Fuse Counter-Bore Body Solder Connection Reliability

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Solution Overview

Problem

Existing fuses face inconsistency and unreliability in wire-to-solder connections due to the lack of a consistent location for solder reflow during assembly, leading to inferior electrical connections.

Innovation Solution

The implementation of counter-bores in the hollow body of the fuse provides additional space for solder to form a more reliable connection between the fusible element and the end caps, ensuring a consistent and robust electrical link.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional hollow tubular body is used without counter-bores, then the fuse structure is simple, but the wire-to-solder connection consistency and reliability are poor

Engineering Contradiction:
Improvewire-to-solder connection reliabilityVSAvoidhollow body structure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The hollow body is modified with counter-bores at specific locations where solder connections are needed. This local modification provides concentrated space for solder reflow at the wire-to-solder connection areas, improving connection reliability without requiring a complete redesign of the entire hollow body structure.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The counter-bores are pre-formed in the hollow body during manufacturing, creating predetermined spaces for solder accumulation before the actual soldering process. This preliminary preparation ensures that solder has a consistent location to reflow and form reliable connections, eliminating the inconsistency of traditional designs.

Inventive Principle:
Principle #10Preliminary action

2Manufacturing precision

If additional space is provided for solder reflow, then the electrical connection consistency improves, but the hollow body manufacturing complexity increases

Engineering Contradiction:
Improvesolder connection consistencyVSAvoidhollow body manufacturing
Core Design Contradiction:
Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The hollow body design incorporates counter-bores with specific dimensional parameters (depth, diameter, location) that are optimized to provide adequate space for solder reflow. By carefully controlling these parameters, the design achieves consistent solder connections while maintaining manufacturability through standard machining or molding processes.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP2577703B1Fuse with counter-bore body
Publication Date: 2016.08.10 LITTELFUSE INC
  • EP2577703B1 patent drawingFigure 1
  • EP2577703B1 patent drawingFigure 2A~2C
  • EP2577703B1 patent drawingFigure 3

AI summary

An improved fuse having one or more counter bores in an interior wall of a hollow tube used as the fuse housing. The fuse includes a fusible element disposed within a cavity defined by the interior wall. The fusible element is electrically connected to first and second end caps via solder. The first and second end caps are attached to respective ends of the hollow tube. The one or more counter bores provide more space for the solder to cover the fusible element resulting in a more reliable electrical connection.