JP2008239826A - Method for producing resin film-laminated prepreg - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently producing a resin film-laminated prepreg, enabling the prepreg's moisture absorption to be suppressed with slight residual voids between the prepreg and the resin film. <P>SOLUTION: The method for producing the resin film-laminated prepreg comprises a step (A) of impregnating a fiber base material with a thermosetting resin composition, a step (B) of heating and drying the thermosetting resin composition impregnated in the fiber base material to form a prepreg with the thermosetting resin in a half-cured state, and a step (C) of making resin films adhere to the obverse and reverse surfaces of the prepreg heated by remaining heat by the above drying operation to effect hot-pressing the prepreg and the resin films together. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a resin film laminated prepreg used for producing a multilayer printed wiring board having an IVH structure.

  In recent years, as electronic devices such as portable communication information terminal devices such as mobile phones and PDAs and small AV devices such as digital still cameras have become smaller and more functional, printed wiring boards are required to be thinner and higher in density. ing.

  In order to achieve high density of the printed wiring board, a multilayer printed wiring board using a so-called build-up method, in which the occupied area is reduced by multilayering the substrate, is used. In particular, a build-up multilayer printed wiring board capable of connecting arbitrary layers with an inner via hole (IVH) can be densified and can increase the degree of freedom in design.

  Electrical connection between conductor layers of multilayer printed wiring boards is made through through holes or via holes. In recent years, prepregs are drilled by irradiating laser light, and screen printing is used for the holes. Then, a filled via is formed by filling a conductive paste (see Patent Document 1). For example, as a method for manufacturing an all-layer IVH structure multilayer printed wiring board, a method of connecting the layers by forming filled vias using a conductive paste composed of copper powder, epoxy resin, and a curing agent is used. ing.

  Thus, when forming an IVH structure using a conductive paste, through holes are formed by laser light irradiation in the thickness direction of a prepreg whose front and back surfaces are covered with a releasable resin film. As a masking material, the through-hole is filled with a conductive paste by screen printing or the like, and then the resin film is peeled off. Then, for example, the prepreg is sandwiched between a plurality of double-sided printed wiring boards, and the whole is heated and pressed to be compression-cured.

  Alternatively, after removing the resin film, prepare two prepregs each having a metal foil bonded to one side, and the surface of the metal foil of the prepreg is on the outside, and at least two layers of wiring patterns between them The whole circuit board is sandwiched, and the whole is heated and pressed to compress and cure to connect the layers. Thereafter, the metal foil on the surface is patterned into a predetermined shape. Using the double-sided circuit board thus prepared as a core, a multilayer printed wiring board is manufactured by laminating a prepreg filled with a conductive paste and a metal foil and multilayering them as described above. The

As described above, in the method of taking the interlayer connection with the conductive paste, when filling the via hole with the conductive paste, a process of attaching a resin film to the prepreg as a masking material is necessary, but conventionally, it is generally used. After the prepreg supplier manufactures the prepreg using the manufacturing equipment, the printed wiring board manufacturer purchases it, and as a separate process from the prepreg manufacturing, a resin film as a masking material is pressure-bonded to the prepreg. Then, laser processing, filling of conductive paste, etc. were performed.
JP 2004-059896 A

  However, when the prepreg once cooled is heated again and a resin film such as polyester is pressure-bonded, the adhesion of the film is not necessarily good, and there is a problem that a void remains between the prepreg and the resin film.

  Furthermore, if a time is required from the time of manufacturing the prepreg to the time when the resin film is pressure-bonded, the prepreg absorbs moisture, and there is a problem that the heat resistance of the printed wiring board manufactured using such a prepreg is affected.

  The present invention has been made in view of the circumstances as described above, there is little void remaining between the prepreg and the resin film, moisture absorption of the prepreg can be suppressed, and a resin film laminated prepreg is efficiently obtained. It is an object of the present invention to provide a method for producing a resin film laminated prepreg that can be used.

