JP2005307088A - Prepreg and laminated seat - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prepreg having flexibility not smaller than that of a conventional prepreg and capable of producing a flexible printed wiring board (FPC) having a stiffness higher than conventional stiffness and capable of obtaining high position accuracy of a through hole, etc., in a flex rigid printed circuit board obtained by using the flexible printed wiring board (FPC). <P>SOLUTION: The present invention relates to the prepreg 1 obtained by impregnating an epoxy resin composition composed of an epoxy resin and an elastomer component into a woven fabric 2 or a nonwoven fabric 3 and drying the impregnated fabric. In the prepreg 1, the elastomer component is contained in an amount of 10-50 wt.% based on total amount of cured material 4 of the epoxy resin composition and the elongation rate of the cured material 4 at 20°C is ≥20%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a prepreg and a laminate used as a material for a flexible printed wiring board (FPC).

  In recent years, with the miniaturization and high functionality of electronic devices, high density integration of electronic components is progressing. As a wiring board used in these electronic devices, for example, there are multilayer wiring boards as disclosed in Patent Documents 1 and 2, but recently, expectations for a flex-rigid printed wiring board have been increasing.

  The flex-rigid printed wiring board 6 is a combination of two types of wiring boards, a rigid printed wiring board and a flexible printed wiring board (FPC), and has a structure that combines the features and functions of each wiring board. . That is, as shown in FIG. 2, it comprises a rigid portion 7 having a hardness and strength that can withstand the weight of the mounted component and can be fixed to the housing, and a flexible flex portion 8 that can be bent. A wiring board in which both the rigid portion 7 and the flex portion 8 are integrated is a flex-rigid printed wiring board 6. The fact that both the rigid portion 7 and the flex portion 8 are integrated means that the circuit 9 formed of copper foil or the like is continuously connected to the both, as shown in FIG. The circuit connection between the flex portion 8 and the rigid portion 7 is made by the through hole 10 of the rigid portion 7. In FIG. 2, reference numeral 11 denotes a cover lay, which is a film that is coated to protect the circuit 9 of the flex portion 8.

Currently, a flexible polyimide film 14 is used for the flex portion 8, while a glass epoxy laminate 12 is used for the rigid portion 7.
Japanese Patent Laid-Open No. 10-341083 Japanese Patent Laid-Open No. 10-93245

  In the flex-rigid printed wiring board 6 shown in FIG. 2, generally, when the number of layers of the rigid portion 7 is increased, the defect rate is increased and the reliability of the through hole 10 is decreased. The reason is that the rigid portion 7 is formed by laminating the glass epoxy laminate 12 and the polyimide film 14 as shown in FIG. In other words, the rigid portion 7 is not composed only of the glass epoxy laminated plate 12 including the base material 13 such as glass cloth, and the flex portion 8 made of the polyimide film 14 not including the base material 13 is provided. It is because it is contained inside. As described above, since the base material 13 does not exist in the flex portion 8 inside the rigid portion 7, the flex portion 8 is compared with the glass epoxy laminated plate 12 of the rigid portion 7 in the vertical and horizontal methods (X · The dimensional stability in the Y direction is poor. Here, the X and Y directions mean in-plane directions perpendicular to the stacking direction in FIG.

  The rigid part 7 is usually multi-layered by the build-up method, but increasing the number of conductor layers (number of layers) increases the number of thermal processing processes and increases the processing time. It gets bigger. This is because more heat history is received by a plurality of laminating presses. The dimensional stability in the X and Y directions is an important characteristic for increasing the positional accuracy of the through-holes 10 and the like. However, as the number of layers increases as described above, the positional accuracy deteriorates. There is a possibility that the defect rate in the manufacturing process becomes high.

  In the flex-rigid printed wiring board 6, the flex portion 8 is formed of the polyimide film 14 as described above and does not include the base material 13, so that the rigidity is originally low, but the conductor layer (number of layers) of the rigid portion 7 is not provided. As the number is increased, the flex portion 8 is required to have high rigidity.

