A D-1). I got it. (Thickness: 15JL) Laminated 6 pieces of this, with a thickness of 35JL on both sides.
Laminated electrolytic copper foil for pot, 380℃, 20kg/cm2
A laminate was obtained by applying pressure and heating for 80 minutes.

The laminates obtained in Examples 1 and 2 and Comparative Example 1 were
The dielectric constant and dielectric loss tangent (IMHz) were measured based on Ei481 and were as follows.

Dielectric constant (@) Dielectric loss tangent (tan δ) Example 1
2.45 < lXl0-5 Example 2 2
．． 43 <lXl0 Comparative Example 1 2.80
15 , it can also maintain the required strength.

By arbitrarily combining the proportions of the silica fiber-containing fluororesin layer and the silica fiber-free fluororesin layer, dielectric properties can be easily selected depending on the application.

Claims (3)

[Claims] (1) At least one fluororesin containing silica fiber
A laminate for a printed wiring board, the laminate having at least one layer of a fluororesin containing no silica fiber, and optionally including a metal layer on at least one of the outermost layers. (2) The laminate for a printed wiring board according to claim 1, wherein the silica fiber-containing fluororesin layer is a layer formed by impregnating a silica fiber aggregate with a fluororesin. (3) The laminate for a printed wiring board according to claim 1, wherein the silica fiber aggregate is a silica fiber cloth.