Search Results (4)

The increasing integration and miniaturization of electronic devices place serious pressure on packaging technologies to ensure long-term reliability. Polymer underfill encapsulation is a key process for reducing thermomechanical stress in modern assemblies. A systematic analysis that frames its diverse methods as solutions to the fundamental trade-off between the final polymer composite’s thermomechanical performance and its liquid-state processability is lacking from the literature. The novelty of this review lies in establishing a decision-making framework that connects specific application requirements to the underlying material science and process limitations. This article analyzes and compares different underfill techniques through a systematic literature review, from conventional capillary flow to advanced wafer-level underfills. Our findings show that this core trade-off leads to three distinct strategies: (1) Maximum reliability: This is achieved with highly filled, post-applied composites, offering excellent thermomechanical properties at the cost of slow, viscosity-driven manufacturing speeds. (2) High productivity: This is realized through integrated, pre-applied processes that simplify manufacturing but impose significant constraints on the polymer chemistry and filler content. (3) Targeted reinforcement for board-level packages: At the localized positions applied, ductile polymers often enhance mechanical shock resistance. This review concludes that the optimal underfill choice is not universal but is a complex, application-driven decision balancing the cured material’s performance against the processing demands of the polymer system. Full article

As the power electronics landscape evolves, pushing for greater vertical integration, capillary underfilling is considered a versatile encapsulation technique suited for iterative development cycles of innovative integration concepts. Since a defect-free application is critical, this study proposes a capillary two-phase flow simulation, predicting both the flow pattern and velocity with remarkable precision and efficiency. In a preliminary performance evaluation, Volume of Fluid (VOF) outperforms the Level-Set method in terms of accuracy and computation time. Strategies like HRIC blending, artificial viscosity, and implicit Multi-Stepping prove effective in optimizing the numerical VOF scheme. Digital mapping using physical experiments and virtual simulations validates transient flow predictions, achieving excellent agreement with deviations as low as 1.48–3.34%. The accuracy of flow predictions is thereby greatly influenced by non-Newtonian viscosity characteristics in the low shear range and time-dependent contact angle variations. The study further explores flow manipulation concepts, focusing on local flow speed adjustment, gap segmentation, and the use of arcuate shapes to influence interface confluence near the chip. Experimental validation corroborates the effectiveness of each design intervention. In conclusion, this research highlights the potential of predictive engineering to develop flow-optimized package designs that enhance reliability while supporting high manufacturing yields. Full article

In this study, the effects of a hybrid filler composed of zero-dimensional spherical AlN particles and two-dimensional BN flakes on the thermal conductivity of epoxy resin were studied. The thermal conductivity (TC) of the pristine epoxy matrix (EP) was 0.22 W/(m K), while the composite showed the TC of 10.18 W/(m K) at the 75 wt% AlN–BN hybrid filler loading, which is approximately a 46-fold increase. Moreover, various essential application properties were examined, such as the viscosity, cooling rate, coefficient of thermal expansion (CTE), morphology, and electrical properties. In particular, the AlN–BN/EP composite showed higher thermal stability and lower CTE (22.56 ppm/°C) than pure epoxy. Overall, the demonstrated outstanding thermal performance is appropriate for the production of electronic packaging materials, including next-generation flip-chip underfills. Full article

In this study, a thermal conductivity of 0.22 W·m⁻¹·K⁻¹ was obtained for pristine epoxy (EP), and the impact of a hybrid filler composed of two-dimensional (2D) flake-like boron nitride (BN) and zero-dimensional (0D) spherical micro-sized aluminum oxide (Al₂O₃) on the thermal conductivity of epoxy resin was investigated. With 80 wt.% hybrid Al₂O₃–BN filler contents, the thermal conductivity of the EP composite reached 1.72 W·m⁻¹·K⁻¹, increasing approximately 7.8-fold with respect to the pure epoxy matrix. Furthermore, different important properties for the application were analyzed, such as Fourier-transform infrared (FTIR) spectra, viscosity, morphology, coefficient of thermal expansion (CTE), glass transition temperature (T_g), decomposition temperature (T_d), dielectric properties, and thermal infrared images. The obtained thermal performance is suitable for specific electronic applications such as flip-chip underfill packaging. Full article