JP2003013002A - Epoxy resin varnish for resin substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin varnish enabling to produce a resin substrate having a low thermal expansion coefficient and a high glass transition temperature and having extremely improved thermal characteristics. SOLUTION: This epoxy resin varnish for the resin substrate is characterized by dispersing silica ultra fine particles having <=2.0 μm mean particle diameter D50 and <=5.0 μm 100% equivalent diameter D100, and not essentially forming a structured configuration, into the epoxy resin. It is preferable that the silica ultra fine particles are surface-treated with a silane coupling agent and further the silica ultra fine particles are dispersed into the epoxy resin under a pressure of 50-350 Mpa.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin varnish for a resin substrate, and more particularly to an epoxy resin varnish suitable for producing a resin substrate such as a printed wiring board, which has improved thermal characteristics.

[0002]

2. Description of the Related Art In recent years, along with the progress of high-density mounting of printed wiring boards, improvements in various characteristics such as low thermal expansion and high glass transition temperature of resin substrates have been demanded. There is a method of impregnating a glass nonwoven fabric with an epoxy resin varnish containing silica, which is smaller than the resin. However, if the silica loading is increased in order to simultaneously achieve low thermal expansion and high glass transition temperature,
Not only does the impregnation operation into the glass nonwoven fabric become difficult because the viscosity of the resin composition increases and the fluidity decreases, but silica particles are secondarily aggregated to cause defects such as voids in the resin substrate. In order to solve this problem, for example, the average particle diameter D50
Of 5 to 10 μm and a 100% equivalent diameter D100 of 40 μm or less and a small amount of finely divided silica having an average particle diameter of 1 μm or less are proposed in combination (Japanese Patent Laid-Open No. 9-2911).
No. 60).

However, the average particle diameter is 5 to 10 μm.
Silica tends to settle during storage of the epoxy resin varnish and a silica concentration difference easily occurs, and it is difficult to recover it even by re-stirring, and the silica adhesion amount on the glass non-woven fabric surface varies and the surface smoothness is impaired. . On the other hand, fine silica particles having an average particle size of 1 μm or less are likely to aggregate due to their morphology, the polarity of silanol groups, or hydrogen bonds,
Poor dispersion occurs in the epoxy resin varnish, and the effect of suppressing void generation does not appear as expected, and rather the distribution on the surface of the nonwoven fabric becomes uneven.

A method is known in which the surface of silica is treated with a coupling agent to improve the dispersibility of silica and improve the thermal characteristics (coefficient of thermal expansion and glass transition temperature). Composite of silica particles and epoxy resin is indispensable. When compounding epoxy resin and fine silica, it is necessary to form a particle surface structure that constrains the epoxy resin layer, so an integral blend in which a coupling agent is added later to the epoxy resin varnish filled with fine silica. Although a method is known, since particles of finely divided silica are bonded and aggregated with each other, it is difficult for the coupling agent added later to uniformly coat the surface of each particle. If the coupling agent causes non-uniform coating, the viscosity of the varnish increases and the fluidity decreases, making it difficult to impregnate a glass nonwoven fabric and reducing the effect of improving the thermal characteristics.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object thereof is to improve the fluidity of an epoxy resin varnish containing silica and to bond and aggregate silica particles in the varnish. Is to be significantly reduced, and thermal characteristics such as low thermal expansion and high glass transition temperature of a resin substrate such as a printed wiring board are improved.

[0006]

That is, according to the present invention, the average particle diameter D50 is 2.0 μm or less and the 100% equivalent diameter D1.
00 is 5.0 μm or less, and an ultrafine silica powder that does not substantially form a structure structure is dispersed in an epoxy resin. In the present invention, it is preferable that the ultrafine silica powder is surface-treated with a silane coupling agent,
Further, it is preferable to disperse ultrafine silica powder in the epoxy resin under a pressure of 50 to 350 MPa.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below.

