【作者】 卿湘勇；

【导师】 黄明亮； 马海涛；

【作者基本信息】 大连理工大学 ， 材料物理与化学， 2010， 硕士

【摘要】 发光二级管LED (Light Emitting Diode)作为一种新型的绿色照明光源,与传统的照明灯相比,在功耗、亮度与寿命方面具有无与伦比的优势,必将成为21世纪的发展趋势。倒装芯片技术(Flip-Chip Technology)的使用极大的提高了LEDs的散热能力和出光效率,成为现阶段研究的热点,但同时也对芯片凸点的制作提出了更高的要求。本论文选择Au-30at.%Sn共晶合金作为芯片的凸点材料,致力于开发一种稳定的无氰Au-Sn镀液来替代传统的氰化物镀液,并通过系列实验确定适用的镀液成分及电镀工艺参数,以实现共沉积法制备Au-30at.%Sn共晶凸点。研究结果表明：1.开发出一种pH值在6-9内稳定的无氰Au-Sn镀液,该镀液以亚硫酸金钠、硫酸亚锡为主盐,亚硫酸钠、EDTA作为金络合剂,并向镀液中添加了一种锡络合剂。2.施镀温度对镀层平整性影响较明显：当施镀温度在25～65℃之间变化时,温度过低镀层表面起伏较明显；温度过高,又会降低镀液的稳定性。所以,采用本论文所开发的无氰Au-Sn镀液施镀温度在45～55℃间较合适。3.峰值电流密度影响镀层锡含量。采用本论文所开发的无氰Au-Sn镀液在低峰值电流密度下得到的镀层锡含量接近50at.%,而在高峰值电流密度下得到的镀层锡含量接近16at.%4.在T=45℃、J=27.5 mA/cm2时,镀液中其他成分及其浓度保持不变的条件下,[Au(Ⅰ)]／[Na2SO3]摩尔浓度比在1：8～1：20之间时,镀速变化不大,继续改变比率至1：24,镀速有明显的增加。高Au(Ⅰ)浓度未必会带来更高的镀层金含量和更快的镀层生长速度,但却可能降低镀液的稳定性并增大了金的带出的浪费；Na2SO3含量过低,镀液稳定性不好,但过高的Na2SO3含量又会增大镀液的粘滞性。综合考虑,较适宜的Au(Ⅰ)浓度为0.02 mol／L、Na2SO3浓度为0.48 mol／L,对应于[Au(Ⅰ)]／[Na2SO3]=1：24。更多还原

【Abstract】 As a new type of green lighting source, LED (Light Emitting Diodes) would surely lead the 21st century trends since their unmatched advantages at power consumption, luminance and lifetime compared with traditional lighting sources. The flip-chip technology improved the thermal dissipation and luminescence efficiency of High-power LEDs. However, higher requirements were submitted to the packaging technology.Au-30at.%Sn eutectic solder was chosen for the bumps, and a stable non-cyanide electroplating solution for Au-Sn alloys must be developed to replace the traditional solutions containing cyanide. Besides, the solution component and the electroplating process parameters were decided for co-electrodepositing Au-30at.%Sn eutectic bumps. The results indicated that:1. A stable non-cyanide electroplating solution with pH of 6 to 9 for Au-Sn alloys was developed. The solution contained Na3Au(SO3)2 (gold sodium sulfite) as the source of gold and SnSO4 (stannous sulfate) as the source of tin. Na2SO3 and EDTA were added as the complexing agent for gold, and an additional complexing agent for tin.2. The plating temperature had an obvious effect on the surface planarization of the Au-Sn films. When the temperature was in the range from 25℃to 65℃, the lower the temperature the rougher the films; however, higher temperature would degrade the stability of the solution. The suitable plating temperature for the newly developed solution was 45-55℃.3. Peak current density affected the tin content of Au-Sn films electroplated from the newly developed solution:Au-Sn films containing 50at.%Sn could be electroplated at low peak current density, while Au-Sn films containing 16at.%Sn electroplated at high peak current density.4. When [Au (I)]/[Na2SO3] molar ratio varied from 1:8 to 1:20 respectively, the plating rate of the Au-Sn films electroplated under T=45℃, J=27.5 mA/cm2 had no significant change. However, when the ratio varied to 1:24, the plating rate had a sharply increase. High Au (I) concentration in the solution could not result in a higher gold content in the Au-Sn films and higher plating rate, but might degrade the stability of the solution and increase the gold waste. The decreasing of Na2SO3 concentration would degrade the solution stability, while the increasing Na2SO3 concentration would result in a higher viscosity. The suitable concentration for Au (I) and Na2SO3 in solution was 0.02 mol/L and 0.48 mol/L, i.e., the corresponding molar ratio of [Au (I)]/[Na2SO3] was 1:24.更多还原