Dual-Layer Metallization for Ultrasonic Wire Bonding on Oxide Ceramics

Solution Overview

Problem

Existing metallizations on oxide ceramics, particularly those used in piezoelectric transducers, suffer from mechanical stress due to ultrasound-induced vibrations during wire bonding, leading to spalling and cracking, which compromises the adhesive strength of the bond.

Innovation Solution

A dual-layer metallization system is employed, where the first layer is made of transition metals or metal alloys with ultrasonic damping properties and the second layer is predominantly precious metals for conductivity and corrosion resistance, minimizing mechanical stress and enhancing bond adhesion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a refractory metal layer is used as adhesion promoting layer, then adhesion to oxide ceramic is improved, but resistance to ultrasound-induced mechanical stress deteriorates

Engineering Contradiction:

Improveadhesive strengthVSAvoidresistance to mechanical stress

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The metallization is divided into multiple functional layers: a refractory metal layer for adhesion promotion and a precious metal layer for mechanical protection and conductivity. This segmentation allows each layer to specialize in its optimal function without compromise.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses a composite metallization structure combining refractory metals (Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) with precious metals (Au, Pt, Ir, Pd, Os, Ru, Ag). This composite approach leverages the high oxygen affinity of refractory metals for adhesion and the high ductility and ultrasound resistance of precious metals.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a precious metal layer is used for electrical conductivity and bondability, then electrical performance is improved, but resistance to ultrasound-induced mechanical stress deteriorates

Engineering Contradiction:

Improveelectrical conductivityVSAvoidresistance to mechanical stress

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The metallization is divided into multiple functional layers: a refractory metal layer for adhesion promotion and a precious metal layer for mechanical protection and conductivity. This segmentation allows each layer to specialize in its optimal function without compromise.

Inventive Principle:

Principle #1Segmentation

3Device complexity

If a single-layer metallization is used, then device complexity is reduced, but ability to simultaneously provide adhesion, conductivity, and mechanical protection deteriorates

Engineering Contradiction:

Improvemetallization structureVSAvoidoverall performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The metallization is divided into multiple functional layers: a refractory metal layer for adhesion promotion and a precious metal layer for mechanical protection and conductivity. This segmentation allows each layer to specialize in its optimal function without compromise.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The precious metal layer serves multiple functions simultaneously: it provides electrical conductivity, mechanical protection against ultrasound-induced stress, and bondability for wire bonding. This multi-functionality compensates for the increased structural complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 dual-layer metallization effectively reduces mechanical stress from ultrasound, preventing damage to the support and improving the adhesive strength of the bond, ensuring durability and robustness against mechanical impacts.

Implementation Method 1

The first layer is made of transition metals and/or metals and/or semi-metals. The first layer has an ultrasonic damping effect.

Methodology Applied

Scientific EffectUltrasonic damping: Damping

Implementation Method 2

The refractory metal layer serves as an adhesion promoting layer since it provides good adhesion to the oxide ceramics due to its high oxygen affinity.

Methodology Applied

Scientific EffectOxygen affinity adhesion: Chemical Bonding

Implementation Method 3

The precious metal layer on the other hand is used for good electrical conductivity and/or bondability of the layer.

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS20250234786A1Metallization and support comprising a metallization

Publication Date: 2025.07.17 KISTLER HLDG AG

AI summary

A system includes a support and at least one metallization that defines at least a first layer and a second layer. The support defines a support surface on which the first layer is arranged between the support surface and the second layer, which is made of at least 90% by weight of a precious metal. The first layer is made of transition metals and/or metals and/or semi-metals and has an ultrasonic damping effect.