In a room filled with various noises, a single command can instantly "wake up" a "sleeping" smart speaker and prompt it to accept the instruction.
"The emergence of MEMS acoustic sensors has transformed speakers from simple music players into intelligent terminals that can interact with people," said Li Gang, founder and president of Minxin Technology. He explained that MEMS sensors utilize semiconductor manufacturing technology to create microelectromechanical systems on silicon wafers that can collect external signals. With their miniaturization, low power consumption, and high reliability, they are widely used in consumer electronics, automotive electronics, medical fields, and other areas.
In the product showroom of Minxin Technology, which is filled with patent certificates, the reporter saw that the MEMS microphone sensor suitable for wireless Bluetooth headsets is only the size of a sesame seed.
"Our cumulative shipments of MEMS sensor chips have reached 1 billion units," said Li Gang. As one of the earliest MEMS companies in China, Minxin Technology has completed the basic research and core technology accumulation of MEMS product chip design, wafer manufacturing, and packaging and testing through 15 years of continuous R&D investment, and has achieved independent control over the entire production process of MEMS sensors.
Expanding into niche markets
MEMS acoustic sensors were invented in the early 20th century, and Li Gang, who was studying MEMS technology at Peking University at the time, became very interested in them. In 2007, Li Gang led his startup team to develop a MEMS sensor project that was selected as one of the first batch of leading science and technology talents in Suzhou Industrial Park. In the same year, he began preparations to establish Minxin Company.
Li Gang said that at that time, smartphones were emerging, and people's requirements for mobile phone functions gradually increased. In addition to clear calls, they also needed to be able to record audio and video. Traditional microphones could no longer meet user needs, and MEMS sensors became the "new favorite" of the market. Minxin Technology keenly perceived this market prospect and decided to develop the product.
However, MEMS Sensors' journey to success was not smooth. "When we were looking for product development platforms and industrial supply chains with our design ideas, we were repeatedly turned away," said Li Gang. Because MEMS sensors are designed and built in three-dimensional space, the production volume is small and the process is special, so at that time, domestic comprehensive semiconductor companies were unwilling to invest in production.
While promoting its R&D concepts to companies in the industry, Minxin Semiconductor also relied on chip design to sustain itself. In 2008, Minxin Semiconductor's R&D team received assistance from the Suzhou Institute of Nano-Tech and Nano-Bionics of the Chinese Academy of Sciences, and produced its first batch of MEMS acoustic sensor chips on its R&D platform.
Li Gang frankly admitted that the gap between laboratory samples and mass-produced industrial products is not only in quantity, but also in the quality and stable performance of the products.
"Our initial product yield rate was only 30%, and we urgently needed to make process corrections through mass production," Li Gang said. At that time, the country included new electronic components in the high-tech industry development project and provided strong support in terms of policy and funding, which led some domestic semiconductor manufacturers to turn their attention to the production of MEMS sensors.
Subsequently, China Resources Shanghua Technology Co., Ltd. invested in and built a MEMS sensor production line in cooperation with Minxin Semiconductor. "Both companies assembled elite teams, and the R&D personnel spent almost every day on the production line, reviewing test results, correcting processes and parameters, and overcoming difficulties with an indomitable spirit," said Sun Kai, R&D Director of Minxin Semiconductor. In 2012, the company's first MEMS acoustic sensor using its self-developed chip achieved mass production, and due to its superior quality, it quickly gained a foothold in the market.
Currently, MEMSensing has become a supplier of MEMS acoustic sensors for many well-known brands. Its products are used in consumer electronics such as smartphones, tablets, wearable devices and smart homes, and are continuously expanding into fields such as automobiles and medical devices.
Increase R&D investment
Stepping into the acoustic laboratory of Minxin Technology, Sun Kai and his R&D team members are conducting noise tests on high signal-to-noise ratio products using an acoustic analyzer, with the simulated mouth in front of them.
"Look, the signal-to-noise ratio of our sensor has reached 70dB, and the AOP (maximum sound pressure level) has reached 135. It's at an industry-leading level," Sun Kai said excitedly, looking at the values displayed on the acoustic analyzer.
