JPH098421A - Material for printed-wiring board - Google Patents

Abstract

PURPOSE: To provide an excellent material for printed-wiring board without deteriorating the properties of SPS resin such as low dielectric constant and dielectric loss tangent, low specific gravity etc., regardless of the application of a flame retardant. CONSTITUTION: In relation to the title material for printed-wiring board, a resin composition containing a resin, fibrous filler and flame retardant mainly comprising styrene base polymer having syndiotactic structure contains bubbles whose mean size is smaller than the fibrous diameter of the fibrous filler.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for a printed wiring board used in the fields of electricity and electronics, and particularly to a lightweight and inexpensive printed wiring board material having excellent high frequency characteristics.

[0002]

BACKGROUND OF THE INVENTION Styrenic polymers having a syndiotactic structure (hereinafter referred to as SPS resin) are mainly
For high-speed arithmetic processing because it has advantages such as low dielectric constant and dielectric loss tangent, high heat resistance, low cost compared to other high frequency substrate resin materials, and relatively low specific gravity. , Is widely used as a resin material for printed wiring boards that require excellent high-frequency characteristics, such as those for receiving sanitary broadcasts and for small communication devices. Since flame resistance is required for these printed wiring boards, a flame retardant and a flame retardant aid have been added to the SPS resin for use.

[0003]

In the above-mentioned conventional printed wiring board materials, although a SPS resin is used, a large amount of a flame retardant is added, so that the dielectric constant and the dielectric loss tangent become high. Further, since the flame retardant has a large specific gravity, the specific gravity as a material for a printed wiring board is not much different from the case where other resins are used. The present invention
The present invention has been made in view of the above problems, and an object of the present invention is to provide an excellent printed wiring board without impairing the low dielectric constant, dielectric loss tangent, and low specific gravity of SPS resin, despite the use of a flame retardant. To provide the material.

[0004]

A material for a printed wiring board according to the present invention is a resin composition containing a resin containing a styrene polymer having a syndiotactic structure as a main component, a fibrous filler and a flame retardant. , And the average size of the bubbles is smaller than the fiber diameter of the fibrous filler. It is an aspect of the present invention that the fiber diameter of the fibrous filler is 1 to 20 μm. That is, the present inventors have used an SPS resin having excellent dielectric properties and a low specific gravity as a resin material for a printed wiring board to prevent deterioration of dielectric properties and increase in specific gravity due to addition of a flame retardant in a resin composition. By introducing bubbles, offsetting, or paying attention to further improvement, as a result of various studies on the structure, by making the average size of the bubbles smaller than the fiber diameter of the fibrous filler, The present invention has been completed by finding that a lightweight and inexpensive printed wiring board material having excellent high-frequency characteristics can be obtained without adversely affecting strength.

In the SPS resin used in the present invention, the stereochemical structure is a syndiotactic structure, that is, the main chain formed from carbon-carbon bonds is opposite in side chains to phenyl groups and substituted phenyl groups. The tacticity is quantified by nuclear magnetic resonance ( ¹³ C-NMR method) using isotopic carbon. ^The tacticity measured by the ¹³ C-NMR method is indicated by the abundance ratio of a plurality of continuous constitutional units, for example, diad in the case of two, triad in the case of 3, and pentad in the case of 5. The styrene-based polymer having a syndiotactic structure in the present invention is usually 75% or more, preferably 85% or more in racemic dyad, or 30% or more, preferably 50% or more in racemic pentad. City-containing polystyrene, polyalkylstyrene, polyhalogenated styrene, polyalkoxystyrene, polyvinylbenzoic acid ester, hydrogenated polymers thereof and mixtures thereof, or copolymers containing these as the main components.

Examples of the polyalkylstyrene include polymethylstyrene, polyethylstyrene, polyisopropylstyrene, polytertiarybutylstyrene, polyphenylstyrene, polyvinylnaphthalene, and polyvinylstyrene. As polyhalogenated styrene, polychlorostyrene, polybromostyrene,
Examples include polyfluorostyrene. Examples of the polyhalogenated alkylstyrene include polychloromethylstyrene and the like. Examples of the polyalkoxystyrene include polymethoxystyrene and polyethoxystyrene. Further, as the comonomer component of the copolymer containing these structural units, in addition to the monomers of the styrene-based polymer, ethylene, propylene, butene, hexene, olefin monomers such as octene, diene monomers such as butadiene and isoprene, cyclic Examples include polar vinyl monomers such as olefin monomers, cyclic diene monomers, methyl methacrylate, maleic anhydride, and acrylonitrile. In addition,
Among these, particularly preferable styrene-based polymer,
Examples thereof include polystyrene, polyalkylstyrene, polyhalogenated styrene, hydrogenated polystyrene, and copolymers containing these structural units.

