JP2005340270A - Laminated plate, pre-preg therefor, flexible printed wiring board using the same and flex rigid printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a flexible printed wiring board (FPC) superior in flexibility and rigidity, and to provide a pre-preg for laminated plate where high position precision of a through hole can be obtained, in a flex rigid printed wiring board obtained by using the flexible printed wiring board (FPC). <P>SOLUTION: The pre-preg for laminated plate is obtained by impregnating a fabric or a non-woven fabric with an epoxy resin composition formed of epoxy resin and elastomer and drying it. Bridged elastomer with a particle size of 1.0 μm or less is used for elastomer. 10 to 50 wt.% of bridged elastomer is made to contain with respect to whole quantity of a hardened material of the epoxy resin composition. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a prepreg for a laminated board used as a material for a flexible printed wiring board (FPC), particularly a flex-rigid printed wiring board, and the laminated board.

  As the flexible printed wiring board, a metal foil such as a copper foil is pasted on a polyimide resin or polyester resin having a thickness of 25 to 125 μm and a predetermined circuit shape is formed thereon. A flexible wiring board using this kind of resin is widely used as a wiring in a bent portion or a movable portion because of its flexibility. In addition, a rigid wiring board obtained by circuit forming a laminated board obtained by stacking a plurality of prepregs impregnated with resin on a base material and press-molding is also used as an electric / electronic component.

  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.

  A flex-rigid printed wiring board 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 207 that has the strength and strength to withstand the weight of the mounted component and can be fixed to the housing, and a flexible flex portion 208 that can be bent. A wiring board in which both the rigid portion 7 and the flex portion 208 are integrated is a flex-rigid printed wiring board 206. The fact that both the rigid portion 207 and the flex portion 208 are integrated means that a circuit 209 formed of copper foil or the like is continuously connected to the both, and usually, as shown in FIG. The connection between the flex portion 208 and the circuit 209 of the rigid portion 207 is made by the through hole 210 of the rigid portion 7. In FIG. 2, reference numeral 211 denotes a coverlay, which is a film that is coated to protect the circuit 209 of the flex portion 208.

Currently, a flexible polyimide film 204 is used for the flex portion 208, while a glass epoxy laminate 212 is used for the rigid portion 207.
Japanese Patent Laid-Open No. 10-341083 Japanese Patent Laid-Open No. 10-93245

  However, since polyimide resin is expensive, cost reduction of flexible wiring board itself is desired. In the flex-rigid printed wiring board 206 shown in FIG. 2, generally, when the number of rigid portions 207 is increased, the defect rate increases and the reliability of the through-hole 210 decreases. The reason is that, as shown in FIG. 2, the rigid portion 207 is not composed only of the glass epoxy laminated plate 212 including the base material 213 such as a glass cloth. This is because the flex portion 208 made of the polyimide film 204 not included is included inside. Thus, since the base material 213 does not exist in the flex portion 208 inside the rigid portion 7, the flex portion 208 has a vertical / horizontal method (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 207 is usually multi-layered by the build-up method. However, 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 210 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.

  Further, in the flex-rigid printed wiring board 206, the flex portion 208 is formed of the polyimide film 204 as described above and does not include the base material 213, so the rigidity is originally low, but the conductor layer (number of layers) of the rigid portion 207 is not provided. As the number is increased, the flex portion 208 is required to have high rigidity.

  The present invention has been made in view of the above points, and can produce an inexpensive flexible printed wiring board (FPC) having flexibility comparable to that of the prior art and having rigidity higher than that of the prior art. In particular, it is an object of the present invention to provide a prepreg for a laminated board that can obtain high positional accuracy of a through hole or the like in a flex-rigid printed wiring board using this flexible printed wiring board (FPC).

  The invention according to claim 1 of the present invention is a laminate prepreg obtained by impregnating a woven or non-woven fabric with an epoxy resin composition comprising an epoxy resin and an elastomer, and drying the woven fabric or non-woven fabric. It is a crosslinked elastomer having a diameter of 1.0 μm or less, and is a prepreg for a laminated board containing 10 to 50% by weight of the crosslinked elastomer with respect to the total amount of the cured product of the epoxy resin composition.

  Moreover, the invention which concerns on Claim 2 of this invention makes it a preferable aspect to use a glass cloth as said woven fabric in the prepreg for laminated boards of Claim 1.

