A. Choubey, D. Menschow, S. Ganesan, and M. Pecht
University of Maryland
College Park, MD 20742
Most electronics companies are transferring or have transferred to Pb-free electronics, both to comply with government legislations and to increase market share through product differentiation. Considering that Pb-based electronics have been in use for over 40 years, the adoption of Pb-free technology represents a dramatic change. Pb-free electronics are expected to be deployed in many products, including oil well applications, which require high reliability in high-temperature environments.
This study involves the design, manufacture, test, and analysis of printed circuit board (PCB) assemblies to obtain critical information related to the long-term exposure of Pb-free assemblies to high temperatures. Several components, including plastic ball grid arrays (PBGA) (Sn3Ag0.5Cu balls), quad flat packs (QFP) (Sn, Sn-Cu, Sn-Bi lead finish), and surface-mount resistors with Sn termination, were mounted on polyimide PCBs fabricated with various pad finishes (immersion-Sn (ImSn), immersion-Ag (ImAg), electroless nickel over immersion-gold (ENIG), and a patented fused Sn over Ni finish (SnNi)). The results from this study include both the extent of intermetallic growth in the solder joints, as a function of commercially available PCB pad finishes and component finishes, and the solder joint strength data for QFPs as a function of aging conditions and finishes.
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