joining and packaging technology for high temperature ......• adhesive •brazing •glass •...
TRANSCRIPT
Copyright © TWI Ltd 2010Technology Engineering
5th Annual IeMRC Conference
21st September 2010
Joining and Packaging Technology for High Temperature Electronics
Beyond Solder?
Norman Stockham
TWI
Copyright © TWI Ltd 2010Technology Engineering
TWI
• Independent R&T organisation
• Specialising in materials, joining,
assembly, training & technology
transfer
• Limited by guarantee/non-profit
distributing
• 3500 industrial member sites in 75
countries
• 580 staff, £58M turnover
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a
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High Temperature Electronics
Higher ambient temperatures:
200-400°C 400-800°CIncreased exposure to chemically active environments:
- Humidity - Brake fluid
- Salt spray - Exhaust gases
- Fuel - Radiation
- Oil - Body fluids
Industry sectors:
- Automotive - Power
- Aerospace - Military
- Oil & Gas - Medical
- Construction
Electronics & sensors are increasingly being applied formonitoring & control in high temperature harsh environments
Bore hole data logger
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Device & Substrate Temperature Tolerance*
Device
Temp
tolerance °C*
Silicon (Si) 125-250
Silicon-on-
insulator (SOI)
250-300
Gallium Arsenide
(GaAs)
350
Gallium Nitride
(GaN)
>500
Silicon Carbide
(SiC)
>750
Diamond >800
* Scatter exists in the values in literature
Substrate Material
Typical max
use temp °C*
Epoxy-glass (FR4) 110-140
Bismaleimide Triazine (BT)
Epoxy
180-190
PTFE-glass 170-200
Polyimide-Quartz 250-280
Alumina (Al2O3) >1000
Silicon carbide (SiC) >1000
Silicon (Si) ~1000
Aluminium (Al) 660
Al-Si MMC
Copper 1083
Ni-Fe-Co (Kovar) 1450
Stainless steel 1400-1500
*Dependent on environment/grade/metallisation etc
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Joining Technologies for High Temperatures >200°C
• Solder
• Adhesives
• Welding
• Brazing
• Glass
• Mechanical
• Disruptive
Die/substrate attach
Device interconnect
Package sealing
Package interconnect
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Solder Applications - Electronics
Die attach
EMI shielding attach
Heat sink attach
Package sealing
Selective device soldering
Track repair
Device Alignment
Substrate Attach
Passive
component
attach
Device Interconnect
Connectors
Package attach
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Benefits of Solder
• 6000 years experience
• Relatively low melting point
• Very high production volume capability
• Electrical and thermal conductivity
• Reworkable
• Joint gap tolerant
• Self aligning
Many electronic components and materials are designed for soldering
Courtesy British Museum
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Typical Solder & Braze Alloys
48Al-52Ge 424High
Temperature
Solders
97Au-3Si 363
88Au-12Ge 356
95Pb-5Sn 300-315
Alloy Melting Point/Range ºC
99Cu-1Ag 1070 - 1080
>450°C Braze
100Au 1064
82Au-18Ni 955
60Au-20Cu-20Ag 835 - 845
91.5Cu-2Ag-6.5P 643 - 796
58Au-42In 495
95Pb-25Pd 454
1Sn-2Ag-97Pb 295-320
Conventional
Electronics
Solders!
