Thermo-compression bonding for fine-pitch copper pillar flip chip interconnect
Intel : Amram Eitan, ASMP: SW Lau
Outline
• Drivers for Chip Attach Technology
• Thermo-Compression-Bonding (TCB) technology
– concept, unique features, as compared to Mass
Reflow
• TCB equipment characteristics to enable robust
chip attach processes
Chip Attach Assembly History
Multiple Chip Attach Technologies available: Technical and cost driven
• Drivers for Chip Attach Technology
• Thermo-Compression-Bonding (TCB) technology
– concept, unique features, as compared to Mass
Reflow
• TCB equipment characteristics to enable robust
chip attach processes
Drivers for Chip Attach Technology: Interconnect Scaling: FLI
FLI scaling Challenges: Placement accuracy and die alignment
5
Drivers for Chip Attach Technology: Package Geometry Aspects
Substrate and die thickness reduction to meet package Z height roadmap- challenges
die and substrate warpage (temperature dependent)
• Drivers for Chip Attach Technology
• Thermo-Compression-Bonding (TCB) technology
– concept, unique features, as compared to Mass
Reflow
• TCB equipment characteristics to enable robust
chip attach processes
Intel’s Mass reflow Chip Attach Technology
• Mass Reflow Chip Attach utilizes natural forces, to ensure die to
substrate position before and at reflow
• Limitations:
• When die and substrate are very thin, warpage overcomes
the natural forces, and non-contact opens occur
• Pitch scaling (FLI and towards 3D assembly) is driving
higher placement accuracy requirements
Non-Contact Open
TCB is becoming a high volume chip attach process in 2014 at Intel
Intel’s Next Generation Chip Attach Technology
Bond Force
Bond Head Temperature
Bond Head Z Position
Temperature ramp
up to melt solder Temperature ramp down to solidify solder Solder
chase
TCB bonding profiles
• TCB utilizes an actual process event to trigger the next step in the bond
operation
• TCB enables unit level process feedback, allowing automated process decisions
based on unit to unit output behavior
• TCB enables tight process control due to its ability to gauge the health of each
unit, as needed
Examples of TCB Bonding Results
Sensitivities that need Equipment features and performance:
• Thermal performance (heating/cooling, uniformity)
• Geometrical accommodation (flatness, warpage, thickness)
• Atmosphere
Process Time
• Process times of 4s and below have been
demonstrated
• Equipment features have been designed to enable short
process times
Key Messages:
• TCB technology is addressing Intel’s and
market’s roadmap towards finer pitch, thinner
and complex packages
• Process control in TCB allows “tailoring” of the
joint geometry, as well as real-time feedback for
quality assurance
• Process times are minimized by the unique
design of the TCB equipment
• Drivers for Chip Attach Technology
• Thermo-Compression-Bonding (TCB) technology
– concept, unique features, as compared to Mass
Reflow
• TCB equipment characteristics to enable robust
chip attach processes
Module Designs to Enable Robust Chip Attach Process
• Placement Accuracy (XY & angular)
• BHZ Position Accuracy
• Co-planarity Measurement & Adjustment
• Die & Substrate Vacuum
• BH Rapid Heating and Cooling
• Thermal Management
• Inert Environment
Placement Accuracy
• Best layout for placement accuracy
– Stationary bond head (BH) and moving
bond stage (BS) with split view optics on
optics table (OT)
• Air bearing for all moving axes with
high resolution encoders to reduce
motion errors
– BHZ, BH mini-Z, BS XY, OT XYZ
• High resolution camera to enhance
alignment accuracy
– With closed-loop temperature control
• The whole bonder structure is
supported by pneumatic isolators
– Best vibration isolation from environment
CoG XY Placement Results
• XY placement accuracy well within ±2µm
