Thermal-Mechanical Stress Modeling of Copper Chip-to-Substrate Pillar Connections
Thermal-Mechanical Stress Modeling of Copper Chip-to-Substrate Pillar Connections
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DOI：
10.1109/tcapt.2010.2050888
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发表时间：
2010-09
影响因子：
--
通讯作者：
P. An;P. Kohl
中科院分区：
文献类型：
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作者：
P. An;P. Kohl
硅集成电路与有机基板之间的热膨胀失配系数引起的热应力是芯片到基板连接的一个重要的可靠性问题。铜柱芯片到基板的连接，包括焊锡柱和全铜柱，是倒装芯片应用中具有底部填充的焊球的潜在替代品。与铜柱连接相关的热应力是铜柱及其相关芯片和基板端子的形状、尺寸和材料的函数。本文采用有限元分析方法对铜柱、芯片与基板连接的设计进行了研究。采用三维半广义平面变形切片模型研究了高温下的静态热应力。设计参数包括铜柱端部衬垫的形状和材料以及柱子周围的支承套圈的性质。模拟结果表明，芯片焊盘有助于降低芯片内部的最大热应力。此外，铜柱周围的支撑环用于降低硅芯片上的最大热应力。铜柱周围的高模数聚合物环用于降低柱子-芯片-焊盘连接处的应力，并增加柱子中心的应力。通过将套圈的弹性模数从1.2 Gpa提高到11.8 Gpa，模具内的最大热应力从160 Mpa降低到100 Mpa。
The thermal stress induced by the coefficient of thermal expansion mismatch between a silicon integrated circuit and an organic substrate is an important reliability issue for chip-to-substrate connections. Copper pillar chip-to-substrate connections, including solder-capped and all-copper pillars, are potential replacements for solder balls with underfill in flip-chip applications. The thermal stresses associated with copper pillar connections are a function of the shape, dimensions, and materials for copper pillars and their associated chip and substrate terminations. In this paper, the design of the copper pillar, chip-to-substrate connections has been studied using finite element analysis. A 3-D, half generalized plane deformation slice model is used to study the static thermal stress at elevated temperature. The design parameters include the shape and material of the pads at the terminus of the copper pillars and the nature of supporting collar around the pillar. The modeling results show that a chip-pad helps to lower the maximum thermal stress within the silicon die. Moreover, a supporting collar around the copper pillars serves to decrease the maximum thermal stress on the silicon die. A high-modulus polymer collar around the copper pillar serves to lower the stress at the pillar-to-chip-pad junction and increase the stress within the center of the pillar. The maximum thermal stress within the die was lowered from 160 MPa to 100 MPa by increasing the elastic modulus of the collar from 1.2 GPa to 11.8 GPa.