Joint Research Projects

Study In Vietnam

Bonding Materials and Processes for High-Temperature Electronics





Professor Nishikawa is the faculty at Joining & Welding Research Institute, Osaka University, Japan. Professor Nishikawa is mainly working on Composite material – interfaces, Material processing, Microstructure control, Electronics devices & Equipment’s.

High temperature electronics (HTEs) have been used in many applications recently, such as under the hood for exhaust gas sensors, oil and gas exploration and production combustion engines in automobile and in exposed areas of an aircraft (150°C to 350°C). Even HTEs are used for space exploration (the surface of Venus is 485 °C). Besides, recent advances in semiconductor technology have greatly increased the operating temperature of semiconductor devices which high temperature device chips built on SiC and GaN-based semiconductors have demonstrated operating temperatures higher than 350°C. For example, the operating temperature of SiC power devices can be 465 °C or higher.



The research on high temperature electronics and bonding materials is followed by several kind of processes. One of them is highlighted here. To do the bonding test, two kinds of Cu disks are used. One is oxygen free Cu disk and another one is electroless Ni immersion Au finished Cu disk. There are two different kind of sample dimension can be used to do the experiment. Before bonding, need to follow several steps for the surface smoothness and cleanliness. For the bonding heated in the furnace is required. Different kind of heat treatment with different temperature is needed. After that shear test is conducted to evaluate the strength of the disk joint. The shear strength was estimated by average of different trials. TEM is used to get the cross-sectional views of the joint specimens.



In the nitrogen & air atmosphere the bonding test is performed & observed the ambient effect. For many different conditions the specimen was treated. Shear test can be done for the evaluation of the joint strength of the specimen. From the experiment can observe the difference of the shear strength between two atmospheres. In air, the shear strength of the oxygen-free Cu disk is much lower than that of the ENIG disk. The shear strength of the oxygen-free Cu disk in air was less than 15 MPa, while that of the ENIG disk was around 30 MPa. These kinds of result we can expect from the experiment.



A joining process using a chestnut-burr-like mi-croscale Ag particle paste was developed as a replacement for high-lead-containing solders in high-power devices. All the particles were deformed from a burr-shape to a spherical shape and numerous adjacent particles were sintered together after heating by varying time. Under a nitrogen atmosphere, the shear strengths of the oxy-gen-free Cu and ENIG disc joints were more than 20 and 30MPa, respectively.