– CoG glass die size: 33mm x 22mm
– Each test: 2x 16 runs @ 3 BS positions on each BS
– BH & BS temperature: 150C
33mm
22mm
Worst Case Corner Performance
• Angular placement accuracy well
within ±0.01
• Worst case corner offset < 3µm
BH with Advanced Process Capabilities
• Completely in-line force production
• Both Large (500N) and Small (1N) force
produced from a single head
– Force sensors with dynamic ranges
• Air bearing guidance for zero wear and
ultra-low friction for long term reliability
• Ultra-high accuracy encoders for
ultimate Z position and bump height
control
• Advanced cooling method to prevent
thermal drift due to BH heater
• Advanced active tip tilt mechanism for
co-planarity adjustment
BHZ Position Accuracy
• Z position accuracy at 350C within ±1µm
– Ensure bump height control during local reflow process
BH mini-Z A-B B-C C-D D-E E-F F-G G-H All B&H C&G D&F
Mean 10.11 10.25 10.03 10.15 10.28 10.05 10.22 10.16 427.80 417.56 407.52
S.D. 0.05 0.05 0.05 0.05 0.06 0.06 0.05 0.10 0.07 0.08 0.07
Cpk@±1um 5.400 5.044 6.290 5.439 4.177 5.032 5.541 2.708 4.194 2.961 2.985
10um step
Bond Force Accuracy
• Force accuracy within ±0.1N when
set force is 1N
– BH temperature: 350C
– BH search speed: 1.0 mm/s
– Use insulator with ball contact
– Each test: 16 cycles
Set force (N) 5 2 1
Set force accuracy
Spec ±5% ±5% ±20%
Mean (N) 5.185 2.040 0.979
SD (N) 0.013 0.014 0.028
Cp 6.639 2.368 2.410
Cpk 1.729 1.421 2.161
Impact
Mean (N) 1.771 1.650 1.579
Max (N) 1.818 1.683 1.640
Min (N) 1.730 1.625 1.524
Range (N) 0.088 0.058 0.115
Co-planarity Measurement & Adjustment
Side View
Tip-tilt
actuators
US PATENTED over 30mm
Die & Substrate Vacuum • Die and substrate are hold flat firmly during bonding by product
specific vacuum trough design on die nozzle and substrate
pedestal
• Maximum 4 individual vacuum channels for substrate pedestal
• Real time monitoring of all vacuum channel analog vacuum
level during bonding
BH Rapid Heating and Cooling
• Performance designed for large die
– Die size up to 33mm x 22mm
• Heating rate
– Maximum without load: ≥ 125C/s in free air
– Controlled: within ±5% of set rate
• Cooling rate
– Maximum without load: ≤ -50C/s in free air
• Temperature uniformity
– ±5C @ Cpk 1.33
Advanced Thermal Management
• Split-view optics
– Symmetric layout
– Same length of optical path for up/down look optics
– Low CTE materials to reduce thermal drift
– Active temperature controlled chamber to ±0.5C
• Bond head heater
– Ceramic insulator in contact with heater
– Top cooling block with air flow
– Reduce temperature from 400C at heater surface
to 30C at top mounting surface
– Thermal mapping for BHZ position compensation
• Bond stage heater
– Ceramic insulator in contact with heater block
– Pillar support with air isolation
– Temperature rise < 3C at base plate when BS
heater surface at 200C
Innovative Inert Environment Solution
• Moving micro inert
– Pedestal on BS with shielding by air gap
• Macro inert chamber
– Enclose BH and OT modules
• Macro and micro chamber connected
by a bond window opening
High Volume Manufacturing (HVM) Configuration
Substrate
Die
Bonded units
Key Messages:
• Proven high quality HVM solution for high
precision, large die thermo-compression bonding
• Proven portable module solutions / core
technologies for current TCB challenges
• Future-proof platform that is forward compatible
with advancement in packaging roadmap
Summary
• Packaging roadmap towards thinner and more
complex assembled products is driving new
required chip attach capabilities
• Thermo-compression bonding was developed
and implemented at Intel towards High Volume
Manufacturing starting in 2014
• ASM’s TCB equipment provides unique
features to enable high quality, fast and robust
chip attach process
Thank You for Listening