Technical Library | 2007-05-31 19:05:55.0
This paper discusses solder paste printing and flux dipping assembly processes for 0.4 and 0.5mm pitch lead-free WLCSPs and the corresponding assembly results and thermal cyclic reliability obtained. Variables evaluated include reflow ambient, paste type, and stencil design. Reliability is also compared to results for the same components assembled under identical conditions using SnPb solder.
Technical Library | 2017-10-12 15:45:25.0
The risk associated with whisker growth from pure tin solderable terminations is fully mitigated when all of the pure tin is dissolved into tin-lead solder during SMT reflow. In order to take full advantage of this phenomenon, it is necessary to understand the conditions under which such coverage can be assured. A round robin study has been performed by IPC Task group 8-81f, during which identical sets of test vehicles were assembled at multiple locations, in accordance with IPC J-STD-001, Class 3. All of the test vehicles were analyzed to determine the extent of complete tin dissolution on a variety of component types. Results of this study are presented together with relevant conclusions and recommendations to guide high reliability end-users on the applicability and limitations of this mitigation strategy.
Technical Library | 2014-07-10 17:37:18.0
This paper studies and compares the effects of pull–pull and 3-point bending cyclic loadings on the mechanical fatigue damage behaviors of a solder joint in a surface-mount electronic package.The comparisons are based on experimental investigations using scanning electron microscopy (SEM) in-situ technology and nonlinear finite element modeling, respectively. The compared results indicate that there are different threshold levels of plastic strain for the initial damage of solder joints under two cyclic applied loads; meanwhile, fatigue crack initiation occurs at different locations, and the accumulation of equivalent plastic strain determines the trend and direction of fatigue crack propagation. In addition, simulation results of the fatigue damage process of solder joints considering a constitutive model of damage initiation criteria for ductile materials and damage evolution based on accumulating inelastic hysteresis energy are identical to the experimental results. The actual fatigue life of the solder joint is almost the same and demonstrates that the FE modeling used in this study can provide an accurate prediction of solder joint fatigue failure.
Technical Library | 2021-07-13 19:59:34.0
We have investigated the processing of lead-zirconate-titanate-based thick films by inkjet printing Pb (Zr0.53Ti0.47)0.98Nb0.02O3 with a 6 mol% excess of PbO nanosized powder dispersed in water. Differentwaveforms were employed to determine the optimum size and shape of the drops. A uniform, defect-free pattern with dimensions of 4 mm × 4 mm can be printed using 20 V and a drop spacing of 20 μm. The inkjet-printed films were heated to 400 °C to remove the organics and subsequently sintered at 750 and 850 °C. The correlations between the density, grain size and electromechanical properties of the thick films and bulk ceramics are qualitatively discussed. A thickness coupling factor of 46% was obtained for a 15-μm-thick film sintered at low temperature of 850 °C, which is comparable to the value of the bulk ceramic with an identical nominal chemical composition. Our results are important for the economic and environmental-benign printing of piezoelectric materials applicable in variety of electronic devices, such as sensors, actuators, transformers, piezoelectric energy harvesters and transducers.
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