JP2009073997A - Epoxy resin composition, prepreg and metal-clad laminate using the epoxy resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epoxy resin composition which is preferably used as an insulating material for a printed circuit board, and which has flame retardance and high heat resistance. <P>SOLUTION: The epoxy resin composition including: a brominated epoxy compound having at least two epoxy groups in a molecule; a cyanate ester compound; a hardening catalyst; and a free halogen adsorbent, is used. Zeolite, activated carbon, an ion exchanger, silica gel, and the like are preferably used as the free halogen adsorbent. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to an epoxy resin composition preferably used as an insulating material for a printed wiring board, and more specifically, an epoxy resin composition preferably used for producing a printed wiring board excellent in heat resistance and flame retardancy, and the epoxy resin thereof The present invention relates to a prepreg and a metal-clad laminate using the composition.

  In recent years, electronic devices used in the field of information and communication have been increasing in capacity and speed of signals, and there is a demand for printed wiring boards that have good high-frequency characteristics and can cope with a higher number of layers due to an increase in the number of wires. .

  In a printed wiring board used for such an electronic device, a low dielectric constant (ε) and a low dielectric loss tangent (tan δ) are required in order to maintain reliability in a high frequency region from the MHz band to the GHz band. Conventionally, as a printed wiring board having such electrical characteristics, one using a thermosetting resin composition in which polyphenylene ether (PPE) is blended with an epoxy resin is used for its insulating layer. Such a thermosetting resin composition exhibits a dielectric property superior to that of a normal epoxy resin composition, but other expensive high-frequency substrate materials such as PTFE, BT resin, polyimide resin, etc. There was a problem that heat resistance was low.

  In order to improve such low heat resistance, the following Patent Document 1 and Patent Document 2 include a specific epoxy compound, a low molecular weight phenol-modified polyphenylene ether, and a cyanate compound as an essential component as a curing agent. An epoxy resin composition is disclosed. Such an epoxy resin composition has high heat resistance and also has excellent dielectric properties.

In addition to the above dielectric properties and heat resistance, the epoxy resin composition used for the insulating layer of the printed wiring board is also required to have high flame resistance. In order to impart flame retardancy to such an epoxy resin composition, a method of blending a predetermined amount of a brominated epoxy compound as an epoxy resin component has been widely used.
Japanese Patent Laid-Open No. 10-265669 JP 20007763 A

  Epoxy resin compositions containing a brominated epoxy compound as a resin component and a cyanate compound as a curing agent are heat resistant compared to the case where an acid anhydride or a phenolic curing agent is used as a curing agent. Although the performance is excellent, it is still insufficient as compared with the heat resistance of other high-frequency substrate materials.

  An object of the present invention is to provide an epoxy resin composition capable of maintaining higher heat resistance in an epoxy resin composition containing a brominated epoxy compound as a resin component and containing a cyanate compound as a curing agent. To do.

  As a result of studies for improving heat resistance in an epoxy resin composition containing a brominated epoxy compound as a resin component and a cyanate compound as a curing agent, the present inventors have a brominated epoxy compound. We have obtained some findings that bromine atoms are desorbed at high temperatures to decompose the resin skeleton and reduce the heat resistance of the cured product. From this knowledge, the present invention has been completed.

  That is, the epoxy resin composition of the present invention comprises a brominated epoxy compound having at least two epoxy groups in one molecule, a cyanate ester compound, a curing catalyst, and a free halogen adsorbent. is there. As in the present invention, by containing a free halogen adsorbent in the epoxy resin composition, the adsorbent captures free bromine (bromine ions or bromine radicals) generated from the brominated epoxy compound at high temperatures. In order to suppress the action of decomposing the skeleton, a decrease in heat resistance can be suppressed.

  As the above-mentioned free halogen adsorbent, at least one selected from zeolite, activated carbon, ion exchanger, and silica gel is preferably used.

  Moreover, the said epoxy resin composition is preferable from the point from which a higher dielectric characteristic is acquired, when the number average molecular weight further contains polyphenylene ether of 10,000 or less.

  Moreover, in the said epoxy resin composition, it is preferable that a curing catalyst contains organometallic salt from the point which can maintain higher heat resistance and fluidity | liquidity.

  Moreover, the prepreg of the present invention is obtained by impregnating a fibrous base material with the epoxy resin composition and curing it.

