Appearing in 1998, UV-LIGA is an additive manufacturing technology that combines lithography (using UV exposure) and electroplating. The acronym UV-LIGA directly refers to this process. Traditional manufacturing methods generally involve the use of specific machinery (machining centres, stamping presses, or electrical discharge machining). UV-LIGA technology consists more of a segmented process divided into different steps:

1. Component Design

UV-LIGA technology allows for component profiles that are impossible to achieve with other manufacturing methods. For example, an escape wheel can be designed with a structured cutout to reduce weight without compromising stiffness. Therefore, it is crucial to fully understand this technology to incorporate its benefits from the component design stage.

2. Creation of the Photomask

The component profile to be produced is printed at a 1:1 scale on a glass plate. The component is replicated as many times as possible on the surface of the photomask. Thus, UV light will only pass outside the contours of the components to be produced.

3. Wafer Fabrication

The wafer essentially acts as the mould that will allow the component to be fabricated through additive growth. It consists of a plate whose surface is gilded to improve electrical conductivity. A layer of photosensitive resin thicker than the component to be manufactured is then applied to the previously gilded surface of the wafer.

4. Mould Structuring

This step involves overlaying the photomask onto the wafer and irradiating the surface with UV rays. Naturally, through the filter of the photomask, only the component surfaces are shielded from the UV rays. The resin exposed to UV rays hardens by polymerization and cannot be dissolved in the subsequent step.

5. Dissolution of the Non-Irradiated Resin

After exposure to UV rays, the wafer is dipped into a bath that precisely dissolves the wafer surfaces that were not exposed to UV rays, specifically the exact surfaces of the components to be produced. This operation creates as many moulds of the component to be produced as the wafer’s surface can accommodate. At this stage, the component mould is completed, along with the lithographic part of the process.

6. Component Fabrication by Material Growth

The mould is immersed in an electroplating bath. An electric current flows between an anode submerged in the bath and the base of the mould (gilded), which acts as the cathode. Metal particles suspended in the bath deposit in successive layers at the bottom of the mould and then over the entire height of the component, perfectly respecting its outlined limits defined by the resin. All conductive metals used for electroplating treatments are therefore eligible for this technology.

7. Surface Finishing

The upper surface of the mould-components assembly is then machined to bring all components to their final thickness and to ensure flatness and parallelism of the various component surfaces.

8. Mould Dissolution

Once machined, the assembly is immersed in a bath that dissolves the hardened resin of the mould and its substrate. The finished components are freed from the mould and ready for assembly.

UV-LIGA technology offers numerous advantages over traditional component production methods. The design and technical features of components have immediately benefited. Due to the precision level offered by this method and the absence of any mechanical stress during component fabrication, the limits in terms of technicality and design are impressively extended.

Although the process involves several steps, the implementation is rapid and the cost is controlled. It is suitable for both prototyping and large-scale production. Components produced by this process are always perfectly identical and conform to the original plan. Precision is at the micron level, and in the total absence of tooling, tightly rigorous tolerances can be achieved.

From this precision, and by the absence of cutting tools, surface states most of the time require no treatment. This is a major advantage, especially when it comes to gears since frictions are minimised by the quality of surfaces obtained through this technology.

This technology finds applications in electronics (MEMS), medtech, and aerospace. Its field of applications in watchmaking is extensive: escapements, mobiles, micro-gears, springs, etc.

These numerous advantages, along with the significant number of materials eligible for this process, have quickly made it a pivotal and widely used technology. Materials of different natures have been specifically developed for this technology, further expanding the realm of possibilities. This technology has truly liberated the creativity of designers and the performance of watches. With the emergence of silicon, UV-LIGA technology constitutes one of the major advancements of the last century.