The aluminum bond-pad corrosion in small outline packaged devices

Owing to the restrictions on the properties of packaging materials, the dimensions of devices and the operative (testing) conditions, small outline plastic packages show higher failure rates than do other types of packages. Although the factors resulting in corrosion are variable for various types of packages, the corrosion of aluminum bond-pads is the major failure mode on the chip surface. The steps of reliability test are discussed and inspected by various analytical methods to investigate the corrosion in the 16 pins small outline packaged devices. The sources of corrosive ions are attributed not only to the out diffusion of corrosive species from epoxy molding compounds but also to the contaminants associated with the steps in the assembly process. Each of the assembly processes and steps in the reliability test are examined to determine the decisive step causing the delamination. Both the fluorescein ingress test and cross-section inspection are used to investigate the most probable transporting path of moisture. Finally, of particular interest in the diffusive paths of corrosive components, the sources of corrosive ions and the reaction mechanisms of corrosion can be revealed in detail.