JP2010163598A - Prepreg, method for producing the same, and printed wiring board using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prepreg from which a printed wiring board having both drilling machinability and thermal conductivity can be manufactured. <P>SOLUTION: The prepreg is produced by impregnating a substrate consisting of a glass woven or nonwoven fabric with a resin composition containing an inorganic filler. In the prepreg, the inorganic filler content is adjusted to 30 to 70 vol.% relative to the prepreg. Further, the inorganic filler contains a component which has both thermal conductivity of 9 W/mK or above and a Mohs' hardness of 6 or below in an amount of 60 vol.% or larger relative to the inorganic filler. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a printed wiring board / metal substrate on which a heat generating electronic component is mounted, a prepreg used as an insulating layer thereof, and a manufacturing method thereof.

  In recent years, heat generation of electronic components (high-functional semiconductors, power semiconductors, transformers, etc.) accompanying miniaturization and high performance of equipment has become an issue, and heat countermeasures such as heat sinks, fans, heat pipes have been taken Yes. A printed wiring board for mounting such heat-generating electronic components is equipped with a high-performance semiconductor and has a multilayer board configuration to support high-density mounting. It consists of a prepreg made of glass epoxy resin and copper foil. There are a metal substrate composed of an adhesive layer that adheres a metal heat sink and a copper foil, and a case where a plurality of members are laminated and cured.

  In the metal substrate, in order to transmit the heat of the electronic component to the heat radiating plate, efforts are made to improve the thermal conductivity, and the filling amount of the inorganic filler having a high thermal conductivity is increased. Therefore, many attempts have been made to add inorganic fillers at high density to resin compositions used as adhesive layers (see Patent Literature). However, since such a resin composition does not perform drilling in a metal substrate that does not have a multilayer board configuration, drilling workability is not considered, and a hard inorganic filler such as alumina (because of high thermal conductivity) ) Is used. Further, the filling rate is high due to the improvement of the thermal conductivity, and the drill blade is significantly worn during drilling.

 In the multilayer board, there is no heat sink, and the thermal conductivity of the prepreg is low, so it is not considered as a heat countermeasure at present, and in order to obtain the strength of the substrate, the coefficient of thermal expansion, flame retardancy, The present condition is that it contains a small amount (about 20 vol%) of aluminum hydroxide. As drilling processability, as a multilayer printed wiring board, drilling is an almost indispensable process, so as to improve drilling accuracy, a proposal for filling an inorganic filler with low Mohs hardness as in Patent Document 1 has been made. Yes.

JP 2000-117733 A

  Up to now, printed wiring boards have not been considered much as a heat countermeasure, but since the mounted electronic components are in direct contact and can effectively transmit heat, the board itself is a new material that cures the heat sink. It was found that it could be used as a heat countermeasure. In the case of a conventional printed wiring board with a multilayer board configuration, it is essential to achieve not only thermal conductivity but also drillability. However, drilling of the drill blade is severe in current materials for metal substrates with high thermal conductivity. There was a problem. In addition, the deterioration of the drill workability also deteriorates the drill hole shape and hole diameter of the through hole, so that the reliability of the plating connection also decreases.

  Accordingly, an object of the present invention is to provide a printed wiring board and a prepreg thereof in consideration of not only thermal conductivity but also wear resistance of a drill blade.

  In order to achieve this object, the present invention provides a prepreg obtained by impregnating a glass woven fabric or glass nonwoven fabric with a resin composition containing an inorganic filler, and the filling ratio of the inorganic filler to the prepreg is 30 vol% or more and 70 vol%. %, And the inorganic filler is a prepreg characterized by containing a component having a thermal conductivity of 9 W / mK or more and a Mohs hardness of 6 or less of 60 vol% or more.

  According to the prepreg of the present invention, its manufacturing method and a printed wiring board using the prepreg, it contains 60 vol% or more of inorganic filler having a thermal conductivity as high as 9 W / mK or more, and the filling rate of the inorganic filler with respect to the prepreg By adjusting the content to 30 vol% or more and 70 vol% or less, the thermal conductivity of the prepreg and the printed wiring board after molding can be improved. Moreover, by setting the Mohs hardness of the inorganic filler to 6 or less, high drill workability can be realized even at a high filling rate of the inorganic filler. In addition, the high thermal conductivity of the inorganic filler effectively dissipates heat during drilling, which can reduce the melting of the resin as the temperature rises. The decline in sex can be suppressed.

