JPH10130399A - Glass cloth base laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject laminate improve in tracking resistance, suitable as a substrate for electrical insulation boards, esp. printed wiring boards, by using, as base material, a glass cloth comprising glass fiber and provided with an alumina layer on the surface. SOLUTION: This base material is obtained by providing the surface of a glass cloth comprising glass fiber with an alumina coating layer as a layer needing at least tracking resistance. In this case, the glass fiber may be nonalkaline glass commonly used for electrical insulation such as E-glass fiber or C-glass fiber. To provide the alumina coating layer on the surface of the glass fiber, it is preferable to thermally spray the glass cloth with alumina because of simplicity and enabling direct resin impregnation. The alumina coating layer is pref. 3-10μm in thickness. The thermosetting resin to be impregnated in the glass cloth is pref. an epoxy resin. The solvent to be used for preparing a varnish by dissolving the thermosetting resin therein is pref. e.g. ethylene glycol monomethyl ether.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass cloth substrate laminate. The laminate of the present invention is suitable as an electric insulating plate, particularly as a substrate for a printed wiring board.

[0002]

2. Description of the Related Art Glass cloth substrate laminates are used in the field of industrial electronic equipment such as computers, communication equipment, measuring instruments, etc., as electric insulating boards, especially substrates for printed wiring boards. The glass cloth substrate laminate is a laminate using a glass cloth as a base material and a thermosetting resin as a matrix. The glass cloth substrate laminate is obtained by laminating a predetermined number of prepregs obtained by impregnating and drying a thermosetting resin varnish on a glass cloth, and heating and pressing. When used as a printed wiring board,
A predetermined number of prepregs are stacked, copper foil is stacked on both sides or one side, and heated and pressed to produce a copper-clad laminate, and the copper foil is etched to form a circuit. The form of the glass cloth used as the base material includes woven cloth and nonwoven cloth, but nonwoven cloth is rarely used alone, and in combination with woven cloth, the woven cloth is used as the base material of the surface layer, and the base material of the inner layer is used. In many cases, a nonwoven fabric is used as the material. As the thermosetting resin, bisphenol type epoxy resin is generally used from the viewpoint of heat resistance and cost.

[0003]

In recent years, with an increase in the density of wiring, an improvement in tracking resistance has been required. Tracking is a phenomenon in which a resin is carbonized by a minute discharge from a conductor, and the carbonized layer extends to cause a short circuit between the conductors. Bisphenol type epoxy resin is
Since the molecule contains many aromatic rings, tracking tends to occur. Conventionally, in order to improve the tracking resistance of a glass substrate laminate, a mixture of a bisphenol-type epoxy resin with an alicyclic epoxy resin and a mixture of a resin with aluminum hydroxide have been known. However, unlike the paper-based phenolic resin laminate, satisfactory results have not been obtained for the improvement of the tracking resistance of the glass-fabric-based laminate. An object of the present invention is to improve the tracking resistance of a glass cloth substrate laminate.

[0004]

SUMMARY OF THE INVENTION Tracking is a type of stratum breakdown. Therefore, various attempts were made to modify the surface of the glass cloth, and it was found that the formation of an alumina coating layer on the surface of the glass fiber improved the tracking resistance, leading to the present invention.

[0005] The present invention is a glass cloth substrate laminate using, as a substrate, a glass cloth made of glass fiber having an alumina coating layer formed on the surface.

[0006] Since tracking mainly relates to discharge from a conductor circuit, tracking often occurs in a surface layer, and rarely causes trans-layer breakdown. Therefore, in the case of a laminate having a plurality of glass cloth substrates, it is not usually necessary to use a glass cloth having an alumina coating layer formed on all the substrates. In many cases, it is sufficient to use a glass cloth made of glass fibers formed with the above.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as glass fibers, non-alkali glass fibers usually used for electric insulation can be used. For example, E glass fiber, C glass fiber, D glass fiber, S glass fiber and the like can be mentioned. As the form of the glass cloth, any of a woven cloth and a nonwoven cloth is used, but the nonwoven cloth is usually used as a base material of an inner layer, and is often a composite laminate using a woven cloth as a base material of a surface layer.

As a means for forming an alumina coating layer on the surface of glass fiber, a means for spraying alumina on a glass cloth is the simplest and is preferable because it can be impregnated with a resin as it is. In addition, a sol-gel method in which an alumina sol is adhered using aluminum alkoxide as a raw material can also be used.

The thickness of the alumina coating layer to be formed is 0.1
~ 20 µm is preferred. When it is smaller than 0.1 μm, the effect of preventing tracking is reduced, and when it exceeds 20 μm, the substrate tends to be difficult to handle, such as being rigid. For this reason, the thickness of the alumina coating layer is 3
It is more preferable that the thickness be 10 to 10 μm.

