Kyocera develops tiny crystal unit for smartphones, wearables

April 10, 2017

Kyocera announced that it has developed what it calls the world’s smallest crystal unit for smartphones, wearables, and other electronic devices. The new CX1008 quartz crystal unit measures just 1.0 x 0.8 mm yet delivers the same electrical characteristics as Kyocera’s conventional CX1210 model (measuring 1.2 x 1.0 mm), enabling it to be adopted without circuit-board revision. Samples are available now with mass production slated for early 2018.

Crystal units are used to generate highly stable reference signals in digital circuits, based on the unique material characteristic of quartz to oscillate at a precise frequency when a specific voltage is applied. The trend toward smaller, more functional smartphones and wearable devices requires smaller, better-performing crystal units. Traditionally, however, it was believed that miniaturizing crystal units beyond a certain point would compromise their performance, since electrical characteristics (such as equivalent series resistance) degraded as the device became smaller. However, Kyocera said it has succeeded in downsizing the crystal unit while maintaining its electrical characteristics. This has been accomplished through crystal element design technology developed exclusively by Kyocera, along with a process that Kyocera developed jointly with Associate Professor Kazuya Yamamura of Osaka University.

Based on this technology, Kyocera will accelerate the development of new low-frequency, high-frequency, and high-precision oscillators for such applications as automotive electronics, advanced driver assistance system (ADAS) technologies, IoT devices, wireless network base stations, and 5G mobile communications.

Downsizing from 1.2 x 1.0 mm to 1.0 x 0.8 mm would ordinarily increase equivalent series resistance by approximately 30%, requiring circuit-board revision, the company said. However, by optimizing the design using its own piezoelectric analysis technology, Kyocera has downsized this device to 1.0 x 0.8 mm while maintaining the electrical characteristics of the conventional CX1210 crystal unit. This allows the CX1008 to be incorporated into existing circuit designs without revision.

With conventional processes and technologies, a crystal unit exhibits higher levels of variation in key electrical characteristics when produced in smaller dimensions. However, Kyocera has avoided this by applying ultra-high-precision processing, using plasma chemical vaporization machining (CVM) technology developed with Yamamura. This method, using plasma-generated neutral radicals and a chemical reaction at the surface of an object, enables to control a quartz crystal with highly precise surface conditions and thickness. Further, Kyocera’s proprietary semiconductor processing technology ensures accurate external dimensions and minimal variation in equivalent series resistance, for optimal performance at reduced size.

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