| Popis: |
Replacement of Pb/Sn terminations on electronic devices with pure Sn has proven to be much more difficult than expected. The main problem is Sn whisker formation. Sn whiskers are typically single-crystal, mechanically strong, metallic filaments that can nucleate and grow over time in such a way as to lead to device failure in the field. In this study, we present the results of Sn whisker formation and growth studies for plated matte-Sn on Cu Pb frames. We include data on the effects of Sn-thickness, post-plate annealing, and simulated board attach reflow. Also included are data on two different bath base chemistries, methane sulfonic acid (MSA) and mixed acid, three different plating bath suppliers, and three different lead-frame plating suppliers. The effects of trim and form as well as lead-frame alloy type were also investigated. Whisker testing was completed by storing devices for at least 1 year at room ambient, 60/spl deg/C/93%RH, and 60/spl deg/C/ |
