PURPOSE: To obtain a substrate having good warpage by subjecting the substrates for information recording having an air sandwich structure to ultrasonic welding by using a horn and anvil having the steps corresponding to the difference in thickness between disk substrates in inside and outside circumferential parts and spacers.
CONSTITUTION: The steps ΔH, ΔA are provided on the horn 14 and the anvil 11 in such a manner that the differences in the total thickness of the outside circumferential part of the disk substrates 3a, 3b and the outside circumferential spacer 5 and the total thickness of the inside circumferential part of the substrates 3a, 3b and the inside circumferential spacer 6 coincide. The substrates 3a, 3b with the inside and outside circumferential spacers 6, 5 in-between are thereby subjected to the ultrasonic welding. The spacer 5 and the substrate 3a are first superposed and welded at this time. This substrate 3a and the substrate 3b on the opposite side are then superposed via the spacer 6 and the spacer 5 and the substrate 3b as well as the spacer 6 and the substrates 3a, 3b are simultaneously welded from one direction and are stuck together. Residual stresses are thereby decreased and the substrate having the good warpage is obtd.
KIMURA TOSHIO
KURISU MASAYOSHI
