Study of a Failure of a Compact Ceramic No-Lead Package Due to Tinning Induced Thermal Shock and Its Design Improvement

A Novel ceramic flat no-lead (CFN) package dual-output LDO IC which has two high-power channels was developed. After being put into mass-production, several board-level failures were found. A couple of analyses including X-ray and metallurgical microscope detection had been carried out on the failed component. The root cause of the failure was a tiny crack on the package body which was caused by the thermal shock during pre-mount tinning process. After studying the failed case and the initial package design details, the design defects were found on the package structure. The weakness of the package was discussed. Then several design improvements on the package structure have been made. And FEM simulation showed the improvements made the package adapted to the tinning process. Finally, experiments were carried out the verify the effectiveness of the new design.