Ag Alloy Bonding Wire Composition for Stable Ag-Al Ball Bonds
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Solution Overview
Problem
Bonding wires used in on-vehicle memory devices face challenges in extending high-temperature life, reducing chip damage during ball bonding, and achieving good ball bonding strength, as they tend to form Ag-Al intermetallic compounds that lead to separation and inadequate bonding due to the diffusion of Ag and Al at high temperatures.
Innovation Solution
An Ag alloy bonding wire containing In and Ga for a total of 110 at ppm or more and less than 500 at ppm, and Pd and Pt for a total of 150 at ppm or more and less than 12,000 at ppm, which forms an alloy layer at the Ag-Al bonding interface, suppressing the growth of Ag-Al intermetallic compounds and controlling the hardness and deformability of the ball for improved bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ag bonding wire is used for on-vehicle memory devices, then cost is reduced compared to Au wire, but high-temperature life is insufficient due to formation of Ag-Al intermetallic compounds causing separation
Solution Approach 1:
The patent changes the chemical composition parameters of the bonding wire by adding specific alloying elements (In: 1-50 at ppm, Ga: 1-50 at ppm, Pd: 1-100 at ppm, Pt: 1-100 at ppm) to pure Ag. These parameter changes modify the metallurgical behavior at the bonding interface, suppressing intermetallic compound formation and enabling the wire to withstand high-temperature storage conditions (220°C for 600 hours) without ball separation.
Solution Approach 2:
The patent creates a composite material system by combining Ag with multiple alloying elements (In, Ga, Pd, Pt) in specific concentrations. This composite structure provides synergistic effects where the alloying elements work together to suppress Ag-Al intermetallic compound formation while maintaining electrical conductivity and bonding performance, resolving the contradiction between cost reduction and high-temperature reliability.
2Productivity
If ball bonding is performed on very thin memory chips (20 um or less), then storage capacity is increased through multilayering, but chip damage occurs due to insufficient bonding strength
Solution Approach 1:
The patent modifies the mechanical properties of the ball by controlling the concentration of alloying elements (particularly In and Ga at 1-50 at ppm each). These parameter changes optimize the hardness and deformability of the ball, enabling it to maintain sufficient bonding strength on very thin memory chips (20 um or less) while preventing chip damage during the bonding process.
3Reliability
If alloying elements are added to Ag wire to suppress intermetallic compound growth, then high-temperature life is extended, but ball formability and bonding characteristics may deteriorate
Solution Approach 1:
The patent precisely controls the concentration parameters of alloying elements within narrow ranges (In: 1-50 at ppm, Ga: 1-50 at ppm, Pd: 1-100 at ppm, Pt: 1-100 at ppm). These controlled parameter changes are sufficient to suppress intermetallic compound growth at high temperatures while maintaining the ductility and formability required for proper ball formation and bonding characteristics.
Solution Approach 2:
The patent applies local quality by having alloying elements concentrate at the bonding interface rather than uniformly distributing throughout the wire. This localized distribution suppresses intermetallic compound formation at the critical bonding area while minimizing the impact on overall ball formability and wire characteristics.
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 Ag alloy bonding wire effectively extends high-temperature life, reduces chip damage, and enhances ball bonding strength by suppressing the growth of Ag-Al intermetallic compounds and optimizing the mechanical properties of the ball, thereby meeting the performance requirements for on-vehicle memory devices.
Implementation Method 1
forming an alloy layer at the Ag-Al bonding interface, suppressing the growth of Ag-Al intermetallic compounds
Implementation Method 2
a wire tip is heated and melted by heat input by arc heating to form a ball
Implementation Method 3
a method of bonding a bonding wire is generally a thermosonic bonding process
Data Source
AI summary
An object of the present invention is to provide an Ag alloy bonding wire for a semiconductor device capable of extending the high-temperature life of a wire, reducing chip damage during ball bonding, and improving characteristics such as ball bonding strength in applications of on-vehicle memory devices. The Ag alloy bonding wire for a semiconductor device according to the present invention contains one or more of In and Ga for a total of 110 at ppm or more and less than 500 at ppm, and one or more of Pd and Pt for a total of 150 at ppm or more and less than 12,000 at ppm, and a balance being made up of Ag and unavoidable impurities.