Assembly Solutions. OmniCure. Assembly of VCSELs. Challenge. Solution. Benefit. Repeatable assembly of the VCSEL module to maximize yields.

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1 OmniCure Assembly of VCSELs Assembly Solutions Challenge Repeatable assembly of the VCSEL module to maximize yields. Solution The OmniCure S2000 UV Spot Curing System with Closed-Loop Feedback technology and a three leg High Power Fiber Light Guide along with a light curable adhesive. Benefit A repeatable curing process which will increase product yields and reduce manufacturing costs. Application Note: OMNICURE VC009/09 April 24, 2009

2 A VCSEL (pronounced vixel), stands for Vertical-Cavity Surface-Emitting Laser. VCSELs are laser diodes which emit laser light in a direction perpendicular to the wafer, as opposed to an edge, as found with standard semi-conductor lasers such as Fabry-Perot (FP) and Distributed Feedback (DFB) lasers. Advantages of VCSELs VCSELs have several advantages over edge-emitting lasers. They are more efficient in converting electrical inputs into optical signals. VCSELs can be tested at several stages throughout the production process to check for material quality and processing issues, while edgeemitters cannot be tested until the end of the process. VCSELs allow for smaller sized optical engines, leading the way for higher levels of functional integration at lower overall costs. Finally, it is possible to combine a VCSEL wafer with an array of optical elements (e.g. collimation lenses) and then dice this composite wafer instead of mounting the optical elements individually for every VCSEL. This allows for less expensive mass production of laser products. VCSEL Markets The worldwide consumption value of VCSEL-based transceivers reached $376 million in 2007; and forecasted to increase at a 24.5 percent average annual growth rate to $1.1 billion in The increased production of VCSEL transceivers is fueling development of 10 gigabit VCSELs, multi-wavelength CWDM VCSEL transceivers, long wavelength single-mode VCSELs and opening new Figure 1 :: VCSEL Modules For the telecommunications industry, the VCSEL s uniform, single-mode beam profile is desirable for coupling into optical fibers. They are the light source of choice for short distance fiber-optical links. Their excellent modulation properties, high reliability and single emission geometry has enabled VCSELs to dominate this market and replace conventional edge-emitting lasers. opportunities for these standards-based applications. Use of VCSEL transceivers in Military/Aerospace applications also continues to show strong growth. 1. Press release Vertical Cavity Surface Emitting Laser (VCSEL) Transceiver Global Market Forecast & Analysis , August Source ElectroniCast. Application Note: OMNICURE VC009/09 April 24, 2009 Page 2

3 After the VCSEL die is fabricated, it is placed inside protective packaging. The VCSEL is placed inside a TO-type can which acts to protect the VCSEL from the environment. The entire can is then placed in a plastic or metallic housing. Typically, the housing contains a lens that collimates light. To ensure that an optimal signal is emitted, the component is actively aligned and bonded into position using a UV curable adhesive. Figure 2 :: Laser Mouse The VCSEL s low cost and high reliability make it the natural choice for optical communications applications. However, it has also become increasingly attractive to other markets. An application area for VCSELs which has acquired a large market volume, is that of optical computer mice. A laser mouse with a VCSEL as light source can have a high tracking precision, combined with a long battery lifetime, as VCSELs use 60-70% less power than LEDs. Single-mode VCSELs have also been used for several years in industrial oxygen measurement sensors. Such devices are built as MEMS VCSELs, having a separate output coupling mirror the position of which can be tuned via thermal expansion, electrostatic forces, or a piezoelectric element. The advantages over existing solutions are the fast response times, high sensitivity, high reliability and insensitivity to other gases. The OmniCure S2000 UV/Visible Curing System along with a multi-legged High Power Fiber Light Guide is ideal for this application. Once the component has been properly aligned, it is important to secure it in place quickly before it moves out of alignment. The 200W lamp found in the OmniCure S2000 System will cure most UV curable epoxies in seconds. The resulting bond will be strong and environmentally resistant to insure years of reliable service from the optical component. It is important the epoxy receives a uniform distribution of UV light, in a controlled manner, in order to preserve precision alignments. If the adhesive is not cured in a controlled manner, it will shrink at different rates and to different degrees. The resulting differential shrinkage shifts the VCSEL, causing misalignment, resulting in the device being scrapped. A three or four leg High Power Fiber Light Guide is recommended for this application to provide an even distribution of UV energy to the adhesive. Assembly Process UV curing technology plays a key role in achieving higher yields in VCSEL production. The assembly of VCSEL modules is ideally suited for a UV curable process with the ability to cure specially formulated optical epoxies rapidly, on-demand. UV curable epoxies can be specially formulated to minimize shrinkage, which is important in maintaining the proper alignment of the parts during the curing process. UV curable adhesives will not begin curing until they receive a sufficient dose of UV energy. This allows for active alignment of the components after the adhesive has been dispensed and instant curing once the alignment has been optimized. Figure 3 :: Lumen Dynamics Closed-Loop Feedback The OmniCure S2000 provides adjustment of the UV irradiance in 1% increments allowing for the precise selection of the irradiance level required for curing the adhesive in a controlled manner. Once the optimum irradiance level is selected, the proprietary Closed-Loop Feedback control maintains that level for every cure, insuring a repeatable curing process. Application Note: OMNICURE VC009/09 April 24, 2009 Page 3

4 Proprietary technology within the High Power Fiber Light Guide provides an equal distribution of energy down each leg, arranged radially symmetrical around the device. This provides even curing of the adhesive to preserve the optimum alignment of the VCSEL. Following the alignment procedure, the entire housing is sealed using a UV curable material. At this point, the packaged VCSEL may also be incorporated into other devices for use in other markets. Manufacturers of VCSEL modules will benefit from using Lumen Dynamics OmniCure S2000 UV System with a multi-leg High Power Fiber Light Guide to insure that each VCSEL module receives the precise and repeatable dosage of UV light to insure a quick, dependable and optimized cure. This provides a repeatable assembly process to maximize yields and reduce costs. LUMEN DYNAMICS UV CURING TECHNOLOGY PRECISE AND REPEATABLE The OmniCure S2000 UV System cures UV epoxies in seconds. Since UV adhesives will cure on-demand, the VCSEL can be precisely aligned and then instantly cured in place to insure maximum output. The Closed-Loop Feedback technology found in the OmniCure S2000 System continuously monitors light output at the source, to maintain consistent, repeatable irradiance levels, for controlled cures. Lumen Dynamics proprietary multi-leg High Power Fiber Light Guides provide an equal distribution of energy down each leg to insure uniform curing of the adhesive. Even application of UV light ensures alignment is maintained during the curing process. Application Note: OMNICURE VC009/09 April 24, 2009 Page 4

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