Current Sensor Electrode Pad Arrangement for Migration Suppression
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Solution Overview
Problem
Current sensors using magnetic sensors with electrode pads in moisture absorption states experience reduced detection sensitivity due to electrode migration, which can be exacerbated by high voltages and thermal effects, and the use of special materials for suppressing migration increases costs and process restrictions.
Innovation Solution
The design incorporates a current sensor with a magnetic sensor on a conductor, featuring a Wheatstone bridge circuit with dual magneto-electric conversion units and electrode pads arranged to minimize potential differences and thermal offsets, using standard conductive metals like gold, copper, or aluminum, and encapsulating the sensor in an insulating resin to suppress electrode migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard conductive metals (gold, copper, aluminum) are used for electrode pads, then manufacturing cost and process simplicity are improved, but electrode migration occurs in moisture absorption state reducing detection sensitivity
Solution Approach 1:
An intermediary protective layer (insulating resin or protective coating) is introduced between the electrode pad and the moisture environment. This mediator prevents direct contact between moisture and the standard conductive metal, blocking the migration pathway while maintaining electrical functionality and detection sensitivity.
Solution Approach 2:
The chemical and physical parameters of the electrode pad surface are modified through protective coatings or resin encapsulation. This changes the surface properties to be moisture-resistant while maintaining the bulk electrical conductivity of the standard metal material, preventing migration without requiring special materials.
2Measurement precision
If high drive voltage is applied to the Wheatstone bridge circuit, then detection sensitivity is improved, but thermal effects and electrode migration are exacerbated
Solution Approach 1:
Protective structures (insulating resin encapsulation or protective coatings) are built in advance around the electrode pads before operation. These pre-established protective barriers cushion against the harmful effects of high voltage by preventing moisture ingress and reducing thermal impact, allowing high drive voltages to be applied without causing migration or excessive heating.
3Reliability
If electrode pads are arranged to minimize potential differences, then electrode migration is suppressed, but device complexity increases
Solution Approach 1:
The electrode pads are arranged and connected to create equipotential regions, minimizing potential differences between adjacent pads. By making the potentials equal or nearly equal, electrochemical migration is suppressed without requiring complex multi-layer structures, achieving reliability through simplified potential equalization.
4Reliability
If special materials containing oxygen or nitrogen compounds are used for electrode pads, then electrode migration is suppressed, but manufacturing cost and process restrictions increase
Solution Approach 1:
Instead of modifying the electrode pad material itself with special compounds, an intermediary protective layer (insulating resin or coating) is applied over the standard conductive metal. This mediator provides the migration suppression function without requiring changes to the base material, maintaining ease of manufacture with standard metals while achieving reliability.
Solution Approach 2:
The protective coating or resin encapsulation changes the surface parameters of the electrode pad system, creating a moisture-barrier interface. This allows standard conductive metals to function reliably by modifying the environmental interaction parameters rather than the bulk material composition, avoiding special material requirements.
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 design maintains high detection precision by minimizing electrode migration and thermal offsets, ensuring reliable and cost-effective operation of the current sensor.
Implementation Method 1
detects a magnetic field intensity by inputting a drive voltage from a pair of power supply terminals and obtaining a differential voltage from a pair of output terminals
Implementation Method 2
A magnetic sensor is known that includes a Wheatstone bridge circuit constituted of four resistive sides each including a magneto-resistive element (TMR)
Implementation Method 3
a current sensor is known that detects, by using the magnetic sensor, the amount of current by measuring the magnetic field intensity around a conductor through which a to-be-measured current flows
Data Source
AI summary
A magnetic sensor 60 includes a substrate 61; a plurality of magneto-resistive elements 51 disposed on the substrate, wherein a part of the plurality of magneto-resistive elements is assembled into a Wheatstone bridge circuit to form a magneto-electric conversion unit 62a and another part is assembled into a Wheatstone bridge circuit to form a magneto-electric conversion unit 62b; and a plurality of electrode pads 63#1 to 63#6 disposed on the substrate including a first and a second electrode pad connected to the drive terminal VDD and the ground terminal GND of the magneto-electric conversion units 62a, 62b, respectively, a third and a fourth electrode pad connected to two output terminals Npa1, Npa2 of the magneto-electric conversion unit 62a, respectively, and a fifth and a sixth electrode pad connected to the two output terminals Npb1, Npb2 of the magneto-electric conversion unit 62b, respectively.