Copper Bonding Wire Grain-Boundary Control for Oxidation Resistance
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Solution Overview
Problem
Copper bonding wires for semiconductor devices suffer from rapid oxidative deterioration when exposed to the atmosphere, leading to a short storage life and increased frequency of replacements, which negatively impacts manufacturing efficiency.
Innovation Solution
The copper bonding wire is engineered with a specific density of crystal grain boundary on its surface, ranging from 0.6 to 1.6 μm/μm², measured by EBSD, and a purity of 99.9% or higher, along with controlled heat treatment and dopant addition to enhance storage life and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If copper bonding wire is exposed to atmosphere for storage, then it is convenient for use, but oxidative deterioration occurs rapidly leading to short storage life
Solution Approach 1:
The invention changes the physical parameters of the copper wire by controlling crystal grain size (10 μm or less) and crystal grain boundary density (0.6 to 1.6 μm/μm²) through specific drawing and heat treatment processes. These parameter changes create a surface structure that naturally resists oxidation, extending storage life from one week to over one month without requiring inert atmosphere packaging.
Solution Approach 2:
The invention creates an inert-like protective environment on the wire surface through controlled oxidation resistance mechanisms. The specific crystal grain boundary structure acts as a barrier, preventing atmospheric oxygen from penetrating and oxidizing the copper surface, effectively creating a protective environment without requiring external inert gas packaging.
2Reliability
If copper bonding wire with high purity is used, then bonding performance is improved, but manufacturing cost increases
Solution Approach 1:
The invention changes the approach from controlling chemical composition (purity) to controlling physical structure (crystal grain parameters). By optimizing crystal grain size and boundary density through mechanical drawing and heat treatment processes, the invention achieves excellent bonding performance with standard purity copper (99.99%), avoiding the need for expensive high-purity materials while maintaining reliable bonding.
3Productivity
If wire length is increased to reduce replacement frequency, then manufacturing efficiency improves, but storage life requirement increases
Solution Approach 1:
The invention performs preliminary action by creating an oxidation-resistant surface structure before the wire is put into storage or use. The controlled crystal grain boundary density and surface treatment are established during manufacturing, providing long-term protection against oxidation that enables extended storage life and allows longer wire lengths to be used without frequent replacements.
Data Source
AI summary
There is provided a copper bonding wire having an improved storage life in the atmosphere. There is specifically provided a copper bonding wire for semiconductor devices characterized in that a density of crystal grain boundary on a surface of the wire is 0.6 (μm/μm2) or more and 1.6 (μm/μm2) or less.