Transcript Why Thermal Management?

Why Thermal Management?
References: Sergent, J., and Krum, A., Thermal Management
Handbook for Electronic Assemblies, McGraw-Hill, 1998
And
Yeh, L.T., and Chu, R.C., Thermal Management of Microelectronic
Equipment: Heat Transfer Theory, Analysis Methods, and Design
Practices, ASME Press, New York, 2002.
Size and Performance Trends
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Higher levels of integration in
semiconductors
More multichip modules
Faster speeds, smaller devices
Leads to both more heat generation and
higher heat densities
Increase in Circuit Complexity
Yeh and Chu, 2002
Major Causes of Electronics Failures
Yeh and Chu, 2002
Types of Failures
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Soft failures: Properties change, changing performance
outside the specs
• Resistors,
capacitors,
transistors, leakage
currents
• Example: bipolar
transistor gain can
change by a factor
of 3 over the
military temperature
range
Sergent and Krum, 1998.
Types of Failures, cont.
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Hard failures: component doesn’t work at
all
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Corrosion, chemical reactions, intermetallic
compound formation
Cracking caused by different coefficient of
thermal expansions
Breakdown of materials
Classification of Temp-Related
Failures
Sergent and Krum, 1998.
Yeh and Chu, 2002
Other common (non-temp-related)
failures
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Due to mechanical interconnections: poor wire bonds,
die bonds, lead frame bonds, etc.; bonds not fully
formed or incompatible materials
Due to manufacturing defects in active devices:
impurities in semiconductors, pinholes in insulating
oxide, etc.
Due to electrical overstress: overstress during operation
or else exposure to electrostatic discharge
Due to chemical reactions: corrosion or formation of
intermetallic compounds; exacerbated by high
temperatures
Designer Reaction to Thermal
Issues
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Two common reactions
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To properly design the system, we need to know
the following
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Underestimate of component temps, resulting in too
little cooling, leading to failure
Overkill – cooling a system much more than needed,
leading to excessive cost and increased size and noise
How and where heat is generated
How to estimate the temperature
How to remove the heat
We’ll focus on these three issues in class!