Solder joint reliability of TSOPs-an overview

One of the recent trends in electronic packaging is the increasing emphasis in miniaturization driven by the end user demand for more powerful, light weight, and portable computing power. A clear example of this is the development of Thin Small Outline Packages (TSOPs) that have a nominal package height of about 1.2 mm with a package to board clearance of about 0 to 0.05 mm, and lead pitches in the range of 0.5 to 1.25 mm. TSOPs are finding multitudes of applications in portable computers and their use is being extended to high end workstation applications. These packages occur in two different versions: type I and type II. A primary application of TSOP modules is in Personal Computer Memory Card International Association (PCMCIA) packages where the cards are used as portable interfaces between system computers and industrial, scientific, public service, robotics, and consumer, and software distribution systems. In this paper are discussed the assembly and reliability aspects of these packages in the context of second level assembly. Type I and II TSOPs and Plastic Quad Flat Packs have many similarities yet there exist several differences that significantly affect their long term performance and reliability. The factors that are considered here are the effect of lead stand-off, ratio of chip to package dimensions, and TCE mismatch