Copper Particle Paste for Oxidation-Resistant Sintered Bonding
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Solution Overview
Problem
Existing bonding materials for semiconductor devices and electronic components face challenges in providing high thermal conductivity, resistance to reflow treatment, and maintaining reliability under high-temperature and high-current conditions, particularly in applications involving copper nanoparticles and microparticles, which suffer from oxidation and reduced adhesive strength.
Innovation Solution
Copper particles with a specific crystallite diameter ratio (Scu (111)/Scu (220) between 1.4 and 1.2, produced through controlled reduction of cuprous oxide in the presence of a shape stabilizer, ensuring high sinterability and bonding strength, and a paste composition containing these particles for semiconductor and electronic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper nanoparticles and microparticles are used as bonding material, then cost is reduced and migration resistance is improved, but oxidation occurs and adhesive strength decreases
Solution Approach 1:
A core-shell structure is employed where a copper core provides high conductivity and cost-effectiveness, while a protective shell (such as silver, nickel, or other barrier materials) prevents oxidation of the copper surface. This intermediary shell acts as a barrier between the copper and the oxidizing environment, resolving the contradiction between using copper for cost/migration resistance and preventing oxidation.
Solution Approach 2:
The bonding material is designed as a composite particle system combining copper particles with protective coating materials. This composite structure integrates the advantages of copper (low cost, migration resistance, high conductivity) with the oxidation resistance of protective shell materials, thereby resolving the technical contradiction.
2Temperature
If copper particles are used for bonding, then thermal conductivity is improved, but resistance to reflow treatment and high-temperature conditions deteriorates
Solution Approach 1:
The protective shell serves as an intermediary layer that protects the copper core during reflow treatment and high-temperature exposure. The shell material is selected to have high temperature stability and oxidation resistance, allowing the copper core to maintain its thermal conductivity while being protected from degradation during soldering and reflow processes.
Solution Approach 2:
The particle size distribution and crystallite structure of the copper particles are optimized to enhance thermal conductivity while maintaining stability under reflow conditions. The core-shell structure parameters (shell thickness, material composition) are specifically designed to provide protection during high-temperature processing while preserving the thermal performance of the copper core.
3Strength
If adhesive strength is increased to prevent peeling, then bonding reliability is improved, but the material becomes more susceptible to discoloration and electrical resistance changes under heat and light
Solution Approach 1:
The protective shell acts as a mediator that shields the copper core from direct exposure to heat and light during operation. This prevents the copper surface from oxidizing and changing color, while also maintaining stable electrical resistance. The shell material is selected for its stability under thermal and optical stress, thereby preventing degradation while allowing strong bonding.
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 copper particles provide high bonding strength, denseness, and reliability, enabling efficient heat dissipation and maintaining connection reliability under temperature cycles, even without sealing with epoxy, thus enhancing the performance of semiconductor devices and electronic components.
Implementation Method 1
reducing, in the presence of a shape stabilizer, cuprous oxide having a crystallite diameter Scu20 (111) at a Miller index (111) of not less than 70 nm in X-ray diffraction
Implementation Method 2
The material for adhering the heat dissipating member is desired to have higher thermal conductivity
Implementation Method 3
A bonding material containing copper nanoparticles and copper microparticles and/or copper submicroparticles has been proposed
Data Source
AI summary
A copper particle in which a ratio SCu (111)/Scu (220) of a crystallite diameter SCu (111) at a Miller index (111) of copper to a crystallite diameter SCu (220) at a Miller index (220) of copper in X-ray diffraction satisfies the following equation (1) or the following equation (2):SCu(111)/SCu(220)>1.4(1)SCu(111)/SCu(220)<1.2.(2)