JP5716698B2 - Resin sheet, laminated board and printed wiring board - Google Patents

Description

  The present invention relates to a resin sheet containing an epoxy resin having a mesogenic skeleton having a high thermal conductivity, and further to a laminated board and a printed wiring board using the resin sheet. More specifically, the resin sheet provides a laminated board and a printed wiring board having high thermal conductivity and excellent insulating properties.

  In various module products on which high heat-generating electronic components such as LEDs, power devices, thyristors, and CPUs are mounted on the board, the amount of heat generation increases due to the trend toward lighter, thinner and smaller electronic devices and fine wiring and high-density mounting. It has been following. The high calorific value reduces the efficiency, reliability, lifespan, etc. of the electronic components, thereby degrading the performance of the module product itself. Therefore, many attempts have been made to improve the heat dissipation performance of the module by imparting thermal conductivity to the printed wiring board constituting the module product.

  In particular, in printed wiring boards, attempts have been actively made to provide a highly heat conductive resin substrate by imparting high heat conductivity to a resin substrate excellent in industrial convenience. The resin substrate is a composite material, and the main material constituting it is a resin material and a ceramic material called filler dispersed therein. In general, high thermal conductivity is achieved by increasing the content of a filler having a thermal conductivity larger than that of the resin in the composite material. However, an increase in the amount of filler may greatly reduce the formability of the resin sheet as a precursor of a printed wiring board or a laminated board and the insulation, which is an important characteristic of the printed wiring board.

  Therefore, in recent years, as a raw material for printed wiring board materials from the viewpoint of industrial convenience, the low thermal conductivity of the most widely used epoxy resin itself has been improved, minimizing the increase in filler, and combining Many studies have been made to improve the heat conduction of the entire material. More specifically, the study of increasing the thermal conductivity of epoxy resins has been made most by introducing a resin skeleton called mesogen. (Patent Documents 1 to 3)

  In Patent Document 4, a resin sheet made of an epoxy resin composition in which an epoxy resin having a mesogenic skeleton and a high thermal conductive filler are combined to give practical thermal conductivity, and a laminated board or printed wiring board using the sheet are disclosed. There is disclosure. In Patent Document 5, in order to achieve both the high thermal conductivity and the handleability of the resin sheet, a resin sheet, a laminate and a printed wiring board comprising a resin composition in which a thermoplastic resin is used in combination with an epoxy resin having a mesogenic skeleton. Disclosure is made.

  The epoxy resin having a highly heat-conductive mesogen skeleton disclosed in Patent Document 5 is semi-cured or cured at the time of molding into a resin sheet, a laminate and a printed wiring board, and contains an epoxy resin known in the art and a curing accelerator It is used as a composition. Further, the resin sheet is manufactured by uniformly impregnating or coating a fiber base material or a base material with an epoxy resin composition containing a solvent which becomes a precursor to a varnished cured product.

  Then, the resin sheet is dried by heat and becomes semi-cured. And the resin sheet is shape-hardened and a laminated board and a printed wiring board are obtained. And in order to obtain the characteristic as an electrically insulating material represented by the dielectric breakdown voltage, the resin sheet used for the resin board and the printed wiring board has been calculated | required that it is homogeneous.

JP 2009-19150 A JP 2006-76263 A JP 2006-82370 A JP 2007-224269 A JP 2009-203261 A

  However, in the homogeneous resin sheet, the orientation of the epoxy resin having a mesogen skeleton contained therein cannot be sufficiently obtained, and the thermal conductivity of the laminated board or printed wiring board, which is a cured product of the resin sheet, is sufficient. There was a problem that it was not demonstrated.

  Accordingly, an object of the present invention is to provide a resin sheet that can obtain a laminated board and a printed wiring board having electrical insulation and high thermal conductivity (1.00 W / (m · K) or more). It is.

  The present inventors have found that it is possible to provide a resin sheet that can obtain a laminated board and a printed wiring board having electrical insulation and high thermal conductivity.

  The resin sheet of the present invention includes a first phase and a second phase, the second phase is dispersed in the first phase, and the first phase and the second phase include an epoxy resin having a mesogenic group, The epoxy resin content of the second phase is greater than that of the first phase.

