Dissolution of copper foil contact with liquid Sn-0.3Ag-0.7Cu solder

• Main Authors: Hsin-fang Chien, 簡信方
• Other Authors: Tien-his Lee
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/23557075728371261074

碩士 === 國立中央大學 === 機械工程學系在職專班 === 102 === Since 2010 the European RoHS 2.0 regulations come into effective and restricted to selling electronic products with limited lead content. The vast printed circuit boards and electronic assembly manufacturers, In order to meet product specifications of RoHS lead-free regulations, they have to upgrade own equipment and process capabilities to comply the requirements of the laws &; the market. In the exposed lead-free process relevant issues, the selection of lead-free solder has a very significant influence, which is not only related to the equipments of thermal assembly process and the choice of component materials. It is related to the product's reliability and life cycle also. As the Sn-3.0wt%Ag-0.5wt% Cu solder alloy with excellent wetting and mechanical properties, Which as the best choice for lead-free process of recommendation by major research institutions and associations, and widely used in the industry in printed circuit board assembly process, that become the mainstream lead- free solder alloy of the industry. Furthermore, due to the lead content as the strictly limited element of RoHS compliance, the traditional tin-lead HASL board has been restricted too. PCB industry needs to find another solutions to instead tin-lead HASL board . The organic surface protective (OSP) board has become the mainstream product due to low production equipment investment and manufacturing costs, good process yield rate and higher reliability of solder joints. But it is unlike gold plate (ENIG) or lead-free HASL (LF HASL) board, which with nickel protect copper surface to prevent Cu dissolute into solder and less copper dissolution affect in PCBA process. In the search of copper dissolution studies, we found the most studies are for experimental purposes, or just focus on Surface Mount Technology (SMT) relevant issues, under limited solder alloy conditions. The dissolution rate will decrease as the copper solute into solder and increasing the concentration of copper, even to stop the dissolution reaction of the equilibrium point. Due to the PCB copper is contacting to mass liquid solder directly, and caused the copper pad dissolution of through-hole components area during the wave solder process, That is the major concern of the current PCBA industry. In order to provide and stabilize the power to drive those attached devices, the amount of through hole components are necessary for high end Enterprise products. During the soldering process of through hole components, the huge melting solder alloy will contact with copper foil directly, and dissolve it into the solder. This study will based on selected solder alloy Sn-0.3Ag-0.5Cu, and using copper foils as the test vehicle, varying the solder’s temperature、immersion time and solder flow rate, to simulate actual production condition and calculate the copper dissolution, to carry out the relationship of copper dissolution v.s process parameter and further discussion.