Disk drive to reduce head instability

1. A disk drive to reduce head instability during disk drive manufacturing, the disk drive comprising:

a disk;

a dynamic flying height (DFH) read/write head;

a flying height actuator to control the spacing between the DFH read/write head and the disk;

a touch distance sensor to measure a spacing signal between the DFH read/write head and the disk; and

a controller for controlling operations in the disk drive including: applying a sloped increasing power between a first voltage and a second voltage to move the DFH read/write head towards the disk; receiving the spacing signal from the touch distance sensor; determining if the DFH head is approaching touchdown based on the spacing signal, and if not, applying a second sloped increasing power between the second voltage and a third voltage;

wherein, if at the third voltage, the DFH head is determined to be approaching touchdown based upon the spacing signal, a touchdown calibration value for the DFH read/write head to avoid head-disk interaction is set at the second voltage.

2. The disk drive of claim 1 , wherein the controller further controls operations including applying a sloped decreasing power between the third voltage and the second voltage.

3. The disk drive of claim 2 , wherein the sloped decreasing power level is determined by a thermal expansion rate of a heater and a cooling effect of an air bearing coupled to the DFH read/write head.

4. The disk drive of claim 1 , wherein the touchdown calibration value for the DFH read/write head is saved in a non-volatile memory.

5. The disk drive of claim 1 , wherein the flying height actuator to control the spacing between the DFH read/write head and the disk includes a thermal actuator comprising a heater.

6. The disk drive of claim 1 , wherein the sloped increasing power level is determined by a thermal expansion rate of a heater and a cooling effect of an air bearing coupled to the DFH read/write head.

7. The disk drive of claim 1 , wherein the controller further controls operations including applying steep sloped increasing power, curved sloped increasing power, level power, curved sloped decreasing power, and sloped decreasing power to the flying height actuator.

8. The disk drive of claim 1 , wherein the second voltage is based on a touchdown calibration value stored in a non-volatile memory.

9. A method to reduce head instability during disk drive manufacturing, the method comprising:

controlling the spacing between a dynamic flying height (DFH) read/write head and a disk;

measuring a spacing signal between the DFH read/write head and the disk from a touch distance sensor;

applying a sloped increasing power between a first voltage and a second voltage to the DFH read/write head to move the DFH read/write head towards the disk;

determining if the DFH head is approaching touchdown based on the spacing signal, and if not,

applying a second sloped increasing power between the second voltage and a third voltage, wherein, if at the third voltage, the DFH head is determined to be approaching touchdown based upon the spacing signal, a touchdown calibration value for the DFH read/write head to avoid head-disk interaction is set at the second voltage.

10. The method of claim 9 , further comprising applying a sloped decreasing power between the third voltage and the second voltage.

11. The method of claim 10 , wherein the sloped decreasing power level is determined by a thermal expansion rate of a heater and a cooling effect of an air bearing coupled to the DFH read/write head.

12. The method of claim 9 , wherein the touchdown calibration value for the DFH read/write head is saved in a non-volatile memory.

13. The method of claim 9 , wherein the flying height actuator to control the spacing between the DFH read/write head and the disk includes a thermal actuator comprising a heater.

14. The method of claim 9 , wherein the sloped increasing power level is determined by a thermal expansion rate of a heater and a cooling effect of an air bearing coupled to the DFH read/write head.

15. The method of claim 9 , further comprising:

applying steep sloped increasing power to the DFH read/write head;

applying curved sloped increasing power to the DFH read/write head;

applying level power to the DFH read/write head;

applying curved sloped decreasing power to the DFH read/write head; and

applying sloped decreasing power to the DFH read/write head.

16. The method of claim 9 , wherein the second voltage is based on a touchdown calibration value stored in a non-volatile memory.