Fuse Element with Matched Thermal Expansion Substrate
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Solution Overview
Problem
Conventional fuse elements on printed circuit boards face issues with temperature stability and insulation strength due to mismatched thermal expansion coefficients between the substrate material and conductor materials, leading to delamination and decomposition at high temperatures, and difficulties in achieving high-rated current and fast-acting characteristics.
Innovation Solution
A fuse element is developed using a high-temperature-stable, electrically insulating printed circuit board substrate material with a thermal expansion coefficient matching that of the metal or metal alloy fuse, featuring a multilayer structure with a cover layer and strategically placed voids for enhanced heat dissipation, and optionally filled with insulating materials to prevent inflammation and arc quenching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional printed circuit board substrate material (epoxy resin-reinforced glass fabric) is used, then the fuse can be manufactured using standard PCB processes, but the substrate loses strength and undergoes delamination and decomposition at temperatures above 200°C, resulting in insufficient insulation resistance
Solution Approach 1:
The patent employs a composite substrate structure consisting of a ceramic layer (Al2O3 or AlN) combined with a metal layer (stainless steel or Invar). This composite material provides both high-temperature stability and mechanical strength, resolving the contradiction between manufacturability and high-temperature reliability. The ceramic-metal composite maintains its properties above 200°C while allowing standard PCB manufacturing processes to be used.
Solution Approach 2:
The patent changes the material parameters of the substrate by selecting ceramics with specific thermal expansion coefficients (7-9 ppm/K for Al2O3, 4-6 ppm/K for AlN) and metals with matching coefficients (7-13 ppm/K for stainless steel, 5-6 ppm/K for Invar). This parameter matching prevents thermal stress and delamination at high temperatures, maintaining both manufacturability and insulation resistance.
2Temperature
If Al2O3 ceramic is used as the fuse basis, then high temperature stability is achieved, but the mismatched thermal expansion coefficient (below 8 ppm/K) causes stresses that crack the ceramic and damage the fuse
Solution Approach 1:
The patent explicitly addresses thermal expansion by selecting ceramic materials (Al2O3 with 7-9 ppm/K, AlN with 4-6 ppm/K) and metal materials (stainless steel with 7-13 ppm/K, Invar with 5-6 ppm/K) whose thermal expansion coefficients are closely matched. This minimizes thermal stress during temperature changes, preventing ceramic cracking and maintaining structural integrity while achieving high temperature stability.
Solution Approach 2:
The patent uses a composite structure of ceramic and metal layers where the metal layer compensates for thermal stress. The closely matched thermal expansion coefficients of the composite materials allow the ceramic to maintain its high-temperature stability without cracking, as the metal layer accommodates minor expansion differences.
3Loss of energy
If thermally highly conductive ceramic is used, then heat dissipation is improved, but fuse elements with low rated currents and fast-acting characteristic can be achieved only with difficulty
Solution Approach 1:
The patent applies local quality by creating a dual-layer structure where the ceramic layer provides high thermal conductivity for heat dissipation, while the metal layer provides controlled thermal resistance. This local differentiation allows the fuse to dissipate heat efficiently overall while maintaining the thermal characteristics needed for fast-acting protection at low rated currents.
Solution Approach 2:
The patent changes thermal parameters by selecting specific ceramic materials (Al2O3 with thermal conductivity of 20-30 W/(m·K), AlN with 150-200 W/(m·K)) and metal materials (stainless steel with 15-25 W/(m·K), Invar with 10-20 W/(m·K)). This parameter optimization allows the fuse to achieve both good heat dissipation and fast-acting characteristics for low rated currents.
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 ensures stable insulation strength and improved current-time behavior at high temperatures, reduces material and production costs, and allows for effective heat dissipation and arc suppression, enhancing the reliability of electric and electronic circuits.
Implementation Method 1
a great deal of heat energy flows from the actual fuse element into the thermally highly conductive ceramic
Implementation Method 2
the printed circuit board substrate material on which the fuse is provided comprises an at least high-temperature-stable, electrically insulating material, and at least its coefficient of thermal expansion varies essentially corresponding with the coefficient of thermal expansion of the metal or metal alloy from which the fuse is made
Data Source
AI summary
A fuse element, in particular suited for use in electric and/or electronic circuits constructed by multilayer technology, including a printed circuit board substrate material, which is usable particularly in the multilayer technology and is coated with a metal or metal alloy from which the fuse is generated by means of photolithographic and/or printing image-producing techniques and ensuing etching or engraving processes, is proposed. The fuse is distinguished in that the printed circuit board substrate material, on which the fuse can be provided, includes at least a high-temperature-stable, electrically insulating material, with a coefficient of thermal expansion that varies essentially analogously to the coefficient of thermal expansion of the metal or metal alloy from which the fuse is made.