Characterization and Modeling of Fine-Pitch Copper Ball 4 Bonding on a Cu/Low-k Chip

Characterization and Modeling of Fine-Pitch Copper Ball 4 Bonding on a Cu/Low-k Chip

Journal of Electronic Materials

10.1007/s11664-014-3532-4

http://link.springer.com/article/10.1007%2Fs11664-014-3532-4

Xiaowu Zhang, T. C. Chai, Fa Xing Che, L. C. Wai

17 December 2014

Cu ball bonding faces more challenges than Au ball bonding, for example, excessive deformation of the bond pad and damage of Cu/low-k structures, because of the much greater hardness of Cu free air balls. In this study, dynamic finite-element analysis (FEA) modeling with displacement control was developed to simulate the ball-bonding process. The three-dimensional (3D) FEA simulation results were confirmed by use of stress-measurement data, obtained by use of stress sensors built into the test chip. Stress comparison between two-dimensional (2D) and 3D FEA models showed the 2D plain strain model to be a reasonable and effective model for simulation of the ball-bonding process without loss of accuracy; it also saves computing resources. The 2D FEA model developed was then used in studies of a Cu/low-k chip to find ways of reducing Al bond pad deformation and stresses of low-k structures. The variables studied included Al pad properties, capillary geometry, bond pad design (Al pad thickness, Al pad coated with Ni layer), and the effect of ultrasonic bonding power.

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https://oar.a-star.edu.sg/communities-collections/articles/12166

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