  In addition, the metal-clad laminate of the present invention is obtained by laminating a metal foil on the prepreg and heating and pressing.

  ADVANTAGE OF THE INVENTION According to this invention, the epoxy resin composition excellent in heat resistance and a flame retardance and preferably used for manufacture of a printed wiring board etc. is obtained.

  The kind of brominated epoxy compound having at least two epoxy groups in one molecule used in the present invention is not particularly limited. Specific examples thereof include bromine which is a bromine-substituted product such as bisphenol A type epoxy compound, bisphenol F type epoxy compound, phenol novolac type epoxy compound, dicyclopentadiene type epoxy compound, naphthalene type epoxy compound, biphenyl type epoxy compound, and the like. An epoxy compound is mentioned. These may be used alone or in combination of two or more. Among these, a tetrabromobisphenol A type epoxy compound, which is a bromine-substituted product of a bisphenol A type epoxy compound, is particularly preferably used because it is excellent in flame retardancy and curability.

  The epoxy resin composition of the present invention may further contain an epoxy compound containing no halogen. Specific examples thereof include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, phenol novolac type epoxy compounds, dicyclopentadiene type epoxy compounds, naphthalene type epoxy compounds, biphenyl type epoxy compounds and the like. These may be used alone or in combination of two or more. In these, a dicyclopentadiene type epoxy compound and a naphthalene type epoxy compound are preferably used from the point which gives still higher heat resistance to hardened | cured material.

  The blending ratio of the brominated epoxy compound in the epoxy resin composition of the present invention is such that the bromine content is 5 to 30% by mass, further 10 to 20% by mass in the total amount of the resin component. Is preferable from the viewpoint that sufficient flame retardancy can be maintained. Moreover, as a compounding ratio of the total amount of the epoxy compound including the brominated epoxy compound, 20 to 70% by mass, and further 30 to 60% by mass of the resin component total amount is sufficient with sufficient heat resistance. It is preferable from the viewpoint that mechanical characteristics and electrical characteristics can be maintained.

  The cyanate ester compound used in the present invention is not particularly limited as long as it is a compound having two or more cyanate groups in one molecule. Specific examples thereof include 2,2-bis (4-cyanatophenyl) propane, bis (3,5-dimethyl-4-cyanatophenyl) methane, and 2,2-bis (4-cyanatophenyl). And aromatic cyanate ester compounds such as ethane and derivatives thereof. These may be used alone or in combination of two or more.

  The cyanate ester compound is a component that acts as a curing agent for an epoxy resin and forms a rigid skeleton. This gives a high glass transition point (Tg). Moreover, since the viscosity is low, the high fluidity of the resin varnish obtained can be maintained.

  Cyanate ester compounds also self-polymerize with each other in the presence of a curing catalyst such as an organic metal salt. In this self-polymerization reaction, cyanate groups react with each other to form a triazine ring, whereby the polymerization reaction proceeds. Such a self-polymerization reaction also contributes to an improvement in heat resistance.

  As the blending ratio of the cyanate ester compound, 20 to 70% by mass, and further 30 to 60% by mass of the resin component is obtained, and sufficient heat resistance is obtained, and the impregnation property to the substrate is excellent. It is preferable from the point that a crystal | crystallization hardly precipitates also in a resin varnish.

  The epoxy resin composition of the present invention preferably further contains polyphenylene ether having a number average molecular weight of 10,000 or less. Even if such polyphenylene ether is obtained by a polymerization reaction, it is obtained by redistributing a high molecular weight PPE by heating it in a solvent such as toluene in the presence of a phenolic compound and a radical initiator. It may be.

  In addition, since the polyphenylene ether obtained by the said redistribution reaction has the hydroxyl group derived from the phenol type compound which contributes to hardening at both ends of a molecular chain, it is preferable from the point which can maintain still higher heat resistance. Moreover, the polyphenylene ether obtained by polymerization is preferable from the point of showing excellent fluidity.

  The number average molecular weight of the polyphenylene ether is 10,000 or less, preferably 2000 to 4000. When the number average molecular weight exceeds 10,000, the fluidity is deteriorated, the reactivity with the epoxy group of the epoxy compound is also lowered, and the curing reaction takes a long time or is not taken into the curing system and is not reacted. As a result, the glass transition temperature decreases and sufficient heat resistance cannot be expected.