  The present invention has been made in view of the above points, and can produce a flexible printed wiring board (FPC) having a flexibility equal to or higher than that of a conventional one and having a rigidity higher than that of a conventional one, An object of the present invention is to provide a prepreg and a laminated board that can obtain a high positional accuracy of a through-hole or the like in a flex-rigid printed wiring board obtained by using this flexible printed wiring board (FPC).

  A prepreg 1 according to claim 1 of the present invention is the prepreg 1 obtained by impregnating a woven fabric 2 or a nonwoven fabric 3 with an epoxy resin composition comprising an epoxy resin and an elastomer component and then drying the woven fabric 2 or nonwoven fabric 3. The elastomer component is contained in an amount of 10 to 50% by weight based on the total amount of the cured product 4, and the elongation rate of the cured product 4 at 20 ° C. is 20% or more.

  The invention of claim 2 is characterized in that, in claim 1, the weight average molecular weight of the elastomer component is 200,000 to 600,000.

  The invention of claim 3 is characterized in that in claim 1 or 2, acrylonitrile butadiene rubber is used as the elastomer component.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, a glass cloth is used as the woven fabric 2.

  The invention of claim 5 is characterized in that in any one of claims 1 to 3, a glass nonwoven fabric or an organic fiber nonwoven fabric is used as the nonwoven fabric 3.

  The invention of claim 6 is characterized in that in any one of claims 1 to 5, the thickness of the woven fabric 2 or the nonwoven fabric 3 is 0.07 mm or less.

  A laminated board 5 according to a seventh aspect of the present invention is characterized by being formed by lamination using the prepreg 1 according to any one of the first to sixth aspects.

  According to the prepreg according to claim 1 of the present invention, a flexible printed wiring board having a flexibility equal to or higher than that of a conventional one can be manufactured while securing rigidity with a woven fabric or a non-woven fabric. In a flex-rigid printed wiring board obtained using a board, it is possible to obtain a high positional accuracy of a through hole or the like.

  According to invention of Claim 2, the flexibility of a prepreg can be improved.

  According to the invention of claim 3, the flexibility of the prepreg can be further enhanced as compared with the case of using other elastomer components.

  According to invention of Claim 4, compared with the case where other woven fabrics are used, the rigidity of a prepreg can be improved further.

  According to the invention of claim 5, the rigidity of the prepreg can be further increased as compared with the case where other nonwoven fabrics are used.

  According to the invention of claim 6, the flexibility of the prepreg can be improved.

  According to the laminated board of claim 7 of the present invention, it is possible to obtain a high degree of positional accuracy such as through-holes while maintaining rigidity with a woven fabric or a non-woven fabric while having a flexibility equal to or higher than the conventional one. A flex-rigid printed wiring board can be manufactured.

  Embodiments of the present invention will be described below.

  The prepreg 1 according to the present invention can be obtained by impregnating a woven fabric 2 or a non-woven fabric 3 with an epoxy resin composition comprising an epoxy resin and an elastomer component and then drying the woven fabric 2 or the nonwoven fabric 3.

  The epoxy resin is not particularly limited. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin, bisphenol F novolak. Type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, dicyclopentadiene type epoxy resin, polyfunctional type epoxy resin (epoxy resin containing three or more epoxy groups in one molecule) and the like can be used. For the purpose of imparting flame retardancy, an epoxy resin containing a halogen compound such as bromine or an epoxy resin containing phosphorus can also be used. Epoxy resins can be used alone or in combination of two or more.

