Electroconductive Paste Bonding Metal Terminals Thermal Shock
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Solution Overview
Problem
Existing electroconductive pastes fail to ensure reliable bonding of metal terminals to external electrodes on electronic components, resulting in insufficient fixing strength and crack generation due to inadequate paste distribution and expansion coefficient mismatch, especially under thermal shock.
Innovation Solution
An electroconductive paste containing spherical Cu powder, flat Cu powder, glass frit, and a spherical inorganic powder with a ceramic material, which maintains a sufficient amount between the metal terminal and external electrode, acting as a spacer to absorb expansion differences and prevent cracking, with specific particle size and proportion ratios to ensure strong bonding and thermal shock resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electroconductive paste is used for bonding metal terminals, then the paste can be applied to external electrodes, but the paste spreads out during bonding and loses the ability to ensure sufficient amount between terminal and electrode, resulting in insufficient fixing strength
Solution Approach 1:
The patent changes the particle size parameters of the inorganic filler, specifically using a spherical inorganic powder with 30 μm or more average particle size. This parameter change prevents paste spread during bonding while maintaining sufficient paste amount between terminal and electrode, resolving the contradiction between bonding reliability and fixing strength
Solution Approach 2:
The patent creates a composite paste formulation combining spherical Cu powder, flat Cu powder, glass frit, and spherical inorganic powder with specific particle sizes. This composite material structure prevents paste spread and ensures sufficient bonding material retention, simultaneously improving both bonding reliability and fixing strength
2Reliability
If conventional electroconductive paste is used for bonding metal terminals, then the paste can be applied to external electrodes, but the baked electrode cannot sufficiently absorb the difference in linear coefficient of expansion, resulting in crack generation under thermal shock
Solution Approach 1:
The patent introduces a spherical inorganic powder with 30 μm or more average particle size that remains unmelted during heat treatment. This parameter change enables the baked electrode to absorb expansion differences through the unmelted inorganic powder, preventing crack generation under thermal shock and improving thermal shock resistance
Solution Approach 2:
The unmelted spherical inorganic powder acts as an intermediary material between the metal terminal and the external electrode. It mediates the thermal expansion differences between materials, absorbing stress and preventing crack propagation, thereby improving thermal shock resistance and preventing crack generation
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 paste achieves strong and reliable bonding of metal terminals to external electrodes, preventing crack generation and ensuring high thermal shock resistance by maintaining a sufficient amount of baked electrode between the terminal and electrode, while absorbing expansion differences.
Implementation Method 1
absorb expansion differences
Implementation Method 2
baking the electroconductive paste
Data Source
AI summary
An electroconductive paste that includes an inorganic filler which contains a spherical Cu powder of 3 μm or less in average particle size; a flat Cu powder of 3 or more in aspect ratio and 10 μm or more in average particle size; glass frit; and a spherical inorganic powder of 30 μm or more in average particle size, the spherical inorganic powder including an inorganic material that is not melted in a heat treatment step for baking. The spherical inorganic powder is contained in a proportion of 10 to 35 parts by volume with respect to 100 parts by volume of a mixture of the spherical Cu powder and the flat Cu powder. In addition, the proportion of the flat Cu powder falls within the range of 10 to 50% by volume with respect to the total amount of the spherical Cu powder and flat Cu powder.