The optoelectronics assembly roller coaster


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Entering the optoelectronics industry has been an up-and-down affair for many. A few years ago in the late 1990s, assembly equipment suppliers for the semiconductor back-end industry became involved in optoelectronics. This was, in part, the result of automation expertise from the semiconductor industry being sought by the opto industry.

For instance, manufacturers of sophisticated laser diode packages realized they needed to automate package assembly to cope with increased demand. Manual assembly was just too slow and yield was unsatisfactory. Assembly of typical high-end packages required specific accuracies, ranging from sub micron to more than 50 microns; this experience helped suppliers move into this expanding market.

As a result, such opto companies began using semiconductor pick-and-place tools. Companies employing epoxy bonding in their devices could use off-the-shelf equipment while more demanding optical subassemblies required suppliers to add high-temperature eutectic bonding capabilities. This was needed to reflow gold-tin eutectic solder up to 400°C. Therefore, heater stages with fast temperature ramping capability, as well as controlled flow of forming gas during the bonding process and a die scrubbing feature, were needed.

The future of both the suppliers and their customers looked bright: Opto manufacturers boasted three-digit growth rates of laser demand and semiconductor equipment suppliers began calculating the demand for assembly equipment unfolding in this new market.

Customizing for a New Industry

When my employer joined this market in 1998, we were challenged to customize our equipment under great time pressure. Customers were changing the specifications of their devices while we were optimizing the automation of the assemblies.

We soon recognized that meeting the accuracy requirements claimed by opto assemblers was challenging. Taking highly accurate semiconductor equipment and putting kilowatts of heating power on it compromised its accuracy. Also, because the opto industry was immersed in manual assembly, many didn't have a clear understanding of the accuracy required to obtain high yields. Tolerances of manually assembled devices don't necessarily follow a bell curve and they consist of many components that all contribute to a certain degree of misalignment and performance. Thus, it can be difficult for opto assemblers to identify the critical tolerances.

The simplest solution, then, is to over-specify the accuracy of the automated assembly steps, allowing higher tolerances for misalignment for the manual steps. The equipment supplier, as a consequence, tends to publish more “theoretical” accuracy specifications. In this hectic phase of the market, we completed several customer specific solutions and designed our own standard eutectic-bonding offering.

Automation and Accuracy

SEMICON West 2001 illustrated the impact that the optoelectronics boom has had on die bonder manufacturers. Many manufacturers displayed tools equipped with automated eutectic bonding capability and improved accuracy to comply with the industry's common 5-mm requirement. Clearly, standardization of designs and processes in the opto industry is still at a low level compared to those in the semiconductor industry. This is not only because the industry is relatively young, but also because high-end opto packages are multi-chip packages.

The variety of assembly steps, however, has created relatively small niches for automation equipment manufacturers. Under these circumstances, we will probably see attempts to integrate multiple assembly operations on one machine and to manufacture components in a single pass mode. Also, some specialized equipment suppliers are actively looking for partnerships with other suppliers. Too many conditions of the industry continue to change to allow one company to dominate the market.

Overcapacity Gives Us Pause

Early in 2001, someone pulled the plug and all the equipment manufacturers had to throttle down. Now we are aware that the short-term forecasts for this industry were misjudged and the installed base of assembly equipment represents significant overcapacity. However, this is a temporary hiccup on the way back to a very high demand for optoelectronics. The need for increased data transmission rates will push the network suppliers to invest in the “last mile.” Needless to say, activating fiber optic networks in metropolitan areas will be expensive. And as soon as end-user demand pushes the opto roller coaster up again, the obstacles to invest will decrease and progress will surge ahead.

André Nipkow, vice president and head of ESEC's Business Unit Micron, can be contacted at Hinterbergstrasse 28, CH-6330 Cham, Switzerland; Tel: 41-41-749-5111; Fax: 41-41-749-5114; E-mail: [email protected].


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