Controlling Whisker Formation in Tin-Based Solders Using Electrically Mediated

The global trend to eliminate lead from electronic devices is driven by legislative and marketing pressures based on environmental, health and social concerns on the cumulative effects of lead in waste streams. Tin and tin-rich alloys are the forerunning replacements for tin- lead solders. However, pure tin electrodeposits have a tendency to form tin whiskers that may cause short-circuiting, metal vapor arcing and failure of the component. The major cause of whisker growth is thought to be compressive stress in pure tin deposits after DC plating. Faraday Technology, Inc. has developed an electrically mediated electrochemical process for depositing lead-free solders, based on non-steady state electric fields to control the deposition process and consequently the physical properties of the deposit. Results of electrically mediated tin deposits are presented and compared to DC deposits in terms of grain size, internal stress type/magnitude and surface roughness