Current Sensor Via Layout for High-Voltage Isolation
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Solution Overview
Problem
Integrated current sensors face challenges in achieving high signal-to-noise ratio and high voltage isolation while maintaining proximity to current-carrying conductors, due to the conflicting requirements of sensitivity and safety in high-voltage applications.
Innovation Solution
The solution involves a current sensor design with an integrated circuit and a housing that includes conductive vias for signal rerouting away from the active sensing side, allowing for reliable and efficient signal distribution while maintaining high voltage isolation through the use of redistribution layers and isolation materials like polyimide layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the active CMOS side including the sensing element is positioned facing the current conductor to minimize distance, then the signal-to-noise ratio is improved, but the electric field is increased which reduces voltage isolation breakdown strength
Solution Approach 1:
The patent introduces a third dimension by routing signals through the thickness of the substrate via conductive vias. Instead of keeping all connections on the same plane as the sensing element, the signal path is extended vertically through the substrate to contact pads on the opposite side, thereby increasing the electrical path length and improving voltage isolation while preserving the close proximity of the sensing element to the current conductor.
Solution Approach 2:
The patent introduces intermediate structures including conductive vias filled with conductive material, redistribution layers, and bond pads as mediators between the sensing element and external connections. These intermediaries allow the signal to be transferred from the sensing element through the substrate to contact pads positioned for optimal electrical isolation, resolving the conflict between signal quality and voltage isolation.
2Ease of manufacture
If contact pads are placed on the active CMOS side for signal interchange, then connection to the sensing element is simplified, but accessibility becomes difficult when the active side faces the current conductor
Solution Approach 1:
The patent inverts the conventional arrangement by placing the contact pads on the back side of the substrate opposite to the active CMOS side, rather than on the same side as the sensing element. This inversion allows external connections to be made to the back side where the current conductor is accessible, while the front side maintains its sensing function facing the current-carrying conductor.
Solution Approach 2:
The patent utilizes the vertical dimension of the substrate to relocate contact pads from the front plane to the back plane. By extending signal paths through conductive vias perpendicular to the substrate surface, the contact pads can be positioned on the opposite side, making them accessible for wire bonding or other connection methods while the active side remains optimally positioned for sensing.
3Measurement precision
If the integrated circuit is positioned close to the current carrying conductor for optimal magnetic flux, then sensing sensitivity is improved, but the risk of voltage breakdown increases
Solution Approach 1:
The patent exploits the vertical dimension by routing signal paths through the substrate thickness via conductive vias. This three-dimensional signal routing increases the electrical path length between high-voltage nodes and low-voltage nodes, thereby improving voltage isolation and breakdown strength while allowing the sensing element to remain in close proximity to the current conductor for optimal magnetic flux coupling.
Solution Approach 2:
The patent employs a composite structure combining the CMOS integrated circuit, dielectric substrate material, and conductive via materials. This composite architecture provides both the electrical connection functionality and the voltage isolation properties needed to operate close to high-voltage conductors without risking breakdown, as the dielectric substrate and via structures collectively provide the necessary insulation.
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 design achieves a high signal-to-noise ratio and reliable electrical connections, enabling effective current sensing with improved safety and reduced risk of voltage breakdown, even in high-voltage environments.
Implementation Method 1
For a magnetic field sensing element, such as a Hall-based integrated current sensor, it is important to have a high sensitivity with high signal to noise ratio.
Implementation Method 2
The housing comprises at least one conductive via disposed outside the integrated circuit and connected to the at least one contact pad, for distributing signals from the at least one contact pad through the housing away from the active side of the integrated circuit.
Data Source
AI summary
A current sensor is described comprising an integrated circuit for sensing electric currents comprising an active side, the active side comprising at least one sensing element and at least one contact pad and a housing comprising material embedding the integrated circuit arranged for allowing electric connection to the at least two contact pads of the active side of the integrated circuit. The housing comprises at least one conductive via disposed outside the integrated circuit and connected to the at least one contact pad, for distributing signals from the at least one contact pad through the housing away from the active side of the integrated circuit.