A method for the measurement of chip to leadframe adhesion in LOC packages

Adequate die-to-leadframe adhesion is necessary for LOC package integrity during and after manufacturing process. Poor adhesion may result in a variety of defects such as die adhesion failure, marginal wire bond, broken wire, exposed wire at the surface of the plastic encapsulated package, and bent leads, ultimately leading to electrical failure [1,2]. In this paper, a technique to measure the adhesion of leadframes to electronic chips in LOC type packages is described. In this method, the leads on opposite sides of the die are pulled using a universal materials tester (e.g., Instron). We found that sample preparation and measurement equipment set-up were critical to the consistency and repeatability of the measurements. A comparison of measurements on packages bonded with three different materials is presented. Minimum bonding forces required for best yields were determined for these three types of chip-to-leadframe bonding materials. Using this information, we were able to rank materials with respect to their relative adhesion characteristics.