Mounting and Packaging

The group develops innovative mounting technology to meet the ever-increasing demands of state-of-the-art semiconductor lasers and microwave devices. Specifically, laser diodes and microwave components are attached to heat sinks and built into more complex housings in our packaging lab. Complete packaged devices can be measured under operating conditions and lifetime-testing can be performed. The results of such packaging and testing are a key part of understanding and optimizing the design of the material.

Packaging plays an important role as an interface between the institute and its partners. The team works closely with FBH's customers, collaborators and research partners, who require not only chips but also assembled devices in order to test and examine the devices within their own applications. State-of-the-art equipment is used to package lasers and microwave devices.

The key challenge in mounting high-power laser chips is to develop technology that ensures very low thermal resistance together with minimal mechanical stress – typically this requires materials that have the same thermal expansion properties as the semiconductor. This is particularly important for long lifetime applications or where devices are repeatedly thermally cycled. For laser devices, another key factor is to ensure that the emitted light is not obstructed: precise, reproducible placement of the laser and well controlled edge properties are critical. For highest performance, the emitting edge of the laser must be well heatsunk to avoid the formation and growth of defects - laser devices produce power densities at the emitting surface (facet) of 20 MW/cm² or higher.

Laser diodes can be mounted as single emitters or as a composite of few emitters (laser bars). For expansion matching purposes, FBH unses composite material such as Cu/W and Cu/Diamond as well as AlN, Si and CVD diamond for submounts. The devices and packages can be assembled together with driver circuits and/or beam shaping optics and other external optical components such as external gratings.

• Die bonding of single lasers and laser bars
• Fluxless soldering in hydrogen atmosphere
• TS Au wire and ribbon bonding
• Coupling of optical components with diode lasers by "active alignment" (Diode laser is working during alignment.)
• Beam collimation (More complex beam shaping, diode laser with external resonator and short wavelength generation by nonlinear effects are treated within the business units Hybrid Laser Systems and Laser Sensors. They use the packaging techniques described here for die attach onto micro optical benches.)
• Development of patterned and solder-coated substrates for submounts and micro-optical benches
• Laser diodes mounted together with HBT driver circuits for optical ps-pulse generation - a combination of laser mounting and micro wave mounting techniques
• Stacked arrays for very high powers

• Pick-and-place die bonder (Weld Equip, Cammax Precima): Reflow soldering of chips onto submounts, heat sinks and packages
• Flip-Chip-Bonder (Finetech) with integrated soldering chamber: High-precision positioning, soldering in vacuum, nitrogen or hydrogen reflow soldering oven with hydrogen enabled chamber (UniTemp GmbH) Soldering of laser benches for space applications and of QCW-Laserstacks
• Flip-Chip-Bonder FC 150 Süss MicroTech: Hybrid Laser Systems, Microwaves
• Automatic Bonder for laser bars BL2000 (ficonTEC Service GmbH): Mounting of laser bars and single emitters.
• Manual Wire Bonder (wedge-wedge, 30°, 90°)  (Marpet Enterprices Inc., Hybond): electrical connections for low power single emitter devices
• Semiautomatic Wire Bonder (Delvotec): Diode lasers > 5 W, micro wave circuits
• Automatic Wire Bonder (Delvotec): Laser bars, micro wave circuits
• IR annealing oven with inert gas or vacuum (UniTemp GmbH): Soldering, annealing, outgassing, high temperature and rapid annealing processes
• Annealing ovens with vacuum or room atmosphere: Annealing, outgassing
• UV-Laser (Innolas): Cutting, scribing, marking, ablation,
• Welding laser StarWeld SELECT (Baasel LASERTECH): Mechanical and electrical connections
• Optical microscopes