Bonding Wire with Intermediate Layer for Loop Defect Control
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Solution Overview
Problem
The existing bonding wires face issues with defective loops due to differences in strain and deformation resistance between the core material and the outer layer, leading to snake and sagging loop defects, which affect bonding reliability and mass production usability.
Innovation Solution
A bonding wire with a core material containing more than 50 mol % of a metal M, an intermediate layer of Ni, Pd, and unavoidable impurities, and a coating layer of Ni, Pd, and Au, where the concentrations of Ni and Pd are optimized to absorb deformation resistance differences and inhibit oxidation and sulfuration, reducing the occurrence of snake and sagging loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a bonding wire with a core material and outer layer is used to reduce material cost, then material cost is reduced, but the bonding wire is deformed due to differences in strain and deformation resistance between the core material and the outer layer, causing defective loops
Solution Approach 1:
The bonding wire is divided into three distinct layers: a core material layer (containing metal M such as Cu or Ag), an intermediate layer (containing Ni, Pd, and metal M), and a coating layer (containing Ni, Pd, and Au). This segmentation allows each layer to have optimized properties that collectively solve the deformation problem while maintaining cost effectiveness.
Solution Approach 2:
The bonding wire uses a composite structure with multiple material layers. The core material provides cost advantages, the intermediate layer provides deformation resistance matching, and the coating layer provides oxidation resistance. This composite approach allows the wire to achieve properties that single materials cannot provide alone.
2Strength
If the concentration of Ni in the coating layer is increased to improve deformation resistance, then deformation resistance is improved, but oxidation and sulfuration resistance is reduced
Solution Approach 1:
Different layers are assigned different compositional qualities suited to their specific functions. The intermediate layer has higher Ni content (15-80 mol %) optimized for deformation resistance matching, while the coating layer has lower Ni content and higher Pd/Au content (Pd: 50-100 mol %) optimized for oxidation and sulfuration resistance. This local optimization resolves the contradiction between deformation resistance and corrosion resistance.
Solution Approach 2:
The intermediate layer acts as a mediator between the core material and the coating layer. It provides the deformation resistance matching needed to prevent loop defects while allowing the coating layer to focus on providing corrosion resistance. The intermediate layer's composition (Ni, Pd, and metal M) serves as a transition that balances mechanical and chemical requirements.
3Device complexity
If a simple two-layer structure (core material and coating layer) is used, then manufacturing complexity is reduced, but defective loops occur due to insufficient absorption of deformation resistance differences
Solution Approach 1:
The bonding wire structure is segmented into three functional layers instead of two. The intermediate layer is inserted between the core material and coating layer to specifically address the deformation resistance mismatch. This additional segmentation, while increasing structural complexity, is necessary to achieve the desired loop quality and prevent defective loops.
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 optimized layer structure effectively reduces the occurrence of snake and sagging loops, improving bonding reliability and usability for high-density mounting, while also enhancing the bonding wire's resistance to deformation and oxidation.
Implementation Method 1
the intermediate layer can absorb the difference in resistance to deformation (deformation resistance) between the core material and the coating layer, to thereby reduce the occurrence of the snake loop as a defective loop
Implementation Method 2
a tip of the wire is first heated and melted by generating arc discharge, so that a ball portion is formed by surface tension
Implementation Method 3
a ball portion is formed by surface tension
Implementation Method 4
the bonding wire is generally bonded by using an ultrasonic and thermo-compression bonding method
Implementation Method 5
the bonding wire is generally bonded by using an ultrasonic and thermo-compression bonding method
Data Source
AI summary
Provided is a bonding wire capable of reducing the occurrence of defective loops. The bonding wire includes: a core material which contains more than 50 mol % of a metal M; an intermediate layer which is formed over the surface of the core material and made of Ni, Pd, the metal M, and unavoidable impurities, and in which the concentration of the Ni is 15 to 80 mol %; and a coating layer formed over the intermediate layer and made of Ni, Pd and unavoidable impurities. The concentration of the Pd in the coating layer is 50 to 100 mol %. The metal M is Cu or Ag, and the concentration of Ni in the coating layer is lower than the concentration of Ni in the intermediate layer.