Thomas Krebs

A breakthrough in power electronics reliability — New die attach and wire bonding materials

Power Electronics on DCB are used for high power devices. There is a wide field of applications for such power electronic devices like converters or inverters for wind mills, solar parks or for electric and hybrid vehicles. High efficiency, long life time and increased power density are the major technical requirements for those devices. Especially the life time, but also the power density are limited by die attach and wire bond materials. New material solutions to overcome these limitations in life time will be discussed in this paper. Results of an active power cycling test of DCB devices supported by the failure analysis and material data will be used to demonstrate and explain the novel materials advantages versus conventional solutions.

Novel interconnect materials for high reliability power converters with operation temperatures above 150°C

Power semiconductor modules are used in a wide field of applications and power ranges. Two common trends for these devices are miniaturization and cost reduction, leading to new requirements for dies, substrates and interconnect materials. As a result, the power density and therefore the operation temperature in the devices rise, creating the need for new interconnect materials. These materials must have high thermal and electrical conductivity to ensure excellent heat dissipation and thermo-mechanical stability. Consequently, the device operation temperature, which is currently limited to maximum 150°C, can be increased and the reliability of the module can be improved. The novel mAgic sinter materials feature highest thermal and electrical conductivity and can be used for operation temperatures above 150°C. This new material family provides a solution to reduce size and cost of high power semiconductor modules and, at the same time, improves the overall performance and reliability of these packages.

Sinter adhesive - new horizons in semiconductor packaging

Conductive adhesives provide advantageous properties for many electronics assembly applications (low processing temperatures, high flexibility) and they are green materials. However, the limited electrical and thermal conductivity of conventional conductive adhesives restrict their usage in most cases to low to medium power density packages. The novel mAgic silver sinter adhesives feature the conventional positive properties of conductive adhesives and combine them with electrical and thermal conductivity that are comparable to solder. This new development therefore provides solutions to the growing challenge of increasing power densities related to shrinkage of packages and / or increase of power.

Comparison of Thermal Measurement Methods of Die Attach Materials Used in Power Electronic Modules

Because of a rapid growth of worldwide energy consumption an economical use of power is a necessity to ensure the supply reliability. One key technology to realize sparing energy use is power electronics. The cost of power electronic devices became an important aspect in this application due to its broader use compared to the past. In recent years, high efficiency at a given lifetime with low system costs are the main focus for the development of power electronic system. To shorten development and qualification time of such systems simulation of electrical and thermal performance is done extensively in order to optimize cost, life time and efficiency of the device. The thermal resistance of the modules and in consequence the thermal resistance of the interconnect materials are important factors of the performance of such systems. The paper discusses different thermal conductivity measurements and die attach materials and substrate materials, along with the measurements with a package like system, containing the die attach material itself as well as interfaces of the die attach material to the die and the substrate. Different measurement methods available to determine the thermal performance in such a system. Some examples are the thermal diffusivity and the junction to case thermal resistance measurement. Measured and simulated values were compared and discussed.