  Moreover, the invention which concerns on Claim 3 of this invention makes it a preferable aspect to use a glass nonwoven fabric or organic fiber as said nonwoven fabric in the prepreg for laminated sheets of Claim 1.

  Furthermore, the invention according to claim 4 of the present invention uses the prepreg for laminated sheets according to claims 1 to 3 having a thickness of 0.07 mm or less as the thickness of the woven fabric or nonwoven fabric.

  The invention according to claim 5 of the present invention is a laminated plate formed by laminating the prepreg for laminated plates according to claims 1 to 4.

  The invention according to claim 6 of the present invention is a flexible printed wiring board using the laminate of claim 5.

  The invention according to claim 7 is a flex-rigid printed wiring board obtained by connecting rigid wiring boards using the flexible printed wiring board according to claim 6.

  According to the prepreg for a laminated board according to the present invention, an inexpensive flexible printed wiring board having the same degree of flexibility as that of the 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 by using a board, the positional accuracy of through-holes and the like can be increased.

  Further, by using glass cloth as the woven fabric and glass nonwoven fabric or organic fiber as the nonwoven fabric, the rigidity can be further increased as compared with the case of using other woven fabric or nonwoven fabric.

  Furthermore, by using a woven or non-woven fabric having a thickness of 0.07 mm or less, the flexibility of the laminated board can be enhanced.

  Embodiments of the present invention will be described below.

  The laminate prepreg according to the present invention can be obtained by impregnating a woven fabric or a non-woven fabric with an epoxy resin composition comprising an epoxy resin and a crosslinked elastomer having a particle size of 1.0 μm or less, and then drying it.

  The epoxy resin of the present invention 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, Use bisphenol F novolac type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, dicyclopentadiene type epoxy resin, polyfunctional type epoxy resin (epoxy resin containing 3 or more epoxy groups in one molecule), etc. Can do. 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 present invention can be combined with an epoxy resin as described above together with a crosslinked elastomer having a particle size of 1.0 μm or less, which is a specific elastomer, to provide a laminate having excellent flexibility while maintaining high rigidity. The present inventors have found that a highly accurate flex-rigid printed wiring board can be provided. In particular, since the present invention can use a resin similar to the resin that can be used on the rigid wiring board side, it is considered that the deformation against heat is also approximated. When you do it, you can have good results.

  Here, the crosslinked elastomer of the present invention is, for example, a secondary crosslinked material having a functional group such as a carboxyl group or a glycidyl group distributed on the surface of a conventional acrylonitrile-butadiene copolymer or the like. Then, it is pulverized. By using such a cross-linked elastomer, it is excellent in compatibility with the epoxy resin, the cross-linked elastomer does not harden in a part of the resin composition, and is a solvent for producing a prepreg by impregnating the resin with the base material. Is also ensured, and a uniform resin composition can be obtained.

  Although it does not specifically limit as a crosslinked elastomer of this invention, What has chemical compositions, such as SBR, BR, and a butyl rubber, is used, and an acrylonitrile butadiene elastomer and a methacrylic acid butadiene elastomer are especially preferable.

  Further, it has been found that, among the above-mentioned crosslinked elastomers, when a crosslinked elastomer having a particle size of 1.0 μm or less is used, sufficient flexibility can be imparted when the laminate is used. The particle size of the crosslinked elastomer is not particularly limited as long as it is 1.0 μm or less, but is preferably 0.02 μm or more, more preferably 0.02 μm or more and 0.5 μm or less in consideration of production. Preferably they are 0.02 micrometer or more and 0.1 micrometer or less. In addition, the particle size of the present invention is measured by dynamic light scattering particle size analysis (equipment used: LPA-3100 manufactured by Otsuka Electronics).

  The reason why excellent flexibility can be obtained while maintaining rigidity by using such a cross-linked elastomer is not clear, but the specific surface area of the cross-linked elastomer is increased by using a finely cross-linked elastomer in combination. It is considered that the correlation between the crosslinked elastomer present in a dispersed state in the composition and the epoxy resin is improved, and that the high dispersibility of the crosslinked elastomer contributes to flexibility. Furthermore, it has an advantage that the above properties can be expressed with a small addition amount due to the property of being fine particles.

