Package Integrated Vapor Chamber Heat Spreaders

In Flip Chip Ball Grid Array (FCBGA) packages that require the protection and mechanical benefits of an integrated heat spreader, a package integrated vapor chamber heat spreader can offer significant thermal enhancement compared to a pure copper heat spreader. This study investigates the unique characteristics and challenges of integrating a vapor chamber heat spreader onto a FCBGA package and proposes a methodology to quantify the effective thermal conductivity of the vapor chamber under different conditions using finite element analysis. Test results indicate that the effective thermal conductivity of the vapor chamber varies depending on the system cooling solution's thermal resistance, and for most cases, offers significant thermal enhancement over a pure copper heat spreader. An FCBGA thermal test vehicle was constructed to evaluate the vapor chamber heat spreaders. With a high resistance cooling solution comprised of an aluminum heat sink and pad type TIM II, the package integrated vapor chamber heat spreader offered a 12.5°C reduction in junction temperature at 120 W power compared to a standard copper heat spreader. With a low resistance cooling solution, a copper heat sink and grease type TIM II, the package integrated vapor chamber heat spreader offered a 4.2°C reduction in junction temperature compared to a standard copper heat spreader. Using a finite element analysis (FEA) method to extract the effective thermal conductivity of the vapor chamber heat spreaders, it was found that under the aluminum heat sink and pad type TIM II test condition, the vapor chamber achieved an effective thermal conductivity of 11,750 W/m*K. Under the copper heat sink and grease type TIM II test, the vapor chamber heat spreader was found to achieve an effective thermal conductivity of 3,495 W/m*K.