Electronic Component External Electrode Solder Adhesion

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Solution Overview

Problem

Conventional electronic components with gold bumps on circuit boards experience insufficient adhesion strength due to incomplete solder wrapping around the joint portions, leading to unstable mounting.

Innovation Solution

The electronic component features external electrodes with a first electrode layer joined to the element body and a second electrode layer laid inside the edge of the first layer, having a planar apical surface and a rounded joint portion, increasing the contact area with solder for enhanced adhesion. The first layer may contain glass for increased joint strength, while the second layer, without glass, ensures high conductivity and malleability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If solder is used to join gold bumps to corresponding pads on a circuit board, then mounting cost is reduced and mounting process is simplified, but solder fails to fully wrap around the joint portion resulting in insufficient adhesion strength

Engineering Contradiction:

Improvemounting cost and process simplicityVSAvoidadhesion strength between electronic component and circuit board

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The external electrode is divided into two distinct layers: a first electrode layer (gold bump) joined to the element body, and a second electrode layer (wetting prevention layer) laid on the inside region of the first layer. This segmentation allows each layer to perform its specific function - the first layer provides mechanical attachment while the second layer controls solder flow and prevents excessive wetting, thereby achieving both easy mounting and strong adhesion.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second electrode layer is positioned specifically on the inside region inside the edge of the first electrode layer, creating a localized structure with different properties. This local quality modification ensures that solder flows appropriately to the edges while preventing excessive wrapping around the joint portion, thus maintaining strong adhesion without compromising mounting ease.

Inventive Principle:

Principle #3Local quality

2Reliability

If the second electrode layer is made thicker to improve conductivity, then electrical conductivity increases, but impact stress absorption requires higher malleability which glass components reduce

Engineering Contradiction:

Improveelectrical conductivityVSAvoidimpact stress resistance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The external electrode uses a composite structure with the first electrode layer containing a glass component for joint strength and the second electrode layer containing no glass component for high conductivity and malleability. This composite material approach allows the thicker second layer to provide both electrical conductivity and impact stress absorption without the brittleness that would result from adding glass.

Inventive Principle:

Principle #40Composite materials

3Stability of the object's composition

If the apical surface of the second electrode layer is made planar for stable mounting, then mounting stability improves, but solder flow to the boundary region may be restricted

Engineering Contradiction:

Improvemounting stabilityVSAvoidsolder contact area and wettability

Core Design Contradiction:

Stability of the object's compositionVSStrength

Solution Approach 1:

The joint portion in the second electrode layer to the first electrode layer is rounded rather than sharp-edged. This curvature facilitates solder flow to the boundary region between the two layers, ensuring adequate wetting and contact area while the planar apical surface maintains mounting stability. The rounded joint portion acts as a solder flow guide without compromising positional stability.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 the adhesion strength between the electronic component and the circuit board, providing stability and preventing degradation, even under impact, by increasing the solder contact area and wettability, and absorbing stress effectively.

Implementation Method 1

When the joint portion in the second electrode layer to the first electrode layer is rounded, the solder adequately flows as far as a region corresponding to a boundary part between the first electrode layer and the second electrode layer. For this reason, solder wettability to the external electrode becomes improved

Methodology Applied

Scientific EffectSurface tension: Surface Tension

Implementation Method 2

When the first electrode layer contains the glass component, the joint strength is enhanced between the element body and the first electrode layer with solder

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS8106506B2Electronic component

Publication Date: 2012.01.31 TDK CORP

AI summary

An electronic component has an element body, and a plurality of external electrodes formed on one principal face of the element body. Each external electrode has a first electrode layer joined to the one principal face of the element body, and a second electrode layer joined as laid on an inside region inside an edge of the first electrode layer. An apical surface of the second electrode layer is planar. A joint portion in the second electrode layer to the first electrode layer is rounded.