Itsuo Watanabe

Recent advances of interconnection technologies using anisotropic conductive films in flat panel display applications

Anisotropic conductive films (ACFs) consist of conducting particles and adhesive resins and have been widely used for packaging technologies in FPDs (Flat panel displays) such as LCDs (Liquid crystal displays) for last decades. So far various packaging technologies such as TCP (Tape carrier package) on LCD panel or PWB (Printed wiring board), COF (Chip on flex) on LCD panel or PWB and COG (Chip on Glass) using ACFs have been realized to meet the requirement of fine pitch capability and make the flat panel displays smaller, lighter and thinner. In order to meet fine pitch capability smaller than 50 /spl mu/m pitch, COF technologies has been introduced instead of TCP interconnection. The adhesion characteristics against COF has been improved by optimizing the elastic modulus of ACF and introducing the reaction group into the adhesive resin. It was demonstrated that the developed ACF shows low contact resistance even after exposed to a high temperature humidity test. It was also confirmed that making conducting particles smaller is advantageous for the driver IC with small bump size and space in COG. The warpage behavior of COG has been clarified by the elastic simulation analysis. In addition, it was demonstrated that heating a glass substrate appropriately during COG interconnection and the use of a low stress type of ACF are very effective in reducing the warpage and improving the connection reliability in COG interconnection.

FLIP-CHIP INTERCONNECTION TO VARIOUS SUBSTRATES USING ANISOTROPIC CONDUCTIVE ADHESIVE FILMS

Flip-chip interconnection to various substrates using ACF was investigated. It was demonstrated that the interconnection resistance of the joints made between gold bumps of the chip and Ni/Au coated pads on FR-4 boards was lower than 10 mΩ depending upon the kinds of conducting particles, although the interconnection was due to the mechanical contact between conducting particles and conductor surfaces. The current–voltage characteristics of the interconnection exhibited an ohmic behavior up to currents of 2000 mA per bump. In attaching bumpless chips to various substrates, the interconnection resistance strongly depended on the kinds of conducting particles and substrates. It was demonstrated that Ni particles were favorable for making good electrical contacts between Al pads of the bumpless chip and substrate electrodes. It was also demonstrated that low interconnection resistance in the range of 2 mΩ to 7 mΩ was obtained as well as with bumped chips, when FR-4 boards with Ni/Au bumped pads were used as substrates for interconnecting bumpless chips.

Rewritable optical-disk fabrication with an optical recording material made of naphthalocyanine and polythiophene

A novel rewritable optical disk that uses an optical recording material made of naphthalocyanine and polythiophene as the recording layer is described. In this system the complex refractive index of the recording material changes reversibly, depending on the aggregation states of naphthalocyanine induced by a conformation change of the polythiophene matrix. After recording, the imaginary part of the refractive index of the recording material increases to three times that of the unrecorded part, at a wavelength of 790 nm at which a semiconductor laser emits light. The fabricated polythiophene naphthalocyanine optical disk shows a high reflectivity of 58% and a large readout modulation amplitude (I(11)/I(top)) of 0.63. It is confirmed that the polythiophene/naphthalocyanine optical disk can be played back on conventional compact-disc players even after ten cycles of rewriting.

Thermochromic and photoluminescent properties in Langmuir-Blodgett multilayer thin films containing poly(3-dodecylthiophene)

Abstract Thermochromism and unusual temperature dependence of photoluminescence in Langmuir-Blodgett (LB) thin films consisting of poly(3-dodecylthiophene) and stearic acid were observed. It was found that the color of poly(3-dodecylthiophene)-stearic acid mixed LB films changes at lower temperatures than that of spin-coated films. We also observed that photoluminescence intensity of poly(3-dodecylthiophene) in LB film increases as temperature increases from 25 °C to 100 °C, whereas that in a spin-coated film decreases. This remarkable thermochromism and unusual temperature dependence of photoluminescence in poly(3-dodecylthiophene)-stearic acid mixed LB films can be explained in terms of the conformational changes of poly(3-dodecylthiophene) resulting from a thermally induced disordering process in which poly(3-dodecylthiophene) originally organized in the mixed LB films is disordered on heating.

Effect of encapsulation on OLED characteristics with anisotropic conductive adhesive

Organic light emitting devices (OLEDs) is one of the most potentially interesting display technologies in the flat panel display (FPD) field. This paper investigates the effects of OLED structures and a perimeter encapsulation to protect the OLED from atmospheric exposure. Firstly, the electric features of the OLED devices with and without a copper phtalocyanine layer were measured, and the one with the additional buffer layer showed a lower turn-on voltage. Then the OLED device sample was encapsulated with a glass cover bonded to the substrate with an adhesive matrix containing micro-particles. The samples were stored in ambient conditions, and the IV characteristics were studied with shelf-time as a parameter. The measurement results indicated that the encapsulation had a significant improvement on the device operation. After two weeks of storage the encapsulated samples showed less degradation and the current density at a given operating bias was about fifty percent higher than without encapsulation.