The styrenic polymer having such a syndiotactic structure is prepared, for example, by using a titanium compound and a condensation product of water and a trialkylaluminum as a catalyst in an inert hydrocarbon solvent or in the absence of a solvent. It can be produced by polymerizing a styrene-based monomer (a monomer corresponding to the styrene-based polymer). In addition, regarding polyhalogenated alkyl styrene,
1-46912, these hydrogenated polymers are disclosed in JP-A 1-1785.
It can be obtained by the method described in Japanese Patent Publication No. 05, etc. There is no particular limitation on the molecular weight of this styrene polymer, but the one having a weight average molecular weight of 2,000 or more, preferably 10,000 or more, particularly 50,000 or more is optimal. further,
Regarding the molecular weight distribution, there is no restriction on the width and width, and various kinds can be applied. Moreover, various additives such as a softening agent and a processing aid can be added to these resin components, if necessary.

The printed wiring board material of the present invention requires the use of solder when mounting electronic components and connection with other substrates, and it is necessary to prevent ignition due to temperature rise of components in use. Heat resistance and flame resistance are required, and it is important to add a flame retardant. Although various flame retardants can be mentioned, halogen-based flame retardants and phosphoric acid-based flame retardants are particularly preferable. Examples of halogen-based flame retardants include tetrabromophthalic anhydride, hexabromobenzene, tribromophenylallyl ether, pentabromotoluene, pentabromophenol, tribromophenyl-2,3-dibromopropyl ether, tris (2-chloro-3). -Bromopropyl) -phosphate, octabromodiphenyl ether, decabromodiphenyl ether, octabromobiphenyl, pentachloropentacyclodecane, hexabromocyclodecane, hexachlorobenzene, pentachlorotoluene, hexabromobiphenyl, decabromobiphenyl oxide, tetra Bromobutane, decabromodiphenyl ether, hexabromophenyl ether,
Halogenated polycarbonate oligomers such as ethylene-bis-tetrabromophthalimide, tetrachlorobisphenol A, tetrabromobisphenol A, tetrachlorobisphenol A or tetrabromobisphenol A oligomers, brominated polycarbonate oligomers, halogenated epoxy compounds, polychloro Examples thereof include styrene, halogenated polystyrene such as polytribromostyrene, polydibromophenylene oxide, and bis (tribromophenoxy) ethane. On the other hand, examples of the phosphoric acid flame retardant include ammonium phosphate, tricresyl phosphate, acidic phosphoric acid ester, triphenylphosphine oxide and the like.

Among these flame retardants, polytribromostyrene, polydibromophenylene oxide, decabromodiphenyl ether, bis (tribromophenoxy) ethane, ethylene-bis-tetrabromophthalimide, tetrabromobisphenol A, brominated, among others. Polycarbonate oligomers are preferred. The flame retardant is
The SPS resin and the fibrous filler are added in an amount of 1 to 40 parts by weight, preferably 5 to 35 parts by weight, based on 100 parts by weight in total. Even if the flame retardant is blended beyond this range, the flame resistance is not improved depending on the proportion, and conversely, other mechanical properties are impaired, which is not preferable. If it is less than this range, the effect cannot be obtained.

Further, in the present invention, it is preferable to use a flame retardant auxiliary together with the above-mentioned flame retardant, and by using both in combination, the desired effect can be sufficiently exhibited. Such flame retardant aids include antimony trioxide,
Examples of the antimony flame retardant auxiliary agent include antimony pentaoxide, sodium antimonate, metal antimony, antimony trichloride, antimony pentachloride, antimony trisulfide, and antimony pentasulfide. Other than these, zinc borate, barium metaborate, zirconium oxide and the like can be mentioned, but among them, antimony trioxide is particularly preferable. This flame retardant aid may be added in a proportion of 0.1 to 15 parts by weight, preferably 2 to 10 parts by weight, based on 100 parts by weight of the SPS resin and the fibrous filler in total. However, the effect does not improve according to the ratio, and if it is less than this range, the effect of the flame retardant aid cannot be obtained.

