TI. T. = Total Thermal Impedance. BLT = Bond Line Thickness of TIM. K = Bulk Thermal Conductivity of TIM. R. C. = Therma
Dr. Glenn Mitchell Oct. 6, 2015
THERMAL MANAGEMENT Challenges, Requirements and Solutions for the Electronics Industry
Agenda • Introduction • Thermal Industry Trends • TIM Challenges, Needs & Criteria • TIM Industry Solutions • Summary • Questions
© 2015 by Honeywell International Inc. All rights reserved.
Thermal Management Industry Trends
© 2015 by Honeywell International Inc. All rights reserved.
Industry Trend: Power Densities Accelerating VGA Power Consumption
Market Dynamics
400
392
350 283
250 200
410
340
300 Watts
- Increasing power consumption for CPU, APU, GPU, and chipsets - Thermal performance & reliability becoming increasingly important across more applications
450
250 216.4
150 100 50 0 2009
2010
2011
2012
2013
Server and Telecom Heat Load
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Rising Power Drives More Emphasis on Reliability
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2014
Merchant Silicon Power in Networking Applications • Power increases more than seven times after the year 2000
• Power cycling trends in networking applications
© 2015 by Honeywell International Inc. All rights reserved.
TIMs – Crucial for Thermal Management • Product Performance -
Increasing power densities High density board layout Higher Device Temperatures Lower Thermal Impedance Increased Thermal Stability and Reliability - Harsher Test Conditions
• Customer Satisfaction
- Reliable product performance for demanding users • Result of Incorrect TIM
- Device failure and performance degradation
© 2015 by Honeywell International Inc. All rights reserved.
Real Potential to Impact Customer Satisfaction and Brand
© 2015 by Honeywell International Inc. All rights reserved.
Thermal Management Challenges, Needs & Criteria
© 2015 by Honeywell International Inc. All rights reserved.
Key Thermal Properties of TIM Bulk Thermal Conductivity (W/mK)
Thermal Impedance (°C.cm2/W)
• Material property only • Does not consider: - Interface contact resistance - Bond line thickness
• Thermal bulk resistance + interface contact resistance • Bond line thickness
Heat Spreader Heat Sink
RTIM
∆T q = kA ∆x ∆T TI = A q k:
thermal conductivity
∆x:
thickness of sample
∆T:
temperature difference across sample
A:
cross-sectional area of sample
TIM
IC
Rc2 BLT RTIM = KTIM
BLT
Rc1
TIM Thermal Impedance: TIT = BLT/K + RC TIT BLT K RC
= Total Thermal Impedance = Bond Line Thickness of TIM = Bulk Thermal Conductivity of TIM = Thermal Contact Resistance at the Interfaces
© 2015 by Honeywell International Inc. All rights reserved.
Thermal Impedance Most Critical to Thermal Dissipation and Performance © 2015 by Honeywell International Inc. All rights reserved.
TIMs - Thermal Needs and Requirements #
Customer Need
Measure
Test Method
1
Thermal Performance
Thermal Conductivity (W/mK) Thermal impedance (TI, oC.cm2/W)
Thermal Bulk Conductivity TTV, Laser Flash ASTM E1461 Cut Bar TI Test ASTM D5470
2
“Out-of-Box” Performance @ Time 0; Withstand Temp Spikes and Bursts
Thermal impedance (TI, oC.cm2/W)
TTV, Laser Flash ASTM E1461; Cut Bar TI Test ASTM D5470
3
Longevity
1mm) than other TIMs and designed to have good compression properties
• provide low thermal resistance for applications that do not require long term reliability and thermal shock
• however, they usually can not deliver the same level of thermal performance as other TIM materials
Metallic • all-metal (e.g., solder) or utilize a metal matrix or binder to which metallic or nonmetallic fillers have been added • good thermal conductivity but normally contact resistance or surface wetting is not good
Thermal Gel
TIM Solution
• normally is one-component, crosslinked or pre-cured gel structure • good compressibility and dispense process automation
Thermal Adhesives
Phase Change Material (PCM)
• one or two-part crosslinkable materials based on epoxies or silicones
• transforms from a solid state to a liquid or gel state
• known for their structural support this can eliminate the need for mechanical clamps, but cure time is required and they are not reworkable
© 2015 by Honeywell International Inc. All rights reserved.
