Chip Type Fuse Barrier Layer Corrosion Resistance
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Solution Overview
Problem
Chip type fuses face corrosion and damage in high humidity and temperature environments due to boric oxide conversion to boric acid and Cu movement, leading to instability and potential failure.
Innovation Solution
Incorporating a barrier layer of a third metal layer, such as Ta or Cr, wider than the first and second metal layers, to prevent corrosion and control Cu movement, enhancing resistance to climatic conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the fuse element is covered by glass layers containing boron to lower melting point, then the fuse element can be fused with small overcurrent at high speed, but in high humidity environments the boric oxide converts to boric acid which melts and corrodes the Cu fuse element pattern
Solution Approach 1:
A barrier layer consisting of a third metal layer (such as Ta or Cr) is introduced between the glass layer and the Cu fuse element pattern. This intermediary layer prevents direct contact between the corrosive boric acid and the Cu pattern, thereby eliminating corrosion while preserving the fast fusing capability provided by the boron-containing glass layer.
2Reliability
If the fuse element pattern is formed by Cu to achieve good conductivity, then electrical performance is improved, but in high temperature environments Cu movement is promoted which may result in upheaval along grain boundaries
Solution Approach 1:
The barrier layer of third metal (Ta or Cr) serves as a stabilizing intermediary that restrains Cu atom migration at high temperatures. This layer prevents Cu upheaval along grain boundaries while maintaining the excellent electrical conductivity of the Cu fuse element pattern during normal operation.
Solution Approach 2:
The fuse element structure is designed as a composite system combining Cu (for conductivity) with a barrier metal layer (for thermal stability). This composite structure leverages the complementary properties of different materials to achieve both high conductivity and structural stability under thermal stress.
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 barrier layer effectively prevents corrosion and Cu particle movement, ensuring stable operation in high humidity and temperature environments, as demonstrated by reduced resistance changes and absence of corrosion in testing.
Implementation Method 1
the barrier layer can control this movement, thus resistance to heat can be improved
Implementation Method 2
because the fuse element includes a layer where a first metal layer and a second metal layer are piled up, and a barrier layer consisting of a third metal layer, which covers the first metal layer and the second metal layer
Data Source
AI summary
A chip type fuse excellent in resistance to climate conditions, where the fuse is able to operate stably under high temperature and high humidity environments. The fuse includes an insulative substrate; an under-glass layer formed on the insulative substrate; a fuse element formed on the under-glass layer; a pair of electrodes formed at both end sides of the fuse element; and an over-glass layer covering at least a fusing section of the fuse element; wherein the fuse element includes a layer where a first metal layer and a second metal layer are piled up, and a barrier layer consisting of a third metal layer, which covers the first metal layer and the second metal layer with a width that is wider than the width of the first metal layer and the second metal layer. The third metal layer overwraps the second metal layer and the first metal layer.