Thermal Dissipation And Thermal Mechanical Reliability Study For MCM-L

In order to meet the high speed, high density and high performance requirement of the package of CPU of domestic next generation supercomputer, the thermal dissipation and thermal-mechanical reliability of a kind of build-up laminated Multi-Chip Module (MCM-L) which will be applied in a certain supercomputer was investigated comprehensively in this paper. The module consisted of seven chips with 1268 eutectic solder bumps under each chip, which are mounted on a 224ayer laminated polyimide substrate with build-up layers and stacked vias. Underfill was filled in between the chips and substrate. The total power of the module was 90W and the maximum heat flux was 30W/cm~2.In the aspect of thermal dissipation, an aluminum cold plate with inner double flow path was designed as the indirect liquid cooling equipment for the module. In order to determine the cooling ability of the cold plate, a series of similar experiments were conducted firstly: two power devices which could imitate power dissipation of chips were mounted on the top of the cold plate with thermal interface materials, and CFD simulations corresponding to the experiments were performed to get the fluid flow, temperature distribution and heat balance of the cold plate and power devices. The comparisons of the experimental results and simulation results not only evaluated the validity of CFD simulation method but also determined the interfacial thermal resistance of thermal interface materials iteratively. And then CFD simulation was used to investigate the heat transfer and fluid flow of the multi-chip module, the results turned out that the maximum temperature of the module was about 58.1℃, which indicted the cold plate could meet the requirement of thermal design. Based on the CFD simulation, the effects of factors such as thermal conductivity and interfacial thermal resistance of the thermal interface materials, solder bump patterns, solder ball patterns, thickness of the chips, space between chips, flow velocity and liquid inlet temperature on the thermal performance of the module were studied.