Au Bonding Wire with Be, Ca, La Alloy Composition
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Solution Overview
Problem
Conventional Au bonding wires face a trade-off between tensile strength and ball diameter dispersion, leading to short-circuits and wire bonding issues in high-density semiconductor packages, where finer wires require higher tensile strength and narrower ball diameters to prevent contact with neighboring wires.
Innovation Solution
The development of Au bonding wires with specific alloy compositions, including Be, Ca, La, and additional elements like Ce, Eu, Mg, Si, Ga, Sb, Sn, Bi, and Y, which maintain high tensile strength and achieve superior roundness of the squashed ball even at diameters less than 23 μm, ensuring stability and preventing wire flow during molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the diameter of bonding wire is reduced to achieve higher density packaging, then the pitch between pins and bonding pad size can be reduced, but the tensile strength decreases and wire flow increases causing bonding reliability issues
Solution Approach 1:
The patent changes the chemical composition parameters of the Au bonding wire by adding specific elements (Be: 3-15 mass ppm, Ca: 3-40 mass ppm, La: 3-20 mass ppm, and optionally Ce: 3-20 mass ppm) to pure gold. This parameter change resolves the contradiction by maintaining high tensile strength (≥23 kg/mm²) even when wire diameter is reduced to 23 μm or less, preventing wire flow during molding while enabling higher density packaging.
2Strength
If the strength of bonding wire is increased to prevent wire flow, then tensile strength improves, but dispersion of diameter of squashed ball becomes broader causing contact between neighboring balls
Solution Approach 1:
The patent optimizes the composition parameters by adding specific rare earth elements (La, Ce) and alkaline earth elements (Be, Ca) in controlled amounts. This parameter optimization achieves both high tensile strength (≥23 kg/mm²) and superior ball roundness (0.95-1.05), thereby reducing ball diameter dispersion and preventing contact between neighboring balls while maintaining wire strength.
3Quantity of substance
If finer bonding wire is used to achieve narrower pitch, then packaging density increases, but absolute stiffness of wire decreases making it more susceptible to wire flow and short-circuits
Solution Approach 1:
The patent creates a composite material by adding multiple elements (Be, Ca, La, and optionally Ce) to pure gold in specific proportions. This composite structure provides both high tensile strength and adequate stiffness even for fine wires (23 μm or less diameter), preventing wire flow during molding and short-circuits while enabling higher packaging density through narrower pitch.
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 solution provides Au bonding wires with fracture stress exceeding 23 kg/mm² and roundness of 0.95-1.05, preventing short-circuits and ensuring reliable bonding in high-density semiconductor packages by balancing wire stiffness and ball diameter dispersion.
Implementation Method 1
heating and melting of the wire tip is carried out with arc heating, forming a ball by surface tension
Implementation Method 2
heating and melting of the wire tip is carried out with arc heating
Implementation Method 3
ultrasonic thermo-compressed bonding method
Implementation Method 4
heating and melting of the wire tip is carried out with arc heating, forming a ball by surface tension, then the ball is stuck by compressed bonding to electrode of semiconductor, which is heated in the range of 150-300 degrees in Celsius
Data Source
AI summary
An Au bonding wire for semiconductor device, comprising a wire-shaped Au alloy material consisting of: 3-15 mass ppm of Be, 3-40 mass ppm of Ca, 3-20 mass ppm of La, 3-20 mass ppm of at least one functional element selected from the group of Ce, Eu, Mg, and Si, and the remainder of Au, wherein the diameter of said Au alloy bonding wire is less than 23 microns, wherein said bonding wire has improved roundness of compressed bonded ball and improved fracture stress.