Flip chip equipment for high end electro-optical modules

Abstract

Accurate assembly of high-end optoelectronic modules has proven to be one of the most challenging alignment problems faced by assembly engineers today. Silicon optical platform applications, where a laser diode is aligned to a single mode fiber or an optical waveguide, then soldered to a substrate, require post-bonding alignments better than 1 /spl mu/m for optimum device performance. Several methods have been investigated to meet such stringent alignment requirements, ranging from active alignment of a powered device to various forms of passive self-aligned soldering methods employing one or more mechanical stops. Though these methods have demonstrated some good results, the active alignment method incurs substantial cost of assembly time, while some self-aligning methods carry the disadvantage of requiring additional process steps during chip and substrate fabrication, as well as generating more sporadic alignment results under typical manufacturing variations. A fresh approach to this alignment problem is proposed, where the mechanical alignment and placement burdens are borne by the robotic placement machine. Differing substantially from pick and place machines available on the market today, this new flip chip bonder has been specifically aimed at the special requirements of the optoelectronic module market. The design and application of this bonder to this assembly process is reviewed, with special notice given to thermal and optical requirements. Results from several such applications are also given.