In the present invention, a thermoplastic resin compatible with SPS resin for improving mechanical properties, particularly impact resistance, for example, a styrene polymer having an atactic structure,
A styrene-based polymer having an isotactic structure, polyphenylene ether, styrene-butadiene-styrene copolymer (SBS), styrene-ethylene-butylene-styrene copolymer (SEBS) and the like can be added.

Examples of the reinforcing fibrous filler used in the present invention include whiskers such as glass fiber, carbon fiber, boron, silica and silicon carbide, alumina fiber, ceramic fiber (eg gypsum fiber, potassium titanate fiber). , Magnesium sulfate fiber, magnesium oxide fiber, etc.), organic synthetic fiber (eg, wholly aromatic polyamide fiber, aramid fiber, polyimide fiber, fluororesin fiber, etc.) and the like, and glass fiber and fluororesin fiber are particularly preferable. There is no particular limitation on these shapes, for example, non-woven fabrics such as chopped strands, chopped fibers, continuous long fibers, woven fabrics, swirl-laminated and swirl-laminated needle-punched, powder, milled Fiber etc. are mentioned. Fiber diameter is 1 to 20
μm, preferably 5 to 15 μm. This is because if it exceeds 20 μm, the strength is adversely affected, and if it is less than 1 μm, the specific surface area is too large, and it is difficult to mix until the reinforcing effect is exhibited. These fibrous fillers may be used alone or in combination of two or more.

In the present invention, the mixing ratio of the fibrous filler to the SPS resin is 100 parts by weight of the SPS resin.
The fibrous filler is 20 to 400 parts by weight, preferably 50 to 100 parts by weight. This is because if it is less than this range, sufficient strength cannot be obtained, and if it exceeds this range, the fibrous filler is added with S.
The PS resin could not be sufficiently covered, resulting in voids,
As a result, the bending strength becomes so weak that it cannot be measured, and there is a problem that the through-hole workability is extremely poor.

In the printed wiring board material of the present invention,
The SPS resin composition described above is foamed, and the resin composition contains bubbles having an average size smaller than the fiber diameter of the fibrous filler. The bubbles have the functions of lowering the dielectric constant and the dielectric loss tangent and also reducing the specific gravity. Making the cell size smaller than the fiber diameter of the fibrous filler is important in order not to impair the reinforcing effect of the fibrous filler, and when the cell size greatly exceeds the fiber diameter, the cells wrap the fiber, The area where the resin does not coat the fibers increases, and the strength decreases significantly. Whether or not the size of the bubbles is smaller than the fiber diameter was determined by observing the unit cross section of the object to be measured with an electron microscope, measuring the size of each bubble, and calculating the number average.

As a method for obtaining bubbles of such a size, for example, under pressure, a plastic material to be processed is pre-saturated with a gas having a uniform concentration, and then nuclei of a large number of bubbles are formed. It is proposed to induce the thermodynamic instability rapidly. For example, the material is pre-saturated with gas and kept under pressure at the glass transition temperature. The material is then rapidly exposed to low pressure to form cell nuclei, which further promotes cell growth to a desired size, depending on the desired final density, a foam material with ultra-microscopic pores or cells. To manufacture. The material is then cooled more rapidly to fix the microporous structure. Such techniques increase the bubble density (ie the number of bubbles per unit volume of starting material),
The bubble size can be reduced. In this microporous process, rather than the critical size inherent to the polymer,
The small size of the bubbles allows control of the material density and composition without sacrificing the desired bubble properties. The foam material obtained by this method has an average cell size of 10
Micron order, maximum bubble density is about 1 trillion (10 ⁹ ) pores per cubic centimeter of starting material, and the pore content is 50% or less of the total volume.

A further method of making the microcellular foamed frustric material is to introduce a web of plastic material into an inert gas and allow the gas to diffuse under controlled conditions into the web. The web is reheated at the foaming station to induce foaming. The temperature and time of this foaming process are controlled to obtain the desired properties. This process is designed for continuous production of expanded plastic web material. The cell size in the foam material is in the range of 2 to 9 μm in diameter.

