Stranded Wire Contact Diffusion Bonding Without Solder Heat Damage

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Solution Overview

Problem

Existing methods for creating stranded contacts in electrical components, such as inductive components, face challenges with insulation removal during soldering, leading to damage, increased risk of failure, and high costs due to high temperatures and unwanted solder balls.

Innovation Solution

The use of thermal diffusion bonding to connect individual wires in a stranded wire to a contact piece without separate insulation removal, using a metallic contact piece that is electrically conductive and mechanically fixative, allowing for an intimate atomic-level connection at temperatures below the materials' melting points, thus avoiding soldering and its associated issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If soldering processes are used to create stranded wire contacts, then mechanical and electrical connections are established, but the high temperatures cause damage to insulation and functional elements

Engineering Contradiction:
Improveconnection strengthVSAvoidthermal damage to insulation
Core Design Contradiction:
StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent changes the temperature parameter from soldering temperatures (400°C) to diffusion bonding temperatures (below melting point of materials), thereby establishing strong connections without thermal damage to insulation and functional elements

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent replaces the thermal-melting mechanism of soldering with a solid-state diffusion bonding mechanism, where atomic diffusion at elevated temperatures creates strong metallurgical bonds without requiring the materials to melt

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Ease of manufacture

If high temperatures are used to remove insulation during soldering, then insulation is effectively removed, but solder balls are created and component reliability decreases

Engineering Contradiction:
Improveinsulation removalVSAvoidcomponent reliability
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent performs insulation removal as a preliminary step before diffusion bonding, using mechanical or chemical methods at low temperatures, thereby eliminating the need for high-temperature insulation removal and preventing solder ball formation

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent converts the previously harmful effect of high temperatures into a beneficial controlled thermal process where moderate heat is used solely for diffusion bonding after insulation is already removed, eliminating harmful side effects while maintaining bonding effectiveness

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

3Ease of manufacture

If two-step manufacturing processes are used for high-temperature insulation, then insulation is reliably removed, but manufacturing complexity and time increase

Engineering Contradiction:
Improveinsulation removal reliabilityVSAvoidmanufacturing process complexity
Core Design Contradiction:
Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent merges the insulation removal step and the connection creation step into a unified manufacturing flow, where insulation is removed first and then diffusion bonding is performed in a controlled sequence, simplifying the overall process while maintaining reliability

Inventive Principle:
Principle #5Merging (Combining)

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

This method provides a reliable, cost-effective, and solder-free connection that prevents damage to nearby components, eliminates solder balls, and ensures a strong mechanical and electrical bond between the stranded wire and the contact piece.

Implementation Method 1

The contact piece is connected to the stranded wire by thermal diffusion bonding. In diffusion bonding, the individual wires are bonded to the contact piece under pressure and at elevated temperatures. The temperature is lower than the melting point of the contact piece material and the material of the individual wires. In diffusion bonding, two-way diffusion occurs at the atomic level across the interfaces of the parts to be joined, creating an intimate connection between the parts.

Methodology Applied
Scientific EffectThermal diffusion bonding: Diffusion Welding

Data Source

PatentEP3685479B1Strand contact for an electric component and method for producing a strand contact
Publication Date: 2024.12.11 TDK ELECTRONICS AG
  • EP3685479B1 patent drawingFigure 1A~1B
  • EP3685479B1 patent drawingFigure 2~3A
  • EP3685479B1 patent drawingFigure 3B~3C

AI summary

The invention relates to an electric component (8) having a strand contact (1), comprising a strand wire (2) with a plurality of individual wires (4) and a contact piece (100) for electrically contacting the strand wire (2), the strand contact (1) being produced by thermal diffusion bonding.