Specifications

18
Dec. 20
Mitsubishi IPM-series Application Note
8. Installation of power Module
8-1 Installing Capacitor
During switching, voltage is induced in power circuit stray inductance by the high di/dt of the main current. This voltage can
appear on the IPM and cause damage. In order to avoid this problem, guidelines that should be followed in designing the
circuit layout are:
٤
1
Located the smoothing capacitor as close as possible to the IPM
٤
2
Use ceramic capacitor near the IPM to bypass high frequency current
٤
3
Adopt low impedance electrolytic capacitor as smoothing capacitor
٤
4
Use snubber circuit to absorb surge voltage
٤
5
Decrease switching speed in order to lower di/dt.
٤
2
and ٤
5
are the most effective to reduce surge voltage. The stray inductance of snubber circuit generally is not
considered to avoid complicating the circuit. In addition, combination of ٤
2
, ٤
4
, ٤
5
is needed since there is a limit on the
length of wiring. The bypass capacitor of approach ٤
2
act as a snubber when oscillation is occurring.
L2 small
L2 large
vce
L1 : Stray inductance between the electrolytic capacitor and the IPM.
L2 : S
tray inductance between the filter capacitor and the driver.
L3 : S
tray inductance between the load and the power circuit's output stage
8-2 Installation Hints
When mounting IPM on a heat-sink, uneven mounting can cause the modules ceramic isolation to crack.
To achieve the best thermal radiation effect, the bigger the contact area is, the smaller the thermal resistance is. Heat-sink
should have a surface finish in range of Rz6 ~ Rz12, curvature within 100μm.
Uniform coating of thermal grease between the module and heat-sink can prevent corrosion of contact parts. Select a
compound, which has stable characteristics over the whole operating temperature range and does not change its properties
over the life of the equipment.
Use a uniform coating of thermal interface compound. The thickness of thermal grease should be ranked in 100~200μm
according to the surface finish.
Mounting screws should be tightened by using a torque wrench to the prescribed torque in progressive stages in a cross
pattern. As mentioned before, over torque terminal or mounting screws may result in damage of IPM.
When an electric driver is used, thermal grease with low viscosity is recommended and extra grease must be extruded
before final tightening screws.
* For the recommended torque order for mounting screws referring to "Installation Method" in the section of
"Correct and Safety Use of Power Module"
Note) Maximum torque specifications are provided in device data sheets. The type and quantity of thermal compounds
having an effect on the thermal resistance are determined by consideration of both thermal grease and heat-sink.
Typical value given in datasheet is measured by using thermal grease produced by Shin-Etsu Chemical Co.,Ltd.
(G-746, which has not issued in Shin-Etsu's publications, is almost the same as G-747.)
Load
Smoothing
Snubber
Installation of power Module