Optoelectronic System Packaging

IL 2208 Electronic System Packaging
(2B5457 Mixed Signal System Design)
Lecture 14
Optoelectronic and Telecom System
Packaging
KTH/LECS/LRZ
Docent Li-Rong Zheng
Laboratory of Electronics and Computer Systems
Royal Institute of Technology (KTH)
SE-164 40 Kista, Sweden
(lrzheng@mit.kth.se)
Outline
• Optoelectronic System Packaging
• Semiconductor Laser and Optical Amplifier Packaging
• Photo Detector Packaging
• Optoelectronic Package Integration and Assembly
KTH/LECS/LRZ

1. Telecom System Packaging
KTH/LECS/LRZ
Communication System Package Levels
An SDH/SONET Board
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Communication System Packaging Hierarchy
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The Structure of Cabinet
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Communication System Interconnect Level Map
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Cabinet Level Interconnections
Function: connecting different units in a cabinet; Length: 5-40m, high-speed
Interconnections: parallel multi-mode or single-mode optical interconnects
LD Array Interconnection Module
KTH/LECS/LRZ

The Fiber Array
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Hemispherical lens formation process
Unit Level Interconnections
Function: connecting different
board in a unit;
Length: 80cm, high-speed
Interconnections: optical backplane or
electrical backplane
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Optical Backplane for Unit Level Connection

Board Level Interconnections
Function: connecting different components on a board; Length: 10-40cm, high speed
and low noise, Interconnections: BGA, Electrical, O/E-MCM
Optoelectronic
circuit board:
optical side
Optoelectronic circuit
board: electrical side
KTH/LECS/LRZ
Optoelectronic Circuit Board: Trends for Integration
Highly miniaturize in size
with high density array
optical interfaces in integrated
MCM module
KTH/LECS/LRZ

2. Semiconductor Laser and
Amplifier Packaging
KTH/LECS/LRZ
The Key Challenges
• Laser and amplifiers are high power devices: heat fluxes
~4kW/cm2
• Device performance are temperature sensitive
• Devices performance are sensitive to stress induced
degradation
• Alignment tolerances are small (submicron position in SM
fiber or microlens)
• Electrical interconnections: package capacitance and
inductance limit the bandwidth of electrical
interconnections
KTH/LECS/LRZ

Laser and Amplifier Packaging
Bonding wire
Heat sink
Edge emitter laser
Surface emitter laser (SEL)
Surface emitter later (SEL)
with flip-chip packaging
Thermal vias
Poor thermal conductivity
Thermal conductive substrate
Underfill material, good thermal conduction
KTH/LECS/LRZ
Heatsink and Device Metallization
Laser Diode
Adhesion layer
Diffusion barrier layer
Wettable layer
Solder layers
Bonding
Heatsink
Solder layers
Wettable layer
(Transition layer)
Diffusion barrier layer
Adhesion layer
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Heatsink/Heatspreader Metallization
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Device Metallization for Die Bonding
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Ultrasonic Wire Bonding Process
Bonding wire
Heat sink
Aluminum wedge bond
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• GaAs and InP are very fragile.
• Ultrasonic wire bonding is
often used for Si.
Thermocompression/Thermosonic Wire Bonding
KTH/LECS/LRZ
• Thermosonic wire bonding is often
used for optoelectronic chips.

Flip-Chip Bonding
IC
Underbump Metallization
Balls or Metal Bumps
Underfill
Substrate (PCB, ceramic)
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Flip-Chip Assembly Technologies
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Self-Alignment in Flip-Chip Packaging
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Flip-Chip Bonding for VCSEL-Based
Array Devices
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3. Photo Detectors Packaging
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Key Challenges
• High-frequency output: low parasitic
electrical interconnections/packaging
• Alignment: detector sensitivity
• Noise Isolation
• Hermeticity needs
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Parasitic Effects in Electronic Packaging
Package parasitic effects stop high frequency signals!
L=1~10nH
Lower data rate in wire bond package
L < 100pH
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Higher data rate in flip-chip package
Integrated Photoreceiver
Detector and amplifier integration: reduce package level and improve bandwidth
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Flip-Chip Packaging for Photodetectors
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Detector Package with Window
•Hermetic, noise issues
•Numerical apertures sinθ, and d
•Flat window for large area devices
•Centering the device in the package
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Connectorized/Pigtailed Packaging
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Fiber Pigtailed Detector Packaging
With a focus lens
Usually SM fiber,
small area devices
high-speed data link
Without a focus lens
Usually MM fiber,
large area device and
lower performance
KTH/LECS/LRZ

4. Optoelectronic Packaging
Integration & Assembly
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Connectorized Receiver Modules Packaging
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Fiber Pigtailed Receiver Modules
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Fiber Pigtailed Receiver Modules with Flip-Chip
Detector Bonding
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Optical/Electrical Integrated Modules
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LD Package in O/E MCM (optical/electrical multi-chip module)
O/E MCM Substrate Fabrication Process
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O/E MCM Module Assembly
Top View
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Hybrid O/E Assembly
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Device Alignment: Active Alignment
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• Total 6 dimension of freedom
θ z can be eliminated
• First align 3-4um accuracy in 5-axis
micropositioner
• Finally scaning SM fiber array on
the YZ plan while monitoring the
coupled laser output from the
outermost channels, -1um accuracy
Passive Alignment Based on Micromachining Technologies
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Sold Self-Alignment and Mechanical “Stops”
F
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After cool down
Surface Array Device Alignment
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2-Dimensional Fiber Array Alignment
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Using Grooved Silicon Chip
2-Dimensional Fiber Array Alignment
Silicon for SM/MM fibers
Fotoform glass for MM fibers
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Brass for SM/MM fibers

Summary
Optoelectronic Package: electronic package + optical
Communication System Package:
Cabinet Level – MM/SM optical links
Unit Level – optical backplane
Board Level – trend to integration-O/E MCM
Laser and Amplifier Package:
thermal & alignment
Heatsink bonding, wire bonding, flip-chip
Detector Packaging:
High-frequency, hermetic, alignment
Optoelectronic Package Integration and Assembly:
O/E MCM, Hybrid assembly
active allignment/passive alignment,
device array alignment, fiber array alignment
KTH/LECS/LRZ