BDTIC AN2010-02 www.BDTIC.com/infineon Technical Information

Application Note, V1.0, 2010
AN2010-02
Technical Information
IGBT modules
BDTIC
Use of Power Cycling curves for IGBT 4
Industrial Power
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Autor: Hubert Ludwig IFAG IMM INP TM
BDTIC
Edition 2010-02-22
Published by
Infineon Technologies AG
59568 Warstein, Germany
© Infineon Technologies AG 2010.
All Rights Reserved.
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AN2010-02
Use of Power Cycling Curves
Use of Power Cycling Curves for IGBT4 modules
In the application very different cycles with different thermal conditions are
superimposed. Power Cycling is a common procedure to investigate the reliability
of power electronic devices, especially power modules.
The IGBT module has a power cycle life as shown in the diagrams of the
Reliability specification. The usage of IGBT modules mustn’t exceed the limits
defined by it’s power cycling life.
Definitions of cycling conditions:
There are two types of power cycle life, the ∆Tvj power cycle and the ∆TC power
cycle. The latter is well known also as active Thermal Cycling (TC).
The Thermal Cycling raises and lowers the case temperature at relatively long
intervals of time (minutes). It is mainly carried out to evaluate the soldered joints
between DCB substrate and module baseplate. Active Thermal Cycling is
equivalent to PCmin. (Power Cycling with cycle time of typically 1 minute duration)
The standard Power Cycling (PCsec.) raises and lowers the chip junction
temperature at relatively short intervals of time (seconds). It is mainly carried out to
evaluate the useful life of the bond wires on the silicon chips and the soldered
joints under the silicon chips.
Power Cycling capability of power semiconductor modules is dependent on
absolute junction temperature (Tvj), the temperature swing (∆Tvj) and the duration
(tcyc , ton) of the power cycle. During the Power Cycling test the same conditions,
such as load current, Tvjmax etc. are periodically repeated.
BDTIC
Definition of Tvj
The junction temperature Tvj is the temperature in the junction region of a
semiconductor chip. Because the junction temperature can only be
determined either by indirect measurement or calculation it is more correctly
termed “virtual junction temperature”.
Definition of Tvj max
The maximum junction temperature Tvjmax is the maximum allowable
temperature value that may be reached during the temperature cycle for the
specified curve in the Power Cycling capability diagram for modules. The
higher the maximum junction temperature Tvjmax , the higher is the stress to
the device which results in a reduced number of cycles.
Definition of ton
The time period ton is the period where power losses are generated in the
device which results in a steady temperature rise of Tvj. (e.g. drive /
acceleration phase of a motor drive.) The longer the on period ton the higher
is the stress to the device which results in a reduced number of cycles. This
can be explained by higher viscoplastic deformation energy in the material
layers that undergo thermomechanical cycling for higher on period ton.
Typical ton time in Power Cycling tests is 1,5s.
Application Note
3
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V1.0, 2010-02-15
AN2010-02
Use of Power Cycling Curves
Definition of toff
The time period toff is the period without load. It is adjusted so that the
temperature Tj goes back to the level before heating. Therefore the typical
toff time is 1,5s
Definition of tcyc
The time period tcyc is the period of one power cyle. It is the time of ton + toff.
Typical tcyc time in Power Cycling tests is 3s.
Use of Power Cycling curves for IGBT4 modules
The Reliability specification “Power Cycling capability for modules rated at
Tvjop max =150°C” shows the cycling capability versus the temperature rise for
a power cycling stress at different maximum junction temperature values
Tvjmax. The Reliability specification “Power Cycling capability: typ.
dependence on ton” shows the influence on the cycling capability by
variation of ton.
BDTIC
Application example 1:
The PrimePACKTM module type FF900R12IE4 is used in a motor drive
inverter with intermittent operation, a load (on) period of 10s and a cycle
time of 60s. The load leads to a junction temperature rise from 85°C up
125°C in the IGBT. This means a junction temperature swing of ∆Tvj=40K.
Power Cycling Capability for Modules rated at Tvj op,max=150°C
IGBT4 1200V / 1700V Industrial Modules
issued 2009-12-21; rev2
1,0E+10
IGBT4 : Tvj,max=100°C
IGBT4 : Tvj,max=125°C
IGBT4 : Tvj,max=150°C
1,0E+09
450 Mill
No. of cycles
Diagram1:
cycle time:
ttcyc
typ.