The thermosetting resin to be impregnated into the glass cloth of the present invention includes, but is not particularly limited to, resins used for laminated boards, such as epoxy resins, unsaturated polyester resins, vinyl ester resins, and phenol resins. Among them, an epoxy resin is preferably used.

When it is necessary to impart flame retardancy to these resins, a resin containing a halogen element in the resin skeleton is blended. When using an epoxy resin as the resin and compounding an epoxy resin containing a halogen element in the resin skeleton,
From the viewpoint of tracking resistance, of the total resin solid content,
Preferably, the halogen content is 5 to 30% by weight.
More preferably, the content is set to ２０20% by weight. As the flame retardant, a known phosphorus-based or antimony-based flame retardant may be blended.

[0012] In addition to the flame retardant, when it is necessary to increase the viscosity of the varnish and to improve the thermal conductivity, clay, talc, wollastonite, silica, glass, magnesium hydroxide, alumina, calcium aluminate, calcium carbonate, A powder such as aluminum hydroxide is blended as a filler. Among them, aluminum hydroxide is preferable because it has an effect on tracking resistance. The compounding amount of the filler is 60 to 200 parts by weight, preferably 80 to 130 parts by weight, based on 100 parts by weight of the resin component. If the amount is less than 80 parts by weight, the effect of the blending of the filler is not exhibited, and if it exceeds 200 parts by weight, the viscosity of the varnish becomes too high.

A varnish is prepared by dissolving a thermosetting resin and various components to be mixed as required in a solvent, and is applied and impregnated on a glass cloth to form a prepreg. And heat and press to form a copper-clad laminate. These methods can be based on known methods and conditions. The solvent of the varnish is not particularly limited, but ethylene glycol monomethyl ether, N, N dimethylformamide, methyl ethyl ketone and the like are preferably used.

[0014]

【Example】

Example 1 Alumina was sprayed on a glass woven fabric using E glass having a thickness of 0.2 mm and a basis weight of 210 g / m ² to form an alumina coating layer having a thickness of 5 μm.

Bisphenol A type brominated epoxy resin having an epoxy equivalent of 470 g / eq and a bromine content of 21.0% by weight (parts by weight, hereinafter the same), bisphenol A having an epoxy equivalent of 510 g / eq and containing no bromide
Dissolve 40 parts of epoxy resin, 3 parts of dicyandiamide, 0.16 part of 2-ethyl-4-methylimidazole and 90 parts of aluminum hydroxide in a mixed solvent of 25 parts of ethylene glycol monomethyl ether and 25 parts of N, N dimethylformamide. And dispersed to form a varnish.

The varnish was impregnated and dried on the glass woven fabric on which the alumina layer having a thickness of 5 μm was formed so that the solid content was 42% by weight, to obtain a glass woven prepreg.
Eight sheets of this glass woven prepreg are stacked, and copper foil having a thickness of 18 μm is stacked on both outer sides thereof.
Heating and pressurizing for two minutes gave a double-sided copper-clad laminate.

Example 2 A glass nonwoven fabric using E glass having a thickness of 0.4 mm and a basis weight of 75 g / m ² was impregnated with the varnish obtained in Example 1 so that the solid content was 90% by weight. It dried and obtained the glass nonwoven fabric prepreg. This glass non-woven fabric prepreg is laminated three times, the glass woven fabric prepreg obtained in Example 1 is laminated on both outer sides thereof, and a copper foil having a thickness of 18 μm is further laminated on both outer sides thereof, and heated and pressed at 170 ° C. and 3 MPa for 90 minutes. Thus, a double-sided copper-clad composite laminate was obtained.

Comparative Example A double-sided copper-clad laminate was obtained in the same manner as in Example 1 except that a glass woven fabric having no alumina coating layer was used.

The obtained three kinds of laminates were subjected to ASTM
Tracking resistance was examined according to D3638. Table 1 shows the results. The test method is as follows. The copper-clad laminate is etched to form two electrodes with a width of 5 mm with slits at a distance of 0.4 mm. While applying a constant voltage between the electrodes, a 0.1% aqueous solution of ammonium chloride is dropped on the slit at intervals of 30 seconds, and the number of drops when tracking occurs on the test surface is determined. By repeatedly changing the voltage and creating a relationship curve between the voltage and the number of drops, a voltage corresponding to the number of drops = 50 was determined, and the CTI (Compa
passive tracking index) value.

[0020]

[Table 1]

From Table 1, it is clear that the laminate of the present invention, which is based on a glass cloth made of glass fiber having an alumina coating layer formed on the surface, has excellent tracking resistance.

[0022]

According to the present invention, the tracking resistance of the laminate can be improved by using a glass cloth made of glass fiber having an alumina coating layer formed on the surface as a base material.

Claims (1)

[Claims] 1. A glass cloth base laminate comprising, as a base material, a glass cloth made of glass fiber having an alumina coating layer formed on at least a layer requiring tracking resistance.