The Packaging group constructs modules to demonstrate the capabilities of the optical and optoelectronic devices which are developed at Fraunhofer HHI. This includes optical fiber coupling as well as electrical interfaces with RF connectors.
Additionally they design and construct tailor-made module prototypes or submounts for all external partners and customers.
The module planning process begins with a 3D model of the whole assembly. The group either designs a customized housing or selects a standard BTF type depending on the usage and numbers required. Even small volumes of customized housings can be cost-efficiently constructed in the in-house workshop.
Fraunhofer HHI is experienced in using many coupling and fiber variants such as:
- Active and passive coupling
- Single mode and multimode fibers
- Polarization maintaining fibers
- Tapered fibers, butt fibers and customized arrays
- Lens coupling
The electrical connections of their chips include, alongside the biasing, the RF signal routing from the chip to the connector for frequencies up to 100 GHz and beyond.
The required circuit carriers are designed and produced on the premises:
- For applications up to 20 GHz we use laser structuring of metallized ceramic substrates which allows fast and individualized production
- When a higher degree of precision is necessary, electroplating of lithographically generated structures is used by the packaging group. Using ebeam lithography equipment makes this process fast and individually customizable as well.
The equipment to connect chips and interposers with various wire bonding and flip chip processes is also available:
- Gold and aluminum wire
- Ball and wedge bonding
- Deep access bonding
- Wire thicknesses from 17.5µm
- Manual or automated
- RF capable bonding up to 100 GHz
- AuSn and SAC reflow
- Pastes and conductive adhesives
- Solder preforms
- AuSn sputtering
For chip assembly the group uses, alongside soldering, a large selection of adhesives whose mechanical, optical, thermal and electrical characteristics are tailored to the application in question. The montage is carried out manually or using machine assisted techniques to sub-micron positioning accuracy.