3s
3,0s
cyc≤
1,0E+08
ton= 1,5s
temperature level:
Tvj,max=100°C
Tvj,max=125°C
Tvj,max=150°C
(see inset)
1,0E+07
2,3 Mill
1,0E+06
1,0E+05
dashed line: estimated
1,0E+04
20
10
∆ Tvj [K]
40
100
Power Cycling Capability : typ. dependance on ton
IGBT4 Industrial Modules rated at Tvj,opmax=150°C
issued 2009-12-14; rev 2
10
Diagram 2:
Ncycles [normalized]
analytical description:
N cyc (ton )
 t 
=  on 
N cyc (1,5s)  1,5s 
−0 , 3
disclaimer:
Ncyc=f(ton)behaviour is only
applicable if other
impact parameters
(I, Tvjmax, ∆T
∆Tvj) are
kept constant
, 0,1s < ton < 60 s
1,39
1
0,57
0,1
Application Note
0,1
0,5
1
4
10
100
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ton [s]
V1.0, 2010-02-15
AN2010-02
Use of Power Cycling Curves
From diagram1 at ∆Tvj=40K and Tvjmax=125°C one obtains the number of
cycles of 2,3Million. Because of the load period ton=10s, the value has to be
multiplied with the correlation factor 0,57 from diagram 2. This results in a
life time of 1,3 million power cycles.
At continuous operation and a cycle time of 60s, it can be expected to have
a life time of 21.600 operation hours under this application conditions.
Application example 2:
The PrimePACKTM module type FF900R12IE4 is used in a motor drive
inverter with intermittent operation and different load conditions per cycle.
The first load (on) period of 10s leads to a junction temperature rise from
85°C up 125°C in the IGBT. The further 3 load (on) periods of 0,5s leads to
a junction temperature rise from 85°C up 105°C in the IGBT. The off period
between each load period is more than 2s. The cycle time of this load train
is 60s.
BDTIC
load
1
2
3
4
1
t
cycle time
This means a junction temperature swing of ∆Tvj=40K once per cycle and 3
times a swing of ∆Tvj=20K per cycle. From diagram1 one gets at ∆Tvj=40K
and Tvjmax=125°C the number of cycles of 2,3Million. Because of the load
period ton=10s, the value has to be multiplied with the correlation factor 0,57
from diagram 2. This would result in a life time of 1,3 million power cycles.
But the further load periods have also to be considered. From diagram1 at
∆Tvj=20K and Tvjmax=105°C one gets the number of 450Million cycles. With a
load period ton=0,5s the value has to be multiplied with the correlation factor
1,39 from diagram 2. This would result in an estimated life time of 626
million power cycles.
Because each load pulse uses lifetime, the total number of cycles for this
load train of 4 pulses per cycle has to be calculated by the following formula.
N cycle =
Application Note
1
1
1
1
1
+
+
+
N1 N 2 N 3 N 4
5
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V1.0, 2010-02-15
AN2010-02
Use of Power Cycling Curves
With the above values this results in an estimated life time of
N cycle =
1
1
1
1
1
+
+
+
1,3 626 626 626
= 1,294Mill.cycles
At continuous operation with a cycle time of 60s, a life time of 21.560
operation hours can be expected under this application conditions.
In this application example it can be seen, that 99,4% of the total lifetime is
used from the first load with the high temperature swing and only 0,6% from
the 3 further load periods with lower temperature swing.
BDTIC
The below table shows an overview of the values from this example:
Power Cycling Application example 2
load
∆ tvj
[K]
from
diagram 1
tvj max cycles at
ton=1,5s
[°C]
1
2 to 4
40
20
125
105
2,30E+06
4,50E+08
from
diagram 2
ton[s] correlation cycles at
factor
ton
10
0,5
0,57
1,39
1,30E+06
6,26E+08
no of
estimated total used life total cycle estimated
loads per allowed load
time
time [s] total lifetime
cycle
cycle numbers
[operation h]
1
3
99,38%
0,62%
1,294E+06
60
2,156E+04
Important note:
Exceeding the specified values means operation out of the
specification. This can lead to a failure of the device!
Application Note
6
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V1.0, 2010-02-15