Abstract
Low thermal conductivity and large coefficient of thermal expansion (CTE) are the most serious disadvantages of the polymer dielectric for the interposer redistribution layer (RDL). In this paper, a high thermal conductivity and low CTE composite with polyimide (PI) matrix and diamond nanoparticles/SiC whiskers reinforcement is proposed. The preparation and characterization of the composite film are presented and the effects of the composite on the improvement of the interposer properties are investigated. With 10 wt% diamond-nanoparticles and 7 wt% SiC-whiskers, the composite film has a thermal conductivity of 1.63 W/m·K and a CTE of 16.7 ppm/°C (compared with 0.19 W/m·K and 55.6 ppm/°C of the PI). Interposers with PI RDL dielectric and the composite RDL dielectric are fabricated, respectively. The simulation result shows that the composite dielectric can significantly enhance the properties of the interposer compared with the PI dielectric. The thermal resistance of the interposer decreases from 8.04 °C/W to 1.15 °C/W. The maximum von Mises stress decreases from 72.8 MPa to 16.9 MPa and the warpage decreases from 1.13 μm to 0.15 μm. Thermal distribution tests are performed as well. The results show that the maximum temperature of the interposer decreases from 64 °C to 45.1 °C. The composite developed in this study can reduce the temperature and enhance the reliability of the chips with interposers. It has the potential to expand the application of the interposers in high thermal density integration and high reliability devices.
Highlights
Development of the 3D integrated circuit (IC) integration is driven by the demands for further miniaturization of device, higher integration density, lower power consumption and better performance [1,2,3,4]
Besides the enhancement of thermal conductivity and the reduction of coefficient of thermal expansion (CTE), it is essential for the composite to maintain its electrical and mechanical properties to be used as spin-coating dielectric, such as good insulation property, low relative permittivity, good fluidity for spin-coating and enough mechanical strength
Besides the enhancement of thermal conductivity and the reduction of CTE, it is essential for the composite to maintain its electrical and mechanical properties to be used as spin-coating dielectrics
Summary
Development of the 3D integrated circuit (IC) integration is driven by the demands for further miniaturization of device, higher integration density, lower power consumption and better performance [1,2,3,4]. Spin-coated polymer-based dielectrics with high thermal conductivity and low CTE has very good application prospects in the 3D IC integration. As presented by Xie, the addition of AlN particles improves the thermal conductivity of the composite, but it increases the relative permittivity significantly which may cause severe signal delay problems. Besides the enhancement of thermal conductivity and the reduction of CTE, it is essential for the composite to maintain its electrical and mechanical properties to be used as spin-coating dielectric, such as good insulation property, low relative permittivity, good fluidity for spin-coating and enough mechanical strength. The preparation and characterization of a composite with high thermal conductivity and low CTE is presented and its application in interposer RDL dielectrics is discussed as well. The DNs and SCWs are dispersed into the matrix to form particle-whisker network structures for improving the thermal conductivity, reducing the CTE and reinforcing the mechanical strength of the matrix
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