Four-laser bending beam measurements and FEM modeling of underfill induced wafer warpage

Warpage is one of the challenging problems for wafer level package (WLP). Especially, the bonding process of multiple wafers will bring additional stress to WLP and warpage of WLP. This paper aims at the stress and warpage characteristics of the WLP (consisting of silicon cover wafer and silicon MEMS wafer) with glass frit bonding. The finite element (FE) method and MOS (Multi-beam Optical Sensor) technology were used. Simulation result indicated that WLP presents almost zero warpage. MOS measurement result indicated that WLP actually presents convex warpage instead of zero warpage. It turned out that the convex warpage results from the temperature difference between WLP wafers (i.e. cover wafer and MEMS wafers) in the course of post-bond cooling. Taken the temperature difference into account, the simulation result was consistent with experiment results. Furthermore, on the basis of the convex warpage value the stress of WLP was also calculated so as to understand the stress distribution and estimate the reliability level of the MEMS device. Keywords-warpage,wafer level package(WLP), finite element method(FEM), micro Electro mechanical systems(MEMS), multibeam optical sensor (MOS)

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Warpage characteristics of wafer-level package of MEMS with glass frit bonding

Wang

Zhu

et al. 2013

2013 14th International Conference on Electronic Packaging Technology

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Warpage and stress optimization of wafer-level package of MEMS with glass frit bonding

Zhu

et al. 2014

2014 15th International Conference on Electronic Packaging Technology

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Warpage issue of wafer level package (WLP) has caught the attention of WLP industry. This paper aims at the warpage characteristics and optimization of the WLP (consisting of silicon MEMS wafer and silicon cover wafer) with glass frit bonding. Finite-element method (FEM) was used to study the warpage and stress optimization of the Si-Si bonding WLP. Some factors which affect WLP warpage, such as CTE (coefficient of thermal expansion) and Young's modulus of glass frit, ring thickness & width of glass frit and bonding temperature etc. were optimized. The stress of WLP was also calculated and the reliability level of the MEMS device was estimated. It turned out that CTE and Young modulus of glass frit are the key parameters for decreasing WLP warpage and stress and promoting the MEMS WLP. Ring width of glass frit and the thickness of silicon cover plate wafer have little impacts on WLP stress and warpage. With the optimized parameters taken into account, the stress in MEMS WLP falls down. Those optimization results have been put into actual WLP manufacture. Keywords-warpage; stress; optimization; glass frit; wafer level package (WLP); finite-element method (FEM); MOS (multi-beam optical sensor) deformation measurement; micro electro mechanical systems (MEMS)

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Study on Warpage and Peeling Mitigation of Wafer Level During Metal Plating Process

Li¹,

Xiao²,

Wang³

2021

2021 22nd International Conference on Electronic Packaging Technology (ICEPT)

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Four-laser bending beam measurements and FEM modeling of underfill induced wafer warpage

Cited by 5 publications

References 8 publications

Warpage characteristics of wafer-level package of MEMS with glass frit bonding

Warpage characteristics of wafer-level package of MEMS with glass frit bonding

Warpage and stress optimization of wafer-level package of MEMS with glass frit bonding

Study on Warpage and Peeling Mitigation of Wafer Level During Metal Plating Process

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