  With this resin sheet, it is possible to obtain a laminated board and a printed wiring board that have electrical insulation properties and retain high thermal conductivity (1.00 W / (m · K) or more).

  The resin sheet of the present invention is characterized in that a volume ratio of the second phase to a total volume of the first phase and the second phase is 10 vol% or more and 83 vol% or less. Thereby, the laminated board and printed wiring board which have this resin sheet can obtain still higher heat conductivity and high electrical insulation.

  Furthermore, the resin sheet of the present invention preferably contains a curing accelerator in the resin sheet and is a latent curing accelerator. Thereby, the laminated board and printed wiring board which have this resin sheet can obtain still higher electrical insulation.

  Furthermore, in the resin sheet of the present invention, the latent curing accelerator is preferably an inclusion catalyst. Thereby, even higher electrical insulation can be obtained with the laminate and the printed wiring board having the resin sheet.

  Furthermore, the laminate of the present invention is preferably characterized by being formed by heating and pressing the resin sheet as a whole or a part of the insulating layer. Since such a laminated board is equipped with the resin sheet which has the said characteristic, it can hold | maintain high thermal conductivity and high electrical insulation.

  Furthermore, the printed wiring board of the present invention is characterized by having an insulating layer made of the resin sheet as a whole layer or a partial layer. Since such a printed wiring board is provided with the resin sheet which has the said characteristic, it can hold | maintain high thermal conductivity and high electrical insulation.

  Provided is a resin sheet capable of obtaining a laminated board and a printed wiring board that retain high thermal conductivity and high electrical insulation.

The schematic diagram of the resin part of the resin sheet which concerns on this embodiment. The schematic diagram which has a cured film of the 2nd phase surface of the resin part of the resin sheet which concerns on this embodiment. Schematic diagram of inclusion compounds. The schematic diagram of a laminated board. The schematic diagram of a printed wiring board.

  Hereinafter, the present invention will be described in detail using embodiments. However, the present invention is not limited to the embodiment.

  The resin sheet in the present embodiment preferably contains an epoxy resin having a mesogen skeleton. Two or more of these may be used in combination. Epoxy resins having these mesogenic skeletons have a chemical structure with a continuous aromatic ring, and thus have a planar structure. Therefore, in the curing process, that is, in the process of forming a laminated board or printed wiring board in which the resin sheet is a cured product. Orientation and higher order structure are formed to achieve high thermal conductivity of the epoxy resin itself. By increasing the thermal conductivity of the epoxy resin itself, the thermal conductivity of a laminated board or printed wiring board that is a composite material of a resin and an inorganic material can be greatly improved.

  The resin according to this embodiment is preferably a compound having a mesogenic and mesogenic skeleton chemical structure represented by the following formula (1).

  The resin sheet may further contain a curing agent. As this curing agent, a known curing agent used for advancing the curing reaction of the epoxy resin can be used. Examples include phenolic compounds including phenolic resins and derivatives thereof, amine compounds and derivatives thereof, acid anhydrides and imidazoles and derivatives thereof, dicyandiamide and derivatives thereof, and the like. Two or more of these curing agents may be used in combination.

  In FIG. 1, the schematic diagram of the structure of the resin part of the resin sheet which concerns on this embodiment is shown. The resin sheet has a phase separation structure in which the second phase 2 is dispersed in the first phase 1 in the resin portion. Examples of the shape of the second phase 2 include an island shape, a band shape, and a needle shape. In particular, from the viewpoint of the dispersibility of the first phase 1, an island shape, that is, a shape close to a spherical shape is preferable.

  That is, in the resin sheet that is a semi-cured product, as shown in FIG. 1, the epoxy resin having a mesogenic skeleton in the homogeneous first phase 1 having the above curing agent as the main component is used as the main component in the resin portion. The second phase 2 has a dispersed phase separation structure. The second phase 2 may contain impurities such as inevitable components.

