High reliability 2.5 Gbit/s modules using silicon platform technology

Abstract

This article deals with the qualification principles used to assess the reliability of 2.5 GbiUs optical modules developed with the Alcatcl Optronics Planar technology. Detailing the tests chosen to validate several technical options. an early rcliabilih assessnicnt method is discussed and illustrated on two different modules witli regard to qualification results obtained on standard Telcordia tests. lntroduction The Alcatel Optronics planar teclmolo~ refers to the use of silicon platfonns, which brings numerous advantages. Firstly. it allows significant cost reductions tllanks to assembling automation, IMSS production capacity and cheaper raw material. Secondly. it gives the possibility to miniaturize the products Uuougbout the integration of several functions on the sane silicon motherboard (laser diode. monitoring photodiode. ..). Moreover. mastering the teclmologics linked with tlie use of silicon platfomi also opens the way to more coinples hybridization. Optical routing and switching functions can be implemented on silica on silicon platforms, using the active chips soldering process, the fibering and the coupling lens inounting teclmologies already developed for basic silicon motherboard. As esaniples. demonstrations of ultra compact and low cost 8sl wavelength combiner and amplified demus module have been proposed by Alcatel Optronics at ECOC 2002, integrating photodetectors arrays: planar MOEM devices? SOA clups and Arrayed Waveguide Grating (AWG) on hybrid silica on silicon platforms. The research efforts on optical devices using silicon optical bench have been quite intensive during tlie last decade. Most of the papers published along tlus period focused on the silicon platform design and manufacturing techniques, llie laser and/or detector chips aligrunent concerns, the optical coupling tolerances and perfonnances, or the fibering process [1][2][3][4][5]. More recently, since approximately five years, several announcements were made on the realization of either complete emitter or receiver modules, with attractive results in terms of perfonnances, potential cost reduction, and compactness [61[7]. Nevertheless, few papers really insisted on the reliability concerns and generally only focused on some specific results [SI, or described a status on standard qualification tests without further detail on measured parameters and failure criteria [9]. Besides, today's commercial offer is not so wide for components based on silicon assembly technology, suggesting that manufacturing and reliability control of that prodiict is no1 so easy to master. Qualification of building blocks Many technological building blocks were proposed for coinponents based on silicon platform: which may lead to various teclmical options during the product development and transfer to manufacturing. For instance, the choice of the mounting technique of the active chips on the Si submount usually balances between full self-aligrunent process and mnacldne-assisted positioning (vision system with refercnce riducials on submount and/or chips): the solder reflow process inay then differ. possibly impacting the reliability of the chip assembly on the submount (solder bumps composition and geometr?., rcflow atmosphere and thennal profile). The fibering (Fig. 1) or the coupling lens mounting (Fig. 2) on the silicon platfionn also rely on two separate options: eitlier gluing or soldering process; with or without the use of additional fistures for the mechanical robustness improvement of the assembly. Again, the reliability behavior of the final devices will strongly depend on these choices.