Manufacturability Reliability Challenges with Leadless Near Chip Scale (LNCSP) Packages in Pb-Free Processes

摘要

Leadless, near chip scale packages (LNCSP) like the quad flat pack no lead (QFN) are the fastest growing package types in the electronics industry today. Early LNCSPs were fairly straightforward components with small overall dimensions, a single outer row of leads and small lead counts. However, there is currently a proliferation of advanced LNCSP package styles that have started to approach BGA packages in terms of both size and number of connections. Some of the newer packages have 3 or more rows, pitches as fine as .35mm, lead counts exceeding 200, and dimensions exceeding 12 mm × 12 mm. While the advantages of these packages are well documented, concerns arise with both reliability and manufacturability in Pb-free environments. So, acceptance of these packages in long-life, severe-environment, high-reliability applications is somewhat limited. One of the most common drivers for reliability failures is the inappropriate adoption of new technologies like LNCSP. Since robust manufacturing and qualifications standards always lag behind implementation, users must carefully select and validate these components for suitability in their use environments and customer applications. Soldering, flexure, and cleanliness issues have driven many failures seen in production and in the field. All of these areas must be addressed early in the selection and validation processes. In this paper, we will review and discuss LNCSP related reliability concerns and challenges, and propose Physics-of-Failure (PoF) based approaches to allow the successful introduction and failure analysis of LNCSP components in electronics products.