  The present invention is characterized by the following in order to solve the above problems.

  1stly, the manufacturing method of the resin film laminated prepreg of this invention is the process (A) which impregnates a thermosetting resin composition in a fiber base material, and heat-drys the thermosetting resin composition impregnated in the fiber base material. The step (B) of forming the prepreg in which the thermosetting resin is in a semi-cured state, and the resin film is brought into close contact with the front and back surfaces of the prepreg heated by the residual heat by heating and drying. And a step (C) of crimping.

  Second, in the first manufacturing method, the steps (A) to (C) are performed as a series of steps by continuously conveying a long fiber substrate downstream.

  Thirdly, in the second manufacturing method, in the step (C), a long resin film is fed to the front and back surfaces of the continuously conveyed prepreg heated by the residual heat by heat drying, and these are pressure-bonded. A resin film is brought into close contact with the front and back surfaces of the prepreg by passing between rolls, and these are thermocompression-bonded.

  Fourth, in any one of the first to third manufacturing methods, after the prepreg is formed in the step (B), until the resin film is adhered to the front and back surfaces of the prepreg in the step (C), The temperature is maintained at 40 ° C. or higher, and a resin film is thermocompression bonded to the front and back surfaces of the prepreg heated to 40 ° C. or higher.

  Fifth, in any one of the first to fourth manufacturing methods, the resin film is used as a masking material when a through-hole formed in the prepreg is filled with a conductive paste by a screen printing method. To do.

  Sixth, in any one of the first to fifth manufacturing methods, the thermosetting resin is an epoxy resin, and the resin film is a polyethylene film, a polypropylene film, or a polyester film.

  According to the first aspect of the present invention, after the prepreg is formed by heat drying of the thermosetting resin composition, the resin film is thermocompression bonded to the front and back surfaces of the prepreg that is heated by the residual heat by heat drying. The resin film is pressure-bonded in a state where the surface state of the prepreg is not fixed by curing shrinkage. Therefore, the adhesiveness of the resin film to the prepreg is good, and the void residue between the prepreg and the resin film can be reduced.

  And, after forming the prepreg by heat drying of the thermosetting resin composition, it is possible to suppress moisture absorption of the prepreg by immediately pressing the resin film in a state where it is heated by the residual heat by heat drying. it can.

  Furthermore, since the residual heat of the thermosetting resin composition heat drying process is used for pressure bonding of the resin film, there is no need for a separate heating device for heat pressure bonding of the resin film, and the resin film is laminated efficiently. A prepreg can be obtained.

  According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, the step of thermocompression bonding the resin film to the front and back surfaces of the prepreg is performed as a series of steps downstream of the prepreg manufacturing process. By simply incorporating a device for transporting and compressing a resin film into the prepreg manufacturing equipment used, it is possible to easily and reliably reduce voids between the prepreg and the resin film and further suppress moisture absorption of the prepreg. it can.

  According to the third aspect of the invention, in addition to the effect of the second aspect of the invention, the prepreg and the resin film can be securely brought into close contact with each other by the pressure-bonding roll, and the void remaining between the prepreg and the resin film can be reliably ensured. Can be reduced.

  According to the fourth invention, in addition to the effects of the first to third inventions, voids between the prepreg and the resin film can be more reliably reduced, and moisture absorption of the prepreg can be more reliably suppressed. can do.

  According to the fifth aspect of the invention, in addition to the effects of the first to fourth aspects of the invention, the obtained resin film laminated prepreg is used as a masking material, and a conductive paste is formed by screen printing on the through-hole formed in the prepreg. By filling the substrate, it is possible to produce a printed wiring board with good yield and excellent heat resistance.

  According to the sixth invention, in addition to the effects of the first to fifth inventions, even when a typical epoxy resin is used as an insulating material for a printed wiring board, a void between the prepreg and the resin film is used. Can be reliably reduced, and moisture absorption of the prepreg can be reliably suppressed.