  The molecular weight of the polyphenylene ether can be adjusted by adjusting the amount of the phenolic compound used in the redistribution reaction. That is, the greater the amount of the phenolic compound, the lower the molecular weight.

  As the high molecular weight PPE subjected to the above redistribution reaction, commercially available products such as commercial products can be used, and typical examples thereof include poly (2,6-dimethyl-1,4-phenylene ether). . In addition, the phenolic compound used in the redistribution reaction is not particularly limited. For example, a polyfunctional phenol having two or more phenolic hydroxyl groups in the molecule such as bisphenol A, phenol novolak, cresol novolak, and the like. System compounds are preferably used. These may be used alone or in combination of two or more.

  The blending ratio of the polyphenylene ether is preferably 20 to 60% by mass, more preferably 30 to 50% by mass in the resin component, from the viewpoint of sufficiently imparting excellent dielectric properties.

  The curing catalyst used in the present invention is a catalyst that promotes the reaction between the epoxy compound and polyphenylene ether added as necessary, and a cyanate ester compound that is a curing agent. Acids, stearic acid, acetylacetonate, naphthenic acid, organic acids such as salicylic acid, organic metal salts such as Zn and Cu, tertiary amines such as triethylamine and triethanolamine, 2-ethyl-4-imidazole, 4-methylimidazole And imidazoles. These may be used alone or in combination of two or more. Among these, organometallic salts, particularly zinc octoate, are preferably used.

  The blending ratio of the curing catalyst is not particularly limited. For example, when an organic metal salt is used, it is preferably about 0.005 to 5 parts by mass with respect to 100 parts by mass of the resin component, and imidazoles are used. It is preferable that it is about 0.01-5 mass parts with respect to 100 mass parts of resin components.

  The free halogen adsorbent used in the present invention is not particularly limited as long as it is a powdery substance that traps free halogen (halogen ions or halogen radicals) by ion exchange reaction, physical adsorption, or chemical adsorption. Specific examples thereof include zeolites such as synthetic zeolite and natural zeolite, activated carbon, silica gel, chemically synthesized inorganic ion exchangers and ion exchange resins, and the like. Examples of such commercially available products include inorganic ion exchanger IXE series manufactured by Toagosei Co., Ltd., molecular sieve manufactured by Union Showa Co., Ltd., and the like. These may be used alone or in combination of two or more.

  The blending ratio of the free halogen adsorbent is not particularly limited as long as it is a sufficient amount for capturing halogen ions and the like, but is 1 to 30 parts by mass, and further 5 to 10 parts by mass with respect to 100 parts by mass of the resin component. Is preferably from the viewpoint of sufficiently maintaining the fluidity of the resulting resin composition.

  Such a free halogen adsorbent is present dispersed in the resin varnish. The particle diameter at the time of dispersion is preferably about 0.01 to 50 μm, more preferably about 1 to 10 μm.

  A flame retardant may be further added to the epoxy resin composition of the present invention in order to impart flame retardancy. Specific examples of the flame retardant include, for example, halogen-based flame retardants such as brominated flame retardants and phosphorus-based flame retardants. In order to further suppress the generation of halogen, phosphorus-based flame retardants are preferably used. It is done.

  An inorganic filler may be added to the epoxy resin composition of the present invention as necessary for the purpose of increasing the dimensional stability during heating or increasing the flame retardancy.

  Specific examples of the inorganic filler include silica, alumina, talc, aluminum hydroxide, magnesium hydroxide, titanium oxide, mica, aluminum borate, barium sulfate, calcium carbonate, and the like.

  The blending ratio of the inorganic filler is 10 to 100 parts by mass, and further 20 to 50 parts by mass with respect to 100 parts by mass of the resin component, without reducing the fluidity and adhesion to the metal foil. Moreover, it is preferable from the viewpoint of improving dimensional stability.

  In the epoxy resin composition of the present invention, as long as the effects of the present invention are not impaired, other components that are blended in the normal epoxy resin composition as necessary, for example, a heat stabilizer, an antistatic agent, an ultraviolet absorber, You may mix | blend a flame retardant, dye, a pigment, a lubricant, etc.