  Further, by using an inorganic filler having a substantially polyhedral shape, particularly a substantially cubic or substantially rectangular parallelepiped shape, heat percolation is improved, and thermal conductivity can be improved even with a relatively small filling amount capable of suppressing deterioration of drill workability. .

  By using the printed wiring board manufactured using the prepreg of the present invention, the heat of the electronic component is diffused to the substrate and the heat dissipation is improved, so that the temperature of the electronic component can be reduced and the electronic component can be mounted at high density. Higher functions, higher power, smaller equipment and higher functions can be achieved.

The figure which shows the relationship between Hit number and drill residual ratio in the case of aluminum oxide combination The figure which shows the relation between the Hit number and drill residual ratio in the case of magnesium oxide combination The figure which shows the relationship between Hit number and drill residual ratio in the case of magnesium carbonate combination

Example 1
Hereinafter, a prepreg will be described as Example 1 of the present invention.

  The resin used in the prepreg of the present invention is not particularly limited, but epoxy resin, polyimide resin, triazine resin, phenol resin, melamine resin, and modified resins of these resins can be used. . Moreover, you may use various hardening | curing agents and hardening accelerators as needed other than mixing the said various resin 2 or more types. For example, when an epoxy resin is used, characteristics such as heat resistance, strength, and adhesiveness are suitable for the substrate. When polyimide resin is used, heat resistance and flexibility can be added to the printed wiring board. When a curing agent is used for the resin, for example, when used for an epoxy resin, polyfunctionality such as dicyandiamide, diaminodiphenylmethane, diaminodiphenylsulfone, phthalic anhydride, pyromellitic anhydride, and phenol novolac and cresol novolac Sexual phenol and the like can be used. The curing agent can be used alone or in combination of two or more kinds, and the kind and amount thereof are not limited and can be appropriately determined. In the case of using an accelerator for the resin, it can be used in a variety of manners similar to the curing agent described above. Specifically, imidazole compounds, organic phosphorus compounds, amines, ammonium salts, and the like are used. Two or more kinds may be used in combination. Also, rubber or thermoplastic resin may be added.

  The glass woven fabric / nonwoven fabric as a structure in the prepreg has the effect of increasing the strength of the prepreg, and the effects of controlling the thermal expansion coefficient after curing, dimensional stability, and mechanical strength are obtained. The glass woven / nonwoven fabric is preferably about 10 to 300 μm. When the thickness of the glass woven fabric / nonwoven fabric is less than 10 μm, it may affect the mechanical strength (for example, tensile strength) of the prepreg or a printed wiring board obtained by curing the prepreg. When the thickness of the glass woven fabric / nonwoven fabric exceeds 300 μm, the influence on the drying process during production of the prepreg becomes large.

  The inorganic filler filled in the resin has an inorganic filler having a thermal conductivity of 9 W / mK or more and a Mohs hardness of 6 or less of 60 vol% or more. For example, boron nitride, magnesium oxide, zirconium silicate, magnesium hydroxide, zirconium silicate, Magnesium carbonate, aluminum hydroxide, or the like can be used. By setting the thermal conductivity to 9 W / mK or more, the thermal conductivity of the printed wiring board after molding and curing the prepreg can be set to 0.8 W / mK or more, and the heat of the electronic components that generate heat is effectively reduced. It is possible to disperse and reduce the temperature of the electronic component. Further, heat generated during drilling can also be dispersed, and a decrease in drill workability such as embedding of a drill blade groove accompanying an increase in resin temperature can be suppressed. Moreover, when the inorganic filler with a thermal conductivity of 9 W / mK or more is 30 vol% or less, the thermal conductivity of the printed wiring board is lowered.

  As for the hardness of the drill blade used for drilling, Mohs hardness of chrome plating is 9, and there is a diamond-coated drill blade with Mohs hardness of 10, but considering the cost and workability, the Mohs hardness of inorganic filler is at least drill It must be below the blade, and preferably below 6. Drilling workability can be further improved when the Mohs hardness is 4 or less.

