Thermal Considerations
Power modules operate in a variety of thermal environments;
however, sufficient cooling should be provided to help ensure
reliable operation.
Considerations include ambient temperature, airflow, module power
dissipation, and the need for increased reliability. A reduction in the
operating temperature of the module will result in an increase in
reliability. The thermal data presented here is based on physical
measurements taken in a wind tunnel The test set-up is shown in
Figure 53. The preferred airflow direction for the module is in Figure
54.
Figure 53. Thermal Test Set-up.
The thermal reference point, Tref used in the specifications of
thermal derating curves is shown in Figure 54. For reliable operation
this temperature should not exceed 120ºC.
The output power of the module should not exceed the rated power
of the module (Vo,set x Io,max).
Please refer to the Application Note “Thermal Characterization
Process For Open-Frame Board-Mounted Power Modules” for a
detailed discussion of thermal aspects including maximum device
temperatures.
Figure 54. Tref Temperature measurement location.
Post solder Cleaning and Drying Considerations
Post solder cleaning is usually the final circuit-board assembly
process prior to electrical board testing. The result of inadequate
cleaning and drying can affect both the reliability of a power module
and the testability of the finished circuit-board assembly. For
guidance on appropriate soldering, cleaning and drying procedures,
refer to Board Mounted Power Modules: Soldering and Cleaning
Application Note.
Through-Hole Lead-Free Soldering Information
The RoHS-compliant through-hole products use the SAC (Sn/Ag/Cu)
Pb-free solder and RoHS-compliant components. They are designed
to be processed through single or dual wave soldering machines. The
pins have an RoHS-compliant finish that is compatible with both Pb
and Pb-free wave soldering processes. A maximum preheat rate of
3C/s is suggested. The wave preheat process should be such that
the temperature of the power module board is kept below 210C.
For Pb solder, the recommended pot temperature is 260C, while the
Pb-free solder pot is 270C max. Not all RoHS-compliant through-
hole products can be processed with paste-through-hole Pb or Pb-
free reflow process. If additional information is needed, please
consult with your GE technical representative for more details.