Waveguide and packaging technology for optical backplanes and hybrid electrical-optical circuit boards

Abstract

Due to ever-faster processor clock speeds, there is a rising need for increased bandwidth to transfer large amounts of data, noise-free, within computer and telecommunications systems. A related requirement is the demand for high bit-rate, short-haul links. Here, optical transmission paths are a viable alternative to high-frequency electrical interconnections, whereby layers with integrated waveguides are particularly suitable. The reasons for this include that a higher connection density can be achieved and the power dissipation, as well as interference from electromagnetic radiation, are significantly lower. The article presents general considerations and the results of research conducted by the German BMBF Project NeGIT, into the manufacture of circuit boards with embedded polymer optical waveguides. The electrical-optical boards were fabricated using precise photolithographic processes and standard lamination methods. They possess the thermal stability necessary for manufacturing processes and operational conditions, in terms of both bond strength and the stability of the optical properties. As part of this project, a design of an optical coupling in the daughter card and board backplane interfaces was developed and is presented as the centerpiece of this study.

Design and measurement of stress indicator structures for the characterization of Epoclad negative photoresist

“…However, in the past decade other materials have also been introduced and used for the active or structural parts of MEMS [1][2][3]. The goal is to make cheaper or even new and better MEMS using these new materials.…”

“…Epoclad comes together with Epocore, also a negative epoxy-based resist. To manufacture an optical waveguide, Epocore would be used as the core and Epoclad as the cladding of the waveguide [3]. Epocore, however, has very bad adhesion properties to various substrates such as silicon wafers.…”

Electro-optical circuit boards using thin-glass sheets with integrated optical waveguides

“…The optical connector between the daughter card and the backplane is the result of further development of a solution, developed for a single-layer polymer optical waveguide system [6]. Due to the two-dimensional waveguide assembly in the circuit boards, the present design uses 2 x 12-channel fiber arrays (50 µm GI-fibers) in the daughter-card backplane connector (Board-Backplane-Connector, BBC) ( Figure 12).…”

“…To improve the today used optical backplanes using glass fibers, the trend of electro-optical circuit boards (EOCB) is being set by integrated waveguide layers, manufactured by planar structuring processes, which are embedded into the [6]. A variety of polymer materials are used for these layers [7].…”

Embedding of Optical Interconnections in Flexible Electronics

“…Same accuracy is realised for the laser ablated micro-mirrors which are fabricated afterwards. The 5 μm precision is crucial for the feasibility of a low loss optical connection [11]. As an alternative to thinned-down dies, standard components with 150 μm thickness can be embedded by using a 150 μm thick cladding layer or multiple 50 μm layers.…”