Flexible Circuit Board Solder Composition for Microland Spreadability
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Solution Overview
Problem
Existing solder compositions affect insulation coatings on printed wiring boards and lack sufficient solder spreadability, particularly in the context of mounting small components on microlands of a board, which is crucial for miniaturized electronic devices.
Innovation Solution
A solder composition comprising a flux composition with specific dicarboxylic acids and thixotropic agents, balanced to minimize impact on insulation coatings while ensuring excellent solder spreadability, is used in conjunction with a reflow process to mount electronic components on flexible circuit boards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional solder composition is used, then solder spreadability is achieved, but insulation coating is affected and degraded
Solution Approach 1:
The patent modifies the chemical composition parameters of the flux by specifying particular ratios of carboxylic acids (0.1-5 mass%), resins (5-50 mass%), and other additives. By adjusting these compositional parameters, the solder composition achieves both good spreadability and reduced harm to insulation coatings through optimized chemical reactivity and wetting properties
Solution Approach 2:
The solder composition uses a composite flux system combining multiple components: carboxylic acids (including dicarboxylic acids), resins (rosin and synthetic resins), activators, and other additives. This composite approach allows the flux to simultaneously provide wetting action for solder spreadability while the balanced composition minimizes corrosive effects on the insulation coating
2Manufacturing precision
If solder composition is optimized for spreadability, then small components can be mounted on microlands, but insulation coating integrity is compromised
Solution Approach 1:
The patent specifies precise compositional parameters including carboxylic acid content (0.1-5 mass%), resin content (5-50 mass%), and ratios of different acid components. These parameter optimizations enable the solder to spread precisely on microlands for accurate small component mounting while the controlled composition prevents excessive etching or degradation of the insulation coating
Solution Approach 2:
The flux composition is designed to exhibit different chemical behaviors in different contexts: it provides strong wetting and cleaning action locally at the solder joint interface to enable precise microland filling, while the overall balanced composition (particularly the controlled acid content and presence of protective resins) reduces the harmful effects on the surrounding insulation coating
3Ease of operation
If flux composition contains strong activators for solder wetting, then solder spreadability improves, but insulation coating suffers from chemical attack
Solution Approach 1:
The patent carefully controls the activator strength by limiting carboxylic acid content to 0.1-5 mass% and specifying the types of acids used (including dicarboxylic acids with 4-8 carbon atoms). This parameter optimization provides sufficient activating power for solder wetting and spreadability while reducing the chemical aggressiveness that would otherwise attack and degrade the insulation coating
Solution Approach 2:
The flux composition uses resins (rosin and synthetic resins totaling 5-50 mass%) as intermediary substances that facilitate solder wetting and spreading while simultaneously providing a protective effect on the insulation coating. The resins act as a buffer that enables the necessary chemical activity for soldering while mitigating direct harmful attacks on the coating
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 solder composition effectively maintains insulation coating integrity and achieves reliable solder bonding without adverse effects, suitable for flexible circuit boards with inferior solder heat resistance.
Implementation Method 1
the (C) component contains at least one selected from the group consisting of a (C1) amide thixotropic agent having a hydroxy group in one molecule and a (C2) glycerol thixotropic agent having a hydroxy group in one molecule
Implementation Method 2
mounting the electronic component on the flexible wiring board through heating by a reflow furnace under predetermined conditions
Implementation Method 3
the solder composition is unlikely to affect an insulation coating and has excellent solder spreadability
Data Source
AI summary
A solder composition contains: a flux composition containing an (A) rosin resin, a (B) activator, a (C) thixotropic agent, and a (D) solvent; and (E) solder powder, in which the (B) component contains a (B1) dicarboxylic acid having 3 to 8 carbon atoms, the (C) component contains at least one selected from the group consisting of a (C1) amide thixotropic agent having a hydroxy group in one molecule and a (C2) glycerol thixotropic agent having a hydroxy group in one molecule, and the solder composition satisfies a condition represented by Numerical Formula (F1) below provided that a total of contents of the (C1) component and the (C2) component is defined as X and a content of the (B1) component is defined as Y,X/2≤Y≤5X (F1).