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A Simulation Tool for Thermal Engineering
27th July 2011
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Why thermal model is needed?
Smaller chip reduces parasitic effect.
Less parasitic allows for high frequency with less switching loss.
Efficient high frequency allows further size reduction.
In order to make a smaller and higher power switch, the thermal limit must be pushed back.
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What is thermal impedance
powerTT
Z ambjth
Silicon chip
Solder/Wire
Copper frame
Epoxy
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Foster-equivalent model have a real physical meaning: each RC cell represents the contribution to the thermal impedance of a given part
What is Thermal impedance Foster circuit
4
1
exp1n nn
nth RCtRtZ
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Deliverable of the Our Tool
a universal and simple method of representing the thermal character of a device
Interpret values from datasheet or measurement
The tool would allow a power plot using a SPICE simulator to accurate represent package temperatures.
Employed as vehicle to cross compare techniques.
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Tool Demonstration
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ResultsTemperature response to oscilloscope waveform
0
10
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0
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0 10 20 30 40 50
Input power [W
]Ju
nctio
n Te
mpe
ratu
re [
C]
Time [us]
Junction temperature
Input Power
Temperature Limit
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0%
20%
40%
60%
80%
100%
0
50
100
150
200
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300
1 10 100 1000 10000
Failu
re R
ate
Qua
ntity
in T
est
Test Time (Hours)
5 yr
Temperature Operating Life test underwent using JESD22-A108 standard
Applicationbeneficial of the tool
Controlled lifetime
Reliable performance
Reduced manufacture cost
Reduced maintenance costs
Jc/TeLife
IFR (Intrinsic Failure Rate)low, constant
Useful life period
Wearoutperiod
EFR
Time
Failu
re ra
te
0
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Advantage Related Art benchmark
Supplier BCauer RC networks included in
the datasheet
Supplier DUse two additional pins
for junction temperature from RC networks
Supplier COnline calculator and some
thermal RC networks
Supplier ECauer RC networks included in a apps
note for each part
Supplier AFoster networks RC networks
included in the datasheet