The ultrafine silica powder used in the present invention has an average particle diameter D50 of 2.0 μm or less and a 100% equivalent diameter D1.
00 is 5.0 μm or less, and it is necessary that substantially no structure structure is formed. Average particle size D50
Is more than 1.0 μm or 100% equivalent diameter D100 is 3.0 μ
If it is more than m, the interaction between the surface of the ultrafine silica powder and the epoxy resin will be reduced, and not only the effect of improving the thermal characteristics will be insufficient, but also the silica concentration will settle during storage of the epoxy resin varnish and a silica concentration difference will occur It becomes difficult to recover even by re-stirring, and the silica adhesion amount on the surface of the glass non-woven fabric varies to impair the surface smoothness.

In the present invention, "substantially not forming a structure structure" is defined as follows: the sphericity of the particles observed by TEM is less than 0.9.
Specifically, it is preferable that 20 or more arbitrarily selected particles are captured by the image analyzer and displayed, and the displayed value is 0.9 or more. As the image analysis device, for example, "SPICCA-II" manufactured by Nippon Avionics Co., Ltd. is used.

In TEM (transmission electron microscope) observation, ultrafine silica particles are dispersed and photographed at a predetermined magnification (100,000 to 1,000,000 times depending on the size of particles) to observe the formation of a structure. It is done by image analysis. As a method for dispersing ultrafine silica, for example, an extremely small amount of sample is ultrasonically dispersed in an acetone solvent, and the diluted solution is suction-filtered with a membrane filter to dry the powder in a dispersed state. After that, the powder as it is attached to the filter is TEM.
Observe.

The particle size is measured by a laser scattered light method. An example of the equipment is a particle sizer manufactured by Coulter (Model LS-230 type). When measuring the average particle diameter D50 or the 100% equivalent diameter D100, pure water or ethanol is used as the dispersion medium, and ultrasonic waves are applied to disperse the sample.

The ultrafine silica powder is obtained by throwing silicon particles into a high temperature field formed by a chemical flame or an electric furnace to spheroidize while causing an oxidation reaction (for example, Japanese Patent No. 1568168), and a silicon particle slurry in a flame. It can be produced by a method of spheroidizing while spraying on and oxidizing reaction. In the vapor phase high temperature pyrolysis method of silicon tetrachloride, since the manufactured silica ultrafine powder has a structure structure,
Not suitable for the present invention.

The silane coupling agent used in the present invention does not need to be special, and general products are sufficient. Examples thereof include γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane,
Examples thereof include N-phenyl-γ-aminopropyltrimethoxysilane. Further, these compounds may be used as they are, or may be hydrolyzed to form a partial condensate, or two or more kinds may be used simultaneously. The silane coupling agent may be used in an amount necessary to coat the surface of the silica ultrafine powder, and specifically, it is 0.05 to 10 parts by mass with respect to 100 parts by mass of the silica ultrafine powder. .

As a treatment method with a silane coupling agent, a conventional means can be adopted. For example, there are a spray method of directly spraying the silane coupling agent, a solution method of dissolving the silane coupling agent in water or an organic solvent, and impregnating it with ultrafine silica powder. The former is preferable, and a method in which a silane coupling agent is sprayed in an air stream at a stage of a temperature of 50 to 350 ° C. from the production of silica ultrafine powder to the collection thereof is particularly preferable. Can be significantly suppressed.

The epoxy resin used in the present invention is one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, cresol novocrack type epoxy resin, alicyclic epoxy resin and the like. The epoxy equivalent of the epoxy resin is 100 to 500.
0, especially 150 to 600 is preferred.

The epoxy resin varnish usually contains an epoxy resin, or an epoxy resin and a curing agent therefor as essential components. If necessary, a solvent, a curing accelerator for promoting the reaction between the epoxy resin and the curing agent, and the like may be contained.

As the curing agent, dicyandiamide, diaminodiphenylmethane, polyfunctional phenols such as phenol novolac and cresol novolac, and the like are used. As the solvent, alcohol solvents such as methanol and ethanol, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone are used. Two or more kinds of curing agents or solvents may be used in combination.

An example of the compounding composition of the epoxy resin varnish of the present invention is 5 to 60 parts by mass of ultrafine silica powder per 100 parts by mass of the epoxy resin.

