Measurement And Reduction of Particulate Contamination in HDD

Transcription

1 Measurement And Reduction of Particulate Contamination in HDD Phil Lei Carl Newberg Chris Schreiber Magnecomp Precision Technology September,

2 Overview The effect of particles in Hard Disk Drives How clean is clean enough Metrology for monitoring cleanliness Realistic specifications Monitoring the right things How do we know the data is correct What other information can LPC data provide Will future LPC monitoring be in-sync with HDD technology advance 2

3 The effect of particles in Hard Disk Drives General They are mobile and transferable Variable size Most are easy to clean but some are very sticky Hard particles Scratch (complete damage) Hard error Soft particles Smear on media Soft error (re-writable) 3

4 How Clean Is Clean Enough? HDD Trends Emerging Recording Technologies Demand Enhanced Controls Robust Designs Interface, Components, HDD Process Higher Cleanliness Tighter Requirements, Controls, Metrology 4

5 Measurement Techniques Liquid Particle Counting (LPC) Extraction Method Varies By Customer Ultrasonic Power & DI water Power density, frequency, extraction time, etc. Dry Particle Counting SEM/EDS Tape Extraction Swab Extraction Other Extraction Techniques (non-hdd) Spray Extraction Non-ultrasonic liquid (swishing) Measurement Method Definition Calibration and Correlations Ultrasonic tank and LPC sensor Size of Particulate Differential counts vs. cumulative counts Particle Type Characterization Extraction Methods SEM/EDS Spectra 5

6 Particle Cleanliness Criteria Particle size 2.0um 0.6um/0.5um 0.3/0.2um Future trend? Particle Counts Differential counts Cumulative counts Per unit surface area Per part Particle Type Hard particles Semi-hard particles Soft particles Related to Particulate Erosive materials Corrosion induced Particulate 6

7 Realistic Specifications LPC Case #1: Different Cleanliness, Same Cleanability 4,000 3,000 2,000 Different Cleanliness Same Asymptote LPC Case #2: Different Cleanliness, Different Cleanability 4,000 3,000 2,000 Different Asymptote 1,000 1, X 2X 3X 4X 5X 1X 2X 3X 4X 5X 4,000 Case #3: Different Cleanliness, Different Cleanability 4,000 Case #4: Same Cleanliness, Different Cleanability 3,000 3,000 Reasonable Specification? LPC 2,000 LPC 2,000 1,000 1, X 2X 3X 4X 5X 0 1X 2X 3X 4X 5X 7

8 What Are You Really Monitoring? LPC Data is Dependant Upon Absolute Cleanliness of the Parts Samples Representative of Mfg. lots Sensor s Ability to Detect Particles (Machine) Resolution Calibration & Gage Uniform Test Procedure (Method) Sensor Calibration Minimize Human and Environmental Factors Sensor Calibration Extraction Power & Procedure 8

9 How Do You Know Your Data Is Correct? Particle size distribution cnts 1 size 3 log( cnts ) = k log( size) + b Where k is approximately -3. Abnormal! PMS: Beal et al. 9

10 What Else Can LPC Data Tell You? Base Material Property Variability Variations Between Raw Material Sources SST Melt & Re-Roll lots Dielectric Differences i.e. PI vs. Acrylic Coverlay Vendor Process Induced Variations Internal Processing Variations Other Unknown Process Factors Tooling Changes Particle Type Change Improper Handling & Transportation 10

11 Particle Type Categorization Hard particle type Silica, silicate, alumina, carbide, diamond, etc. Semi-hard particle type SST 3xx series, SST 4xx series, other Fe-based, etc. Other particles Fiber, talc, magnetic, etc. Media scratches, head damage, etc. Erasure, smear, minor scratches, etc. 11

12 Particle Extractions By Ultrasonic Power U/S Power 200 watts 300 watts 350 watts How much U/S power to use? What is the best U/S frequency? How long to extract? U/S Frequency 68 khz 132 khz 3-factor DOE Extraction Time 30 sec 60 sec 120 sec 12

13 Extraction Power, Time & Frequency Factor Multiple Extraction LPC: U/S Power Effect Frequency 132kHz 68k Hz LPC LOG/LOG Curve Slope sec 60sec 120sec U/S_Power 200W 300W 350W X 2X Frequency effect has the most significance! 3X 4X 5X LOG/LOG Curve Slope Frequency 132k Hz 68k Hz W 300W 350W 13

14 Extraction Time and Extraction Power 0.2um LPC (Differential Counts) 3,500 3,000 2,500 2,000 1,500 1, Extraction Power and Time Factor 200W 300W 350W 0 30 sec 60 sec 120 sec Extraction Time 14

15 Cleanliness Control Roadmap Customer Cleanliness Requirements Product/Tooling Robust Design for Better Cleanliness Reduced Handling Tooling Cleanliness Clean room Facility and Commodity Cleanliness R&D, Design Manufacturing Best-in-Class Methods Material Cleanliness Characteristics Qualifications Standardized Data Reporting Final Washing System Optimization Supplier Cleanliness Control (LPC spec for components) Final Products QA for Outgoing LPC Test Method Optimization Feedback from Customer Results 15

16 Future LPC Monitoring in HDD Smaller Than 0.2µm Particle Size? Lower counts More sophisticated particle segregation More complex analysis tool and procedure More comprehensive procedure Adoption of one unified HDD industry measurement procedure Uniform specification criteria based upon, for example asymptote 16

17 Summary New Recording Methods Require More Stringent Cleanliness Enhanced Focus on HPA & SST Particulate Current Test Methods Possess Erosive Background That Overlap Future Targets Attaining Effective Cleaning Without Altering the Delicate 0.1 degree Static Attitude and 0.02 Gram Sigmas, on Today s Products Pose Significant Challenges LPC Trends are Challenging the Metrology 17