Quasi Static Testing Advanced Quasi-Static Testing Technology and Applications

Henry Patland

2192 Bering DriveSan Jose, CA 95131hpatland@us-isi.com

www.us-isi.com

Topics

Introduction to Quasi-Static Testing

Advanced Quasi-Static Testing Technology

Quasi-Static Testing Applications

QST Testing as a Concept

Independent of external influence (disk/flying height variation)

Significantly more flexible, with the ability to subject the GMR/TMR to any variety of ambient conditions.

Can analyze pure GMR/TMR 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.

Quasi Static Testing can characterize the GMR/TMR performance, with the following advantages over DET Testing:

Basics of Quasi-Static TestingThe roots of QST are derived from actual drive operation

As GMR/TMR passes over a disk it is introduced to a variety of magnetic field.

In simplest terms the resistance of the GMR/TMR is dependent on the magnetic field applied to it.

In ideal case the relationship of GMR/TMR resistance to applied field is linear, but we don’t live in ideal world.

Close To Ideal Transfer Curve

Transverse Transfer CurveResistance

Amplitude

Asymmetry

Barkh Jump

Hysteresis

Bias Point

Delta R/R

Bias Angle

Slope

Max Slope

Parametrics extracted from QST Transfer Curve

DC MeasurementsMeasures head resistance change versus an externally applied magnetic field through a low frequency channel. The following DC tests can be performed.

Transfer curve Stability Bias angle Asymmetry sweep Resistance delta Quasi-Static test

Static Tests (HSA / HDA)Verification of the Preamp Chip, Flex, and Voice Coil assembly can be performed.

Voice coil measurements Fault detection Current consumption Pin-Pin and Pin-Ground shorts Temperature Sensor control Passive component measurements RDX / RDY offset voltage

AC MeasurementsMeasures high frequency noise as influenced by write excitation, field excitation, or combinations of both. The following AC tests can be performed

Popcorn Noise W/R Recovery Field Induced Noise Characterization Frequency Response

AC Channel Technology

Glitch After Write (Popcorn) Field Induced Instabilities (Noise) Spectral Analysis (FFT) 200 Mhz Analog Bandwidth 160 Mhz 10-bit digitizer Low Noise W/R Recovery < 500 ns 400 Mhz Write Frequency

Write Induced InstabilitiesWriter Induced Instabilities

(Popcorn)

Field Induced InstabilitySoft Kink at 160 Oe

Field Induced Instability @ 150 Oe

Field Induced Instability @160 Oe

Field Induced Instability @ 170 Oe

Spectral Maximum Amplitude Noise

Noise RMS (uV)

Noise Amp (uV)

Max Noise Amp (uV)

S.M.A.N

Digitizer is The Key to S.M.A.N.

Qualifies Three Types of Instability Events in One Shot

RMS Noise for broadband noise Max Amp for rare events such as Barkh.

Jumps and Write Induced Instability Amp Noise for high probability noise

Transfer Curve & S.M.A.N.Soft Kink and Max Noise at

160 Oe

Applications for QST Testing

Bar, Slider Testing HGA, HSA, HDA Testing ESD Tolerance Testing Thermal Reliability Testing

Row/Slider Level Testing

Benefits of Row/Slider Testing

Early look at Wafer process for QST Parametrics and Instability

Upstream testing reduces scrap cost Bar to 4000 Sliders/Hour Slider to 1200 Sliders/Hour

HGA, HSA, HDA Level Testing

Benefits of HGA, HSA, HDA Testing

Process Control Simple Test/Tooling Failure Analysis at HDA level HSA Screening Prior to Drive Build HDA Screening After Servo Write

ESD Tolerance Measurement And Process Mapping

ESD Tolerance: Repetitive “Inject and Test” HBM, MM and DCDM

CDM (Charged Device Model) is rapidly becoming the standard for characterizing GMR/TMR head ESD Failure Thresholds

Process Mapping: Test After Each Process Including Bar, Slider, HGA (Before/After DET), HSA Prior to Final Bond and HDA After Merge and After Servo Write

Symptoms: First Failure Mode: Instability, then Parametrics

D-CDM Cartridge Assembly

ESD/CDM Pulse System

CDM Tolerance Characterization

QST can characterize ESD damage by applying controlled ESD events to GMR head

CDM: 100% Resistance Change

Multiple distributed melting points

HBM: 10% Resistance Change

Sensor Damage

What can be done about GMR/TMR head ESD Sensitivity ?

Improved design of GMR/TMR head which is less sensitive to ESD

Eliminate ESD events from Manufacturing Monitor GMR/TMR 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!

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

DCDM Sweep

50010001500

40

50

60

0.5

1.0

40

50

60

80

100

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0

E SD P ro file C u rveB ia s : 5 .0 P a r t ID : H e a d : F a rH d 0

Amp

At T

est (

µV)A

VGR

es

ista

nc

e (

Oh

ms

)AV

GP

opco

rnA

VG

Noi

se A

mp

(µV)

MAX

Ma

x N

ois

e A

mp

(µ

V)M

AX

E P S -DCDM E S D (V )

P OS NE G

-2500

-2000

-1500

-1000

-500

0

500

1000

1500

-150 -100 -50 0 50 100 150

Transverse Transfer C u rveB ia s : 5 .0 P a r t ID : P a r tID H e a d : F a rH d 0

Am

plit

ud

e (

uV

)

M agnetic F ield (O e)

Reverse

-1000

-750

-500

-250

0

250

500

750

1000

0.0 2.5 5.0 7.5 10.0 12.5 15.0

P o pco rn P u lsesS ub T itle

Am

plit

ud

e (

uV

)

Tim e (uS )

519-1 520-1 523-3 524-2 525-2 526-1 527-1

528-4 530-2 531-1 532-3 533-4 534-4 535-6

25

50

75

100

125

150

175

-150 -100 -50 0 50 100 150

Spectral M axim u m Am plitu de N o ise P lo tP a r t ID : P a r tID H e a d : 0

No

ise

Am

plit

ud

e (

µV

)

F ield (Oe)

Noise A m p M ax Noise A m p

CDM Failure Threshold at 3.5V 25% lower than Amp

Failure at 5V

Thermal Reliability Testing

Accelerated Life Testing at Row Level

Accelerated Life Testing at HGA Level

Accelerated Life Testing at Row Level

Accelerated Life Test @ 5.5 Days

Resistance and Amplitude Deteriorating after 5.5 Days of elevated temperature (100C) and elevated VBias

HGA Level Accelerated Life Test

Up to 8 simultaneous HGA testing

Temperature Test

Transfer Curve

Parametrics vs. Temperature

Benefits of Thermal Reliability Testing

Accelerated Life Testing Can Predict Failures Before They Occur

Row Level Testing Provides Early Look at Thermal Reliability

Conclusion

Don’t loose your head over

ESD, Instability or Reliability

Whatever you do, QST Testing can Help!

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] H. Patland, W. Ogle, “High Frequency Instabilities in GMR Heads Due to Metal-To-Metal Contact ESD Transients”, EOS/ESD Symposium 2002

[4] Integral Solutions Int’l, “Quasi 97” and “QST-2002” Tester

Acknowledgements

Al Wallash –Maxtor Mark Nichols –Maxtor