Oxidized Solder Particles for Short-Circuit-Resistant Bonding
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Solution Overview
Problem
Commercially available solder particles have a wide particle size distribution and are soft, making it difficult to form a uniform insulating film, which leads to short-circuiting and reduction in insulating properties during thermocompression bonding.
Innovation Solution
Solder particles with an oxidized film thickness of 3 nm or greater and surface roughness of 10 nm or greater, produced using a forced airflow classification process in an oxygen-containing atmosphere, to prevent short-circuiting and maintain insulating properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a thin oxidized film (2.5-6 nm) is formed on solder particles to inhibit temporal viscosity increase, then paste stability is improved, but the film is insufficient to prevent short-circuiting and solder particle agglutination during thermocompression bonding
Solution Approach 1:
The patent changes the thickness parameter of the oxidized film from the conventional 2.5-6 nm to a thicker range of 7-20 nm. This parameter change provides sufficient insulating strength to prevent short-circuiting and solder particle agglutination during thermocompression bonding, while still maintaining paste stability and printability.
2Ease of manufacture
If currently commercially-available solder particles with wide particle size distribution are used, then production cost is reduced, but coarse particles cause short-circuiting in portions without pressure application
Solution Approach 1:
The patent applies local quality by forming an oxidized film with specific thickness (7-20 nm) and surface roughness (Ra 5-50 nm) on the surface of each solder particle. This localized modification provides insulating protection at the particle surface level, preventing short-circuiting caused by coarse particles while maintaining the overall particle size distribution for cost-effective manufacturing.
3Quantity of substance
If solder particles are used as conductive particles, then electrical conductivity is improved, but solder particles melt and auto-agglutinate during thermocompression bonding causing short-circuiting
Solution Approach 1:
The patent creates a composite structure by forming an oxidized film layer on the surface of the solder particles. This composite material combines the electrical conductivity of the solder core with the insulating properties of the oxidized film shell, enabling the particles to conduct electricity while preventing unwanted agglutination and short-circuiting during thermocompression bonding.
4Reliability
If an oxidized film is formed on solder particles to prevent short-circuiting, then insulating property is improved, but the film may increase paste viscosity and affect printability
Solution Approach 1:
The patent optimizes the oxidized film thickness parameter to a specific range of 7-20 nm with surface roughness Ra of 5-50 nm. This parameter optimization provides sufficient insulating strength to prevent short-circuiting while maintaining appropriate paste flow characteristics for good printability, avoiding the viscosity problems associated with excessively thick films.
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 process effectively prevents short-circuiting and maintains insulating properties by ensuring uniform film formation and surface roughening, reducing the risk of solder particle melting and agglutination between wiring patterns.
Implementation Method 1
a proposed solder powder for a solder paste is obtained by forming an oxidized film having an average thickness of from 2.5 nm through 6 nm on the surface of solder particles
Implementation Method 2
produced by a forced airflow classification process in an oxygen-containing atmosphere
Data Source
AI summary
Solder particles containing an oxidized film on the surface thereof, wherein the average film thickness of the oxidized film is 3 nm or greater, and the average surface roughness Ra of the solder particles is 10 nm or greater are provided.