Thermal fly height induced shield instability screening for magnetoresistive heads
View Patent ↗A method for testing magnetic heads formed on a wafer to detect the presence of thermal induced popcorn noise resulting from thermal fly height control. The method includes performing a quasi test on a magnetic head, the quasi test being performed over 400 or more cycles of magnetic field application. For additional test accuracy, the write head can be cycled while 400 or more cycles of magnetic field are generated.
1. A method for testing a magnetic head, comprising:
forming a magnetic head on a wafer the magnetic head including, a read head, a write head and a heater element;
placing the magnetic head into a testing tool;
activating the heater element; and
while activating the heater element, monitoring a signal from the read head while generating a series of magnetic fields in a vicinity of the read head, the series of magnetic fields including 400 or more magnetic field cycles.
2. A method as in claim 1 wherein the series of magnetic fields includes magnetic field having strength of 300-500 Oe.
3. A method as in claim 1 wherein the series of magnetic fields includes magnetic field having strength of 400 Oe.
4. A method as in claim 1 wherein further comprising applying a sense voltage of 100-150 mV to the read head.
5. A method as in claim 1 further comprising applying a sense voltage of about 125 mV to the read head.
6. A method as in claim 1 wherein the series of magnetic fields include about 512 magnetic field cycles.
7. A method as in claim 1 wherein the series of magnetic fields includes magnetic fields having a strength of 300-500 Oe, the method further comprising applying a sense voltage of 100-150 mV.
8. A method as in claim 1 wherein the series of magnetic fields includes magnetic fields having a strength of about 400 Oe, the method further comprising applying a sense voltage of about 125 mV.
9. A method as in claim 1 wherein the read head comprises a magnetoresistive sensor sandwiched between first and second magnetic shields.
10. A method as in claim 1 wherein the read head comprises a magnetoresistive sensor sandwiched between first and second magnetic shields, each of the first and second magnetic shields being constructed of NiFe.
11. A method for testing a magnetic head, comprising:
forming a magnetic head on a wafer the magnetic head including, a read head, a write head and a heater element;
placing the magnetic head into a testing tool;
activating the heater element;
activating the write head and while activating the heater element and write head, monitoring a signal from the read head while generating a series of magnetic fields in a vicinity of the read head, the series of magnetic fields including 400 or more magnetic field cycles.
12. A method as in claim 11 , wherein the activating the write head comprises activating the write head through a series of activation cycles.
13. A method as in claim 11 , wherein the activating the write head comprises activating the write through 400 or more activation cycles.
14. A method as in claim 11 , wherein the activating the write head comprises activating the write head though about 512 activation cycles.
15. A method as in claim 11 , wherein the activating the write head comprises activating the write head through a series of 400 or more activation cycles, the activation cycles including generating a current of 20-40 mA through the write head.
16. A method as in claim 11 , wherein the activating the write head comprises activating the write head through a series of 400 or more activation cycles, the activation cycles including generating a current of 20-40 mA through the write head, separated 5-15 microseconds of inhibited current.
17. A method as in claim 11 , wherein the activating the write head comprises activating the write head through a series of 400 or more activation cycles, the activation cycles including generating a current of 20-40 mA, at 30-50 MHz through the write head, each generation of current through the write head being separated by 5-15 microseconds of inhibited current.
18. A method as in claim 11 wherein the series of magnetic fields includes magnetic field having strength of 300-500 Oe.
19. A method as in claim 1 wherein the series of magnetic fields includes magnetic field having strength of 400 Oe.
20. A method as in claim 11 wherein the series of magnetic fields include about 512 magnetic field cycles.