Tin Whisker Test Development-Temperature and Humidity Effects Part I: Experimental Design, Observations, and Data Collection

The effects of temperature and humidity on tin whisker growth were investigated through a collaborative project sponsored by the International Electronics Manufacturing Initiative (iNEMI) and its member companies. A broad range of testing conditions was adopted to test a variety of components with matte tin (Sn) plating and copper (Cu)-based leadframes. The primary goal of the study was to collect data that could be used to develop mathematical models (acceleration functions) that describe the dependence of tin whisker growth and corrosion on temperature and humidity. This paper describes the background, experimental design, data collection and reports results. Part II of the study (J. W. Osenbach et al. Tin whisker test development-Temperature and humidity effects part II: Acceleration model development, Electronics Packaging Manufacturing, Vol. 33, no. 1, pp., Jan. 2010) discusses in the data analyses and acceleration model development. Storage testing was performed over a wide range of temperature and humidity conditions from 30 degrees C to 100 degrees C and from 10% to 90% relative humidity (RH). Commercially produced components with both 3 mu m and 10 mu m thicknesses from three sources were evaluated. For components with the 10 mu m-plating, the plating was evaluated in both the as-plated and reflowed (260 degrees C) conditions. These variations resulted in a large experimental matrix that included 13 different Sn platings, aged at ten different temperature and humidity combinations. Further, the aging test was done at five different laboratories with inspections performed at eight different laboratories. The data collected include 1) corrosion incubation time, 2) tin whisker incubation time, and 3) dependence of the maximum whisker length on storage time at each temperature/humidity condition. Data suggest that corrosion is not a unique driving force for whisker initiation and growth. Whisker formation differs in corroded and non-corroded regions. Due to the scope of this work, it is broken down into two papers. The data and experimental observations are discussed in this paper. The mathematical model development, discussion of results and conclusions are included in Part II of this study.