Coated Silver Wire for Ultra-Fine Pitch Bonding
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Solution Overview
Problem
Existing bonding wires in electronics and microelectronics applications face challenges in achieving optimal FAB formation, corrosion resistance, and bonding performance, particularly in ultra-fine pitch requirements and second bond window reliability.
Innovation Solution
A coated silver or silver alloy wire with a core composition of pure or doped silver and a double-layer coating of gold and palladium, manufactured through a process involving precursor elongation, coating deposition, and strand annealing, to enhance wire bonding properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pure silver wire is used, then cost is reduced, but bonding performance and reliability deteriorate
Solution Approach 1:
The patent creates a composite wire structure with a pure silver core and a dual-layer coating (inner gold, outer palladium). This composite structure maintains cost-effectiveness through the silver core while achieving superior bonding performance and reliability through the carefully engineered coating layers.
Solution Approach 2:
The patent applies local quality by using pure silver for the core (cost-effective) and applying specific coating layers only on the surface where bonding occurs. The inner gold layer and outer palladium layer are applied locally on the surface to provide the necessary bonding performance without compromising the cost-effectiveness of the bulk silver core.
2Length of moving object
If wire diameter is reduced for ultra-fine pitch, then pitch requirements are met, but bonding performance and reliability worsen
Solution Approach 1:
The patent uses a composite coating structure with an inner gold layer and an outer palladium layer that is specifically optimized for ultra-fine pitch applications. The outer palladium layer (1-10 nm) on the reduced-diameter wire enables proper FAB formation and bonding performance even when the wire diameter is reduced to meet ultra-fine pitch requirements.
Solution Approach 2:
The patent changes the coating parameters (inner gold layer 20-200 nm, outer palladium layer 1-10 nm) to optimize bonding performance for reduced wire diameters. By adjusting the coating thickness and composition parameters, the patent maintains reliable bonding performance even when the wire diameter is reduced for ultra-fine pitch applications.
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 coated wire exhibits improved FAB formation, corrosion resistance, and bonding performance, meeting ultra-fine pitch requirements and ensuring high reliability in wire bonding applications.
Implementation Method 1
a coating layer superimposed on the surface of the core
Implementation Method 2
manufactured through a process involving precursor elongation, coating deposition
Implementation Method 3
manufactured through a process involving precursor elongation, coating deposition, and strand annealing
Data Source
AI summary
A wire comprising a wire core with a surface, the wire core having a coating layer superimposed on its surface, wherein the wire core itself consists of:(a) pure silver consisting of (a1) silver in an amount in the range of from 99.99 to 100 wt.-% and (a2) further components in a total amount of from 0 to 100 wt.-ppmor(b) doped silver consisting of (b1) silver in an amount in the range of from >99.49 to 99.997 wt.-%, (b2) at least one doping element selected from the group consisting of calcium, nickel, platinum, palladium, gold, copper, rhodium and ruthenium in a total amount of from 30 to <5000 wt.-ppm and (b3) further components in a total amount of from 0 to 100 wt.-ppm,or(c) a silver alloy consisting of (c1) silver in an amount in the range of from 89.99 to 99.5 wt.-%, (c2) at least one alloying element selected from the group consisting of nickel, platinum, palladium, gold, copper, rhodium and ruthenium in a total amount in the range of from 0.5 to 10 wt.-% and (c3) further components in a total amount of from 0 to 100 wt.-ppm,or(d) a doped silver alloy consisting of (d1) silver in an amount in the range of from >89.49 to 99.497 wt.-%, (d2) at least one doping element selected from the group consisting of calcium, nickel, platinum, palladium, gold, copper, rhodium and ruthenium in a total amount of from 30 to <5000 wt.-ppm, (d3) at least one alloying element selected from the group consisting of nickel, platinum, palladium, gold, copper, rhodium and ruthenium in a total amount in the range of from 0.5 to 10 wt.-% and (d4) further components in a total amount of from 0 to 100 wt.-ppm,wherein the at least one doping element (d2) is other than the at least one alloying element (d3),wherein the individual amount of any further component is less than 30 wt.-ppm,wherein the individual amount of any doping element is at least 30 wt.-ppm,wherein all amounts in wt.-% and wt.-ppm are based on the total weight of the core, andwherein the coating layer is a double-layer comprised of a 1 to 1000 nm inner layer of gold and an adjacent 0.5 to 100 nm thick outer layer of palladium or a double-layer comprised of a 0.5 to 100 nm thick inner layer of palladium and an adjacent >200 to 1000 nm thick outer layer of gold.