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Thermal paste application service is said to guarantee high and reproducible quality

18th July 2007

Semikron Ltd

ES Admin

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SEMIKRON has increased its portfolio of technical and logistics services to include the application of thermal paste to power modules. The introduction of this new service sets SEMIKRON apart from other power semiconductor manufacturers, by enabling it to offer a high and reproducible level of quality. The optimum application of thermal paste onto the semiconductor module ensures good thermal performance once the module is assembled on the heat sink. Too much paste reduces the thermal impedance and can in extreme cases lead to cracking in the insulating ceramic substrate during assembly. Too little paste results in thermal overload of the power semiconductor, which shortens module service life.

Thermal paste is normally applied by using a printing processes or a sponge rubber roller. The manual rolling process is not reproducible, which means that quality control is very difficult. Printing processes produce reproducible results, but require costly purpose-built tools. Therefore, it makes good sense for the manufacturer of the power module to apply the thermal paste layer using this technique, because it can provide a controlled quality and offer the service at an attractive price, as a result of large production volumes.

Over the last ten years, SEMIKRON has developed a volume-production-viable thermal paste application process for semiconductor modules. It has now added this automatic screen-printing process to its service portfolio. The thermal paste layer thickness is module-specific and is monitored using Six Sigma tools. The application process boasts an accuracy of +/-10µm. With such properties, the process fully meets the requirements for power semiconductor modules.

Modules with a thermal paste layer are transported in purpose-built patented blister packaging, which guarantees contact-free transportation. Modules can be stored in these blisters for up to 18 months. The storage properties of SEMIKRON blisters were tested in high-temperature, low-temperature, warm, moist and humid conditions with subsequent thermal resistance and power cycling tests.

Once the modules reach the customer, they can be simply removed from their packaging and placed onto the heat sink. Heat sink assembly to the module is therefore a quick and straightforward procedure. Production workers do not come into contact with the thermal paste, which means there is no risk of thermal paste being carried over into production.

SEMIKRON has initially introduced thermal paste application as an optional additional service for its MiniSKiiP product family. Greater capacity is currently being created to enable the company to increase the print volume over the coming years to as many as 2 million modules per year. Thermal paste application will soon be available as an optional service for the standard bipolar SEMIPACK range.