Wettable flank routable thin MicroLeadFrame for automotive applications

Abstract

Driven by the higher power density and harsh environments in automotive, leadframe package has been varied to meet the higher requirement of reliability and integration. Quad Flat No-Lead (QFN) packages is known to provide the small form factor, and adequate for the high power package system. However, due to its wet pad characteristics, the solder volume is thin without fillet endangering the structural reliability. Therefore, it is very important to ensure structural integrity by constructing sound solder fillet, and it is mandatory for industry to inspect visually the soldering state after the bonding process. Wettable flank QFN is designed for this particular purpose. In this study, the routable thin MicroLeadFrame®, an wettable flank technology which allows easy process by employing chemical etching yet enables the side solder visible inspection for fine lead pitch, is introduced and explored. Process to achieve the wettable flank structure was developed, and the reliability was studied through Automotive Electronics Council (AEC) reliability test under package level and board level. Also, mechanical shear test and simulation was carries out to verify the wettable flank structure feasibility to the automotive electronics packaging by demonstrating excellent reliability performances.