Selective Plating for Surface-Mounted Component Lead
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
A method is described which can eliminate the solder wicking problem, which is one of the biggest concerns in surface-mounted technology (SMT). One of the most frequently occurring solder defects in the SMT area is solder joints which open mainly because of the solder wicking to the component leads during solder paste reflow (see the figure). Some of the possible causes of solder wicking problems are as follows: -contamination and/or oxidation of pad surface, -solderability difference between component lead and pad (e.g., Sn or Sn/Pb vs. Cu), -differences of heat transfer due to different heat sink during reflow (pad vs. component lead or small sized component vs. big component), -coplanarity of component leads or misregistration of component, and -variability of component leads surface finishing.