JP2008030246A - Single-sided metal foil clad laminated sheet and printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single-sided metal foil clad laminated sheet which uses a polypropyrene mold release film comprising an inexpensive material easy to obtain, and ensures the releasability of the polypropyrene mold release film and the adhesion with a prepreg at the time of secondary molding in a well-balanced state, and also to provide a printed wiring board using it. <P>SOLUTION: The single-sided metal foil clad laminated shot is obtained by molding under heating and pressure, a laminate which is produced by: superposing a metal foil on one side of a prepreg obtained by impregnating a glass fabric with epoxy resin varnish and drying the impregnated glass fabric; and superposing a mold release film on the other side of the prepreg. The polypropyrene mold release film is used as the mold release film and the glass transition temperature Tg of the laminated sheet is set so as to fall below the glass transition temperature Tg of the laminated sheet in a perfectly cured state by 5-25°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a single-sided metal foil-clad laminate used as a material for multilayer printed wiring boards and the like, and a printed wiring board using the same.

  Conventionally, single-sided metal foil-clad laminates (hereinafter also referred to as single-sided plates) and multilayer printed wiring boards using the same have been manufactured, for example, as follows. First, a prepreg used in the production of a printed wiring board is prepared by preparing a resin composition mainly composed of an epoxy resin as a resin varnish, impregnating the resin varnish into a substrate made of a glass woven fabric, and then drying it. Manufactured in a semi-cured state (B stage). Next, a metal foil is overlaid on one surface of the prepreg, and a release film is overlaid on the other surface to form a laminate, and this laminate is sandwiched between mold plates (mirror plates) and subjected to heat and pressure molding. Thus, a single-sided plate is obtained.

  When manufacturing a multilayer printed wiring board, the peeled surface from which the release film of the single-sided board obtained as described above is peeled off is applied to a double-sided printed wiring board in which circuits are arranged on both sides, or the double-sided printed wiring board is formed by prepreg A multilayer printed wiring board whose surface layer is a single-sided board can be obtained by stacking a plurality of layers on top of each other via a prepreg and performing heat-pressure molding.

  Conventionally, a film obtained by kneading a small amount of an inorganic filler in a fluorine-based material such as a polyvinyl fluoride resin has been mainly used as the release film for the single-sided plate. The fluorine-based material has good releasability from the epoxy resin, and the inorganic filler can provide appropriate unevenness on the resin surface of the single-sided plate, thereby improving the adhesion to the prepreg during secondary molding.

  However, in recent years, fluorine-based release films are relatively expensive and have become difficult to obtain due to problems such as expanded applications.

On the other hand, a polypropylene release film is partially used as an inexpensive release film (for example, Patent Document 1). However, the melting point is as low as about 170 ° C., the releasability from the epoxy resin, and the single-sided plate. It has been considered difficult to ensure a good balance of the adhesiveness during the secondary molding of the resin surface (film peeling surface) and the prepreg.
Japanese Patent Laid-Open No. 10-303554

  The present invention has been made in view of the circumstances as described above, and uses a polypropylene release film made of an inexpensive and easily obtainable material. The peelability of the polypropylene release film, the prepreg at the time of secondary molding, It is an object of the present invention to provide a single-sided metal foil-clad laminate and a printed wiring board using the same.

  In order to solve the above problems, the single-sided metal foil-clad laminate of the present invention is characterized by the following.

  First, a glass woven fabric is impregnated with an epoxy resin varnish and dried, and a metal foil is stacked on one side of a prepreg obtained by drying, and a laminate in which a release film is stacked on the other side is heated and pressurized. In the single-sided metal foil-clad laminate obtained by molding, the release film is a polypropylene release film, and the glass transition temperature Tg of the laminate is 5 ° C. higher than the glass transition temperature Tg of the laminate in the fully cured state. It is characterized by being set low by -25 ° C.

  Second, in the first invention, the polypropylene release film has a surface roughness of 5 μm or more and 10 μm or less.

  Third, in the first or second invention, the polypropylene release film has a thickness of 25 μm or more and 50 μm or less.

  Fourthly, in any one of the first to third inventions, at the time of heat and pressure molding, molding is performed at the maximum product temperature in the range from the temperature 20 ° C. to the melting point lower than the melting point of the polypropylene release film. It is characterized by being.

Fifth, in any one of the first to fourth inventions, the molding is performed at a molding pressure of 5 kg / cm ² or more and 10 kg / cm ² or less during cooling after heat and pressure molding. Features.

  Sixthly, the printed wiring board of the present invention is characterized by using the single-sided metal foil-clad laminate of any of the first to fifth inventions.

  According to the first invention, a polypropylene release film is used as the release film, and the glass transition temperature Tg of the laminate is set to be 5 ° C. to 25 ° C. lower than the glass transition temperature Tg of the laminate in the fully cured state. Therefore, while maintaining the advantage that a polypropylene release film is relatively inexpensive and easy to obtain than a release film using a fluororesin, the release property of the release film and the adhesion to the prepreg during secondary molding are improved. It becomes possible to ensure a good balance.

  According to the second invention, since the surface roughness of the polypropylene release film is 5 μm or more and 10 μm or less, in addition to the effects of the invention described above, the peelability of the release film and the close contact with the prepreg at the time of secondary molding The property can be further improved.

  According to the third aspect of the invention, since the thickness of the polypropylene release film is 25 μm or more and 50 μm or less, in addition to the effects of the above invention, the generation of film wrinkles during product processing can be suppressed.

  According to the fourth invention, at the time of heat and pressure molding, since the molding is performed at the highest product temperature in the range from the temperature 20 ° C. lower than the melting point of the polypropylene release film to the melting point, in addition to the above effects, The polypropylene release film can be prevented from fusing and becoming difficult to peel off, and the molding time during production can be shortened to improve efficiency.

According to the fifth invention, since the molding is performed at a molding pressure of 5 kg / cm ² or more and 10 kg / cm ² or less at the time of cooling after heat and pressure molding, in addition to the above effects, epoxy resin and polypropylene By reducing the residual stress of the release film, the effect of improving the film peelability due to the heat shrinkage of the polypropylene release film can be further enhanced.

  According to the sixth invention, since the single-sided metal foil-clad laminate of the first to fifth inventions is used, a printed wiring board having high adhesion to the prepreg at the time of secondary molding can be obtained.

  Embodiments of the present invention will be described.

  The single-sided metal foil-clad laminate of the present invention was obtained by impregnating a glass woven fabric with an epoxy resin varnish and overlaying a metal foil on one side of a prepreg obtained by drying and a mold release film on the other side. The laminate is obtained by heating and pressing. As the release film, a polypropylene release film that is inexpensive and easily available is used. In the single-sided metal foil-clad laminate of the present invention, the glass transition temperature Tg is set to be 5 ° C to 25 ° C lower than the glass transition temperature Tg of the laminate in the fully cured state (when 5 ° C is lower and 25 ° C). Including low cases). Here, the glass transition temperature Tg is JIS C6481 5. 17.1 Value measured by TMA method. The glass transition temperature Tg can be adjusted by adjusting heating and pressing conditions such as heating temperature, molding pressure, and heating and pressing time. When the prepreg is sufficiently heated and pressed to be in a completely cured state where the glass transition temperature Tg has reached its peak, the adhesion with the prepreg during the secondary molding is reduced. On the other hand, if the heating and pressing conditions are insufficient and the glass transition temperature Tg is lower than 25 ° C., the adhesion between the release film and the resin becomes too strong, and the peelability is deteriorated. Therefore, by setting the glass transition temperature Tg of the single-sided metal foil-clad laminate of the present invention within the above range, it is possible to ensure a good balance between the peelability of the release film and the adhesion between the prepreg during secondary molding. It becomes possible.

  The prepreg can be obtained as follows. A glass woven fabric is used as the substrate. In addition, an epoxy resin is used as a matrix resin, and a resin varnish is prepared by dissolving a curing agent, a curing accelerator, or the like, if necessary, in a solvent. For example, a glass woven fabric is wound in a roll shape so that it can be continuously supplied, and an epoxy resin varnish is placed in a dip tank. The glass woven fabric is sent out sequentially, the glass woven fabric is impregnated with the resin varnish by passing through the dip tank, and the solvent is removed by passing through the dryer, and the prepreg is made semi-cured, that is, B-staged. Get.

  The material of the metal foil stacked on one surface of the prepreg is not particularly limited, and for example, copper foil, aluminum foil, or the like can be used. The dimensions and thickness can also be set as appropriate according to the application.

