Copper Micro-Particle Bonding for Reliable Metal Joints
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Solution Overview
Problem
Conventional metal bonding methods using copper, such as soldering or high-temperature pressure bonding, result in poor electrical characteristics and connection reliability due to the formation of high-resistance Cu—Sn alloy layers or require expensive vacuum equipment.
Innovation Solution
A method involving a disperse solution of copper micro-particles in an oxide-eluting solution, where copper micro-particles are dispersed into a solution containing copper oxide, filling the gap between bonding portions and applying energy to bond them at a reduced distance, allowing for copper bonding without high temperatures or large-scale equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder bonding is used to connect copper members, then electrical connection is achieved, but Cu-Sn alloy layers form at the bonded interface causing high electric resistance and poor ductility
Solution Approach 1:
The invention extracts and removes the harmful Cu-Sn alloy layer formation by eliminating solder from the bonding process. Instead, it uses a solution that dissolves the oxide layer and promotes direct copper-to-copper bonding, thereby taking out the intermediate solder material that causes high resistance and poor ductility.
Solution Approach 2:
The invention introduces a solution as an intermediary substance that facilitates direct copper bonding. This solution contains agents that dissolve copper oxide and promote copper diffusion, acting as a mediator that enables reliable electrical connection without forming harmful alloy layers, thus improving both connection reliability and electrical characteristics.
2Strength
If high-temperature pressure bonding is used to bond copper members, then bonding strength is improved, but the wiring substrate or semiconductor chip may be damaged due to heat or pressure application
Solution Approach 1:
The invention changes the bonding parameters from high temperature and high pressure to low temperature and low pressure conditions. By using a chemical solution to facilitate bonding, the process operates under milder parameters that achieve sufficient bonding strength without damaging the substrate or chip.
Solution Approach 2:
The invention replaces the mechanical pressure-based bonding system with a chemical solution-based bonding system. Instead of relying on high mechanical pressure to achieve bonding, the solution chemically facilitates copper diffusion and bonding at low pressure, thereby avoiding substrate or chip damage while maintaining bonding strength.
3Reliability
If vacuum activation method is used to bond copper members, then bonding reliability is improved, but large-scale vacuum equipment is required leading to increased costs
Solution Approach 1:
The invention replaces expensive, complex vacuum equipment with a simple, disposable chemical solution. The solution can be applied in ambient conditions using conventional equipment, and after use, the process completes without requiring costly vacuum systems, thereby reducing device complexity and costs while maintaining bonding reliability.
Solution Approach 2:
The chemical solution serves as an intermediary that enables copper bonding in ambient conditions without requiring vacuum equipment. This intermediary substance facilitates oxide removal and copper diffusion, allowing reliable bonding to be achieved with simple equipment rather than complex vacuum systems.
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
This method achieves reliable copper bonding with improved electrical characteristics and reduced equipment costs by forming a copper bonded portion with high orientation and stability, capable of bonding at lower temperatures without the need for vacuum apparatuses.
Implementation Method 1
a disperse solution obtained by dispersing copper micro-particles into a solution for oxide elution into which an oxide with copper oxide as a principal component can be eluted
Implementation Method 2
filling a gap between a first bonding portion formed of a first metal material and a second bonding portion formed of a second metal material with the disperse solution; further reducing a distance between the first bonding portion and the second bonding portion
Implementation Method 3
applying energy to the gap between the first bonding portion and the second bonding portion in the state in which the gap between the first bonding portion and the second bonding portion is reduced, so as to bond the first bonding portion and the second bonding portion
Data Source
AI summary
The gap between first and second bonding portions is filled with a disperse solution obtained by dispersing copper micro-particles into a solution for copper oxide elution, so as to elute copper oxide configured as the outermost layer of the first bonding portion and copper oxide configured as the outermost layer of the second bonding portion, and copper oxide formed on the surface of each copper micro-particle. Pressure is applied to the first and second bonding portions using a press machine so as to raise the pressure of the disperse solution. At the same time, heat is applied under a relatively low temperature condition of 200° C. to 300° C., so as to remove the components contained in the disperse solution except for copper, thereby depositing copper. Thus, a first base portion and a second base portion are bonded via a copper bonded portion containing copper derived from the copper micro-particles.