Semiconductor packaging technology has been moving toward much more miniaturization, lighter weight and higher density. Flip Chip packaging is therefore becoming the key technology for next generation devices. The technology has been requiring much finer interconnection between the semiconductor chip and the package substrate, much narrower circuit width on the substrate and a much smaller through-hole diameter. To meet these demands a novel type of substrate material, "LaZ", for semiconductor package has been developed. Much more focus was placed on the thermal expansion at the thickness direction on the substrate, because lower thermal expansion was expected to lead to higher reliability of the substrate. In this paper the reason why higher reliability is accomplished by the use of "LaZ" is demonstrated, and other features of this material, such as environmental friendship, flame retardance and thermal resistance are also described.
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