JP2002138153A - Prepreg and method of preparing laminate using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a prepreg having excellent processability affording high precision board thickness of a laminate or a multi-layer circuit board after processing. SOLUTION: This method of producing a prepreg comprises the steps of impregnating a curing catalyst dissolved in a solvent into a glass fiber substrate, preferably in a ratio of 0.01 to 10 pts.wt. of the curing catalyst to 100 pts.wt. of the glass fiber substrate, then impregnating a thermosetting resin and drying by heating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prepreg excellent in thickness accuracy and formability and a method for manufacturing a laminated board using the prepreg, and has a formability equal to or higher than that of a conventional prepreg. It is possible to obtain a laminated board or a multilayer circuit board having excellent thickness accuracy, which has been difficult to achieve with the prepreg.

[0002]

2. Description of the Related Art In recent years, higher frequencies have been used in circuit board laminates and multilayer circuit boards than ever before, and the requirements for the physical properties of the materials have become even more severe. In particular, a variety of circuit board materials have been studied for the signal delay of the circuit, and a resin that can control the impedance by lowering the dielectric constant of the circuit board and improving the precision of the board thickness after forming the board has been developed. I have. The thickness accuracy of the substrate has a one-time correlation with the signal delay. On the other hand, regarding the reduction of the dielectric constant of the substrate material, the dielectric constant correlates with the square root of the signal delay. Is the more effective means.

[0003] In order to improve the thickness accuracy of a substrate, it is important to control the amount of resin flowing out of a mold (hereinafter referred to as flowout) generated during molding. For example, flowout has been controlled by increasing the minimum melt viscosity of the resin during molding. Specifically, there is a method of increasing the viscosity of the resin by adding a filler or a high molecular weight resin to the resin to be impregnated into the prepreg, but the method of increasing the viscosity of the resin decreases the impregnation property to the glass fiber base material. Therefore, the voids in the fiber may be increased at the time of impregnation, and molding failure may occur at the time of molding the substrate.

[0004] Further, the improvement in the precision of the thickness of the sheet after forming is affected not only by the problems of the prepreg, such as the thickness of the prepreg, but also by the pressure and temperature variations in the press during the molding. For example, the flow of the resin does not flow uniformly at the center or the end of the prepreg, but generally, the flow of the resin is larger at the peripheral portion than at the center portion of the mirror plate of the press, and as a result, the peripheral portion is larger than the central portion. It is well-known that they are also thin. The thickness accuracy also decreases due to such variations during molding, and the effect is not sufficient only by increasing the viscosity by adding the filler or the high molecular weight resin as described above. In view of the above, a prepreg having both high precision of board thickness accuracy and excellent moldability is desired.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been completed as a result of intensive studies on the structure of a prepreg in order to solve the problem of compatibility between the thickness accuracy of a substrate after molding and the moldability of the prepreg. I came to. ADVANTAGE OF THE INVENTION This invention can improve the thickness precision of the board | substrate after shaping | molding, maintaining favorable moldability.

[0006]

According to the present invention, there is provided a method for producing a prepreg, comprising impregnating a glass fiber substrate with a curing catalyst dissolved in a solvent, impregnating a thermosetting resin, and heating and drying. It is about. In order to obtain a prepreg excellent in thickness accuracy and moldability after molding, the prepreg contains a large amount of a curing catalyst in the vicinity of the glass fiber base material, and when impregnated with a predetermined resin and dried, the vicinity of the glass fiber base material and the prepreg surface. Has a difference in curing speed. That is, the curing speed in the prepreg has gradation. Due to the difference in curing speed, the vicinity of the glass fiber base material at the time of molding has a function of rapidly curing and maintaining the plate thickness, and the prepreg surface has a function of bonding to another layer and embedding in an inner layer circuit.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is characterized in that a glass substrate is impregnated with a curing catalyst dissolved in a solvent. This is because a large amount of the curing catalyst can be selectively present near the glass substrate by impregnating the glass substrate with the curing catalyst in advance. The solvent used in the present invention is selected in relation to the curing catalyst, and includes, for example, dimethylformamide, methyl cellosolve and the like. The curing catalyst used in the present invention is not particularly limited as long as it can be used for a oxy resin laminate. Usually, an imidazole compound is used, but 2-phenyl-4-methylimidazole, 2-methylimidazole and the like are preferably used because of good catalytic action.

