亚硫酸盐无氰体系电镀金凸块性能的影响因素

Factors affecting the properties of gold microbumps electroplated in a cyanide-free sulfite-based bath

[目的]鉴于先进封装技术向微型化和集成化发展,电镀金凸块成为液晶显示驱动芯片互连的首选。但纯金材料存在强度不足、易形变的问题,因此提升电镀金凸块的力学性能是该领域的研究重点之一。[方法]采用亚硫酸盐无氰体系在晶圆表面电镀金凸块,研究了镀液各组分浓度、工艺参数变化及镀液老化对金凸块性能的影响。[结果]晶圆表面各部位的金凸块外观均一,无漏镀、结瘤、针孔等缺陷,退火后的显微硬度约为90 HV,其力学性能可在较为宽泛的施镀工艺窗口、镀液组分浓度范围及镀液老化过程中保持稳定。[结论]该亚硫酸盐无氰电镀金工艺有望在高密度封装领域得到推广应用。

[Introduction]Given the development of advanced packaging technology towards miniaturization and integration,electroplated gold bumps have become the preferred choice for interconnecting liquid crystal display(LCD)driver chips.However,pure gold has disadvantages such as insufficient strength and easy deformation,so improving the mechanical properties of electroplated gold bumps is one of the research focuses in this field.[Method]A cyanide-free sulfite-based bath was used to electroplate gold microbumps on wafer surface.The effects of the concentrations of various components in the bath,process parameters,and bath aging on the properties of gold microbump were studied.[Result]The gold microbumps at different parts of a wafer were uniform in appearance,with no defects such as skip plating,nodules,or pinholes,and their microhardness after annealing were about 90 HV.The mechanical properties of the electroplated gold microbumps remained stable within a wide range of electroplating process window,bath component concentrations,and bath aging process.[Conclusion]The cyanide-free sulfite-based gold electroplating process is expected to be promoted and applied in the field of high-density packaging.