Adhesion Characteristics of Epoxy Molding Compound and Copper Leadframe Interface: Impact of Environmental Reliability Stresses

Delamination at the mold compound and leadframe interface is the most common failure mode observed during processing and qualification of the microelectronic package. Mold compound to leadframe delamination is typically observed after environmental reliability stresses like: moisture preconditioning and reflow, air-to-air thermal cycling, biased highly accelerated stress etc. Leadframe based packages constitutes majority of microelectronic packages that are manufactured today, which makes mold compound/leadframe interface of great interest requiring thorough understanding of the adhesion characteristics and its evolution as a function of reliability stresses. This study used four-point bend testing to evaluate the adhesion strength of commercially available mold compound to bare copper and silver plated copper leadframes exposed to automotive grade environmental stresses. Results show that adhesion of mold compound to silver plated leadframes is significantly lower than adhesion to bare copper leadframes. Results obtained from this study can be used to carefully select the qualification reliability stresses to prevent overstressing the package and causing failures related to wire bond cracking, delamination etc., which have significant time and cost implications. Finite element simulations were also performed to validate the empirical adhesion test results and can be extended to full package level models to enable delamination prediction.

Investigation of Uncertainty Sources of Piezoresistive Silicon Based Stress Sensor

The aim of this paper is to get insight into measurement uncertainties for thermomechanical measurements performed using a piezoresistive silicon-based stress sensor in a standard microelectronic package. All used sensors have the same construction, were produced in the same technological processes at the same time, yet the measurement results show significant distribution. The possible causes for this phenomenon are discussed in this paper. Additionally, Finite Element Method (FEM) model is created and validated, what enables a study of sensitive parameters influencing the measurement uncertainties.

Influence of Ti Layer on the Structure and Properties of Al/Cu Thin Film

Titanium and aluminum films were deposited on oxygen-free copper substrates by electron beam evaporation method to obtain Al/Cu and Al/Ti/Cu layer composites. Evolution of microstructure and properties of Al/Cu and Al/Ti/Cu thin film during heat treatment processes were investigated by XRD, SEM and electrical properties analysis. The introduce of Ti layer can prevent the formation of Cu-Al intermetallic compounds, and has no obvious influence on the electrical resistivity of Al/Cu thin film, which can be used as a pad in microelectronic package and devices.