Dielectric Breakdown of in-Package Epoxy Mold Compound under Wet and Dry Conditions: Frequency and Temperature dependence

Epoxy-based molding compounds (EMCs) are highly valued materials in the electronics industry due to their strong resistance to a variety of mechanical, electrical, and environmental stresses. In literature, EMCs were characterized by using thick bulk samples providing interesting indications on their electrical reliability when employed in high humidity, voltage and temperature conditions. However, in-package performance and reliability with thin EMC structures is lacking. In this work, an interdigitated capacitor embedded into a 24-pin Single-Small-Outline (SSO) package is used as a reference test structure. Samples have undergone rigorous realization and preliminary characterization procedures. The features of EMC layers as thin as 15.7μm have been measured up to the dielectric breakdown by applying DC and AC ramp voltages under different humidity, frequency and temperature. Results show that the breakdown strength is higher under DC voltage stress than AC ones. Moreover, the relationship between the breakdown strength and frequency in dry conditions has a statistically significant dependence: the greater the frequency, the lower the breakdown strength. On the contrary, almost no dependency between breakdown strength and temperature has been observed under both wet and dry conditions. The presence of space charge is expected to play a key role in each dependence. Thus, a preliminary TCAD model is proposed to effectively explain the role of space charge formation at different ramp rates.