  In the epoxy resin composition of the present invention, it is preferable that all of the resin components are dissolved in the resin varnish. Such a resin varnish is prepared as follows, for example.

  An epoxy compound, a cyanate ester compound, and a polyphenylene ether used as necessary are each dissolved in a predetermined amount of a solvent such as toluene. At this time, heating may be performed as necessary. In addition, when dissolving, it is preferable to use an epoxy compound and a cyanate ester compound that are soluble in a solvent such as toluene at room temperature from the viewpoint that precipitates and the like are not easily generated in the resin varnish.

  Furthermore, when adding an inorganic filler as required, it is dispersed using a ball mill, a bead mill, a planetary mixer, a roll mill or the like until a predetermined dispersion state is obtained.

  Then, a curing catalyst and a free halogen adsorbent are further added to the resin varnish in which the resin component is dissolved, and the mixture is stirred so as to be uniform. In this way, a resin varnish is prepared.

  Examples of a method for producing a prepreg using the obtained resin varnish include a method of impregnating a fibrous base material with the resin varnish and then drying.

  Examples of the fibrous base material include glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, polyester nonwoven fabric, pulp paper, linter paper and the like. When a glass cloth is used, a laminate having excellent mechanical strength can be obtained, and a flat glass processed glass cloth is particularly preferable. The flattening can be performed, for example, by continuously pressing the glass cloth with a press roll with an appropriate pressure and compressing the yarn flatly. In addition, as a thickness of a base material, the thing of 0.04-0.3 mm can generally be used.

  Impregnation is performed by dipping or coating. Impregnation can be repeated a plurality of times as necessary.In this case, the impregnation can be repeated using a plurality of solutions having different compositions and concentrations, and finally the desired composition and resin amount can be adjusted. is there.

  The base material impregnated with the resin varnish is heated at a desired heating condition, for example, 80 to 170 ° C. for 1 to 10 minutes, whereby a semi-cured (B stage) prepreg is obtained.

  As a method for producing a metal-clad laminate using the prepreg thus obtained, one or a plurality of the prepregs are stacked, and a metal foil such as a copper foil is stacked on both upper and lower surfaces or one surface thereof. By heating and pressing to laminate and integrate, a double-sided metal foil-clad laminate or a single-sided metal foil-clad laminate can be produced. The heating and pressing conditions can be appropriately set depending on the thickness of the laminated board to be produced, the type of the resin composition of the prepreg, etc. For example, the temperature is 190 to 210 ° C., the pressure is 3.5 to 4.0 Pa, and the time Can be 120 to 150 minutes.

  In addition, the epoxy resin composition of this invention forms a strong crosslinked structure when the epoxy group of a epoxy compound and a cyanate ester compound react in the hardening reaction. A cured product of the cyanate ester compound is excellent in electric characteristics and heat resistance. In addition, by incorporating a free halogen adsorbent and capturing bromine released from the brominated epoxy compound, decomposition of the cured product can be suppressed and high heat resistance can be maintained.

  By forming a circuit by etching the metal foil on the surface of the laminate thus produced, a printed wiring board having a conductor pattern as a circuit on the surface of the laminate can be obtained. The printed wiring board thus obtained is excellent in dielectric characteristics and has high heat resistance.

  The present invention will be described more specifically with reference to the following examples. However, the scope of the present invention is not limited to these examples.

  First, a production example of the low molecular weight polyphenylene ether used in this example is shown.

(Production example: Production of polyphenylene ether having a number average molecular weight of 4000 by redistribution reaction)
250 g of toluene was put in a 2000 ml flask equipped with a stirrer and a stirring blade. While controlling the flask at an internal temperature of 90 ° C., 90 g of high molecular weight PPE (PPE having a number average molecular weight of 25000 (“Noryl 640-111” manufactured by GE Plastics, Inc.)), 3.6 g of bisphenol A, benzoyl peroxide A solution of polyphenylene ether having a number average molecular weight of 2500 (solid content concentration: 28% by mass) was prepared by adding 3.6 g and continuing the reaction for 2 hours, and the number average molecular weight was determined by gel permeation chromatography. It is the value of styrene conversion measured by (GPC).

