Numerical modelling of the delamination in multi-layered ceramic capacitor during the thermal reflow process

Abstract

Purpose This paper aims to study the interfacial delamination found in the boundary of the copper/copper-epoxy layers of a multi-layer ceramic capacitor. Design/methodology/approach The thermal reflow process of the capacitor assembly and the crack propagation from the initial micro voids presented in the boundary, and later manifested into delamination, were numerically simulated. Besides, the cross section of the capacitor assembly was inspected for delamination cracks and voids using a scanning electronic microscope. Findings Interfacial delamination in the boundary of copper/copper-epoxy layers was caused by the thermal mismatch and growth of micro voids during the thermal reflow process. The maximum deformation on the capacitor during reflow was 2.370 µm. It was found that a larger void would induce higher vicinity stress, mode I stress intensity factor, and crack elongation rate. Moreover, the crack extension increased with the exerted deformation until 0.3 µm, before saturating at the peak crack extension of around 0.078 µm. Practical implications The root cause of interfacial delamination issues in capacitors due to thermal reflow has been identified, and viable solutions proposed. These can eliminate the additional manufacturing cost and lead time incurred in identifying and tackling the issues; as well as benefit end-users, by promoting the electronic device reliability and performance. Originality/value To the best of the authors’ knowledge, the mechanism of delamination occurrence in a capacitor during has not been reported to date. The parametric variation analysis of the void size and deformation on the crack growth has never been conducted.

Investigation of moisture-induced crack propagation in the soft-termination multi-layer ceramic capacitor during thermal reflow process

“…After the reflow process and when the heat is no longer applied, these deformations would be reversed, but at different rates for each layer. This thermal mismatch of both copper-electrode and copper-epoxy layers leads to the cracking (Ng et al , 2022b), manifested as a gap, due to the uneven thermal expansions between adjacent copper-electrode and copper-epoxy layers as shown in Figure 11. In the absence of the copper-epoxy layer, the adjacent copper-electrode layer and nickel layer would undergo similar deformations, as their CTEs are 14.8 ppm/°C and 12.8 ppm/°C, respectively.…”

“…To the best of the authors’ knowledge, previous studies by Lee and Yoon have investigated the reliability of soft-termination MLCCs with additional ag-epoxy (Lee and Yoon, 2022). In addition, Ng has conducted numerical modelling of delamination at the copper/copper-epoxy layers of MLCCs during the reflow process (Ng et al , 2022a). However, the work was conducted without focusing on moisture-induced crack propagation in MLCC.…”

Deformation and crack growth in multilayered ceramic capacitor during thermal reflow process: numerical and experimental investigation

“…Various researchers have applied numerical and experimental fracture mechanics techniques to examine the defect growth behavior of soldered electronic packages in a thermal environment. Fatigue fracture behavior in various copper/lead-free solder junctions that had been thermally aged is examined in Zhang et al (2010), Ng et al (2022). In Hofmeister et al (2008), fracture mechanics was used to study the propagation of initial voids and cracks to establish the defects growth phenomena in integrated circuit (IC) components and solder joints.…”

“…Despite the notable contributions in the literature on fracture mechanics of electronic packages, a few research studies (Ahmar and Wiese, 2017; Ng et al , 2022; Bachok et al , 2023; Jin Kim et al , 2007; Tao et al , 2017; Apalowo et al , 2023) exist on the experimental study of thermally reflowed ceramic capacitors. Furthermore, a limited number of works (Ng et al , 2022; Bachok et al , 2023; Apalowo et al , 2023) considered the fracture growth phenomenon during thermal reflow of soft-termination MLCCs. Also, only one (Apalowo et al , 2023) of the limited studies subjected the soft-termination MLCC to multiple (accelerated) thermal reflow.…”

“…Considering the significant impact of subjecting the MLCC to an accelerated thermal reflow on its thermal reliability (IPC/JEDEC, 2023), the current work investigates fracture deformation and delamination cracks in soft-termination MLCC when subjected to an accelerated thermal reflow. The current work also examines the growth mechanism of the interfacial crack; this was not considered in the previous works (Ng et al , 2022; Bachok et al , 2023; Apalowo et al , 2023) on the subject matter.…”