As a result of studies by the inventors, it is preferable that the curing catalyst dissolved in the solvent is impregnated so that the amount of the curing catalyst is 0.01 to 10 parts by weight per 100 parts by weight of the glass fiber base material. It has been found that a prepreg excellent in sheet thickness accuracy and moldability after molding can be obtained with such an amount of the curing catalyst. When the amount of the curing catalyst is less than 0.01 part by weight based on 100 parts by weight of the glass fiber base material, the effect of the gradation of the curing speed in the prepreg by the curing catalyst becomes weak, and the effect of improving the thickness accuracy becomes insufficient. Easy and
If the amount exceeds 10 parts by weight, the effect of the gradation of the curing speed in the prepreg is reduced due to the diffusion of the curing catalyst during the resin impregnation and drying, and the curing speed is too fast during the press molding, and the interlayer adhesion tends to be insufficient. The embedding property is reduced. In addition, the storage stability of the prepreg may not be good.

In the conventional prepreg, there is no difference in the curing speed in the thickness direction of the prepreg of the present invention, all the resin layers have the same curing speed, and impregnation or embedding in a circuit has priority over the thickness accuracy. Was something. For this reason,
It was necessary to reduce the viscosity of the resin in the prepreg during molding, and flow-out occurred during molding, resulting in poor plate thickness accuracy. On the other hand, when the viscosity of the resin is increased, the moldability is reduced due to voids in the fibers and the like.

In the present invention, voids in the fiber may be generated when the curing catalyst solution is impregnated. However, this solution has an extremely low viscosity, and it is not necessary to increase the viscosity of the resin component because it is not necessary to add a polymer component. By virtue of the impregnation method and conditions, it is easy to reduce the voids in the fibers to a level that does not affect the physical properties of the laminated board after molding. In the present invention, additives such as a filler, a surfactant, and a silane coupling agent can be added as needed.

The thermosetting resin used in the present invention is an epoxy resin, a thermosetting polyimide, a cyanate resin, or the like.
Two or more kinds can be used as a mixture. If necessary, additives such as a curing agent, a curing catalyst, a filler, a surfactant, and a silane coupling agent can be added. Usually, this resin is used in the form of a varnish dissolved in a solvent, and it is desirable that the solvent used has good solubility in the resin. In addition, a poor solvent can be used as long as the solvent is not adversely affected. When the resin can be pulverized by pulverization or the like, the resin can be applied to a glass fiber substrate with a powder.

In the present invention, the glass fiber substrate impregnated with the thermosetting resin is usually dried by heating in a drying oven at 150 to 180 ° C. for 1 to 3 minutes.

The prepreg obtained by the present invention can be cut into a suitable length, superposed on a metal foil or an inner circuit board, and molded by heating and pressing to obtain a circuit board or a multilayer circuit board. Alternatively, a circuit board or a multilayer circuit board can be obtained by winding the prepreg in a long state and continuously laminating the prepreg on a metal foil such as a copper foil, an aluminum foil or a nickel foil or on an inner circuit board.

[0014]

The present invention will be described below with reference to examples and comparative examples.

Example 1 <Preparation of curing catalyst solution> 2-Phenyl-4-methylimidazole 0.1 part by weight with respect to 100 parts by weight of dimethylformamide.
086 parts by weight were dissolved to prepare a curing catalyst solution. <Preparation of epoxy resin varnish> 70 parts by weight of a bisphenol A type epoxy resin having an epoxy equivalent of about 450 and a phenol novolak type epoxy resin 3 having an epoxy equivalent of about 190
0 parts were dissolved in 100 parts by weight of methyl ethyl ketone.
To this solution, a solution prepared by dissolving 3 parts by weight of dicyandiamide and 0.15 parts by weight of 2-phenyl-4-methylimidazole in 20 parts by weight of dimethylformamide was added and mixed with stirring. Thus, an epoxy resin varnish was prepared. <Preparation of Pre-preg> The curing catalyst solution was impregnated with glass cloth (thickness 0.10 mm) so that the solution impregnation amount was 35 parts by weight and the curing catalyst amount was 0.03 parts by weight with respect to 100 parts by weight of glass cloth. Then, the epoxy resin varnish prepared as described above has a resin solid content of glass cloth 100.
Impregnated to 110 parts by weight with respect to parts by weight,
Drying was performed for 1.5 minutes in a drying oven at 0 ° C. to obtain a prepreg.

Example 2 A curing catalyst solution obtained by dissolving 1.45 parts by weight of 2-phenyl-4-methylimidazole per 100 parts by weight of dimethylformamide was used. A glass cloth was added to the curing catalyst solution to 100 parts by weight of glass cloth. The solution was impregnated so that the solution impregnation amount was 35 parts by weight and the curing catalyst amount was 0.5 parts by weight. Thereafter, it was made in the same manner as in Example 1.

Example 3 A curing catalyst solution obtained by dissolving 29.6 parts by weight of 2-phenyl-4-methylimidazole with respect to 100 parts by weight of dimethylformamide was used. The solution was impregnated so that the solution impregnation amount was 35 parts by weight and the curing catalyst amount was 8 parts by weight. Thereafter, it was made in the same manner as in Example 1.

