1. Quasi Static Testing
Ultimate Solution for Cost Effective Quality Verification and ESD Analysis of GMR Heads
Henry Patland
Wade Ogle
2192 Bering Drive
San Jose, CA 95131

2. Welcome to Complex World of GMR Head

3. Manufacturing GMR heads with good Yield, Reliability and Cost
GMR is a new complex technology requiring new manufacturing and test methodology
GMR technology provides huge advances in Arial Density
GMR is the most ESD sensitive mass produced device in the world
Is There an ultimate test solution for manufacturing GMR heads with good Yield, Reliability and Cost?

4. GMR Manufacturing Process
WAFER
(Semiconductor Process, Test)
ROW/BAR
(Wafer Slicing, Row Level Lapping, Test)
SLIDER
(Row Dicing, Slider Level Lapping, Test)
HGA
(Assy from Sliders, Suspension, FCBA’s, Test)
HSA
(Assy from HGA’s, Actuator, VC, FCBA’s, Preamp Chip, Test)
HDA
(Assy from HSA’s, Media, Enclosures, Drive PCB, Servo,Test)
How many places in your manufacturing process can GMR elements get damaged?

5. Basics of Quasi-Static Testing
The roots of QST are derived from actual drive operation
As GMR passes over a disk it is introduced to a variety of magnetic field.
In simplest terms the resistance of the GMR is dependent on the magnetic field applied to it.
In ideal case the relationship of GMR resistance to applied field is linear, but we don’t live in ideal world.
Close To Ideal Transfer Curve

6. QST Testing as a Concept
Quasi Static Testing can characterize the GMR performance,
with the following advantages over DET Testing:
Independent of external influence (disk variation)
Significantly more flexible, with the ability to subject the GMR to any variety of operating conditions.
Can analyze pure GMR performance with higher resolution than DET Testing.
Reduced Risk of Handling or Tester damaging heads
QST Testing is inexpensive, fast, relatively simple, and requires significantly lower maintenance and operating costs compared to DET Testing.

7. QST Transfer Curve Resistance Amplitude Asymmetry Barkh Jump
Hysteresis
Bias Point
Delta R/R
Bias Angle
Slope
Max Slope
Parametrics extracted from QST Transfer Curve

8. Common Anomalies which cause errors in a drive
Baseline anomalies
Single Bit Jumps (Kinks)
Amplitude variation
Asymmetry

9. Can QST screen out these Anomalies?
Amplitude / Asymmetry Variation
Baseline Shift / Popping
Field Induced Instabilities (Kinks)
Reader Induced Instabilities
Writer Induced Instabilities
ESD Soft/Hard Damage (Amplitude, Pin-Reversal, Asymmetry)
DET/Drive Correlation

10. Amplitude/Asymmetry Variation
Poor Amplitude
High Asymmetry

11. Base Line Shift / Popping
Barkhausen Jump
Large Hysteresis

12. Field Induced Instabilities
Field Instability at 40 Oe
Kink / Max Slope

13. Reader Induced Instabilities
Reader Instability

14. Writer Induced Instabilities
(Popcorn)

15. ESD Soft / Hard Damage Amplitude and Asymmetry Degradation
No Amplitude – Hard Damage
Pin-Layer Reversal

16. Drive Anomaly Correlation
Amplitude variation in Drive caused by High Hysteresis shown in Transfer Curve

17. QST to DET Correlation Test conditions QST-2002 Guzik 1001 + 1701
Sweep: 275 Oe
Measured at 250 Oe
Bias Current: 5 mA
Guzik
Frequency: 5 MHz
Filter: 60 MHz
RPM: 5400

18. The Answer is YES, QST can screen out most common Anomalies!
Drive Anomaly
QST Function
Amplitude/Asymmetry Variation
Transfer Curve Amplitude/Asymmetry
Baseline Shift / Popping
Transfer Curve Barkhausen Jump and Hysteresis
Field Induced Instabilities (Kinks)
Transfer Curve Max Slope and Field Induced Noise Test
Writer/Reader Induced Instabilities
Writer/Reader Induced Noise Test
ESD Damage (Amp, Pin-Reversal, Asymmetry)
Transfer Curve Amp, Asymmetry and Slope
DET/ Drive Correlation
YES

19. Additional Functionality of QST Testers
Static Tests of HSA components including Preamp Chip, Voice Coil, FCBA, Writer
Elevated Temperature Testing
PZT Suspension Testing
ESD Failure Threshold Testing

20. ESD Damage to GMR heads is considered one of the worst problems in Manufacturing Today
Due to sensitivity to ESD, GMR heads can be easily damaged or destroyed by the slightest ESD event caused by Humans or Machines in Manufacturing
Unfortunately, this problem is here to stay and will only get worse in near future as the ESD Failure Voltage level is inversely proportional to Arial Density
CDM (Charged Device Model) is rapidly becoming the standard for characterizing GMR head ESD Failure Thresholds

21. QST can characterize ESD damage by applying a controlled ESD events to GMR head
HBM: 10% Resistance Change
Sensor Damage
HBM
CDM: 100% Resistance Change
Multiple distributed melting points
CDM

22. What can be done about GMR head ESD Sensitivity ?
Improved design of GMR head which is less sensitive to ESD
Eliminate ESD events from Manufacturing
Monitor GMR head performance after every significant process to isolate and eliminate ESD events in Manufacturing
As Al Wallash – Maxtor would put it:
“Don’t loose your head over ESD”
Whatever you do, QST Testing can Help!

23. By Applying Varying Amplitude ESD Events to GMR Head, QST can easily determine heads Failure points
Resistance Failure
Meltdown
Amp Failure
Pin Reversal
Asymmetry
Failure

24. CDM Failure Threshold at 5V
Direct-CDM Sweep
CDM Failure Threshold at 5V
Partial Damage

25. QST is the Ultimate Test Solution for GMR head manufacturing
QST Testing Methodology can be applied from Wafer to HDA level testing
QST Testing can screen out bad heads early in manufacturing process
QST Testing can identify which processes in Manufacturing are ESDing your heads
QST Testing is fast and inexpensive
QST Testing can be done with None or Very Little Handling on many test levels
QST surpasses DET in analyzing pure GMR performance

26. References
[1] J.Himle, R.Cross, M.Greenwell, “Drive-Level Instabilities Correlated to Quasi-Static Field Testing”, MMM-Intermag 2001
[2] C. Moore, “A Comparison of Quasi-Static Characteristics and Failure Signatures of GMR Heads subjected to CDM and HBM ESD Events”
[3] Integral Solutions Int’l, “Quasi 97” and “QST-2002” Tester

27. Acknowledgements Al Wallash – Quantum/Maxtor
Mark Nichols – Quantum/Maxtor
Jenny Himle - Maxtor