Interconnection Technologies of Anisotropic Conductive Films and Their Application to Flexible Electronics

Anisotropic conductive films (ACFs) consist of conducting particles and adhesive resins and have been widely used for packaging technologies in FPDs (Flat Panel Displays) such as LCDs (Liquid Crystal Displays) for last decades. So far various packaging technologies such as TCP (Tape Carrier Package) on LCD panel or PWB (Printed Wiring Board), COF (Chip on flex) on LCD panel or PWB and COG (Chip on Glass) using ACFs have been developed to meet the requirement of fine pitch capability and make the flat panel displays smaller, lighter and thinner. Also ACFs are flip-chip technologies have been of much interest because they provide higher packaging density than conventional semiconductor packaging technologies such as face-up wire bonding. In addition, ACFs are expected as interconnect materials which realize flexible electronics such as flexible display and RFID (Radio Frequency Identification).

Recent advances of interconnection technologies using anisotropic conductive films

Anisotropic conductive films(ACFs) consists of conducting particles and adhesive resins and have been widely used for packaging technologies in FPDs(Flat panel displays) such as LCDs(Liquid crystal displays) for last decades. So far various packaging technologies such as TCP(Tape carrier package) on LCD panel or PWB(Printed wiring board), COF(Chip on flex) on LCD panel or PWB and COG(Chip on Glass) using ACFs have been realized to meet the requirement of fine pitch capability and make the flat panel displays smaller, lighter and thinner. In order to meet the requirement of finer pitch interconnection of outer lead of TCP in LCD packaging technologies, the influence of conducting particles on contact resistance of ACF joints was investigated. It was found that the 50 micron pitch of outer lead interconnection of TCP is realized by optimizing the hardness of conducting particles. In addition, to meet fine pitch capability smaller than 50 micron pitch, the improvement of the adhesion characteristics against COF has been demonstrated in outer lead interconnection. It was confirmed that making conducting particles smaller is advantageous for the driver IC with small bump size and space in COG. Low temperature curable ACF using new curing system which cross-links at 140 degrees C in 10 sec bonding has been demonstrated in TCP/PWB interconnection.

19.1: Invited Paper: Driver IC Packaging Technologies Using Anisotropic Conductive Films in Flat Panel Display

Anisotropic conductive films (ACFs) are adhesive films with anisotropic conductivity induced by dispersing conducting particles such as metal coated plastic balls and metal particles into polymer matrices such as thermoplastics and thermosetting resins. ACFs have been widely used for driver IC packaging technologies in FPDs(Flat panel displays) such as LCDs(Liquid crystal displays) for last two decades. So far various packaging technologies such as TCP(Tape carrier package) on LCD panel or PWB(Printed wiring board), COF(Chip on flex) on LCD panel or PWB, and COG(Chip on Glass) using ACFs have been realized to meet the requirement of fine pitch capability and make the flat panel displays smaller, lighter and thinner. In this paper, the history of ACF and driver IC packaging are described. In addition, it is mentioned that how important driver IC packaging is in implementing the miniaturization, high resolution, low cost and high display quality. ACF material design for COF which is advantageous in fine pitch interconnection is described. It is indicated that low temperature curable ACF is very useful in improving productivity of LCD modules and reducing the thermal stress at the interface in large LCD modules. We also indicates that the warpage of LCD panel after COG interconnection induces the light linkage issue in LCD modules. Lowering bonding temperature of ACF is also very important in reducing the warpae issue and avoiding the light linkage issue when COG is applied for driver IC packaging in large LCD modules.

Experimental Investigation and Micropolar Modelling of the Anisotropic Conductive Adhesive Flip-Chip Interconnection

A conductive adhesive is a promising interconnection material for microsystem packaging. The interconnect features are of great importance to system responses under various loading conditions. The flip-chip packaging system with anisotropic conductive film (ACF) joint under thermal loadings has been investigated both experimentally and theoretically. The displacement distributions have been measured by an interferometer, which could provide the in-plane whole-field deformation observation. The interconnection is of much smaller scales compared with the neighbouring components such as the chip and substrate, and there are even finer internal structures involved in the joint. The wide scale range makes both experimental observation and conventional simulation difficult. A micropolar model is thus developed. Utilizing the homogenization, this model requires low computation resource. Combination of this model with a second-order model was able to produce a highly efficient and valid prediction of the packaging system response under thermal and mechanical loadings. Comparison of the micropolar model simulation and experimental data shows good agreement.