  In the case of a homogeneous structure without this phase separation structure, the orientation of the mesogenic epoxies is weak, and the formation of higher order structures due to the orientation during the curing process to form the subsequent laminated board or printed wiring board becomes insufficient. Conductivity decreases. The determination of the presence or absence of the phase separation structure can be performed by observing the resin part of the cross section of the resin sheet with a scanning electron microscope or a metal microscope.

  It is also essential that the epoxy content of the second phase 2 is greater than the epoxy content of the first phase 1. When the epoxy content of the first phase 2 is larger than the epoxy content of the second phase 2, the amount of the curing agent becomes extremely small. Therefore, when the laminate or printed wiring board is a cured product, the degree of uncuring Increases, so that the electrical insulation is reduced.

  Regarding the judgment of the size of the epoxy content here, the first phase 1 and the second phase 2 are subjected to microscopic Fourier infrared spectroscopy (FT-IR) observation at the resin part of the cross section of the resin sheet, and the first The peak intensity derived from the epoxy group of the infrared (IR) profile of phase 1 and the infrared (IR) profile of second phase 2 is compared, and either first phase 1 or second phase 2 has a higher epoxy resin content. You can judge whether or not.

  In the resin part of the resin sheet, the volume ratio of the second phase 2 to the total volume of the resin component, which is the sum of the first phase 1 and the second phase 2, is 10 vol. % Or more is more preferable in that a high thermal conductivity of 1.40 W / (m · K) or more can be obtained. The volume ratio is 10 vol. If it is less than%, the amount of epoxy resin having a mesogenic skeleton that contributes to the formation of a higher-order structure by orientation decreases, so that high thermal conductivity tends to be insufficient.

  The volume ratio is 83 vol. %, The epoxy resin having the mesogen skeleton is not completely melted in the melt molding process to the laminated board and printed wiring board, and uncured voids are generated. Since the electrical insulation property of the plate tends to decrease, the volume ratio is 83 vol. % Or less is preferable. The term “uncured void” as used herein refers to the presence of an uncured resin portion in a cured resin such as a laminate or a printed wiring board.

  Further, for the purpose of improving the curing reaction rate, a curing accelerator is added to the resin sheet from the precursor resin composition, and the curing accelerator is preferably a latent curing accelerator. .

  Hereinafter, the latent curing accelerator having high potential in the resin sheet of the present embodiment will be described in detail. In FIG. 2, the schematic diagram which has a cured film of the 2nd phase 2 surface of the resin part of the resin sheet which concerns on this embodiment is shown. In the resin portion, the second phase 2 is dispersed in the first phase 1, and the surface of the second phase has a phase separation structure covered with the cured coating 3.

  As a curing accelerator for a resin composition that is a precursor of a resin sheet containing an epoxy resin having a mesogenic skeleton and a known curing agent, a phosphorus compound system, an amine compound system, an imidazole compound system, etc. are generally used. ing. Among these, for laminates and printed wiring boards, imidazole compounds that are highly crosslinked cured products are most widely used because their cured products require a relatively high glass transition point. However, since this imidazole compound-based curing accelerator has high activity with respect to epoxy resins, the curing reaction rate of the resin composition is extremely fast, and impregnation is implicated in terms of the production of resin sheets containing prepreg. The inactivation degree of the curing accelerator is low up to the drying temperature region of the solvent in the resin composition applied, and the curing reaction tends to proceed.

  Accordingly, when the contained epoxy resin is an epoxy resin having a mesogen skeleton, like the resin composition that is a precursor of the resin sheet of the present embodiment, it does not dissolve in the solvent contained in the resin composition. Since the epoxy resin has a large number of fine particles, as described above, the second phase 2 and the other components mainly composed of an epoxy resin having a fine particle portion of the epoxy resin, that is, a mesogen skeleton at the time of drying or semi-curing at the time of resin sheet preparation Phase-separated into two homogeneous first phases 1 mainly composed of a hardener and the like. Then, as shown in FIG. 2, the curing reaction proceeds during the drying or semi-curing, and the cured film 3 is easily generated on the surface of the second phase 2.

