3 Manufacturing GMR heads with good Yield, Reliability and Cost GMR is a new complex technology requiring new manufacturing and test methodologyGMR technology provides huge advances in Arial DensityGMR is the most ESD sensitive mass produced device in the worldIs 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 operationAs 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 headsQST 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 HysteresisBias PointDelta R/RBias AngleSlopeMax SlopeParametrics extracted from QST Transfer Curve
8 Common Anomalies which cause errors in a drive Baseline anomaliesSingle Bit Jumps (Kinks)Amplitude variationAsymmetry
9 Can QST screen out these Anomalies? Amplitude / Asymmetry VariationBaseline Shift / PoppingField Induced Instabilities (Kinks)Reader Induced InstabilitiesWriter Induced InstabilitiesESD Soft/Hard Damage (Amplitude, Pin-Reversal, Asymmetry)DET/Drive Correlation
15 ESD Soft / Hard Damage Amplitude and Asymmetry Degradation No Amplitude – Hard DamagePin-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 OeMeasured at 250 OeBias Current: 5 mAGuzikFrequency: 5 MHzFilter: 60 MHzRPM: 5400
18 The Answer is YES, QST can screen out most common Anomalies! Drive AnomalyQST FunctionAmplitude/Asymmetry VariationTransfer Curve Amplitude/AsymmetryBaseline Shift / PoppingTransfer Curve Barkhausen Jump and HysteresisField Induced Instabilities (Kinks)Transfer Curve Max Slope and Field Induced Noise TestWriter/Reader Induced InstabilitiesWriter/Reader Induced Noise TestESD Damage (Amp, Pin-Reversal, Asymmetry)Transfer Curve Amp, Asymmetry and SlopeDET/ Drive CorrelationYES
19 Additional Functionality of QST Testers Static Tests of HSA components including Preamp Chip, Voice Coil, FCBA, WriterElevated Temperature TestingPZT Suspension TestingESD 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 ManufacturingUnfortunately, 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 DensityCDM (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 ChangeSensor DamageHBMCDM: 100% Resistance ChangeMultiple distributed melting pointsCDM
22 What can be done about GMR head ESD Sensitivity ? Improved design of GMR head which is less sensitive to ESDEliminate ESD events from ManufacturingMonitor GMR head performance after every significant process to isolate and eliminate ESD events in ManufacturingAs 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 FailureMeltdownAmp FailurePin ReversalAsymmetryFailure
24 CDM Failure Threshold at 5V Direct-CDM SweepCDM Failure Threshold at 5VPartial Damage
25 QST is the Ultimate Test Solution for GMR head manufacturing QST Testing Methodology can be applied from Wafer to HDA level testingQST Testing can screen out bad heads early in manufacturing processQST Testing can identify which processes in Manufacturing are ESDing your headsQST Testing is fast and inexpensiveQST Testing can be done with None or Very Little Handling on many test levelsQST surpasses DET in analyzing pure GMR performance
26 References J.Himle, R.Cross, M.Greenwell, “Drive-Level Instabilities Correlated to Quasi-Static Field Testing”, MMM-Intermag 2001 C. Moore, “A Comparison of Quasi-Static Characteristics and Failure Signatures of GMR Heads subjected to CDM and HBM ESD Events” Integral Solutions Int’l, “Quasi 97” and “QST-2002” Tester
27 Acknowledgements Al Wallash – Quantum/Maxtor Mark Nichols – Quantum/MaxtorJenny Himle - Maxtor