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Silicone or not ?

In-Depth: Ulysse Nardin And SIGATEC: Project Code Name "Si"

For the first time in 17 years of production, it’s now possible to enter the clean room at SIGATEC in Sion, Switzerland. Join us as we witness the secretive manufacture of silicium parts first-hand.

By Vincent Daveau

Silicium, in the form of Silica sand, is one of the most abundant chemical elements on earth. However, it does not exist naturally in its metallic state, only in dioxide or silicate form. A substance known and used in the field of electronics for decades, it was first micrometrically sized for use in movement sensors of automotive air bags in the 1980s, which subsequently led to significant advances in the technology.

In the beginning there was sand

DRIE, or Deep Reactive Ion Etching by photolithography permits the machining of pure silicium with micron-level tolerances. The very first watchmaking experiments with this pure metalloid were conducted by the R&D office of Ulysse Nardin and showcased in the Freak watch in 2001. It is also interesting to note that the group of watchmakers comprising Patek Philippe, Rolex and the Swatch Group also began working in collaboration very early on with the Federal Institute of Technology, Lausanne (EPF), the Institute of Microtechnology (IMT) at the University of Neuchâtel, the Swiss Centre for Electronics and Microtechnology (CSEM) and COMLAB.

These collaborations led to the invention of a reliable process for the manufacture of balance springs and other useful components of mechanical watches. Their work gave rise to a patent application for the balance spring that focused specifically on treating it to surface oxidization that render it thermally stable.

Mastering the latest technologies

A material very much in vogue among watchmakers for its hardness, light weight, purity and insensitivity to magnetic radiation, silicium has been especially useful in the manufacture of electronic components for decades. However, companies such as MIMOTEC (a 50/50 stakeholder together with Ulysse Nardin in the joint venture SIGATEC) quickly understood its attraction for watchmakers up against the pressure on deliveries of metallic balance-springs and other fine components of mechanical watchmaking escapements. MIMOTEC is totally owned by the Acrotec Group

They soon realised the need for developing a technology that might permit the standardised production of sufficient quantities of ultra-precise silicium components. This observation led, in 2006, to the founding of SIGATEC, a company now specialised in the manufacture of silicium components for the watchmaking industry and certain parts for watchmaking brands authorised to use the patent submitted by the CSEM. According to Marc-André Glassey, CEO of SIGATEC, the company is now able to make incredibly reliable balance-springs, but it will have to wait until 2020 and the expiry of the CSEM patent before it can start supplying its version to all brands seeking silicium components which guarantee optimum precision.

Into the heart of the SIGATEC matrix

Thanks to SIGATEC 's consummate in-house mastery of the technologies in place at its Sion-based workshops, it is now able to supply Ulysse Nardin and other industrial entities with a myriad of silicium components aimed at watchmaking. The company produces a huge number of elements, after all it went to great lengths to highlight the advantages of a material it was the first to use itself for the making of pallet wheels, pallets, balances, etc..

Indeed, we hear much about the components themselves, but we rarely hear anything about how they are manufactured. To attempt to answer this question, the watch brand sporting the famous anchor logo decided to invite specialized journalists into its clean room for the first time ever.

Naturally, anyone wishing to gain access inside must wear special gear as not one speck of dust may be allowed to compromise production quality. Once visitors are through the pressurised air chamber, they are required to don a brand new, vacuum-packed suit. Caution is nevertheless advised as no part of the suit is allowed to touch the ground. Once through, they must put on a mask, special boots and a hood to cover the head, then slip on gloves without touching any outside surfaces. After this procedure is completed, the adhesive floor catches any last particles of dust that might have escaped the vigilance of the cleanliness experts. The first thing that strikes the visitor on the other side is the yellowish hue of the environment. The anti-UV light is designed to protect the silicium wafers, since UV rays will be used in the destruction of the masking films covering the components.

The manufacturing procedure - the key phases

The process starts with a wafer, a silicium disc calibrated to thickness and assembled on a protective substrate. This material, sliced from a silicon crystal ingot, is delivered ready for use by one of the few factories in the world able to supply the material in its purest quality and with the expected finishes. Once the disc is removed from its protective box, it is placed in a kind of centrifuge to be coated in a reactive epoxy film. It is only the parts of the film not exposed to the UV rays that will remain.

Once the solvent has evaporated, the wafer has an iridescent colour and is transferred to the next stage. The optical glass mask protecting the positive image of the future components marked out in chrome is adhered to the wafer, then exposed to an ionized plasma flow designed to destroy the epoxy film not covered by the mask. After rinsing in a "piranha" bath (a specially formulated acid bath), the oxidized part of the wafer disappears leaving the shapes of the future components.

The whole is then placed in a very special machine costing a hefty 1 Million CHF equipped with a tank complete with air vacuum in which the wafer is a bombarded by ionized plasma, which makes etches in the material a few micrometers deep. Once this stage has been completed using the plasma process, the machine injects a gas containing a Teflon-based polymer, which isotropically deposits itself in the cavities thus formed. The goal is to protect the existing vertical sides against any further destruction by exposure. The procedure is then repeated until the required depth is obtained. Once the successive operations are completed, all that remains is for the operators to remove the substrate allowing the handling of the disc. The wafer, which corresponds in thickness to that of the future component, is then placed in an oven heated to a temperature of 1000 degrees Celsius in order to be subjected to surface oxidization, which will ensure the components treated (mainly the balance springs) are thermally stable. The other components are coated with a layer of DiamondSyl® in order to guarantee extreme hardness and tribological properties.

Once the disc is finished, it is inspected visually by an operator and each compliant component is separated from the wafer, to which it is attached by very fine threads. The points of attachment have been carefully designed to ensure that, once the part has been removed, there is no impact upon the future functioning of a component made using contemporary processes.

The elements are then gathered together and packaged up, before heading off for the different workshops of the Ulysse Nardin manufacture. There, they will be assembled traditionally and fitted into the watch for which they were made, thereby ensuring that the duly-equipped watchmaking instruments offer a degree of performance and accuracy superior to that provided by the same components made in classic watchmaking materials.

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