  The cured film 3 will be described in detail. Compared with the epoxy resin dispersed in a small amount in the curing agent in the first phase 1, the second phase 2 epoxy resin is an agglomerate of epoxy fine particles. The functional group density is extremely high. Therefore, for example, in the case of a highly active imidazole compound-based curing accelerator, the epoxy functional group on the surface of the second phase 2 and its surroundings in the resin part in the process from drying to semi-curing of resin sheet production from the resin composition As the curing agent rapidly undergoes a curing reaction, a cured film 3 is formed on the surface of the second phase 2. Therefore, in the resin portion, the epoxy resin fine particles, that is, the second phase 2 are covered with the cured film 3, and the surrounding resin portion, that is, the first phase 1 is in a homogeneous semi-cured state. This resin part is melt-molded at 170 ° C. to 180 ° C. to become a laminated board or printed wiring board. However, since the second phase 2 having the cured film 3 on the surface does not completely melt, other curing agents and the like are included. Melt-compatible with the first phase 1 is not homogeneous, and aggregates of fine particles of mesogenic epoxy resin are generated. Then, the aggregates tend to be uncured voids in the laminated board and the printed wiring board, so that the electrical insulation tends to be hardly obtained.

  From the above, in order to maintain electrical insulation as a laminated board and a printed wiring board, it is preferable to use a latent curing accelerator in the resin sheet of this embodiment. By using the latent curing accelerator, the cured film on the surface of the second phase 2 can be minimized, and accordingly, the electrical insulation can be maintained or improved.

  With regard to improving the potential of imidazole-based curing accelerators, that is, making them into latent curing accelerators, an organic substituent for increasing the melting point is introduced into the compound so that it does not melt to the drying temperature range so that the curing accelerator is not used. There are a method of making it active and a method of making an imidazole compound a salt structure so that the salt is not dissociated up to the drying temperature region and making the curing accelerator inactive.

  More preferably, the curing accelerator is an inclusion compound that is included in another compound, and it is preferable that the curing accelerator has a higher potential compared to the above-described latent curing accelerator. FIG. 3 shows a schematic diagram of the inclusion compound. As shown in FIG. 3, the inclusion compound refers to a compound in which compound (A) 5 is incorporated into the crystal structure of compound (B) 4. More specifically, when the inclusion compound is an imidazole curing accelerator, an imidazole compound as shown in formula (2) is incorporated into a crystal structure represented by tetrakisphenols as shown in formula (3). In addition, if the crystallinity of the tetrakisphenols is high, there is almost no release of the imidazole compound up to the drying temperature range, so that a very high potential can be maintained. That is, the contact between the cured resin and the curing accelerator can be minimized. At this time, the inclusion compound is not formed by chemical bond between the imidazole compound and the tetrakisphenol, and the crystal structure is broken at a high temperature (for example, heat of drying during the process or heat of curing). The compound is released and a curing accelerating function is expressed in the resin composition. Therefore, the imidazole compound and the tetrakisphenol are independent, and do not affect the activity of the imidazole compound as a curing accelerator even when the crystallinity of the tetrakisphenol is high.

  Due to the high potential effect of the curing accelerator, which is an inclusion compound, in the resin sheet of the present embodiment, fine particles of epoxy resin having a mesogenic skeleton having a cured film on the resin portion (second phase 2) The generation of fine particles and the aggregation of the fine particles in the form as described above do not occur, so that the uncured voids specific to epoxy resins having a mesogenic skeleton do not occur in laminated boards and printed wiring boards provided with the resin sheets. Electrical insulation can be greatly improved. In addition, although the compound included is imidazole compound (A), it is not limited to this. In addition, it is essential that at least one curing accelerator contains an inclusion compound, but other latent curing accelerators may be used in combination.

  If necessary, the resin sheet according to the present embodiment includes a flame retardant, a colorant, a plasticizer, an antioxidant, a mold release agent, an anti-settling agent, a coupling agent, a dispersant, an adhesion promoter, an ion scavenger, and the like. An additive may be included. Moreover, the resin composition may contain an organic solvent for the purpose of producing a resin sheet.

