In, e.g., the communication and computer related fields, there exists the need for the fusion of electrical and optical technologies. To facilitate the fusion, packaging of optical fibers and associated optoelectronic components must be advanced. The cost of producing optical and optoelectronic modules is typically dominated by the cost of packaging of the devices rather than the cost of the devices. One aspect of device packaging is the bonding of, e.g., devices, components, assemblies or semiconductor chips (collectively "components") to a substrate. A bonding approach which has been used extensively by the electronics industry is the the flip-chip solder bump technique.
Although solder bump bonding is well established in the electronics industry, only recently has this approach been used in conjunction with optical and optoelectronic components. These new uses of solder bump bonding have revealed limitations of the technique which typically are not of concern in the established applications of the technique. For example, optical and optoelectronic bonding involves more demanding alignment tolerances than are customary in electronic bonding. In the latter, alignment in the substrate plane is typically the only concern. Usually, as long as the wettable pads are correctly positioned on the substrate, the components will be correctly positioned. Alignment in the direction normal to the substrate (z-direction) typically has not been a significant concern in electronic packaging. However, when bonding optical and/or optoelectronic components to a substrate, the components frequently not only need to be accurately aligned in the plane of the substrate (x and y directions) but also in the direction normal to the substrate (z-direction). Exemplarily, if the alignment of an optical waveguide with respect to the associated laser radiation source is off by even 1 .mu.m in any direction, the optical coupling efficiency of the combination can be too low to be acceptable.
Solder bonding a component to a substrate such that the positional variation in the direction normal to the substrate is within, e.g., .+-.1 .mu.m is difficult. Thus, a process which can satisfy the stringent alignment requirements, especially in the z-direction, that are encountered in optical and optoelectronic packaging is much needed and could significantly reduce the packaging costs associated with optical and optoelectronic packaging. This application discloses such a process.
USPTO Backgrounds
USPTO Backgrounds