  The elastomer component is not particularly limited. For example, acrylonitrile butadiene rubber (NBR), SBR, BR, IR, EPM, EPDM, CR, butyl rubber, urethane rubber, silicone rubber, polysulfide rubber, hydrogenated nitrile. Rubber, polyether-based special rubber, fluoro rubber, tetrafluoroethylene propylene rubber, acrylic rubber, epichlorohydrin rubber, propylene oxide rubber, ethylene vinyl acetate copolymer, ethylene acrylic rubber, and the like can be used. Among these, it is preferable to use NBR. This is because the flexibility of the prepreg 1 can be further enhanced as compared with the case where other elastomer components are used. The weight average molecular weight of the elastomer component is preferably 200,000 to 600,000. If an elastomer component having a weight average molecular weight of less than 200,000 is used, the flexibility of the cured product 4 of the epoxy resin composition may be reduced, and the flexibility of the prepreg 1 may be reduced. Conversely, the weight average molecular weight may be 600,000. When a larger elastomer component is used, the solubility in a solvent becomes poor and the epoxy resin composition may not be prepared as a varnish. However, when an elastomer component having a weight average molecular weight of 200,000 to 600,000 is used, the above-described problem does not occur and the flexibility of the prepreg 1 can be improved.

  A curing agent can be used when preparing the epoxy resin composition. Although it does not specifically limit as a hardening | curing agent, For example, a dicyandiamide and a phenol novolak can be used. The compounding quantity of a hardening | curing agent can be set suitably.

  A curing accelerator can also be used when preparing the epoxy resin composition. Although it does not specifically limit as a hardening accelerator, For example, imidazoles, such as 2-ethyl-4-methylimidazole (2E4MZ), dimethylbenzylamine, etc. can be used. The compounding quantity of a hardening accelerator can also be set suitably.

  At the time of preparing the epoxy resin composition, an additive (filler) that functions as a flame retardant aid, a thickener, or the like can also be used. The additive is not particularly limited. For example, an inorganic filler such as silica powder, metal hydrate powder such as aluminum hydroxide and magnesium hydroxide, and clay mineral powder such as talc and clay is used. be able to. Only 1 type can be used for an additive, and 2 or more types can also be mixed and used for it. The blending amount of the additive can also be set as appropriate.

  Then, in addition to the epoxy resin and the elastomer component, if necessary, a curing agent, a curing accelerator and an additive are added to the solvent, and this is uniformly mixed with a mixer, a blender, etc., so that the epoxy resin composition is used as a varnish. Can be prepared. The solvent is not particularly limited, and for example, dimethylacetamide (DMAC), dimethylformamide (DMF), methyl ethyl ketone (MEK), methoxypropanol (MP) and the like can be used. Only 1 type can be used for a solvent, and 2 or more types can also be mixed and used for it.

  Here, the compounding amount of the elastomer component is set in advance so that the elastomer component is finally contained in an amount of 10 to 50% by weight based on the total amount of the cured product 4 (solid material) of the epoxy resin composition. To prepare. If the content of the elastomer component is less than 10% by weight, the flexibility of the cured product 4 of the epoxy resin composition may be reduced, and the flexibility of the prepreg 1 may be reduced. Conversely, the content of the elastomer component is 50 If the amount is more than% by weight, the heat resistance of the finally obtained laminate 5 is lowered, the glass transition temperature is lowered, or the amount of resin smear is increased. May not be able to be secured. Further, the elongation percentage at 20 ° C. of the cured product 4 needs to be 20% or more. If the elongation is less than 20%, the flexibility of the prepreg 1 is lowered. Note that the upper limit of the elongation is 300%, and if this upper limit is exceeded, the rigidity and dimensional stability, etc., of the printed wiring board will decrease.

  And the woven fabric 2 or the nonwoven fabric 3 is impregnated with the epoxy resin composition prepared as a varnish as mentioned above. At this time, the resin content can be set to 40 to 80% by weight with respect to the total amount of the prepreg 1. Then, for example, the prepreg 1 according to the present invention can be obtained by heating and drying at a temperature of 80 to 200 ° C. for 10 seconds to 2 hours to remove the solvent and to make a semi-cured B stage state.

