Journal of the Microelectronics & Packaging Society Vol. 10, No. 3, p. 00-00. 2003 1 ¥‹ ¾Ý Effects of Silica Filler and Diluent on Material Properties of Non-Conductive Pastes and Thermal Cycling Reliability of Flip Chip Assembly Kyung-Woon Jang, Woon-Seong Kwon, Myung-Jin Yim* and Kyung-Wook Paik Dept. of Materials Science and Engineering, KAIST 373-1, Kusong-dong, Yusong-gu, Taejon 305-701, Korea *ACA/F Dept., Telephus, Inc. 25-11, Jang-dong, Yusong-gu, Taejon 305-343, Korea Abstract: In this paper, thermo-mechanical and rheological properties of NCPs (Non-Conductive Pastes) depending on silica filler contents and diluent contents were investigated. And then, thermal cycling (T/C) reliability of flip chip assembly using selected NCPs was verified. As the silica filler content increased, thermo-mechanical properties of NCPs were changed. The higher the silica filler content was added, glass transition temperature (T g ) and storage modulus at room temperature became higher. While, coefficient of thermal expansion (CTE) decreased. On the other hand, rheological properties of NCPs were significantly affected by diluent content. As the diluent content increased, viscosity of NCP decreased and thixotropic index increased. However, the addition of diluent deteriorated thermo-mechanical properties such as modulus, CTE, and T g . Based on these results, three candidates of NCPs with various silica filler and diluent contents were selected as adhesives for reliability test of flip chip assemblies. T/ C reliability test was performed by measuring changes of NCP bump connection resistance. Results showed that flip chip assembly using NCP with lower CTE and higher modulus exhibited better T/C reliability behavior because of reduced shear strain in NCP adhesive layer. Keywords: 1. Introduction As electronic packaging technology trends move toward lower cost, fine pitch, higher electrical per- formance and better reliability, flip chip technology gains popularity as one of the best chip packaging candidates to meet these trends. Although flip chip assembly using solder balls is in the main stream of flip chip technology, flip chip assemblies using polymer conductive adhesives such as isotropic conductive adhesives (ICAs), anisotropic conductive films (ACFs), and non-conductive pastes (NCPs) have been under development because of their potential advantages compared with solder flip chip assemblies such as lower processing tempera- ture, lower cost due to fewer assembly processing steps, and cheaper bumping method, and green proc- ess (no lead, no flux, and no cleaning solvent). Among these conductive adhesive flip chip tech- nologies, flip chip with NCPs and gold stud bumps is one of the promising method for certain applica- tions. Therefore, it is necessary to investigate thermo- mechanical properties and rheology of NCPs. The thermo-mechanical properties such as modulus, CTE, and T g are important for good flip chip assembly reliability, and rheological properties such as viscos- ity and thixotropy are important for good NCPs dis- pensability. It is previously observed that flip chip adhesives on organic substrates fails during the thermal cycling test mainly due to high CTE of adhesive layer 1) . Therefore, silica (SiO 2 ) fillers are added to reduce CTE for good T/C reliability. However, NCP’s viscos- ity increases as silica filler content increases resulting in a poor dispensability. To solve dispensability problem, diluent is added.