Plastic packaging for high temperature applications

More and more applications in microelectronics as automotive, industrial, oil drilling industry or power electronics demand packaging solutions for reliable high temperature packaging with remaining low costs. Widen the application range of plastic packages by using advanced polymer materials and optimizing material combinations and interfaces could be one answer to these requirements. Typical scenario for the integration of electronics into automotive applications is a control unit in the engine compartment, where typical ambient temperatures are around 150°C, package junction temperatures may range from 175°C to 200°C and peak temperature may exceed these values. If low cost packages and technologies as e.g. BGA, QFN, Chip On Board or Flip Chip are used under harsh environment conditions, it is clear that especially the polymeric materials, i.e. Epoxy Molding Compounds, Die Attach adhesive, underfiller, solder mask or the organic substrate base material, are challenged. Generally the development goal for die attach materials and encapsulants compatible with high temperature applications are materials with high Tg and low degradation even at temperatures > 200°C. In this paper material analysis is performed to study the material degradation and temperature depending thermo-mechanical and adhesion properties of state-of-the-art as well as new advanced encapsulation materials. Beneath standard degradation analyzing techniques as thermo-gravimetry dielectric spectroscopy is introduced as an analyzing tool for process and package related degradation studies. As an advanced packaging example the high temperature potential of Flip Chip assemblies on low lost substrates is investigated, Typically Flip Chip assemblies are only investigated up to cycling temperatures of 125°C, sometimes up to 150°C. This study widens the temperature range up to 175°C. Additional to standard capillary underfill materials transfer molding compounds for Flip Chip encapsulations are discussed. Extensive failure and material analysis allows the estimation of reliability potential of Flip Chip assemblies for harsh environment use. In summary a status of the high temperature potential of state-of-the-art die attach and encapsulation materials is given and an outlook on future demands and developments is provided