What thermal grease precautions should we be aware of?

While thermal grease promotes thermal conduction to a fin, it has a thermal capacity itself. Applying too much grease will obstruct the heat radiation to fins. At the same time, applying too little will increase the contact thermal resistance because thermal grease will not have good contact in some spots between the fins and module […]

How should thermal grease (compound) be applied on an IGBT module?

Thermal grease can be applied using either a roller or stencil mask. An inappropriate thermal grease thickness will negatively affect heat radiation to the heat sink. We strongly recommend using a stencil mask that enables a uniform thickness to be applied over the back surface of the module. For details on application methods, refer to […]

Is there a recommended thermal grease that should be used?

Refer to Application Manual Chapter 6-3.3 for details.

What are the recommended thermal conductivity and thickness for thermal grease?

Recommended values are 0.92 W/m·K or higher for thermal conductivity, and approximately 100 μm thick after spreading thermal grease. For details, refer to Application Manual Chapter 6-3.3 or Mounting Instruction.

Can we apply an IGBT module directly to a heat sink?

No, prior to using an IGBT module, please apply thermal grease (compound) on the surface of a heat sink and module before layering. This will reduce the contact thermal resistance. For details, refer to Application Manual Chapter 6-3.3 or Mounting Instruction.

Where are the chips located internally?

Please contact Fuji Electric Corp. of America or your local sales representative or distributor to answer your question.

How do I measure the case temperature (Tc) for an IGBT module?

The following illustrates an example of how to measure case temperature (Tc). One method is to make a groove on a copper base or a heat sink of an IGBT module to embed a thermocouple. Please fill the groove with highly thermally conductive paste to secure the thermocouple and attain even thermal diffusion.

What is the difference between Tj(max) and Tj(op)?

The maximum allowable temperature for the chip during conventional continuous operation is specified in Tj(op). Please ensure the maximum chip temperature stays at or under Tj(op) during conventional continuous operation. The maximum allowable temperature for a chip during short-term overload or abnormal operation is specified inTj(max).

How do I estimate the junction temperature (Tj)?

Junction temperature can be estimated based on generated losses and thermal resistance Rth(j-c). For details, refer to Application Manual Chapter 6-2.1. We provide a free software to calculate IGBT’s temperature at 2-level inverter, 3-level inverter, and chopper circuits. This software can be downloaded here.

What is the acceptable range of case temperature (Tc) for an IGBT module?

Refer to the “Maximum Ratings: Case temperature” section in the data sheet.