Flexible connection for reflow free super fine pitch QFP SMT components

Abstract

Owing to the limitation of the fine pitch and the fine area array assembly, fine pitch package or micro BGA are facing challenges such as miniaturization, high density and assembly problems along with the rapid development of the high-density electronic packaging and surface mount assembly. The major limitation of the fine pitch packages is around 0.3mm. Exceeding this limitation encounters reliability issues for the manufacture of packaging leads, solder pads on PCB and the reflow soldering, especially the interconnection failure, such as bridging, solder ball and cold solder joint. More novel interconnection methods are urgently needed to be found in order to overcome these obstacles. In our work, a conductive silicone rubber used to achieve the electrical interconnection between the packaging leads and solder pads on PCB is studied. The pitch is reduced within 0.1 to 0.05 mm when the interconnection of the conductive silicone rubber is adopted, and the characteristics of the current carrying capacity and the continuity resistance have greatly improved. Thus, the size of the integrated circuit (IC) package can be greatly reduced, and the surface mount density can be greatly increased after using this new interconnection technology.