  The present invention has the features as described above, and an embodiment thereof will be described below.

  As the thermosetting resin used in the present invention, an appropriate one can be selected as long as it is used as an insulating material for a printed wiring board. Specific examples thereof include an epoxy resin, a phenol resin, and a polyimide resin. , Polyphenylene oxide resin, cyanate resin, or those obtained by modifying these resins. Among these, an epoxy resin is preferable in consideration of moldability, compatibility with the conductive paste filled in the via, storage stability, and the like.

  The epoxy resin can be used without particular limitation as long as it has two or more epoxy groups in one molecule. Specific examples thereof include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolak type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, dicyclopentadiene. Type epoxy resin, alicyclic epoxy resin, polyfunctional epoxy resin (epoxy resin containing three or more epoxy groups in one molecule) and the like. For the purpose of imparting flame retardancy, an epoxy resin containing a halogen compound such as bromine, an epoxy resin containing phosphorus, or the like can also be used. An epoxy resin may be used individually by 1 type, and may be used in combination of 2 or more type.

  A curing agent can be blended in the thermosetting resin composition using an epoxy resin. As the curing agent, those generally used can be used without particular limitation. Specific examples thereof include amine curing agents such as dicyandiamide and carboxylic acid hydrazide; 3- (3,4-dichlorophenyl) -1, Urea curing agents such as 1-dimethylurea; acid anhydride curing agents such as phthalic anhydride, methyl nadic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride; aromas such as diaminodiphenylmethane and diaminodiphenylsulfonic acid Group amine-based curing agents; phenolic compound-based curing agents such as bisphenol A, bisphenol F, phenol novolac, cresol novolac, and pyrogallol. These may be used alone or in combination of two or more. From the viewpoint of the stability and workability of the composition, it is desirable to use a solid latent curing agent powder such as dicyandiamide.

  Furthermore, a curing accelerator can be blended in the thermosetting resin composition using an epoxy resin together with the above curing agent. Specific examples of the curing accelerator include imidazoles such as 2-methylimidazole and 2-phenylimidazole; tertiary amines such as triethylenediamine and dimethylbenzylamine; and organic phosphines such as triphenylphosphine. These may be used alone or in combination of two or more.

  Furthermore, thermosetting resin compositions using epoxy resins include flame retardant aids, thickeners, various fillers that play a role in controlling thermal expansion coefficient, toughening laminates, and elastomer fine particles. Additives can be blended. Specific examples of fillers include silica, aluminum hydroxide, magnesium hydroxide, glass powder, alumina, magnesium oxide, titanium dioxide, calcium silicate, calcium carbonate, clay, talc, and other inorganic fillers; fluorine resin, polyimide resin, benzoguanamine Examples thereof include organic fillers such as resins and epoxy resins. Specific examples of the elastomer fine particles include acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), ethylene propylene rubber (EPM), ethylene propylene diene rubber (EPDM), chloroprene. Rubber (CR), butyl rubber, urethane rubber, silicone rubber, polysulfide rubber, hydrogenated nitrile rubber, polyether-based special rubber, fluorine rubber, acrylic rubber, epichlorohydrin rubber, propylene oxide rubber, ethylene vinyl acetate copolymer, ethylene acrylic rubber, etc. Is mentioned.

  Furthermore, for thermosetting resin compositions using epoxy resins, additives such as thermal polymerization inhibitors, plasticizers, leveling agents, antifoaming agents, UV absorbers, flame retardants, and coloring are added as necessary. Pigments and the like can be blended.

  A thermosetting resin composition using an epoxy resin can be prepared by uniformly mixing the epoxy resin and each of the above-described components blended as necessary using a mixer or a blender. At this time, if necessary, it may be diluted with a solvent and prepared as a varnish. As the diluting solvent, dimethylformamide, dimethylacetamide, methyl ethyl ketone, methoxypropanol or the like is used.

