Ultrasound-Damping Metallization for Oxide Ceramic Wire Bonding
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Solution Overview
Problem
Existing metallization methods for oxide ceramics, particularly those used in piezoelectric sensors, suffer from mechanical stress and damage due to ultrasound vibrations during wire bonding, leading to spalling, cracks, and reduced adhesive strength.
Innovation Solution
A dual-layer metallization system is employed, where a first layer made of transition metals or semimetals provides ultrasound damping, and a second layer composed of at least 90 wt.% precious metals ensures high conductivity and corrosion resistance, minimizing mechanical stress and enhancing adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer precious metal metallization is used, then good electrical conductivity and corrosion resistance are achieved, but mechanical stress from ultrasound vibrations causes spalling, cracks, and reduced adhesive strength
Solution Approach 1:
The patent applies a composite metallization structure consisting of a first layer (adhesion promoter layer made of refractory metal) and a second layer (precious metal layer for conductivity). This composite structure combines the high oxygen affinity and adhesion properties of refractory metals with the excellent electrical conductivity and corrosion resistance of precious metals, while the layered configuration helps distribute and mitigate mechanical stress from ultrasound vibrations during wire bonding.
Solution Approach 2:
The metallization is segmented into two distinct functional layers: a first layer specifically designed for adhesion to the oxide ceramic carrier, and a second layer optimized for electrical conductivity and bondability. This segmentation allows each layer to perform its specialized function optimally while collectively providing resistance to vibration-induced mechanical stresses.
2Strength
If refractory metal is used as adhesion promoter, then good adhesion to oxide ceramic is achieved, but low damping properties transmit ultrasound vibrations causing mechanical damage
Solution Approach 1:
The patent combines refractory metal (for adhesion) with precious metal (for conductivity and improved damping characteristics) in a layered composite structure. This composite metallization maintains the essential adhesion properties of refractory metals while introducing materials with better vibration damping capabilities, thereby reducing the transmission of ultrasound-induced mechanical stresses to the piezoelectric crystal.
3Ease of operation
If wire bonding is performed on oxide ceramic carriers, then electrical connection is achieved, but ultrasound vibrations cause spalling and cracks in the substrate
Solution Approach 1:
The dual-layer metallization structure provides an optimized bonding surface for wire bonding operations. The precious metal layer offers excellent bondability and electrical conductivity, while the underlying refractory metal layer ensures strong adhesion to the carrier. This composite structure acts as a protective interface that mitigates the transmission of harmful ultrasound vibrations to the piezoelectric crystal during the wire bonding process.
Solution Approach 2:
The metallization layers serve as an intermediary between the wire bonding process and the piezoelectric crystal carrier. This intermediate metallization structure absorbs and dissipates vibration energy, protecting the fragile piezoelectric material from direct exposure to the mechanical stresses generated during ultrasound wire bonding operations.
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 vibrations, preventing damage to the carrier and improving the adhesive strength of the bond, ensuring robust and durable connections.
Implementation Method 1
The first layer is made of transition metals and/or metals and/or semimetals. The first layer is ultrasonic-damping. This has the advantage of reducing the mechanical stress on the substrate caused by vibrations such as ultrasound.
Implementation Method 2
The refractory metal layer serves as an adhesion promoter layer, as its high oxygen affinity enables good adhesion to the oxide ceramics.
Implementation Method 3
The precious metal layer, on the other hand, provides good electrical conductivity and/or bondability of the layer.
Data Source
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AI summary
System (36) comprising a carrier (3) and at least one metallization (6); wherein the metallization (6) has at least a first layer (1) and a second layer (2); wherein the carrier (3) has a carrier surface (7); wherein the first layer (1) is arranged between the carrier surface and the second layer (2); wherein the second layer (2) is made of at least 90 wt.% of a noble metal; wherein the first layer (1) is made of transition metals and/or metals and/or semimetals; wherein the first layer (1) is ultrasound-damping.