JPH0719951B2 - Insulating layer forming paste composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has a low dielectric constant (hereinafter abbreviated as ε) and is useful for adhesive layers, thickness adjusting layers, overlay layers, etc. in circuit boards and multilayer circuit boards. The present invention relates to an insulating layer forming paste composition used.

[Prior Art] In recent years, in the field of electronics, a plastic insulating layer has been used in an extremely wide range of applications such as a circuit board in combination with a conductor layer, and has various required characteristics. Of these, ε is used for the purpose of increasing the signal propagation speed.
It is necessary to develop an insulating layer having a low electric field, and recently, ε is required to be 3 or less. As a method of forming an insulating layer, there has been a method of forming an insulating layer from a thermosetting resin paste composition, but ε of the insulating layer is greatly affected by ε of the resin itself, and a conventional thermosetting resin is used. When used, ε cannot be lowered.

As a means for forming a plastic insulating layer having a low ε,
Fluorine resin, polyethylene resin, polybutadiene resin,
A method of using a thermoplastic resin having a low ε such as a polysulfone resin as a film has been studied. However, such an insulating layer is inferior in multilayer formability, dimensional change, drilling workability, heat resistance, etc., and a highly reliable circuit board itself has not been obtained.

[Problems to be Solved by the Invention]

INDUSTRIAL APPLICABILITY The present invention can form an insulating layer having a low ε of 3 or less and having excellent adhesion to other layers, heat resistance, moisture resistance, water resistance, etc., and can be processed into a circuit board. It is an object to provide a possible paste composition.

[Means for Solving the Problems]

The present invention relates to a thermosetting resin varnish containing an epoxy-modified polybutadiene, an epoxy resin, a carboxylic acid anhydride and a radical polymerization initiator as main components and having a maximum particle diameter of 50 μm or less with respect to 100 parts by weight of the resin component. 10 to 200 parts by weight of plasma surface treated fluororesin powder is added, and the solid content of the thermosetting resin and the fluororesin is 20% by weight.
The present invention relates to an insulating layer forming paste composition obtained by adding and mixing an epoxy group-containing silane coupling agent of ˜100 mol PPM.

The epoxy-modified polybutadiene may be any of polybutadiene having an epoxy group attached to the main chain and terminals, and the epoxy resin may be a general-purpose epoxy resin such as bisphenol A type or alicyclic type, tetrabromobisphenol A type, or dibromobisphenol. A flame-retardant epoxy resin such as A type can be used.

Carboxylic anhydrides include chlorendic anhydride, methylbutenyl tetrahydrophthalic anhydride, alkenyl succinic anhydride, and 5- (2,5-dioxotetrahydrofuryl) -3.
Examples thereof include methyl 3-cyclohexene-1,2 dicarboxylic acid anhydride, and the radical polymerization initiators include organic peroxides such as dicumyl peroxide, t-butyl perbenzoate, t-butyl peroxylaurate and benzoyl peroxide. Oxides are examples. To make these varnishes, one or more organic solvents such as dimethylformamide, methyl isobutyl ketone, and methyl cellosolve are used.

The fluororesin powder used in the present invention includes tetrafluoroethylene resin, tetrafluoroethylene-6 fluoropropylene copolymer resin, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin powder, and the like. A plasma-treated product is used.

As a method of plasma treatment, there is a method of external electrode / internal electrode due to the positional relationship between the electrode and the reactor, and there is a method of using capacitive coupling / inductive coupling / waveguide in the power supply method.
The power supply frequency ranges from DC to GHz band, and any method is possible. In order to uniformly plasma-treat the entire powder charged in the reactor, it is necessary that the powder be agitated in the reactor during the treatment.

The maximum particle diameter of the fluororesin powder is preferably 50 μm or less, more preferably 20 μm or less in terms of the roughness of the inner wall of the through hole when the circuit board including the insulating layer produced using the paste of the present invention is drilled.

If the particle size of the fluororesin powder is large, the inner wall roughness of the insulating layer at the time of through hole becomes large. If the inner wall roughness of the through hole is large, chemical resistance, plating resistance and electrical characteristics are adversely affected.

The composition of the plasma-treated fluororesin powder added to the resin varnish is 10 to 200 parts by weight of the plasma-treated fluorine resin powder with respect to 100 parts by weight of the uncured resin mixture.

If the amount is 10 parts by weight or less, the effect of lowering the ε is small, and if the amount is 200 parts by weight or more, the function of the thermosetting resin as a binder is deteriorated, and the strength and appearance are deteriorated. Particularly, 50 to 180 parts by weight is preferable.

It is important to uniformly disperse the fluororesin powder in a varnish consisting of a mixture of resins.

Epoxy group-containing silane coupling agents include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethylmethoxysilane, and the like, with respect to the solid content of the thermosetting resin and the fluororesin combined. 20 to 10
An addition amount of 0 mol PPM is desirable.

