Disperse phase method particle study with doped nano-particles in sac305 solder
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Date
2018-08-01
Authors
Siti Haslinda Mohamed Said
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Abstract
Nowadays, most electronic devices consist of miniature components, therefore, to ensure high durability and strength on the assembly of these miniature joints and components can represent huge challenges to the product designer. Vast amount of researches have been concerted to the usage of nano-reinforced Sn-3.0Ag-0.5Cu (SAC305) lead free solder that is introduced to the solder paste for the improvement of the current lead free alloy but the study is limited to experimental findings only. With the inclusion of nanoparticles in the lead free solder, the trajectory of the nanoparticles throughout the soldering process needs to be monitored since it will influence the formation of the fillet height, inter-metallic compound (IMC) layer and micro-void formation. A two way interactions utilizing both volume of fluid method (VOF) and disperse phase method (DPM) are introduced in the current study to account for the interaction between both the nanoparticles and the molten solder. The nano-reinforced particles that are introduced in the SAC305 solder are titanium oxide (TiO2), nickle oxide (NiO) and Iron (III) oxide (Fe2O3) nanoparticles with an approximate diameter of ≈20nm at different weight percentages of 0.01, 0.05 and 0.15 wt.% for application to ultra-fine 01005 type capacitor. Both experimental and simulation studies were conducted to compare the validity of the new DPM based simulation. The results obtained from the experiment can effectively visualize the distribution of the nanoparticles at the end of the reflow process. The DPM simulation on the other hand is capable of showing detail trajectory of the nanoparticles as it undergoes SAC305 thermal reflow. Additionally, good agreement can be seen between both experimental and simulation data obtained for all cases of nanoparticles being used. The fillet height of the nano-reinforced solder also managed to meet the minimum requirement for 01005 capacitor as set by the Association Connecting Electronics Industries (IPC) standards. The findings also show that 0.05wt% of NiO nanoparticles has the lowest wetting time with 2.65s. Additionally, for 0.05wt% of Fe2O3, the trajectory of nanoparticles are well distributed leading to inhibition of void formation and thin IMC layer. The introduction of the nanoparticles in the SAC305 have also shown further retardation on the growth of IMC layer that is favorable since it is aligned with the main requirement of having a thin layer of IMC. Subsequently, this can contribute to good wettability of the solder and managed to inhibit micro-voids formation due to the higher pressure distribution that can promote the flow front propagation of the wetted solder. The study of two-ways interaction of both VOF and DPM models showed the viability of the simulation approach in simulating the miniature soldering process of the molten solder with nanoparticles and can provide a useful alternative to the conventional costly experimental approach.
Keywords:
SAC305; Nanocomposite solder paste; Nanoparticles; Titanium oxide (TiO2); Nickle oxide (NiO); Iron (III) oxide (Fe2O3); Numerical simulation; Finite volume method (FVM) ; Disperse phase method (DPM).