80Au-20Sn 280
99Sn-1.0Cu 227
96.5Sn-3.5Ag 221
95.5Sn-3.8Ag-0.7Cu 217
63Sn-37Pb 183
62Sn-36Pb-2Ag 179
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Device & Substrate Attach
Joining Methods:
• Solder
• Adhesive
• Brazing
• Glass
• Anodic bonding
• Mechanical
• Diffusion bonding
• Welding
• Novel
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Device & Substrate Attach
Design Issues/Considerations
• Differential thermal
expansion causes
deformation & stress
• Operating temperature
capability
(eg >200°C)
• Thermal Conductivity,
(Solder: 30-50 W/mK) Coefficient of thermal expansion
50
24.519 17 15.8
6.4 5.9 4.5 4 3
0
10
20
30
40
50
60
Epoxy
Alu
min
ium
Low
str
ess e
poxy 'G
lob top'
Copper
FR
-4
94%
Alu
min
a
Kovar
AlN
SiC
Silicon
CT
E (
x10-6
in/in/°
C)
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Device & Substrate Attach
Adhesive Die (Chip) AttachLevel of adhesive use: Extensive
Reasons for adhesive use:
- Low cost
- Ease of assembly
- Tailored properties (mechanical/electrical)
- No plating
- Low temperature processing (low stress)
- Electrical/thermal conductivity (solder)
- Stress absorption
- Rework possible
Typical adhesive die attach materials:
- Acrylics, Epoxies & Polyimides (eg silver filled)
Si die to Al2O3 substrate
Flip Chip Bonding
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Device & Substrate Attach
Typical Adhesives
Polymer type
Typical maximum
continuous service
temp ºC *
Chemical and
solvent resistances *
Polyurethane (TS, TP) 95 Poor
Epoxy (TS) 120-200 Excellent
Phenolic (TS) 150-250 Good
Polyimide (TS) 260 Excellent
Silicone (TS) 260 Good
Polyamide-imide (TP) 270 Good
TS Thermoset
TP Thermoplastic
* Dependent on environment and operation
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Device & Substrate Attach
Eutectic Die Attach
Gold-Silicon Eutectic Die Attach:
Eutectic composition: 3%Si, MP 363°C
Thermal Conductivity: 60 W/mK
Issues: Stress on large die
Typically: Used on small die (<8 x 8mm)
Ceramic packages
Die backside Au metallised
Can employ Au or Au-2%Si preforms
Process temperature: 425°C
Scrubbing to disrupt Si Oxide
Hot (eg 175°C) nitrogen blanket
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Device & Substrate Attach
Liquid Phase Joining
Fusible metal alloy >450°C.
Application of heat to reflow braze alloy.
Braze metals with/without metallisation.
Ceramics, usually metallised (eg Mo/Mn, Sputter coating, thick film).
Ceramics can be brazed directly using active braze materials (eg Ti additive).
Requires flux or a protective atmosphere.
90mm Φ Silicon Carbide to Tungsten
Active metal braze
Brazing
Application of heat and pressure
in an oxygen rich environment.
Copper oxidises and forms
eutectic liquid (Cu2O) at 1070°C.
Copper to Alumina
Direct Copper Bonding
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Device & Substrate Attach
Solid Phase Joining
Friction Welding
Ultrasonic Welding
Alumina-copper with gold interlayer
Diffusion Bonding
Aluminium to Alumina
Electrostatic Bonding
Silicon to PyrexAluminium to Alumina
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Device & Substrate Attach
Reducing CTE Stress via Interlayers
Silicon Nitride to Steel
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Device & Substrate Attach
Carbon Nanotube (CNT) Interfaces
MWCNT Mat
Top Side Overview
Tout
High power chip
Heat sink
Tin
CNT composite
adhesive
High thermal conductivity ~1000 - 3000 W/mK
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Device & Substrate Attach
Spray Coating Technologies: Reduce Interfaces
Cold SprayHVOF Spray
Cu-Al2O3W-Cu Blend Cu Heat Sinks
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Device & Substrate Attach
Moulded Al2O3 / Al-SiC MMC Package
Embedded
Al2O3
substrate
Al-SiC
package
Conventional
Al2O3
substrate
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Device to Package Interconnect
Interconnect Methods:
• Wire bonding
• Flip chip bonding
• Soldering
• Adhesives
• Welding
• Mechanical
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Device to Package Interconnect
Wire Bonding
Cu ball bonding
Ribbon Bonding
Al ball bonding
• Mature technology
• High process yields
• Design flexibility
• Increasing power
capability
• High temp capability
Needs Protection
Power Device Bonding
Courtesy of Orthodyne Electronics
Au ball bonding
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Wire Pad
Upper continuous
service temperature ºC *
Au Al ~150-180Interdiffusion
Brittle intermetallics
Increased resistance
Loss of strength
Cu Al ~200
Al Ni ~300
Pd Au ~500
Al Al ~600
Melting temperatureAu Au ~1000
Pt Pt >1000
* Influenced by environment and metallisation system
Device to Package Interconnect
Wire Bonding Service Temperatures
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Device to Package Interconnect
Alternative Interconnect Processes
• Flip Chip Bonding/Welding
- Adhesives
- Thermocompression
• Conductive Adhesives + leadframe
• Mechanical
• Direct write/print?
