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Head position of de-pop actuator for test yield improvement Disclosure Number: IPCOM000013581D
Original Publication Date: 2001-Apr-22
Included in the Prior Art Database: 2003-Jun-18

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The idea is how to decide head positions for de-pop actuator, for test yield improvement. As TPI gets higher, actuator flutter becomes one of the major causes of track following error, because that can't be controlled by servo controller. Actuator flutter is caused by the wind generated by rotating disks. And the power of the wind between disks is higher than that between disk and cover, and between disk and base. Therefore track following error of heads between disks is worse(see graph.1a 1c). That means heads between disks have higher risk of MFG test fails cased by track following error. The idea of this invention is to select lower risk heads for de-pop actuator. For example, the actuator of 3 heads model has 3 heads and 1 dummyhead. In former products, we put 3 heads from base side in order and put a dummyhead at the arm nearest top cover. But in this examples, we put a dummyhead between disks for minimizing the number of heads between disks (see fig.1). By deciding head position like this, we can reduce the number of heads that have higher risk of MFG test fails. And then we can achieve better test yield. graph.1a : 4 heads actuator NRRO of track following error H1,H2 is between disks)