  The inorganic filler needs to have a filling rate of 30 vol% or more and 70 vol% or less with respect to the prepreg. The vol% is defined here in order to make the effect on thermal conductivity and drilling work constant even when changing to inorganic fillers with different densities. When multiple materials are defined, they are described in wt%. To do is essentially not true. Moreover, the desired value can be obtained for the thermal conductivity when formed on the substrate by defining the filling rate of the inorganic filler having a high thermal conductivity with respect to the entire prepreg including the glass woven fabric / nonwoven fabric. The thermal conductivity of a prepreg can be 0.8 W / mK or more by making the filling rate with respect to the prepreg of an inorganic filler 30 vol% or more. In order to increase the value of the inorganic filler / prepreg, it is effective to increase the ratio of the inorganic filler / resin composition in the resin composition impregnated into the glass cloth and to increase the resin fraction / prepreg in the prepreg (glass Woven / nonwoven fabrics have low thermal conductivity). By setting the filling rate of the resin composition / prepreg to 50 vol% or more, the filling rate of the inorganic filler / prepreg can be set to 30 vol% or more. Similarly, by setting the filling rate of the inorganic filler / resin composition to 40 vol% or more, the filling rate of the inorganic filler / prepreg can be set to 30 vol% or more.

  Moreover, when the filling rate with respect to the prepreg of an inorganic filler will be 70 vol% or more, board | substrate shaping | molding may become difficult, such as a raise of the melt viscosity of a prepreg, and the adhesive force fall of copper foil and a prepreg.

  When the filling ratio of the resin composition / prepreg is 95 vol% or more, there may be a problem such as insufficient strength due to a decrease in the ratio of the glass woven fabric / nonwoven fabric that is a structure.

  Further, when the filling ratio of the inorganic filler / resin composition is 90 vol% or more, the viscosity of the mixture (varnish) of the resin, the inorganic filler, and the solvent increases, and the impregnation process at the time of preparing the prepreg becomes difficult. In addition, the melt viscosity of the prepreg also increases due to the lack of resin, and the flowability at the time of forming the multilayer substrate may be significantly reduced, making it impossible to provide a highly reliable printed wiring board.

  Deterioration of drillability affects the hole shape and diameter of the through hole, and the reliability of the plated connection of the through hole decreases. However, by increasing the filling rate of the inorganic filler / prepreg, A thermal expansion coefficient (especially thickness direction) can be made small. Thereby, the reliability of the through hole is improved by reducing the thermal expansion coefficient in the Z-axis direction. Since the through hole is formed by plating after drilling, the plated part has a thermal expansion coefficient of a metal material (generally copper), and by reducing the thermal expansion coefficient in the Z-axis direction, The expansion difference is reduced, and the generated stress is reduced. When the coefficient of thermal expansion is 45 ppm / ° C. or less, the reliability is high and the durability against thermal shock and thermal cycle is improved, which is desirable. Furthermore, reliability is further improved by setting it as 35 ppm / degrees C or less.

  The inorganic filler preferably has a substantially polyhedral shape, more preferably a substantially cubic shape and / or a substantially rectangular parallelepiped shape. In order to improve the thermal conductivity, it is necessary to increase the filling rate of the inorganic filler. For this reason, an inorganic filler close to a spherical shape is often used, but an increase in the inorganic filler leads to a decrease in drill workability. Considering the same filling rate, the contact between the planes of the inorganic filler is desirable in terms of heat percolation, and the thermal conductivity can be improved by using the inorganic filler having a substantially polyhedral shape. The substantially polyhedral shape here means a solid body having a flat surface portion, and does not mean that there is no curved surface portion at all. Especially, a substantially cubic shape or a substantially rectangular parallelepiped shape can increase a contact area. However, a plate-like or needle-like inorganic filler having an aspect ratio of 3 or more has poor kneadability and increases the melt viscosity. A shape with an aspect ratio of 2.5 or less is desirable in terms of improving thermal conductivity while preventing deterioration of melt viscosity.

  The filler has fewer impurities and a higher crystallinity, the higher the thermal conductivity. Also, the crystallinity is improved, the surface becomes smooth, and the BET value and the amount of oil supply decrease. Also, the shape tends to be a shape corresponding to the crystal system. Therefore, the kneadability can be improved and the melt viscosity can be reduced. Also, the smoothness of the surface leads to an improvement in percolation. A filler having a cubic or tetragonal crystal structure is desirable as an inorganic filler because it tends to grow into a substantially cubic or substantially rectangular parallelepiped shape. The degree of crystallinity can be easily measured by, for example, the half width of the peak in X-ray diffraction. In the case of a cubic filler in the powder X-ray diffraction method using Cu—Kα rays, the half width of the peak on the (200) plane is preferably 0.3 ° or less. Moreover, it is better that the half-value widths of the peaks on the (111) plane and the (220) plane are also small, preferably 0.3 degrees or less.

