Silicon in the movement

Silicon parts are etched from wafers of monocrystalline silicon by deep reactive ion etching, the DRIE process of microelectronics, and can be cut to almost any flat shape.^2, 5

Patek Philippe lists the properties that drew watchmakers: silicon is hard, about a third the density of steel, non-magnetic and resistant to corrosion, and flexible in thin structures. WorldTempus adds that it needs almost no lubrication but breaks if stressed in the wrong direction.^2, 5

Its use is in the escapement and the regulating organ: the balance spring, the lever and the escape wheel, where weight, magnetism, temperature and friction matter most, as WorldTempus describes.²

Ulysse Nardin’s Freak of 2001 had no dial and no crown, and its Dual Direct escapement gave impulse from two escape wheels. Monochrome reports that aluminium wheels worked but wore too fast, so the wheels were etched from silicon.¹

Monochrome credits the project to the company’s owner Rolf Schnyder, the watchmaker and historian Ludwig Oechslin and the designer Carole Forestier, and says Ulysse Nardin set up Sigatec with Mimotec in 2006 to make parts by LIGA and DRIE. WorldTempus reports that Ulysse Nardin and Sigatec supply silicon parts to other brands.^1, 2

A balance spring of plain silicon would change its stiffness with temperature. CSEM’s European patent, filed on 25 November 2002, covers a spring cut from monocrystalline silicon with an outer layer, such as silicon dioxide, whose thermal coefficient has the opposite sign, so that the two cancel.³

CSEM calls the result Silinvar, the first temperature-compensated silicon balance spring; Patek Philippe uses Silinvar as the name of its own silicon material.^5, 7

A consortium of Patek Philippe, Rolex and the Swatch Group, formed at CSEM, licensed the patent and took silicon balance springs into industrial production, as Europa Star and WorldTempus report; Europa Star says Patek had first worked with the microengineering institute of the University of Neuchâtel.^2, 4

Patek Philippe dates a Silinvar escape wheel to 2005, the Spiromax balance spring to 2006 and the Pulsomax escapement to 2008. Europa Star dates Rolex’s Syloxi spring, of silicon and silicon oxide, to 2014, in the women’s calibre 2236.^4, 5

WorldTempus reports that the Swatch Group fits silicon parts across almost all its brands, and that Breguet was among the early users.²

The core European patent expired on 25 November 2022; Europa Star gives 2023 for Japan.^3, 4

Europa Star reports that a silicon balance spring cost about 100 francs at first and about 20 by 2022, and that makers outside the consortium, such as the Biel brand Horage, prepared springs of their own for when the patent lapsed.⁴

New shapes followed, because silicon is easy to prototype: WorldTempus names Girard-Perregaux’s Constant Escapement of 2008, with a flexible silicon blade, and the Zenith Defy Lab of 2017, developed with CSEM and TAG Heuer, whose one-piece silicon oscillator runs at 15 hertz.²

CSEM says it developed with Vaucher Manufacture Fleurier, in 2014, a new mechanical regulator to replace the Swiss lever escapement that cuts a movement’s energy use by up to six times.⁷