quasi static testing ultimate solution for cost effective quality verification and esd analysis of...
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Quasi Static Testing Ultimate Solution for Cost Effective Quality Verification and ESD Analysis of GMR Heads
Henry Patland
Wade Ogle
2192 Bering DriveSan Jose, CA 95131
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Welcome to Complex World of GMR Head
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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?
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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?
GMR Manufacturing Process
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Basics of Quasi-Static TestingThe 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
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QST Testing as a Concept
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.
Quasi Static Testing can characterize the GMR performance,
with the following advantages over DET Testing:
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QST Transfer CurveResistance
Amplitude
Asymmetry
Barkh Jump
Hysteresis
Bias Point
Delta R/R
Bias Angle
Slope
Max Slope
Parametrics extracted from QST Transfer Curve
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Common Anomalies which cause errors in a drive
Amplitude variation
Asymmetry
Baseline anomalies
Single Bit Jumps (Kinks)
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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
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Amplitude/Asymmetry Variation
-2000
-1500
-1000
-500
0
500
1000
1500
2000
-200 -150 -100 -50 0 50 100 150 200
Transverse Transfer C u rveB ia s : 4 .5 P a r t ID : A 2 0 - 1 8 H e a d : F a rH d 0
Am
plit
ud
e (
uV
)
M agnetic F ield (O e)
Forward Reverse
Poor Amplitude
High Asymmetry
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Base Line Shift / Popping
-3000
-2000
-1000
0
1000
2000
3000
-300 -250 -200 -150 -100 -50 0 50 100 150 200 250 300
Transverse Transfer C u rve B ia s : 3 .9 7 8 P a r t ID : H e a d : 2
Am
plit
ud
e (
uV
)
M agnetic F ield (O e)
Forward Reverse
Large Hysteresis
Barkhausen Jump
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Field Induced Instabilities
-2000
-1500
-1000
-500
0
500
1000
1500
2000
-200 -150 -100 -50 0 50 100 150 200
Transverse Transfer C u rveB ia s : 4 .5 P a r t ID : A 2 0 - 2 0 H e a d : F a rH d 0
Am
plit
ud
e (
uV
)
M agnetic F ield (O e)
Forward Reverse
314.0
73.398.7
124.1149.5
174.9200.2
225.6
251
276.4
301.8
Thre
shol
d (u
V)
0
100
200
300
400
500
Po
pc
orn
Co
un
t
-100-90-80-70
-60-50
-40-30
-20-10
0
10
20
30
40
50
60
70
8090
100
F ield (Oe)
Popc orn T es t
Kink / Max Slope
Field Instability at 40 Oe
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Reader Induced InstabilitiesReader Instability
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Writer Induced InstabilitiesWriter Induced Instabilities
(Popcorn)
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ESD Soft / Hard Damage
Amplitude and
Asymmetry Degradation
Pin-Layer Reversal
No Amplitude – Hard Damage
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Drive Anomaly Correlation
-3000
-2000
-1000
0
1000
2000
3000
-300 -250 -200 -150 -100 -50 0 50 100 150 200 250 300
Transverse Transfer C u rve B ia s : 3 .9 7 8 P a r t ID : H e a d : 2
Am
plit
ud
e (
uV
)M agnetic F ield (O e)
Forward Reverse
Amplitude variation in Drive caused by High Hysteresis shown in Transfer Curve
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QST to DET CorrelationTest conditions QST-2002
Sweep: 275 Oe Measured at 250 Oe Bias Current: 5 mA
Guzik 1001 + 1701 Frequency: 5 MHz Filter: 60 MHz Bias Current: 5 mA RPM: 5400
Amplitude Correlation (Stack Level)
R2 = 0.9325
-500
0
500
1000
1500
2000
2500
0 500 1000 1500 2000 2500
QST PP AMP
Guz
ik L
F A
mpl
itude
,nor
m fo
r C
urre
nt S
ensi
ng P
ream
p, u
V
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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
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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
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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
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QST can characterize ESD damage by applying a controlled ESD events to GMR head
HBM: 10% Resistance Change
Sensor Damage
CDM: 100% Resistance Change
Multiple distributed melting points
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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!
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By Applying Varying Amplitude ESD Events to GMR Head, QST can easily determine heads Failure points
Amp Failure
Pin Reversal
Resistance Failure
Meltdown
Asymmetry
Failure
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Direct-CDM SweepCDM Failure
Threshold at 5V
Partial Damage
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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
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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
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Acknowledgements
Al Wallash – Quantum/Maxtor Mark Nichols – Quantum/Maxtor Jenny Himle - Maxtor