Fraunhofer Institute for Laser Technology ILT
Fraunhofer Institute for Laser Technology ILT

Laser-based packaging

© Fraunhofer ILT, Aachen.

Since they apply energy locally, laser-based packaging processes help progressively increase the integration density of highly sensitive, functional elements in miniaturized microsystems. Processes such as laser soldering, glass solder bonding, laser beam bonding for transparent and metallic materials or microwelding are precise joining technologies that meet the constantly growing requirements in the packaging sector.

Laser beam soldering, for example, is a method that offers high flexibility in the production of high-density circuits; it improves the thermal performance of electronic components. By precisely controlling the laser beam, high-strength connections can be produced, ensuring reliable and durable chip assembly.

Glass frit bonding

Laser-based glass solder bonding opens up new perspectives for integrating glass substrates in microelectronic designs. Precise melting and bonding using laser radiation creates robust and hermetically sealed housings that offer excellent long-term stability and protection against external influences.

The laser-based bonding process is based on using a glass solder that absorbs laser radiation and causes a locally defined input of radiation energy. This selective energy input, which is limited to the joining zone, makes it possible to produce resilient, hermetic encapsulations without thermally stressing and damaging the highly sensitive, functional elements. Process times of just a few seconds are typical for the encapsulation of small systems.

© Fraunhofer ILT, Aachen

Micro welding

Laser beam microwelding is a precise and gentle method used to join thin metal components in microelectronics. Targeted energy input from the laser achieves localized heating, which ensures that the melt is controlled, thereby joining the components without damaging adjacent ones. Thus, joining zones with weld seam widths < 200 µm can be achieved with very low temperature stress on the overall component. The process is, therefore, particularly suitable for encapsulating microsystems with moving structures and thermally sensitive components.

Laser beam bonding

Laser beam bonding is based on the principle of transmission joining and is suitable for joining glass-glass, glass-silicon and silicon-silicon wafers with a high surface quality. The two wafers are joined, with one of the wafers transmitting the laser radiation, while the second or an applied intermediate layer absorbing it. The absorbed radiation is converted into thermal energy, which induces a local melting process and creates a material bond.

However, metallic materials can also be welded together using laser beams, a technology that generates reliable, high-strength bonds for electronic components. This method enables the fast and precise joining of materials of different types and thicknesses without the need for additional solder alloys or fluxes.

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© Fraunhofer ILT, Aachen / Andreas Steindl.

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