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Gallium Oxide (Ga 2 O 3) holds significant potential for the next generation of electronic devices following SiC and GaN due to its ultra-wide bandgap of approximately 4.5 eV - 4.9 eV and high theoretical critical breakdown field strength of 8 MV/cm. Nonetheless, Ga 2 O 3 has a naturally low thermal conductivity, resulting in limited device output performance and hindering Ga 2 O 3 devices from reaching their full theoretical potential. In this study, we demonstrate that the appropriate thermal management strategy can solve the above challenges. By comparing the thermal control schemes including the Ga 2 O 3 FET devices on the original substrate, the thinned Ga 2 O 3 substrate, the high thermal conductivity substrate, the heat sink packaging, and the flip-chip packaging, it is demonstrated that the flip-chip model is the most effective strategy to improve the heat dissipation performance of the Ga 2 O 3 device. By utilizing the appropriate carrier in flip-chip packaging, the temperature elevation of the device at 2 W/mm power density will be diminished by around 91% in contrast to the initial basic device. Furthermore, the output performance of the device demonstrates significant enhancement. This thermal management technique successfully resolves the severe heat dissipation issue prevalent in Ga 2 O 3 devices and eliminates primary obstacles concerning the industrialization of Ga 2 O 3 RF and power devices. • Establishing a thermoelectric coupling model to solve the problem of Ga 2 O 3 transistor thermal management. • Replacing the native substrate is not an optimal solution to the thermal problem of Ga 2 O 3 transistors. • The chip flip packaging can greatly improve the heat dissipation performance of Ga 2 O 3 devices. [ABSTRACT FROM AUTHOR]

Interfacial reactions in Sn/Ni-4.5 wt.%Si and Sn-Cu/Ni-4.5 wt.%Si couples at 250°C, and Sn-Ni-Si ternary phase equilibria at 250°C were investigated in this study. Ni-Si alloys, which are nonmagnetic, can be regarded as a diffusion barrier layer material in flip chip packaging. Solder/Ni-4.5 wt.%Si interfacial reactions are crucial to the reliability of soldered joints. Phase equilibria information is essential for development of solder/Ni-Si materials. No ternary compound is present in the Sn-Ni-Si ternary system at 250°C. Extended solubility of Si in the phases NiSn and NiSn is 3.8 and 6.1 at.%, respectively. As more Si dissolves in these phases their lattice constants decrease. No noticeable ternary solubility is observed for the other intermetallics. Interfacial reactions in solder/Ni-4.5 wt.%Si are similar to those for solder/Ni. Si does not alter the reaction phases. No Si solubility in the reaction phases was detected, although rates of growth of the reaction phases were reduced. Because the alloy Ni-4.5 wt.%Si reacts more slowly with solders than pure Ni, the Ni-4.5 wt.%Si alloy could be a potential new diffusion barrier layer material for flip chip packaging. [ABSTRACT FROM AUTHOR]

Microelectromechanical systems (MEMS)-type double helix chip-level electrical interconnect structures are fabricated and characterized in this paper. Due to their springlike structure, double helix interconnects have the potential to provide large mechanical compliance to compensate for nonidealities, such as nonplanarity and thermal expansion mismatch between silicon chips and substrates. A double helix configuration provides for structures with a high volumetric density of conductor for enhanced current carrying capability. The fabrication process is compatible with wafer-level fabrication and packaging. Instead of using solder to form semipermanent interconnections, the double helix interconnects use pressure to make electrical connection and provide sufficiently low resistance (~35 ± 15 mΩ). Large arrays of double helix structures have been fabricated and characterized with excellent yield. The mechanical and electrical models of the structures are presented. Reworkability tests were performed and the structures show a consistent resistance over 50 remating cycles. [ABSTRACT FROM AUTHOR]

Abstract: Packaging technology used in liquid crystal displays (LCDs) faces the critical issues such as high density interconnects, thinner packaging size, and environmental safety. In order to reduce the packaging size, driver integrated circuit (IC) chips are directly attached to LCD panels using flip chip technology with adhesives, which is called chip on glass (COG) packaging processes. To investigate the effects of the bonding force and bonding temperature on the flip chip thermal-compression packaging, this study established a compression model to analyze the flip chip packaging processes with non-conductive adhesives (NCAs). The plastic deformation of bumps and the NCA flow dynamics between chip and substrate were taken into account in this model. The gap height, bump deformation, bump contact area, and residual stresses after bonding can be estimated with this model. According to the simulation in this work, the best tactic for the flip chip packaging process using NCA is bonded at a lower temperature. This reduces the maximum warpage and only slightly decreases the average compressive residual stress in the bottom of bumps. A larger bonding force results in a larger bump contact area with the substrate, but has a lower compressive residual stress at the contact areas. The bonding force during the flip chip thermal bonding process will affect the contact resistance and reliability of packaging at the same time. [Copyright &y& Elsevier]