  A conventional flexible printed circuit board (FPC) is manufactured by forming a conductor layer on the surface of a flexible and insulating polyimide film 14 by a printing technique. When used in place of the polyimide film 14, the woven fabric 2 or the nonwoven fabric 3 can ensure rigidity, and the prepreg 1 is formed even when the woven fabric 2 or the nonwoven fabric 3 is used. The elastomer component is contained in an amount of 10 to 50% by weight based on the total amount of the cured product 4 of the epoxy resin composition, and the elongation rate at 20 ° C. of the cured product 4 is 20% or more. A flexible printed wiring board (FPC) having flexibility can be manufactured.

  Here, it is preferable to use a glass cloth as the woven fabric 2. Since the glass cloth has higher rigidity than the other woven fabrics 2, the rigidity of the prepreg 1 can be further increased. On the other hand, as the nonwoven fabric 3, it is preferable to use a glass nonwoven fabric (glass paper) or an organic fiber nonwoven fabric. Since the glass nonwoven fabric and the organic fiber nonwoven fabric have higher rigidity than the other nonwoven fabrics 3, the rigidity of the prepreg 1 can be further increased. In addition, although it does not specifically limit as an organic fiber which forms an organic fiber nonwoven fabric, For example, an aramid fiber, a polyester fiber, a polyimide fiber, a polyacryl fiber, etc. can be used. Moreover, it is preferable that the thickness of a woven fabric or a nonwoven fabric is 0.07 mm or less. When the thickness of the woven fabric 2 or the nonwoven fabric 3 is thicker than 0.07 mm, the flexibility of the prepreg 1 may be lowered. However, when the thickness of the woven fabric 2 or the nonwoven fabric 3 is 0.07 mm or less as described above, the flexibility of the prepreg 1 can be improved. In addition, in order to ensure the rigidity of the prepreg 1, it is preferable that the minimum of the thickness of the woven fabric 2 or the nonwoven fabric 3 is 0.01 mm.

  The laminate 5 according to the present invention can be manufactured by laminate molding using the prepreg 1 obtained as described above. FIG. 1 shows an example of a laminated board 5 according to the present invention. The laminated board 5 is a flex-rigid printed wiring board 6 obtained by using the prepreg 1 for the flex part 8 instead of the conventional polyimide film 14. A glass epoxy laminate 12 can be used for the rigid portion 7.

  In the flex-rigid printed wiring board 6 shown in FIG. 1, even if the number of layers of the rigid portion 7 is increased, the defect rate does not increase and the reliability of the through hole 10 does not decrease. The reason is that, as shown in FIG. 1, the rigid portion 7 is composed only of a material including a base material 13 such as a glass cloth such as a glass epoxy laminated plate 12. That is, the flex portion 8 inside the rigid portion 7 also includes the woven fabric 2 or the non-woven fabric 3 as the base material 13. Therefore, the rigid portion 7 is excellent in dimensional stability in the vertical and horizontal methods (X and Y directions) against heat.

  The rigid portion 7 can be multi-layered by a normal build-up method, but the positional accuracy can be maintained high even when multi-layered in this way, and accordingly, the defect rate in the printed wiring board manufacturing process. Can be kept low.

  Further, in the flex-rigid printed wiring board 6 shown in FIG. 1, the flex portion 8 is formed of the prepreg 1 according to the present invention as described above and includes the woven fabric 2 or the non-woven fabric 3 and thus has high rigidity. Therefore, even if the conductor layer (number of layers) of the rigid portion 7 is increased, the high rigidity required for the flex portion 8 can be sufficiently ensured.

  As described above, in the flex-rigid printed wiring board 6 obtained by using the prepreg 1 according to the present invention in the form of a flexible printed wiring board (FPC), the rigidity of the flex portion 8 is secured by the woven fabric 2 or the nonwoven fabric 3. On the other hand, it has a bendability comparable to or higher than that of the conventional one, and the position accuracy of the through hole 10 and the like can be obtained with high accuracy.

  Hereinafter, the present invention will be specifically described by way of examples.

<Preparation of varnish of epoxy resin composition>
“YDB-500” (epoxy equivalent: 500, bromination rate: about 24% by weight) manufactured by Toto Kasei Co., Ltd., which is a brominated bisphenol A type epoxy resin, and Dainippon Ink, which is a cresol novolac type epoxy resin. “N-690” (epoxy equivalent: 220) manufactured by Chemical Industry Co., Ltd. was used.

