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Among many factors that influence the reliability of a flip-chip assembly using NCF interconnections, the most effective parameters are often the coefficient of thermal expansion (CTE), the modulus (E), and the glass transition temperatures (Tg). Of these factors, the effect of Tg on thermal deformation and device reliability is significant; however, it has not been shown clearly what effect Tg has on the reliability of NCF. The Tg of a conventional NCF material is approximately 110°C. In this study, a new high Tg NCF material that has a 140oC Tg is proposed. The thermal behaviors of the conventional and new NCFs between -40oC to 150oC are observed using an optical method. Twyman-Green interferometry and the moiré interferometry method are used to measure the thermal micro-deformations. The Twyman-Green interferometry measurement technique is applied to verify the stress-free state. The stress-free temperatures of the conventional and new Tg NCF materials are approximately 100oC and 120oC respectively. A shear strain at a part of the NCF chip edge is measured by moiré interferometry. Additionally, a method to accurately measure the residual warpage and shear strain at room temperature is proposed. Through the analysis of the relationship between the warpage and the shear strain, the effect of the high-Tg NCF material on the reliability is studied.

In this paper, structural integrity evaluation of reactor pressure vessel bottom head without penetration nozzles in core melting accident has been performed. Considering the analysis results of thermal load, weight of molten core debris and internal pressure, thermal load is the most significant factor in reactor vessel bottom head. The failure probability was evaluated according to the established failure criteria and the evaluation showed that the equivalent plastic strain results are lower than critical strain failure criteria. Thermal-structural coupled analyses show that the existence of elastic zone with a lower stress than yield strength is in the middle of bottom head thickness. As a result of analysis, the elastic zone became narrow and moved to the internal wall as the internal pressure increases, and it is evaluated that the structural integrity of reactor vessel is maintained under core melting accident.

In this paper, we investigated the degradation mechanism and the reliability behaviors of flip chip joint using Anisotropic Conductive Adhesives (ACAs) and Au bumped chip under high current density. The current carrying capability and current stressing reliability of flip chip assembly using three different types of ACAs were performed to investigate the effect of thermal conductivity of ACA and the conductive particle type on the current carrying capability and current stressing reliability of ACA flip chip joints.For the ACA materials, we prepared two conventional ACAs with different conductive fillers, which are thermally non-conductive, and one thermally conductive ACA. For the conductive fillers, we incorporated Au coated polymer balls and metallic Ni balls in 5 µm diameter. For the thermally conductive ACA materials, we incorporated thermally conductive fillers of silicon carbide with less than 1 µm diameter in the conventional ACA formulation. The thermal conductivity and thermo-mechanical properties of three ACAs such as thermal conductivity, cure behavior, coefficient of thermal expansion (CTE) were measured in comparison.The current carrying capabilities and current stressing reliabilities of flip chip joints using ACAs with different conductive filler type, thermal conductivity and physical properties were investigated. The current carrying capability and electrical reliability of flip chip joints using enhanced thermally conductive ACAs were improved due to high thermal conductivity. The failure analysis including crosssection SEM works shows that the interface degradation and adhesive swelling are main degradation mechanism of the high current density interconnection of flip chip assembly using conventional ACA, in which high junction temperature enhance such thermally induced degradation mechanism. The improved current carrying capability and current stressing reliability of flip chip assembly using thermally conductive ACAs were due to reduced interface and adhesive degradation through easy heat dissipation of adhesive that bring slow down of thermally induced degradation mechanism. There were no degradations of ACA flip chip joints using Ni-filled ACA and Au-coated polymer-filled ACA up to 200 hrs under 3.0 A current stress.

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