Microphone units

With a value of $7.2 million in 2008, the MEMS market is forecast to grow to $10.6 million in 2011, according to IEK. This growth is attributed to the robust market for portable consumer electronics, which includes mobile phones, digital cameras, laptops, personal navigation devices and Bluetooth headsets.

US- and UK-based industry pioneers Knowles Acoustics and Wolfson Microelectronics are gaining foothold in the Greater China market and have set up satellite offices in the region. Both companies are ready to launch their latest solutions, offering second-tier developers and suppliers the tools to quickly adapt to sophisticated market demands.

ASP to fall once mass production begins

Silicone MEMS microphones are more expensive to produce than conventional electret condenser microphones (ECMs) at present. The average selling price (ASP) of a silicone microphone is $1.65, which is up to three times higher than that of ECMs. Silicone microphone prices, however, are forecast to gradually decline to about 15 cents by 2010, dropping by 70 percent from 2006 quotes.

This drop in prices is expected to happen when the silicone microphone market opens up and mass production goes full throttle.

Industry sources also noted that MEMS devices are relatively cheaper to produce since these employ batch fabrication techniques. MEMS microphones come in smaller profiles with mounting options that eliminate off-line subassembly production costs. Customized designs can be easily applied on tape-and-reel and run through standard automatic pick-and-place equipment during in-line surface mounting.

MEMS silicone microphones deliver the same acoustic performance as that of ECMs but come in thinner and more compact profiles. Silicone microphones with MEMS also withstand higher temperatures than ECMs during surface mounting in consumer electronic products.

Pioneers offer tech assistance, new solutions

Knowles and Wolfson have established satellite sales offices and R&D facilities in Taiwan to service the growing local acoustic industry. Knowles, for instance, has set up a research center to assist local developers as well as accelerate the technical development of the region’s nascent MEMS microphone line.

With more than 50 years’ experience in the acoustic industry, Knowles is the world’s first maker to offer surface-mount MEMS microphones. It introduced its SiSonic series in 2002, which is currently on its fourth generation of development. The company now accounts for nearly 75 percent of the world’s MEMS microphone supply.

Wolfson, on the other hand, is relatively new to the silicone microphone market. It offers the WM7110 and WM7120 silicone microphones, which are built on the company’s proprietary CMOS and MEMS membrane platform. The 4.72x3.76x1.25mm WM7110 and the 3.76x2.95x1.10mm WM7120 typically consume 160µA and are suitable for use in portable electronic devices.

Wolfson also released models WM7110E and WM7120E, which feature a sensitivity tolerance of ±1dB. Both devices offer an improved 62dB S/N ratio (A-weighted) performance by reducing the noise floor in the microphone. These feature 0.5 percent maximum THD at 100dB SPL.