Flex-rigid wiring board

a wiring board and rigid technology, applied in the field of wiring boards, can solve the problems of delayed signal propagation, more serious delay in signal propagation, and unstable high-speed signal transmission, and achieve the effect of stable signal transmission

Inactive Publication Date: 2008-05-08
IBIDEN CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0008] The present invention has an object to overcome the above-mentioned drawbacks of the related art by providing a flex-rigid wiring thinner than the conventional one and that is excellent in electrical properties and reliability of the conductive layer penetrating flexible and rigid substrates, can transmit high-frequency electrical signals with a less delay and has a connecting structure more advantageous for assuring a stable signal transmission.
[0009] The inventors of the present invention had devoted themselves to attaining the above object. The inventors found it possible to transmit GHz-level electrical signals with an improved stability by electrically connecting a rigid substrate and flexible substrate not through the plated through-hole as in the conventional technology but via an anisotropic conductive adhesive layer interposed between conductive layers of substrate portions including interconnecting electrode pads, and thus worked out the present invention.

Problems solved by technology

However, the wiring board in which a flexible substrate and rigid substrate are electrically connected to each other through a plated through-hole with the above-mentioned conventional wiring-board technology is not advantageous in that when it is used with a frequency of higher than 1 GHz, signal propagation is delayed and high-speed signal transmission is not stable.
Especially when the wiring board is used with a frequency of higher than 5 GHz, the signal propagation is more seriously delayed and instability of the high-speed signal transmission is greater.
Also, the wiring board produced with the conventional wiring-board technology was found, as a result of the reliability test made in the cooling / heating cycle test, to have the electrical connection thereof deteriorated.
Further, since the conventional flex-rigid wiring board is formed either by fixing a flexible substrate to an outermost rigid substrate with an anisotropic adhesive or by laying a flexible substrate between both outermost rigid substrates, so it cannot be designed thinner.

Method used

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Examples

Experimental program
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Effect test

example 1

[0117] (A) Preparing a Flexible Substrate

[0118] (1) For producing the flex-rigid wiring board as the example 1 of the present invention, a laminated film (ESPANEX SB by Shin-Nittetsu Chemicals) formed from a 25 μm-thick insulative film 11 of polyimide resin having a 30 μm-thick copper foil 12 laminated on either side thereof (as in FIG. 1(a)) is used as a base material for preparation of a flexible substrate 100A included in the flex-rigid wiring board.

[0119] (2) A resist layer is formed on the copper foil on the laminated film, and exposed to light and developed to form a circular opening of 300 μm in diameter. The copper foil was etched using a cupric chloride aqueous-solution to form the opening in the copper foil. Carbon-dioxide laser or the like is irradiated to the opening to form an opening 14 that penetrates the resin layer to the copper foil on the back of the insulative film (as in FIG. 1(b)).

[0120] (3) The opening 14 formed in the step (2) above is fully filled with co...

example 2

[0137] A flex-rigid wiring board is produced similarly to the aforementioned example 1 except that each coverlay 24 formed on the flexible substrate 100A is formed to a thickness of 25 μm.

example 3

[0138] A flex-rigid wiring board is produced similarly to the example 1 except that each coverlay 24 formed on the flexible substrate 100A is formed to a thickness of 40 μm.

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Abstract

In a flex-rigid wiring board in which a rigid substrate formed from a rigid base material and a flexible substrate formed from a flexible base material are stack-joined and electrically connected to each other, the flexible substrate including a conductive layer having interconnecting electrode pads provided on at least one surface thereof, and the rigid substrate including a conductive layer having interconnecting electrode pads provided on at least one surface thereof in a position opposite to the interconnecting electrode pads on the rigid substrate, are locally connected electrically to each other with an anisotropic conductive adhesive layer interposed between conductive layers of substrate portions each including at least the interconnecting electrode pads. In this flex-rigid wiring board, transmission of high-frequency signals can be prevented from being delayed, noises can be suppressed, and an excellent electrical connection and connection reliability be assured.

Description

CROSS REFERENCE OF RELATED APPLICATION [0001] This application is a divisional of U.S. application Ser. No. 10 / 558,289, filed Nov. 28, 2005, which is a national stage of PCT / JP05 / 09819, filed May 23, 2005, and further is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2004-173414, filed Jun. 11, 2004.FIELD OF THE INVENTION [0002] The present invention generally relates to a wiring board including a flexible substrate and rigid substrate, and more particularly to a wiring board characterized in the connection between a flexible substrate and rigid substrate stack-joined to each other in a rigid portion, among others, of the wiring board. BACKGROUND ART [0003] The recent portable electronic devices such as a foldable mobile phone and the like use a flex-rigid wiring board. Normally in such a wiring board, rigid or non-flexible portions and a flexible portion are joined to each other with a flexible substrate laid between them, and wiring pa...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H05K3/00H05K1/14H05K3/28H05K3/32H05K3/36H05K3/46
CPCH05K1/117H05K3/244H05K3/323H05K3/361H05K3/4614H05K3/462Y10T29/49126H05K2201/09063H05K2201/09481H05K2201/096H05K2201/09781H05K2201/09845H05K2203/063H05K3/4691H05K1/14H05K3/36
Inventor KAWAGUCHI, KATSUOFUTAMURA, HIROFUMIMIKADO, YUKINOBUITO, SOTAROU
Owner IBIDEN CO LTD
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