Manufacturing technologies
Power device, EV/HEV car, Drone, Aerospace, 5G/6G communication

Development of power module thermal evaluation and structuralreliability evaluation system using SiC heater chip
Flexible 3D System Integration Laboratory, SANKEN (The Institute of Scientific and Industrial Science)Specially Appointed Associate Professor Chuantong Chen

https://researchmap.jp/chenchuantong

Specially Appointed Professor Katsuaki Suganuma

https://researchmap.jp/ksuganuma

Abstract
Despite the rapid progression of silicon carbide (SiC)power devices, thethermal characteristic evaluation during power cycling at high temperature (>200 °C) is an issue. In this study, a fast and miniaturized evaluation
system with online thermal characteristic measurement function was introduced by an n-doped 4H SiC thermal engineering group (TEG) chip. Online thermal resistance measurement of a power module structure by Ag
sinter joining with micron/submicron Ag particles paste in low temperature,
low pressure, and cooling system by a thermal interface material bonding
was performed. High-temperature reliability was systemically investigatedby power cycling tests by switching ON/OFF the power source which isconnected to the SiC-TEG chip by Au wires. The total thermal resistance ofthe power module from the SiC-TEG chip to the cooling system increased
from 0.5 to 0.53 K/W with the enhanced power source, and remained
almost same after 20 000 power cycling at a swing temperature ΔTj of
150 °C. Furthermore, the SiC-TEG power module structure with the die
attached with Pb and Pb-free solders, alongwith the same power source
as sinter Ag paste was also measured. The Ag sinter joint possesses thelowest thermal resistance and highest high temperature reliability during
power cycling compared with Pb and Pb-free die-attach materials.

the sinter Ag joint possesses the lowest thermal resistance and highest
high-temperature reliability during power cycling compared with Pb andPb-free die attach materials.

▍ Significance of the research and Future perspective
This study proves the possibility of a precise measurement method of
the junction temperature and thermal resistance at high power density,
which is no longer limited by the actual SiC direct bonded power module structure. This technology can be extended to perform reliability teststandardization for all WBG semiconductors by providing a method thatcan record the information of the thermal and electrical properties online,
but with a fast and miniaturized evaluation system. The SiC-TEG technology can benefit the controlled and site-specific power conversion industries
and may lead to new avenues for power electronics design with the capability to perform well at increased junction temperature.

Manufacturing technologies▍ Background & Results
In power electronics, the greatest aspect of power loss during the power
conversion process depends on the performance of the semiconductor devices. To improve this limitation of conventional silicon (Si)-based power devices, wide-bandgap (WBG) semiconductors such as silicon carbide (SiC)
and gallium nitride (GaN) have been introduced and have revolutionized
the power electronics components. Until now, the measurement of thermal
resistance characteristics and power cycling reliability for power module
structures such as SiC MOSFETs require two equipment systems. One is
the power cycling system and the other is the transient thermal resistancemeasurement mechanism (T3Ster). The T3Ster is applied to understanding package thermal metrics and structure, calibration of thermal simulation models, reliability, and quality assessment, which can detect failure
phenomenon nondestructively. For example, failures have been reported
in structures around semiconductor chips, joint structures of chip-substrate-metal base plate and in joint structures. However, both systems are
expensive and need large space, due to which it has been difficult to apply
in a wide range of applications in the power electronics domain. Most importantly, to measure the thermal resistance by T3Ster, the power cycling
test must be stopped, which means that online thermal characteristic measurement of the power module structure during power cycling is impossible.
Usually it is needed to stop the power cycling test many times to obtain thechange of the thermal resistance and failure conditions, which influences
the measurement accuracy itself. Hence, a fast and miniaturized evaluation
system with online thermal resistance record functioning is needed.
In this study, we present a significant advance in the measurement ofthermal resistance through the junction temperature during the operation ofan assembled SiC power module structure, where the thermal resistancecan be measured online by using a thermal test engineering group (TEG)
chip at the first instance. The junction temperature and temperature distribution of the SiC-TEG chip with input power was analyzed by experimentand simulation. The results show that SiC-TEG can accurately evaluate
the thermal characteristics with different die attach materials. Additionally,Figure 1 (a) the SEM image of SiC heater chip, (b) Temperature distribution of SiC heater
chip attached on DBC substrate by Ag sinter paste joining in the case of the power source
being ON by finite element simulation. (c) Temperature distribution in the vertical direction.

Figure 2 (a) Measurement system of thermal property characterization and Power source
electrode applied on the DBC substrate. (b) Schematic diagram of the thermal characterization evaluation system of the SiC heater chip die-attached structure, (c) SEM image ofthe cross section of SiC heater chip connected to the DBC by Ag sinter paste joining. (d)Change of thermal resistance of the die-attached structures by various solders and Ag
sinter paste joining during power cycling.

P a t e n t
Kim, Dongjin; Nagao, Shijo; Chen, Chuantong et al. Online thermal resistance and reliability characteristic monitoring of power modules with Ag sinterT r e a t i s e joining and Pb, Pb-free solders during power cycling test by SiC TEG chip. IEEE Transactions on Power Electronics. 2021, 36(5) pp. 4977-4990,
doi: 10.1109/TPEL.2020.3031670
URL
K e y w o r d power electronics, SiC heater chip, thermal resistance measurement, Ag sinter joining