Hybrid Thermoplast-Thermoset Molding

摘要

For the functional integration of electronics into plastic insert molding and encapsulation technology is required. The fragility of the insert and the thermo-mechanical mismatch of the inorganic and the organic part pose serious limitations to the applicability of the technique. The fragility requires a very gentle molding process which can only be achieved with low viscosity materials. The thermo-mechanical matching requires to fill the polymer with a high percentage of inorganic particles which increases the viscosity. Traditionally, thermosetting materials are used for these reasons. Thermosets, however, suffer from limited mechanical strength and shape accuracy as well as their tendency towards flashing. In applications where mechanical functions need to be integrated this cannot be tolerated. Therefore a hybrid technology is proposed which intends to combine the advantages of both thermosetting and thermoplastic materials and processing. By blending reactive monomers with thermoplastic polymers the viscosity can be tuned to the required level. In order to prevent reaction in the barrel a two-component system is used like in reaction injection molding (RIM). The reaction starts upon mixing of the materials in the runner towards the cavity. Due to the presence of thermoplastic the reaction kinetics of the thermoset changes quite drastically. In the paper the viscosity, diffusion- and reaction kinetics and morphology development will be shown for a model system of PMMA with epoxy (DGEBA-MDA) and the implications will be discussed.