  Moreover, the polypropylene release film to be overlaid on the other surface of the prepreg usually has a melting point of about 170 ° C. The polypropylene release film preferably has a surface roughness of 5 μm or more and 10 μm or less. Here, the surface roughness is a value according to the arithmetic average height Ra (JIS B0601 4.2.1) of the contour curve. When the surface roughness is within the above range, the release film peelability and the adhesiveness during secondary molding can be ensured better. If the surface roughness is too small, the releasability is improved, but the adhesion to the prepreg at the time of secondary molding is lowered, and if it is too large, the adhesion to the release film becomes too strong and the peelability tends to be poor. There is. The surface roughness of the polyethylene release film can be adjusted using a method of kneading an inorganic filler or a processing method such as sand mud, but is not particularly limited.

  Moreover, it is preferable that the thickness of a polypropylene release film is 25 micrometers or more and 50 micrometers or less. Single-sided metal foil-clad laminates are mainly produced by stacking prepreg and metal foil on both sides via a release film to produce two single-sided plates as a set, and in this state they are bonded to any size. It is common to be processed and distributed. The reason is that if the release film is peeled off, the laminate is warped due to residual stress at the time of molding the metal foil and the epoxy resin layer, and is difficult to handle. In addition, the melting point of polypropylene is about 170 ° C., and the release film may be melted by heat at the time of processing the laminated plate and may remain as wrinkles at the ends. In order to prevent this, the release film is preferably as thin as possible. On the other hand, if the release film is too thin, it may be difficult to manufacture and handle the release film. Therefore, the thickness of the polypropylene release film is preferably in the above range.

  In addition, the single-sided metal foil-clad laminate of the present invention is molded at the highest product temperature in the range from a temperature 20 ° C. lower than the melting point of the polypropylene release film to the melting point during heat and pressure molding. preferable. When the molding temperature completely exceeds the melting point of the polypropylene release film, the polypropylene release film melts and becomes difficult to peel off. When the molding temperature exceeds 20 ° C. below the melting point, the curing of the resin proceeds. Molding time can be very long and efficiency can be compromised.

Moreover, it is preferable that the single-sided metal foil-clad laminate of the present invention is molded at a molding pressure of 5 kg / cm ² or more and 10 kg / cm ² or less during cooling after heat and pressure molding. If it does in this way, the residual stress of an epoxy resin and a polypropylene release film can be made small, and the improvement effect of the film peelability by the heat shrink of a polypropylene release film can be heightened more.

  Furthermore, according to this invention, a printed wiring board with high adhesiveness with the prepreg at the time of secondary shaping | molding can be obtained using the single-sided metal foil clad laminated board of said structure.

Next, examples and comparative examples of the present invention will be shown. In the examples and comparative examples, “%” is based on weight unless otherwise specified.
(Example 1)
As a resin varnish, an epoxy resin was used as a matrix resin, and the following resin composition was prepared.

Epoxy resin
Toto Kasei Co., Ltd .: YDB-500EK80 72.5%
Toto Kasei Co., Ltd. product: YDCN-220EK75 6.27%
Hardener
Dicyandiamide 1.41%
solvent
Dimethylformamide 9.88%
Propylene glycol monomethyl ether 9.91%
Curing accelerator
Imidazole 0.03%
As a base material, a glass woven cloth having a thickness of about 100 μm (manufactured by Nitto Boseki Co., Ltd .: WEA116) is used. After impregnating the resin varnish through a resin varnish dip tank, the solvent was removed through a dryer to obtain a semi-cured (B stage) prepreg (resin amount 45%).

  Next, a copper foil having a thickness of 18 μm (Furukawa Circuit Foil Co., Ltd .: GT-18 μ) is overlaid on one surface of the prepreg, and the other surface has a thickness of 40 μm, a surface roughness of 7 μm, and a melting point of 170. A polypropylene release film (manufactured by Somar Co., Ltd .: Soma Blast) at a temperature of 0 ° C. (value by DSC method) was layered to obtain a laminate.

Next, the laminated body produced above was sandwiched between mold plates (mirror plates) and subjected to heat and pressure molding. The molding conditions at the time of heat and pressure molding were set at 170 ° C. for 60 minutes and 30 kg / cm ² . The molding pressure during cooling after heat-press molding of the laminate was 30 kg / cm ² . A single-sided plate as a product of the present invention was produced as described above.

  The glass transition temperature Tg of the product of the present invention produced above was measured by the method described above. This single-sided metal-clad laminate was completely cured, and the glass transition temperature Tg was 140 ° C.

  Moreover, the surface roughness of said polypropylene release film was measured by Tokyo Seimitsu Co., Ltd. product: SURFCOM E-RM-S01A E-MD-S39A.

