Resistor with Central Electrodes for Creepage Distance
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Solution Overview
Problem
Conventional mold resistors face challenges in securing a sufficient creepage distance of insulation between conductor sections and a metal case, particularly in high-voltage and large-current environments, which is essential for in-vehicle applications but difficult to achieve without compromising miniaturization or increasing the size of the resistor.
Innovation Solution
A resistor design featuring paired electrodes on an insulating substrate with a resistive element and an insulating exterior, where the electrodes are formed on areas other than the ends, and externally connecting electric conductors with convex junctions that ensure a predetermined creepage distance of insulation, using a flexible harness wire structure and a protective film to cover the upper and side surfaces, except for the junctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tip part sections of metal terminals are joined to electrodes at the end parts of the substrate, then electrical connection is achieved, but creepage distance of insulation between conductor sections and metal case cannot be secured
Solution Approach 1:
The electrode arrangement transitions from end-part positioning to central positioning on the substrate, utilizing the internal dimensional space of the substrate rather than the boundary regions. This dimensional repositioning creates sufficient creepage distance from the metal case while maintaining electrical connection functionality through the substrate's thickness dimension.
Solution Approach 2:
The insulating substrate acts as an intermediary barrier between the conductor sections (electrodes and metal terminals) and the metal case. By positioning electrodes on the substrate rather than at its ends, the substrate provides both electrical insulation and sufficient creepage distance, mediating between the need for electrical connection and insulation requirements.
2Reliability
If the area of the insulating substrate is made larger to secure insulation, then creepage distance is improved, but miniaturization of the resistor becomes impossible
Solution Approach 1:
The solution utilizes the vertical dimension (thickness) of the substrate and the three-dimensional space within the mold resin to achieve sufficient creepage distance. Instead of increasing the substrate's planar area, the design positions electrodes centrally and allows the mold resin to provide insulation coverage, achieving insulation requirements without increasing the resistor's footprint or volume.
Solution Approach 2:
Different regions of the resistor structure are assigned different functional qualities: the central substrate area hosts electrodes for electrical connection, while the surrounding mold resin provides insulation. This local differentiation allows the resistor to meet insulation requirements through strategic material placement rather than uniform size increase.
3Ease of manufacture
If electrodes are positioned at the end parts of the substrate for easy connection, then manufacturing is simplified, but sufficient resistive element area cannot be secured
Solution Approach 1:
The electrode connection approach moves from two-dimensional end-part attachment to three-dimensional central positioning with vertical connection paths through the substrate. Externally connecting electric conductors pass through the mold resin to reach centrally positioned electrodes, providing both sufficient resistive element area and reliable electrical connection through this spatial reconfiguration.
Data Source
AI summary
A resistor has a structure including a resistor substrate that has paired electrodes and a resistive element formed on an insulating substrate, an insulating exterior material that covers at least the upper and the side surface of the resistor substrate, and harness electric wires that have one end parts connected to the respective electrodes, pass through the exterior material, and extend outside. The paired electrodes are formed on areas other than the end parts of the insulating substrate, and junctions of the end parts of the harness electric wires and the paired electrodes are at positions where creepage distance of insulation from the junctions to the bottom ends of the insulating substrate is a predetermined distance or longer. Such structure provides the resistor having a secured creepage distance of insulation between the conductor parts of the resistor and the metal case in which the resistor is installed.