© et-trends llc 1 mems packaging & assembly issues ken gilleo, phd et-trends gilleo@ieee.org...

© ET-Trends LLC 1

MEMS PACKAGING & ASSEMBLY ISSUES

Ken Gilleo, PhD

ET-Trends

gilleo@ieee.org

SMTAi 2000

Chicago

SMTAi 2000

Chicago

Intellisense

© ET-Trends LLC 2

OUTLINE

• MEMS Introduction & Survey

• Packaging challenges

• Assembly issues

• MOEMS; let there be light* (optics)

• Conclusions

* control

© ET-Trends LLC 3

Nano World

Where all technology converges

The convergence point of electronics, mechanics, physics, chemistry and biology, etc.

ElectronicsM

echan

ics

Optics

MEMS

OE OM

MOEMS

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MEMS

• Semiconductor processing used

• Merges mechanical motion & electronics

• VERSATILE

– sensing

– computing

– motion

– control

Marauder MEMS Monster?Marauder MEMS Monster?

Micro-Electro-Mechanical System

U of W

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MEMS Processing• Electronics fab: standard methods

• Silicon Machining:

– Define mechanical parts by lithography

– Form sacrificial SiO2 in “removal” areas

– Etch away SiO2 to free mechanical parts

• Many other micro-machining processes are available

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MEMS Motion• Deformable; cantilevers, beams, membranes

• Sliding, linear

• Rotating; partial, full, multi-plane

• Rotating Inter-contact; gears, wheels

• Hinges

• Combinations

Sandia, UW, AD

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MEMS “Engines”

• Electrostatic; very efficient*

• Thermal

• Electromagnetic

• Pneumatic

• Hydraulic

• Photoelectric *Surface area is relatively high, mass is very low; surface effects are important

*Surface area is relatively high, mass is very low; surface effects are important

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MEMS Device Input Output

Accelerometer Motion Electrical3D Motion Detection Motion ElectricalInk Jet Electrical Motion, fluidDigital Mirror Array Electrical and light Controlled lightMicro-Spectrophotometer “Light” ElectricalDNA Analyzer Biological samples ElectricalDisk Drive Heads Magnetic ElectricalOptical Switches Electrical and light Electrical & lightCapacitors, Tunable Electrical/RF RFRF Tuners Electrical/RF RFGyroscopes Electrical/motion ElectricalDiagnostics (in vitro) Electrical/liquid ElectricalInfrared Imagers IR/electrical ElectricalMicro-Relay Electrical Electrical

Pressure Sensors Force directly/indirectly Electrical

MEMS Products

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MEMS Structures

IBM MEMS DNA Detector

Electrostatic Relay - UW

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More MEMS

TweezersUW-Madison

Are the Microbots” coming?

Are the Microbots” coming?

Guess?Guess?

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The real problem may be Lack of

KNOWLEDGE,not

Lack of TECHNOLOGY

The real problem may be Lack of

KNOWLEDGE,not

Lack of TECHNOLOGY

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Packaging Challenges

• MEMS devices can be very fragile

– pre-package handling concerns

– more protection by package

• Most require hermetic package ($$$)

• MOEMS (later) requires a window & controlled

atmosphere.

• Biggest challenge: cost-effective, high

volume packaging

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MEMS Packaging Types

• Traditional hermetic; metal or ceramic

• Cap-on-Chip

– wafer-level

– device-level

• Silicon Sandwich

• Near- and non-hermetic

• Selective/partial packaging

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Packaging

MicroRelay - Cronos (HERMETIC)

Accelerometer (CAP)

Ink Jet MEMS in TAB Package (SELECTIVE)

DPL Modules, TI (HERMETIC)

No StandardsNo Standards

(HERMETIC)

(HERMETIC) (HERMETIC)

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This type of machine can be used to selectively encapsulate MEMS- one like this is used on ink jet cartridges. Courtesy of Speedline

Selective Encapsulation

Ink Jet “Gun”

I-TAB package

Ink Jet “Gun”

I-TAB package

MEMS bare die

MEMS

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Cap-on-Carrier

MEMS IC

This packaging method is suitable for accelerometers, gyroscopes and other motion detectors that can be sealed.

