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Microjoining Lab
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A lab studying joining materials and processes for electronics packaging.
AboutAbout the lab
Studying microscale joining in electronics.
The Microjoining Lab conducts research and education on microjoining in electronics packaging.
It covers a broad range, from developing new joining materials to establishing joining processes, clarifying their mechanisms, and evaluating reliability, advancing both fundamental science and applied technology.
The lab actively accepts international students and research students from overseas, and also pursues international collaborative research with universities and research institutions abroad.
The lab belongs to the Joining and Welding Research Institute, and is also a cooperating chair (Microjoining Engineering Chair) of the Division of Materials and Manufacturing Science in the Graduate School of Engineering.
Key terms
- Electronics packaging
- Technology for connecting electronic components to boards and assembling them into electronic devices.
- Lead-free solder
- An alloy that does not use lead and is used to join metals together.
- Solid-state bonding
- A method of joining in which the materials are not melted, and atoms move across the bonding interface while the materials remain solid.
NewsLab news
Associate Professor Tatsumi held a press conference on a joining technology for insulating substrates for power semiconductors
Associate Professor Tatsumi received the Minister of Economy, Trade and Industry Award (10th Monozukuri Nippon Grand Awards)
Associate Professor Tatsumi and a master's student received the MES2025 Best Paper Award and a Research Encouragement Award, respectively
An undergraduate student received the "Engineering Award" of the School of Engineering, Osaka University
ResearchResearch themes
The lab studies microscale joints such as the solder used in electronics packaging, covering materials, processes, and evaluation. Research topics include developing low-temperature solder alloys, building highly heat-resistant joints using three-dimensional nanostructures, and clarifying interfacial bonding mechanisms through atomic-scale simulation.
*Illustrative imageImproving Low-Melting-Point Lead-Free Solder Joints
The widely used Sn-Ag-Cu solder has a high melting point, and lower-temperature joining is in demand. Focusing on Sn-Bi eutectic solder, which melts at 138°C, among others, the lab works on improving its properties by adding trace amounts of elements.
*Illustrative imageSolder Joining with New Heat Sources Such as Lasers
Demand is growing for heat sources, such as semiconductor lasers, that heat a localized area in a short time. The lab evaluates and improves the microstructure and impact properties of solder bumps heated by laser.
*Illustrative imageDeveloping Joining Technologies to Replace High-Temperature Solder
Solder with a high Pb content, used in power modules and similar applications, needs to be replaced with alternatives that do not use hazardous substances. The lab conducts fundamental research on new sintering-type joining technologies that use insert materials with nanostructured surfaces or micro-sized metal particles.
*Illustrative imageClarifying Solid-State Bonding from Atomic Motion
As semiconductor devices become smaller and more functional, solid-state bonding is attracting attention as an alternative to conventional soldering. To achieve bonding at low temperature in a short time, the lab reproduces and studies the movement of atoms at the bonding interface using molecular dynamics and first-principles calculations.
MembersFaculty
The members of the Microjoining Lab consist of faculty, technical assistants, administrative assistants, and doctoral, master's, and undergraduate students.As of 2026
- ProfessorHiroshi Nishikawa
- Associate ProfessorHiroaki Tatsumi
- Assistant ProfessorMakoto Iioka
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Report an errorAbout the images
The top and research theme images are illustrative and were not taken at the lab. They are cropped from Wikimedia Commons images. Cropped CC BY-SA images are provided under the same CC BY-SA license as the original (version shown on each line).
- Top image: “Electronic Printed Circuit Board” JayHand / CC BY-SA 3.0 (cropped)
- Improving Low-Melting-Point Lead-Free Solder Joints: “Soe self-solder sleeve 5” Lead holder / CC BY-SA 4.0 (cropped)
- Solder Joining with New Heat Sources Such as Lasers: “Laser soldering machine” Mauro Cateb / CC BY-SA 4.0 (cropped)
- Developing Joining Technologies to Replace High-Temperature Solder: “DC to DC Power Module ( )” Razor512 / CC BY 2.0 (cropped)
- Clarifying Solid-State Bonding from Atomic Motion: “Diffusion Bonding Fixture for Combustion Chamber 01” Romanusas2 / CC BY-SA 4.0 (cropped)
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- Related lab (レーザプロセス学分野): “Laser welding of the pipeline” Barbara Nasiłowska / CC BY 4.0 (cropped)
- Related lab (エネルギー制御学分野): “Energy Arc (central electrode of a Plasma Lamp)” Blaise Frazier aka PiccoloNamek / CC BY-SA 3.0 (cropped)
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