Compact crystal unit designed for smartphones

Samples will be available in May 2017 with mass production slated for early 2018. Crystal units are used to generate highly stable reference signals in digital circuits, based on the 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 miniaturising 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 has succeeded in downsizing the crystal unit while maintaining its electrical characteristics — with its current CX1210 (1.2x1.0mm) device, and now, by commercialising the ultra-small CX1008 (1.0x0.8mm) crystal unit. 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.

Product features

1. What the company claims to be the world’s smallest crystal unit with electrical characteristics of the existing CX1210
   Downsizing from 1.2x1.0mm to 1.0x0.8mm would ordinarily increase equivalent series resistance (CI value) by approximately 30%, requiring circuit board revision. However, by optimising the design using its own piezoelectric analysis technology, Kyocera has downsized this device to 1.0x0.8mm while maintaining the electrical characteristics of the conventional CX1210 crystal unit. This allows the CX1008 to be incorporated into existing circuit designs without revision.
2. Manufacturing technology
   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 (plasma 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.