Thermal Performance Research Of 3D High Power Chips On The Basis Of TSV

By stacking multiple chips in Z direction and achieving high-density packaging, 3D packaging can meet the requirements of electronic products, such as low cost, low power, small size, etc. However, thermal management is very serious in 2.5D and 3D packaging, and it is of great importance to study the thermal performance of high-power chips.With micro-channels integrated within the interposer, heat generated by 3D high power chips when working is taken away by the circulating fluid medium, and the working temperature of chip is maintained within an appropriate range, which is a desirable cooling solution for high power chips. The chip of power 100 W and heat flux 100W/cm2, integrated with TSV and micro-channels, is proposed in this paper. The micro-channels liquid cooling technology is applied to cool down the chip. The overall model is established to carry out the related research work. The content of this paper is mainly summarized as follows.First, there are numbers of solder joints, TSV and other minor structures in the packaging, so the model needs to be simplified. The equivalent method and the equivalent thermal conductivity formula of solder joints are proposed. The actual model integrated with 400 solder joints and the equivalent model is built. As for with and without underfill in the actual model, the software ANSYS Workbench is applied to compute the error by simulation when the diameter and pitch of solder joints are varied. The main conclusions are shown: For the equivalent method of solder joints in this paper, the temperature error is less than±1% in Z direction and is below 30% in X-Y direction, correspondingly. While for the equivalent method that take the material of all the solder joints and underfill as solder, the temperature error is between ±65.0%~±99.0% in Z direction and is between±97.85%~±99.94% in X-Y direction, correspondingly.Secondly, the equivalent method and the equivalent thermal conductivity formula of interposer are proposed, and the equivalent thermal conductivity of interposer is analyzed as the diameter, pitch and aspect ratio of TSV change. The actual model integrated with 100 TSVs and the equivalent model is built, and the steady state thermal analysis is carried out by the software ANSYS Workbench. The error of the equivalent method is obtained by simulation, and the conclusions are reached: The equivalent thermal conductivity of interposer increases as the diameter of TSV increases, decreases as the pitch of TSV increases and decreases as the aspect ratio of TSV increases. For the equivalent method of interposer in this paper, the temperature error is less than ±10% in Z and X-Y directions.Thirdly, the whole model is simplified and the simulation model is determined on the basis of the equivalent thermal conductivity formula of solder joints and interposer. The simulation model with five different widths of micro-channels: 0.2mm, 0.4mm, 0.6mm, 0.8mm and 1.0mm is built. The software ANSYS CFX is adopted to analyze the model at different coolant inlet fluid velocity: 0.1m/s, 0.5m/s, 1m/s and 2m/s. The fluid pressure in the flow fluid and the temperature of the chip are compared. The conclusions are as follows: Without heat sink, the temperature of the chip is 1219.6K, while for the micro-channel with the width of 0.6mm; the chip on the model is 334.1K at the inlet velocity of 1m/s correspondingly. With the same fluid velocity, when the width of micro-channel decreases, the heat transfer performance and the fluid pressure are both increase. When the width of micro-channel remains unchanged, the heat transfer performance and the fluid pressure increase as the flow rate increases.Finally, for the model with the micro-channel of width 0.6mm, the simulation result shows that it cannot meet the miniaturization requirement of micro-pump when the inlet fluid velocity is 1m/s. By changing the duty cycle of the fins from 1 to 0.5, the structure of micro-channel is optimized, and the conclusions is drawn by simulation: When the inlet fluid velocity is 0.5m/s, the maximum chip temperature is 63.5? and the pressure is 0.50441 bar, and this condition can both meet the thermal design requirement of the system and the miniaturization requirement of the micro-pump simultaneously. Then, the preliminary design of the whole system is conducted and the flow rate and pressure drop of the system are theoretically calculated, which are 258.75 m L/min and 0.53142 bar, respectively. The type of micro-pump is chosen accordingly. Finally, all the parts of the system are assembled together, and the bulk of which is 60 mm ?60mm ?85mm approximately.