| Mar. 26, 2004 | ||
Toray Succeeds in Development of Flexible Circuit Board With World's Highest Level of Density, Enabling Miniaturization, Improved Performance and Lower Costs for LCD Driver ICs |
||
| Toray Industries, Inc. succeeded in the development
of a very high-density flexible printed circuit board (FPC hereinafter) that
has the highest density level in the world. This technology will help to miniaturize
the driver ICs for liquid crystal displays by more than 30%. The mass production of FPCs with IC connection leads having a 35µm wiring pitch has already started. The existing technology, however, limits the fineness of the pitch to about 30µm and it is nearing the limitation in terms of miniaturization. The company, by combining its fine pitch wiring technology that uses photosensitive polymer and the new technology that decreases the dimensional change of polyimide film, broke through the existing limitations and made possible a wiring pitch of 25µm (10µm for the line width and 15µm for space). At the same time, Toray discovered an essential solution for “total accuracy” which expresses the smallness of the error in the distance between IC connection leads, the most important factor in miniaturization. It succeeded in improving the accuracy to better than ±0.02%, more than double the ±0.04%, which was thought to be the limitation so far.
Toray has proved that it can achieve excellent total accuracy when attaching this FPC to a 20mm IC chip with 800 pins (electrodes) at 25µm pitch and has started supplying samples to some of the probable customers. Toray aims to commercialize this technology in 2005. With this fine pitch FPC, the width of the row of IC connection leads can be reduced by 30% or if the width is the same, the number of leads can be increased by about 1.4 times, leading to miniaturization, improved performance and lower costs of the LCD driver IC and eventually of the LCD itself. Furthermore, this technology can also be applied to extremely flexible polyimide films with 25µm thickness. In addition to FPCs for LCD driver IC, this can be adopted in a wide range of markets including FPCs that are folded for three-dimensional packaging such as in electronic circuits for mobile phones, digital cameras etc. Along with the improvements in LCD’s resolution and miniaturization of IC, FPCs have also been miniaturized. Especially for use in mobile phones, and along with the heightened demand for higher performance, smaller size and lower cost in recent years, companies have been striving to make LCD driver IC with more pins and with finer pitch. With the existing technologies, however, it was extremely difficult to make FPCs with pitch that is finer than 30µm and there was little hope for achieving it. In general, LCD driver IC has a length of 10mm to 20mm and several hundred pins on the length side need to be accurately connected to the same number of IC connection leads that are on the FPC. In the FPC processing with the existing technology, however, the limitation of total accuracy is said to be ±0.04%. This translates to a dimensional change of ±4µm for a length of 10mm, meaning it is difficult to connect the IC accurately to leads when wiring pitch is less than 30µm. The polyimide film that forms the base has features such as superior mechanical properties, electrical properties and heat/chemical resistance. On the other hand, when dimension changes occur due to the expansion / shrinkage caused by the influence of temperature or humidity, the polyimide film, along with exhibiting distortions (measured in µm), also shows a disposition where some of the dimensions do not return to the original levels even after the temperature / humidity conditions are back to the original levels. This is the principal cause of the above-mentioned positioning error. Toray, exploiting the technological expertise it accumulated over the years dealing with polyimide resins and its know-how in handling film manufacturing, succeeded in developing a new technology for controlling the dimension changes that occurs while manufacturing polyimide films In “Subtractive method”, the commonly used wiring technology, a copper layer is plated on the film and masked with photoresist (photosensitive resin) and the conducting pattern is formed by etching (removing) the non-circuit areas off using solution. In this case, since the wiring cross-section is trapezoidal in nature, it is difficult to secure the line width and the precision control for space when doing fine pitch wiring. The company, in place of the subtractive method, employed the “semi-additive method”, which enables minute control of the wiring pattern and is also suited for fine pitch wiring. By growing a copper layer with perpendicular side wall using electroplating at the openings in photoresist, it succeeded in developing wiring that is accurate and minute. This technology, in theory, should produce extremely high total accuracy and we are at the stage of attaining a total accuracy better than ±0.01%. In addition, we have succeeded in theoretically proving that it is possible to gain a total accuracy one digit higher than existing technology. In the future, along with IC Bonder (mounting equipment) manufacturer, Toray Engineering Co., Ltd, we’re planning to provide total solutions for the FPC business and to push forward with making this technology commercially viable, keeping in perspective the developments of high-density FPC processing business on its own. Toray has been putting about 60% of its strategic development potential into the three growing areas of “Information and Telecommunications,” “Life Sciences” and “Environment/Safety/Amenity.” Among the three, Information and Telecommunication field has occupied about 30% of the strategic attention. In the FPC parts-related business, which is at the core of the Electronics and Information-related Products, the company has garnered a large share in the tapes used for TAB (Tape Automated Bonding), which is in turn used for mounting the LCD driver IC, because of its highly-rated superior bonding qualities and reliability. Toray also has succeeded in the development of highly flexible epoxy adhesive and halogen-free, flame-retardant epoxy adhesive and commercialized FPC material employing them in 2003. It has also started the development of a polyimide adhesive that is highly reliable compared to the existing products, with an aim to make it commercially viable in fiscal year 2004. At the same time, Toray Group is engaged in a wide range of operations through Du Pont-Toray Co. Ltd., which produces polyimide film “Kapton*” for flexible printed circuit boards, Toyo Metallizing Co. Ltd., which makes plated polyimide film “Metaloyal,” and STEMCO Ltd. (South Korea), which operates a circuit board processing business. Toray, with its comprehensive strength, aims to continue to propose new values by creating innovative and large-scale materials in the information and telecommunication field. * “Kapton” is a registered trademark of E.I.du Pont de Nemours and Company |
||
| # # # |
 |
||
 |
|
Back to News Index |
