FR AUNHOFER INSTITUTE FOR ELEC TRONIC NANO SYSTEMS ENAS

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January 26, 2022 || page 1 | 3

Inductive bonding – A new bonding method inmicrosystems technology

The Fraunhofer Institute for Electronic Nano Systems ENAS is developing a
new bonding technology for microsystems in cooperation with Chemnitz
University of Technology and SHINKO ELECTRIC INDUSTRIES CO., LTD. The
chip-level inductive bonding process will be presented for the first time atMEMS Sensing & Network System 2022 in Tokyo.
Inductive joining is a technology that has so far mainly been used only for macroscopic components, such as steel tubes or car doors. Fraunhofer ENAS, togetherwith Chemnitz University of Technology and the Japanese company SHINKO, is now
developing a process that enables inductive bonding on the micro level for the firsttime. A bonding process based on sintering paste with silver micro particles wasdeveloped for the mechanical surface contacting of chips on DBC (direct bondedcopper) substrates.

I N C O O P E R AT I O N W I T H

Multi-chip array
Ag paste
ENIG layer
DBC substrate
Multi-chip set up with all components. (Image © Fraunhofer ENAS)

Editors
Dr. Martina Vogel | Fraunhofer Institute for Electronic Nano Systems ENAS | Phone +49 371 45001-203 |Technologie-Campus 3 | 09126 Chemnitz | Germany | www.enas.fraunhofer.de | martina.vogel@enas.fraunhofer.de
Person in charge
Christian Hofmann | Fraunhofer Institute for Electronic Nano Systems ENAS | Phone +49 371 45001-496 |Technologie-Campus 3 | 09126 Chemnitz | Germany | www.enas.fraunhofer.de | christian.hofmann@enas.fraunhofer.deFR AUNHOFER INSTITUTE FOR ELEC TRONIC NANO SYSTEMS ENAS

A wide range of advantages can be exploited here, especially in the heterogenous
integration of chips and components. The inductive process enables very rapid
heating of targeted structures, for example bond pads, which are joined to thebond partner at a high local temperature. The temperature input occurs primarily
locally in the areas of the induction coils, so that the surrounding structures andcomponents, as well as the entire substrate, are significantly less thermally affectedby the very rapid heating and cooling of the local structures.

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January 26, 2022 || page 2 | 3

IR image of inductive heating of the multi-chip setup with Ag paste array onto the DBC substrate.
The target temperature of 300 °C is reached in only five seconds. (Image © Fraunhofer ENAS)

Bonding processes of silicon chips on a DBC substrate have already been successfully carried out with silver sintering pastes. Using induction coils, geometricallyadapted to the bond structures, a high-frequency electromagnetic field induces
eddy currents in the electrically conductive silver particle pad. Heating rates of morethan 100 K/s were thus generated. The overall process time is decisively reducedwith this method, since the target temperature of 300 °C is reached in only fiveseconds.
As part of the research work, a test setup consisting of a process chamber with asintering module, a pressure plate and an infrared camera for process monitoring
was developed. The sintering module contains a water-cooled induction coil in anelectrically insulating surrounding material. By means of process monitoring, thecoil current and the operating frequency are recorded in real time.

The Fraunhofer Institute for Electronic Nano Systems ENAS is the specialist and development partner in the field of Smart Systems and theirintegration for various applications. Fraunhofer ENAS has specialized on the challenge of combining micro and nano sensors, actuators and electroniccomponents with interfaces for communication and a self-sufficient energy supply to form smart systems, thus supporting the Internet of Things andthe ongoing digitalization. The institute develops single components, manufacturing technologies and system concepts, system integration technologies and actively supports the technology transfer for and with its customers. It offers innovation consulting and supports customer projects, startingfrom the idea, via design and technology development or realization based on established technologies up to tested prototypes.

FR AUNHOFER INSTITUTE FOR ELEC TRONIC NANO SYSTEMS ENAS

Induction coil

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January 26, 2022 || page 3 | 3

Water connection
Rogowski coil
Multi chip setup
Coil housing (GL®P)
Insulator (polymer)
Adapter plate
Sintering module assembly with individual components. (Image © Fraunhofer ENAS)

This process is revolutionary, especially for manufacturers of power electronics
assemblies, as the duration of bonding processes is significantly reduced and thethermal influence on all bonding components is reduced. The mechanical contacting by silver sintering pastes allows the high waste heat of the components to bedissipated quickly and specifically via the sintered structures. The company Shinko
offers the process as an industrialized method and is continuously developing theprocess together with the project partners of Chemnitz University of Technology
and Fraunhofer ENAS.
At the trade show MEMS Sensing & Network Systems in Tokyo Big Sight from Jan
26 until 28, the process will be presented at the joint booth of Tohoku University
and Fraunhofer ENAS (hall 2, booth 2D-05).
A paper on inductive chip bonding can be requested under the following contact:events@enas.fraunhofer.de (Subject: Paper inductive bonding).

The Fraunhofer-Gesellschaft, headquartered in Germany, is the world’s leading applied research organization. With its focus on developing key
technologies that are vital for the future and enabling the commercial exploitation of this work by business and industry, Fraunhofer plays a central
role in the innovation process. Based in Germany, Fraunhofer is an innovator and catalyst for groundbreaking developments and a model of scientific excellence. By generating inspirational ideas and spearheading sustainable scientific and technological solutions, Fraunhofer provides scienceand industry with a vital base and helps shape society now and in the future. Founded in 1949, the Fraunhofer-Gesellschaft currently operates
75 institutes and research institutions. The majority of our 29,000 staff are qualified scientists and engineers who work with an annual researchbudget of 2.8 billion euros. Of this sum, 2.4 billion euros are generated through contract research.