This study investigates the effects of aging in air and argon at 170°C on Cu coupons which were pretinned with 75Sn-25Pb, 8Sn-92Pb, and 5Sn-95Pb solders. Coatings were applied using electroplating or hot dipping techniques.The coating thickness was controlled between 3 to 30ktm and the specimens were aged for 0 hours, 2 hours, 24 hours and 2 weeks. Wetting balance tests were used to evaluate the wettability of the test specimens. Microstructural development was evaluated using X-ray diffraction, energy d_spersive X-ray and Auger spectroscopy, as well as optical and scanning electron microscopy.The wetting behavior of the test specimens is interpreted with respect to observed microstructural changes and as a function of aging time, solder composition, and processing conditions. i Graph showing the net (excluding plateau) time to 90% of the maximum wetting force as a function of coating thickness and aging time for the Sn-rich (75Sn-25Pb), electroplated samples aged in air. showing cross-section of a Pb-rich (5Sn-95Pb), hot-dipped (360°C) specimen which was aged in argon at 170°C for 2 weeks. LIST of TABLESix