Effect of hourglass shape solder joints on underfill encapsulation process: numerical and experimental studies

Nashrudin, Muhammad Naqib; Gan, Z. L.; Abas, Aizat; Ishak, M. H. H.; Ali, M. Yusuf Tura

doi:10.1108/ssmt-10-2019-0028

Cited by 8 publications

(4 citation statements)

References 23 publications

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“…Both the main constituents in underfill fluid of epoxy resin and silica fillers were separately considered to establish a two-way fluid-solid interaction with the aim to visualize the epoxy flow and filler particle distribution during the underfill flow stage [5]. On the contrary, other numerical studies on filler distributions were either based on the cured underfill package [64] or at the completion of underfilling [65] In the recent years, particle-based LBM was used to simulate the underfill flow, which had seen various applications in conventional capillary underfill [12,17,45,46,48,66,67], mold underfill [68,69], and pressurized underfill [70]. While both LBM and FVM numerical findings are comparable in terms of flow visualization and filling time aspects, it is reported that LBM-based simulation can simulate the void formation during underfill flow for which FVM-based simulation is incapable to achieve [46].…”

Section: Numerical Simulationmentioning

confidence: 99%

Underfill Flow in Flip-Chip Encapsulation Process: A Review

Abas

2021

Journal of Electronic Packaging

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The scope of review of this paper focused on the pre-curing underfilling flow stage of encapsulation process. A total of 80 related works has been reviewed and being classified into process type, method employed, and objective attained. Statistically showed that the conventional capillary is the most studied underfill process, while the numerical simulation was mainly adopted. Generally, the analyses on the flow dynamic and distribution of underfill fluids in the bump array aimed for the filling time determination as well as the predictions of void occurrence. Parametric design optimization was subsequently conducted to resolve the productivity issue of long filling time and reliability issue of void occurrence. The bump pitch was found to the most investigated parameter, consistent to the miniaturization demand. To enrich the design versatility and flow visualization aspects, experimental test vehicle was innovated using imitated chip and replacement fluid, or even being scaled-up. Nonetheless, the analytical filling time models became more accurate and sophiscasted over the years, despite still being scarce in number. With the technological advancement on analysis tools and further development of analytic skills, it was believed that the future researches on underfill flow will become more comprehensive, thereby leading to the production of better packages in terms of manufacturing feasibility, performances, and reliability. Lastly, few potential future works were recommended, for instance, microscopic analysis on the bump-fluid interaction, consideration of filler particles and incorporation of artificial intelligence.

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Section: Numerical Simulationmentioning

confidence: 99%

Underfill Flow in Flip-Chip Encapsulation Process: A Review

Abas

2021

Journal of Electronic Packaging

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“…Among these approaches, the solder bump interface stands out as a promising bonding technology due to its capacity for achieving a high-density connection, coupled with proficient electrical conductivity and effective heat dissipation in flip-chip technology [4]. Nonetheless, the advancement of flip-chip technology is confronted by a significant reliability hurdle, the occurrence of voids or sluggish filling within the solder bumps positioned between the silicon chip and the organic substrate [5][6][7][8]. This predicament can give rise to gradual underfilling processes, imposing substantial stresses on the solder bump interconnects.…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical study of solder bumps impact on the underfill fluid flow under electrohydrodynamic effect

Hassan,

Khalil,

Khan

et al. 2023

Phys. Scr.

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Solder bumps can increase filling time, which is one of the main challenges in electronic packaging reliability. Here, we compare the capillary flow behavior between parallel plates with and without solder bumps to examine how solder bumps affect the length of the underfill fluid flow under the effects of an electric potential. We found that the solder bumps restrained the flow length, while the electric field enhanced it. By enhancing the voltage from 0 to 1000 V, in the case without solder bumps, the flow length increased by up to 30%, and it increased by up to 25% in the case of solder bumps. To determine the optimum bump design, we selected the diameter and pitch size of the solder bumps as the independent variables. The results revealed that larger pitch sizes and smaller diameters show longer fluid flow lengths. The effect of the electric field on varying nozzle positions was also investigated. We found that the fluid flow length increased when the nozzle was between the solder bumps compared to the top of the solder bumps. According to our observations, the nozzle position is also the main factor in determining the fluid flow length compared with the bump diameter and pitch sizes for the design of the underfill packaging process. Numerical simulations were also performed to compare the experimental results, and the average discrepancy between the experimental and numerical results at various time steps for different solder bump parameters was between 5 to 10%. Our findings demonstrate the potential of using electric potential in conjunction with solder bumps to control underfill flow, which can benefit flip-chip packaging applications. Numerical methods can accurately predict underfill fluid flow with solder bumps under the electric field effect.

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“…In the postunderfill stage, the interfacial adhesion of copper/underfill was studied (Andre et al, 2020). Subsequently, the underfill flow in the package was modelled numerically (Ishak et al, 2020;Nashrudin et al, 2020), experimentally (Huang et al, 2020) or analytically (Ng et al, 2020). The void defect formed during the underfilling flow was also numerically simulated (Lee et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Surface energetic-based analytical filling time model for flip-chip underfill process

Abas

2021

SSMT

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Purpose This paper aims to present new analytical model for the filling times prediction in flip-chip underfill encapsulation process that is based on the surface energetic for post-bump flow. Design/methodology/approach The current model was formulated based on the modified regional segregation approach that consists of bump and post-bump regions. Both the expansion flow and the subsequent bumpless flow as integrated in the post-bump region were modelled considering the surface energy–work balance. Findings Upon validated with the past underfill experiment, the current model has the lowest root mean square deviation of 4.94 s and maximum individual deviation of 26.07%, upon compared to the six other past analytical models. Additionally, the current analytically predicted flow isolines at post-bump region are in line with the experimental observation. Furthermore, the current analytical filling times in post-bump region are in better consensus with the experimental times as compared to the previous model. Therefore, this model is regarded as an improvised version of the past filling time models. Practical implications The proposed analytical model enables the filling time determination for flip-chip underfill process at higher accuracy, while providing more precise and realistic post-bump flow visualization. This model could benefit the future underfill process enhancement and package design optimization works, to resolve the productivity issue of prolonged filling process. Originality/value The analytical underfill studies are scarce, with only seven independent analytical filling time models being developed to date. In particular, the expansion flow of detachment jump was being considered in only two previous works. Nonetheless, to the best of the authors’ knowledge, there is no analytical model that considered the surface energies during the underfill flow or based on its energy–work balance. Instead, the previous modelling on post-bump flow was based on either kinematic or geometrical that is coupled with major assumptions.

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Effect of hourglass shape solder joints on underfill encapsulation process: numerical and experimental studies

Cited by 8 publications

References 23 publications

Underfill Flow in Flip-Chip Encapsulation Process: A Review

Underfill Flow in Flip-Chip Encapsulation Process: A Review

Experimental and numerical study of solder bumps impact on the underfill fluid flow under electrohydrodynamic effect

Surface energetic-based analytical filling time model for flip-chip underfill process

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