Copper Bonding Wire with Nickel Coating for Oxidation Resistance
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Solution Overview
Problem
Conventional copper bonding wires face issues with oxidation, reduced bonding strength, and deformation during resin sealing due to their susceptibility to corrosion and insufficient strength, making them unsuitable for high-density semiconductor applications.
Innovation Solution
A copper-based bonding wire with a core material and a surface covering layer composed of conductive metals like gold, palladium, platinum, rhodium, silver, and nickel, featuring concentration gradients and intermetallic compounds to enhance formability, bondability, and resistance to oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If copper bonding wire is used to reduce material cost, then cost of material is reduced, but oxidation of wire surface causes bonding strength to drop
Solution Approach 1:
The patent applies composite materials by creating a multi-layered wire structure with a copper core and a nickel surface layer. This composite structure combines the low cost and high conductivity of copper with the oxidation resistance of nickel, resolving the contradiction between material cost and bonding strength. The nickel layer protects the copper core from oxidation while maintaining electrical conductivity.
Solution Approach 2:
The patent applies parameter changes by controlling the thickness of the nickel surface layer (0.01-2 μm) and the composition of the copper core (99.99% purity). By optimizing these parameters, the wire achieves both cost effectiveness and oxidation resistance, maintaining bonding strength while reducing material cost compared to pure gold or pure nickel wires.
2Quantity of substance
If copper bonding wire is used to reduce material cost, then cost of material is reduced, but corrosion of wire surface easily occurs during resin sealing
Solution Approach 1:
The patent uses composite materials with a copper core and nickel surface layer. The nickel layer serves as a protective barrier that prevents corrosion during resin sealing, while the copper core provides cost effectiveness and electrical conductivity. This composite structure resolves the contradiction between material cost and corrosion resistance.
Solution Approach 2:
The nickel surface layer creates an inert protective environment around the copper core, preventing direct contact between the copper and corrosive substances during resin sealing. This protective barrier effect resolves the contradiction between material cost and corrosion resistance.
3Strength
If wire strength is increased to control deformation during resin sealing, then deformation is reduced, but loop control becomes difficult and bonding strength drops
Solution Approach 1:
The patent applies parameter changes by optimizing the nickel layer thickness (0.01-2 μm) to achieve the right balance between wire strength and flexibility. The controlled nickel coating provides sufficient strength to prevent deformation during resin sealing while maintaining loop controllability during bonding operations.
Solution Approach 2:
The patent applies local quality by providing different properties at different locations: the nickel surface layer provides strength and corrosion resistance where needed, while the copper core maintains flexibility and conductivity. This localized property distribution resolves the contradiction between wire strength and loop control.
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 improved ball and wedge bonding capabilities, increased strength, and reduced deformation, enabling the use of copper wires in thinner and thicker applications, including power ICs, while maintaining cost-effectiveness and industrial production feasibility.
Implementation Method 1
The tip of the wire is heated to melt by arc heat input, the surface tension is used to form a ball
Implementation Method 2
the surface tension is used to form a ball
Implementation Method 3
the wire is directly bonded to the external lead side by ultrasonic bonding
Implementation Method 4
the ultrasonic bonding/thermal compression bonding method is the most general
Implementation Method 5
this ball part is pressed against an electrode of the semiconductor device heated to 150 to 300° C. in range for bonding
Data Source
AI summary
The present invention provides a bonding wire improved in formability of a ball part, improved in bondability, good in loop controllability, improved in bonding strength of a wedge connection, securing industrial production ability as well, and mainly comprised of copper which is more inexpensive than gold wire, that is, provides a bonding wire for a semiconductor device comprised of a bonding wire having a core material having copper as its main ingredient and a surface covering layer over the core material and of a conductive metal of a composition different from the core material, characterized in that the surface covering layer has as its main ingredients two or more types of metals selected from gold, palladium, platinum, rhodium, silver, and nickel and the surface covering layer has a concentration gradient of one or both of a main ingredient metal or copper in the wire radial direction.