Pearlitic Steel Canted Coil Spring With Copper Plating Balance

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Solution Overview

Problem

Canted coil springs used in connectors require both settling resistance and conductivity, which zirconium-copper alloys often fail to provide effectively.

Innovation Solution

A canted coil spring with a core wire made of steel having a pearlite structure and a copper plating layer with a crystallite size of 220±50 Å, along with a hard layer for enhanced stability and conductivity, addresses the need for both settling resistance and conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a zirconium-copper alloy is used as the material of the canted coil spring, then the spring can provide settling resistance, but the conductivity is insufficient

Engineering Contradiction:

Improvesettling resistanceVSAvoidconductivity

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The invention uses a composite structure consisting of a steel core wire with pearlite structure and a copper plating layer. The steel core provides high strength and settling resistance, while the copper plating layer provides high conductivity. This composite material approach resolves the contradiction between settling resistance and conductivity by combining materials with complementary properties.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the copper plating layer has a small crystallite size, then the conductivity is improved, but the settling resistance decreases

Engineering Contradiction:

ImproveconductivityVSAvoidsettling resistance

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The invention optimizes the crystallite size of the copper plating layer to a specific range (170-270 nm) to achieve the best balance between conductivity and settling resistance. By controlling the crystallite size parameter within this optimal range, the invention resolves the contradiction between conductivity (improved by smaller crystallite size) and settling resistance (improved by larger crystallite size).

Inventive Principle:

Principle #35Parameter changes

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 canted coil spring achieves high settling resistance and conductivity, ensuring stable electrical coupling with low resistance across varying terminal distances.

Implementation Method 1

The copper plating layer has a crystallite size of 170 nm or more and 270 nm or less, thereby the canted coil spring has high conductivity

Methodology Applied

Scientific EffectGrain boundary scattering:

Implementation Method 2

a core wire formed of steel having a pearlite structure

Methodology Applied

Scientific EffectPearlite structure:

Data Source

PatentUS11674193B2Canted coil spring and connector

Publication Date: 2023.06.13 SUMITOMO ELECTRIC INDUSTRIES LTD

AI summary

A canted coil spring includes a core wire 10 formed of steel having a pearlite structure; and a copper plating layer 20 formed of copper or a copper alloy and covering an outer circumferential surface 11 of the core wire 10. The steel contains 0.5 mass % or more and 1.0 mass % or less carbon, 0.1 mass % or more and 2.5 mass % or less silicon, and 0.3 mass % or more and 0.9 mass % or less manganese, with the balance being iron and inevitable impurities. The copper plating layer 20 has a crystallite size of 220±50 Å.