Encapsulant characterization - valuable tools for process setup and failure analysis

The selection of the optimum material for an encapsulation application can be a challenging task, as typically the datasheets do only provide general information, e.g. CTE below glass transition temperature or Young's modulus at room temperature. The reason is that a full material characterization is rather sumptuous, due to the wide variety of material parameters possibly relevant. There are parameters for process setup and evaluation as rheological behavior and reaction behavior and there are application specific parameters as e.g. thermal conductivity, degradation temperature or media resistance. Therefore the determination and definition of relevant methods and parameters are important as results must be comparable. This is especially true as sample preparation and testing is time and cost intensive. Within the BMBF-sponsored project PUMA, a test schedule was set up to fully characterize various underfill encapsulants and to check relevance of material parameters for process development and package reliability. In summary this paper proposes test methods suited for encapsulant characterization, so material measuring techniques can be homogenized, results are comparable and material selection is facilitated.