Al Bonding Wire Composition for Stable Second-Bond Strength
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Solution Overview
Problem
Aluminum (Al) bonding wires used in power semiconductor devices face challenges in achieving stable bonding strength, particularly at the second bonded part, due to the difficulty in breaking surface oxide films and forming strong bonds with substrates having a firm Ni oxide film, leading to potential peeling and manufacturing yield issues.
Innovation Solution
The Al bonding wire contains 0.01-0.8 mass% of Sc, Zr, and Mg, with a crystal orientation ratio of 30-90 degrees to the wire axis, and additional elements like Pd, Pt, Ni, and Fe/Si to enhance mechanical strength and surface properties, ensuring stable bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-purity Al bonding wire is used, then electrical conductivity is improved, but bonding strength at the second bonded part deteriorates due to inability to sufficiently break surface oxide films
Solution Approach 1:
The patent changes the chemical composition parameters of the bonding wire by adding specific elements (Sc: 0.01-0.5 mass%, Zr: 0.01-0.5 mass%, Mg: 0.01-0.3 mass%) to high-purity Al. These compositional changes modify the material properties to enable sufficient oxide film breaking while maintaining electrical conductivity, resolving the contradiction between conductivity and bonding strength.
Solution Approach 2:
The patent creates a composite material system by combining Al with trace elements (Sc, Zr, Mg) that have specific functions. Sc and Zr contribute to oxide film breaking capability, while Mg controls crystal grain growth. This composite approach maintains the high conductivity of Al while adding the necessary bonding strength through the synergistic effects of the alloying elements.
2Adaptability or versatility
If Al bonding wire is used with substrate having firm Ni oxide film, then adaptability to different substrates is improved, but bonding strength deteriorates due to peeling defects
Solution Approach 1:
The patent modifies the bonding wire composition parameters by adding Sc (0.01-0.5 mass%) and Zr (0.01-0.5 mass%), which enhance the ability to break through the firm Ni oxide film on the substrate surface. This compositional adjustment enables the bonding wire to effectively bond with Ni-deposited substrates while preventing peeling defects, thus resolving the contradiction between substrate adaptability and bonding strength.
3Ease of operation
If bonding wire material is softened to improve bond quality at first bonded part, then ease of bonding is improved, but ability to break surface oxide films deteriorates
Solution Approach 1:
The patent carefully balances the composition parameters by adding Mg (0.01-0.3 mass%) which controls crystal grain growth and maintains material softness for good bond quality, while simultaneously adding Sc (0.01-0.5 mass%) and Zr (0.01-0.5 mass%) which provide oxide film breaking capability. This multi-parameter compositional control resolves the contradiction between ease of bonding and oxide film breaking ability.
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 composition and crystal orientation configuration improve mechanical strength, reduce oxide film breaking variations, and enhance bonding stability at the second bonded part, addressing the issue of peeling and yield concerns in power semiconductor devices.
Implementation Method 1
The wedge bonding is a method of applying ultrasonic waves and a load to the bonding wire via a jig made of metal, breaking surface oxide films of a bonding wire material and an electrode material to expose new surfaces, and performing solid phase diffusion bonding.
Implementation Method 2
applying ultrasonic waves and a load to the bonding wire via a jig made of metal, breaking surface oxide films of a bonding wire material and an electrode material to expose new surfaces, and performing solid phase diffusion bonding
Data Source
AI summary
To provide an Al bonding wire for semiconductor devices that stably exhibits a favorable bonding strength at a second bonded part. An Al bonding wire for semiconductor devices containing equal to or larger than 0.01 mass % and smaller than 0.8 mass % of one or more of Sc, Zr, and Mg in total, wherein, as a result of measuring a crystal orientation on a cross-section parallel to a wire axis direction including a wire axis of the bonding wire, 10 an orientation ratio of a <100> crystal orientation angled at 15 degrees or less to the wire axis direction is equal to or higher than 30% and equal to or lower than 90%.