Current trend in the industry has seen multi-stacks ball grid array (BGA) being introduced to fulfill the increasing demands of the customer to includes both high performance and smaller size chip package. Conventional underfill encapsulation process on multi-stack BGA to to enhance the reliability of the package is still prone to undesired drawbacks of prolonged encapsulation time and incomplete filling. Accordingly, thermal energy is introduced by preheating the chip prior the underfill process is seen as a viable option to solve the slow filling time issue. A comparative experimental study is conducted on a scaled-up multi-stack BGA model for the cases at two distinct setups; at room temperature of 25°C and pre-heated at 70°C respectively. Decisive data has concluded that the setup with elevated temperature has prominently increase the filling rate by 75.2% with shorter completion filling time achieved. This justified the necessity of conducting the underfill process at an elevated temperature as a future operating procedure in the encapsulation process.