High accuracy machine automated assembly for opto electronics

One of the major alignment challenges faced by assembly engineers today is the accurate assembly of high-end optoelectronic modules. Silicon optical platform applications, where a laser diode is aligned to a single mode fiber or an optical waveguide, require post-bonding alignments better than 1 micron for optimum device performance. Flip Chip technology has proven its ability to cope with such stringent alignment requirements. Several bonding methods have been investigated, 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 passive alignment approach is proposed, where the mechanical alignment, placement and joining burdens are bourne by a flip chip bonder. 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, and is capable of performing in-situ gold-tin eutectic bonding to 1 micron accuracy. The design and application of this bonder to this assembly process is reviewed, with special notice given to optical, thermal and environmental requirements.