An Osaka University professor has developed a pressureless sintering joining technology to aid next-gen power semiconductors made up of gallium nitride (GaN).
According to Professor Suganuma Katsuaki from Osaka’s Institute of Scientific and Industrial Research, the low-temperature pressureless die bonding can be used for all types of electrodes, including copper (Cu) and gold (Au), as well as silver coating.
The new development – which owes its fruition to Katsuaki’s prowess in improving the conductor’s silver paste – has resulted in a low-cost, reliable heat-resistant mounting technology for die attach and for printed wiring without changing a conventional cheap electrode structure.
The technology has also proven to withstand temperatures over 250°C with no lax in reliability.
Nickel/gold (Ni/Au) or copper (Cu) are often used for electrodes for silicon (Si), silicon carbide (SiC) and gallium nitride (GaN) semiconductors as well as direct bonded copper (DBC) substrates. Thus, bonding to Ni/Au or Cu electrodes is in high demand within the semiconductor industry.
Katsuaki’s group, in collaboration with chemical company Daicel Corporation, developed a solvent to promote interfacial activation of silver (Ag), achieving pressureless sintering technology of joining various electrodes even at 200°C, lower than that of conventional technology.
With this new type of solvent (paste), a low electrical resistivity of 4×10-6Ωcm, about two times of that of Ag, was achieved, which can only be obtained with Osaka’s-silver paste.
In conventional power semiconductor fabrication processes, films are often used instead of paste as a die attach material. This group developed technology to activate the surface of an Ag film by grinding it.
The researchers further contend that their technology could help in reducing energy loss during power conversion, which is characteristic of SiC and GaN power semiconductors.
Image and content: Osaka University/Suganuma Laboratory