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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]

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]

Abstract: This paper presents an innovative polishing process aimed at leveling rough surface of plating-based flip chip solder bumps so as to get uniform coplanarity across the whole substrate after both electroplating and reflow processes. This polishing mechanism is characteristic of combining mechanical-dominated polishing force with slight chemical reaction together. A large number of extremely but inevitably rugged mushroom-like structures after electroplating are drastically smoothed down with the help of this newly-developed polishing process. Nearly 70μm solder bumps in height with two different profiles as square and circle on the substrates reach as flatly as ±3μm between different substrates after reflow process; ±2.5μm in single substrate; and even ±1μm in die, respectively. Besides, surface roughness among the solder bumps is simultaneously narrowed down from Ra 0.6 to Ra 0.03 along with the coplanarity improvement. Excellent uniformity and smooth surface roughness in solder bumps are absolutely beneficial to pile up and deposit in the following steps in MEMS and semiconductor fields. [Copyright &y& Elsevier]

Abstract: A novel method (the V-shaped curve) is presented to predict the failure probability of anisotropic conductive film (ACF) in IC/substrate assemblies. The Poisson function is used to calculate the probability of opening failure in the vertical gap between the pads, while the box and modified box models are used to estimate the probability of bridging failure between the pads in the pitch direction. The opening and bridging probabilities are combined using probability theory to establish four different failure prediction models. The results reveal that the model combining the Poisson function for fewer than six particles per pad with the modified box model provides the most accurate predictions of the failure probability of ACF in IC/substrate assemblies. [Copyright &y& Elsevier]