Flux With Dibasic Acid Mixture for Underfill Compatibility
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing flux residues remain fluid after soldering, hindering the adhesion of underfill to the join object and allowing fine foreign matter to attach, which compromises the strength of the soldering joint.
Innovation Solution
A flux containing a thermosetting resin, a hardening agent, and a long-chain dibasic acid mixture is used, where the hardening agent suppresses the viscosity of the flux residue, preventing fluidity during soldering and attachment of foreign matter, while maintaining wettability and compatibility with underfill.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermosetting resin is added to flux to maintain no-cured state after reflowing for compatibility with underfill, then the resin remains fluid during soldering, but this causes fine foreign matter to attach to the flux residue surface
Solution Approach 1:
The patent changes the chemical composition parameters of the flux by adding specific long-chain dibasic acids (sebacic acid, azelaic acid, or pimelic acid) in controlled amounts (0.1-5% by mass). This compositional parameter change modifies the surface properties of the flux residue to reduce foreign matter attachment while preserving underfill compatibility.
Solution Approach 2:
The patent creates a composite flux formulation combining thermosetting resin with specific long-chain dibasic acids. This composite material approach allows the flux residue to simultaneously achieve compatibility with underfill (through the resin) and resistance to foreign matter attachment (through the dibasic acid components).
2Reliability
If flux residue remains fluid after soldering to maintain compatibility with underfill, then adhesion of underfill is hindered, but cleaning the flux residue requires time and cost
Solution Approach 1:
The patent enables the flux residue to self-regulate its properties after soldering. The long-chain dibasic acids in the flux formulation cause the flux residue to spontaneously form a low-surface-energy state that is both compatible with underfill and resistant to foreign matter, eliminating the need for external cleaning operations.
3Ease of operation
If the resin is not hardened to maintain fluidity during soldering, then the flux residue has viscosity that prevents foreign matter attachment, but this requires suppressing viscosity after soldering
Solution Approach 1:
The patent utilizes temperature-dependent parameter changes. During soldering at high temperatures, the flux maintains fluidity for proper operation. After cooling below the resin's glass transition temperature, the flux residue spontaneously increases in viscosity and hardens, providing stability and preventing foreign matter attachment without requiring additional hardening steps.
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 residue remains compatible with underfill, preventing foreign matter attachment and ensuring strong adhesion without the need for cleaning, thus enhancing the joining strength.
Implementation Method 1
a long-chain dibasic acid mixture in which long-chain dibasic acids having the following compositions (1) through (4) are respectively mixed... the viscosity of the surface of the flux residue is suppressed
Implementation Method 2
a technology has been proposed in which a thermosetting resin contained in the flux can maintain its no-cured state after reflowing so that the resin contained in the flux residue can be compatible with the underfill
Data Source
AI summary
Provided is a flux, flux residue of which keeps a predetermined viscosity during reflow and after a reflow step without hindering wettability of a solder alloy, the flux being compatible with an underfill in an underfill hardening step. The flux contains a thermosetting resin, a hardening agent, an organic acid and a solvent in which the flux contains 3% or more by mass to 8% or less by mass of the resin, 1% or more by mass to 5% or less by mass of the hardening agent to remain within a limit of an additive amount of the resin, 5% or more by mass to 15% or less by mass of the organic acid and a remainder of the solvent.