Thermal Performance of High Thermal Conductivity TIM for Large Advanced Package through TTV Measurement and FEM Analysis Approach

With the development of artificial intelligence (AI) and high-performance computing (HPC) technology, advanced packages such as CoWoS (Chip on Wafer on Substrate) have become more popular in recent years due to its outstanding signal transmission speed and space management efficiency. Nevertheless, such high-power applications and the large size of heterogeneous integrated package may lead to thermal and high package warpage problems. In that case, the high stiffness heat spreader is usually used to solve the problem of large warpage. However, structural damage caused by stress and additional thermal resistance from the interface between heat spreader and die top surface have occurred. In terms of stress and thermal issues, optimizing packaging material selection and high thermal conductivity thermal interface material (TIM) are widely used to reduce the stress risk and enhance thermal performance. Therefore, it is important to accurately predict mechanical stress performance and thermal behavior. In this study, the thermal conductivity that considers real application of TIM needs to be extracted to ensure the FO-EB-T (Fan-Out Embedded Bridge with TSV) package thermal performance. In order to achieve this purpose, junction-to-case thermal resistance (ӨJC) measurement of large lidded FCBGA thermal test vehicle (TTV) is firstly measured to ensure the silicon based/graphite/alloy based TIMs thermal performance with liquid-cooling test fixture. Scanning acoustic tomography (SAT) and destructive physical analysis (DPA) are measured to check the TIM coverage and bond line thickness (BLT). Then, thermal conductivity which considers the interface effect is calculated by heat transfer equation using ӨJC, TIM coverage and BLT results. After extracting the thermal conductivity from the TTV measurement, a thermal simulation is constructed to ensure thermal behavior of the large lidded FO-EB-T test vehicle with the liquid cooling system using FloTHERM. Finally, the mechanical performance of the FO-EB-T is simulated by ANSYS to check the warpage and stress behavior. The structural material optimization is proposed to ensure the package warpage performance while reducing the chip module epoxy molding compounds (EMC) stress risk. Overall, the paper proposes a method that can extract the thermal conductivity of TIMs in real application. And further ensure not only the thermal performance but also mechanical behavior of large lidded FO-EB-T by thermal and mechanical simulation. Above that, the FO-EB-T package development that can save the design of experiments (DOE) and the thermal behavior consider real application are being proposed.