UM0969 datasheet(38/46 Pages) STMICROELECTRONICS

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Power losses and dissipation

UM0969

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Doc ID 17665 Rev 2

fundamental) concept of thermal resistance must be considered, which is defined as the

difference in temperature between two closed isothermal surfaces divided by the total power

flow between them, Equation 18.

Equation 18

For semiconductor devices, typically, the important factors are the relation between Tj, IGBT

junction temperature, and a reference temperature, Tx. The selection of a reference point is

arbitrary, but usually the hottest spot on the back of a device, on which a heatsink is

attached, is chosen. This is called junction-to-case thermal resistance, Rφjc. When the

reference point is an ambient temperature, it is called junction-to-ambient thermal

resistance, Rφja. Both thermal resistances are used for the characterization of a device's

thermal performance.

The thermal resistance of the IPM is strictly related to the assembly process/material:

STGIPS10K60A is based on a DBC substrate that guarantees a higher isolation voltage and

an excellent thermal resistance value.

In practical operations, the power loss PD is cyclic and therefore the transient RC equivalent

thermal circuit, see Figure 16 and Table 10 for more details, should be considered. For

pulsed power loss, the thermal capacitance effect delays the rise in junction temperature,

and therefore permits a heavier loading of the IPM.

Figure 16.

Equivalent STGIPS10K60A thermal network (CAUER models)

Table 10.

RC - Cauer STGIPS10K60A thermal network

Value [ºC/W]

Value [W*s/ºC]

0.088

0.32E-3

0.0154

0.63E-3

0.316

0.90E-4

0.395E-2

0.50E-3

0.816

0.50E-2

UM0969 Datasheet(PDF) 38 Page - STMicroelectronics