Internal-Flux Solder Preform for Consistent Reflow Coating
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Solution Overview
Problem
Conventional solder tubes with external flux coatings face issues such as difficulty in achieving uniform coating, inconsistent inner diameter dimensions, potential for flux-related defects, and production downtime due to flux dust and powder formation during handling and shipping.
Innovation Solution
Solder preforms with an internal flux core containing a thermochromic indicator, allowing the flux to flow out during reflow soldering through openings or perforations, eliminating the need for external coatings and reducing flux-related defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external flux coating is applied to the solder tube, then flux is provided to facilitate soldering, but uniform coating is difficult to achieve and inner diameter dimensions become inconsistent
Solution Approach 1:
Instead of applying flux externally to the solder tube surface, the patent inverts the approach by embedding the flux within the solder alloy matrix itself. The flux is incorporated during the manufacturing process, ensuring uniform distribution without affecting dimensional tolerances. This internal flux delivery system eliminates the coating application step while maintaining reliable flux availability during soldering.
Solution Approach 2:
The flux is pre-incorporated into the solder alloy during manufacturing, before the soldering process occurs. This preliminary action ensures that the flux is already uniformly distributed within the solder material, eliminating the need for post-manufacturing coating operations and ensuring consistent dimensional properties are maintained throughout production.
2Reliability
If an external flux coating is applied to the solder tube, then flux is provided for soldering, but flux-related defects and production downtime occur due to flux dust and powder formation
Solution Approach 1:
The patent extracts the flux from the external surface environment and relocates it internally within the solder alloy matrix. This extraction eliminates the source of flux dust and powder formation that occurs during handling and shipping of externally coated tubes. The flux remains contained within the solid solder material until the melting process releases it naturally.
Solution Approach 2:
The patent converts the potential harm of flux exposure (dust and powder formation) into a benefit by incorporating the flux internally. The flux that would otherwise create contamination issues on the surface is now contained within the solder alloy, where it serves its intended purpose without creating harmful byproducts during storage and handling.
3Reliability
If an internal flux core with thermochromic indicator is used, then flux delivery is improved and visual temperature verification is provided, but the preform structure becomes more complex
Solution Approach 1:
The patent merges multiple functions into a single integrated structure. The flux delivery system and thermochromic temperature indicator are combined within the same internal core structure of the solder preform. This consolidation provides both reliable flux delivery and visual temperature verification without requiring separate external components, thereby limiting the increase in overall structural complexity.
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 internal flux core design enables higher flux content, consistent dimensions, and prevents flux-related issues, ensuring better solder joint formation and reducing production downtime.
Implementation Method 1
a thermochromic dye may be added to the exterior flux coating. During reflow soldering that melts the flux, when a correct reflow temperature is reached, the thermochromic dye will change color (e.g., become colorless).
Data Source
AI summary
A solder preform in the shape of a solder tube or washer includes: a cylindrically shaped solder alloy body including an inner surface, an outer surface, a first end, and a second end, the second end interlocking with the first end, and the first end and the second end cut along an entire height of the cylindrically shaped solder alloy body; and a flux core embedded in the cylindrically shaped solder alloy body between the inner surface and the outer surface, the flux core including a thermochromic indicator. During reflow soldering, the flux core including the thermochromic indicator is configured to flow out of the first end and the second end to coat a substrate that is soldered.