Entwicklung von fluessigkristallinen Polymeren als Mantelmaterial fuer elektronische Bauelemente

A joint research project was directed towards the investigation into the feasibility of substituting currently used thermosetting resins for the encapsulation of electronic components by mouldable thermoplasts. Materials based on liquid crystalline polymers (LCP) appeared to be favourable in view of their excellent flow characteristics, inherent inflammability and mouldability. Initially tested materials derived from BASF developmental LCP exhibited sufficient thermal conductivity and low ion content levels. The additional requirements of stability towards hydrolysis and soldering as well as good welding line strength, however, were met only by blends of LCP with poly(aryletherketone)s (PAEK). Adherence of these materials to lead frame metal surfaces was investigated by a team of the Fraunhofer Institute of Applied Materials Research (FhG-IFAM). A minimised temperature difference between thermoplast melt and mould was recognised to be decisive for good adherence. The structural stability was significantly enhanced by introducing a polyimide layer between thermoplast and lead frame. The developmental materials were evaluated by SIEMENS for direct and indirect (premoulded packaging) sheathing. With direct sheathing using the LCP/PAEK blends ''wire sweeps'' were unavoidable. Promising results were obtained with the same materials under conditions of premoulded packaging techniques, among which heated tool welding proved to be the best suited welding process. High potential of the developed blends in system packaging is expected providing new prospects for the electronics industryAvailable from TIB Hannover: F93B1281+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman