Palladium-Coated Silver Wire Corrosion Resistance
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Solution Overview
Problem
In semiconductor devices, noble metal-coated silver wires for ball bonding face corrosion issues at the bonding interface with aluminum pads, leading to energization failures under high temperature and high humidity conditions, which existing technologies have not adequately addressed.
Innovation Solution
A noble metal-coated silver wire with a palladium layer and sulfur group elements, where the palladium content is between 0.01 and 5.0 mass % and the sulfur group element content is between 0.1 and 100 mass ppm, forming a palladium distribution layer that suppresses corrosion and maintains bonding reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a palladium coating layer is formed on silver wire to prevent sulfurization, then surface corrosion resistance is improved, but bonding reliability deteriorates in high temperature and high humidity environments
Solution Approach 1:
The invention changes the chemical composition parameters of the coating layer by introducing sulfur group elements (S, Se, Te) in specific amounts (0.01-5.0 mass %) alongside palladium. This parameter modification transforms the coating from a simple Pd layer that melts during bonding to a composite layer where sulfur group elements suppress Pd melting and promote uniform distribution, thereby maintaining both corrosion resistance and bonding reliability in harsh environments.
Solution Approach 2:
The invention creates a composite coating layer combining palladium with sulfur group elements (S, Se, or Te). This composite structure leverages Pd's corrosion resistance while the sulfur group elements prevent Pd from melting during ball bonding and promote uniform distribution. The synergistic combination resolves the contradiction between corrosion protection and bonding reliability in high temperature and humidity conditions.
2Object-affected harmful factors
If the palladium coating layer is made thicker to improve corrosion resistance, then surface protection is improved, but manufacturing cost increases
Solution Approach 1:
The invention optimizes the coating composition by incorporating sulfur group elements at specific concentrations (0.01-5.0 mass %) rather than using thick pure Pd coatings. This parameter change allows achieving adequate corrosion resistance with thinner, more cost-effective coatings while the sulfur group elements provide additional functional benefits of preventing Pd melting and ensuring uniform distribution during bonding processes.
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 effectively prevents corrosion at the bonding interface, ensuring reliable electrical conductivity and extending the lifespan of semiconductor devices even under severe conditions.
Implementation Method 1
the wire contains at least one sulfur group element, the noble metal coating layer comprises at least one palladium layer, the total palladium content relative to the entire wire is 0.01 mass % or more and 5.0 mass % or less, and the total sulfur group element content relative to the entire wire is 0.1 mass ppm or more and 100 mass ppm or less
Implementation Method 2
pure silver wires had a problem that their surfaces were sulfurized when they were left in the air for a long period of time, and silver alloy wires had a problem that electric resistivity increased when pure silver was alloyed with palladium or gold. Accordingly, in order to solve the above problems, a coated silver bonding wire obtained by coating the surface of a silver wire with a platinum group metal such as palladium was proposed. The coated silver bonding wire solved the problem of sulfurization of the surface of the bonding wire
Implementation Method 3
one end of the wire is melted by electric discharge, becomes spherical due to surface tension, and is solidified. The solidified ball is called a free air ball (FAB)
Implementation Method 4
The solidified ball is called a free air ball (FAB) and is connected to an electrode of a semiconductor chip by an ultrasonic thermocompression bonding method
Data Source
AI summary
A noble metal-coated silver bonding wire for ball bonding wire includes a noble metal coating layer on a core material made of pure silver or a silver alloy, wherein the wire contains at least one sulfur group element, the noble metal coating layer includes at least one palladium layer, the total palladium content relative to the entire wire is not less than 0.01 mass % and not more than 5.0 mass %, and the total sulfur group element content relative to the entire wire is not less than 0.1 mass ppm and not more than 100 mass ppm.