Cleaning of Eutectic No-Clean Solder

Circuit board longevity is a key factor in electrical and electronic equipment. Boards are constantly introduced to varying environmental conditions, including extreme heat, high relative humidity and below freezing temperatures. The specific production processes used along with the differing levels of voltages applied introduce even more variables that may impact longevity. It is necessary to understand why some boards fail. The team designed an experiment which tests key factors to provide data and understand failures of printed circuit boards.

The experiment is based on varying three factors: voltage, flux volume and pad spacing. The team developed a circuit board which optimized the number of tests per board while meeting design of experiment requirements. They used a humidity/temperature chamber to match desired environmental conditions, applied flux to each board at three differing levels, and applied voltage sources ranging from 15V to 50V DC. Pad spacing allowed for further variation. The boards were held under constant environmental conditions for a period sufficient to encourage dendritic growth. The team noted current leakage, recorded the time of failure and presented relevant statistics. Ion chromatography permitted further understanding of the factors causing dendritic growth and current leakage.