Silicon Hairspring Thermal Compensation via Doping

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Solution Overview

Problem

Existing timepiece components, such as hairsprings, face challenges in achieving optimal performance due to sensitivity to temperature variations and magnetic fields, with complex manufacturing processes and compromises in mechanical properties.

Innovation Solution

A process involving the deposition of a polycrystalline or monocrystalline silicon layer on a substrate, followed by etching and release, to create a timepiece component with uniform doping for thermal compensation, resulting in a component that is insensitive to temperature and magnetic fields.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a silicon hairspring with thick oxide layer is used for thermal compensation, then temperature insensitivity is improved, but manufacturing complexity and processing time increase

Engineering Contradiction:

Improvetemperature sensitivityVSAvoidmanufacturing process complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent changes the material parameter by using heavily doped silicon (with doping concentration of 10^19 to 10^21 atoms/cm³) instead of relying on thick oxide layers. This material parameter change achieves thermal compensation while avoiding complex high-temperature oxidation processes, thus resolving the contradiction between temperature insensitivity and manufacturing complexity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical/thermal system of thick oxide layer compensation with a doping-based material property system. By controlling the electrical and thermal properties through doping, the patent achieves thermal compensation without the complex oxidation treatment processes, reducing manufacturing complexity while maintaining temperature insensitivity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Object-affected harmful factors

If heavily doped silicon is used for thermal compensation, then temperature insensitivity is improved, but achieving the required doping level becomes difficult

Engineering Contradiction:

Improvetemperature sensitivityVSAvoiddoping level control

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent applies preliminary doping action during the silicon layer deposition process itself, incorporating dopants into the silicon structure from the beginning. This preliminary doping approach ensures the required high doping levels are achieved without needing subsequent complex high-temperature diffusion processes, thereby improving both doping level control and temperature insensitivity

Inventive Principle:

Principle #10Preliminary action

3Strength

If ferromagnetic alloy hairspring is used, then mechanical properties are improved, but magnetic sensitivity and frequency drift increase

Engineering Contradiction:

Improvemechanical propertiesVSAvoidmagnetic sensitivity

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent uses composite material approach by combining silicon with heavy doping to create a material that provides both the required mechanical properties and magnetic insensitivity. The heavily doped silicon structure offers adequate mechanical strength while being inherently insensitive to magnetic fields, thus resolving the contradiction between mechanical properties and magnetic sensitivity without requiring heat treatments that cause frequency drift

Inventive Principle:

Principle #40Composite materials

4Stability of the object's composition

If heat treatment is applied to reduce frequency drift, then long-term stability is improved, but manufacturing time and energy consumption increase

Engineering Contradiction:

Improvefrequency stability over timeVSAvoidheat treatment time

Core Design Contradiction:

Stability of the object's compositionVSLoss of time

Solution Approach 1:

The patent applies self-service principle by incorporating the doping process during the initial deposition stage, where the doping occurs simultaneously with layer formation. This self-integrated approach achieves the required material properties without requiring separate, time-consuming post-deposition heat treatment steps, thus improving frequency stability while reducing manufacturing time and energy consumption

Inventive Principle:

Principle #25Self-service

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 process simplifies manufacturing, reduces component sensitivity to temperature and magnetic fields, and enhances mechanical stability, enabling precise and robust operation of timepiece oscillators.

Implementation Method 1

notably comprises at least the following steps: a. providing a substrate made of semiconductor material or metal material; b. carrying out the deposition of a polycrystalline- or monocrystalline-silicon layer onto the substrate

Methodology Applied

Scientific EffectVapor deposition: Physical Vapour Deposition

Data Source

PatentUS20230136065A1Silicon timepiece component for a timepiece

Publication Date: 2023.05.04 ROLEX SA

AI summary

The method for manufacturing a timepiece component is capable of thermocompensating a functional assembly including the timepiece component. The method includes at least the following actions: a) providing (e1) a substrate (1) of semiconductor or metallic material; b) proceeding with the deposition (e2) of a polycrystalline or monocrystalline silicon layer (5) on the substrate (1); c) releasing (e4) the timepiece component (10) from the substrate (1).