Introduction of the collaborative activity of KT Method & TRIZ
to improve Hard Disk Drive’s Quality and Reliability

Kazushi Tsuwako
Hitachi Global Storage Technologies Japan, Ltd.
C&C HDD Advanced Platform Development

Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

1. Back Ground3.5”HDD is using an air spoiler to minimize the disk vibration.
②Air Flow

Top Cover

Air Spoiler①Disk Rotation③Disk・Vibration

Air Spoiler

DiskSpindle Motor

Basecast

3.5” HDD’s capacity increase required a bigger air spoiler.
But a bigger air spoiler increases serious data damage on the disk.
New product “J” which had a bigger air spoiler was required someactions to cover for the disk damage.
Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

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2. Air Spoiler’s Function and Issue

Comparison of Disk damage by contamination (Product “G” & “K”)
Air Spoiler Location

発生率No.of HE

No.of HE

発生率ODID

Product “G” Damage Area

Air Spoiler Location

ODID

Product “K” Damage Area

Most of all disk damage were under a air spoiler.
Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

33-1. Problem Analysis of OD Scratch 1/3

State the Problem
Identify the root cause of the data damage occurred on Outside Data Zone (OD)
area of new 3.5” HDD

What is wrong in the way
the object looks, sounds,
feels, smells

What is NOT wrong thistime, even though it isrelated, or was wrong, atother times

Distinction
Peculiarities anddifferences about the "IS"and "IS NOT" columns

Old 3.5” HDD

Areal Density Increase

New 2.5” HDD

Alminum Disk, Air Spoiler,Higher RPM

Scratch Increase @ODNo Scratch @ID

Higher RPM

Spiral Scratch @OD

Head Crush @OD

Head treads on
contamination @OD

OD & MD area

ID area

Higher relative speed

Under Actuator

Crosscurrent on thedisk

New 3.5” HDD

Surface with Air Spoiler
Under Air Spoiler

Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

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3-2. Problem Analysis of OD Scratch 2/3Distinction

New 3.5” HDD

Areal Density Increase

Just after POR

Contamination on disk

After Load/Unload

Easily trend on the bigContamination

5 fail out of 1,000 HDDs
Increase

Decrease

Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

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3-3. Problem Analysis of OD Scratch 3/3

Assumed Cause based on Distinction

Test by IS/IS Not

Sensitivity of Media against scratch is getting higher andhigher due to capacity increase. And the relative speed
between head and disk is highest at OD area.
The air spoiler create the crosscurrent (Karman voltex).
This crosscurrent accelerates nano-particle to accrete（ＭＰＣ？）
the disk.
(MPC?)
Some asperities remained on the disk. Some of themescaped from the disk MFG process, some of them weregenerated by Cobalt migration on the disk.

If higher recording density or asperity on the disk is root cause,they can not explain why many HE were under the air spoiler.
HE increased area depends on the air spoiler, but it does notdepend on the actuator. They are clearly conflicting.
Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

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4.1. Proposal of New Air Spoiler for Contamination Reduction - 1

Why an air spoiler accelerates accrete contamination to the disk?
Focused attention on Air Spoiler’s Shape Two-dimensional Fluid Analysis (ANSYS)

Disk Rotation Speed ： 30m/s （at 40mm from the center of Disk)
DiskDiskAir Spoiler
w/o Taper

Karman vortex

DiskAir Spoiler
w/ TaperDisk

An air spoiler without taper makes Karman voltex and accelerate toaccrete the contamination on the disk. But an air spoiler with taper
reduces Karman voltex and the contamination on the disk.
Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

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4.2. Proposal of New Air Spoiler for Contamination Reduction - 2Particle Injection Test to confirm the simulation result
 Air Spoiler used for Particle Injection Test
Air Spoiler

3 Disk Model

Air Spoiler (2Fin)

Top Cover

Cross Section①2 fin type

without Taper

D#3
D#2
D#1DiskBase②2 fin type
(Taper 2mm)with Taper
2mm

Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

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5. Qualification Result of Air Spoiler with Taper

Number of Contamination/HDD

 Measurement Result of Contamination on the disk
40000
38000
36000
34000
32000
30000
28000
26000
24000
22000
20000
18000
16000
14000
12000
10000
8000
6000
4000
2000
0STN POR vs Machining & Taper2mm Total
32673

3208940% Reduction
20812
17363

STN3D-1

STN3D-2

STN3D-1

Without
PORTaper
Total

32673

32089

STN3D-2
with Taper
Machining & Taper2mm
17363
20812

It was confirmed that the air spoiler with taper could contain theKarman voltex and decrease the contamination on the disk.

Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

96. Jumboizing Air Spoiler

Jumboizing Air Spoiler to improve NRRO for new product Concern on Contamination increase

R2

5

Air Spoiler “J”
Top Cover
D#5
D#4
D#3
D#2
D#1

Air Spoiler

Disk
ディスクBaseベースAir Spoiler “G”
Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

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7. Break through “PSYCHOLOGICAL INERTIA”
Because we needhigher areal density
than previous model
Hey, reduce
contaminationnear spoiler on
the disk.

What is truly needed?
Not Air Flow!
It’s anotherPhysical Force!
Other ways we have!

Head/Disk engineer

Karman Vortex,
Karman Vortex,
Karman Vortex,
Karman Vortex,…
Can do nothing
about….

Mechanics engineer

TRIZ methodology is based on
breakthrough of“Psychological inertia”
Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

118. Correspondence between HDD’s and TRIZ parameter

Key Word of HDD parameter

TRIZ 48 Parameters

Bit length on the Disk

Length of stationary object(4)Error Rate

Loss of Time (26)、Loss of Information (28)

Seek Time

Duration of Action of Moving Object (12)Weight Saving

Weight of Stationary Object (2)SoundNoise（29)Thermal Stability

Stability（21)Track Per Inch

Information (11)

Reliability

Reliability (35)

Write Fault Frequency

Loss of Information (28)、Loss of Time (26)Power Consumption

Loss of Energy (27)

Positioning Accuracy

Reliability (35)

Rotational Waiting Time

Loss of Time (26)

CostProductivity (44)Radiation

Temperature (22)

Detectability of media defectAbility of Detect/Measure (47)Test Time

Loss of Time (26)、Productivity (44)Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

129. Trial “J” Large Air Spoiler•Jumboizing the air spoiler accelerate the data damage at out side area ofthe media by the media scratch.

•Contradiction Matrix from Inventive Principles– 4 x 28 （Length of Stationary Object/Loss of Information）• 28：
Mechanics Substitution
Introduce electric, magnetic• 24:Intermediaryor electromagnetic fields tointeract with an object .
•3:
Local Quality• 13:“The Other Way Around” => Conductive Air Spoiler– 4 x 35 （ Length of Stationary Object/Reliability）• 35：
Parameter Changes
Enable each part of a system• 31:
Porous Materials
to function in locally optimised• 29:
Pneumatics And Hydraulics conditions.
=> With Taper• 17：
Another Dimension
Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

1310. Trial “J” Large Air Spoiler with TRIZ Idea

 Air Spoiler used for Particle Injection TestFigureModelMaterial

Surface Resistance

Polycarbonate

1 E16(Insulator)

Cross Section

w/o Taper

J
Plastic withCarbon fiber

1 E1~E3（Conductor）

w/TaperJ
w/Taper

GPolycarbonate

Polycarbonate

1 E162mm(Insulator)

1 E16

w/o Taper(Insulator)

Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

1411. Particle Injection Test Result

Number of Particle/HDD

 Measurement Result of Paricle

60%減

Air Spoiler “J”(Insulator)

Air Spoiler “J” Air Spoiler “J” Air Spoiler “G”(Insulator)(w/Taper)(Conductor)
Air Spoiler Type

Significant Improvement of Particle Reduction by Conductive Air Spoiler

Why the conductive air spoiler can reduce the particle accretion?
Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

1512. Failure Mechanism led by TRIZ
Mechanism of Particle Accretion on the Disk by Static Electrical Charge
NanoParticleは、＋の電荷を帯びている
particle have positive electrical charge.

Spoiler Air Spoiler
Insulation
DiskDisk (-)

Particle (+)+ +++++++--------+ +++++++--------+ +++++++--------

Induction Charge
From GroundNano-Particles with positive electrical charge gravitate toward the disk withnegative electrical charge induced by the insulation air spoiler with positiveelectrical charge.
Copyright © 2010, Hitachi Global Storage Technologies, All rights reserved.

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