Patent Application
20050183884
The present invention relates to a flexible printed circuit board, particularly to a flexible printed circuit board with an anisotropic conductive film, which has even and low impedance, even breakage of conductive particles, even pressure, and thus has good reliability of the anisotropic conductive film for use in handheld electrical devices.
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The anisotropic conductive film 8121 contains plural conductive particles. The conductive particles must be broken in order to conduct electricity, if not, they cannot conduct electricity. However, the conductive particles are often broken unevenly. Though the conductive particles of uneven breakage can still conduct electricity, they could reduce the reliability of the anisotropic conductive film 8121. In the conventional technique, the pitch of the anisotropic conductive film 8121 is about 0.1 mm, as shown in the A and B portions of
In order to overcome the drawbacks in the prior art, a flexible printed circuit board is provided. In the particular design, the anisotropic conductive film with broadened pitch has the features of even and low impedance, even breakage of conductive particles, even pressure, and thus the anisotropic conductive film for use in handheld electrical devices will have good reliability.
It is an object of the present invention to provide a flexible printed circuit board with an anisotropic conductive film for use in handheld electrical devices.
It is another object of the present invention to provide a flexible printed circuit board with an anisotropic conductive film, which has the features of even and low impedance, even breakage of conductive particles, even pressure, and thus a good reliability of the anisotropic conductive film for use in handheld electrical devices is achieved.
In accordance with an aspect of the present invention, a flexible printed circuit board includes a substrate layer; at least a circuit layer formed on the substrate layer; and a conductive film layer formed on one end of the circuit layer, characterized in that a pitch of the conductive film layer is broadened to be ranged from 0.5 mm to 3.0 mm.
Preferably, the other end of the circuit layer is formed to be a golden-finger region and is electrically connected to the LCD circuit board.
Preferably, the anisotropic conductive film includes conductive particles and sticky polymers.
Preferably, the conductive particles are one of metal-plated polymer particles and nickel particles.
Preferably, the metal of the metal-plated polymer particles is selected from a group consisting of a nickel, a copper, a gold, and a silver.
Preferably, the substrate layer is a plastic layer.
Preferably, the plastic layer includes a polyimide layer and a polypropylene/epoxy resin layer.
Preferably, the plastic layer includes a polyimide layer.
Preferably, the circuit layer is a copper circuit layer.
Preferably, the circuit layer further includes an integrated circuit disposed thereon which is packaged by using one of a tape carrier package and a chip on film.
Preferably, the circuit layer further includes surface mounting devices.
Preferably, the conductive film is an anisotropic conductive film.
Preferably, the flexible circuit board is connected to a liquid crystal display via the conductive film layer.
In accordance with another aspect of the present invention, a flexible printed circuit board includes at least two substrate layers; at least a circuit layer formed between every adjacent two substrate layers; and at least a conductive film layer formed on one end of the circuit layer, characterized in that a pitch of the conductive film layer is broadened to be ranged from 0.5 mm to 3.0 mm.
Preferably, the other end of the circuit layer is formed to be a golden-finger region and is electrically connected to the LCD circuit board.
Preferably, the anisotropic conductive film includes conductive particles and sticky polymers.
Preferably, the conductive particles are one of metal-plated polymer particles and nickel particles.
Preferably, the metal of the metal-plated polymer particles is selected from a group consisting of a nickel, a copper, a gold, and a silver.
Preferably, the substrate layer is a plastic layer.
Preferably, the plastic layer includes a polyimide layer and a polypropylene/epoxy resin layer.
Preferably, the plastic layer includes a polyimide layer.
Preferably, the circuit layer is a copper circuit layer.
Preferably, the circuit layer further includes an integrated circuit disposed thereon which is packaged by using one of a tape carrier package and a chip on film.
Preferably, the circuit layer further includes surface mounting devices.
Preferably, the conductive film is an anisotropic conductive film.
Preferably, the flexible circuit board is connected to a liquid crystal display via the conductive film layer.
The foregoing and other features and advantages of the present invention will be more clearly understood through the following descriptions with reference to the drawings, wherein:
The present invention will now be described more specifically with reference to the following embodiments. In the first embodiment of the present invention, the flexible printed circuit boards 1, 1′ with the broadened anisotropic conductive film respectively have the main portions 11, 11′. Please refer to
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In the second embodiment of the present invention, the flexible printed circuit boards 1, 1′ are all-polyimide flexible laminae. For example, it has two layers, three layers, four layers, and six layers.
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In the anisotropic conductive adhesive or anisotropic conductive films 121, 121′ of the present invention, usually the conductive particles are dispersed and mixed in the polymers in a random fashion. The sticky polymers are subsequently transformed into the solid thin films. The conductive particles, typically as small as a few microns in diameter, are usually gold-plated polymers or nickel particles. The interconnection, between the anisotropic conductive adhesive or anisotropic conductive films 121, 121′ of the LCD display circuit board and the Indium-tin oxide layers 21, 21′ of the LCDs 2, 2′, is achieved by causing the break of the conductive particles with the hot bar. Hence the electricity is conducted along the films. The above process is called thermocompression process. Furthermore, during the thermocompression process the space between the Indium-tin oxide layers 21, 21′ and the anisotropic conductive films 121, 121′ are filled with the sticky polymers.
The core substance of the conductive particles is the thermosetting and the thermoplastic polymers. Further, the surface of core particles is processed by the method of surface metalization so as to make conductive particles. The requirement of the product is that the fine pitch is under 0.1 mm. The present invention can be applied to a fine pitch interconnection in the following fields: anisotropic conductive film (ACF), anisotropic conductive adhesive (ACA), liquid crystal display (LCD)/TAB, liquid crystal display (LCD)/FPC, chip of glass (COG), chip on film (COF), electrolumine scence (EL) electrode, flip chip, and etc. Thus, the present invention with a fine pitch interconnection is indispensable in the LCD and semiconductor industries.
The above-mentioned polymers of conductive particles can be plated with a layer of nickel, copper, gold, or silver so as to form 0.5-4 mm particles in diameter. Furthermore, the techniques of emulsification synthesis and surface transforming are used for metalizing the surface of the polymers. Accordingly, the cores of the conductive particles are polymers with even particles having same diameters so that they can enhance the conductivity while connected. The anisotropic conductive adhesive or anisotropic conductive films 121, 121′ has an area the same with the area of the indium-tin oxide layers 21, 21′ so that the impedance is reduced. Therefore, since the conductive particles on the anisotropic conductive film 121, 121′ have even sizes and good conductivity. The anisotropic conductive film 121, 121′ provided in the present invention can be adapted to the standards in the IC industry. In other words, even if the pitch is broadened up to 0.5 mm owing to the product requirement, the anisotropic conductive film is still smooth and has excellent conductive interconnection.
While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.