  These inorganic fillers may be subjected to a surface treatment. The surface treatment can improve moisture resistance, adhesive strength, and dispersibility. As the surface treatment, in addition to a silane coupling agent, a titanate coupling agent, a phosphoric acid ester, a sulfonic acid ester, and a carboxylic acid ester, it may be coated with an alumina, silica coat, or silicone material. In order to increase the filling rate of the inorganic filler, a plurality of types of inorganic fillers having different particle size distributions may be selected and used in combination.

(Example 2)
Hereinafter, an example of a method for producing a prepreg will be described as Example 2 of the present invention.

  Stir and knead varnish consisting of resin, inorganic filler, and solvent in a specified amount, impregnate glass woven / nonwoven fabric with varnish, heat dry, remove solvent, and make resin semi-cured Thus, a prepreg is produced.

  Next, a method for producing a printed wiring board having high thermal conductivity and good drillability using a prepreg will be described. One or more prepregs are stacked to form a laminate, and a copper clad laminate can be obtained by stacking a copper foil on the laminate and heating and pressing. Next, the copper foil of the copper clad laminate is patterned into a predetermined shape. The patterning can be performed by a general process (photoresist formation, exposure, development, etching, photoresist removal). Then, a multilayer board can be constituted by repeating the lamination process and the patterning process as necessary. Next, a hole is formed at a predetermined position of the laminated body by drilling or laser, etc., and copper plating is performed to form a through hole, and then the outermost layer is patterned. Next, a solder resist or the like is formed to complete the printed wiring board.

  The manufacturing method is not limited to the method described above. The prepreg can be used not only as a constituent material of a printed wiring board but also as an adhesive material between a copper foil of a metal substrate and a heat sink.

  As described above, by using the prepreg according to the present invention, a manufacturing method thereof, and a printed wiring board using the prepreg, downsizing of a mobile phone, a television, an electrical component, or a device that requires heat dissipation such as industrial use is required. High performance is possible.

(Experiment 1)
As Experiment 1, an example of the inventors' experiments and evaluation results will be described.

  Drilling workability was examined using aluminum oxide (Morse hardness 9 manufactured by Sumitomo Chemical Co., Ltd.), magnesium oxide (Morse hardness 6 manufactured by Kamijima Chemical Co., Ltd.), and magnesium carbonate (Morse hardness 3 manufactured by Kamishima Chemical Co., Ltd.) as the inorganic filler. The particle size of the inorganic filler is in the range of 1 to 5 μm.

An inorganic filler was blended with an epoxy resin (bisphenol F type + curing agent), and MEK was used as a solvent to diffuse with a disper mill to prepare a varnish. This varnish was impregnated into a glass woven fabric (# 1080: weight 48 g / m ² ) to prepare a prepreg. The ratio of the inorganic filler / resin composition (from 20 vol% to 90 vol%) and the thickness of the prepreg were adjusted so that the filling ratio of the inorganic filler to the prepreg was 10, 30, 50, 70 vol%.

  Six prepregs were laminated, 18 μm thick copper foil was laminated on the upper and lower outermost layers, and cured by heating (180 ° C. × 1 h) / pressurizing (2 MPa) with a hot press to prepare a sample substrate. . R-1566 having the same thickness was used as a reference.

  This sample substrate was drilled and the change in the drill blade diameter after 1000, 2000, 3000 HIT was measured. A drill having an initial diameter of 0.5 mm was used. At the time of drilling, the sample board was sandwiched between an entry board (aluminum: 0.12 mmt) and a backup board (baked board: 1.5 mmt).

  The remaining blade rate of the drill is shown in FIGS. When the aluminum oxide shown in FIG. 1 is used, the drill wear amount is large at 8.1% with a filling rate of 10% by volume of inorganic filler / prepreg, and exceeds 11.8% and 10% at 30% by volume. There was a problem with sex. This is the wear of the drill due to the high Mohs hardness. When the magnesium oxide shown in FIG. 2 was used, the wear amount of the drill was 8.2% at a filling rate of 70 vol%, and the magnesium carbonate shown in FIG. 3 was 4.0% at a filling rate of 30%. The wear rate of the reference R-1566 was 1.0%.

