www.corpe.et.aau.dk
Online Junction Temperature Measurements via TSEPs
Nick Baker, Stig Munk-Nielsen, Marco Liserre
Aalborg University
November 21, 2013, Aalborg University, Denmark
Abstract:
The temperature of a power semiconductor device is important for both its optimal operation and reliability. Temperature measurements via thermo-sensitive electrical parameters (TSEP) are
one way to carry out immediate temperature readings on fully packaged devices. However, successful implementation of these techniques during the actual operation of a device has not yet
been achieved. The project aims to characterise and propose methods to determine the temperature of power semiconductor devices based on electrical parameters during the normal
operation of power electronic converters. The scope includes both improvements to existing techniques, as well as the generation of new novel methods for electrical parameter based
temperature measurement.
Why TSEP?
Implementation Issues
ÎThe development of a temperature measurement
system via TSEPs is hindered by a number of
issues
Temperature Estimation using Voltage Drop with slightly varying
current measurement error (Data from IFSTTAR, Versailles)
Current close to 80A Current close to 100A
Current (A)
Estimated temperature
(°C)
79.8
80.2
99.8
100.2
111.2
116
150.5
154
• Calibration requirements
A TSEP can differ from one chip to another despite having the same
temperature and reference, and being from the same manufacturing
process! (eg, Threshold Voltage)
ÎAllow observation of temperature without device
modification
• Other methods usually require direct access to the chips (IR
Camera, Optical Fibres) or embedded internal sensing equipment
• Generally provide an average temperature measurement
• In theory can provide instantaneous temperature measurement
• Have been used for several decades to validate thermal
resistance parameters for datasheets
• However, online use is not well developed – there are several
implementation issues
ÎTSEP Categories
Classical
Static
Characteristics
Saturation Current
Voltage Drop at Low
I(V) Characteristic
Current
(Voltage Drop at High
Current)
Threshold Voltage
Short Circuit Current
Dynamic
Characteristics
Turn-on Delay
Rise Time
Turn-off Delay
IGBT Current Tail
……and several more
Bond Wires create large errors in temperature measurements
via Voltage Drop at High Current when verified with an IR
Camera (data from Perpina, 2006)
• Dependence of electrical parameters on variables other than
temperature
Current measurements need to be very accurate: small error in current
= large error in temperature measurement
Bond wires and packaging introduce large errors in temperature
estimations (bond wire and junction operate at different temperatures)
• Aging/damage influences
Electrical parameters often change throughout the lifetime of a power
module: method is required to discount these aging processes
• Temperature non-uniformity
Average junction temperature measurements are preferred as
they provide opportunity to observe faults such as solder voids
Does the temperature measured via a TSEP accurately represent the
desired temperature distribution in the junction?
Peak due to the void
• Practicality of conducting measurement without interruption to
converter operation
Specialised control strategies may be required, eg temporary increase
of gate resistance
Project Status
•
•
•
•
New TSEP method investigated
Proof of concept in offline conditions
Designing custom gate driver to
perform ‘online’ double pulse tests
Perform verification with Infra-red
Camera