Flux Composition for Multi-Reflow Solder Void Prevention
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Solution Overview
Problem
Existing fluxes do not exhibit favorable wettability with electrodes subjected to various surface treatments and can form voids during multiple reflow processes, affecting the reliability of soldered components.
Innovation Solution
A flux composition comprising rosin, rosin amine, organic sulfonic acid, thixotropic agent, and solvent, with specific mass ratios, to enhance wettability and prevent void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flux containing p-toluenesulfonic acid as activator is used, then wettability is exhibited, but favorable wettability among electrodes subjected to various surface treatments cannot be achieved
Solution Approach 1:
The flux uses a composite activator system combining rosin amine (5-30%) with organic sulfonic acid (0.2-10%), creating a multi-functional chemical system that can interact with different electrode surface treatments (Ni-Au plating, Cu-OSP treatment, Sn plating) effectively, achieving universal wettability across various surface conditions
Solution Approach 2:
The flux optimizes the ratio of rosin amine to organic sulfonic acid (3.33-10:1), which controls the chemical reactivity and wettability characteristics. This parameter optimization enables the flux to maintain effective wettability across multiple reflow cycles while being compatible with different electrode surface treatments
2Productivity
If multiple times of reflow are performed, then components can be mounted on both sides or multilayer boards, but voids form in joint portions
Solution Approach 1:
The flux contains rosin amine and organic sulfonic acid in optimized ratios that prevent oxide formation and maintain wetting capability before subsequent reflow cycles. This preliminary protective action ensures that even after multiple reheating cycles, the solder joints remain void-free and reliable
Solution Approach 2:
The flux formulation maintains its wettability and protective functions continuously through multiple reflow cycles. The rosin amine and organic sulfonic acid work synergistically to prevent oxidation and ensure consistent solder flow, eliminating void formation even after repeated heating and cooling cycles
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 flux improves wettability with various surface-treated electrodes and prevents void formation even after multiple reflow cycles, ensuring reliable soldering.
Implementation Method 1
A flux has an effect of chemically removing metal oxides present on the metal surface of an object to be joined, which is a soldering target, and on a solder
Implementation Method 2
a thixotropic agent
Data Source
Figure 1
Figure 2A~2C
AI summary
The present invention uses a flux which contains a rosin, a rosin amine; one or more types of organic sulfonic acid selected from the group consisting of an alkane sulfonic acid, an alkanol sulfonic acid, and an aromatic sulfonic acid, a thixotropic agent, and a solvent, wherein: the rosin content is 5-50 mass%, inclusive, of the total amount (100 mass%) of the flux, the rosin content is 5-30 mass%, inclusive, of the total amount (100 mass%) of the flux, the organic sulfonic acid content is 0.2-10 mass%, inclusive, of the total amount (100 mass%) of the flux, and the proportion (mass ratio) of the rosin amine content to the organic sulfonic acid content is 3.33-10, inclusive.