Copper Bonding Paste With Phosphate Ester for Oxidation Control
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Solution Overview
Problem
Copper is prone to oxidation, leading to a decrease in the strength of the bonding layer when used as a sintered material, especially in non-reducing atmospheres.
Innovation Solution
A bonding paste comprising copper particles, a solvent, and a phosphate ester additive, where the additive content is between 0.5% to 3.0% by mass, is used to form a bonding layer that suppresses oxidation and maintains strength during the bonding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If copper paste is used as bonding material, then material cost is reduced, but oxidation occurs causing decrease in bonding layer strength
Solution Approach 1:
A protective film forming additive is introduced as an intermediary substance that forms a protective film on the copper particle surface. This additive acts as a mediator between the copper particles and the oxidation environment, preventing direct contact between oxygen and copper surfaces during storage and heating processes, thereby maintaining bonding layer strength while using cost-effective copper material
Solution Approach 2:
The protective film created by the additive establishes an inert environment around each copper particle surface. This film barrier effectively creates a localized inert atmosphere that prevents oxidation without requiring the entire bonding process to occur in a costly reducing atmosphere, thus resolving the contradiction between material cost and bonding strength
2Device complexity
If copper paste is used without protective atmosphere, then process complexity is reduced, but oxidation occurs during heating causing strength decrease
Solution Approach 1:
The bonding paste formulation includes a protective film forming additive that automatically forms a protective film on copper particle surfaces during storage and heating. This self-protecting mechanism eliminates the need for external protective measures such as reducing atmospheres or inert gas environments, thereby maintaining bonding strength while simplifying the overall process
Solution Approach 2:
The protective film is formed preliminarily on the copper particle surfaces before the bonding process begins. This pre-formed protective layer is already in place during storage and the heating process, preventing oxidation from occurring in the first place and eliminating the need for complex atmospheric control during 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 use of the bonding paste effectively prevents the decrease in strength of the bonding layer even in non-reducing atmospheres, ensuring stable bonding and heat resistance.
Implementation Method 1
copper is easily oxidized, which may cause the decrease in a strength of the bonding layer composed of a sintered copper
Implementation Method 2
The silver paste can be sintered under a relatively low temperature condition
Data Source
AI summary
To suppress a decrease of strength, a bonding paste includes a copper particle, a solvent, and an additive composed of a phosphate ester. In the bonding paste, a content of the additive is in the range of 0.5% to 3.0% by mass both inclusive relative to a total of the bonding paste.