Fusible Lead Frame Terminal for Overheat Protection

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Solution Overview

Problem

Existing protection methods for security-critical components in electronic circuits, such as power semiconductors and capacitors, fail to effectively prevent overheating and damage due to defects, as conventional fuses and PTCs are either ineffective or too costly for decentralized protection, and temperature sensors cannot interrupt current flow in malfunctioning switches.

Innovation Solution

An electric component with a lead frame featuring a fusible material that melts at a predetermined temperature, integrated into the current feeding terminal, which interrupts the current path upon overheating, allowing for decentralized and cost-effective protection of individual components without the need for external assistance or bulky designs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional fuses are used for protection, then cost-effective protection is achieved, but decentralized protection of individual components is not effective

Engineering Contradiction:

Improveprotection effectivenessVSAvoidprotection structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the fuse function directly into the lead frame structure by making the current feeding terminal itself fusible. This integration merges the protective function with the electrical connection structure, enabling decentralized protection of individual components without requiring separate fuse elements or complex protection circuits.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The lead frame terminal serves dual functions: it provides electrical connection and simultaneously acts as the protective element. The fusible material in the terminal automatically interrupts current flow when overheating occurs, making the component self-protecting without requiring external protection mechanisms.

Inventive Principle:

Principle #25Self-service

2Difficulty of detecting and measuring

If temperature sensors are used to monitor overheating, then temperature detection is achieved, but current interruption capability is lost in malfunctioning switches

Engineering Contradiction:

Improvetemperature monitoringVSAvoidcurrent interruption capability

Core Design Contradiction:

Difficulty of detecting and measuringVSReliability

Solution Approach 1:

The patent replaces electronic temperature sensing with a thermal-mechanical response. The fusible material directly responds to temperature through phase change (melting), which mechanically interrupts the electrical connection. This substitution eliminates the need for separate temperature sensors and control circuits while maintaining reliable current interruption.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The protective mechanism utilizes the phase transition of the fusible material from solid to liquid at a predetermined melting temperature. This phase change provides a direct, reliable method for detecting overheating and automatically interrupting current flow without requiring electronic sensing or control.

Inventive Principle:

Principle #36Phase transitions

3Reliability

If external protection devices are added to components, then protection coverage is improved, but device size and cost increase

Engineering Contradiction:

Improveprotection coverageVSAvoidcomponent size

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

The protective function is merged into the existing lead frame structure, eliminating the need for separate protection devices. The current feeding terminal itself becomes the protective element through the use of fusible material, thereby providing protection without increasing component size or requiring additional external devices.

Inventive Principle:

Principle #5Merging (Combining)

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

This solution enables efficient and cost-effective protection of security-critical components by integrating a fusible material into the component's lead frame, allowing for thermal coupling with switches and consumers, thereby interrupting current flow at a critical temperature, preventing overheating and damage without requiring additional sensors or bulky designs.

Implementation Method 1

a first terminal (166a, 176a) comprising in part a fusible material (81) melting at a predetermined melting temperature

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

the fusible material (81) is removed from the first terminal (166a, 176a) in the molten state

Methodology Applied

Scientific EffectPhase change (melting): Melting

Implementation Method 3

a second terminal (166b, 176b) comprising a material having a melting temperature which is higher than that of the fusible material

Methodology Applied

Scientific EffectMelting point difference: Melting

Data Source

PatentUS7504925B2Electric component with a protected current feeding terminal

Publication Date: 2009.03.17 INFINEON TECHNOLOGIES AG

AI summary

An electric device generates a predetermined amount of heat in the event of a malfunction. The electric device is protected from overheating in that it is arranged, with a fuse in a circuit, such that the fuse and the electric device are thermally coupled to one another, so that the generation of the amount of heat by the electric device causes a fusible material in the fuse to melt. In this manner, the current terminal path of the electric device is interrupted.