Thermal Cycle Reliability of Copper Pillar Bumps in Advanced Fan-Out Packages.
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| Title: | Thermal Cycle Reliability of Copper Pillar Bumps in Advanced Fan-Out Packages. |
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| Authors: | Shih, Meng-Kai1 (AUTHOR) mkshih@mail.nsysu.edu.tw, Chen, Shi-Jie2 (AUTHOR), Lin, I. Hung3 (AUTHOR), Lou, Bai-Yao3 (AUTHOR), Ni, Tom3 (AUTHOR) |
| Source: | Journal of Electronic Materials. Dec2024, Vol. 53 Issue 12, p8066-8077. 12p. |
| Subjects: | Surface mount technology, Response surfaces (Statistics), Epoxy compounds, Copper, Thermomechanical properties of metals, Thermocycling |
| Abstract: | Fan-out (FO) packages are in high demand for smartphones and Internet of Things (IoT) devices because they allow for the integration of multiple components within a single package, leading to enhanced functionality and improved operational performance. In addition, the shift from solder bumps to copper pillar bumps for interconnection is expected to become a prevalent trend in FO package assemblies because of their superior electrical and thermal performance and ability to achieve a finer pitch. However, the increased stiffness of the copper pillars increases the risk of interface fractures between the pillars and solder bumps during the surface mount technology process, which may degrade the thermal cycle test (TCT) reliability. Consequently, the present study develops a three-dimensional (3D) computational model, which approximates the thermomechanical properties of the redistribution layer (RDL) using the rule of mixtures principle, to analyze the reliability of the Cu pillar bumps in FO packages under thermal cycling between −55°C and 125°C. The tensile stress–strain properties of the polyimide (PI) film in the FO package are determined experimentally using an MTS Acumen microforce tester. The experimental data are used to construct an empirical formula for predicting the stress–strain response of the PI film, which is then incorporated into the simulation model. The validity of the simulation model is confirmed by comparing the predicted results for the out-of-plane deformation of the FO package with experimental observations. The reliability of the Cu pillar bumps under TCT processing is investigated numerically using the Anand viscoplastic constitutive model. Finally, a second-order response surface methodology model and Box–Wilson central composite design method are employed to determine the optimal design of the FO package that minimizes the plastic work density of the Cu pillar bumps. The results show that the thermomechanical reliability of the FO package depends mainly on the Cu trace coverage in the RDL and the thickness of the epoxy molding compound layer. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | Fan-out (FO) packages are in high demand for smartphones and Internet of Things (IoT) devices because they allow for the integration of multiple components within a single package, leading to enhanced functionality and improved operational performance. In addition, the shift from solder bumps to copper pillar bumps for interconnection is expected to become a prevalent trend in FO package assemblies because of their superior electrical and thermal performance and ability to achieve a finer pitch. However, the increased stiffness of the copper pillars increases the risk of interface fractures between the pillars and solder bumps during the surface mount technology process, which may degrade the thermal cycle test (TCT) reliability. Consequently, the present study develops a three-dimensional (3D) computational model, which approximates the thermomechanical properties of the redistribution layer (RDL) using the rule of mixtures principle, to analyze the reliability of the Cu pillar bumps in FO packages under thermal cycling between −55°C and 125°C. The tensile stress–strain properties of the polyimide (PI) film in the FO package are determined experimentally using an MTS Acumen microforce tester. The experimental data are used to construct an empirical formula for predicting the stress–strain response of the PI film, which is then incorporated into the simulation model. The validity of the simulation model is confirmed by comparing the predicted results for the out-of-plane deformation of the FO package with experimental observations. The reliability of the Cu pillar bumps under TCT processing is investigated numerically using the Anand viscoplastic constitutive model. Finally, a second-order response surface methodology model and Box–Wilson central composite design method are employed to determine the optimal design of the FO package that minimizes the plastic work density of the Cu pillar bumps. The results show that the thermomechanical reliability of the FO package depends mainly on the Cu trace coverage in the RDL and the thickness of the epoxy molding compound layer. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 03615235 |
| DOI: | 10.1007/s11664-024-11420-2 |
