Underfill Flow in Flip-Chip Encapsulation Process: A Review

Abstract

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.

Advances on Thermally Conductive Epoxy‐Based Composites as Electronic Packaging Underfill Materials—A Review

“…According to the flip‐chip packaging processes, current underfill materials can be mainly classified into capillary underfill, no‐flow underfill, and molded underfill materials. Owing to its straightforwardness and simplicity, lower chances to form defects of incomplete fillings and voids, and better compatibility for a range of underfill fluids and package designs, the capillary underfill process has been widely adopted in practical applications [ 7 ] and covers more than 60% of the underfill market. [ 8 ] In a typical capillary underfill process, liquid resin is dispensed along the periphery of the attached chip.…”

Capillary Underfill Flow Simulation as a Design Tool for Flow-Optimized Encapsulation in Heterogenous Integration

“…Unlike traditional approaches, this method eliminates the need for custom molds and subsequent processing steps. Nonetheless, ensuring a defect-free underfill application presents a critical challenge, given that both reliability and production throughput are significantly impacted by void formation and prolonged filling times [12]. Hence, it becomes imperative to not only tweak the material attributes of the underfill but also refine dispensing patterns and incorporate modifications in package designs to improve flow dynamics throughout the filling process.…”

Numerical Simulation of Laser Soldering Process on Pin Through Hole (PTH)

“…This is because comparison is required to verify the validity of this study to know the range of the results. The numerical analysis results are essential for better understanding of relevant researchers and engineers in the electronic industry [9].…”