Water-Containing Formic Acid Soldering for Low-Void Joints
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Solution Overview
Problem
The conventional solder paste soldering process faces issues such as low reliability of solder joints, generation of organic solvent waste, and leftover organic acid metal salts, while the use of pure formic acid as a source for formic acid soldering is costly and environmentally unfriendly.
Innovation Solution
A processing method of formic acid soldering that utilizes water-containing formic acid as the source of formic acid vapor, creating a water-containing formic acid atmosphere for soldering, which reduces costs and environmental impact while maintaining high soldering performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pure formic acid is used as the source of formic acid vapor, then the soldering performance is improved, but the cost is increased
Solution Approach 1:
The patent changes the purity parameter of formic acid from 100% to a range of 40-95%, demonstrating that high purity is not necessary for achieving good soldering results. This parameter change reduces material cost while maintaining effective soldering performance through formic acid vapor generation.
Solution Approach 2:
The patent employs lower purity, cheaper formic acid as a disposable consumable that can be directly vaporized for soldering. The formic acid source (liquid or solid) is consumed during the process to generate vapor, eliminating the need for expensive high-purity reagents while achieving the same functional outcome.
2Productivity
If conventional solder paste soldering process is used, then the soldering process is complete, but organic solvent waste is generated and washing is required
Solution Approach 1:
The patent replaces the mechanical/chemical flux system in conventional soldering with a thermal vaporization system. Formic acid is vaporized and applied thermally to remove oxides, eliminating the need for liquid flux and subsequent washing processes, thereby preventing organic solvent waste generation.
Solution Approach 2:
The patent converts the potentially harmful concentrated formic acid into a beneficial process by controlling its vaporization. The vapor form allows for precise application and complete evaporation, transforming a corrosive liquid into a clean gaseous reagent that leaves no residue requiring washing.
3Productivity
If conventional solder paste soldering process is used, then the soldering process is complete, but the reliability of solder joint is reduced
Solution Approach 1:
The patent changes the chemical environment parameter from conventional flux-based atmosphere to formic acid vapor atmosphere. This parameter change creates optimal conditions for oxide removal and solder wetting, resulting in improved solder joint reliability with fewer voids and better metallurgical bonding.
Solution Approach 2:
The patent creates a controlled formic acid vapor atmosphere that acts as a protective environment during soldering. This atmosphere prevents oxidation of solder and substrate surfaces while facilitating clean metal-solder bonding, similar to how inert gases protect against oxidation in other metallurgical processes.
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 method achieves a high reliability of solder joints with low void rates, eliminates the need for washing, and reduces waste treatment costs, while providing a more environmentally friendly approach compared to using pure formic acid.
Implementation Method 1
providing formic acid vapor to react with the oxides on the surface of the soldering metal object and form formic acid metal salts
Implementation Method 2
further pyrolysis the formic acid metal salts in a high temperature so as to reduce the metals
Implementation Method 3
a water-containing formic acid vapor extracted from a formic acid source is introduced to the soldering object
Data Source
AI summary
A processing method of formic acid soldering includes providing a solder, performing a formic acid providing step, performing a soldering step and performing a cooling step. The solder is disposed at a soldering object. In the formic acid providing step, a water-containing formic acid vapor extracted from a formic acid source is introduced to a soldering object so as to form a water-containing formic acid atmosphere surrounding the soldering object. In the soldering step, the solder and the soldering object are soldered in the water-containing formic acid atmosphere at a soldering temperature so as to form a soldered object with high temperature. In the cooling step, the soldered object with high temperature is cooled by a cooling method so as to form a soldered object. A range of a moisture content of the formic acid source is greater than or equal to 0.1 wt % and less than 15 wt %.