Effect of Au/Na2SO3 Molar Ratio on Co-electroplating Au-Sn Alloys in Sulfite-based Solution
LEDs (Light Emitting Diodes) that assembled using flipchip technology are today used as long-life, energy efficient, environmentally friendly light sources. However, the flip chip solder joints have to meet high requirements. Therefore, their performance and quality are crucial for the integrity of the assembly, which in turn is vital to the overall function of the LED. Au-30at.％Sn eutectic alloy is the generally used solder in electro-optical assemblies due to its excellent thermal and mechanical properties. Au-Sn solder bumps can be obtained by sequential electroplating of Au and Sn layers or by coelectroplating Au-Sn alloys from a single solution. In the present work, Au-Sn alloys have been co-electroplated from a non-cyanide, sulfite-based stable solution which contains Na3Au (SO3)2 (gold sodium sulfite) as the source of gold and SnSO4 (stannous sulfate) as the source of Sn. Na2SO3 (sodium sulfite) is added as the complexing agent for gold and an additional commercial complexing agent for Sn. The effect of the Au/Na2SO3 molar ratio in the plating solution on the composition of the deposits, surface morphology and plating rate has been investigated. It was shown that the Au/Na2SO3 molar ratio of 1/24 proved to be the best one with respect to plating rate and surface morphology in the present experiment. When the Sn2+ concentration is 0.03 mol/L, the optimum concentration for co-electroplating Au-Sn alloys is Au(I) concentration of 0.02 mol/L and Na2SO3 concentration of 0.48 mol/L, corresponding to the Au/Na2SO3 molar ratio of 1/24.
Xiangyong Qing Mingliang Huang Jianlin Pan
Electronic Packaging Materials Laboratory, School of Materials Science & Engineering, Dalian Univers Electronic Packaging Materials Laboratory, School of Materials Science & Engineering, Dalian Univers
国际会议
北京
英文
878-881
2009-08-10（万方平台首次上网日期，不代表论文的发表时间）