  Also in a thermosetting resin composition using a thermosetting resin other than an epoxy resin, a thermosetting resin composition can be prepared according to the above.

  A woven fabric or a non-woven fabric is used as the fiber base material impregnated in the thermosetting resin composition. Specific examples of the woven fabric include a glass cloth in which hundreds of filaments having a diameter of 5 to 15 μm are woven as warp yarns and weft yarns. On the other hand, specific examples of the nonwoven fabric include glass nonwoven fabric (glass paper), linter paper, kraft paper, and the like, which is made by cutting glass fibers into several mm to several tens of mm and bonded with water-dispersed epoxy resin or the like. Paper base materials, organic fiber nonwoven fabrics, and the like. Specific examples of the organic fiber forming the organic fiber nonwoven fabric include aramid fiber, polyester fiber, polyimide fiber, polyacrylic fiber, and the like. Among them, aramid fiber is a fiber material suitable for prepreg because it has high heat resistance and a small coefficient of thermal expansion, and can be well processed for via holes by a carbon dioxide laser processing machine.

  The thickness of the fiber base material is appropriately determined in consideration of the bendability of the prepreg and securing necessary rigidity, and is, for example, 10 μm to 300 μm.

  In the present invention, the step (A) of impregnating the fiber base material with the thermosetting resin composition, and the thermosetting resin composition impregnated into the fiber base material are dried by heating so that the thermosetting resin is in a semi-cured state. The step (B) of forming the prepared prepreg, and the step (C) of attaching the resin films to the front and back surfaces of the prepreg heated by the residual heat by heat drying and thermocompression bonding them are generally used. An apparatus for supplying a resin film can be attached to the existing prepreg manufacturing apparatus, and the process can be performed continuously.

  FIG. 1 is a diagram schematically showing an embodiment of a prepreg manufacturing apparatus used in a prepreg manufacturing method according to the present invention. In the same figure, the code | symbol 1 has shown the prepreg manufacturing apparatus as a whole. The prepreg manufacturing apparatus 1 includes a resin-impregnated tank 20 that impregnates the above-described thermosetting resin composition 21 into the band-shaped fiber base material 2 fed from the unwinding roll 11 and the thermosetting resin composition 21. A dryer 30 that heat-drys the fiber substrate 2 to make the thermosetting resin composition 21 in a semi-cured state, and a resin that is thermocompression-bonded by supplying the resin films 4a and 4b to both sides of the prepreg 3 thus obtained. A film supply device 40 and a cutting machine 50 that cuts the strip-shaped prepreg 3 formed by thermocompression bonding of the resin films 4a and 4b into sheets of a certain size are provided.

  Moreover, the prepreg manufacturing apparatus 1 is provided with the conveyance roll equipment for conveying the fiber base material 2 and the prepreg 3 which are continued in strip | belt shape, and this conveyance roll equipment is downstream of the fiber base material 2 wound by roll shape. And a plurality of transport rolls including a pair of squeeze rolls 13a and 13b, and the tension is controlled by these transport rolls. However, the fiber base material 2 and the prepreg 3 are continuously conveyed downstream.

  The fiber base material 2 delivered from the unwinding roll 11 is introduced into the resin impregnation tank 20 in which the liquid thermosetting resin composition 21 is stored in a form supported and supported by the dip roll 12, and the thermosetting resin. The composition 21 is impregnated. Although not shown in the figure, the resin impregnation tank 20 can circulate the thermosetting resin composition 21 with a separate tank for storing the thermosetting resin composition 21. The temperature and viscosity of the thermosetting resin composition 21 in 20 are automatically controlled.

  The fiber base material 2 impregnated with the thermosetting resin composition 21 is pulled up to a pair of squeeze rolls 13a and 13b on the upper downstream side of the resin impregnation tank 20, and passes between the squeeze rolls 13a and 13b. Excess thermosetting resin composition 21 is squeezed to adjust the amount of impregnation. For example, when an epoxy resin varnish is impregnated into a woven fabric or non-woven fabric, the resin content can be set to 30% by mass to 80% by mass with respect to the total amount of the prepreg.