In order to disperse the ultrafine silica powder in the epoxy resin, it is preferable to use an apparatus called a high pressure homogenizer. The basic structure of the high-pressure homogenizer is composed of a high-pressure generator that pressurizes the epoxy resin varnish and a diaphragm mechanism. A high-pressure pump generally called a plunger pump is preferably used as the high-pressure generator. The high-pressure pump is available in a series type, a double type, a triple type, etc., and as the power, there are types such as pneumatic, electric, hydraulic, etc., but the epoxy resin varnish is 50-350MP.
It is preferable that the pressure can be applied to a. When such a high-pressure homogenizer is used, the efficiency of dispersion is remarkably increased, and the epoxy resin is extremely stable in a short time compared with the case where dispersion is performed using a conventional media-medium-type disperser. You can get a varnish.

Examples of trade names of the high-pressure homogenizer include "Ultimizer" manufactured by Sugino Machine Ltd., "Nanomizer" manufactured by Nanomizer, "Microfluidizer" manufactured by Microfluidics, and "Nanomaker" manufactured by Miracle.

In order to manufacture a resin substrate using the epoxy resin varnish of the present invention, for example, a method of manufacturing a resin substrate by impregnating a glass cloth substrate with the epoxy resin varnish and laminating and molding the fiber substrate is generally used. Used for.

[0022]

[Examples] Examples and comparative examples of the present invention will be further described below.

In the furnace for producing ultrafine silica powder, a double-tube structure LPG-oxygen mixed burner is provided at the furnace top so that an internal flame and an external flame can be formed. A two-fluid nozzle for slurry injection is attached. Then, the slurry is injected into the flame from the center of the two-fluid nozzle and the oxygen is injected into the flame from the surroundings. The flame is formed by injecting an LPG-oxygen mixed gas for forming an outer flame and forming an inner flame from the pores of the respective injection ports of the double-tube burner, and the amount of LPG and oxygen gas. The flame condition is adjusted by the control of. The heat-treated product that has passed through the flame is sent to a collection system by a blower.

Metallic silicon powder (average particle size 10.5μ
m) 30 parts (mass parts, the same applies hereinafter) and 70 parts of water are mixed to prepare an aqueous slurry (solid content concentration 20%), and the mixture is heated from the center of the two-fluid nozzle into the flame (temperature about 1900 ° C.).
It was injected at a rate of 0 kg / hour, and the generated ultrafine silica powder was collected by a bag filter.

Example 1 85 parts of a liquid epoxy resin (YD-128), 30 parts of a solvent (methyl ethyl ketone) and 15 parts of silica ultrafine powder were stirred and premixed. Using a simple kneading machine (trade name "Awatori Kentaro AR-360M" manufactured by Shinky Co., Ltd.),
Kneading was performed for 10 minutes at a rotation speed of 600 rpm and an orbital rotation speed of 2000 rpm, and the viscosity (at 1 rpm) was measured. In addition, the sedimentation stability was measured by measuring the sedimentation component generated after standing for 1 month, and shown by mass% with respect to the initial silica content. The solvent was removed from the epoxy resin varnish obtained by kneading with a vacuum drier, and 4.88 g (Wako Pure Chemical Industries, Ltd. special grade reagent) of a curing agent 4,4′-diaminodiphenylmethane (DDM) was added to 20 g of this, and 5 A vacuum desorption method was performed for a minute, and the mixture was poured into a tetrafluoroethylene resin mold (5 mm × 5 mm × 20 mm). Then, curing was performed at 150 ° C. for 1 hour and then at 200 ° C. for 2 hours, and the coefficient of thermal expansion from room temperature to 250 ° C. was measured.

Example 2 A high-pressure homogenizer (trade name "Ultimizer" manufactured by Sugino Machine Co., Ltd.) was used instead of kneading the preliminary mixture with a simple type kneader, except that the pre-mixture was dispersed (kneaded) 5 times at a pressure of 150 MPa. In the same manner as in Example 1, a cured product was produced, and its coefficient of thermal expansion was measured.

Example 3 A silane coupling agent (γ-glycid manufactured by Shin-Etsu Chemical Co., Ltd.) was used in a pipe section at a temperature of about 270 ° C. while the produced ultrafine silica powder was pneumatically transported to a collection system (bag filter) by a blower. Xypropyltrimethoxysilane "KBM-40
3 ") was sprayed to produce silica ultrafine powder treated with a silane coupling agent according to Example 1, and a cured product was produced in the same manner as in Example 1 except that this was used. The coefficient of thermal expansion was measured. As the silane coupling agent, a mixture of 100 parts of water and 2.5 parts was used as 0.5 parts of silane coupling agent per 100 parts of ultrafine silica powder.
It was sprayed so as to have a ratio of parts.

