Whisker is a single crystal growth noticed frequently in Sn plating and Sn alloy plating. It is also an abnormal phenomenon occurring frequently when performing pure Sn electroplating. It is known that whisker is caused by residual stress emitted by compressive stress generated during the process of plating. However, neither a precise mechanism nor an accelerated testing method exists. Moreover, no firm guideline is in place as to which plating solution(s) and what plating process(es) could prevent whisker. Because of this, applying pure Sn coating layer to Pb-free lead finish involves a number of risk factors.

• Compressive stress in the Sn layer
• Crystallographic defects in lattice structure

• Grain size, shape, orientation
• Crystallographic defects in lattice structure
• Process
• Substrate material
• External mechanical stress: bending, scratching, thermal cycling
• Substrate stress
• Irregular, thick and fast IMC formation

• Bath Chemistry
• Process
• Substrate diffusion and subsequent IMC formation

Whisker Evaluation at SAMSUNG (1.82MB )

visit http://nepp.nasa.gov/whisker/

visit http://www.calce.umd.edu/lead-free/tin-whiskers/

• 65 ~ 150 °C 1000cycs (Carsem)
• 35 ~ 125 °C 500cycs (Sony)
• 40 ~ 90 °C 500cycs (NEMI)
• Room Temp(4 weeks) (NEMI)
• Room Temp(1 year) (Sony)
• 65 °C 1000hrs (Sony)
• 50 ~ 55 °C 26months (Carsem)
• PCT 1000hrs. (Carsem)
• 50 °C /Ambient(4 weeks) (NEMI)
• 85 °C /Ambient(4 weeks) (NEMI)
• 85 °C /85% 1000hrs. (NEMI, Carsem)
• 85 °C /85% 500hrs. (Sony)
• 50 °C /85% 1000hrs. (Carsem)
• 50 °C /85%(4 weeks. (NEMI)