  Thereafter, the fiber base material 2 impregnated with the thermosetting resin composition 21 is introduced into a dryer 30, and the thermosetting resin is semi-cured by heat drying to form a prepreg.

  As the dryer 30, for example, a generally used vertical drying furnace, horizontal drying furnace, or the like can be used. As a drying method, a method of applying contact heat by hot air to both surfaces of the fiber base material 2 impregnated with the thermosetting resin composition 21, a method of applying radiant heat by far infrared rays using a radiant panel, or a combination of these methods, etc. Applies.

  The drying temperature in the dryer 30 varies depending on the type of thermosetting resin used, but is generally between 80 ° C. and 200 ° C., and the drying time is generally between 2 minutes and 10 minutes.

  The prepreg 3 drawn out from the dryer 30 is sent to a resin film supply device 40 arranged on the downstream side. The resin film supply device 40 includes a pair of resin film unwinding rolls 14 a and 14 b and a pair of pressure-bonding rolls 15 a and 15 b, and the resin film unwinding roll 14 a is formed of the prepreg 3 drawn out from the dryer 30. The resin film 4 a is supplied to one surface, and the resin film unwinding roll 14 b supplies the resin film 4 b to the other surface of the prepreg 3. Then, the resin films 4 a and 4 b are bonded to the respective surfaces of the prepreg 3 by passing between the pressure-bonding rolls 15 a and 15 b with the prepreg 3 being sandwiched between the resin films 4 a and 4 b and bringing them into close contact with each other.

  At this time, the prepreg 3 conveyed to the positions of the pressure rolls 15a and 15b is in a state heated to a predetermined temperature by the residual heat after drying by heating in the dryer 30, and the prepreg 3 is removed by the resin films 4a and 4b. The resin films 4a and 4b are thermocompression bonded to the respective surfaces of the prepreg 3 by passing between the pressure-bonding rolls 15a and 15b.

  The temperature of the prepreg 3 at the time of thermocompression bonding by the pressure bonding rolls 15a and 15b is set to a temperature at which thermocompression bonding is appropriately performed according to the type of the thermosetting resin, but when using an epoxy resin, the temperature of the prepreg Is preferably 40 ° C. or higher.

  The temperature of the prepreg 3 at the time of thermocompression bonding by the pressure-bonding rolls 15a and 15b can be appropriately adjusted depending on the transport time to the pressure-bonding rolls 15a and 15b after the prepreg 3 passes through the dryer 30.

  The resin films 4a and 4b function as a masking material in the step of filling the via holes formed in the prepreg 3 with a conductive paste, and also function as a contamination prevention film during transportation. In the subsequent printed wiring board manufacturing process, the resin films 4a and 4b are peeled off.

  From such a point, the resin films 4a and 4b are required to have a sufficient adhesive strength to the prepreg 3 and a releasability. Moreover, it is desirable that the film does not undergo deformation such as thermal shrinkage when thermocompression bonding with the prepreg 3.

  In this invention, it is preferable to use a polyethylene film, a polypropylene film, a polyester film, etc. from an above-mentioned viewpoint. Further, for example, a film made of the above resin having a thickness of about 10 μm, which is coated on one side with a silicone release agent, can be used.

  After the resin films 4a and 4b are pressure-bonded to both surfaces of the prepreg 3, the resin film laminated prepreg 3 conveyed downstream is cut into a single sheet by a cutting machine 50 in a certain size. As this cutting machine 50, a shearing cutter, a rotary cutter, a laser cutter, etc. can be used.

