Parametric Study on the Void Risk in FC-POP Molded Underfill Process Using a Novel Porous Media, Two-Phase, Compressible Flow Simulation Method

Lee, Moon Soo; Baick, Inhak; Jeong, Min Suk; Kim, Min; Kwon, Seo Hyun; Yeo, Myeong Soo; Rhee, Hyug-Gyo; Pae, Sangwoo

doi:10.1109/tdmr.2020.2985209

Cited by 3 publications

(2 citation statements)

References 11 publications

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“…Many attempts have been made to minimize and eliminate the void defects. Vacuum moulded underfill was applied to the flip-chip package underfill process [12]. The simulation model predicts the void size and its characteristics via computational fluid dynamics [11 & 12] in the Flip-chip PoP.…”

Section: Introductionmentioning

confidence: 99%

Package-on-Package (Pop) Underfill Process Using a Material Dam Method

Ali

Khor²,

Azmi³

et al. 2022

AEJ

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Recent developments in the electronics industry have introduced a multi-stack ball grid array (BGA) to meet the growing consumer demand for both high-performance and smaller-sized chip packages. This study focused on the preliminary study of the Package-on-Package (PoP) underfill process using a material dam method. High viscosity type of underfill material is considered for the underfill process. In the current experimental work, L path-dispensing method was chosen due to its advantages, as reported in the previous work. The material dam method was used to prevent underfill from moving backwards and flowing out from the dispensing region. The material dam was built surrounding the PoP package. The effectiveness of the underfill process was analyzed based on the cycle time and lateral lapping, which are significant factors in material selection. The experimental results revealed that slow underfill flow may cause the quickly harden of material while the dispensing process is still running. This situation restricts the underfill flow and creates voids in the PoP package. The material dam method successfully enhanced the underfilling process for layers 3 and 4 stacked-package. This study is expected to provide the preliminary underfill process of stacking the PoP package and is useful as a reference for the engineer in the microelectronics industry.

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Section: Introductionmentioning

confidence: 99%

Package-on-Package (Pop) Underfill Process Using a Material Dam Method

Ali

Khor²,

Azmi³

et al. 2022

AEJ

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show abstract

“…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). Moreover, the curing stage was studied numerically to predict the package warpage (Lin and Lee, 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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Advancing packaging technology: computational fluid dynamics modeling for capillary underfill encapsulant in multi-chip heterogenous packages

Azman,

Abdullah,

Loh

et al. 2024

SSMT

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Purpose The purpose of this study is to investigate the dynamics of capillary underfill flow (CUF) in flip-chip packaging, particularly in a multi-chip configuration. The study aims to understand how various parameters, such as chip-to-chip spacing (S12), chip thickness (tc) and others, affect the underfill flow process. By using computational fluid dynamics (CFD) simulations and experimental studies, the goal is to provide insights into understanding the dynamics of CUF in heterogeneous electronic packaging. Design/methodology/approach The paper introduces a CFD analysis and experimental study on CUF in a multi-chip configuration, aiming to understand underfill flow dynamics. A 3D geometry models of multi-chip arrangement are created using computer-aided design (CAD) software. After that, the CAD models are meshed and simulated in Ansys Fluent using incompressible and non-Newtonian fluid properties. The study maintains S12 of 2.86 and tc of 22.29 between experimental and simulation data for results validation. Next, a various of S12 values (1.14, 2.86, 5.71, 8.57, 14.29 and 20) which focus on tc of 22.29 have been investigated. Further studies have been conduct using S12 of 5.71 and tc of 8.00, 14.29 and 22.29. Findings Results show a strong correlation between simulation and experiment which validate the correctness and robustness of simulation. Further parameter’s studies using simulation for various of S12 indicated that higher S12 values lead to faster flow. This effect is due to large underfill weight from reservoir able to flow into S12 region which contributed to higher mass momentum movement. Furthermore, the effect of various of tc shows that the thicker the chip the faster the underfill to flow in S12 region. Research limitations/implications The intentional exclusion of solder bump pattern arrangements from the experiment and simulation may limit the study's ability to fully understand the impact of solder bump patterns on underfill flow. Therefore, more parameters can be investigated such as solder bump pattern, underfill weight and dispense pattern in the future using CFD. Practical implications The manuscript provides a comprehensive examination of the contributions of CFD to the advancement of knowledge regarding CUF phenomena in heterogeneous electronic packaging assemblies. Moreover, it delineates the utilization of CFD methodologies to assess the influence of chip-to-chip spacing (S12) and the thickness of the chip (tc) on the underfill flow characteristics. Originality/value This paper fulfills an identified need of computational fluid dynamics method to study capillary underfill flow dynamics in heterogenous electronic packaging.

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Parametric Study on the Void Risk in FC-POP Molded Underfill Process Using a Novel Porous Media, Two-Phase, Compressible Flow Simulation Method

Cited by 3 publications

References 11 publications

Package-on-Package (Pop) Underfill Process Using a Material Dam Method

Package-on-Package (Pop) Underfill Process Using a Material Dam Method

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

Advancing packaging technology: computational fluid dynamics modeling for capillary underfill encapsulant in multi-chip heterogenous packages

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