Not Whiskers or Hillocks, But Tin Bumps on RF Shielding Cans

Pure tin bumps can sometimes be formed on tin-plated steel RF cans during certain conditions of reflow. This is a rare phenomena not associated with tin whiskers. A Design of Experiments (DOE) strategy was used to confirm the oven variables that could be used to turn the formation on or off. Extensive lab work and investigation by the supplier revealed that the root cause of these bumps is organic contamination during the plating process.