Coil Component Electrode Adhesion for Thermal Stress

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Solution Overview

Problem

The existing coil components face issues with crack generation in solder portions and potential fracturing of the drum core due to stress from temperature changes and substrate deflection, primarily because the outer electrodes are strongly fixed to the component body.

Innovation Solution

A coil component design where the adhesive strength of the bottom-surface electrode portion is lower than the end-surface electrode portion, allowing the bottom-surface electrode to move freely and absorb external forces, with a round chamfered portion and electroplated films used to maintain mechanical strength and prevent magnetic flux blocking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the outer electrode is strongly fixed to the component body, then the electrical connection is stable, but stress from temperature changes and substrate deflection causes cracks in solder portions and fractures in the component body

Engineering Contradiction:

Improveelectrical connection stabilityVSAvoidresistance to thermal stress and mechanical stress

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies different adhesive strengths to different portions of the outer electrode. The end-surface electrode portion has high adhesive strength to the component body for stable electrical connection, while the bottom-surface electrode portion has low adhesive strength to allow stress absorption. This local differentiation resolves the contradiction between connection stability and stress resistance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The outer electrode is divided into two distinct portions: the end-surface electrode portion and the bottom-surface electrode portion. Each portion serves a different function - one for electrical connection and the other for stress absorption. This segmentation allows the electrode system to simultaneously achieve both stable connection and stress resistance.

Inventive Principle:

Principle #1Segmentation

2Stability of the object's composition

If the bottom-surface electrode portion is strongly fixed to the component body, then the overall electrode stability is improved, but the ability to absorb external force and prevent solder cracks is reduced

Engineering Contradiction:

Improveelectrode structural stabilityVSAvoidsolder portion integrity

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent creates a local quality difference in adhesive strength between the bottom-surface electrode portion and the end-surface electrode portion. The bottom portion has deliberately reduced adhesive strength to function as a stress absorption interface, while maintaining overall electrode stability through the strongly fixed end portion.

Inventive Principle:

Principle #3Local quality

3Area of stationary object

If the outer electrode extends to the end surface of the component body, then the electrical connection area is increased, but the component body becomes more susceptible to fracture under stress

Engineering Contradiction:

Improveelectrode contact areaVSAvoidcomponent body fracture resistance

Core Design Contradiction:

Area of stationary objectVSStrength

Solution Approach 1:

The patent extends the outer electrode to the end surface to maximize electrical connection area, but applies different adhesive strength characteristics to different portions. The end-surface electrode portion maintains strong adhesion for electrical connection, while the bottom-surface electrode portion has weak adhesion to prevent stress transmission to the component body, thus preventing fracture.

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 design reduces the likelihood of crack formation in solder portions and component body fractures, enhancing resistance to thermal fatigue and substrate deflection, while maintaining a stable electrical connection.

Implementation Method 1

The above-mentioned outer electrodes are formed by applying and baking an electrically conductive paste containing silver as an electrically conductive component and then performing nickel plating and tin plating.

Methodology Applied

Scientific EffectElectroplating: Electroplating

Implementation Method 2

An adhesive strength of the bottom-surface electrode portion with respect to the component body is lower than an adhesive strength of the end-surface electrode portion with respect to the component body.

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS10381152B2Coil component and coil-component-equipped mounting substrate

Publication Date: 2019.08.13 MURATA MFG CO LTD

AI summary

A coil component has an outer electrode include a bottom-surface electrode portion disposed along a bottom surface of a component body and an end-surface electrode portion disposed along an end surface of the component body so as to be continuous with the bottom-surface electrode portion. The adhesive strength of the bottom-surface electrode portion with respect to the component body is lower than that of the end-surface electrode portion with respect to the component body.