A method for obtaining a smaller cell size is to produce a super-microcellular foam material by feeding a supercritical liquid (ie, gas in its supercritical state) to the material to be foamed. Is. The supercritical fluid acts as a blowing agent in the starting material. Shortly after introducing the supercritical liquid into the starting material, a fully saturated solution of the liquid and the material is formed. If the liquid / material solution contains a sufficient amount of supercritical liquid therein, at a suitably selected temperature and pressure,
Rapid changes in the temperature and / or pressure of the liquid / material system induce thermodynamic instability and cause foaming to form a foamed material. The foamed material thus obtained may have a cell density of several hundred trillion pores per cubic centimeter, an average pore or cell size of less than 1.0 μm, and sometimes less than 0.5 μm.

Any kind of gas can be selected as the gas of the bubbles to be introduced, but CO ₂ , N ₂ , Ar, He and the like are preferable because they are chemically stable as a gas.

[0019]

As described above, by introducing air bubbles into the printed wiring board material of the present invention, the deterioration of the dielectric properties due to the addition of the flame retardant and the increase of the specific gravity are canceled or improved.
By making the average size of the bubbles smaller than the fiber diameter of the fibrous filler, the bubbles do not wrap around the fibers, so that the strength is not deteriorated.

[0020]

EXAMPLES Next, specific embodiments of the present invention will be shown together with comparative examples. [Example 1] It was carried out in the following order. .Preparation of reaction product of trimethylaluminum and water; 17.8 g of copper sulfate pentahydrate (CuSO ₄ .5H ₂ O) in a glass container having an inner volume of 500 ml and substituted with argon.
(200 mmol), toluene (200 ml) and trimethylaluminum (24 ml) (250 mmol), and the mixture was reacted at 40 ° C. for 8 hours. Then, toluene was further distilled off from the solution obtained by removing the solid matter at room temperature under reduced pressure to obtain 6.7 g of a reaction product. The molecular weight of this contact product was 610 as measured by the freezing point depression method.

[0021]. Production of SPS resin; 1 liter of purified styrene in a reaction vessel having an internal volume of 2 liters, 10 mmol of the reaction product obtained above as an aluminum atom, 60 mmol of totylaluminum, pentamethylcyclopentadienyl titanium trimethoxy 0.075 mmol of sodium chloride was added and the polymerization reaction was carried out at 90 ° C. for 1 hour. After completion of the reaction, the catalyst component was decomposed in a methanol solution of sodium hydroxide, and the product was repeatedly washed with methanol and dried to obtain 268 g of a polymer. The weight average molecular weight of the polymer is 1,
When measured by gel permeation chromatography at 130 ° C. with 2,4-trichlorobenzene as a solvent, the weight average molecular weight was 180,000 and the weight average molecular weight / number average molecular weight was 2.53. Further, the melting point and ¹³ C-NMR measurement confirmed that this polymer was polystyrene having a syndiotactic structure.

.. Production of resin compound; 35 parts by weight of flame retardant (polytribromostyrene), 9 parts of flame retardant aid (Sb ₂ O ₃ ) based on 100 parts by weight of SPS resin obtained above
Parts by weight were added, and the mixture was molded into pellets using a single-screw extruder in which the cylinder temperature was set to 290 ° C.

[0023] Introduction of air bubbles and compounding with fibrous filler: The resin compound obtained above was molded from a twin-screw extruder through a T-die to form a sheet having a thickness of 0.2 mm.
This sheet was placed in the chamber of the foaming apparatus, and CO ₂ was supplied at a temperature of 0 ° C. and a pressure of 60 kgf / cm ² . Then the temperature is 43 ℃
And the pressure was adjusted to 210 kgf / cm ² . Here, CO ₂ is in a supercritical state. This state was maintained for 60 minutes to saturate the sheet with CO ₂ in a supercritical state.
Two sheets of this and a glass cloth "# 5150" (trade name, manufactured by Asahi Schwebel) (monofilament fiber diameter: 4.5 µ
m) 3 pieces are piled up alternately and the temperature is 290 ℃ and the pressure is 30kg.
Pressed at f / cm ² for 5 minutes. The sheet is foamed by the heating at this time. Then, it cooled at room temperature for 10 minutes. Thus, a 0.8 mm-thick printed wiring board material was produced. The characteristics obtained are that the average bubble size is about 1.0 μm and the specific gravity is
1.2, relative permittivity of 1.8 at 12 GHz, dielectric loss tangent of 0.0
It was 027. The bending strength was 21.0 kgf / mm ² .

