Multilayer Coating for Brazing Non-Metallic Watch Components
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Solution Overview
Problem
Existing methods for assembling watch components using non-metallic materials, such as silicon, diamond, and ceramics, face challenges with adhesion and wettability issues due to the fragility of these materials and the limitations of traditional brazing processes, which result in poor long-term behavior and inadequate torque transmission.
Innovation Solution
A multilayer metallic coating is applied to the components, comprising a first layer with strong adhesion to the base material and a second layer with high wettability for the filler metal, optionally including a third layer to prevent oxidation and serve as a diffusion barrier, allowing precise and reproducible brazing without surface propagation of the filler metal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single-layer metallic coating is applied to non-metallic watch components, then adhesion to the base material is achieved, but wettability by filler metal deteriorates
Solution Approach 1:
The single-layer metallic coating is segmented into multiple layers with distinct functions: a first layer (e.g., chromium, titanium, or tantalum) optimized for adhesion to the non-metallic base material, and a second layer (e.g., nickel, palladium, or platinum) optimized for wettability by the filler metal. This segmentation allows each layer to specialize in one function, resolving the contradiction between adhesion strength and brazing reliability.
Solution Approach 2:
Different regions of the coating system are assigned different material properties: the first layer has high adhesion quality for bonding to silicon/diamond/ceramic, while the second layer has high wettability quality for filler metal interaction. This local differentiation of material qualities enables simultaneous optimization of both adhesion and brazing characteristics.
2Reliability
If a metallic deposit is applied to improve wettability, then filler metal bonding is enhanced, but oxidation of the deposit occurs leading to loss of wettability
Solution Approach 1:
The first layer is applied in advance as a protective barrier before the second layer. This preliminary adhesion layer prevents oxidation of the base material and provides a stable substrate for the second layer, ensuring the second layer maintains its wettability properties throughout the brazing process.
Solution Approach 2:
The first metallic layer acts as an intermediary between the non-metallic base material and the second metallic layer. It mediates the interaction by providing a stable, oxidation-resistant interface that supports the wettability-functioning second layer, preventing direct oxidation of the wettability-critical surface.
3Measurement precision
If non-metallic materials are used for watch components, then precision and efficiency are improved, but assembly by pressing is no longer possible due to fragility
Solution Approach 1:
The mechanical pressing assembly method is replaced with a thermal-brazing process. Instead of mechanically pressing components together (which fails due to fragility), the invention uses controlled heating to melt filler metal that bonds components thermally, enabling assembly of fragile non-metallic materials without mechanical stress.
Solution Approach 2:
The assembly process parameters are changed from room-temperature mechanical pressing to elevated-temperature thermal brazing. By changing the temperature parameter and the bonding mechanism from mechanical to thermal, the process becomes compatible with fragile non-metallic materials while maintaining assembly effectiveness.
4Ease of manufacture
If elastic mounting is used for non-metallic components, then assembly is simplified, but torque transmission capability is reduced
Solution Approach 1:
The elastic mounting mechanical system is replaced with a thermal-brazed joint system. Instead of relying on elastic deformation and friction for torque transmission, the invention creates a solid-state metallurgical bond through filler metal, enabling high torque transmission while maintaining assembly simplicity through the brazing process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method ensures strong and reliable assembly of watch components with improved adhesion and wettability, preventing filler metal migration and maintaining the intrinsic properties of the non-metallic materials, while allowing for precise control of the brazing process and high torque transmission.
Implementation Method 1
a first layer in contact with the first watch component and made of a first metallic material and, on the first layer, a second layer made of a second metallic material different from the first metallic material
Implementation Method 2
the second metallic material may be chosen to have better wettability by the filler metal than the first metallic material
Implementation Method 3
b) braze the second watch component to said at least a part of the first watch component
Implementation Method 4
deposit a filler metal onto the multilayer metal coating; melt the filler metal so that it bonds the first and second watch components
Implementation Method 5
a third layer made of a third metallic material different from the second metallic material and chosen to mix with the filler metal during step b), this third layer protecting the second layer from oxidation and thus preserving the wettability of the second layer
Implementation Method 6
the second layer can serve as a diffusion barrier preventing, during step b), the migration of atoms from the first metallic material
Data Source
Figure 1~2(d)
Figure 3~4
AI summary
A method for assembling a first watch component (1) made of a base material, typically non-metallic, and a second watch component (5). The method comprises the following steps: a) depositing a multilayer metallic coating (7) onto at least a portion of the first watch component (1), the multilayer metallic coating (7) comprising a first layer (7a) in contact with the first watch component (1) and made of a first metallic material, and, on the first layer (7a), a second layer (7b) made of a second metallic material; and b) brazing the second watch component (5) to at least a portion of the first watch component (1). In one exemplary embodiment, the first metallic material is chosen to have better adhesion to the base material than the second metallic material, and the second metallic material is chosen to have better wettability than the first metallic material.The second layer (7b) can also be a sacrificial protective layer or serve as the filler metal for brazing. The first watch component (1) is, for example, a balance spring, and the second watch component (5) is a stud.