  As described above, the resin film laminated prepreg is continuously produced. A multilayer printed wiring board using this resin film laminated prepreg is manufactured, for example, as follows. Through holes are formed by laser light irradiation in the thickness direction of the resin film laminated prepreg, and the resin film is used as a masking material to fill the through holes with a conductive paste by screen printing or the like, and then the resin film is peeled and removed. And this prepreg is pinched | interposed between several double-sided printed wiring boards, and the whole is heat-pressed and compression-hardened.

  Alternatively, after removing the resin film, prepare two prepregs each having a metal foil bonded to one side, and the surface of the metal foil of the prepreg is on the outside, and at least two layers of wiring patterns between them The whole circuit board is sandwiched, and the whole is heat-pressed and compression-cured to bond the layers. Thereafter, the metal foil on the surface is patterned into a predetermined shape. Using the double-sided circuit board thus prepared as a core, a multilayer printed wiring board is manufactured by laminating a prepreg filled with a conductive paste and a metal foil and multilayering them as described above. The

  Therefore, an example will be shown below and will be described in more detail. Of course, the invention is not limited by the following examples.

<Example 1>
(1) Preparation of epoxy resin varnish 58 parts by mass of cresol novolac type epoxy resin (trade name “Epicron N690-75M”, Dainippon Ink and Chemicals, Inc., epoxy equivalent 215) as a thermosetting resin, phenol novolac (as a curing agent) Trade name “Phenolite TD-2090-60M” manufactured by Dainippon Ink & Chemicals, Inc. 35.5 parts by mass, 2-ethyl-4-methylimidazole (trade name “2E4MZ” Shikoku Kasei Co., Ltd.) as a curing accelerator 0.06 parts by mass) and 6.44 parts by mass of MEK as a diluent solvent were mixed and stirred and homogenized with a disper or the like. At this time, the amount of the solvent was adjusted so that the solid content (non-solvent component) such as epoxy resin and curing agent was 65.0% by mass to obtain a resin varnish.
(2) Production of prepreg Using the above epoxy resin varnish, a prepreg was produced by the prepreg production apparatus shown in FIG. Using a glass cloth (trade name “3313 / AS891AW” manufactured by Asahi Schavel Co., Ltd.) as a fiber base material, the glass cloth is fed out from an unwinding roll and conveyed to a resin impregnation tank, and the glass cloth is impregnated with the above epoxy resin varnish. . Then, the prepreg was produced by drying and removing the solvent in a varnish by heating at about 130-170 degreeC with a non-contact-type heating unit, and semi-hardening the resin composition. The amount of resin in the prepreg was adjusted to 54 parts by mass of resin with respect to 66 parts by mass of the glass cloth.

Thereafter, the prepreg is continuously pulled out from the dryer, and the polyethylene film fed from a pair of resin film rolls (trade name “Easy Oven Film”, thickness 20 μm, manufactured by J Film Co., Ltd.) is opposed to the front and back surfaces of the prepreg. While maintaining the state in which the prepreg was heated by the residual heat after drying by heating in a dryer, it was brought into close contact under the condition of 5 kg / cm ² by thermocompression bonding. At this time, thermocompression bonding with a polyethylene film was performed at a prepreg temperature of 40 ° C. when reaching the pressure-bonding roll from the dryer.

Thus, after obtaining the prepreg with a film, it cut | disconnected by the fixed dimension with the cutting machine in the downstream, and obtained the prepreg for a test.
(3) Evaluation of test prepreg (3-1) Number of voids The number of voids generated between the surface of the test prepreg cut into 300 mm × 500 mm and the film pressure-bonded thereto was observed, and the test prepreg 10 The average value of the sheets was taken as the number of voids.
(3-2) Moisture content of prepreg A test sample of 5 mm × 50 mm was cut out from the center of the test prepreg, and then this sample was heated to 150 ° C. in a nitrogen stream. Thereafter, a coulometric titration method was performed by introducing the generated volatile gas into the Karl Fischer liquid, and the mass% of water contained in the prepreg was measured.
(3-3) Heat resistance of copper clad laminate A copper clad laminate was produced as follows using a test prepreg. A copper-clad laminate was manufactured by stacking copper foils on both surfaces of the seven prepregs, which were laminated by heating and pressing at 200 ° C. and 30 MPa for 60 minutes. The copper foil used was “GT-18” manufactured by Furukawa Circuit Foil Co., Ltd., having a thickness of 18 μm.

