Power Durability of Al–W Alloy Electrodes Used in RF-Band Surface Acoustic Wave Filters

For the RF-band surface acoustic wave (SAW) filters, the power durability of Al–W alloy electrodes was studied. It was shown that the power durability of Al–0.5 at.% W alloy electrodes is superior to that of the Al–0.5 at.% Ti alloy electrodes which have been known as power-durable electrodes. The amount of hillocks decreases as the W content in the Al–W alloy increases, on the other hand, the lifetime of the electrodes is maximized at a W content of 0.5 at.%. These phenomena suggest that the whiskers, instead of hillocks, grown on the sides of the electrodes, cause the electrical short between the hot and the ground electrodes and suppress the lifetime increase.