(Examples 1-7, Comparative Examples 1-3)
First, the raw materials used in this example are shown together.
<Epoxy compound>
-Tetrabromobisphenol A type epoxy compound, MW800 Epicron 153 (Dainippon Ink Chemical Co., Ltd.)
・ Epicron HP7200 (Dainippon Ink Chemical Co., Ltd.) which is a dicyclopentadiene type epoxy compound and has a number average molecular weight (MW) 550
-Bisphenol F type epoxy compound, MW350 Epicron 830S (manufactured by Dainippon Ink & Chemicals, Inc.)
<Cyanate ester compound>
2,2-bis (4-cyanatophenyl) propane (Bandy made by Lonza Japan)
<Curing catalyst>
・ Zinc octoate (Dainippon Ink & Chemicals, Inc., zinc concentration 18%)
<Free halogen adsorbent>
・ Zirconium, bismuth inorganic ion exchanger IXE-6107 manufactured by Toagosei Co., Ltd.
・ Zeolite HiSiv3000 manufactured by Union Showa Co., Ltd.
<Inorganic filler>
・ Spherical silica (SiO ₂ ) SO25R (manufactured by Admatex)

[Preparation of resin varnish]
Toluene was heated to 90 ° C., and after adding resin components such as an epoxy compound, a cyanate ester compound, and polyphenylene ether so as to have a blending ratio shown in Table 1, the mixture was stirred for 30 minutes to be completely dissolved. . Further, a curing catalyst, a free halogen adsorbent, and an inorganic filler were added and dispersed with a ball mill to obtain a resin varnish.
Next, the obtained resin varnish was impregnated into glass cloth (“WEA116E” manufactured by Nitto Boseki Co., Ltd.), and then heated and dried at 150 ° C. for 3 to 5 minutes to obtain a prepreg.
Next, 6 sheets of the obtained prepregs were stacked and laminated, and copper foils (F2-WS 18 μm manufactured by Furukawa Circuit Foil Co., Ltd.) were disposed on both outer layers, respectively, under conditions of a temperature of 220 ° C. and a pressure of 3 MPa. By heating and pressing for 2 hours, a copper-clad laminate having a thickness of 0.75 mm was obtained.

  The following evaluation was performed using the obtained prepreg and copper clad laminate.

<Heat-resistant>
In accordance with the standard of JIS C 6481, the copper-clad laminate cut out to a predetermined size was left in a thermostat set at a predetermined temperature for 1 hour and then taken out. And the processed test piece was observed visually and the highest temperature when the swelling did not generate | occur | produce was calculated | required.

<Flame retardance>
The flame retardancy of the copper clad laminate cut out to a predetermined size was determined by performing a combustion test according to the UL 94 combustion test method.

<Dielectric properties>
According to the standard of JIS C 6481, the dielectric constant and dielectric loss tangent at 1 MHz were obtained.

<Coefficient of thermal expansion (CTE)>
In accordance with the standard of JIS C 6481, the thermal expansion coefficient in the Z-axis direction was determined. The measurement conditions were a temperature increase rate of 5 ° C./min and a temperature range of 75 to 125 ° C.

  From Table 1, the copper clad laminated board obtained using the epoxy resin composition which mix | blended the free halogen adsorbent of Examples 1-7 concerning this invention is maintaining flame retardance V-0, The heat resistance was also maintained at 260 ° C. or higher. Further, Example 5 containing PPE had a low dielectric constant and dielectric loss tangent, and showed excellent dielectric properties. On the other hand, the heat resistance of Comparative Example 1 in which no free halogen adsorbent was blended was low.

Claims (6)

  An epoxy resin composition comprising a brominated epoxy compound having at least two epoxy groups in one molecule, a cyanate ester compound, a curing catalyst, and a free halogen adsorbent.   The epoxy resin composition according to claim 1, wherein the free halogen adsorbent is at least one selected from zeolite, activated carbon, ion exchangers, and silica gel.   The epoxy resin composition according to claim 1 or 2, further comprising a polyphenylene ether having a number average molecular weight of 10,000 or less.   The epoxy resin composition according to any one of claims 1 to 3, wherein the curing catalyst contains an organic metal salt.   A prepreg obtained by impregnating a fibrous base material with the epoxy resin composition according to any one of claims 1 to 4 and curing it.   A metal-clad laminate obtained by laminating a metal foil on the prepreg according to claim 5 and heating and pressing.