Solder Paste Flux Composition for QFN Void Suppression
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Solution Overview
Problem
The challenge of suppressing void generation during soldering of miniaturized components like quad flat non-leaded packages (QFN) is significant due to the difficulty in joining the exposed lead frame and electrode terminal to a board using conventional solder pastes.
Innovation Solution
A flux formulation containing rosin, solvents with varying boiling points, a thixotropic agent, heteroalicyclic amine hydroiodide, and an activator, specifically piperidine hydroiodide, is used to create a solder paste that minimizes void formation by optimizing viscosity and solvent ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solder paste is used for soldering miniaturized components like QFN, then the soldering process can be performed, but voids are generated in the joint between the component and board
Solution Approach 1:
The patent changes the chemical composition parameters of the flux by introducing heteroalicyclic amine hydroiodide (0.01-1.5 mass%) in combination with specific solvents having controlled boiling points. This parameter change modifies the flux's chemical reactivity and physical properties to suppress void generation during soldering while maintaining effective oxide removal capability.
Solution Approach 2:
The patent creates a composite flux formulation combining multiple components: rosin, heteroalicyclic amine hydroiodide, solvents with specific boiling points (250°C or higher and 220°C or lower), thixotropic agents, and activators. This composite material approach synergistically combines the functions of each component to achieve both effective fluxing and void suppression.
2Reliability
If the flux composition is optimized to suppress voids, then void generation is reduced, but the formulation complexity increases
Solution Approach 1:
The patent establishes specific parameter ranges for each component to achieve void suppression while managing complexity. The heteroalicyclic amine hydroiodide content is controlled at 0.01-1.5 mass%, solvent boiling points are specified (250°C or higher, 220°C or lower), and the mass ratio of solvents is controlled at 50/50 to 85/15. These defined parameters provide a systematic approach to formulation.
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 proposed flux and solder paste significantly reduce void generation during soldering, ensuring strong and reliable connections by enhancing the soldering process.
Implementation Method 1
the board on which the components are mounted is heated in a heating furnace called a reflow furnace
Implementation Method 2
a flux containing rosin, a solvent, a thixotropic agent, an amine hydroiodide, and an activator
Data Source
AI summary
A flux containing rosin, a solvent, a thixotropic agent, an amine hydroiodide, and an activator (provided that the amine hydroiodide is excluded), in which the amine hydroiodide includes a heteroalicyclic amine hydroiodide, is provided in the present invention. As the heteroalicyclic amine hydroiodide, at least one selected from the group consisting of piperidine hydroiodide and pipecholine hydroiodide is preferable. According to such flux, the generation of voids during soldering can be further suppressed.