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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]

Purpose This paper aims to demonstrate the improved functionality of additive manufacturing technology provided by combining multiple processes for the fabrication of packaged electronics.Design/methodology/approach This research is focused on the improvement in resolution of conductor deposition methods through experimentation with build parameters. Material dispensing with two different low temperature curing isotropic conductive adhesive materials was characterised for their application in printing each of three different conductor designs, traces, z-axis connections and fine pitch flip chip interconnects. Once optimised, demonstrator size can be minimised within the limitations of the chosen processes and materials.Findings The proposed method of printing z-axis through layer connections was successful with pillars 2 mm in height and 550 µm in width produced. Dispensing characterisation also resulted in tracks 134 µm in width and 38 µm in height allowing surface mount assembly of 0603 components and thin-shrink small outline packaged integrated circuits. Small 149-µm flip chip interconnects deposited at a 457-µm pitch have also been used for packaging silicon bare die.Originality/value This paper presents an improved multifunctional additive manufacturing method to produce fully packaged multilayer electronic systems. It discusses the development of new 3D printed, through layer z-axis connections and the use of a single electrically conductive adhesive material to produce all conductors. This facilitates the surface mount assembly of components directly onto these conductors before stereolithography is used to fully package multiple layers of circuitry in a photopolymer. [ABSTRACT FROM AUTHOR]

With the rapid growth of the microelectronic packaging market, it is necessary to increase the throughput and reduce the cost of flip chip. Driven by these evolutions, a novel revolving-turret chip transferring (RTCT) technology is introduced to implement high-throughput flip chip packaging. The unnecessary time delays of packaging processes could be eliminated in the RTCT technology due to its parallel manner of motions. In order to analyze the packaging efficiency, the layout and movement sequence of the packaging system are studied, and a calculation model of packaging efficiency is proposed. Furthermore, the effects of the critical parameters (the horizontal and the vertical spacing of antennas and the maximum velocity and acceleration of the turret-type head) on packaging efficiency are investigated to search out the optimal parameters combination. To verify the performance of the RTCT technology under optimal parameters combination, two cases are implemented and compared. The results show that due to parallel motions of processes, unnecessary delays affecting the packaging efficiency have been reduced, and the packaging efficiency of ALN-9714 inlay could be more than 35k chips per hour. In addition, compared with the conventional flip chip packaging process, the RTCT technology is more effective in packaging the chips on antennas with multicolumn layout and small horizontal spacing. [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]

This study investigated the influence of different injection types, such as I-type, L-type, and U-type, on the dynamic behavior of capillary-driven encapsulation flows for a commercially available flip chip. The dynamic filling behavior of underfill encapsulation was visualized experimentally, and numerical simulations were conducted for three-dimensional flows in a flip chip package by using commercial software (ANSYS FLUENT Ver. 13.0). Numerical results were compared with experimental data for the filling time and the rate of change in underfill volume fraction with different injection types. At the early stage of underfill injection, the estimated flow characteristics exhibited high capillary acceleration that rapidly decreased with time, which indicates that capillary force was dominant in underfill encapsulation. The capillary pressure drop effect was dominant at the early stage. Thus, the injection method for underfill encapsulation inside the flip chip should be carefully controlled for faster and more stable encapsulation to avoid void formation in the chips. [ABSTRACT FROM AUTHOR]

Electronics packaging based on stress-engineered spring interconnects has the potential to enable integrated IC testing, fine pitch, and compliance not readily available with other technologies. We describe new spring contacts which simultaneously achieve low resistance (<100~m\Omega) and high compliance (>30~\mum) in dense 2-D arrays (180–180-\mum pitch). Mechanical characterization shows that individual springs operate at approximately 150-\muN force. Electrical measurements and simulations imply that the interface contact resistance contribution to a single contact resistance is <40~m\Omega. A daisy-chain test die consisting of 2844 contacts is assembled into flip-chip packages with 100% yield. Thermocycle and humidity testing suggest that packages with or without underfill can have stable resistance values and no glitches through over 1000 thermocycles or 6000 h of humidity. This paper suggests that integrated testing and packaging can be performed with the springs, enabling new capabilities for markets such as multichip modules. [ABSTRACT FROM AUTHOR]

This paper focuses on the packaging process and assembly and interlayer dielectrics (ILD) structural stability including mechanical simulation with polymer-encapsulation and redistribution process for 150-µm pitch Pb-free flip chip packaging of low-k/Cu interconnects. Chemical vapor deposition (CVD) type low-k test vehicles with four Cu layers were fabricated using Cu dual damascene process. Polymer encapsulation and metal redistribution (RDL) technology were applied using wafer integration technology to minimize the stress from the solder bump pad to low-k ILD. This polymer encapsulated dicing line (PEDL) was introduced and the result of investigation discussed. Finite element method (FEM) mechanical simulations are per- formed for RDL approach, normal direct bumping, and PEDL. According to the results with shear loading, RDL approach showed less stress than that of direct bumping at the solder joint. Simulation indicated the die corner stress is reduced significantly on chip with PEDL as compared to that without PEDL. For copper postinterconnects, cost-effective and thick photoresist process was developed and optimized for electro Cu plating and solder was deposited on the top of Cu post. Bump shear test was carried out to evaluate the bump quality and failures were analyzed. After flip chip assembly with Cu/low-k devices having via-chain and daisychain interconnects, various JEDEC standard reliability tests were carried out and failure analysis was performed. [ABSTRACT FROM AUTHOR]

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]