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Wired circuit board and producing method thereofWired circuit board and producing method thereof description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20090142478, Wired circuit board and producing method thereof. Brief Patent Description - Full Patent Description - Patent Application Claims
This application claims priority benefits on the basis of Japanese Patent Application No. 2005-355089 filed on Dec. 8, 2005, the disclosure of which is incorporated herein by reference. 1. Field of the Invention The present invention relates to a wired circuit board and a method of producing the same, more particularly, to a wired circuit board including, for example, a suspension board with circuit and the like and a producing method thereof. 2. Description of the Prior Art There has been conventionally known a suspension board with circuit including a metal supporting board made of stainless steel, an insulating layer made of a resin, and a conductive pattern made of copper, which are formed successively on the metal supporting board. In such a suspension board with circuit, a metal supporting board is made of stainless steel, so that a transmission loss is increased in a conductive pattern. To reduce the transmission loss, it has been proposed that a lower conductor made of copper or a copper alloy containing mainly copper is formed on a suspension made of stainless steel and then an insulating layer, a conductor on the recording side and a conductor on the playback side are successively formed on the lower conductor (see, e.g., Japanese Unexamined Patent Publication No. 2005-11387). However, in the proposal mentioned above, the insulating layer is formed directly on the lower conductor so that an ion migration phenomenon occurs in which the copper or the copper alloy containing mainly copper of the lower conductor migrates to a surface of the insulating layer or to the inner portion thereof with moisture or water absorption by the insulating layer in the presence of an electric current or voltage. This occasionally causes defective adhesion between the lower conductor and the insulating layer or defective conductivity of the conductors on the recording and playback sides. When the insulating layer is formed on the lower conductor in the form of a pattern by exposing the photosensitive synthetic resin to light and developing it, an exposure mask must be disposed precisely on the upper portion of the lower conductor, thereby requiring a positioning mark provided on the suspension board. In order to precisely detect the positioning mark, since it is optically detected, an optically distinguishable contrast is required between the surface of the positioning mark and the surface around the positioning mark. It is therefore an object of the present invention to provide a wired circuit board and a producing method thereof which can precisely form an insulating layer and reduce transmission loss with a simple layer structure and also features excellent long-term reliability by preventing the occurrence of an ion migration phenomenon between each of a ground layer and a positioning mark, and an insulating layer to improve the adhesion between each of the ground layer and a positioning mark, and the insulating layer and the conductivity of a conductor. The present invention provides a novel wired circuit board comprising a metal suspension board, a first thin metal film formed on the metal suspension board, a ground layer and a positioning mark layer formed on the first thin metal film, a second thin metal film formed on the ground layer and the positioning mark layer, an insulating layer formed on the second thin metal film, a conductive pattern formed on the insulating layer. In the wired circuit board of the present invention, it is preferable that the ground layer and the positioning mark layer are formed of copper and the second thin metal film is formed of nickel. The method of producing the wired circuit board of the present invention comprises the steps of; preparing a metal suspension board; forming a first thin metal film on the metal suspension board; forming a resist on the first thin metal film to have a pattern; forming a ground layer and a positioning mark layer on the first thin metal film exposed from the resist; forming a second thin metal film on the ground layer and the positioning mark layer and removing the resist; forming an insulating layer on the second thin metal film; and forming a conductive pattern on the insulating layer. In the method of producing the wired circuit board of the present invention, it is preferable that the positioning mark layer is formed of copper and the second thin metal film is formed of nickel. The wired circuit board according to the present invention can precisely form the insulating layer and reduce transmission loss with a simple layer structure. Moreover, since the second metal thin film is formed between each of the ground layer and the positioning mark layer, and the insulating layer, the occurrence of the ion migration phenomenon between each of the ground layer and the positioning mark layer, and the insulating layer is prevented with the simple layer structure. As a result, it is possible to sufficiently improve the adhesion between each of the ground layer and the positioning mark layer, and the insulating layer as well as the conductivity of the conductor to ensure excellent long-term reliability. In addition, according to the method of producing the wired circuit board of the present invention, the positioning mark layer and the ground layer can be formed on the first thin metal film at the same time. Since the second thin metal film is formed on the ground layer and the positioning mark layer, and then the regist is removed, therefore, in the process of forming the insulating layer, the second thin metal film is formed on the ground layer and the positioning mark layer, whereas the first thin metal film is exposed in the portion other than above. This ensures to make an optically distinguishable contrast between the second thin metal film formed on the positioning mark layer and the first thin metal film exposed therearound. As a result, the positioning mark can be accurately detected and thus the insulating layer can be precisely formed in the insulating layer forming process. Continue reading about Wired circuit board and producing method thereof... Full patent description for Wired circuit board and producing method thereof Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Wired circuit board and producing method thereof patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Wired circuit board and producing method thereof or other areas of interest. ### Previous Patent Application: Portable electronic device and transferring method of circuit element thereof Next Patent Application: Method of manufacturing semiconductor device-fabrication wafer holder Industry Class: Coating processes ### FreshPatents.com Support Thank you for viewing the Wired circuit board and producing method thereof patent info. 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