JP2007036001A - Rigid flex multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rigid flex multilayer printed wiring board which is excellent in connection reliability of blind via holes and through holes, flex part flexibility and low cost.
A rigid-flex multilayer printed wiring board comprising a rigid substrate divided into a plurality of blocks and a bendable flex substrate connecting between the plurality of rigid substrates, at least a component of the flex substrate Rigid-flex multilayer printed wiring board, wherein the flex base substrate is not in contact with the blind via hole and / or through hole for interlayer connection, and also serves as a protective layer for the outer layer wiring pattern .
[Selection] Figure 2

Description

  The present invention relates to a rigid flex multilayer printed wiring board, and more particularly to a rigid flex multilayer printed wiring board in which a flex substrate is laminated on an outer layer.

  In recent years, the demand for rigid-flex multilayer printed wiring boards, which are excellent in the degree of freedom of placement in products, has increased as a configuration of printed wiring boards incorporated in products due to the downsizing and high functionality of equipment, especially recently. For reasons such as the ease of manufacturing methods, a configuration in which a flex substrate is arranged in an outer layer is increasing.

  As such a rigid-flex multilayer printed wiring board, a rigid-flex multilayer printed wiring board Pa configured as shown in FIG. 3 is already known (see Patent Document 1).

  That is, the wiring pattern 2 is formed on the front and back of the insulating layer 1, and the core substrate 9a is provided on the one surface of the core substrate 9a. An insulating adhesive layer 15 having a similar opening 14a provided at the same site as the opening 8 and a flex substrate 12 having a wiring pattern 2c on the flex base substrate 10 laminated via the insulating adhesive layer 15. Between the wiring pattern 2d laminated via the build-up insulating layer 6 provided with the same opening 14b at the same position as the opening 8 on the other surface of the core substrate 9a, and the adjacent wiring pattern forming layer It consists of a blind via hole 7b to be connected, a through hole 20 for connecting a wiring pattern between the front and back sides, and a solder resist 21 for protecting the outer layer wiring patterns 2c and 2d. By forming the plating layer when forming the line via hole 7b and the through hole 20 as one layer, the outer layer wiring patterns 2c and 2d can be easily miniaturized, and small electronic components can be mounted on the front and back of the printed wiring board Pa. (R in the figure is a “rigid part” and F is a “flex part”).

  However, the configuration of the rigid flex multilayer printed wiring board Pa has the following problems.

  That is, since the coverlay that reduces the connection reliability of the through hole is not used as a protection for the wiring pattern 2c of the flex board 12, the connection reliability of the through hole 20 can be secured to some extent, Since the through hole 20 has a structure that penetrates the flex base substrate 10 having a linear expansion coefficient different from that of the core substrate 9a or the like, the connection reliability is higher than that in the case where the through hole is formed only in the rigid substrate such as the core substrate 9a or the like. It was that the nature would be low.

  Further, the solder resist 21 is used in place of the coverlay as a protection for the wiring pattern 2c of the flex board 12. However, since the solder resist has to be flexible, the cost is low. It was a disadvantageous structure.

Furthermore, plating for forming the blind via hole 7b and the through hole 20 is deposited on the wiring pattern 2c located in the flex portion F of the flex substrate 12, and the conductor thickness of the wiring pattern 2c is increased. There was a problem that the flexibility decreased.
JP 2004-349277 A

  An object of the present invention is to provide a rigid-flex multilayer printed wiring board that is excellent in connection reliability of blind via holes and through-holes, flexibility of flex portions, and low cost.

  The present invention is a rigid-flex multilayer printed wiring board comprising a rigid board divided into a plurality of blocks and a bendable flex board connecting the plurality of rigid boards, and at least a constituent material of the flex board Rigid-flex multilayer printed wiring board, wherein the flex base substrate is not in contact with the blind via hole and / or through hole for interlayer connection, and also serves as a protective layer for the outer layer wiring pattern This solves the above problem.

  By adopting the configuration of the rigid flex multilayer printed wiring board according to the present invention, the blind via hole and the through hole are configured not to penetrate the flex base substrate having different linear expansion coefficients. Therefore, the connection reliability of the blind via hole and the through hole is improved. Sex can be secured. In addition, since the flex base substrate is used as a protective layer for the outer layer wiring pattern, it is not necessary to use an expensive flexible solder resist or the like, which can reduce costs and manufacturing processes. In addition, since no plating is deposited during the formation of blind via holes or the like, it is possible to prevent a decrease in the flexibility of the flex portion.

  An embodiment of the present invention will be described with reference to a schematic cross-sectional manufacturing process diagram of a rigid flex multilayer printed wiring board shown in FIG. In addition, the same code | symbol was attached | subjected to the site | part same as a prior art.

  First, a four-layer core substrate 9 as shown in FIG. 1A is produced by a general construction method.

  Briefly, a double-sided substrate in which metal foils are laminated on the front and back of the insulating layer 1 is prepared, and through holes are drilled in desired portions.

  Next, after performing the desmear process of the through hole, electroless plating (for example, electroless copper plating) and electrolytic plating (for example, electrolytic copper plating) are performed to make the through hole conductive.

