Mimotec Micro-parts for great ideas
At the end of the 90s, Dr Hubert Lorenz was pursuing his doctorate degree at the Swiss Federal Institute of technology of Lausanne (EPF) where he was elaborating and perfecting the UV-LIGA manufacturing process. Inspired by the procedures used in the field of electronic circuits, he went on to revolutionise the process by structuring photo-sensitive resin (SU-8) up to 1 mm thickness.
Dr Lorenz’s work caught the attention of an industrialist in the canton of Valais,who gave him the opportunity to put his thesis results into practice via the manufacture of mould inserts for plastic-injected watchmaking components. Following this, Dr Lorenz founded Mimotec SA and set up shop on the premises of his first clientAnd the rise to success continued
The efficiency of this technology was rapidly proven and orders grew exponentially. With diversification in mind, Mimotec launched the manufacture of hard nickel components (580HV) in 1999. The watchmakers took some convincing, but they eventually understood the interest of this technology for their industry. Since then, the luxury watchmaking sector represents more than 90% of the Sion-based company’s sales.
At the end of 2006, Mimotec SA and UlysseNardin SA founded Sigatec SA, a company specialising in the manufacture of watch components in silicon and based in the same premises as Mimotec. From 2008 to 2009, Mimotec invested in building its own production site despite a difficult period due to the economic crisis. The healthy finances of the company meant that 60% of the construction costs were auto-financed. With ultra-modern equipment and a 300m2 clean room, the production capacity could be increased four-fold. Today, more than 2,500 references are produced each year, representing close to 2 million components.A technology with multiple advantages
Contrary to traditional manufacturing methods (shavings removal), Mimotec produces its components by building up the matter. The procedure consists of using photolithography to structure a substrate (wafer) on which a photoresist layer is then deposited. Exposed to UV rays, the resin polymerises and the unexposed zones are dissolved during the development process. The cavities that remain correspond to the negative version of the part to be created. The wafer is then immersed in a galvanic bath where it undergoes electro-moulding of material in the cavities.
This incredibly precise technology (+/-2 µm) is ideal for component miniaturisation and pushes back the boundaries of traditional methods. With great freedom of design, this procedure can be applied to up to 3-layer components, which makes it possible to auto-orient one level in relation to the others and to reduce assembly operations. Very sought after in the watchmaking world, UV-LIGA technology has revolutionised and simplified the construction of complicated timepieces. While still relatively unknown in sectors other than watchmaking, this technology is constantly evolving and has very good prospects in various fields, including medical, connector, micro-mould and probe cards, to name only a few.Interesting synergies with Sigatec
Sigatec SA is a joint venture between Mimotec and UlysseNardin. The company is active in both the watchmaking and non-watchmaking sectors and used DRIE dry engraving to manufacture components in silicon. Silicon is interesting in the watchmaking world because the material is not as dense as aluminium (2.33 kg/dm3 compared to 2.7 for aluminium) and therefore consumes less energy in a mechanical watch. What’s more, its 1,000HV hardness (Vickers) means it will never wear down. Certain watch parts with ruby palettes for tribology (escapement anchor) are currently wholly produced out of silicon. By uniting silicon etching technology and LIGA technology, mixed and unique components can be achieved. Take the example of a component with an identification system that is counterfeit-protected (see the image titled Counterfeiting). Beforehand, Sigatec micro-structures the desired pattern on the surface of a silicon wafer. UV-LIGA operations (photolithography and galvanic growth) come next, and then the etched pattern is reproduced from the wafer to the surface of the electro-moulded part.
Another interesting application is in the manufacture of mould inserts with micro-structuring that is so fine that it is not achievable with UV-Liga technology. The example in the image titled Nanostructure is a hard nickel insert containing 42 million 3µm-diameter cones for applications in the biomedical sector, which illustrates the possibilities of these technologies in the world of miniaturisation. In other words, what is a tolerance limit for some becomes a geometric shape for Sigatec.
Mimotec is currently very active in the watchmaking sector and is very motivated to develop its non-watchmaking activities. The micro-mould sector is making a comeback in our regions. This application field helped Mimotec to launch its activities at the end of the 90s and had almost been eclipsed by Chinese companies. Indeed, in China an extremely cheap workforce and financial grants from the government meant that Europe was no longer in the running. Now there are certain signs that this situation is being reversed. Using innovative technology for high value-added part production, Mimotec will assuredly play an important role in non-watchmaking applications that require great precision, finesse in detail and consistent series-prototype quality.
Nanostructure A hard-nickel insert for applications in the biomedical sector with 3µm-diameter cones.
En français dans le texte
Micropièces pour grandes idées
A la fin des années 90, le Dr. Hubert Lorenz met au point à l’EPFL le processus de fabrication UV-LIGA en s’inspirant de ce qui se faisait dans le monde des circuits électroniques. Rapidement, l’efficacité de cette technologie idéale pour la miniaturisation de composants et d’une grande liberté de design est démontrée et intéresse l’horlogerie d’autant plus que le silicium a une densité plus faible que l’aluminium et du coup consomme moins d’énergie et que sa dureté le rend quasi inusable.
Mimotec, l’entreprise qu’a créé Hubert Lorentz à Sion en 1998, a pu ainsi multiplier les commande, en particulier dans la haute horlogerie, avec à ce jour plus de 2500 références différentes produites chaque année, représentant près de 2 millions de composants. Fin 2006, Mimotec et Ulysse Nardin fondent aussi Sigatec spécialisée dans la fabrication de composants horlogers en silicium grace au procédé de gravure sèche DRIE. En conjuguant cette technologie à celle du LIGA, il est possible de réaliser des composants mixtes et uniques permettant, par exemple, de se prémunir de la contrefaçon.