Cool base plates look for hot semiconductors.

The semiconductor components used in the electronics industry produce ever more heat during operation. Efficient cooling asks for high-tech materials from Plansee.

As the operating power increases, so, too, do the demands relating to thermal management in electrical systems. Inadequate cooling considerably impairs the efficiency and reliability of semiconductor components. This is because well over half of all electronic component failures are due to thermal influences. It is much rarer for such failures to be caused by vibrations, moisture, dust or other effects.

What it takes.

 

The thermal design of electronic components is also dependent on the heat flux, that is to say the quantity of heat that has to be reliably dissipated via the available surface area. This problem is exacerbated by the fact that the greatest power dissipation is often concentrated in tiny surface areas of the chip which are known as hotspots. In the components used for power electronics, the local heat flux can vary from a few hundreds to over 1,000 Watts per square centimeter – at a maximum operating temperature of less than 150 degrees Celsius. By way of comparison: Although heat fluxes of a few kilowatts per square centimeter also occur in rocket nozzles, the temperatures in these applications however climb higher than 2,500 degrees Celsius. By contrast, a hot stovetop ring barely reaches 8 Watts per square centimeter.

The second key question relates to the configuration "hot semiconductor meets cold base plate". If the thermal conductivity and thermal expansion characteristics of the semiconductor and the base plate are not optimally harmonized then undesired distortions to the semiconductor or even damage and subsequent failure are unavoidable. Which, if you look at things the other way round, means: The better harmonized the properties are, the better the semiconductor module is to withstand soldering processes involved during manufacture and the temperature cycles that occur during operation.

 

Overall, this means: First of all, the base plate material must provide suitable thermal expansion characteristics that broadly match those of the semiconductor. In addition, the level of the expected heat fluxes is critically important for the choice of a suitable base plate material. The greater the heat fluxes, the better the thermal conductivity of the material must be.

High thermal conductivity meets low thermal expansion.

 

Copper and aluminum are relatively good heat conductors and are in widespread use as heat sinks and contacts in the electronics industry. However, the great drawback lies in their high coefficient of thermal expansion. As a result, these materials are not suitable as base plate material for high-performance semiconductors that are exposed to significant thermal loads.

The refractory metals molybdenum and tungsten are ideally suited for use as the base material due to their low coefficients of thermal expansion. These materials have been used for many years as base plates for power transistors. Composite materials based on molybdenum, tungsten and copper have also been developed for applications with demanding thermal conductivity requirements. The copper content of these composite materials can be specifically adjusted to optimally adapt the thermal properties of the base plate to the complete assembly.

Due to their lower weight, molybdenum-copper composites are particularly suitable for this type of application where every gram counts. For example, in the automotive industry where they are used as carrier plates for the IGBT modules that act as inverters in electric drives.

The ideal material. From us, of course.

 

We manufacture semifinished products as well as components such as heat spreaders, heat sinks and base plates made from for a wide range of thermal management applications in the electronics industry. From the raw material through to the finished, coated component we perform every stage of the production process in-house.

Find out more about our heat spreaders for semiconductor components.