  Accordingly, the glass transition temperature (Tg) is lowered due to the nature of the combined use of ordinary elastomer components, but the Tg is not lowered and high flexibility can be obtained in the crosslinked elastomer of the present invention.

  As such a crosslinked elastomer, for example, XER-91 (acrylonitrile-butadiene elastomer, particle size: 0.1 μm) manufactured by JSR Corporation, XER-92 (methacrylic acid-butadiene elastomer, particle diameter manufactured by JSR Corporation), particle diameter : 0.1 μm).

  As another composition of the prepreg for laminates of the present invention, a curing agent is added together with the above resin composition for semi-curing. 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.

  In addition, a curing accelerator can be used when preparing the 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.

  Moreover, the additive (filler) which plays the role of a flame retardant adjuvant, a thickener, etc. can also be used as needed. 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.

  In consideration of other characteristics, it is also possible to add a resin component usually used in a prepreg.

  Then, in addition to the epoxy resin and the crosslinked elastomer, a curing agent, a curing accelerator and an additive are added to a solvent, and this is uniformly mixed with a mixer, a blender, or the like to prepare an epoxy resin composition as a varnish. it can.

  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 crosslinked elastomer is finally contained in an amount of 10 to 50% by weight, preferably 15 to 45% by weight, more preferably 20 to 40% by weight based on the total amount of the cured product (solid material) of the resin composition. In addition, the amount of the crosslinked elastomer is set in advance to prepare a resin composition.

  If the content of the cross-linked elastomer is less than 10% by weight, the flexibility of the cured product may be reduced and the flexibility of the prepreg may be reduced. Conversely, the content of the elastomer component is more than 50% by weight. When the heat resistance of the finally obtained laminate is lowered, the glass transition temperature is lowered, or the amount of smear is increased, the performance required for the laminate cannot be secured. There is a fear.

  Then, the woven fabric or the nonwoven fabric is impregnated with the epoxy resin composition prepared as a varnish as described above. At this time, the resin content can be set to 40 to 80% by weight based on the total amount of the prepreg. Then, for example, the prepreg 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 / insulating polyimide film by a printing technique, and the prepreg according to the present invention is used as a conventional polyimide film. When used in place of the above, rigidity can be ensured by a woven fabric or a non-woven fabric, and even if a woven fabric or non-woven fabric is used in this way, the total amount of the cured product of the epoxy resin composition that forms the prepreg On the other hand, a flexible printed wiring board (FPC) having the same degree of flexibility as the conventional one can be produced by containing 10 to 50% by weight of the predetermined cross-linked elastomer.

  Here, it is preferable to use glass cloth as the woven fabric. Since the glass cloth has higher rigidity than other woven fabrics, the rigidity of the prepreg can be further increased.

  On the other hand, it is preferable to use a glass nonwoven fabric (glass paper) or an organic fiber as the nonwoven fabric. Since glass nonwoven fabric and organic fiber have higher rigidity than other nonwoven fabrics, the rigidity of the prepreg can be further increased. In addition, although it does not specifically limit as an organic fiber, 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. If the thickness of the woven or non-woven fabric is greater than 0.07 mm, the flexibility of the prepreg may be reduced. However, when the thickness of the woven or non-woven fabric is 0.07 mm or less as described above, the flexibility of the prepreg can be further enhanced. In addition, in order to ensure the rigidity of a prepreg, it is preferable that the minimum of the thickness of a woven fabric or a nonwoven fabric is 0.01 mm.

  The laminate according to the present invention can be produced by using the prepreg obtained as described above, placing a metal foil, for example, copper, aluminum, etc. on the prepreg and press-molding it.

  FIG. 1 shows an example in which the present invention is applied to a flex-rigid printed wiring board. This laminated board 5 with an inner layer circuit is a flex-rigid printed wiring board 6 obtained by using the above prepreg 1 for the flex part 8 instead of the conventional polyimide film. 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, both the inside of the rigid portion 7 and the flex portion 8 include the woven fabric 2 or the nonwoven 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. In FIG. 1, reference numeral 11 denotes a coverlay, which is a film that is coated to protect the circuit 9 of the flex portion 8.