"Signal-to-noise ratio (SNR) refers to the ratio of signal to noise. The higher the SNR, the less noise mixed in with the signal, and the better the sound quality. Sound pressure level (SPL) refers to the highest sound level that a microphone can process before distortion. The higher the SPL, the higher the sound it can process," said Sun Kai. He added that in order to achieve functions such as voice control and sound-based localization at greater distances while ensuring clear sound quality, MEMS acoustic sensors must improve the SNR and maximum recording SPL.
To accelerate R&D and product iteration, Minxin Technology has established multiple R&D teams, conducting continuous brainstorming sessions and tens of thousands of experiments for each product, constantly striving to reach the pinnacle of the industry. Li Gang told reporters that the company has customized and developed more than 80 types of high-frequency, wide-bandwidth, and miniaturized special MEMS acoustic sensors in recent years, meeting various market demands.
Minxin Technology's large product output stems from its relentless investment in research and development. The company's R&D investment was RMB 35.6704 million in 2019, RMB 42.0434 million in 2020, and RMB 75.6186 million in 2021; R&D personnel account for more than 33% of the company's total employees; and R&D expenditure accounts for more than 21% of operating revenue.
For the past 15 years since its establishment, MEMSensing has been committed to innovation and R&D. It now has a multi-category product line with independent R&D and proprietary intellectual property rights, and has gradually grown into one of the few domestic companies that has mastered the design and manufacturing process of multiple categories of MEMS sensors.
"In 2021, the number of invention and utility model patents held by Minxin Technology increased by 150% and 140% respectively compared to 2020, and the number of R&D personnel increased by 40% year-on-year; the number of invention patents granted in the first half of 2022 was 1.4 times that of the whole of 2021." In Li Gang's view, for a company to maintain its vitality, it cannot go far by simply imitating others. It must continuously break through itself and surpass its competitors through R&D innovation in order to win the future.
Strengthen self-control
The manufacturing of a MEMS sensor involves core stages such as chip design, wafer foundry manufacturing, packaging, and testing. "If a startup relies entirely on the external supply chain, it's easy to start but difficult to scale up, and it's hard to leverage cost and scale advantages. It will also lose its core competitiveness and inevitably fall into the predicament of 'homogeneous' competition," said Li Gang. He explained that because the manufacturing process of MEMS sensor chips is highly customized, the process must be developed on demand, making the manufacturing, packaging, and testing stages particularly important.
Li Gang vividly remembers a packaging parameter error incident from several years ago. On an outsourced packaging and testing production line, a parameter error caused the microphone already installed in a mobile phone to malfunction. "Acoustic sensors are different from other components; if they fail, the phone becomes unusable. If the microphone malfunctioned, we would have to compensate for the value of the phone, which would be unbearable for a startup. Products need to be well-designed, but even more importantly, they need to be well-manufactured, well-packaged, and well-tested," Li Gang said.
Fortunately, this batch of products did not experience widespread malfunctions. However, this served as a wake-up call for the company, making it realize that the supply chain must be self-reliant and controllable.
In 2019, MEMSensing invested in and built a wholly-owned subsidiary focusing on MEMS packaging. "Currently, our first-phase packaging and testing plant is already in operation, with a monthly MEMS sensor packaging capacity of 40 million units. In the first half of next year, the second-phase plant will also be put into operation, and the monthly packaging capacity is expected to increase to 100 million units," said Li Gang.
Today, MEMSensing has successfully joined the ranks of leading companies in China's MEMS industry, with its products used in a variety of fields, including consumer electronics, medical devices, industrial control, and automotive electronics. "Over the years, the company has survived fierce market competition by focusing on low-to-mid-end applications. Currently, the company is striving to enter the supply chain systems of major international consumer electronics brands," said Li Gang. He added that MEMSensing is rapidly making breakthroughs in R&D and innovation, and is also continuously improving and addressing its weaknesses in building a complete industry chain to ensure adequate supply and leverage its supply chain advantages.
