Chip Fuse Thermal Insulation for Precision Fusing
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Solution Overview
Problem
Existing methods for manufacturing chip fuses, particularly in thick-film technology, face challenges in achieving precision and cost-effectiveness due to the use of expensive substrates with low thermal conductivity and the need for additional costly processing steps like laser cutting.
Innovation Solution
A thermally insulating intermediate layer, such as a low-melting-point inorganic glass paste or organic layer, is applied between a cost-effective Al2O3 ceramic substrate and the fusible metallic conductor, utilizing thin-film technology and photolithographic structuring to define the fusing characteristic precisely while allowing the use of standard ceramics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If expensive substrates with low thermal conductivity are used to achieve precise fusing characteristics, then manufacturing precision is improved, but manufacturing cost increases
Solution Approach 1:
The substrate is functionally segmented into two distinct parts: a cost-effective high thermal conductivity substrate (Al2O3 ceramic) and a localized low thermal conductivity region (glass glaze layer) positioned only at the fuse element location. This segmentation allows the expensive thermal insulation property to be applied only where needed for precise fusing, while the rest of the substrate uses inexpensive material.
Solution Approach 2:
The glass glaze layer with low thermal conductivity is applied locally only at the position of the fuse element rather than covering the entire substrate. This local quality approach ensures that thermal insulation is provided precisely where heat dissipation would interfere with fusing characteristics, while maintaining cost-effectiveness by using inexpensive substrate material elsewhere.
2Ease of manufacture
If screen-printing method is used to apply fusible element layers, then ease of manufacture is improved, but manufacturing precision deteriorates
Solution Approach 1:
The glass glaze layer acts as an intermediary between the substrate and the fusible element layers. This intermediate layer provides a suitable surface that combines the advantages of screen-printing (ease of manufacture) with improved geometry precision, as the paste materials can be applied with better geometric control on the glaze surface compared to direct application on the ceramic substrate.
3Manufacturing precision
If additional laser cutting methods are used to process fusible element, then manufacturing precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The complex laser cutting process is extracted and replaced by a simpler photolithographic structuring method. The fuse element geometry is defined through photolithographic patterns applied to the sputtered metal layers, eliminating the need for additional laser cutting steps while achieving the required precision through the photolithographic process itself.
4Temperature
If high Al2O3 proportion ceramic substrates are used, then thermal conductivity is improved, but manufacturing cost increases due to glazing requirements
Solution Approach 1:
The substrate surface is segmented into glazed and unglazed regions. The glass glaze layer is applied only at the fuse element position where thermal insulation is needed, while the rest of the high Al2O3 substrate remains unglazed. This segmentation allows the substrate to maintain high thermal conductivity overall while providing localized thermal insulation where required for precise fusing characteristics.
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 approach enables the cost-effective and precise manufacturing of high-precision fuses that effectively protect electronic components from fault currents, using standard ceramics and minimizing thermal conduction to define the melting point of the fuse accurately.
Implementation Method 1
A thermally insulating intermediate layer, such as a low-melting-point inorganic glass paste or organic layer, is applied between a cost-effective Al2O3 ceramic substrate and the fusible metallic conductor
Implementation Method 2
The maximum possible current strength which may flow through this conductor without fusing it is determined by the geometry and the cross-section of the conductor. If this value is exceeded, the electrical conductor is fused because of the heat resulting therein due to its electrical resistance
Implementation Method 3
Especially high precision of the cut-off and/or fusing characteristic is achieved in this case through photolithographic structuring of sputtered layers
Data Source
AI summary
In order to produce a cost-effective fuse in chip design, which is applied to a carrier substrate made of a Al2O3 ceramic having a high thermal conductivity, and which is provided with a fusible metallic conductor and a cover layer, in which the melting point of the metallic conductor may be defined reliably, it is suggested that an intermediate layer having low thermal conductivity be positioned between the carrier substrate and the metallic conductor, the intermediate layer being formed by a low-melting-point inorganic glass paste applied in the screen-printing method or an organic intermediate layer applied in island printing. Furthermore, a method for manufacturing the fuse is specified.