• Laser & Resistance Welding
(wire, leadframe, beam lead):
Flip chip bonding
Silicon Nitride Microclips
Courtesy University of Cambridge
Microjet
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Package Sealing/Protection
Metal housings
Polymer housing
Hermetic Packaging, eg:
Kovar, plated lids
Aluminium alloy
Stainless steel
Titanium
Copper
Ceramic
Glass
Non Hemetic (Polymer), eg:
Polymer housing
Potting
Glob top
Conformal coating
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PolymerTypical continuous
service temp ºC * MetalTypical continuous service
temp ºC *
Polypropylene (TP)
(glass reinforced)105-125
Copper 200 (oxidation)
Polycarbonate (TP) 120 Al alloys 300 (creep)
PPA (TP) 190 Nickel irons 400 (oxidation)
LCP (Polyester) (TP) 240 Titanium 600 (oxidation)
PEEK (TP) 250 Stainless steels 800 (oxidation)
PPS (TP) 260Nickel/colbalt heat
resistant alloys
1000 (creep)
Polyimide (TS) 260 Ceramic
PTFE (TP) 285 Glass ceramic 600-700 (strength reduction)
SiC 700-800 (degradation)
Al2O3 800 (creep)
Sapphire 1500-1600 (-)
TS = Thermoset / TP = Thermoplastic* Dependent on environment
Package Sealing/Protection
Outer Package Materials – Operating Temperatures
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Package Sealing/Protection
Conventional Hermetic Sealing Processes
Resistance Seam Sealing
- Brazing
Laser & Electron Beam Welding
Electron Beam Welding
Power supply
Work table
Electrode Lid
Base
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Package Sealing/Protection
Anodic Bonding/Wafer Level Packaging
MEMS RF
module
Typical Parameters:
Temp: 200-500°C
Voltage: 200-2000 Vd.c.
Time: 10s-120min
Polarity: glass negative
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Package External Interconnect
Joining Methods:
• Soldering
• Conductive Adhesives
• Welding
• Brazing
• Mechanical
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Package External Interconnect
Replacement of Solders by Conductive Adhesives
Reasons for adhesive use:
- Environmental (Pb-free)
- Low processing temperature
- Fine pitch capability (eg: ACA)
Primary choice issues:
- Long term reliability
- Electrical conductivity
- Mechanical strength
- Alignment/Co-planarity of leads/board
Typical conducting adhesive for solder replacement
- Ag filled epoxies
Adhesive SMT
ACA display Interconnect
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Package External Interconnect
Replacement of Solder by Welded Terminations
Ultrasonic
Percussive arc
TIG
Coil Windings
Lead frame assembly
Wire to pin connectionsWire terminations(Courtesy of Amtech)
Wire and leadframe
Resistance
Laser
Ultrasonic
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Package External Interconnect
Friction Acoustic Bonding
Typical Materials: Aluminium
Copper
Steel
Polymers
Copper ribbon cable to PCB
Load
Rotation
Traverse Speed
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Package External Interconnect
Replacement of Solder by Welded Terminations
• High temperature capability
• Low resistance joints
• Reduced footprint
• No plating/intermediary material costs
• No soldering flux/residues/cleaning chemicals
• Automated processes
• No ‘contaminants’ when recycled
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Replacement of Solders by Disruptive Technology
Remove joints!
• Increase active device functionality
• Reduce number of interfaces
• Hybrid/COB type technologies
• 3D, SiP
• Wafer scale packaging
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Disruptive Technology
High Density Packaging
Benefits:
• Improved performance
• Reduced size & weight (2 to 10 times)
• Fewer SMT components, faster throughput
• Reduced costs per function
• Reduced external wiring
• Improved reliability & EMC emissions
Embedded Passive Devices
Typical thicknesses:
Die: 40-70µm
Adhesive: 10-20µm
Package: 1.4mm
Stacked Die Packaging
Courtesy of ASE Group
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Disruptive Technology
System in Package (SiP)
PCB
Flip chip
deviceSiP to pcb
interconnections
thermal dissipation
SiP IDwire bond
devicePassive
component
SiP packageinternal
interconnection
screening
Package in
Package
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Material
Typical upper operating
temperature ºC *
Adhesives (conductive) 250
Soldering 250
Glass Fusion 350-1000
Brazing 450-1100
Ceramic Adhesives 200-1500
Welding 200-2000
* Dependent on materials and application
Summary & Conclusions
General Thermal Hierarchy
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Summary and Conclusions
• Solder technology is not easily replaced in the high volume PCB assembly market
• Solder has to a large extent been replaced in die attach, device interconnect & package sealing.
• There will be a reduction in solder joints as a consequence of on going drivers in electronics aimed at:
– increasing product performance (eg: density & operating temp.)
– reducing size
– tightening environmental legislation
• There are alternatives to solder for higher temperature applications (eg >200ºC). However, these have to be considered at an early design stage in conjunction with device & packaging materials, interconnect, layout and production requirements.
Copyright © TWI Ltd 2010Technology Engineering
Thank you I hope you enjoyed this
presentationNorman Stockham
TWI
Granta Park
Cambridge, UK
Tel: +44 (0)1223 899323
Email: [email protected]