  Moreover, the film peelability of the product of the present invention was measured by measuring the frequency of occurrence of a product failure rate due to the peel strength being strong after carrying out a peeling operation on 100 products.

  In addition, the adhesion at the time of secondary molding is performed by secondary molding of a single-sided plate made of the product of the present invention and a prepreg (made by Matsushita Electric Works Co., Ltd .: R-1661) having a thickness of 0.1 mm and a resin amount of 52%. The peel strength at the interface between the prepreg and the single-sided plate was measured with an autograph (manufactured by Shimadzu Corporation: AGS-500B).

  Furthermore, the occurrence of film wrinkles was made by stacking 20 sheets of the product of the present invention and cutting them with an auto cut-and-sew, and examining the presence or absence of wrinkles at the ends.

The above evaluation results are shown in Table 1.
(Example 2)
In Example 1, a single-sided plate as a product of the present invention was produced in the same manner except that the maximum product temperature during heat and pressure molding was set to 160 ° C., and the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.
(Example 3)
In Example 1, a single-sided plate as a product of the present invention was produced in the same manner except that the molding pressure during cooling was 10 kg / cm ^2, and the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.
Example 4
A single-sided plate as a product of the present invention was produced in the same manner as in Example 1 except that a polypropylene release film having a surface roughness of 4 μm was used, and the same evaluation as in Example 1 was performed. In this case, compared to Example 1, there was a tendency that the adhesion at the time of secondary molding was slightly reduced, but this was in a practical range.
(Example 5)
In Example 1, a single-sided plate as a product of the present invention was manufactured in the same manner except that a polypropylene release film having a surface roughness of 12 μm was used, and the same evaluation as in Example 1 was performed. In this case, the value of the film peelability tended to be slightly higher than that in Example 1, but was in a practical range.
(Example 6)
A single-sided plate as a product of the present invention was produced in the same manner as in Example 1 except that a polypropylene release film having a thickness of 20 μm was used, and the same evaluation as in Example 1 was performed. In this case, the handleability tended to be difficult, but was in a practical range.
(Example 7)
In Example 1, a single-sided plate as a product of the present invention was manufactured in the same manner except that a polypropylene release film having a thickness of 60 μm was used, and the same evaluation as in Example 1 was performed. In this case, compared with Example 1, there was a tendency that the generation of film wrinkles at the time of processing started, but it was in a practical range.
(Comparative Example 1)
In Example 1, a single-sided plate as a comparative example product was produced in the same manner except that the maximum product temperature during heat and pressure molding was set to 175 ° C., and the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1. The glass transition temperature of the comparative product was 140 ° C., which was the same as the fully cured state value.
(Comparative Example 2)
In Example 1, a single-sided plate as a comparative product was produced in the same manner except that no molding pressure was applied during cooling, and the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1. The glass transition temperature of the comparative product was 110 ° C., which was 30 ° C. lower than the value of the fully cured state.

From Table 1, it can be seen that the product of the present invention can ensure a good balance between the peelability of the polypropylene release film and the adhesion to the prepreg during secondary molding, as compared with the comparative product.

Claims (6)

  A glass woven fabric impregnated with an epoxy resin varnish and dried to obtain a laminate with a metal foil on one side of the prepreg and a release film on the other side. In the obtained single-sided metal foil-clad laminate, the release film is a polypropylene release film, and the glass transition temperature Tg of the laminate is 5 ° C. to 25 ° C. lower than the glass transition temperature Tg of the laminate in the fully cured state. A single-sided metal foil-clad laminate, characterized by being set.   The single-sided metal foil-clad laminate according to claim 1, wherein the surface roughness of the polypropylene release film is 5 µm or more and 10 µm or less.   The single-sided metal foil-clad laminate according to claim 1 or 2, wherein the polypropylene release film has a thickness of 25 µm or more and 50 µm or less.   4. The molding according to claim 1, wherein the molding is performed at the highest product temperature in a range from a temperature 20 ° C. lower than the melting point of the polypropylene release film to the melting point at the time of heat-pressure molding. The single-sided metal foil-clad laminate as described. The single-sided metal according to any one of claims 1 to 4, wherein the single-sided metal is molded at a molding pressure of 5 kg / cm ² or more and 10 kg / cm ² or less during cooling after the heat and pressure molding. Foil-clad laminate.   A printed wiring board using the single-sided metal foil-clad laminate according to any one of claims 1 to 5.