高強度リードフレーム材の開発

概要

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As the increment of ICs integration, the packages such as T-SOP and T-QFP are getting smaller and thinner. Consequently, the lead frame strips are required thinner in thickness, higher strength and higher heat discipation performance.The two types of high strength lead frames are developed as follows:1. Fe-40%Ni-3%Nb alloyThis alloy strip has high strength (i.e. Vickers hardness of 275 and tensile strength of 90kgf/mm2) and almost the same thermal expansion coefficient as the conventional 42%Ni-Fe alloy. Optimization of the strip production process makes the lead frame isotropic in mechanical properties (i.e, Youngs modulus E and threshold value of spring Kb) and lower residual stress by slitting.2. Copper double overlay clad strip alloyCopper strips are cladded on the both surfaces of precipitation hardened Invar alloy (Fe-38.5%Ni-5%Co-2.5%Ti). The clad strip can be produced to 0.15mm in total thickness which has the 0.015mm thick copper layer in each side. The copper double overlay clad strip has very high tensile strength of 126kgf/mm2 and 4.6% elongation. Thermal dicipation of the clad strip is expected two times larger than that of 42Ni alloy. In addtion, the clad strip seems to be superior to 42Ni alloy in the capability of soldering and plating due to the surface copper layers.
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