Technology core competence:

The DieMount core competence is fiber chip coupling of electro-optical semiconductor dice and optical waveguides. The novel process allows to achieve high precision by passive coupling mechanism even for large volume fabrication. In this way it is feasible to fabricate low cost but quality optical transceiver modules for local access data transmission systems even in large numbers.

The following sequence shows schematically the applied process.

• In the first step the electro-optical semiconductor die is aligned by passive coupling precisely to a  microstructured submount and contacted electrically.

• Next a coupling element is mounted on the microstructured submount by press fit assembly.

• Subsequently the optical waveguide is aligned via the coupling element precisely to the submount.

• In summary the novel setup technology allows the very precise coupling of the optical waveguide with the electro-optical die.

"Thick" optical waveguides with a core diameter of about 700µm and more (like e.g. the 1mm polymer optical fiber, POF) benefit in addition by a parabolic microreflector that is integrated to the microstructured submount in the process. As a consequence the coupling efficiency of semiconductor die and optical waveguide is increased up to factor 5 in comparison to conventional butt coupling.

Typical technology process to fabricate a fiber coupled , electro-optical modul

• the printed circuit board (generally FR4) that is used as substrate material comprises 100 to 300 receiver units depending on the necessary area for the electronic components,

• the microstructured submount that is soldered to the printed circuit board,

• the electro-optical semiconductor die (laser diode, LED, VCSEL, PIN-detector, ...), that fits exactly to the opening in the submount,

• the coupling element that is made either from plastic or metal depending on the EMI-requirements of the modul,

• the electronic signal processing unit that is assembled by SMD on the substrate backside. The picture above shows a transimpedance amplifier of a fiber optic receiver. The corresponding transmitter requires a driver circuit for the tranmitter diode.

This fabrication process allows to realize customer specific solutions even at rather low volumes (typically down to 1000 units). The initial costs generally cover the PCB costs only. If a new submount is required a new deep drawing tool is necessary for the submount fabrication.