  The resin sheet can be blended with a filler in order to improve mechanical properties such as thermal conductivity, strength and internal stress and to ensure flame retardancy. Examples of the particulate filler include metal oxides, hydroxides, carbides, nitrides, and the like. More specifically, aluminum oxide, magnesium hydroxide, aluminum hydroxide, silicon dioxide, boron nitride, silicon carbide, Silicon nitride, magnesium oxide, zinc oxide, aluminum nitride, beryllium oxide, titanium oxide, titanium carbide, titanium nitride, zirconium oxide, zirconium carbide, zirconium nitride, vanadium carbide, vanadium nitride, chromium nitride, molybdenum nitride, niobium carbide, tantalum carbide Examples of the filler include spherical, flake-like, plate-like, and columnar fillers, and these may be used in combination of two or more fillers. Examples of the fibrous filler include materials such as glass fibers, paper fibers, organic synthetic fibers such as aramid fibers, and ceramic fibers.

  The resin composition, which is a precursor of the resin sheet of the present embodiment, can be impregnated into a sheet-like woven fabric or nonwoven fabric made of glass fiber, organic fiber, or the like to produce a resin sheet called a prepreg. . Moreover, without using a sheet-like woven fabric or non-woven fabric, using a known comma coater, gravure coater, slot die coater or the like, it is applied to an organic film such as PET or a metal foil. A resin sheet can also be produced by drying. The resin sheet can be used as a semi-cured state by heating and drying.

  A laminated board is comprised by using the said resin sheet as all the layers or one part layer. A resin sheet can also be used in combination of 2 or more types. A typical schematic view of this laminate is shown in FIG. A copper foil 6 is attached to both surfaces of a laminate of a plurality of resin sheets 7 having a sheet-like glass cloth 10 and laminated and formed. Furthermore, the printed wiring board is provided with an insulating layer obtained by heat-pressing the resin sheet including the resin sheet 7 described above, a single-sided printed wiring board, a double-sided printed wiring board, a multilayer board having an inner layer circuit, an aluminum base board, Examples thereof include a metal core substrate in which thick copper is embedded in the substrate. FIG. 5 shows a typical schematic diagram of a multilayer substrate (four-layer substrate or printed wiring board) having this inner layer circuit. The multilayer substrate is formed by lamination molding in which an outer layer circuit 8 and an inner layer circuit 9 formed by etching are interlayer-insulated by a resin sheet 7 having a sheet-like glass cloth 10.

  As described above, the laminated board or the printed wiring board provided with the resin sheet 7 of the present embodiment enables high thermal conductivity of the laminated board and the printed wiring board due to the high thermal conductivity that is a characteristic of the epoxy resin itself. Since it is excellent in electrical insulation such as the dielectric breakdown voltage, the performance and reliability of a module product in which a highly heat-generating electronic component is mounted on a substrate can be greatly improved.

  Examples of the present invention will be described below, and the present invention will be described in detail. In the following examples and comparative examples, (part) means (part by weight). Moreover, this invention is not limited to a present Example, unless it deviates from the summary.

Example 1
An epoxy resin having a mesogenic skeleton is a mixture of 4,4′-tetramethylbiphenol epoxy resin and 4,4′-biphenol type epoxy resin (mixing ratio is 50 wt% to 50 wt%) manufactured by Mitsubishi Chemical Corporation. (Epoxy equivalent 175) was used. 10 parts of TD2093Y, which is a phenol novolac resin made by DIC Corporation, is added as a curing agent to 100 parts of this epoxy resin, and the volume ratio of the second phase to the volume of the entire resin amount in the resin sheet is 91 vol. % Adjusted. Furthermore, 1 part of 1-cyanoethyl-2-undecylimidazolium trimellitate (C11-ZCNS manufactured by Shikoku Kasei Co., Ltd.), which is a latent curing accelerator as a curing accelerator, is manufactured by Denki Kagaku Kogyo Co., Ltd. as a filler. An epoxy resin composition is obtained by adding 500 parts of DAW-03, which is spherical alumina particles, and 100 parts of methyl ethyl ketone as a solvent for coating, mixing with a lyker machine, and further dispersing the mixture using a disper. An impregnation paint was prepared. The compound of the curing accelerator here has a salt structure of trimellitic acid, and is a latent curing accelerator that exhibits a curing acceleration effect when the salt dissociates and dissolves in the resin at high temperatures.