  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 the same degree of flexibility as the conventional one, and the position accuracy of the through hole 10 and the like can be obtained with high accuracy.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these 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, “XER-91” (acrylonitrile butadiene elastomer, particle size: 0.1 μm) manufactured by JSR Co., which is a crosslinked elastomer, and “N220SH” (nitrile rubber, manufactured by JSR Co., Ltd.) as a non-crosslinked elastomer. Linear) 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, each elastomer component is uniformly dispersed in MEK so as to be about 15% by weight, and then this dispersion and other components (excluding the curing accelerator) are mixed in a predetermined amount shown in Table 1 below. The solvent (MEK: MP: DMF = 1: 1.5: 3) was added, and this was stirred and mixed at about 1000 rpm for about 90 minutes by “Homomixer” manufactured by Tokushu Kika Kogyo Co., Ltd. Thereafter, 0.1 part by weight of a curing accelerator (2-ethyl-4-methylimidazole) is added to this, and the mixture is stirred again for about 15 minutes, and then degassed, so that the B-type viscosity at 25 ° C. is about 500- A 1000 centipoise epoxy resin varnish was prepared.

<Manufacture of prepreg using woven fabric>
As the woven fabric, a glass cloth (1035 type: “WEA1035” manufactured by Nitto Boseki Co., Ltd., thickness: 0.03 mm) was used.

  And each varnish prepared as mentioned above was impregnated so that the resin content might become predetermined weight% shown in Table 1 to prepreg whole quantity. Then, this was heated for 5 minutes at 160 degreeC with the non-contact-type heating unit, and the solvent in a varnish was dried and removed, and it was set as the semi-hardened B stage state, and the prepreg was manufactured.

<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.

  Then, the varnish prepared as described above was impregnated so that the resin content was a predetermined weight% shown in Table 1 with respect to the total amount of the 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.

  About each laminated board produced as mentioned above, the following bendability tests, thermal expansibility tests, bending elastic moduli, and Tg were measured. The results are shown in Table 1. In Table 1, each composition amount means parts by weight.

<Flexibility test (MIT test)>
An MIT test (curvature radius: φ0.38 mm, 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 laminate as a sample was disconnected was measured.

<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.

<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 JISC6481 using the said sample.

<Glass transition temperature (Tg)>
The plate for bending elastic modulus was cut into a length of 30 mm and a width of 5 mm, tan δ was measured with a viscoelastic spectrometer device, and the peak temperature was defined as Tg.

  In Table 1, Comparative Example 1 shows “Espanex” (film thickness: 0.05 mm, manufactured by Nippon Steel Chemical Co., Ltd.) used as a polyimide-based flexible printed wiring board (FPC) that does not include a base material. (Measured using a thickness of copper foil: 18 μm).

  As can be seen in Table 1, since Examples 1 to 3 are structures having a base material compared to the resinous material used in the conventional flexible wiring board of Comparative Example 1, high rigidity and excellent thermal stability It turns out that it has sex. Moreover, although the flexibility is slightly inferior to the resin property, it can be seen that the flexibility is improved to a level that does not cause any practical problems.

  Further, when Examples 1 to 3 and Comparative Examples 2 to 5 are compared, both of them are excellent in rigidity and positional accuracy from the measurement results of the flexural modulus and the thermal expansion coefficient in the X and Y directions. It is confirmed. However, from the results of the MIT test, it is confirmed that Examples 1 to 3 are superior in flexibility compared to Comparative Examples 2 to 5 having different elastomer contents and types.

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 with inner layer circuit

Claims (7)

  An epoxy resin, a prepreg for a laminate obtained by impregnating a woven or non-woven fabric with an epoxy resin composition comprising an elastomer, and drying the laminate, wherein the elastomer is a crosslinked elastomer having a particle size of 1.0 μm or less, A prepreg for a laminate comprising 10 to 50% by weight of the crosslinked elastomer based on the total amount of the cured product of the epoxy resin composition.   The prepreg for a laminated board according to claim 1, wherein a glass cloth is used as the woven fabric.   The prepreg for a laminate according to claim 1, wherein the nonwoven fabric is made of glass nonwoven fabric or organic fiber.   The prepreg for a laminated board according to any one of claims 1 to 3, wherein the thickness of the woven fabric or the nonwoven fabric is 0.07 mm or less.   A laminate comprising the prepreg for laminate according to any one of claims 1 to 4.   The flexible printed wiring board using the laminated board of Claim 5.   The flexible printed wiring board according to claim 6, wherein the rigid wiring boards are connected to each other.

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