Fuse Element Segmentation for Thermal Management

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Solution Overview

Problem

Conventional fuse elements face challenges in achieving high current ratings while maintaining low resistance and compact size, particularly due to heat-related issues during blowout, which can cause melting of connection solders during surface mounting and limit the use of high melting point materials like Pb-containing solders under RoHS regulations.

Innovation Solution

A fuse device incorporating a fuse element with a low thermal conductivity portion for interrupting and a high thermal conductivity portion for cooling, where the interrupting portion is separated from the cooling member, allowing for efficient heat dissipation and reducing temperature rise at the terminal, enabling size reduction and increased current rating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a high melting point metal fuse element is used to prevent melting during reflow, then the fuse element can withstand reflow heat, but the terminal temperature rises to near the melting point and may melt connection solders

Engineering Contradiction:

Improvefuse element temperature resistanceVSAvoidterminal temperature rise affecting connection solder

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The fuse element is divided into two distinct portions: a low thermal conductivity portion at the interrupting section and a high thermal conductivity portion at the terminal section. This segmentation allows the interrupting portion to concentrate heat for effective blowing while the terminal portion efficiently dissipates heat to protect connection solders during reflow processing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different thermal conductivity properties are assigned to different portions of the fuse element. The interrupting portion has low thermal conductivity to concentrate and retain heat for reliable blowout, while the terminal portion has high thermal conductivity to rapidly dissipate heat and prevent damage to connection solders during reflow.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If the length of the fuse element is increased to ensure distance between interrupting portion and electrode terminal, then terminal temperature rise is reduced, but the fuse device size increases

Engineering Contradiction:

Improveterminal temperature riseVSAvoidfuse element length

Core Design Contradiction:

Object-affected harmful factorsVSLength of stationary object

Solution Approach 1:

The thermal conductivity parameter is changed along the length of the fuse element, with the terminal portion having high thermal conductivity to efficiently conduct heat away from the terminal area. This allows for a shorter overall length while still protecting the connection solder from excessive temperature rise.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the cross-sectional area of the fuse element is increased to reduce resistance, then the current rating can be increased, but the heat generation at the interrupting portion increases

Engineering Contradiction:

Improvecurrent ratingVSAvoidheat generation at interrupting portion

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The fuse element features a low thermal conductivity portion at the interrupting section with a smaller cross-sectional area that concentrates heat for reliable blowout, while the terminal portion has a larger cross-sectional area with high thermal conductivity to reduce overall resistance and improve current rating without excessive heat generation at critical points.

Inventive Principle:

Principle #3Local quality

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 solution effectively suppresses temperature increases during overcurrent conditions, enhances rated current capacity, and prevents melting of connection solders, achieving a compact and high-rated fuse device with improved reliability and compliance with environmental regulations.

Implementation Method 1

a low thermal conductivity portion provided with a relatively low thermal conductivity in which an interrupting portion that is blown out by heat is separated from the cooling member

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

a high thermal conductivity portion provided with a relatively high thermal conductivity, provided in a portion other than the interrupting portion, and in contact with or close to the cooling member

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

a fuse element is blown by self-heating when a rate-exceeding current flows therethrough

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS10727019B2Fuse device

Publication Date: 2020.07.28 DEXERIALS CORP

AI summary

A fuse device includes a fuse element and a cooling member, wherein the fuse element includes a low thermal conductivity portion having a relatively low thermal conductivity in which an interrupting portion that is blown out by heat is separated from the cooling member, and a high thermal conductivity portion having a relatively high thermal conductivity, provided in a portion other than the interrupting portion, and in contact with or close to the cooling member.