JP2010129610A - Flex-rigid printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flex-rigid printed wiring board capable of having improved thickness accuracy, and being easily bendable at flex portions. <P>SOLUTION: A plurality of rigid portions 1 are integrated with each other through the flex portions 2 to form this flex-rigid printed wiring board A. The epoxy resin layer 5 of a resin sheet 6 with metal foil which is formed by laminating the metal foil 3, a polyimide film 4, and the epoxy resin layer 5 in this order is superposed on a flexible board 7, and the resin sheet 6 with the metal foil is bonded to the flexible board 7. The metal foil 3 in a prescribed area is removed in a prescribed pattern shape to form a conductor circuit 8, and the rigid portions 1 are formed by laminating rigid boards 9 in this area. The metal foil 3 in the area other than the prescribed area is removed to form the flex portion 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a flex-rigid printed wiring board used by being bent in a small electronic device or the like.

  The flex-rigid printed wiring board is formed by integrating a plurality of rigid parts via a flex part (see, for example, Patent Document 1). Here, the rigid part is a rigid printed wiring board part that can withstand the weight of the component to be mounted and can be fixed to the housing, and the flex part is flexible enough to be bent. It is a flexible printed wiring board part. The flex-rigid printed wiring board is used in a small and light device such as a portable electronic device by being bent at a flex portion and housed in a housing or the like.

However, in recent years, further improvements in plate thickness accuracy and flexibility have been demanded for such flex-rigid printed wiring boards. In particular, when the plate thickness accuracy is poor, insulation between layers may be deteriorated or the target plate thickness design value may not be met.
Japanese Examined Patent Publication No. 61-48279

  The present invention has been made in view of the above points, and it is an object of the present invention to provide a flex-rigid printed wiring board that can improve plate thickness accuracy and can be easily bent at a flex portion. is there.

  A flex-rigid printed wiring board according to claim 1 of the present invention is a flex-rigid printed wiring board A in which a plurality of rigid portions 1 are integrated through a flex portion 2, and a metal foil 3, a polyimide film 4, The epoxy resin layer 5 of the resin sheet 6 with metal foil formed by laminating the epoxy resin layer 5 in this order is stacked on the flexible substrate 7, and the resin sheet 6 with metal foil is adhered to the flexible substrate 7. 3 is removed in a predetermined pattern shape to form a conductor circuit 8, and a rigid substrate 9 is laminated in this region to form a rigid portion 1, and the metal foil 3 other than the region is removed. A flex portion 2 is formed.

  According to the flex-rigid printed wiring board according to claim 1 of the present invention, the insulating layer formed on the flexible substrate is composed of two layers of a polyimide film that does not melt and flow at a normal molding temperature and an epoxy resin layer. As a result, it is possible to improve the plate thickness accuracy and easily bend at the flex portion as compared with the case consisting only of the epoxy resin layer.

  Embodiments of the present invention will be described below.

  FIG. 1 shows an example of an embodiment of the present invention. In the present invention, the flex-rigid printed wiring board A is formed by integrating a plurality of rigid portions 1 via the flex portions 2 and can be manufactured as follows.

  First, the flexible substrate 7 to be a core material is produced. As shown in FIG. 1A, the flexible substrate 7 is a conductor circuit having a thickness of about 6 to 18 μm formed of copper or the like on the surface of a base material 10 having a thickness of about 10 to 100 μm formed of polyimide resin or the like. 8 can be produced.

On the other hand, the resin sheet 6 with metal foil is produced. As shown in FIG. 1A, the metal foil-attached resin sheet 6 is formed by laminating a metal foil 3, a polyimide film 4, and an epoxy resin layer 5 in this order. 3 and the polyimide film 4 are bonded by thermocompression bonding, for example, at 350 ° C. for 5 minutes under the condition of 2.94 MPa (30 kg / cm ² ), and then the epoxy resin composition is applied to the surface of the polyimide film 4 This can be produced by heating and drying until it is in a semi-cured state (B stage state) to form the epoxy resin layer 5. In addition, the thickness of the metal foil 3 is about 6-18 micrometers, the thickness of the polyimide film 4 is about 10-50 micrometers, and the thickness of the epoxy resin layer 5 is about 10-50 micrometers.

  Here, the epoxy resin composition used for the production of the resin sheet 6 with metal foil is an epoxy resin such as brominated bisphenol A type epoxy resin or cresol novolac type epoxy resin, a curing agent such as dicyandiamide, 2-ethyl-4- It can be prepared by blending a curing catalyst such as methylimidazole. Although the compounding quantity of each component is not specifically limited, It is preferable that an epoxy resin is 90-100 mass parts, a hardening | curing agent is 0.5-10 mass parts, and a curing catalyst is 0.01-1 mass part. .

  Next, as shown in FIGS. 1 (a) and 1 (b), the epoxy resin layer 5 of the resin sheet 6 with metal foil is overlapped on the flexible substrate 7 and heated and pressed to form the resin sheet 6 with metal foil. Adhere to the substrate 7. The molding pressure at this time is 1 to 3 MPa. The molding temperature is 160 to 200 ° C., and the epoxy resin layer 5 melts and flows at this temperature. However, since the softening point of the polyimide film 4 is 300 ° C. or more, the polyimide film 4 melts and flows during molding. Never do. Thus, the insulating layer 11 formed on the flexible substrate 7 is composed of two layers of the polyimide film 4 and the epoxy resin layer 5 that do not melt and flow at a normal molding temperature, so that only the epoxy resin layer 5 is present. The plate thickness accuracy can be improved as compared with the above.

