In recent years, the study of Chip on Board (COB) structures with LSI chips mounted on the substrate has attracted much attention. One of the main technical problems is that the internal electrical wires may disconnect during the heat cycle process due to the differences in the thermal expansion coefficients between component materials. In order to prevent thermal expansion deformation the wires are encased in resin. Until now, the relationship between the physical properties of the resin and the thermal residual stress in the wires has been seldom reported.
In this work, the influence of resin physical properties on the thermal residual stress generated during the heat cycle process was theoretically analyzed via finite element analysis. The results show that the thermal residual stress generated in the wire during the heating process is larger than that during the cooling process. During heating the thermal residual stress was influenced by the storage modulus of the rubbery state (E_R).

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Glass-fiber (GF) reinforced thermoplastics are important industrial materials. Since the main purpose of using GF is to reinforce plastics, many attempts have been made to improve the interfacial strength between polymer and GF and to prevent fiber breakage. Elastomers and polymer blends are often used to improve the mechanical properties of GF reinforced thermoplastics although few works are reported. Our research focused on the investigation of the influence of GF and compatibilizers on the mechanical properties and morphology of polymer blends of PP and PA 66. In this study, we found that PA 66, which has a higher affinity for GF than for PP migrates to the GF interface. The heat distortion temperature (HDT) of this reinforced blend is significantly higher than that of GF-PP. The HDT of GF-PP/PA 66 blend is over 200°C, which exceeds the Tm (melting temperature) of neat PP. For high GF loadings, the interface compatibilized structure is easily formed by adding a small quantity of PA 66. The HDT is controlled by the heat resistance of a small quantity of polymer resin that forms a continuous phase. In carbon fiber composites, a continuous phase including the CF can be used by introducing PA66. This material has good electrical conductivity.

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