Litz Wire Termination via Ferrule Crimping and Molten Solder

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Solution Overview

Problem

Terminating litz wire is challenging due to solder wicking issues and moisture ingress, which can lead to brittleness and poor insulation, especially with small conductors and complex insulation layers.

Innovation Solution

A method involving a ferrule crimped over exposed conductors, submerged in molten solder to bond with the litz wire, ensuring the ferrule and exposed conductors are soldered, followed by heat shrink tubing and an O-ring for additional insulation and moisture resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If solder is applied directly to litz wire conductors, then strong bonding is achieved, but solder wicks up the conductors causing brittleness

Engineering Contradiction:

Improvebonding strengthVSAvoidconnection reliability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

A ferrule is introduced as an intermediary component between the litz wire conductors and the solder. The ferrule provides a controlled interface where solder can bond strongly without wicking up the individual conductors, thus maintaining bonding strength while preventing the harmful wicking effect that causes brittleness.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The termination process is segmented into distinct zones: the ferrule contains the conductors in a controlled manner, allowing solder to bond to the ferrule and selected conductor portions while preventing uncontrolled solder penetration into the litz wire structure. This segmentation isolates the bonding function from the harmful wicking function.

Inventive Principle:

Principle #1Segmentation

2Strength

If insulation is removed from conductors for solder bonding, then strong solder attachment is achieved, but moisture can ingress into the litz wire and termination

Engineering Contradiction:

Improvesolder attachment strengthVSAvoidmoisture ingress

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The solution employs a nested structure where heat shrink tubing is placed over the ferrule and conductor assembly. This outer protective layer seals the moisture-sensitive internal components (exposed conductors and solder joint) without interfering with the solder bonding process, thus protecting against moisture ingress while maintaining strong solder attachment.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

Heat shrink tubing provides a flexible protective shell that conforms to the ferrule and conductor assembly. This thin film barrier prevents moisture ingress while allowing the solder joint to form and bond properly during the termination process.

Inventive Principle:

Principle #30Flexible shells and thin films

3Strength

If ferrule is crimped tightly to conductors, then mechanical strength is improved, but solder wicking resistance may be reduced

Engineering Contradiction:

Improvemechanical strengthVSAvoidsolder wicking resistance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The ferrule design implements local quality by having different functional zones: a crimped section that provides mechanical strength and conductor containment, and an uncrimped or less-compressed section that maintains capillary properties to resist solder wicking. This localized differentiation allows the ferrule to simultaneously achieve mechanical strength and solder wicking resistance.

Inventive Principle:

Principle #3Local quality

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 robust, moisture-resistant termination that minimizes solder wicking and ensures strong bonding, enhancing the reliability and durability of litz wire connections.

Implementation Method 1

crimping the ferrule to the litz wire

Methodology Applied

Scientific EffectCrimping: Mechanical Force

Implementation Method 2

solder bonds to the conductors that are within in the molten solder

Methodology Applied

Scientific EffectSoldering: Soldering

Implementation Method 3

The heat shrink tubing conforms to the exterior surface of the external insulation and to the termination after a process to heat the heat shrink tubing

Methodology Applied

Scientific EffectThermal contraction: Thermal Contraction

Data Source

PatentUS10374329B2Method of making a litz wire solder termination

Publication Date: 2019.08.06 WIRELESS ADVANCED VEHICLE ELECTRIFICATION INC

AI summary

A method for litz wire termination includes placing a ferrule over exposed conductors on an end of litz wire. The exposed conductors include a portion of the litz wire without an external insulation layer, and a portion at the end of the litz wire protrude past the ferrule. The method includes crimping the ferrule to the litz wire and placing the end of the litz wire with the ferrule in molten solder past the end of the ferrule. The method includes maintaining the litz wire in the molten solder until insulation on conductors of the litz wire is removed from the conductors in the molten solder and solder bonds to the conductors that are within in the molten solder. The method includes removing the litz wire from the molten solder and allowing the litz wire to cool until molten solder bonded to the conductors transitions to a solid state.