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In this paper, wafer level transfer of graphene on to a dielectric substrate is demonstrated based on SiO2-SiO2 fusion bonding and de-bonding processes. The developed technique allows to transfer graphene on 200 mm wafer without any contamination; thus CMOS compatible. The experimental data verifies the successful transfer of the graphene on to another substrate with high quality and a yield value...
Several types of interconnects for the finer pitch assembly are currently being investigated across the globe. Here in this paper, a new type of interconnect Ni3Sn4 Interconnect is proposed and evaluated for assembly at 10 pitch and below. The proposed interconnect is compared to traditional solder interconnect. The comparison is done on the basis of shape of the joints in interconnects, the electric...
Predominant high melting point solders for high temperature electronics contain lead (Pb), which will soon be banned by environmental regulations as in most of consumer electronics. In an effort to replace the Pb-based solders with a new high-temperature capable material, we developed a transient liquid phase (TLP) bonding of bismuth (Bi) and nickel (Ni). A molten Bi (m.p. of 271°C) strongly reacts...
Microbump-based interconnects with 20 µm pitch have been fabricated on 300 mm wafers using industrial tools. Good processes control enables to get narrow standard deviations for the microbumps height (0.2 µm) and diameter (0.4 µm). Assembly was studied with chip to wafer (CtW) test vehicles by either mass reflow (MR) or thermo-compression (TC) with or without non-conductive paste (NCP). MR and TC...
The advanced electronic device trends are changing to be more and more light weighted and miniaturized. And due to the rapid growth of wearable electronic industry, demands for flexible packaging are growing, and advanced flexible interconnection methods are required. In order to satisfy the needs, fine pitch Flex-on-Flex (FOF) assembly has been introduced, because FOF can reduce not only the package...
Aiming for application to the inverter system of HEV and EV, we have developed a novel packaging technique for SiC power devices based on Nickel Micro Plating Bonding (NMPB) technique. We implemented heat resistant mounting of SiC schottky barrier diode (SBD) on the TO247 type package and confirmed the rectifying behavior even after the high temperature storage for 500hr at 250°C without any significant...
In recent years, Sn-Bi solders get much attention because low temperature bonding technique is possible to reduce warpage of package and stress at solder joining. However, few studies attempted to their reliability and knowledge of microstructure of the solder bump. In this study, we investigated the difference of inter-metallic compounds (IMCs) formation between Sn57wt%Bi solder (Sn-Bi eutectic solder)...
With regulations mandating industry toward Pb-free solders in all electronics, the development of interconnecting materials capable of withstanding harsh thermal conditions becomes one of the key technological elements for the development of next generation wide band-gap semiconductors. By reflowing Ni/Sn/Ni interconnects under temperature gradient, a new transient liquid phase (TLP) bonding process...
In this study, we investigated effects of thermal gradient of joint during flip chip bonding on intermetallic compound (IMC) growth for several solder materials. Cu/Sn-2.5Ag/Cu joint was prepared by bonding electroplated Cu/Sn-2.5Ag bump on Cu pad. Ni/Sn/Ni, Ni/In/Ni, Ni/In-48Sn/Ni, and Ni/Sn-58Bi/Ni joints were prepared by solder capping by IMS on electro-less plated Ni/Au post and bonding it on...
The improvement of interconnection technology is becoming a top priority for the operation of high power devices such as SiC at higher temperatures. We proposed a interconnection method using Nickel Nano-particles direct bonding to form bonds between the chip electrodes and substrates. SiC devices assembled with the Ni bonding interconnection were confirmed to be operated successfully in a high temperature...
Processing of bump-less or embedded microbumps is introduced in this paper as an approach which enables scaling microbumps for below 10um pitches. Landing wafer is standard damascene process and in top wafer bumps are embedded in a soft backed polymer. Later during thermo-compression bonding this polymer is cured to bond two chips together. Process flow and results of TC bonding is discussed in this...
Recently, copper wires have been attracting much attention for LSI (Large Scale Integration) bonding because of its excellent mechanical and electrical properties, and low material cost. On the other hand, the end of these wires are usually joined to the pads or through-holes on the printed circuit board, and lead-free soldering is one of the popular bonding methods. Since the solders are weaker than...
A novel low-temperature, pressureless bonding approach by electroless plating with controlled flow through a microfluidic device, in which a laminar forced convection flow of electroless solution was passing through a microchannel between dies and to gaps between copper pillars, was developed to metallically interconnect copper pillars together. Previous study had been demonstrated that, with the...
In this paper the influence of adding ELD barrier and capping layers in die shear strength of 3D stacked chips is discussed. Electroless NiB is used as barrier layer to prevent solder or UBM consumption and immersion Au is used as capping layer to improve the solder wettability. In this study UBM layers are Cu, Co and Ni and pure Sn is used as solder. For bonding both reflow and TCB methods are employed...
Recently, the eco-friendly vehicles such as Hybrid Electric Vehicle (HEV) and Electric Vehicle (EV) have been spotlighted. EV has power semiconductors which generate a lot of heat. So, the power semiconductors have to guarantee reliability because it is driven at high temperature. Furthermore, it was able to be driven at a higher temperature by developing the semiconductor devices such as SiC and...
For the purpose of process R&D on inter-die vertical connection for 3D integration, the role of ultrasonic vibration in forming a low-temperature bonding joint needs to be studied in-depth. Rather than focusing on the ultrasonic-induced interfacial reactions by molten solder, this study used low power ultrasonics to bond solder with flat Ni and microcone-structured Ni substrates respectively under...
In this article, an approach is explained to controlling the Young's modulus of bonding layers formed using a Transient Liquid Phase (TLP) process. The three focus points of this research include: 1) development of a new bond microstructure for thermal stress mitigation, i.e. Young's modulus reduction, 2) a novel approach to the preparation of bulk specimens for mechanical property tests, and 3) mechanical...
In this paper a bump-less process is introduced in order to further scale down the pitch of microbumps. Electrical resistance measurement, Cross section SEM and mechanical characterizations show successful 3D stacking using proposed method.
This study developed a low temperature soild-state direct bonding process for dissimilar metals. Experimental results show that Cu/Zn can be bonded successfully at 200°C under the loading of 10MPa for 30 minutes. The joints thus formed exhibited a shear strength up to 20MPa. If the thermal compression was performed at 300°C, the shear strength of bonded Cu/Zn and Cu/Ni/Zn joints exceeded 50MPa, especially...
High bonding temperature and force are known to cause physical damage to the device. The objective of this present study is to develop a new low-temperature and pressureless bonding method for Cu-to-Cu interconnects using electroless Ni plating. Two plating methods were employed to test the feasibility of electroless bonding of copper pillars. The first method was carried out in a stirred plating...
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