If it is 20 mol PPM or less, the adhesive effect is small, and if it is 100 mol PPM or more, the electric performance is deteriorated. Regarding the addition of the silane coupling agent, it is important to uniformly disperse it in the paste. The order of addition may be either in the varnish when the thermosetting resin varnish is prepared or at the same time when the fluororesin powder is added.

As a method for applying the obtained paste, there is a method such as roll coater / bar coater / screen printing. After that, the resin is cured only by heating or under heat and pressure at atmospheric pressure or vacuum to form an insulating layer.

[Action]

Polybutadiene has a low ε, but is inferior in colorability and heat resistance. By using the epoxy-modified polybutadiene having an epoxy group added to the main chain and the terminal and mixing the epoxy resin, the adhesiveness and heat resistance are improved while maintaining the property of low ε. The epoxy resin can be made flame-retardant by using a bromide, and the addition of the fluororesin powder further promotes the reduction of ε, and ε can be 3 or less. Since the fluororesin is non-polar, the addition of this reduces the adhesiveness of the paste. In order to suppress this decrease, the surface of the fluororesin powder is activated by plasma treatment.

The epoxy group-containing silane coupling agent can improve the adhesiveness between the paste-copper foil and the fluororesin-thermosetting resin.

〔Example〕

Example 1 Epoxy-modified polybutadiene having 90% 1,2 bonds and an epoxy equivalent of 550, brominated bisphenol A type epoxy resin, 5
-(2,5-Dioxotetrafuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic acid anhydride and dicumyl peroxide were mixed and dissolved in methyl isobutyl ketone and dimethylformamide in the composition shown in Table 1. Then, a varnish having a resin content of 58.3% by weight was prepared.

To the varnish, 58.3 parts by weight of a tetrafluorinated ethylene resin powder having a maximum particle size of 20μ treated with plasma and 21 parts by weight of methyl cellosolve were added, and further 1 part by weight (30 mol PPM) of γ-glycidoxypropylmethylmethoxysilane was added. The mixture was mixed with a commercially available homogenizer at 10,000 rpm for 5 minutes to obtain a paste composition.

Plasma treatment of tetrafluoroethylene resin powder is 13.56MHz
Was used for the external electrode method using Ar as a gas and a vacuum degree of 0.01 torr and an electric power of 100 W for 60 minutes. The inside of the plasma treatment reactor was stirred using a stirrer.

Screen-print this composition on 35μm thick copper foil and
After drying for 0 minutes, the two sheets of copper foil / coating layer are put together so that the coating layer is on the inside. Temperature 170 ° C Pressure 30 kg / cm ² , time 2 hours 3
It was pressed for 0 minutes to obtain a double-sided copper clad plate with a total thickness of 130 μm.

The dielectric constant, dielectric loss tangent, and peel strength of the copper clad plate were measured according to JIS-C-6.
It was evaluated according to 481.

Example 2 The procedure of Example 1 was repeated except that the amount of γ-glycidoxypropyltrimethoxysilane added was 2 parts by weight (60 mol PPM).

Comparative Example 1 Same as Example 1 except that γ-glycidoxypropyltrimethoxysilane was not added.

Comparative Example 2 Same as Example 1 except that 3 parts by weight (120 mol PPM) of γ-glycidoxypropyltrimethoxysilane was used.

Table 2 shows the evaluation results of the examples and the comparative examples.

[Effects of the Invention] The insulating layer obtained from the insulating layer-forming paste composition of the present invention has a lower ε than an insulating layer made of a conventional paste composition, and additionally the amount and type of fluororesin. By changing, ε can be adjusted arbitrarily.

Furthermore, the insulating layer-forming paste composition of the present invention has very excellent adhesiveness and water resistance.

A circuit board including an insulating layer made of the paste-like composition for forming an insulating layer of the present invention can be subjected to drilling, plating, etching, soldering, etc., like a board made of a normal laminated plate.

In addition, when a brominated epoxy resin is used, it is possible to impart flame retardancy to the insulating layer formed of the paste composition.

Therefore, the paste-like composition for forming an insulating layer of the present invention is applied to an inner layer surface including, for example, a signal circuit and dried to form an insulating layer as a semi-cured layer, and a plurality of these or other outer layers are formed. It is most suitable for use in which the insulating layer serves as a thickness adjusting layer when a multilayer circuit board is obtained by stacking layers together and heating and pressing.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01B 3/44 N 9059-5G

Claims (1)

[Claims] 1. A thermosetting resin varnish containing an epoxy-modified polybutadiene, an epoxy resin, a carboxylic acid anhydride and a radical polymerization initiator as main components, and having a maximum particle size of 50 μm or less per 100 parts by weight of the resin component. Yes, adding 10 to 200 parts by weight of fluororesin powder that has been subjected to plasma surface treatment,
A paste composition for forming an insulating layer, which is obtained by adding 20 to 100 mol PPM of an epoxy group-containing silane coupling agent to a solid content obtained by combining the thermosetting resin and the fluororesin and mixing them.