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8 MEMS Packaging
•Ken Gilleo PhD•ET-Trends LLC
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Packaging Classification
Packaging Classification
1. Package discrete MEMS device (non-WLP)
2. Partial WLP; pre-packaging; e.g. capping
3. Total WLP
Bond protective wafers with vias
Bond protective wafers with vias in MEMS
Integrated package with 2nd-level connectors
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Hermetic PackagingHermetic Packaging
• Metal
• Ceramic
• Combinations
Plastic has not “proven” hermeticity – passing leak test is not enough;Result is generally a Near-Hermetic Package (NHP)
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OPEN INSERT FILLPlastic
Conductor Insert
Plastic Molded PackagePlastic Molded PackageMetal Lead Fame (MLF)
Thermoplastic
Quantum Leap Packaging
RJR Polymers
RJR Polymers
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PCB Fabricated Enclosures
PCB Fabricated Enclosures
• Fabricated PCB substrate; BGA, QFN
• Add walls; various methods used
• Die attach & wire bond chip (s)
• Seal lid
• Singulate
Used for non-hermetic MEMS such as microphones
Knowles Electronics
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Ported Flip Chip BGA
Ported Flip Chip BGAEncapsulant
MEMS FLIP CHIP
Light pipe or gas accessUnderfill
Dam
Selective; semipermeable membrane, etc.
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WLP ProcessesWLP Processes• Wafer preparation
MEMS release step Coat (polymer), treat; anti-stiction, other
• Wafer bonding Apply adhesive if required Bond
• Singulation; cap, MEMS, both
• Secondary packaging if required
• Test
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Partial WLP: Pre-Packaging
Partial WLP: Pre-Packaging
• Form package components Caps in wafer Couplings, fittings, ports, or none
• Assemble Place sub-components Wafer bonding
• Move to final packaging process Capped wafer is transportable Packaging foundry may handle
Popular for inertial sensors;
accelerometers, gyro.
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MEMS Wafer
Cap
Printed Adhesive Wallsor use etched features
Wafer-Level CappingWafer-Level Capping(1) Print Adhesive
(2) Bond
(3) Singulate; may be complex
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WL “Cap & Mold”WL “Cap & Mold”
2. Attach & bond device
1. Apply cap to device or wafer;solder, weld, bond.
3. Conventional overmolding or dispensed encapsulant
MEMS Chip
Cap
Vacuum
Seal
After singulation steps
Cross-section
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Lid Sealing/BondingLid Sealing/Bonding
• Used for virtually all cavity packages
• WL lid bonding is called “capping”
• Many methods, old and new
• Wafer bonding & lid seal can share methods
Can use many of the same methods as wafer bonding
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1. Form sheet of polymer film or resin
2. Cut or mold into matrix; laser or die
3. Bond tack to lens disk
4. Flip lens/LCP array and align to wafer
5. Seal/bond to wafer with laser,such as near-IR
6. Singulate by sawing
Wafer-Level with Polymer Films
Wafer-Level with Polymer Films
Laser spot or diode bar line
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Total WLPTotal WLP
• Electrical pass-through; e.g.; TSV
• Enclosure
• Interconnect to PCB (2nd-level)
• Controlled atmosphere as required
• Non-electrical I/Os as required
• General package attributes
Processes must provide:
TSV = Through Silicon Vias
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Interconnect for WLInterconnect for WL
1. Through chip (drill & fill; plasma, RIE)
2. Route conductors over/under
Same methods been adopted & developed for 3D stacked chips
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Integral CapsIntegral Caps
• Form capping structure
• Clean
• Vacuum or gas environment
• Seal port
• Singulate
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Fabricate Caps on Wafer(Hexal MicroMold Process)
Fabricate Caps on Wafer(Hexal MicroMold Process)
• Etch Recess
• Deep Etch
• Deposit sacrificial & pattern
• Plate Au bumps & seal
• Release
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Micro Cap AssemblyMicro Cap Assembly
• Transfer caps to MEMS
• Align
• Bond
• Separate
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Sacrificial
Integrated PackageIntegrated Package
Base
MEMS Structure
Deposited Layer
EvacuateSeal
…or add port or coupling
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Device-Specific Packages
Device-Specific Packages
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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
Ink Jet “Gun”
I-TAB package
Ink Jet “Gun”
I-TAB package
MEMS bare die
MEMS
Encapsulation
EncapsulationSelective
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Pressure PackagesPressure Packages
Bishnu Gogoi, Motorola
Motorola Unibody Package
Cost can be too high
Protective Coating; e.g.; Parylene
Corrosion can occur under the coating in harsh environments
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Bio-MEMS & Fluidics Packaging
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Bio-MEMS ChallengeBio-MEMS Challenge• Biocompatibility; inert
• Sample into pressurized system
• Variety of energy transfer modes
• Interfaces in hostile environments
• Protection within life system
• Remakable couplings
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Fluid Coupling Technology
Fluid Coupling Technology
• Fluidic MEMS device (s)
• Inter-chip coupling as required
• Auxiliary unit connections
• Through-package fluidic interface
• Electrical I/Os and 2nd-level
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Fluid Coupling DesignFluid Coupling Design
Ellis Meng; California Institute of Technology
Materials: silicon, polymersProcesses: bulk etching, RIE
Bulk Coupler AssemblyPlastic Insertion Using Cryogenics
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BioMEMS
BioMEMS
IME Singapore
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Plug-inMEMS
Plug-inMEMS
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Session SummarySession Summary• MEMS is a major packaging challenge
• Typically device-specific
• Often application-specific
• Result is non-standard, high customization
• Trend Discrete pWLP full-WLP
• More WLP in the future
• Some MEMS packaging suppliers evolving