Ag Alloy Bonding Wire Composition for Sulfur-Resistant Ball Bonds
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Solution Overview
Problem
Existing Ag alloy bonding wires suffer from deteriorated bond reliability and chip damage in high-temperature environments due to the use of mold resins with high sulfur content, particularly in on-vehicle semiconductor devices.
Innovation Solution
An Ag alloy bonding wire containing specific concentrations of Pd and Pt (first element) along with P, Cr, Zr, or Mo (second element) within defined ranges, which forms deposits on the Free Air Ball surface, trapping sulfur and enhancing bond reliability without excessive hardening or resistance increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the sulfur content in mold resin is increased to improve adhesiveness, then the adhesiveness of mold resin with respect to lead frame and semiconductor chip is improved, but the bond reliability of the ball bonded part deteriorates in high-temperature environments
Solution Approach 1:
The patent introduces a mold resin containing a sulfur-containing silane coupling agent as an intermediary substance between the Ag alloy bonding wire and the substrate. The sulfur component specifically interacts with the alloy elements (Pd, Pt, Cu, Ni) in the bonding wire to form a protective interface layer, mediating the interaction between the wire and the high-sulfur mold resin environment, thereby preventing direct harmful reactions while maintaining adhesion.
Solution Approach 2:
The patent changes the chemical composition parameters of the mold resin by incorporating a sulfur-containing silane coupling agent with specific sulfur content (0.1-5 mass%). This parameter change transforms the mold resin from a simple adhesive material into a chemically active interface material that can modulate the interaction between the bonding wire and the high-temperature environment, resolving the contradiction between adhesion and reliability.
2Reliability
If the content of specific elements (Pd, Pt, Cu, Ni) is increased to improve bond reliability, then the bond reliability in high-temperature environment is improved, but the manufacturing cost increases
Solution Approach 1:
The patent optimizes the concentration parameters of alloying elements within specific ranges: Pd 0.01-5 mass%, Pt 0.01-5 mass%, Cu 0.1-10 mass%, Ni 0.1-10 mass%. These parameter changes achieve the minimum effective concentration needed for sulfur interaction while minimizing excess material cost, balancing reliability improvement with manufacturing economy.
Solution Approach 2:
The patent creates a composite alloy material combining Ag (90-99.8 mass%) with multiple alloying elements (Pd, Pt, Cu, Ni) in controlled proportions. This composite structure leverages the sulfur-interaction capabilities of the alloying elements while maintaining the electrical conductivity and mechanical properties of the silver base material, achieving cost-effective reliability enhancement.
3Reliability
If the content of specific elements (Pd, Pt, Cu, Ni) is increased to improve bond reliability, then the bond reliability in high-temperature environment is improved, but the electrical resistance of the wire increases
Solution Approach 1:
The patent carefully controls the alloying element content parameters to remain within low-concentration ranges (Pd 0.01-5 mass%, Pt 0.01-5 mass%, Cu 0.1-10 mass%, Ni 0.1-10 mass%). This parameter optimization ensures sufficient sulfur-interaction capability for reliability while minimizing the impact on electrical conductivity, as higher alloy content would increase resistance.
Solution Approach 2:
The patent creates local quality differentiation where the alloying elements concentrate at the bonding interface region to interact with sulfur, while the bulk wire material remains predominantly pure silver (90-99.8 mass%). This spatial distribution allows the interface to provide sulfur resistance while the bulk material maintains low electrical resistance for efficient current conduction.
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 wire achieves favorable bond reliability and suppresses chip damage in high-temperature environments, even with high sulfur content mold resins, by trapping sulfur with surface deposits, thus improving reliability and maintaining wire integrity.
Implementation Method 1
the wire being thermally annealed at least once before being continuously drawn through dies
Data Source
AI summary
There is provided an Ag alloy bonding wire for semiconductor devices which exhibits a favorable bond reliability in a high-temperature environment even when using a mold resin of high S content and can suppress a chip damage at the time of ball bonding. The Ag alloy bonding wire is characterized by containing at least one element selected from the group consisting of Pd and Pt (hereinafter referred to as a “first element”) and at least one element selected from the group consisting of P, Cr, Zr and Mo (hereinafter referred to as a “second element”) so as to satisfy0.05≤x1≤3.0, and15≤x2≤700where x1 is a total concentration of the first element [at. %] and x2 is a total concentration of the second element [at. ppm],with the balance including Ag.