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OmniCure Assembly Solutions ®
Assembly of Bluetooth Headsets Challenge Reliable, low-cost, low-heat assembly of Bluetooth headsets.
Solution The OmniCure® S2000 UV Spot Curing System with Closed-Loop Feedback technology and a dual-leg High Power Fiber Light Guide along with a light curable acrylate adhesive.
Benefit A repeatable curing process which will maximize sound quality and reduce manufacturing costs.
Application Note: OMNICURE BLU010/09 September 4, 2009
Light curable adhesives are used in the assembly of acoustical components where a strong and flexible bond is required without heating of sensitive components. Micro speakers used in Bluetooth headsets must be small and rugged while at the same time, they must provide the highest possible acoustical properties. Increasing consumer demands for wireless access to music and other multi-media applications being used on cellular phones and MP3 players is driving demand for improved sound quality. Prices for Bluetooth headsets are currently declining, requiring the assembly process to be as costeffective as possible for the manufacturers to be profitable. This application note provides a brief overview of the benefits of using the OmniCure® S2000 along with a multi-leg High Power Fiber Light Guide in the assembly of Bluetooth headsets. Headset manufacturers can achieve a fast, low-heat and repeatable assembly process to maximize yields and minimize assembly costs.
Market Bluetooth technology has been very successful in specific markets at replacing wired headsets for mobile phones. Today, over 60% of the phones sold in the United States come with built-in Bluetooth.1 The market for Bluetooth headsets is set to almost double from just under 60 million units shipped in 2007 to over 115 million by 2010.2 Figure 1 :: Cell phone with Bluetooth headset Its initial success was to replace the wired headset for hands-free calling in an automotive setting, especially with the addition of laws that prohibit handheld phones while driving. Growth has also been driven by the trend throughout the consumer electronics industry to go from wired to wireless.
1. Article “Handset Laws a Boon for Bluetooth”, June 2008, Source: ABI Research 2. Article “Bluetooth Headset Market. The Good, The Bad and The Ugly”, Oct 2008, Source: MGDP Consulting
Application Note: OMNICURE BLU010/09
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While demand for Bluetooth headsets has continued to grow, an increase in the supply of products has seen a steady decline in the price for headsets and reduced profitability for the manufacturers. New technologies such as Active Noise Cancellation and the improving performance of stereo headsets are expected to re-establish some of the profitability that the market for mono headsets is gradually losing.
UV curable acrylics are widely used in the assembly of Bluetooth headsets to join the voice coil to the diaphragm. The diaphragms for micro speakers are very thin and delicate; most often made of mylar or paper. It is very important in this assembly process to avoid heating the diaphragm which might distort or even break the diaphragm; rendering the part useless.
To create stereo Bluetooth products that seamlessly stream audio and offer superior quality, handset manufacturers must ensure their products are compatible with the Advanced Audio Distribution Profile (A2DP). A2DP describes how stereo-quality audio can be streamed from a Bluetooth-enabled audio source (e.g., MP3 player or mobile phone) to an audio synch (e.g., wireless headset or wireless speakers). In 2007, the sales of music phones reached 575.7 million worldwide and are predicted to reach 886.7 million by 2010.3 At the same time 116 million handsets were equipped with A2DP stereo capabilities in 2007. By 2010 it is expected that 544 million handsets will be ready to deliver a wireless stereo experience.4 Figure 3 :: Micro speaker components
In some processes, large area UV curing systems are used for joining the voice coil to the diaphragm. Large area curing systems are able to cure a number of speaker components quickly, but will often generate too much heat during the curing process, damaging the diaphragm. This is due to a significant amount of infrared (IR) light being produced by the large area UV lamp. The IR light will heat the diaphragm, often causing irreparable damage to the parts. Figure 2 :: Bluetooth Stereo headset In order to deliver the experience successfully, Bluetooth stereo headsets will need to be paired with the mobile devices. The stereo headset market is expected to double from 2008, reaching 14.2 million Bluetooth headset sales in 2010.5
Application UV curing technology is used in the automated production of Bluetooth headsets, where the acoustical components are bonded in 2 to 3 seconds. The adhesives must rapidly join parts of different materials such as plastic and metal and provide a very strong bond, able to withstand harsh conditions such as drop tests from 10 feet as required by wireless headsets.
The OmniCure® S2000 UV Spot Curing System uses a 200W lamp with a proprietary dichroic coating on the lamp reflector to minimize the amount of IR light from the lamp. The OmniCure® S2000 also includes a bandpass filter to only allow specific wavelengths of light through to the parts; virtually eliminating all unwanted IR. There are 5 different bandpass filters available to select only the required wavelengths for even further heat reduction. Another important requirement for the voice coil to the diaphragm bond is that the UV adhesive must remain flexible in order to absorb vibrations. This is essential for ensuring optimum acoustic properties of the micro speakers.
3, 4, 5. Article “Plantronics and Altec Lansing predicts quality audio to drive the next revenue peak”, August 2008, Source: Strategy Analytics
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When curing a UV acrylate it is important to maintain a very repeatable irradiance level. While acrylates provide the benefit of curing very rapidly with UV exposure, it is also possible to over cure them. This could have a detrimental effect on the physical properties of the cured adhesive, such as reducing flexibility, which could result in inferior acoustical properties in the headset. The OmniCure® S2000 UV Spot Curing System prevents these problems by allowing for very precise selection of irradiance levels in 1% increments. Once the optimum irradiance level has been determined, the OmniCure® S2000 includes Closed-Loop Feedback technology to monitor and maintain the irradiance level of the UV curing process. This proprietary technology ensures a repeatable manufacturing process of very high quality speakers.
Manufacturing of Bluetooth headsets poses challenges to assemble heat-sensitive components in an automated process. Adhesive bonds must be strong for reliability, yet must maintain flexibility in order to provide the acoustic properties demanded by consumers. Lumen Dynamics’ OmniCure® technology offers unique benefits over and above standard UV curing, ensuring low heat, repeatable curing for cost effective assembly of specialized electronic components such as Bluetooth headsets for cellular phones.
LUMEN DYNAMICS UV CURING TECHNOLOGY – PRECISE AND REPEATABLE • The OmniCure® S2000 UV system cures UV acrylics in seconds and can easily be integrated into fully automated production processes.
• The OmniCure® S2000 has a choice of 5 different filter options to provide low-heat curing for sensitive components.
• The OmniCure® S2000 lamp includes a dichroic filter to virtually eliminate IR light for a low heat curing process.
• The Closed-Loop Feedback technology found in the OmniCure® S2000 system ensures repeatable irradiance levels, for consistently flexible bonds and optimum acoustic properties.
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www.LDGI-OmniCure.com
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