Comparative Example 1 The epoxy resin varnish prepared as described above was impregnated so that the resin solid content was 110 parts by weight with respect to 100 parts by weight of the glass cloth, and 1.5 minutes in a drying oven at 170 ° C. It dried and prepared the prepreg. Comparative Example 2 The epoxy resin varnish prepared as described above was impregnated so that the resin solid content was 110 parts by weight based on 100 parts by weight of glass cloth, and dried in a drying oven at 170 ° C. for 3 minutes to prepare a prepreg. Created.

Using the prepreg obtained as described above, a double-sided copper-clad laminate and a four-layer circuit board were prepared by the following method, and their characteristics were evaluated. <Molding of Laminated Plate> A thickness of 18
A μm copper foil was overlaid. Then, a pressure of 40 kgf / cm ² ,
Heat and pressure molding was performed at a temperature of 170 ° C. for 60 minutes to obtain a double-sided copper-clad laminate having an insulating layer thickness of 0.1 mm. <Evaluation of laminated board> The thickness accuracy and formability are 500 m in size.
The measurement was performed on a double-sided copper-clad laminate of mx500 mm whose copper foil was removed by etching. The plate thickness accuracy was measured by setting 36 measurement points in a grid pattern and measuring the thickness. The average value and the range were obtained and defined as the thickness accuracy. Formability is size 5
The substrate having a size of 00 mm × 500 mm was visually and visually checked with an optical microscope for the presence or absence of voids and other abnormalities. The peel strength of 18μm copper foil is JIS
Performed according to C 6481. For the measurement of solder heat resistance, only one side was etched, cut into a size of 50 mm × 50 mm, and then subjected to a moisture absorption treatment under pressure cooker conditions of 121 ° C. and 2.0 atm for 1 hour and 2 hours. Subsequently, after immersion in a 260 ° C. solder bath for 120 seconds, the evaluation of blistering and measling was confirmed visually and by an optical microscope.

<Preparation of Four-Layer Circuit Board> The surface of a copper foil (thickness: 35 μm) of a double-sided copper-clad laminate having a thickness of 0.8 mm as an inner layer plate is subjected to oxidation treatment (blackening treatment), and the upper and lower surfaces thereof are formed as described above. One prepreg was laminated, and 18 μm copper foil was laminated on top and bottom of the prepreg, and the pressure was 40 kgf / cm ² and the temperature was 170 ° C.
It was heated and pressed for 0 minutes to form a four-layer circuit board. <Evaluation of 4-layer circuit board> The thickness accuracy is 500 mm in size.
With respect to a substrate of × 500 mm, 36 measurement points were set in a grid pattern, and the thickness was measured. The average value and the range were obtained and defined as the thickness accuracy. Formability is 500mm x 500mm in size
The presence of voids in the substrate and the presence of other abnormalities were confirmed visually and by an optical microscope. The inner layer peel strength was measured by measuring the peel strength at the interface between the inner layer blackened copper foil and the prepreg of the substrate according to JIS C6481. The solder heat resistance was measured by etching only one side and cutting it into a size of 50 mm × 50 mm.
The moisture absorption treatment was performed for 1 hour and 2 hours under a pressure cooker condition of 2.0 ° C. and 2.0 atm. Subsequently, after immersion in a 260 ° C. solder bath for 120 seconds, the evaluation of blistering and measling was confirmed visually and by an optical microscope.

Table 1 shows the evaluation results.

[Table 1]

The prepregs obtained in Examples 1, 2, and 3 have excellent plate thickness accuracy and excellent moldability. Comparative Example 1 is an example of a prepreg prepared by a conventional method, and is inferior in thickness accuracy as compared with the embodiment. In Comparative Example 2, the resin has a high viscosity due to a long heating time during the preparation of the prepreg, and has a high plate thickness accuracy. However, the laminate moldability and the circuit embedding property of the four-layer circuit board are poor, and voids remain.

[0023]

As is apparent from the above results, in the present invention, a prepreg having high thickness accuracy and excellent moldability can be easily obtained, and a laminate having excellent thickness accuracy can be obtained. Can be.

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Claims (4)

[Claims] 1. A method for producing a prepreg, comprising impregnating a glass fiber substrate with a curing catalyst dissolved in a solvent, impregnating a thermosetting resin, and heating and drying. 2. The method according to claim 1, wherein the curing catalyst is impregnated with 0.01 to 10 parts by weight per 100 parts by weight of the glass fiber base material. 3. A method of impregnating a glass fiber substrate with a curing catalyst dissolved in a solvent, impregnating a thermosetting resin, heating and drying, and heat-forming one or more prepregs. A method for manufacturing a laminated plate, which is characterized by the following. 4. The method according to claim 3, wherein the curing catalyst is impregnated with 0.01 to 10 parts by weight per 100 parts by weight of the glass fiber base material.