  In addition, as an elastomer component, “BRR-1H” (weight average molecular weight = 330,000) manufactured by JSR Co., Ltd., which is NBR, “CTBN 1300 × 13” (UBE Industries, Ltd.) (weight average molecular weight = 5000), which is NBR. Was used.

  Furthermore, dicyandiamide (molecular weight: 84, theoretically active hydrogen equivalent: 21) is used as the curing agent, 2-ethyl-4-methylimidazole (2E4MZ) is used as the curing accelerator, and methyl ethyl ketone (MEK), methoxy is used as the solvent. Propanol (MP) and dimethylformamide (DMF) were used.

  First, the elastomer component was uniformly dissolved in dimethylformamide (DMF) so as to be about 15% by weight. Next, a predetermined solvent (MEK: MP: DMF (weight ratio) = 1: 1.5: 3) of this solution and other components (excluding the curing accelerator) in the blending amounts shown in [Table 1] below. The mixture was stirred and mixed at about 1000 rpm for about 90 minutes by “Homomixer” manufactured by Tokushu Kika Kogyo Co., Ltd. Then, an epoxy resin composition having a viscosity at 25 ° C. of about 500 to 1000 centipoise is obtained by adding a curing accelerator (2-ethyl-4-methylimidazole) thereto, stirring again for about 15 minutes, and then degassing. A varnish was prepared.

<Manufacture of prepreg using woven fabric>
Glass cloth (1035 type: “WEA1035” manufactured by Nittobo Co., Ltd., thickness: 0.03 mm) and glass cloth (2116 type: “WEA-116E” manufactured by Nittobo Co., Ltd.), thickness: 0 0.1 mm) was used.

  And the varnish prepared as mentioned above was impregnated so that resin content might be 40 to 80 weight% with respect to the total amount of prepreg. Thereafter, this was heated by a non-contact type heating unit at a temperature of about 130 to 180 ° C. for 5 minutes to dry and remove the solvent in the varnish and to make a semi-cured B stage state, thereby producing a prepreg.

<Manufacture of prepreg using non-woven fabric>
As the non-woven fabric, an aramid fiber non-woven fabric (“Surmount” manufactured by DuPont, 30 g basis weight = thickness: 0.04 mm) was used.

  And the varnish prepared as mentioned above was impregnated so that resin content might be 40 to 80 weight% with respect to the total amount of prepreg. Thereafter, this was heated by a non-contact type heating unit at a temperature of about 130 to 180 ° C. for 5 minutes to dry and remove the solvent in the varnish and to make a semi-cured B stage state, thereby producing a prepreg.

<Manufacture of laminates>
Rolled copper foil (“BHY13BT” manufactured by Nikko Materials Co., Ltd., thickness: 18 μm) was superimposed on both sides of the prepreg produced as described above, and 2.94 MPa while being heated at 170 ° C. for 90 minutes. A laminated board (double-sided copper-clad laminated board) was manufactured by pressurizing with the pressure of and laminating.

<Elongation rate of cured product of epoxy resin composition>
The varnish prepared as described above was applied to a PET film with a comma coater at room temperature. Next, this is heated by a non-contact type heating unit at a temperature of about 130 to 170 ° C., and the solvent in the varnish is dried and removed, and a semi-cured B stage state is obtained. : 100 μm). Thereafter, the insulating film was cured by leaving it in an atmosphere of 170 ° C. for 2 hours.

  And the hardened insulating film was peeled from PET film, and this insulating film was used as a sample for calculating elongation. The elongation at 20 ° C. of this sample was calculated based on ASTM D638. As a result, those having an elongation of less than 20% were used as comparative examples, while those having an elongation of 20% or more and satisfying other constituent requirements were used as examples.

