© et-trends llc 1 ken gilleo – et-trends – ken@et-trends.com nathan kerrick, cookson...

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Ken Gilleo – ET-Trends – Ken@ET-Trends.com

Nathan Kerrick, Cookson Electronics

IBM MicroDrive: 351 MB

MEMS & GMR

Technology

IMAPS 200 Denver

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OUTLINE

• Hard Disk Drive overview

• GR and GMR technology

• Processing of hi-density heads

• The role of temporary adhesives

• HDD assembly

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The HDD (Hard Drive Disk)

Magnetic Disk

SliderFlex

Courtesy of 3M Co

Mag. Head Assembly

Mag. Head Assembly

Positioner

Assembly

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The HDD Head is key to Ultra-High Density

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HDD Technology

• Density increases surpass Moore’s Law.

• MR and GMR are true breakthroughs.

• Density records:– 30 million bits/in2 December 1999 (commercial)– 56 Gbits/in2 on April 2000 (lab)

• Density limits have not been reached.

• The technology is in the complex head.

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MR Head Technology

Contact

MR Sensing Layer(changes resistivity)Insulator Spacer

Soft Adjacent Layer

ShieldShield

bias

MR Effect: changes in electrical resistance by certain magnetically-soft when a magnetic field is turned on and off.

Magneto-Resistive

Measure as

“read” signal

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GMR Head Technology

Shield

Contact

Sensing Layer

Conducting Layer

Exchange Layer

Pinned Layer(magnetically oriented)

Shield

GMR is a quantum effect and relies on electron spin states; >2X more sensitive than GR

Giant Magneto-Resistive

bias

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Write Head

COIL

Write Current

SLIDER

Coil

WRITE HEAD

Magnetic medium

Writing Current

Magnetic coil creates field that“writes” by orienting disk domain medium

ONON

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Merged Read/Write Head

N SS NN SS NN SS N

WRITE

READ

Shield 1

RotatingDisk

Shield 2

Inductive Writing Element

MR or GMR

Sensor

READ WRITE

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Building MR/GMR Head Elements

• Semiconductor wafer fab

• Wafer thinning

• Wafer sawing

• Element planing/polishing

• Head assembly

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First, some adhesive basics.

MixingCasting Adhesive film

Wafer-applied adhesive for die attach

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Long-chained typically organic macromolecules made up of small repeating segments of monomers. Properties such as strength, flexibility, melting point and electrical characteristics can be ENGINEERED into the polymer.

- Engineered molecules

- Highly compatible-Tailored properties

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A polymer that is cross-linked so that melting does not occur under heating.

SOLID SOLID

A polymer that is capable of softening to a flowable "liquid" when heated and hardened again when cooled.

SOLID LIQUID (flowable)

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Polymer Types

Thermoplastic (Linear); mp, reworkable

Thermoset (3-D); infusible, memory

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Thermoplastic as a temporary adhesive

Independent chain motion allows melting; debonding.

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Thermoplastics

can be dissolved or debonded without

dissolving; swelling

Thermoplastics

can be dissolved or debonded without

dissolving; swelling

Solvent Molecules

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Thermoplastic Adhesive FORMS

• Film– sheets– rolls

• Preform– any shape from disk to complex

• Paste– for needle dispense– spin coat for wafer-level

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Resin & Filler Choices

• Fillers– Silver - Electrical & thermal conductivity– AlN, BeO - Thermal, but good dielectric– Unfilled - Insulating

• Resin bond ranges (thermoplastics):

– Low : 100oC– High :400oC– Typical: 150 - 250oC

For Most HDD Processes

Sometimes used to control static.

