Piezoelectricity: the invisible force that revolutionised precision technology
The article entitled "The Application of Piezoelectricity to Watches," written by Eishi Momosaki and Shigeru Kogure and published in 1982 in the journal Ferroelectrics, presents a detailed analysis of the use of quartz oscillators in wristwatches. The introduction to the article highlights how piezoelectricity, specifically through the use of quartz crystals, transformed the precision and miniaturisation of watches.
The text, always with reference to its time, begins by explaining the rapid adoption of quartz oscillators in watches and clocks, largely owing to their ability to maintain an extremely stable frequency. This is due to the resistance of the quartz crystal to environmental changes, such as temperature and elapsed time. The authors point out that more than 60% of the quartz oscillators manufactured in Japan at the time were destined for the watch and clock industry, which underlines the importance this technology had in the market.
Performance of Quartz Oscillators in Wristwatches
The article describes four main requirements for the performance of quartz oscillators in wristwatches:
Stability of characteristics: Precision is fundamental, requiring the resonant frequency to be as stable as possible, regardless of environmental conditions.
Miniaturisation: The small size of the components is essential for making small, elegant watches.
Low power consumption: Given the limited size of the batteries used in watches, the quartz oscillator must consume little energy.
Low cost: High productivity and low costs are vital to the commercial viability of quartz watches.
Technical Advances and Manufacturing Methods
The authors discuss the technical advances that made the miniaturisation of quartz oscillators possible. The development of packaging technology reduced the volume of the oscillators, and power consumption fell significantly over the years, thanks to improvements in both the integrated circuits and the oscillators.
In addition, the article explores methods of analysis and design, highlighting the use of the Finite Element Method (FEM) to calculate the vibrations of quartz oscillators, which led to improvements in the design and efficiency of the components.
As regards manufacturing, the authors explain the transition from the use of mechanical techniques to make oscillators to the application of photolithographic techniques, which allow oscillators to be mass-produced with high precision at reduced cost. Photolithography, similar to that used in the manufacture of integrated circuits, makes it possible to produce ultra-thin, miniaturised oscillators, already used in high-precision watches.
Future Trends
The article concludes with a discussion of future trends for quartz oscillators, from the perspective of the time, suggesting that the pursuit of precision will continue to drive innovation in the field. The authors mention the growing interest in more advanced resonance modes, such as the thickness-shear mode and the coupling of multiple oscillators, which could result in even more accurate and reliable watches.
The article by Momosaki and Kogure provides a comprehensive view of the impact of piezoelectricity and quartz oscillators on the watch industry. The innovations described in the text not only improved the precision of watches but also made possible the mass production of affordable and elegant watches, shaping the wristwatch market as we know it today. The combination of advances in design, analysis and manufacturing continues to be a field of great interest for the watchmaking industry.
Further information: The application of piezoelectricity to watches
NOTE:
Piezoelectricity is the property that certain materials, such as quartz crystals and ceramics, have of generating an electric charge when subjected to mechanical pressure. This phenomenon occurs because of the crystalline structure of these materials, which, when deformed, causes a displacement of the internal electric charges, resulting in the creation of an electric potential difference. Conversely, applying an electric field to these materials can induce a mechanical deformation, which allows them to be used in a wide range of technological applications, such as sensors and oscillators in watches and other electronic devices.
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