Example 2 The resin compound obtained in Example 1 was passed through a twin-screw extruder so that 100 parts by weight of chopped glass fiber having a fiber diameter of 10 μm was mixed with 100 parts by weight of the compound from the side feeder. Then, the sheet was sent to the above and passed through a T-die to form a sheet having a thickness of 0.2 mm. Place this sheet in the chamber of the foaming machine and
° C., was fed CO ₂ pressure 60 kgf / cm ^2. Then the temperature
The temperature was adjusted to 43 ° C and the pressure was adjusted to 210 kgf / cm ² . Here, CO ₂ is in a supercritical state. This state is 60
After being held for a minute, the sheet was saturated with CO ₂ in a supercritical state. Put these 3 sheets on top of each other and
5150 "(trade name, manufactured by Asahi Schebel) (monofilament fiber diameter: 4.5 μm) are alternately stacked and pressed for 5 minutes at a temperature of 290 ° C. and a pressure of 30 kgf / cm ² , and then cooled at room temperature for 10 minutes. did. The sheet foams due to the heating in this step. Thus, a 0.8 mm-thick printed wiring board material was produced. The properties of the obtained printed wiring board material were such that the average bubble size was about 1.0 μm, the specific gravity was 1.15, the relative dielectric constant at 12 GHz was 1.6, and the dielectric loss tangent was 0.0021. The bending strength was 19.3 kgf / mm ² .

[Comparative Example 1] Two sheets were prepared in the same manner as in Example 1 except that air bubbles were not introduced into the sheets.
A glass wiring material having a thickness of 0.8 mm was produced by alternately stacking three glass cloths. The obtained characteristics have a specific gravity of 1.8,
The relative dielectric constant at 12 GHz was 3.5 and the dielectric loss tangent was 0.0054. The bending strength was 20.4 kgf / mm ² .

[Comparative Example 2] The resin compound obtained in Example 1 was passed through a twin-screw extruder so that chopped glass fibers having a fiber diameter of 30 μm from the side feeder became 100 parts by weight per 100 parts by weight of the compound. Then, 3 parts by weight of a foaming agent ACDA and 2 parts by weight of talc were further mixed, and a 0.4 mm-thick foamed sheet was molded through a T-die. Two sheets of this sheet are piled up, and the temperature
After pressing for 5 minutes at 290 ℃, pressure 30kgf / cm ² ,
After cooling at room temperature for 10 minutes, a 0.8 mm-thick printed wiring board material was obtained. This product had an average cell size of 60 μm and a bending strength of 4.4 kgf / mm ² .

As described above, the printed wiring board material of the present invention contains the flame retardant and the flame retardant auxiliary,
The specific gravity is almost the same as 1.8 of Comparative Example 1 which does not contain bubbles.
It was extremely light at 1.2 and had excellent dielectric properties. Furthermore, in the case of Comparative Example 2 in which the size of the introduced bubbles is larger than the fiber diameter, the bending strength is 21.0 kgf / mm ² , 19.3 kgf / mm in Examples 1 and 2 in which the cell size is smaller than the fiber diameter.
^{2 was} 4.4 kgf / mm ^2, which was extremely small.

[0028]

EFFECTS OF THE INVENTION The printed wiring board material of the present invention has a dielectric property obtained by adding a flame retardant without impairing the excellent dielectric property and low specific gravity of SPS resin by introducing air bubbles into the resin material. The deterioration and the increase in specific gravity were offset, and it was possible to improve further. Then, by making the average size of the bubbles smaller than the fiber diameter of the fibrous filler, it is possible to obtain a lightweight and inexpensive material for a printed wiring board, which is free from deterioration of strength, excellent in high frequency characteristics. By using the material for a printed wiring board of the present invention in a printed wiring board, the weight of the device can be reduced, and the conventional PT
The price was lower than that of FE and PPO substrates, and the product cost could be reduced.

Claims (2)

[Claims] 1. A resin composition containing a resin containing a styrene-based polymer having a syndiotactic structure as a main component, a fibrous filler, and a flame retardant contains air bubbles, and the average size of the air bubbles is the fibrous material. A printed wiring board material characterized by being smaller than the fiber diameter of the filler. 2. The fiber diameter of the fibrous filler is 1 to 20 μm.
The material for a printed wiring board according to claim 1, wherein the material is m.