Others • thermal compound, tapes, films, epoxy, etc.
• no bleed out, pump out and degradation issues normally found in thermal greases
Greases in Power Cycling Applications • Greases - Subject to thermal expansion of the heat sink and ASIC lid during power cycling - Can cause pump out and result in dry-out scenarios of the interface between the heat sink and the chip
Name of Sensor Chip 1 Chip 2 Chip 3 Chip 4
Grease Application 91.0 92.0 98.0 100.0
Phase Change Application 92.0 91.2 97.5 99.0
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PCM Can Provide Equal Thermal Performance as Grease w/o Issue
© 2015 by Honeywell International Inc. All rights reserved.
Illustration of Pump Out
Grease pump out and creation of voids Phase change application forming a continuous interface between heat sink and ASIC lid © 2015 by Honeywell International Inc. All rights reserved.
Theoretical Curve: PCM Viscosity vs. Temp.
Solid
Liquid/gel state
Viscosity
• Optimal Surface wetting • Low Contact Resistance • Low Thermal Impedance
Melt temp 45 °C
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Increasing Temperature
PCM Polymer • Higher Molecular Weight
- Structural integrity • Long Chain Polymer Structure Grease
PCM
vs.
• Long Chain • Stable and Consistent Filler • Minimizes Filler Migration / Separation Over Accelerated Life Test (HTB, Temp Cycle)
• Short Chain • Good ‘Flow-ability’, Wetting but… • Potential for Migration, Dry-Out and Pump-Out Issues
© 2015 by Honeywell International Inc. All rights reserved.
PCM Polymer Structure Enables Reliable, Long-Term Performance
© 2015 by Honeywell International Inc. All rights reserved.
PCM Technology • Fundamentally three primary components in PCM • Each are vital to robust polymer matrix integrity and filler optimization
Thermal Filler
• Filler TIM Performance and Reliability
- Thermal
• Wax/Polymer - Structural integrity Additives
• Additives - Cross linking
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PCM Formulation is Critical to Performance
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Wax/ Polymer
Thermal Cycle (-55 °C to 125 °C) vs. Grease
PCM vs. Silicone Grease
Honeywell PCM Silicone Grease
Initial
1000 cycles
Honeywell PCM
Silicone Grease
Grease breaks down Thermal Cycling Test Condition:
2.00 1.80 1.60 1.40 1.20 1.00 0.80 0.60 0.40 0.20 0.00
1.78
0.09 0.12 Initial
0.11 Baking 400 Hr
Grease TI degrades
• -55°Cx10min + 125°Cx10 min, for 500 to 1000 cycles • Sandwich PCM & grease between aluminum and glass plates set at 200μm gap • TI Test : ASTM D5470 © 2015 by Honeywell International Inc. All rights reserved.
PCM Provides Stable Polymer Structure with No Pump-Out Issue
© 2015 by Honeywell International Inc. All rights reserved.
Thermal Reliability: PCM vs. Silicone Greases High Temperature Soak at 150 °C TI vs. Hours of Exposure
Thermal Impedance (°C-cm2/W)
1.20
1.00
0.80 PTM3180 0.60
Grease A Grease B
0.40
0.20
0.00 0
200
400
600
800
1000
Hours Test Condition: 150°C continuous baking Test Method: Laser Flash, ASTM E1461 © 2015 by Honeywell International Inc. All rights reserved.
Significantly Better Reliability Than Silicone Grease
© 2015 by Honeywell International Inc. All rights reserved.
Extended Reliability - PCM • Thermal Stability >3000 hrs @ 150°C • HAST > 192hrs@ 130°C/85%RH • Superior Reliability
HAST TI vs. Time
ASTM E1461
High Temperature Baking TI vs. Time
>10% deviation of thermal impedance indicates end of reliability life
ASTM E1461
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Polymer Chemistry Enables Improved Reliability
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Improved Thermal Impedance - PCM • Lower Thermal Impedance: