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To reduce the cost of soldering materials and alleviate the thermal shock of temperature-sensitive electronic components during board-level packaging process, SnBi(Ag) solder pastes were explored to replace SnAgCu solder pastes due to the feature of low melting temperature of SnBi(Ag) solders. In this study, Sn3.0Ag0.5Cu (SAC305) solder balls as IC pins were assembled with SnBi(Ag) solder pastes in...
High thermo-mechanical stresses are usually induced in through silicon via (TSV) structures due to the mismatch of coefficients of thermal expansion (CTE) between copper and silicon in Cu filled TSVs, which has brought an increasing concern for the reliability problems during fabrication process and operation of electronic devices. The size, shape and orientation of Cu grains in TSVs and their effects...
In order to reduce the cost of solder materials and retard the thermal shock of temperature-sensitive electronic components during packaging process, SnBi solder paste was explored to replace SnAgCu solder paste due to the low melting temperature. In this study, BGA structure Cu/solder-ball/solder-paste/Cu joints were designed and prepared to study the interfacial reactions and microstructural evolution...
The existence of microcracks in solder interconnects plays a key role in determining the performance and reliability of solder interconnects, in particular, may increase significantly the potential for brittle interfacial fracture of interconnects and reduce the thermal conductivity of the systems. Thus, characterization of the formation and propagation of microcracks is very important for evaluating...
Size effect of solder balls on the interfacial reaction and microstructural evolution of BGA structure Cu/Sn3.0Ag0.5Cu-ball/Sn3.0Ag0.5Cu-paste/Cu joints during isothermal aging at 125 °C was systematically investigated. Results show that a large amount of bulk Cu6Sn5 phase distributes in the solder matrix of joints with large solder ball size, resulting from larger outflux Cu atoms from the interface...
The migration and segregation of Bi atoms in Cu/Sn-Bi/Cu solder interconnects under electric current stressing usually induce the formation of Bi-riched layers at the anode side, which can cause the failure of solder interconnects easily. In our study, the microstructure evolution of the eutectic Sn-Bi solder in a Cu/Sn-Bi/Cu flip chip solder joint and a right-angle Cu/Sn-Bi/Cu solder interconnect...
The interfacial reactions and formation of intermetallic compound of Sn-ball/Sn-3.0Ag-0.5Cu-paste/Cu joints in flip-chip on BGA packaging were studied by using a differential scanning calorimeter. Results show that a thin circular Cu6Sn5 layer forms first on the surface of Cu substrate due to the diffusion of Sn atoms dissolved in the soldering flux, subsequently the planar-like Cu6Sn5 layer forms...
The solder joint's volume and interfacial reaction during the soldering significantly affect its solidification behavior and microstructure feature; further, the microstructure of the solder matrix and the intermetallic compounds (IMC) have a direct impact on the performance and reliability of the solder joint. In this study, the effects of the solder volume and interfacial reaction on the undercooling...
Dimension of solder interconnects (or joints) and pitches has been continuously scaling down, resulting in inhomogeneous microstructure and severe electromigration (EM) effect in solder interconnects. In this study, the interaction effect between electromigration and microstructure evolution in ball grid array (BGA) structure Cu/Sn-58Bi/Cu solder interconnects under a direct current density of 1.5×10...
The solder joint's volume and interfacial reaction during the soldering significantly affect its solidification behavior and microstructure feature; further, the microstructure of the solder matrix and the intermetallic compounds (IMC) have a direct impact on the performance and reliability of the solder joint. In this study, the effects of the solder volume and interfacial reaction on the undercooling...
Dimension of solder interconnects (or joints) and pitches has been continuously scaling down, resulting in inhomogeneous microstructure and severe electromigration (EM) effect in solder interconnects. In this study, the interaction effect between electromigration and microstructure evolution in ball grid array (BGA) structure Cu/Sn-58Bi/Cu solder interconnects under a direct current density of 1.5×10...
The interaction effect between electromigration (EM) and microstructure evolution in Cu/Sn-58Bi/Cu solder interconnect with asymmetric configuration along current direction was studied by cellular automaton (CA) modeling embedded with finite element (FE) simulation, with a comparison to in-situ scanning electron microscope (SEM) observation and focus ion beam (FIB) microanalysis. The CA method was...
The influence of the cooling rate and the type of under bump metallization (UBM, i.e., Cu and Ni) on the undercooling and solidification behavior of Sn-Ag-Cu (SAC) based solders (i.e., Sn-1.0Ag-0.5Cu, Sn-3.0Ag-0.5Cu and Sn-3.8Ag-0.7Cu) and their joints was characterized. The results show that the cooling rate has little influence on the undercooling of Sn-1.0Ag-0.5Cu and Sn-3.0Ag-0.5Cu solder balls,...
Isothermal aging effect on the microstructure and mechanical properties of line-type Ni/Sn3.0Ag0.5Cu/Ni sandwich structure interconnects with small heights of 50 and 25 μm was investigated in this study. Microstructural analysis showed that interfacial (Ni, Cu)3Sn4 IMC layer grew thick after aging at 125 °C for 100 h with the formation of local voids and cracks due to volume shrinkage induced by the...
The influence of the pre-existing void in the Cu/Sn-58Bi/Cu solder joint on electromigration behavior was investigated by in-situ SEM observation and focused ion beam (FIB) analysis. The results show that the void with smooth internal surface has no influence on the Bi atom migration, while the one with a sharp notch may easily result in Bi atom congregation and further lead to the formation of cracks...
Mg-doped (Li, Na, K)NbO3 lead-free piezoelectric ceramics with a nominal composition of [Li0.06(Na0.5K0.5)0.94](Nb0.198Mg0.005)O3 (LNKNM) was prepared by normal sintering method. The microstructure and electrical properties were studied with a special emphasis on the influence of sintering temperature in the range of 920-1020degC. A MPB bridging tetragonal and orthorhombic symmetry was found as the...
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