Y. H. Lin, F. Kuo, Y. F. Chen, C. Ho, J. Y. Lai, S. Chen, F. Chien, R. Lee, J. Lau
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To meet high I/O density IC request, the trend of wafer level chip scale package (WLCSP) I/O pad distributed design is toward to reduce the I/O pitch and increase the I/O density, and therefore impact solder ball size application of ball mount process, WLCSP micro-ball mount technology is requested. In this study, a low-cost and fine-pitch micro-ball mounting technology is developed. Emphasis is placed on determining the most important factors such as accurate dropping parameters, stencil quality and reflow conditions for microball mounting design, materials, and process. Three different ball sizes are considered: 70μm, 100μm, and 250μm. Their corresponding pitches are 130μm, 180μm, and 400μm. WLCSP micro balls with diameter = 70μm and pitch = 130μm on 300mm wafers (with ~2KK I/Os) have been successful produced. 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引用次数: 4
摘要
球贴装技术使用焊料球体通过金属模板一次性滴到晶圆上。该技术直接在晶圆上产生凸点,具有高通量和一致的凸点结果。不使用电镀的滚珠安装工艺降低了成本和化学污染。该技术适用于许多应用,但与该技术相关的几个问题限制了其在大批量和高产量应用中的广泛应用。这些限制包括:(1)可以掉落的球体尺寸的实际下限,(2)所执行的焊接球体和晶圆之间的模板可能失效,导致所有球体释放到工具中(通常称为爆裂或逃逸),并且产量在统计上很低。为了满足高I/O密度集成电路的要求,晶圆级芯片规模封装(WLCSP) I/O焊盘分布式设计的趋势是减小I/O间距和增加I/O密度,因此影响滚珠安装工艺中焊球尺寸的应用,要求采用WLCSP微滚珠安装技术。本研究开发了一种低成本、小间距的微球安装技术。重点放在确定最重要的因素,如准确的下降参数,模板质量和回流条件的微球安装设计,材料和工艺。滚珠尺寸分为70μm、100μm和250μm。分别为130μm、180μm和400μm。在300mm晶圆(I/ o ~2KK)上成功制备了直径为70μm、节距为130μm的WLCSP微球。产率大于99.99%,无微球丢失和桥接现象。
Low-cost and fine-pitch micro-ball mounting technology for WLCSP
Ball mount technology uses performed solder spheres dropping through a metal template onto wafer at once. This technology is directly producing bumps on wafer with high throughput and consistent bump results. Ball mounting process without using electroplating decreases cost and chemical pollution. This technique is applicable for many applications but several issues associated with this technology that limits its widespread use in high volume and high yield applications. These limitations include: (1) a practical lower limit to the size of sphere that can be dropped, and (2) the stencil between the performed solder spheres and the wafer can fail, causing a release of all the spheres into the tool (often referred to as bursts or escapes), and the yields are statistically low. To meet high I/O density IC request, the trend of wafer level chip scale package (WLCSP) I/O pad distributed design is toward to reduce the I/O pitch and increase the I/O density, and therefore impact solder ball size application of ball mount process, WLCSP micro-ball mount technology is requested. In this study, a low-cost and fine-pitch micro-ball mounting technology is developed. Emphasis is placed on determining the most important factors such as accurate dropping parameters, stencil quality and reflow conditions for microball mounting design, materials, and process. Three different ball sizes are considered: 70μm, 100μm, and 250μm. Their corresponding pitches are 130μm, 180μm, and 400μm. WLCSP micro balls with diameter = 70μm and pitch = 130μm on 300mm wafers (with ~2KK I/Os) have been successful produced. The yield is more than 99.99% without any missing micro ball and bridging.