Current Sensor Leadframe with Oblique Conductor Sections
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Solution Overview
Problem
Current sensors face challenges in achieving high sensitivity, immunity to temperature variations and stress, high dielectric strength, and low production costs, as existing technologies often require complex processing and higher costs due to the need for precise alignment and etching of leadframes and semiconductor chips.
Innovation Solution
A method involving a leadframe with obliquely oriented current conductor sections, a semiconductor chip with integrated Hall sensors and magnetic field concentrators, and wire bonding, packaged in a standard plastic housing with a ceramics or glass isolator, which simplifies production and enhances sensitivity and stress immunity without the need for etching or complex alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wire bonding technology is used to connect semiconductor chip and leadframe, then manufacturing precision requirements are reduced and production costs are lowered, but the device complexity increases compared to flip chip arrangement
Solution Approach 1:
The patent replaces the mechanical flip chip mounting process with wire bonding technology, substituting a complex mechanical alignment and bonding system with a more forgiving wire-based connection system that tolerates misalignment and requires less precise positioning of the semiconductor chip relative to the leadframe
Solution Approach 2:
The patent introduces wire bonds as an intermediary element between the semiconductor chip and leadframe, allowing electrical connection without requiring direct surface mounting, thereby decoupling the precision requirements of chip placement from the final electrical connection quality
2Measurement precision
If the current conductor is positioned closer to the Hall sensors, then sensitivity increases, but the dielectric strength between current conductor and electronics decreases
Solution Approach 1:
The patent resolves the contradiction by transitioning from a two-dimensional planar arrangement to a three-dimensional configuration, positioning the current conductor in a lowered position beneath the semiconductor chip while maintaining adequate vertical clearance, thus achieving both close proximity for sensitivity and sufficient separation for dielectric strength
Solution Approach 2:
The patent introduces an isolator as an intermediary component between the current conductor and the semiconductor chip, providing dielectric separation that maintains high dielectric strength while allowing the current conductor to be positioned in optimal proximity to the Hall sensors for maximum sensitivity
3Ease of manufacture
If standard plastic housing and simple leadframe are used, then production costs are reduced, but the immunity to temperature variations and stress decreases
Solution Approach 1:
The patent applies a stress buffer layer beforehand to cushion and compensate for thermal expansion and mechanical stress effects, protecting the semiconductor chip and magnetic field concentrators from temperature variations and stress while maintaining compatibility with standard plastic housing and simple leadframe structures
Solution Approach 2:
The patent employs composite material structures, including the stress buffer layer combining different material properties, and the integration of ceramics or glass isolator with plastic housing, to achieve enhanced thermal and mechanical stability while maintaining cost-effectiveness through the use of standard materials
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 solution achieves high sensitivity, immunity to external magnetic fields and mechanical stress, and maintains low production costs by using standard materials and processing techniques, ensuring dielectric strength of 2 to 4 kV and efficient current measurement.
Implementation Method 1
a semiconductor chip... comprising four Hall sensors, each Hall sensor integrated at an active surface of the semiconductor chip and providing a Hall output signal
Implementation Method 2
magnetic field concentrators arranged on the active surface of the semiconductor chip
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
A method of making a current sensor comprises providing a leadframe (1) having a current conductor portion (7) comprising two sections (8, 9) shaped such that a current to be measured flows in the two sections (8, 9) in directions oriented obliquely or oppositely with respect to each other, deforming the leadframe (1) to lower the current conductor portion (7), mounting an isolator (2) on the current conductor portion (7), mounting a semiconductor chip (3) having a thickness of at least 0.2 mm and comprising two magnetic field sensors composed of four Hall sensors (13) and magnetic field concentrators (16) on the isolator (2), connecting the semiconductor chip (3) and sensor terminal leads (6) by wire bonds (17), packaging the semiconductor chip (3) and parts of the leadframe (1) in a plastic housing (4), and cutting a frame (10) of the leadframe (1) from current terminal leads (5) and the sensor terminal leads (6).