Micro-LEDs, which have a chip size of less than 100 × 100 μm², have been potential candidates for conventional LCDs and OLEDs due to their high optical power, outstanding stability, and nanosecond response time. However, Micro-LED chips are fabricated only on limited substrates due to the high-temperature metal-organic chemical vapor deposition process and lattice-mismatch issues. Therefore, the fabrication of Micro-LED displays requires complex processes such as chip fabrication, transfer, bonding, and repair. Especially, Micro-LED transfer and bonding have been critical challenges for the Micro-LED display commercialization. Here, recent advances in the transfer and bonding of Micro-LEDs are introduced, and novel Micro- LED display fabrication methods are reviewed to provide a practical outlook for both mass production and commercialization of Micro-LED displays.

In this study, solder joints mixed with graphene-nanosheets (GNSs) were investigated for the manufacture of highly reliable electronic devices. In order to analyze the effect of adding GNSs, experiments were performed by adding various amounts of GNSs (0.01, 0.05, 0.1, 0.3, 0.5 wt%). To compare and analyze the properties of the solder joints to which GNSs were added, shear forces were measured, and cross-sectional observation was performed. The bonding strength of the solder joints containing 0.05% GNSs was the highest, and the bonding strength of the solder joints with higher GNSs contents did not increase. This is because, as the content of GNSs increases, the viscosity of the solder paste also increases; therefore, the solder paste detachability from the metal mask was lowered and a sufficient amount was not applied. In addition, due to the high content of GNSs, the fluidity of solder powder and paste decreased, resulting in defects in the shape of the solder joint. Therefore, the optimal GNSs content in this study was 0.05%, and studies for optimal viscosity should be continued.

As packaging processes for atomic gyroscope vapor cells, the glass tube tip-off process, anodic bonding, and paste sealing have been widely studied. However, there are stability issues in the alkali metal which are caused by impurity elements and leakage during high-temperature processes. In this study, we investigated the applicability of a vapor cell low-temperature packaging process by depositing Au on a Pyrex cell in addition to forming an Au-Sn thin film on a cap to cover the cell, followed by laser irradiation of the Au/Au-Sn interface. The mechanism of the thin film bonding was evaluated by XRD, while the packaging reliability of an Ne gas-filled vapor cell was characterized by variation of plasma discharge behavior with time. Furthermore, we confirmed that the Rb alkaline metal inside the vapor cell showed no color change, indicating no oxidation occurred during the process.

This study investigated the various physical and electrical effects of silicon direct bonding. Direct bonding means the joining of two wafers together without an intermediate layer. If the surfaces are flat, and made clean and smooth using HF treatment to remove the native oxide layer, they can stick together when brought into contact and form a weak bond depending on the physical forces at room temperature. An IR camera and acoustic systems were used to analyze the voids and bonding conditions in an interface layer during bonding experiments. The I-V and C-V characteristics are also reported herein. The capacitance values for a range of frequencies were measured using a LCR meter. Direct wafer bonding of silicon is a simple method to fuse two wafers together; however, it is difficult to achieve perfect bonding of the two wafers. The direct bonding technology can be used for MEMS and other applications in three-dimensional integrated circuits and special devices.

Current progress in the development of semiconductor technology in applications involving high electron mobility transistors (HEMT) and power devices is hindered by the lack of adequate ways todissipate heat generated during device operation. Concurrently, electronic devices that use gallium nitride (GaN) substrates do not perform well, because of the poor heat dissipation of the substrate. Suggested alternatives for overcoming these limitations include integration of high thermal conductivity material like diamond near the active device areas. This study will address a critical development in the art of GaN on diamond (GOD) structure by designing for ideal heat dissipation, in order to create apathway with the least thermal resistance and to improve the overall ease of integrating diamond heat spreaders into future electronic devices. This research has been carried out by means of heat transfer simulation, which has been successfully demonstrated by a finite-element method.

In this study, the characteristics and error ranges of the mechanical bonding strength were analyzed according to before and after thermal shock test for various chips of automotive application component using Sn-3.0Ag-0.5Cu solder. In the after thermal shock test, the mechanical bonding strengths tend to decrease, meanwhile decreasing rates of mechanical strengths were less then 12% at specimen`s bonding area below 3.5mm2, and were from 17 to 21% at specimen`s bonding area above 12 mm2. On the other hand, Specimen`s mean deviation rates were about 5% at specimen`s bonding area more than 12 mm2. Inversely, at specimen`s bonding area is less then 3.5 mm2, mean deviation rates were increased to about 8%. It means that the smaller device size is, the larger mean deviation rate. In addition, error ranges and deviation rates of the mechanical bonding strengths may differ slightly depending on their bonding area. Furthermore, process conditions as well as method of mechanical reliability evaluation should be established to reduce the error ranges of bonding strength.

In this paper, the following results were obtained from the experiment in which electrification voltage of silicone rubber specimen for thermal bonding were measured under various time, temperature (10~40℃), and humidity (30~90%) conditions and different amount of carbon additives (0~15 phr (per hundred resin)). Electrostatics electrification voltage decreased when carbon is up to 10 phr, and there was no electrification voltage in 15 phr condition. The electrostatics electrification voltage did not change over time. When the temperature was constant, electrostatics electrification voltage sharply dropped when the humidity was around 70%. That means, this condition might be appropriate for prevention of charging. The electrification voltage decreased as humidity and amount of carbon increased.