Bottom leaded plastic (BLP) package: a new design with enhanced solder joint reliability

The ultra-thin and crack free bottom leaded plastic (BLP) package has been developed by LG Semicon mainly for memory devices. The package can be manufactured by the conventional plastic package manufacturing process with an appropriate modification. The BLP package has no lateral leads and this novel leadless design concept provides numerous advantages over the conventional packages. They include: (1) compactness and low profile, (2) higher electrical performance and (3) enhanced thermal performance [2]. These advantages made the current design of the BLP package an optimal choice for many applications. In order to extend its applicability into high-end memory devices, however, the improvement of solder joint reliability of the current BLP package assembly becomes increasingly important. In this paper, an improved design of the BLP package is proposed to enhance the solder joint reliability. Solder joint strains of the current and the proposed designs are evaluated by an experimentally verified 3-D FEM model. The results are used to assess relative reliability of the proposed design. The relative reliability is estimated by the average shear strain of the solder joint, based on the modified Coffin-Manson relationship. The analysis indicates that the proposed design enhances the solder joint reliability nearly three times, compared to the current design. More applications are anticipated with the improved design.