  In this way, a copper-clad laminate having a thickness of 0.78 mm cut to 50 mm × 50 mm was prepared, and heat resistance was measured according to JIS C6481.

The evaluation results of the test prepreg are shown in Table 1.
<Example 2>
A test prepreg was obtained under the same conditions as in Example 1 except that the film material to be thermocompression bonded to both sides of the prepreg was changed to a polyester film (trade name “Tetron”, Teijin DuPont Films Co., Ltd., thickness 25 μm). For this test prepreg, the number of voids, the moisture content of the prepreg, and the heat resistance of the copper clad laminate were evaluated in the same manner as in Example 1. The results are shown in Table 1.
<Example 3>
(1) Preparation of epoxy resin varnish 58 parts by mass of cresol novolac type epoxy resin (trade name “Epicron N690-75M”, Dainippon Ink and Chemicals, Inc., epoxy equivalent 215) as a thermosetting resin, phenol novolac (as a curing agent) Trade name “Phenolite TD-2090-60M” manufactured by Dainippon Ink & Chemicals, Inc. 35.5 parts by mass, 2-ethyl-4-methylimidazole (trade name “2E4MZ” Shikoku Kasei Co., Ltd.) as a curing accelerator 0.06 parts by mass) and 6.44 parts by mass of MEK as a diluent solvent were mixed and stirred and homogenized with a disper or the like. At this time, the amount of the solvent was adjusted so that the solid content (non-solvent component) such as epoxy resin and curing agent was 65.0% by mass to obtain a resin varnish.
(2) Production of prepreg Using the above epoxy resin varnish, a prepreg was produced by the prepreg production apparatus shown in FIG. An aramid fiber nonwoven fabric (trade name “Churmount N718” manufactured by DuPont Teijin Advanced Paper Co., Ltd.) is used as a fiber base material. Impregnated with resin varnish. Then, the prepreg was produced by drying and removing the solvent in a varnish by heating at about 130-170 degreeC with a non-contact-type heating unit, and semi-hardening the resin composition. The amount of resin in the prepreg was adjusted to 53 parts by mass of resin with respect to 47 parts by mass of the aramid nonwoven fabric.

Thereafter, the prepreg is continuously pulled out from the dryer, and the polyethylene film fed from a pair of resin film rolls (trade name “Easy Oven Film”, thickness 20 μm, manufactured by J Film Co., Ltd.) is opposed to the front and back surfaces of the prepreg. While maintaining the state in which the prepreg was heated by the residual heat after drying by heating in a dryer, it was brought into close contact under the condition of 5 kg / cm ² by thermocompression bonding. At this time, thermocompression bonding with a polyethylene film was performed at a prepreg temperature of 40 ° C. when reaching the pressure-bonding roll from the dryer.