(Experiment 2)
As Experiment 2, a plurality of magnesium oxides (manufactured by Kamishima Chemical Co., Ltd., manufactured by Tateho Chemical Co., Ltd.) were used as inorganic fillers, and the relationship between crystallinity (filler shape) and thermal conductivity was examined. The particle size of the inorganic filler is in the range of 1 to 5 μm.

  Preparation of the sample prepreg was the same as in Example 1, and the filling ratio of the inorganic filler to the prepreg was set to 30 vol%. The ratio of the inorganic filler / resin composition (20 vol% or more and 90 vol% or less) and the thickness of the prepreg were adjusted.

  Four prepregs are laminated, and a copper foil with a thickness of 18 μm is laminated on the upper and lower outermost layers. After heating (180 ° C. × 1 h) and pressurizing (2 MPa) with a hot press machine, all the copper foil is removed by etching. The sample was processed into a disk shape of about φ12.7 mm to produce a thermal conductivity evaluation sample. In addition, powder X-ray diffraction was performed to measure crystallinity, and (111), (200), and (220) plane peaks were detected by analysis software (Jade), and the half-value width of each peak was Calculation was performed.

  The relationship between the value of the half width of the (200) plane and the thermal conductivity is shown in [Table 1].

From [Table 1], the sample with a smaller half-value width has a higher thermal conductivity and is 0.3 or less, and a thermal conductivity of 0.8 W / mK can be achieved. Also, the variation is small. This is probably because the crystal itself has a high thermal conductivity and the thermal percolation is improved.

  The manufacturing method is not limited to the method described above. The prepreg can be used not only as a constituent material of a printed wiring board but also as an adhesive material between a copper foil of a metal substrate and a heat sink.

  As described above, by using the prepreg according to the present invention, a manufacturing method thereof, and a printed wiring board using the prepreg, downsizing of a mobile phone, a television, an electrical component, or a device that requires heat dissipation such as industrial use is required. And higher performance and higher reliability.

Claims (12)

In a prepreg in which a glass woven fabric or glass nonwoven fabric base material is impregnated with a resin composition containing an inorganic filler, the filling ratio of the inorganic filler to the prepreg is set to 30 vol% or more and 70 vol% or less, and the inorganic filler has a thermal conductivity. A prepreg containing a component of 9 W / mK or more and a Mohs hardness of 6 or less in the inorganic filler of 60 vol% or more. In a prepreg obtained by impregnating a glass woven fabric or glass nonwoven fabric base material with a resin composition containing a substantially polyhedral inorganic filler, the filling rate of the inorganic filler with respect to the prepreg is set to 30 vol% or more and 70 vol% or less. A prepreg containing a component having a thermal conductivity of 9 W / mK or more and a Mohs hardness of 6 or less in the inorganic filler of 60 vol% or more. The prepreg according to claim 1 or 2, wherein the heat conductivity after curing is 0.8 W / mK or more and 20.0 W / mK or less. The prepreg according to claim 1 or 2, wherein the inorganic filler contains at least one kind of boron nitride, magnesium oxide, zirconium silicate, magnesium hydroxide, zirconium silicate, magnesium carbonate, and aluminum hydroxide. The prepreg according to claim 2, wherein the inorganic filler has a substantially cubic shape and / or a substantially rectangular parallelepiped shape. The prepreg according to claim 2, wherein the inorganic filler is cubic or tetragonal. The prepreg according to claim 1 or 2, wherein the half width of the peak on the (200) plane in powder X-ray diffraction using Cu-Kα rays of the inorganic filler is 0.3 ° or less. The prepreg according to claim 1 or 2, wherein a filling ratio of the resin composition to the prepreg is 50 vol% or more and 95 vol% or less. The prepreg according to claim 1 or 2, wherein a filling rate of the inorganic filler with respect to the resin composition is 40 vol% or more and 90 vol% or less. The prepreg according to claim 1 or 2, wherein a linear expansion coefficient in a thickness direction of the insulating plate obtained by curing the prepreg is 45 ppm / ° C or less in a range of the glass transition temperature Tg or less of the insulating plate. A metal foil-clad laminate, wherein one or more prepregs according to claim 1 and / or 2 are laminated to form a laminate, and metal foil is laminated on one side or both sides of the laminate and heat-pressed. Board.  A printed wiring board, wherein the prepreg according to claim 1 and / or 2 is used as an insulating layer of a constituent material.

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