Electrode Surface Smoothing via Ultrasonic Vibration

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Solution Overview

Problem

Sintered metal electrodes on ceramic substrates often have high surface roughness due to manufacturing processes, leading to insufficient platability, wettability, and increased risk of corrosion and reduced bonding strength during wire bonding, as well as damage to the substrate during plating due to surface irregularities.

Innovation Solution

A method involving the use of vibrating media, such as zirconia balls, in contact with the electrode surface, with ultrasonic waves applied in a treatment liquid to smooth the electrode surface without damaging the substrate, allowing for precise control of surface roughness and preventing macroscopic impurity networks formation during plating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the electrode surface is smoothed by forming a thick plating layer, then surface roughness is reduced, but the substrate is damaged and strength is reduced due to prolonged immersion in plating bath

Engineering Contradiction:

Improvesurface roughnessVSAvoidsubstrate strength

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The patent applies ultrasonic vibration to the plating bath, causing the plating solution to vibrate at high frequency. This vibration enhances mass transport and promotes uniform plating deposition at reduced thickness, achieving surface smoothing without requiring thick plating layers that would damage the substrate through prolonged immersion.

Inventive Principle:

Principle #18Mechanical vibration

Solution Approach 2:

The patent changes the physical parameters of the plating process by introducing ultrasonic vibration frequency and amplitude as new control parameters. This allows the plating process to achieve desired surface finish with thinner deposits by modifying the deposition mechanism through vibrational energy input.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If conventional smoothing methods are used on electrodes from non-shrinkage process, then surface irregularities are reduced, but the electrode surface still retains insufficient smoothness due to constraining layer removal traces

Engineering Contradiction:

Improvesurface smoothnessVSAvoidconstraining layer removal

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

Ultrasonic vibration is applied during the constraining layer removal process, enabling the layers to be detached without leaving significant surface traces. The high-frequency vibration facilitates clean separation and subsequent smoothing of the electrode surface, achieving better finish than conventional mechanical removal methods.

Inventive Principle:

Principle #18Mechanical vibration

3Productivity

If screen-printing process is used to form electrodes, then electrode formation is efficient, but mesh traces remain causing high surface roughness

Engineering Contradiction:

Improveelectrode formation efficiencyVSAvoidsurface roughness

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

Ultrasonic vibration is applied during or after the screen-printing process to eliminate mesh traces from the electrode surface. The vibrational energy breaks down and removes the characteristic screen printing patterns, achieving smooth surfaces while maintaining the efficiency of the screen-printing formation method.

Inventive Principle:

Principle #18Mechanical vibration

4Reliability

If electrodes with high surface roughness are used, then plating and wettability properties are insufficient, but smoothing requires thick plating that damages substrate

Engineering Contradiction:

Improveplating and wettability propertiesVSAvoidsubstrate damage from plating

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Ultrasonic vibration is applied during the plating process to achieve uniform, thin plating layers that provide adequate plating and wettability properties. The vibration enhances solution penetration and deposit uniformity, allowing thin layers to achieve the same functional properties that would otherwise require thick layers, thereby preventing substrate damage.

Inventive Principle:

Principle #18Mechanical vibration

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

The method effectively smooths the electrode surface to mirror polish quality, reducing issues like solder popping and bonding strength reduction, while maintaining the integrity of the substrate and electrode, enabling the formation of dense plating layers with improved reliability.

Implementation Method 1

an ultrasonic wave is applied to the treatment liquid

Methodology Applied

Scientific EffectUltrasonic wave: Ultrasound

Implementation Method 2

smoothing the electrode surface by vibrating media such that the media are arranged to be in contact with the electrode

Methodology Applied

Scientific EffectAbrasion: Abrasion

Data Source

PatentUS8756775B2Method for smoothing a surface of an electrode

Publication Date: 2014.06.24 MURATA MFG CO LTD

AI summary

A method is provided for efficiently and securely smoothing a surface of an electrode disposed on a base, such as a ceramic substrate, without damaging the electrode or the base. The electrode is fired by a non-shrinkage process using a constraining layer and is separated from the constraining layer. The base including the electrode disposed thereon is prepared and a surface of the electrode is smoothed by vibrating media such that the media are arranged to be in contact with the electrode.