Low-Residue Solder Paste Composition for Void-Free Bonding
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Solution Overview
Problem
Conventional solder paste compositions for printed circuit boards face challenges in achieving strong bonding due to metal oxide films, leading to voids, low thermal conductivity, and reduced reliability, especially when rosin and quaternary ammonium halide salts are used, which can increase manufacturing costs and complexity.
Innovation Solution
A solder paste composition comprising a metal powder and an organic mixture with a solvent, thixotropic agent, and an organic acid having a boiling point lower than the metal powder's melting point, which penetrates and removes metal oxide films uniformly, avoiding flux residues and voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rosin and quaternary ammonium halide salt are used to remove metal oxide film, then soldering capability is improved, but flux residues and voids are generated reducing reliability
Solution Approach 1:
The patent extracts and removes the harmful quaternary ammonium halide salt component from the solder paste formulation, replacing it with carboxylic acid and its salt. This extraction eliminates the generation of metal halide salts and flux residues while maintaining the ability to remove metal oxide films, thereby improving reliability without harmful by-products
Solution Approach 2:
The patent changes the chemical parameters of the flux system by substituting quaternary ammonium halide salts with carboxylic acids and their salts. This parameter change alters the reaction mechanism from generating metal halide salts to generating soluble carboxylate salts, which can be easily removed without forming voids or harmful residues
2Reliability
If reducing gas is used to remove metal oxide film during soldering, then center of solder joint can be treated, but water vapor is generated causing voids
Solution Approach 1:
The patent converts the harmful effect of carboxylic acid (potential corrosion) into a beneficial effect by using its controlled decomposition during heating. The carboxylic acid decomposes to form water and carbon dioxide, which escape as gases without forming voids, while the resulting carboxylate salt provides continuous fluxing action without the harmful effects of traditional fluxes
3Reliability
If complex pre-treatment process is applied to metal powders to prevent oxidation, then solder bonding is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies preliminary action by incorporating the carboxylic acid and its salt directly into the solder paste formulation during manufacturing. This pre-incorporation eliminates the need for complex post-manufacturing pre-treatment processes, as the flux components are already positioned to remove oxide films during the soldering process itself, thereby reducing manufacturing complexity and cost
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 solution achieves improved soldering strength, reduced porosity, and simplified manufacturing processes by ensuring complete vaporization of the organic acid, enhancing the reliability and cost-effectiveness of solder joints.
Implementation Method 1
the organic acid has a boiling point lower than a melting point of the metal powder... which penetrates and removes metal oxide films uniformly
Implementation Method 2
ensuring complete vaporization of the organic acid... the organic acid having a boiling point lower than the metal powder's melting point
Implementation Method 3
A solder paste composition comprising a metal powder and an organic mixture... melting the metal powder of the solder paste composition to solder the soldering target to the substrate
Data Source
Figure 1~2
Figure 3~4
AI summary
Provided are a solder paste composition and a soldering method using the same. The solder paste composition comprises a metal powder in an amount of 100 parts by weight and an organic mixture in an amount from 3 to 18 parts by weight; wherein the organic mixture comprises a solvent, a thixotropic agent and an organic acid; wherein the organic acid has a boiling point lower than a melting point of the metal powder. The soldering method using the solder paste composition comprises the steps as follows: providing the soldering paste composition between a substrate and a soldering target to form a complex structure; placing the complex structure in a chamber and introducing an acid gas to the chamber; and melting the metal powder of the soldering paste composition to solder the soldering target to the substrate.