Coil Device Terminal Electrode Segmentation for Bonding Reliability

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Solution Overview

Problem

Conventional coil devices experience bonding strength and reliability issues due to film residue and heat-induced melting of the Sn layer during thermocompression bonding, leading to voids and cracks in connecting members.

Innovation Solution

The coil device features separately provided wire connecting and mounting parts on the terminal electrodes, positioned away from each other, which reduces film residue adherence and minimizes heat impact, enhancing bonding strength and reliability while allowing for a more compact design with reduced direct current internal resistance (DCR).

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If thermocompression bonding is used to connect the wire end to the terminal electrode, then the connection is achieved, but film residue is left on the mounting surface causing voids and reducing connection reliability

Engineering Contradiction:

Improveconnection reliabilityVSAvoidfilm residue

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The terminal electrode is divided into two separate parts: a wire connecting part for thermocompression bonding and a mounting part for mounting. This segmentation prevents film residue generated at the wire connecting part from affecting the mounting surface, thereby eliminating voids and improving connection reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The mounting part is extracted and positioned away from the wire connecting part along the outer peripheral direction of the flange. This extraction removes the mounting surface from the harmful zone where film residue is generated during thermocompression bonding, preventing contamination.

Inventive Principle:

Principle #2Taking out (Extraction)

2Strength

If thermocompression bonding is used to connect the wire end to the terminal electrode, then the connection is achieved, but the Sn layer on the mounting surface melts and reduces adhesion strength

Engineering Contradiction:

Improvebonding strengthVSAvoidheat influence

Core Design Contradiction:

StrengthVSTemperature

Solution Approach 1:

The terminal electrode is segmented into a wire connecting part and a mounting part positioned away from each other. This segmentation isolates the mounting part from the heat generated during thermocompression bonding at the wire connecting part, preventing Sn layer melting and maintaining adhesion strength.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The spatial separation along the outer peripheral direction of the flange acts as an intermediary distance that blocks heat transfer from the wire connecting part to the mounting part, protecting the Sn layer from thermal damage.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of energy

If the wire connecting part is positioned closer to the winding core, then the DCR is reduced, but the terminal electrode structure becomes more complex

Engineering Contradiction:

Improvedirect current internal resistanceVSAvoidterminal electrode structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The terminal electrode is segmented into functionally distinct parts: the wire connecting part positioned close to the winding core for low DCR, and the mounting part positioned away for reliable connection. This segmentation allows optimization of each part's position for its specific function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different parts of the terminal electrode are given different local qualities and positions: the wire connecting part is located inner peripherally close to the winding core to minimize resistance, while the mounting part is located outer peripherally for optimal mounting. This local differentiation achieves low DCR without excessive complexity.

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 configuration improves connection reliability and bonding strength by preventing film residue adherence and heat-induced melting, while also reducing DCR and enhancing handling properties.

Implementation Method 1

the end of the wire forming the coil is connected to the terminal electrode having the mounting surface by thermocompression bonding

Methodology Applied

Scientific EffectThermocompression bonding:

Data Source

PatentUS11657956B2Coil device and pulse transformer

Publication Date: 2023.05.23 TDK CORP

AI summary

A coil device 1 including a winding core 11 and flanges 12, 12, wires 31 to 34 wound around the winding core 11 and having one end located at the flanges 12, 12, and terminal electrodes 51 to 56 provided on the flanges 12, 12. The terminal electrodes 51 to 56 includes a wire connecting part 63a, 63b to which the one end of the wires 31 to 34 are connected and a mounting part 65 formed continuously to the wire connecting part 63a, 63b and to be positioned away from an axis of the winding core with respect to the wire connecting parts 63a, 63b along an outer peripheral direction of the flanges 12, 12.