Thus, after obtaining the prepreg with a film, it cut | disconnected by the fixed dimension with the cutting machine in the downstream, and obtained the prepreg for a test. For this test prepreg, the number of voids, the moisture content of the prepreg, and the heat resistance of the copper clad laminate were evaluated in the same manner as in Example 1. The results are shown in Table 1.
<Example 4>
A test prepreg was obtained under the same conditions as in Example 3, except that the film material to be thermocompression bonded to both surfaces of the prepreg was changed to a polyester film (trade name “Tetron”, Teijin DuPont Films Co., Ltd., thickness 25 μm). For this test prepreg, the number of voids, the moisture content of the prepreg, and the heat resistance of the copper clad laminate were evaluated in the same manner as in Example 1. The results are shown in Table 1.
<Comparative Example 1>
A prepreg without a resin film was produced under the same conditions as in Example 2 except that the polyester film was not used. And using the prepreg cooled to room temperature, the polyester film used in Example 2 was thermocompression bonded to both surfaces under the conditions of 40 ° C. and 5 kg / cm ² . For this test prepreg, the number of voids, the moisture content of the prepreg, and the heat resistance of the copper clad laminate were evaluated in the same manner as in Example 1. The results are shown in Table 1.
<Comparative example 2>
A prepreg without a resin film was produced under the same conditions as in Example 4 except that the polyester film was not used. And using the prepreg cooled to room temperature, the polyester film used in Example 4 was thermocompression bonded to both surfaces under the conditions of 40 ° C. and 5 kg / cm ² . For this test prepreg, the number of voids, the moisture content of the prepreg, and the heat resistance of the copper clad laminate were evaluated in the same manner as in Example 1. The results are shown in Table 1.

  As shown in Table 1, in Examples 1 to 4 in which the resin film was pressure-bonded to the front and back surfaces of the prepreg that was heated by the residual heat after drying by heating in the dryer, there was a void residue between the prepreg and the resin film. There was almost no. Furthermore, since the front and back surfaces of the prepreg were covered with the resin film immediately after the heat drying in the drier, the moisture absorption of the prepreg was small and the moisture content of the prepreg was reduced. Therefore, the heat resistance of the copper-clad laminate produced from this prepreg was good.

  On the other hand, in Comparative Examples 3 and 4 in which the prepreg once cooled to room temperature was heated again and the resin film was pressure-bonded, a void residue was observed between the prepreg and the resin film. Furthermore, before the prepreg was covered with the resin film, the prepreg absorbed moisture, so that the water content increased. Therefore, the heat resistance of the copper-clad laminate produced from this prepreg was lowered.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Prepreg manufacturing apparatus 2 Fiber base material 3 Prepreg 4a, 4b Resin film 15a, 15b Compression roll 21 Thermosetting resin composition 30 Dryer

FIG. 1 is a diagram schematically showing an embodiment of a prepreg manufacturing apparatus used in a prepreg manufacturing method according to the present invention.

Claims (6)

  A step (A) of impregnating a fiber base material with a thermosetting resin composition, and a prepreg in which the thermosetting resin is made into a semi-cured state by heating and drying the thermosetting resin composition impregnated into the fiber base material A resin film comprising: a step (B) of forming a resin film; and a step (C) in which the resin film is adhered to the front and back surfaces of the prepreg heated by residual heat by heat drying, and these are thermocompression bonded. A method for producing a laminated prepreg.   The method for producing a resin film laminated prepreg according to claim 1, wherein the steps (A) to (C) are carried out as a series of steps by continuously conveying a long fiber substrate downstream. .   In step (C), a long resin film is fed out to the front and back surfaces of the continuously conveyed prepreg heated by the residual heat due to heat drying, and these are passed between the pressure-bonding rolls to pass the front and back surfaces of the prepreg. The method for producing a resin film laminated prepreg according to claim 2, wherein the resin film is closely attached to each other and thermocompression bonded.   After the prepreg is formed in the step (B), the temperature of the prepreg is maintained at 40 ° C. or higher until the resin film is adhered to the front and back surfaces of the prepreg in the step (C), and is heated to 40 ° C. or higher. The method for producing a resin film laminated prepreg according to any one of claims 1 to 3, wherein a resin film is thermocompression bonded to the front and back surfaces of the prepreg.   5. The resin film laminated prepreg according to claim 1, wherein the resin film is used as a masking material when a conductive paste is filled in a through-hole formed in the prepreg by a screen printing method. Production method.   The method for producing a resin film laminated prepreg according to any one of claims 1 to 5, wherein the thermosetting resin is an epoxy resin, and the resin film is a polyethylene film, a polypropylene film, or a polyester film.