Reflectivity and Thermal Shock Properties of Sn-3.5Ag Electroless-plated Deposit for LED Lead Frames

摘要

The surface roughness and reflection characteristics of electroless-plated Sn-3.5 wt%Ag on a LED (light emitting diode) lead frame were investigated. Cu electroplating was carried out prior to electrons plating of Sn-3.5Ag to improve the reflectivity of the Sn-3 5Ag deposit. A thermal shock test was performed to evaluate the stability of the deposits, namely the surface roughness and the reflectivity of the Sn-3.5Ag layer. The experimental results revealed that the surface roughness of the Sn-3.5Ag deposit was 0.135um (arithmetical average roughness, R_8), 1.77 urn (maximum height roughness, R_(max)) and the reflectivity was 1.86 GAM. After 500 thermal shock cycles of the Sn-3.5Ag deposit between 85°C and -55°C, the surface roughness became 0.145 pm (R_a) and 1.93 urn (R_(max) and the reflectivity was 1.76 GAM, which indicates that the Sn-3.5Ag deposit was stabilized by 500 thermal cycles.