Thermal Performance Research On Electronics Packaging Component Based On Flip Bonding

The two trends in the electronics packaging component field nowadays are the miniaturization in the size and high intensity in power. Development of high heat flux chips requires better heat dissipation performance and higher thermal reliability of the electronics packaging, meanwhile, the miniaturization tendency and portability demand of the electronics packaging accelerate the research on the air-cooling technology. So the crucial issue which the thermodynamic engineering is facing is how to ensure the thermal performance while the components burden heavier thermal load.The main purposes of the research are to accelerate the interior heat diffusion, reduce the mean operating temperature, relieve the inner thermal mismatch and thermal stress, and then improve thermal reliability and lengthen service life of the packaging component. In the thesis, experimental investigation on heat-transfer characteristics of air impingement jet and thermo-mechanical performance of solders was accomplished. After that, the numerical model about non-linear thermal-stress coupling was built, the interior distribution of temperature and stress of FC-CBGA electronic packaging component under the operating condition was simulated via ANSYS software, and then thermal capability of the component was evaluated and predicted. The details were expatiated as follows.Firstly, based on the concept of experimental investigation combined with accessorial numerical calculation, the corresponding numerical models were built according to the experimental systems. Then the experimental error and its causation were analyzed qualitatively and quantitively by simulating the dynamic testing process. Meanwhile the numerical simulation was applied to analyze the experimental results accessorially. Investigation indicated that it was feasible and beneficial for the experimental-simulation combination method to detect the limitation of experimental method and system, evaluate the testing precision, analyze experimental results and interpret phenomena qualitatively and quantitively. The concept was embodied through the thesis. Secondly, the heat-transfer characteristics of confined air impinging jet with millimeter-level aperture nozzles were investigated experimentally and analyzed theoretically. It could be demonstrated that the heat transfer performance has the direct relationship with the flow state, velocity distribution and confined degree of impinging jet. Comparison of the experimental results, the non-swirl impinging jet has an excellent local heat transfer performance at the stagnation zone, while the peak value of Nu for the swirl impinging jet exists outward transition phenomena along the radius of impact surface. Furthermore, multi-jets could improve the uniformity of heat transfer in the condition of same flux because that the phenomena of coherence and collision between the jets result in the heat trensfer coefficient not present monotone distribution anymore between stagnation zones.Thirdly, to develop, investigate and use replacer of lead solders is the international trend. So experiments on 96.5Sn3.5Ag-a new lead-free solder were accomplished to discuss the thermo-mechanical behaviors. The conclusion could be drawn that Anand visco-plastic model can be applied to describe the thermo-mechanical behaviors of solder 96.5Sn3.5Ag correctly. Meanwhile, based on the fatigue-characteristic experments and relevant theories involved in dislocation theroy, fracture mechanics, creep-damage theory, et al, the fatigue behaviors of solder were analyzed theoretically. It can be enunciated that absolute temperature has an important effect on failure mechanism of solders and the synergism of creep-damage and fatigue damage brings on fatigue failure of solders. The investigation provides the useful data for thermo-mechanical behaviors and failure mechanism of new-style solders.Exterior heat exchange modes influence parameters distribution inside packaging components, then distinction in thermo-mechanical behaviors exists between operating states and uniform temperature states. So the discussion about the thermo-mechanical behaviors and thermal capability of the component in the operating states could approach the engineering practice more closely. In the operating states, the research of thermal capability on packaging components is involved in multi-field coupling problems. Furthermore, the solders present obvious nonlinear mechanical characteristics such as creep, so the research of thermal capability is also involved in non-linear problems. In this thesis, the coupling mechanism of unsteady temperature and stress fields was discussed. After that, coupling thermal-elastoplastic problems were simplified and decoupled, and the one-way sequential coupling technique was adopted to analyze the unsteady thermal stress inside the solid materials. Besides, based on increment theory, the nonlinear thermo-stress coupling issue and corresponding numerical solution based on Finite Element Method were discussed.According to the theories mentioned above, the transient temperature and stress fields of FC-CBGA electronics packaging component in the operating states were simulated. After that, the method of high-temperature low-cycle fatigue life prediction about pumps in multiaxial stress condition was discussed. In the numerical simulation research, in order to describe the temperature and stress distribution inside the component especially inside the solder bumps more precisely, model of visco-plasticity was applied to describe the thermo-mechanical behaviors of solders and a full size model was built which reconstruct the interior configuration as detailed as possible. Furthermore, some techniques were applied to solve specific problems in simulating. Sub-model method based on local influence theorem was introduced to solve the issues such as grid division, computational precision and efficiency caused by scale level discrepancy among subassemblies inside electronics packaging components and it was proved availably. And sequential coupling technique was adapted to solve coupling problems such as multi-fields coupling, heterophase coupling, inphase coupling, et al.The research provides experimental and theoretical foundation for development of electronics packaging components based on flip bonding and for improvement of thermal performance about electronics packaging components.