  Next, the insulating resin 4 is filled in the through-holes subjected to the conductive treatment, and then plating (for example, copper plating) is deposited on the entire surface, and then the wiring pattern 2 is formed on the front and back surfaces by a general subtractive method. In addition, a double-sided board on which a buried hole 3 (having an insulating resin 4 filled in the hole and a lid plating 5 for closing the hole filled with the insulating resin 4) for connecting the front and back wiring patterns 2 is formed. 1a is obtained.

  Next, after the build-up insulating layer 6 and the metal foil are laminated on the front and back of the double-sided board 1a, the wiring pattern 2a is formed on the surface of the build-up insulating layer 6, and the wiring pattern 2, 2a is connected to the blind. A via hole 7 is formed, and then an opening 8 is provided at a portion to be a flex portion F that can be bent later, thereby obtaining the four-layer core substrate 9 shown in FIG.

  Next, a flex substrate 12 having metal foils 11 laminated on the front and back sides of the flex base substrate 10 is prepared, and a wiring pattern 2b is formed on one surface by a general subtractive method. A cover lay 13 (the cover lay is formed by applying polyimide, epoxy, urethane, polyol, or the like, or affixing these films) is formed on a portion that will later become the flex portion F.

  Next, an insulating adhesive layer 15 such as a prepreg provided with a similar opening 14 is prepared in the same portion as the opening 8 provided in the core substrate 9, and then, as shown in FIG. The insulating adhesive layer 15 and the flex substrate 12 are sequentially aligned and arranged on the front and back of the core substrate 9, and then laminated and integrated.

  Next, as shown in FIG. 1 (c), by performing an etching process on the metal foil 11 laminated on the other surface of the flex substrate 12, a window portion 16 is formed at a portion where the flex base substrate 10 is removed. Form.

  Next, as shown in FIG. 1D, laser processing or etching processing (the etching processing here is, for example, etching processing for removing the flex base substrate 10 (for example, polyimide)). After removing the flex base substrate 10 exposed from the window portion 16, the window portion 16 is irradiated with a laser as shown in FIG. 2E, thereby forming the blind via hole 7a. A through hole for forming a through hole 20 for drilling a non-through hole 17 and exposing the wiring pattern 2b formed on one surface of the flex substrate 12 and then connecting the wiring pattern between the front and back surfaces at a desired position. The hole 18 is drilled by drilling or the like.

  Here, as a step of removing the flex base substrate 10 exposed from the window portion 16, the flex base substrate 10 exposed from the window portion 16 is drilled before the non-through hole 17 and the through hole 18 are drilled. Although the example of removing was shown, it can also be performed after the non-through hole 17 and the through hole 18 are drilled.

  Next, as shown in FIG. 2F, after the inside of the non-through hole 17 and the through hole 18 is cleaned by a desmear process, an electroless plating process (for example, an electroless plating process), an electroplating process (for example, Then, the plating 19 is filled in the non-through holes 17 and deposited on the entire surface including the inside of the through holes 18 by sequentially performing an electrolytic copper plating process using a plating solution for filled vias.

  Next, as shown in FIG. 2 (g), the rigid portion R in which the via pattern 2b and the blind via hole 7a connecting the wiring pattern forming layers and the through hole 20 are formed by a general subtractive method. A rigid flex multilayer printed wiring board P composed of the flex part F is obtained.

  In describing the present invention, a six-layer rigid-flex multilayer printed wiring board in which a flex substrate is laminated on the outer layer of a four-layer core substrate has been described as an example. Can also be changed.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic cross-sectional process explanatory drawing which shows the manufacturing process (a)-(d) of the rigid flex multilayer printed wiring board of this invention. FIG. 2 is a schematic cross-sectional process explanatory diagram illustrating manufacturing steps (e) to (g) subsequent to FIG. 1. The schematic cross-section explanatory drawing of the conventional rigid flex multilayer printed wiring board.

Explanation of symbols

1: Insulating layer 1a: Double-sided board 2, 2a, 2b, 2c, 2d: Wiring pattern 3: Belle hole 4: Insulating resin 5: Lid plating 6: Build-up insulating layers 7, 7a, 7b: Blind via hole 8: Openings 9, 9a: Core substrate 10: Flex base substrate 11: Metal foil 12: Flex substrate 13: Coverlay 14, 14a, 14b: Opening 15: Insulating adhesive layer 16: Window portion 17: Non-through hole 18: Through hole 19: Plating 20: Through hole 21: Solder resist P, Pa: Rigid flex multilayer printed wiring board R: Rigid part F: Flex part

Claims (1)

  A rigid-flex multilayer printed wiring board comprising a rigid substrate divided into a plurality of blocks and a bendable flex substrate connecting the plurality of rigid substrates, at least a flex base that is a component of the flex substrate A rigid-flex multilayer printed wiring board, wherein the substrate is not in contact with a blind via hole and / or a through-hole for interlayer connection, and also serves as a protective layer for an outer-layer wiring pattern.

Images