Together for clean contacts
A specialist for snow jet cleaning and a supplier for ultrasonic wire bonding solutions join forces. With combined know-how, they are developing fully automated solutions for clean wire bonding of battery cells.
Ultrasonic wire bonding has been established in the microelectronics and semiconductor industry for many years, including for the electrical interconnection of battery cells. F&S Bondtec Semiconductor GmbH supplies fully automatic and manual wire bonders and bond testers to companies in the microelectronics and semiconductor industries. In contrast, applications in the production of battery packs, for example for electromobility, are comparatively new for the company, which was founded in 1994. One of the advantages of wire bonding is the high reliability and durability of the connections. "A prerequisite, however, is a consistently high level of cleanliness of the bonding surfaces," explains Johann Enthammer, technical manager at F&S Bondtec. Problems are caused by particulate and chemical-film contamination, for example due to organic contamination or oxidation. But also varying storage conditions or a different storage time of the cells can affect the bondability. "In order to be able to offer customers from the automotive and supplier industry added value, we were looking for an effective, integrable and comparatively inexpensive cleaning solution," reports Johann Enthammer.
Enthammer found what he was looking for at Productronica 2019 with booth neighbor acp systems AG, developer and manufacturer of the quattroClean snow jet cleaning technology. Together with the company, F&S Bondtec conducted trials. "On the one hand, we achieved reproducibly convincing results. On the other hand, the cleaning process does not cause any mechanical changes to the bond surface, as we observed in trials with laser cleaning," says Johann Enthammer, citing some of the reasons that were decisive for the cooperation with acp systems.
The cleaning medium for this dry process is liquid, climate-neutral carbon dioxide. It is passed through a two-substance ring nozzle and expands as it emerges to form fine snow particles. They are bundled by a separate compressed air jacket jet and accelerated to supersonic speed. When the cleaning jet impinges on the surface to be cleaned, the four active mechanisms - thermal, mechanical, solvent and sublimation effect - ensure that organic contaminants and particulate contaminants are reliably and reproducibly removed down to the submicrometer range. After cleaning, the surface has the required properties for bonding. The surfaces are dry after cleaning and can be immediately fed into the wire bonding process.
Fully automated inserts
The compact quattroClean system enables fully automated integration of the cleaning process, for example in the 86 series bonding machines for large-area battery packs. The nozzle is mounted on the bonding head and integrated into the machine control system so that all surfaces to be bonded are approached in a path-control-optimized manner and cleaned in a controlled manner. Solutions for manual cleaning and bonding can be implemented, as can complete production lines with automated parts handling. To ensure consistently good results, the snow jet consistency at each nozzle is monitored by a sensor system. All determined values are automatically stored and can be transferred to a higher-level system.
acp systems AG www.acp-systems.com
F&S Bondtec Semiconductor GmbH www.fsbondtec.at