This paint was impregnated into a glass cloth as a fiber substrate having a thickness of 35 μm and dried by heating to obtain a resin sheet having a thickness of 110 μm.
A laminated board for characteristic evaluation is obtained by stacking a plurality of resin sheets cut to an appropriate size and performing a lamination press with a vacuum press at a temperature increase of 2.0 ° C./min and a post-cure 175 ° C. for 1 hour to obtain an epoxy resin. A laminate comprising a resin sheet containing the composition was prepared and carried out.
Further, cross-sectional observation of the resin sheet is performed using a scanning electron microscope, and the phase separation structure of the first phase and the second phase, more specifically, the second phase is dispersed in the first phase. Was observed and checked to determine whether the phase separation or homogeneous.

The thermal conductivity was measured by punching out a laminated plate obtained by laminating and pressing six resin sheets at 175 ° C. into a disk shape having a diameter of 10 mm to prepare a sample for measuring thermal diffusivity. The thermal diffusivity of the prepared sample was measured with a TC series (manufactured by ULVAC-RIKO). Specific heat was measured by DSC using sapphire as a standard sample. The measured values were substituted into the following formula (4) to obtain the thermal conductivity in the thickness direction of the laminate, and 1.00 W / (m · K) or more was evaluated as sufficient thermal conductivity was obtained.
λ = α × Cp × r (4)
α: Thermal diffusivity Cp: Specific heat
r: Density

The dielectric breakdown voltage test of the laminate was evaluated by measuring the dielectric breakdown voltage with a test piece of laminate 100 mm × 100 mm laminated and molded at 175 ° C. by laminating two resin sheets.
Moreover, after cutting these test pieces, cross-sectional polishing was performed, the polished surface was observed with a metal microscope, and the appearance of uncured voids resulting from the cured film of the epoxy resin was confirmed. As evaluation criteria, those with no phase separation are determined as laminate appearance: ○ (no uncured voids), and those with any phase separation present as laminate appearance: x (with uncured voids) did.

  Table 1 shows the respective material compositions and characteristics of the laminate including the resin composition of Example 1. As characteristics of the laminate, the thermal conductivity was 1.52 W / (m · K), and the dielectric breakdown voltage was 28 kV / mm. Further, no uncured voids were observed, and the laminate appearance was good.

Example 2
The amount of the added curing agent was 20 parts, and the volume ratio of the second phase to the total volume of the resin in the resin sheet was 83 vol. The same procedure as in Example 1 was performed except that the content was%. The results are shown in Table 1. The island-like dispersion (phase separation structure) was also confirmed in the resin part of the resin sheet. As characteristics of the laminated plate, the thermal conductivity was 1.56 W / (m · K), the dielectric breakdown voltage was 50 kV / mm, and the dielectric breakdown voltage was greatly improved as compared with Example 1. Further, no uncured voids were observed, and the laminate appearance was good.

Example 3
The amount of the added curing agent was 59.4 parts, and the volume ratio of the second phase to the total volume of the resin in the resin sheet was 63 vol. The same procedure as in Example 1 was performed except that the content was%. The results are shown in Table 1. The island-like dispersion (phase separation structure) was also confirmed in the resin part of the resin sheet. As characteristics of the laminate, the thermal conductivity was 1.52 W / (m · K), and the dielectric breakdown voltage was 45 kV / mm. Further, no uncured voids were observed, and the laminate appearance was good.

Example 4
The amount of the added curing agent was 100 parts, and the volume ratio of the second phase to the total volume of the resin in the resin sheet was 50 vol. The same procedure as in Example 1 was performed except that the content was%. The results are shown in Table 1. The island-like dispersion (phase separation structure) was also confirmed in the resin part of the resin sheet. As the characteristics of the laminate, the thermal conductivity was 1.51 W / (m · K), and the dielectric breakdown voltage was 48 kV / mm. Further, no uncured voids were observed, and the laminate appearance was good.