Example 4 A cured product was produced in the same manner as in Example 2 except that the silica ultrafine powder treated with the silane coupling agent produced in Example 3 was used. It was measured.

Example 5 The solid content concentration of the aqueous slurry of metallic silicon powder was 65%.
Silica ultrafine powder was produced in the same manner as in Example 2 except that the above was used. A cured product was produced in the same manner as in Example 2 except that this silica ultrafine powder was used, and the thermal expansion coefficient thereof was measured.

Example 6 The solid content concentration of an aqueous slurry of metallic silicon powder was 65%.
A silica ultrafine powder treated with a silane coupling agent was produced in the same manner as in Example 4 except that the above was used. A cured product was produced in the same manner as in Example 4 except that the silica ultrafine powder treated with the silane coupling agent was used, and the coefficient of thermal expansion thereof was measured.

Comparative Example 1 A cured product was produced in the same manner as in Example 1 except that a commercially available ultrafine silica powder (trade name "Aerosil 130" manufactured by Nippon Aerosil Co., Ltd.) was used, and the coefficient of thermal expansion thereof was measured. did.

Comparative Example 2 Example 2 except that "Aerosil 130" was used.
A cured product was produced in the same manner as in, and the coefficient of thermal expansion was measured.

Comparative Example 3 "Aerosil 130" was placed in a mixer and 2000 rp
The mixture was stirred at m and maintained in a fluidized state, and a silane coupling agent (γ-glycidoxypropyltrimethoxysilane “KBM-403” manufactured by Shin-Etsu Chemical Co., Ltd.) was sprayed on the mixture, and then heat-treated at 150 ° C. for 1 hour, Silica-coupling ultrafine powder was obtained. A cured product was produced in the same manner as in Example 1 except that this silica ultrafine powder was used, and the coefficient of thermal expansion thereof was measured.

Comparative Example 4 Example 2 except that the silane-coupling treated "Aerosil 130" prepared in Comparative Example 3 was used.
A cured product was produced in the same manner as in, and the coefficient of thermal expansion was measured.

The above results are shown in Table 2, and the characteristics of the ultrafine silica powder are shown in Table 1.

[0036]

[Table 1]

[0037]

[Table 2]

As is clear from the comparison between Examples 1 to 6 and Comparative Examples 1 to 4, the epoxy resin varnish for resin substrate of the present invention has highly dispersed silica particles, and the silica particles are bonded together. Excellent sedimentation stability because aggregation is extremely unlikely to occur. As a result, the resin substrate such as a printed wiring board manufactured by using the resin is remarkably improved in various characteristics such as a lower coefficient of thermal expansion than conventional products.

[0039]

EFFECTS OF THE INVENTION According to the present invention, the bonding / aggregation of silica particles in an epoxy resin varnish is remarkably small, and a resin substrate produced using this has a low coefficient of thermal expansion and a high glass transition temperature, The thermal characteristics are extremely improved.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4J002 CD051 CD061 DJ016 FB136                       FB146 FD016 FD140 GQ01                 4J038 DA051 DA052 DB031 DB032                       DB061 DB071 DB072 HA446                       JB07 JB18 JC30 KA03 LA06                       NA11 NA14 PA07 PA19 PB09                       PB11 PC02

Claims (3)

[Claims] 1. An average particle diameter D50 of 2.0 μm or less, 1
An epoxy resin varnish for a resin substrate, characterized in that ultrafine silica powder having a 100% equivalent diameter D100 of 5.0 μm or less and substantially not forming a structure structure is dispersed in an epoxy resin. 2. The epoxy resin varnish for a resin substrate according to claim 1, wherein the ultrafine silica powder is surface-treated with a silane coupling agent. 3. The epoxy resin varnish for resin substrate according to claim 1 or 2, wherein ultrafine silica powder is dispersed in the epoxy resin under a pressure of 50 to 350 MPa.