Page 21

EETE JULAUG 2014

Fig. 2: Bonding wafers and use of TSVs produces a monolithic CMOS sensor just 600-micron thick. Source: mCube achieve 8-bit resolution, Lee said. Grain of sand With sensors in 3mm and 2mm packages mCube is already down at the same sort of size as a grain of sand – coarse sand comes in at 1mm to 2mm. But what if, with the monolithic construction mCube could forego the plastic packaging and directly bond its hermetically sealed die to the PCB? “The z-height goes even lower,” said Lee. “We have to look at structural integrity issues and how the cavity inside the sensor performs. But we have alpha customers and it’s very exciting,” said Lee. Lee also has an mCube take on the sensor fusion, sensor hub debate. Does it mean that mCube will be adding microcontroller circuitry for software programmability within the company’s tiny combination sensors? Lee said there are three main approaches: 1) running the sensor fusion software on the application processor, 2) having a separate sensor hub IC, such as Apple’s M7; 3) and putting an MCU inside the MEMS package. The decision is usually based on the lowest power for an always-on solution so that motion of the equipment can be used to wake up the circuitry. “Most of our customers don’t want us to do it in the third option. But that doesn’t mean they don’t want us to write the software. They want us to provide a library of algorithms for accurate pedometer and so on.” As an extension of this, mCube has written a couple of games that can show of the ability of the company’s iGyro component. For now Lee is determined that mCube should follow the business model of its investor and partner MediaTek. “China is our first focus. We’re not concentrating on any other customers but those. But our reputation for smallest size does mean we are starting to get cold calls for the wearables market,” said Lee. ISO9001:2008 hit or miss. And when you are kicked out it is very disruptive to the company,” he said pointing at companies that have been more or less destroyed by the loss of an Apple design win. The Chinese market is faster moving and much finer-grained with scores of “white-box” companies designing and making equipment for brands in China, said Lee. “There are a slew of ODMs original device manufacturers supplying the brands in China. Part is brand supply then there is also a domestic no-brand market. And then there are also emerging markets in India, Africa, Indonesia and elsewhere. There is a market of about 600 million phones shipped annually served by 100 ODMs in China that go into local and international markets,” said Lee. “But you have to behave like a Chinese supplier. It’s the wild, wild East,” he said. But it offers a number of things that are much better for a startup than an Apple or Samsung design win. “It’s fast time to market, fast time to money and fast time to feedback,” Lee said. “And now there is wearables. mCube has the world’s smallest accelerometer – that’s confirmed by Yole Developpement,” said Lee. “So our timing is very good.” Lee explained that while the motion of gaming and phone handsets and tablet computers is definite and relatively easy to detect, wearables are throwing up the need to detect subtle movements. “Trying to detect very slight movements in wearables is pushing companies to deploy three or four sensors as far apart as possible on the PCB, which means the sensors must be small. So it’s not a 1:1 attach rate but multiple separate devices.” Fabless with TSMC But mCube is fabless and so the manufacturing of its MEMS sensors comes courtesy of foundry supplier Taiwan Semiconductor Manufacturing Co. Ltd. What’s to stop TSMC offering the process to others creating competitors? “We co-developed the process with TSMC,” said Lee. mCube has also filed more than 100 patent applications. Lee does not rule out the possibility that other companies might use manufacturing services from TSMC of a similar nature but added: “It’s true we are the designers but in MEMS design and manufacturing are highly integrated.” Lee points out that one of their key patents covers how to accurately control the depth of etching for a TSV so that there is a connection but no damage on the primary wafer that carries the electronic circuitry. Without that technique the approach is closed off to potential rivals. With it mCube is able to create 14-bit resolution sensors when other companies struggle to such as a MediaTek octocore; www.norsun.com.tw For more information please contact gwenlin@norsun.com.tw directly www.electronics-eetimes.com Electronic Engineering Times Europe July/August 2014 21


EETE JULAUG 2014
To see the actual publication please follow the link above