Development of Anisotropic Conductive Film Using Pb-free Solder and Its Application to the Micro-joining of IC-chip

本研究的目的是利用新型微连接技术所必需的无铅焊料制备一种全新的、独特的各向异性导电膜，该各向异性导电膜可应用于电极间距小于20 ~ 30微米的IC芯片上。此外，电极的形状和排列也没有限制。除了取得各向异性导电膜外，还从实验和理论上获得了设计和研制无铅焊料所需的基本信息。由此，建立了利用光刻技术制备具有直径为10微米的细孔的绝缘膜（聚酰亚胺膜）的工艺。此外，该技术与电镀技术相结合，可以使该工艺易于将焊料颗粒填充到绝缘膜上的细孔中。本研究确定了Sn-Pb和游离Pb焊料的最佳电沉积条件（电流密度和时间）。利用本研究开发的各向异性导电膜，在实际的集成电路芯片微连接中尝试了柔性印制板上电极的连接。结果表明，所制备的各向异性导电膜具有良好的粘结性和实用化的可能性。此外，提出了一种不同类型的各向异性导电膜，其中包含分散在热固性树脂中的焊料颗粒，并通过在柔性印制板上的实际粘接证明了其实用性。本研究还对锡合金在极低温下的熔化温度、强度、导电性、润湿性和相稳定性等方面的信息进行了实验积累，为进一步设计新型各向异性导电膜所需的新型无铅钎料合金提供了依据。

The purpose of this study was to develop a quite new and unique anisotropic conductive film using Pb free solder which is necessary for a new micro-joining technology This anisotropic conductive film could be applicable to the IC chip with the electrode pitch less than 20〜30 micron. Besides, there is no restriction of the shape and arrangement of electrodes. Except for the development of anisotropic conductive film, fundamental information necessary for the design and development of Pb free solder was also obtained experimentally and theoretically.As the results, the technology for making the insulation film (polyimide film) which has fine and line up holes with a diameter of 10 micron was established by utilizing photolithography technique. In addition, it was demonstrated that the combination of this technique and the electroplating technique could make the process easy to fill solder particles up into fine holes on the insulation film. The optimum conditions for the electro-deposition (current density and time) of Sn-Pb and Pb free solders were determined in this study. By using the anisotropic conductive film developed in this study, the joining of electrodes on flexible printed board was tried by utilizing the bonding machine for practical IC chip micro-joining. It was confirmed that the good joining could be attained, and the possibility for the practical use of developed anisotropic conductive film. Moreover, a different type anisotropic conduction film contains solder particles dispersed in thermosetting resin was proposed, and the usefulness of it was shown by the practical bonding of the electrode on flexible printed board. Also in this study, the accumulation of information on melting temperature, strength, conductivity, wettability and phase stability of Sn alloys at extremely low temperature were carried out experimentally for the further design of new Pb-free solder alloys necessary for the new anisotropic conductive film.