Example 5
The amount of the added curing agent was 130 parts, and the volume ratio of the second phase to the total volume of the resin in the resin sheet was 43 vol. The same procedure as in Example 1 was performed except that the content was%. The results are shown in Table 1. The island-like dispersion (phase separation structure) was also confirmed in the resin part of the resin sheet. As characteristics of the laminate, the thermal conductivity was 1.58 W / (m · K), and the dielectric breakdown voltage was 55 kV / mm. Further, no uncured voids were observed, and the laminate appearance was good.

Example 6
The amount of the added curing agent was 370 parts, and the volume ratio of the second phase to the total volume of the resin in the resin sheet was 21 vol. The same procedure as in Example 1 was performed except that the content was%. The results are shown in Table 1. The island-like dispersion (phase separation structure) was also confirmed in the resin part of the resin sheet. As characteristics of the laminate, the thermal conductivity was 1.53 W / (m · K), and the dielectric breakdown voltage was 50 kV / mm. Further, no uncured voids were observed, and the laminate appearance was good.

Example 7
The amount of the added curing agent was 920 parts, and the volume ratio of the second phase to the total volume of the resin in the resin sheet was 10 vol. The same procedure as in Example 1 was performed except that the content was%. The results are shown in Table 1. The island-like dispersion (phase separation structure) was also confirmed in the resin part of the resin sheet. As characteristics of the laminate, the thermal conductivity was 1.44 W / (m · K), and the dielectric breakdown voltage was 51 kV / mm. Further, no uncured voids were observed, and the laminate appearance was good.

Example 8
The amount of the added curing agent was 1180 parts, and the volume ratio of the second phase to the total volume of the resin in the resin sheet was 8 vol. The same procedure as in Example 1 was performed except that the content was%. The results are shown in Table 1. The island-like dispersion (phase separation structure) was also confirmed in the resin part of the resin sheet. As characteristics of the laminate, the thermal conductivity was 1.12 W / (m · K), and the dielectric breakdown voltage was 30 kV / mm. Further, no uncured voids were observed, and the laminate appearance was good.

Example 9
Except that the added curing accelerator was 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine (2MZ-A manufactured by Shikoku Kasei Co., Ltd.) Performed as in Example 3. The compound used in this curing accelerator has a triazine group introduced into the imidazole skeleton, and is a latent curing accelerator that exhibits a curing accelerating effect when the temperature rises and the compound melts. The results are shown in Table 1. The island-like dispersion (phase separation structure) was also confirmed in the resin part of the resin sheet. As the characteristics of the laminate, the thermal conductivity was 1.55 W / (m · K), and the dielectric breakdown voltage was 50 kV / mm. Further, no uncured voids were observed, and the laminate appearance was good.

Example 10
The same procedure as in Example 3 was performed except that the added curing accelerator was an amine adduct (PN-23 manufactured by Shikoku Kasei Co., Ltd.). The results are shown in Table 1. The island-like dispersion (phase separation structure) was also confirmed in the resin part of the resin sheet. As characteristics of the laminate, the thermal conductivity was 1.48 W / (m · K), and the dielectric breakdown voltage was 49 kV / mm. Further, no uncured voids were observed, and the laminate appearance was good.

Example 11
This was carried out in the same manner as in Example 3 except that a compound in which 2-phenyl-4-methylimidazole, which is a curing accelerator having high potential, was added with tetrakisphenol was used. The results are shown in Table 1. The island-like dispersion (phase separation structure) was also confirmed in the resin part of the resin sheet. As the characteristics of the laminated plate, the thermal conductivity was 1.49 W / (m · K), the dielectric breakdown voltage was 65 kV / mm, and the dielectric breakdown voltage was improved as compared with Examples 1-10. Further, no uncured voids were observed, and the laminate appearance was good.

Comparative Example 1
The same procedure as in Example 3 was performed except that an ortho-cresol novolac type epoxy resin was used instead of the epoxy resin having a mesogenic skeleton. The results are shown in Table 1. The island-shaped dispersion (phase separation structure) was not confirmed in the resin part of the resin sheet. The laminate has the following characteristics: thermal conductivity is 0.78 W / (m · K), dielectric breakdown voltage is 54 kV / mm, and an epoxy resin having a mesogenic skeleton that forms a higher order structure at the time of molding is not used. The thermal conductivity decreased. Further, no uncured voids were observed, and the laminate appearance was good.