  Next, by performing etching, the metal foil 3 in a predetermined region is removed so as to have a predetermined pattern shape as shown in FIG. 1B to form a conductor circuit 8, and the metal foil other than the region is formed. 3 is removed. Then, the rigid part 1 is formed by laminating the rigid board | substrate 9 in the area | region in which the conductor circuit 8 was formed. The flex portion 2 is formed by removing the metal foil 3 other than the region. Here, as the rigid substrate 9 used for forming the rigid portion 1, a metal-clad laminate such as a copper-clad laminate, which is formed by laminating a metal foil 3 such as a copper foil and a prepreg 12, is used. Can do. As shown in FIG. 1B, since the conductor circuit 8 is formed in advance in a predetermined region on the surface of the polyimide film 4, a single-sided metal-clad laminate may be used as the rigid substrate 9.

  And in order to conduct between the conductor circuits 8 formed in different layers, the through hole 13 and the via hole 14 are formed in the rigid part 1, and the conductor circuit 8 is formed in the outermost layer of the rigid part 1, A flex-rigid printed wiring board A as shown in FIG. 1 (c) can be manufactured. In the flex part 2 of the flex-rigid printed wiring board A thus obtained, the epoxy resin layer 5 that is hard and brittle is covered and protected by the polyimide film 4 that is excellent in flexibility. It can be easily bent at the flex portion 2 as compared with the layer 5 only exposed. The rigid portion 1 can be further multilayered by a build-up method as necessary.

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

(Examples 1 and 2)
First, the flexible substrate 7 used as a core material was produced. The flexible substrate 7 was produced by providing a conductor circuit 8 having a thickness of 18 μm formed of copper on the surface of a substrate 10 having a thickness of 25 μm formed of polyimide resin.

  On the other hand, the resin sheet 6 with metal foil was produced. The resin sheet 6 with metal foil first bonds the copper foil 3 and the polyimide film 4 by thermocompression bonding, and then applies the epoxy resin composition to the surface of the polyimide film 4 and makes this a semi-cured state (B stage state) ) And dried to form an epoxy resin layer 5. The thickness of the copper foil 3 is 18 μm.

  Here, the epoxy resin composition used for the production of the resin sheet 6 with metal foil was 90 parts by mass of “YDB-500” manufactured by Tohto Kasei Co., Ltd., which is a brominated bisphenol A type epoxy resin, and a cresol novolac type epoxy resin. 10 parts by mass of “YDCN-220” manufactured by Toto Kasei Co., Ltd., 2 parts by mass of dicyandiamide, and 0.1 parts by mass of 2-ethyl-4-methylimidazole were prepared.

  Next, as shown in FIGS. 1 (a) and 1 (b), the epoxy resin layer 5 of the resin sheet 6 with metal foil is overlapped on the flexible substrate 7 and heated and pressed to form the resin sheet 6 with metal foil. Bonded to the substrate 7. The molding pressure at this time is 3 MPa, and the molding temperature is 180 ° C.

  Next, by performing etching, the copper foil 3 in a predetermined region is removed so as to have a predetermined pattern shape as shown in FIG. 3 was removed. Then, the rigid part 1 was formed by laminating the rigid board | substrate 9 in the area | region in which the conductor circuit 8 was formed. The flex part 2 was formed by removing the copper foil 3 other than the region. Here, as the rigid board | substrate 9 used for formation of the rigid part 1, the single-sided copper clad laminated board was used.

  And in order to conduct between the conductor circuits 8 formed in different layers, the through hole 13 and the via hole 14 are formed in the rigid part 1, and the conductor circuit 8 is formed in the outermost layer of the rigid part 1, A flex-rigid printed wiring board A as shown in FIG.

(Comparative Examples 1 and 2)
As the resin sheet 6 with a metal foil, the same epoxy resin composition as in Examples 1 and 2 was applied to the surface of a copper foil 3 having a thickness of 18 μm, and this was heated and dried until it became a semi-cured state (B stage state). Then, a flex-rigid printed wiring board A was produced in the same manner as in Examples 1 and 2, except that the epoxy resin layer 5 was used (not shown).

  And the board thickness precision of each flex-rigid printed wiring board A was evaluated. The evaluation of the plate thickness accuracy was performed by measuring the variation in the thickness of the insulating layer 11 after molding. This variation is measured by observing a cross section with a cross section and measuring the distance between the shiny surface (S surface) side of the inner copper foil and the mat surface (M surface) side of the surface copper foil with a stereomicroscope. went. The measurement results are shown in [Table 1] below.

  Moreover, the flexibility of each flex-rigid printed wiring board A was evaluated. Flexibility was evaluated by the MIT test. The test results are shown in [Table 1] below.

  As can be seen from [Table 1] above, in comparison with Comparative Examples 1 and 2, Examples 1 and 2 have less variation in the thickness of the insulating layer 11 after molding and are superior in plate thickness accuracy. It was confirmed.

  In addition, compared with Comparative Examples 1 and 2, it was confirmed that Examples 1 and 2 had a higher number of bendings until breakage and were superior in flexibility.

An example of embodiment of this invention is shown and (a)-(c) is sectional drawing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rigid part 2 Flex part 3 Metal foil 4 Polyimide film 5 Epoxy resin layer 6 Resin sheet with metal foil 7 Flexible substrate 8 Conductor circuit 9 Rigid substrate

Claims (1)

  In a flex-rigid printed wiring board formed by integrating a plurality of rigid parts through a flex part, an epoxy resin of a resin sheet with a metal foil formed by laminating a metal foil, a polyimide film, and an epoxy resin layer in this order The layer is stacked on the flexible substrate, the resin sheet with the metal foil is adhered to the flexible substrate, the metal foil in a predetermined region is removed so as to have a predetermined pattern shape, a conductor circuit is formed, and a rigid substrate is laminated in this region. A flex-rigid printed wiring board, wherein a rigid portion is formed and a metal foil other than the region is removed to form a flex portion.

Images