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Thermoset Adhesives

-------------Thermoplastic -------------

Dispense Oven Cure

DRY Heat & PressurePlace Part

Place Preform

Place

No Pressure Needed

Dispenseor Print

Place Part Dry/Fuse

No Pressure Needed

Coat Wafer:spin, print

Place Part Heat & Pressure

Pasteto

Substrate

Pasteto

Substrate

Pasteto

Wafer

Pasteto

Wafer

FILMFILM

Pasteto

Substrate

Not TemporaryNot Temporary

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Application Processes

• Liquid (paste)– Coat on wafer; spin, stencil, print; dry– Needle dispense on substrate or holder

• Film– Laminate to wafer, then run processes

• Preform (cut to wafer of row shape)– Bond to wafer– Bond to substrate

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Bonding Thermoplastics

GlassyState

Process Window

DecompositionDecomposition

TmaxTminTgTemperature

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Thermoplastic Properties

FILLERSTg Rework Die

ShearThermal Modulus

BondTemp

C C Cmin. PSI @ 25C WmC PSI

none -40 100 - 150 110 1700 0.2 60K

Ag, AlNnone

-25 150 - 200 160 2200 0.3 - 3.0 60K

Ag, AlNnone

45 160 - 220 170 2600 0.3 - 3.0 500K

Ag, AlNnone

98 160 - 250 170 3000 0.3 - 3.0 400K

Ag, AlNnone

180 325 - 400 350 4000 0.3 - 3.0 360K

None 145 200 - 230 210 3800 0.22 150K

None 280 350 - 450 400 4900 0.25 370K

Each row is a different polymerEach row is a different polymer

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SUBSTRATE CONDITIONING INITIAL BOND FINAL BONDCeramic 150oC, 1000 hrs. 2500 PSI 4800 PSI

Au-plated Ceramic

150oC, 1000 hrs. 3100PSI 4900 PSI

Al 150oC, 1000 hrs. 4100 PSI 4500 PSI

Ceramic85%RH, 85oC,

1000 Hrs.2500 PSI 1800 PSI

Au-plated Ceramic

85%RH, 85oC, 1000 Hrs.

3100 PSI 2600 PSI

Al85%RH, 85oC,

1000 Hrs.4100 PSI 3600 PSI

Ceramic-65oC to 150oC,

500 cycles2500 PSI 4000 PSI

Au-plated Ceramic

-65oC to 150oC, 500 cycles

3100 PSI 3700 PSI

Al-65oC to 150oC,

500 cycles4100 PSI 4800 PSI

Bond Strength of Die Attach Adhes.

Bonding: 180C/ 10sec, 135g; .080" x .080" Ni/Au Kovar

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Removal Options

• Heat element area

• Peel off parts

• Immerse assembly in solvent

• Remove parts

• Rinse in solvent

HEAT

SOLVENT Preferred for HDD work

Preferred for HDD work

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Wafer Lapping (thinning & polishing)

Attach wafer to lava stone with temporary adhesive.

Attach wafer to lava stone with temporary adhesive.

HDD Wafer

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Wafer Lapping Process

Wafer

Rotation

HolderLava Rock

TemporaryAdhesive

Grinding MediaGrinding Media

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Slicing1. Heat Bond Wafer

2. Slice into Rows

3. Debond with Solvent

Temporary adhesive

(sawing into rows)

ROW ofHeads beforesingulating

Rows formed after slicing

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AdhesivePaste

Lapping & Edge Polishing1. Dispense Adhesive

2. Mount Rows

3. Bond by heating

Automatic Dispenser- Speedline

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Temporary Adhesive

Row Bonding Step

Rotate 90o

with cut, or rough side facing up.

Rotate 90o

with cut, or rough side facing up.

(part of lapping & polishing)

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Debond in solvent

Rows are planarized/leveled/lapped

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Finished rows are sliced into head elements

Use temporary adhesive

Use temporary adhesive

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HDD Assembly

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Conclusions

• HDD Beats Moore’s Law and IC industry

• The breakthrough was GMR

• MEMS is playing a role

• Density limits have not been reached

• Photonics is being added

• Expect continuous density increases

73 GB

IBM