Method for making balance springs on a support

By sorting and correcting balance springs into stiffness classes off the wafer, the method addresses the inefficiencies in existing manufacturing processes, achieving reduced stiffness variation and improved yield and precision in mechanical resonator production.

EP4752645A1Pending Publication Date: 2026-06-03RICHEMONT INTERNATIONAL SA
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Patent Information

Authority / Receiving Office
EP · EP
Patent Type
Applications
Current Assignee / Owner
RICHEMONT INTERNATIONAL SA
Filing Date
2024-11-28
Publication Date
2026-06-03

AI Technical Summary

Technical Problem

Existing manufacturing processes for mechanical resonators, such as balance springs in mechanical watches, suffer from significant geometric variations and stiffness dispersion, leading to inefficiencies and high equipment usage due to the need for corrective operations on each wafer, which do not adequately reduce the standard deviation of stiffness variations.

Method used

A method involving the sorting and correction of balance springs by forming batches based on stiffness classes, allowing for tailored corrective treatments to achieve a target stiffness, reducing the dispersion to fewer than 10 classes, and optimizing machine utilization by applying these corrections off the original wafer.

Benefits of technology

This process significantly improves the yield and precision of balance spring manufacturing by reducing stiffness variation, enabling a larger proportion of springs to meet target specifications, simplifying stock management, and enhancing machine efficiency through targeted corrections.

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Abstract

The invention relates to a method for manufacturing balance springs (20) intended to equip a regulating organ of a timepiece, said method comprising the manufacture of balance springs (20) in at least one silicon wafer (10), this manufacture comprising at least one lithography step to form the pattern of the balance springs (20) on or above said wafer (10) and a machining step in said at least one wafer (10) through said patterns, said method comprising the following steps: (a) determination of the stiffness of each balance spring (20); (b) classification of each balance spring (20) according to its stiffness; (c) formation of batches of balance springs (20) detached from their original wafer by stiffness class; (d) selection of batches of balance springs (20) to be corrected; (e) application of a corrective treatment adapted to said selected batches to modify the stiffness of each spiral (20) of said batches and approach a target stiffness.
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