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Viscoplastic finite-element simulation was used to predict reliability of solder joints in a high temperature 4-chips stacked capacitor mounted on a PCB under temperature cycling (-55°C to +125°C, 45min ramps/60min dwells). A three-dimensional (3D) model was built considering the materials properties of a commercial component. Capacitor materials w...
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... have been prepared and observed by using scanning electron microscopy (SEM, JEOL JSM-6100) and energy dispersive x-ray spectroscopy (EDX, Oxford Inca X-act). The he EDX spectrum (Figure 2-a) indicates the presence of the elements Barium (Ba), Titanium (Ti) and Oxygen (0) in the dielectric layers, which means that they are composed by barium titanate (BaTi03) derived materials. More accurate quantitative analyses, carried out on the ceramics only, revealed a small amount of bismuth (Bi) ( Table 1). ...
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... Tables 1 and 2 summarize the material parameters, namely the Young's modulus, coefficient of thermal expansion (CTE), and electrical conductivity for the Ni electrode and dielectric material applied in the MLCC modeling; the dielectric is based on the BaTiO 3 ceramic. [19][20][21][22][23][24][25][26][27][28]. Figure 6 presents the analysis results of the ANSYS Maxwell 3D and ANSYS Icepak software to obtain the temperature result of the MLCC according to the ripple current flow. Figure 6a, b present the ohmic loss value of MLCC owing to current flow (10 kHz, 1A), and the Joule heating value, respectively. ...
Heat generation with decrease in multilayer ceramic capacitor (MLCC) device size proves problematic in various fields. Herein, we performed heating temperature measurements according to various MLCC sizes and several finite element analysis (FEA) simulations to improve the self-heating characteristics. For the experiments, 1005, 1608, and 2012 size MLCCs with a 1-µF capacitance were selected, and temperature changes were measured using a ripple current test at 10 kHz. The thermal resistance (Rt) and equivalent series resistance (ESR) of the 1005, 1608, and 2012 MLCCs were determined to be 94 °C/W and 92 mΩ, 86 °C/W and 69 mΩ, and 82 °C/W and 37 mΩ, respectively. The experimental results confirm that the ESR value and MLCC size significantly influence thermal resistance due to ripple current. To improve the heat generation characteristics due to ripple current, an FEA model was constructed considering the dielectrics, conductors, and design parameter characteristics to verify the temperature changes according to ESR and MLCC size. After application of ripple current from the measured ESR value through the ANSYS Maxwell 3D software, the extracted ohmic loss value was converted to the ANSYS Icepak software to verify the temperature change value. Resultantly, a measured temperature change and simulation result error range of within 1% were obtained. For MLCC incorporation in applications such as 5G network equipment and electric vehicles, considering reliability characteristics, the internal stress and heat flux values were analyzed using the ANSYS mechanical software as per temperature change according to MLCC size, volume, and ripple current. The results confirmed that with MLCC volume increase, the internal heat flux increased according to the temperature change, temperature increase was suppressed owing to the smooth heat flux, and the internal stress appeared smaller.