<Flexibility test (MIT test)>
An MIT test (curvature radius: φ0.38 cm, load: 0.5 kgf (4.9 N)) was performed using the laminate produced as described above. This test was performed in an environment of a temperature of 20 ° C. and a humidity of 50% based on JIS C 6471. The number of times until the sample laminate is broken is shown in Table 1 below as measurement results.

<Coefficient of thermal expansion in X and Y directions>
The thermal expansion coefficient of the prepreg produced as described above in the X and Y directions (in the direction perpendicular to the thickness direction) was measured by the TMA method. The measurement results are shown in [Table 1] below.

<Bending elastic modulus>
First, the prepreg produced as described above is overlaid with a copper foil (thickness: 18 μm) on both sides so that the thickness after lamination molding is about 1.6 mm, at a temperature of 170 ° C. A double-sided copper-clad laminate was manufactured by heating and pressing at a pressure of 2.94 MPa for 90 minutes to laminate. Next, the copper foil of this double-sided copper-clad laminate was removed by etching the entire surface to prepare a sample for measuring the flexural modulus.

  And the bending elastic modulus was measured based on JIS C 6481 using the said sample. The measurement results are shown in [Table 1] below.

  In addition, "Espanex" manufactured by Nippon Steel Chemical Co., Ltd. (film thickness: 0.05 mm, copper foil thickness: 18 μm) is used as a polyimide-based flexible printed wiring board (FPC) that does not include a base material. This was designated as Comparative Example 1.

  As seen in Table 1, when Examples 1 to 4 and Comparative Example 1 are compared, it is confirmed from the results of the MIT test that both are excellent in flexibility (fold resistance). However, from the measurement results of the flexural modulus and the thermal expansion coefficient in the X and Y directions, Examples 1-4 are superior in terms of rigidity and positional accuracy compared to Comparative Example 1 that does not include a base material. It is confirmed.

  Moreover, when Examples 1-4 and Comparative Examples 2-4 are contrasted, both are excellent in the point of rigidity and a positional accuracy from the measurement result of a bending elastic modulus and the thermal expansion coefficient of a X * Y direction. Is confirmed. However, from the results of the MIT test, Examples 1-4 are more flexible (folding resistance) than Comparative Examples 2-4 in which the content of the elastomer component and the elongation percentage of the cured product are out of the predetermined range. It is confirmed that it is excellent.

  Further, when Examples 1 and 2 and Example 4 are compared, it is confirmed from the measurement results of the flexural modulus and the thermal expansion coefficient in the X and Y directions that both are excellent in terms of rigidity and positional accuracy. Is done. However, from the results of the MIT test, Examples 1 and 2 are more excellent in flexibility (fold resistance) than Example 4 in which the thickness of the woven fabric exceeds 0.07 mm. Is confirmed.

It is sectional drawing which shows an example of embodiment of this invention. It is sectional drawing which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Prepreg 2 Woven cloth 3 Nonwoven fabric 4 Hardened material 5 Laminate board

Claims (7)

  In a prepreg obtained by impregnating a woven fabric or non-woven fabric with an epoxy resin composition comprising an epoxy resin and an elastomer component and then drying the woven fabric or non-woven fabric, the elastomer component is 10 to 50 weights based on the total amount of the cured product of the epoxy resin composition. %, And the elongation at 20 ° C. of the cured product is 20% or more.   The prepreg according to claim 1, wherein the elastomer component has a weight average molecular weight of 200,000 to 600,000.   The prepreg according to claim 1 or 2, wherein acrylonitrile butadiene rubber is used as an elastomer component.   The prepreg according to any one of claims 1 to 3, wherein a glass cloth is used as the woven fabric.   The prepreg according to any one of claims 1 to 3, wherein a glass nonwoven fabric or an organic fiber nonwoven fabric is used as the nonwoven fabric.   The prepreg according to any one of claims 1 to 5, wherein the woven fabric or the nonwoven fabric has a thickness of 0.07 mm or less.   A laminate obtained by laminate molding using the prepreg according to any one of claims 1 to 6.

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