This packaging method is suitable for accelerometers, gyroscopes and other motion detectors that can be sealed.

Silicon or Metal CapMolded or Liquid Encapsulant

Solder, weld, or polymer

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Cap-on-Chip(level-0)

MEMS Chip

CAP

Vacuum

Seal

Can now be handled like an ordinary die - almost!

Can now be handled like an ordinary die - almost!

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Cap-on-Chip Variants• Etched Silicon, ceramic, glass

– Indent Reflow Sealing (IMEC)

– Wafer-Level Protected (AMKOR)

• Silicon Sandwich; GIT

• Metal, low CTE?

• Plastic?

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Cap-on-Chip Overmolding

MEMS IC

2. Attach & bond device

May require gel coatto protect thin cap

1. Apply cap to device or wafer;solder, weld, bond.

3. Conventional overmolding followed by solder ball attach.

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MOEMS

• Projection Mirrors

• Photonics Switches

• Gratings

• Fiber Aligners

• Modulators, Shutters

• Movable Lenses

Micro-opto-electro-mechanical systems

A Market powered

by the Internet!

A Market powered

by the Internet!

A Technology that will

power the Internet!

A Technology that will

power the Internet!

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Optical MEMS or

Cronos (JDS-Uniphase)Micro-Mirror

Lenses Array

Micro-Mirror Array - TI

Pop-Up Lens

Rotating Mirror-UCLA

Cross-switch mirrorShutter - Sandia

Fiber Alignor

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Micro-Mirror Close-up by TIon off

Ref. “Digital Light Processing TM for High-Brightness, High-Resolution Applications”Larry J. Hornbeck, hbek@dlep1.itg.ti.com

World’s most complex machine?

World’s most complex machine?

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MOEMS Micro-Mirror

WINDOW

HEAT SINK

Ceramic

Weldor

seal

MEMS Digital Mirrorsone section

HERMETIC

Getter

250,000 mirrors

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Encapsulant

Flip Chip for MOEMS?

MEMS FLIP CHIP

Light PipeUnderfill

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MOEMS Flip Chip BGA Package

MEMS IC

Seal or dam

Light Pipe

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Agents that counteract harmful contaminants within a sealed package; this includes solids, liquids, gases and combinations.

GETTERS

Will guard and control package environment over an extended time.

Will guard and control package environment over an extended time.

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• Particle: attracts and holds.

• Moisture: desiccant.

• Gas: adsorbs/chemically converts to liquid

or solid.

• Combinations.

• Others are possible.

Types of Getters

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Why Use Getters?

• Remove harmful agents from the device environment.

• Control atmosphere for many years.

• Provide the maximum security and reliability; highest life expectance.

• Protect optics; mirrors, lenses

• Reduce wear

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• Moisture

• Particle

• Hydrogen

• Hydrogen

• Combinations

Available Getters

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Assembly Issues

• Safe handling; some are shock sensitive

• Orientation; can be critical

• PWB & joint; change affects MEMS sensitivity

• Testing; not well established for some devices

• Free path; light, sound, molecules

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Accelerometer Example

Analog Devices ChipSensing Mechanism (AD)

Result of rough

handling = “dead” component

Result of rough

handling = “dead” component

High surface area = high attraction =

“STICTION”

High surface area = high attraction =

“STICTION”

For air bags

INOPERABLE

INOPERABLE

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Stiction Solutions

• Liquid lubricants

• Gases, vapors

• Polymer films; Fluorinated Parylene

• Treatments

• Design; “no contact”

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Assembly Factors

• Component skew

• Component non-coplanarity

• Solder joint mass and shape

• Flux residue

• Board thickness

• Board warpage

All change accelerometer behavior

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Conclusions

• MEMS: a key 21st century technology

• The packaging is more difficult

• Expect new & unusual packages

• Assembly has new constraints

• New guidelines are needed

Let’s take the bite out of MEMS