Comparative Example 2
It shows in Table 2 similarly to the comparative example 1. This was carried out in the same manner as in Example 3 except that a tetramethylbiphenol type epoxy resin was used so that the epoxy resin having a mesogenic skeleton had low orientation and was compatible with a curing agent to form a homogeneous resin sheet. The results are shown in Table 1. The laminate has the following characteristics: thermal conductivity is 0.82 W / (m · K), dielectric breakdown voltage is 57 kV / mm, and this epoxy resin does not form a high-order structure at the time of molding. However, compared with Example 1, it decreased. Further, no uncured voids were observed, and the laminate appearance was good.

Laminated plate appearance ○: No uncured void Laminated plate appearance ×: Uncured void present N-670: DIC Corporation ortho-cresol novolac epoxy resin YL6121H: Mitsubishi Chemical Corporation 4,4′-tetramethylbiphenol epoxy resin Mixture of 4,4'-biphenol type epoxy resin (mixing ratio is 50wt% vs 50wt%)
YX4000H: 4,4′-tetramethylbiphenol type epoxy resin manufactured by Mitsubishi Chemical Corporation TD2093Y: phenol novolac resin manufactured by DIC Corporation C11-ZCNS: 1-cyanoethyl-2-undecylimidazolium trimellitate 2MZ manufactured by Shikoku Kasei Co., Ltd. -A: 2,4-diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine manufactured by Shikoku Kasei Co., Ltd. PN-23: amine adduct TEP-2P4 MHz manufactured by Ajinomoto Finetech Co., Ltd .: Nippon Soda Co., Ltd. 2-phenyl-4-methylimidazole compound included in tetrakisphenol DAW-03: Denki Kagaku Kogyo Co., Ltd.

  As described above, as is apparent from Table 1, it is a semi-cured resin sheet containing an epoxy resin having a mesogenic skeleton, which is being developed as a high thermal conductive material, and is a second phase mainly composed of an epoxy resin having a mesogenic skeleton. In the first phase mainly composed of a curing agent, a phase separation structure in which the second phase is dispersed in an island shape in the first phase, a higher order structure is formed at the time of forming the laminate, The conductivity could be increased. Furthermore, by using the curing accelerator contained in the resin sheet as a latent curing accelerator, the generation of a cured film on the surface of the second phase mainly comprising an epoxy resin having a mesogenic skeleton in the resin sheet is greatly reduced. As a result, the laminated board and the printed wiring board provided with the resin sheet can greatly reduce the uncured voids and improve the dielectric breakdown voltage.

  The above-mentioned resin sheet was obtained by laminating copper foil as a conductor so as to sandwich the resin sheet, and laminating with a vacuum press, thereby producing a high thermal conductivity copper-clad laminate as a printed wiring board material. Furthermore, on this copper clad laminate, formation of a circuit pattern by photo and etching, formation of a through hole by drilling and plating of the through hole, lamination of the resin sheet, printed wiring board such as resist coating, etc. By subjecting to a known processing, a highly heat-conductive printed wiring board having a high heat radiation function could be produced.

1 First Phase 2 Second Phase 3 Cured Film 4 Compound (B)
5 Compound (A)
6 Copper foil 7 Resin sheet 8 Outer layer circuit pattern 9 Inner layer circuit pattern 10 Glass cloth

Claims (4)

4,4′-tetramethylbiphenol epoxy resin having a first phase and a second phase, the second phase being dispersed in the first phase, and the first phase and the second phase having mesogenic groups; , 4′-biphenol type epoxy resin mixture, a phenol novolac resin as a curing agent, and the second phase epoxy resin content is higher than that of the first phase,
A resin sheet containing a latent curing accelerator in the resin sheet.   The resin sheet according to claim 1, wherein the latent curing accelerator is an inclusion catalyst.   A laminate comprising at least one layer of the resin sheet according to claim 1 or 2. A printed wiring board comprising at least one layer of the resin sheet according to claim 1.