The mechanism and characteristics of aluminum whisker generation were studied by using pure-aluminum (pure-Al) thin film sputter-deposited on glass substrate. The experiments revealed that whisker generation is accelerated at thermal stress temperatures above 270 degrees C as the exposure time at the maximum temperature becomes longer. and that the potential for whisker generation increases as the margin between the deposition and the thermal stress temperatures is increased. Plan-view TEM and electron diffraction analyses of whiskers also revealed that an Al film with a large proportion of (111) texture shows strong resistance to whisker generation, and that no whiskers grow from the (111)-oriented grain.