Variable-Thickness Lead Frame for High-Current Sensor Reliability
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Solution Overview
Problem
Traditional current sensors are limited in handling high currents and surge currents above 50 A and 20 kA, leading to overheating, thermal damage, and fusing issues, which are not adequately addressed in existing technologies for applications like electric vehicles and energy harvesting systems.
Innovation Solution
A lead frame design with a conductive piece featuring a thicker sensing zone and a routing zone, where the sensing zone has additional material to increase thickness, allowing for higher current density and heat dissipation while maintaining a compact form factor, and using methods like electroplating or additive manufacturing for tailored shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lead frame thickness is increased to handle high currents, then the current carrying capacity and heat dissipation improve, but the device size and material usage increase
Solution Approach 1:
The patent applies local quality by varying the lead frame thickness in different zones: the sensing zone has increased thickness (e.g., 50-200 micrometers) to handle high current density and dissipate heat, while the routing zone maintains standard thickness. This localized thickness variation allows the lead frame to withstand high currents only where necessary, reducing overall material usage and device size while maintaining reliability in critical areas.
2Temperature
If additional material is added to the sensing zone, then the heat dissipation capability improves, but the manufacturing complexity increases
Solution Approach 1:
The patent changes the geometric parameter of the lead frame by creating a non-uniform thickness profile with additional material in the sensing zone. This can be achieved through various manufacturing methods such as selective plating, additive manufacturing, or forming processes, allowing control over the thickness parameter to optimize heat dissipation while managing manufacturing complexity.
3Reliability
If the lead frame is designed with variable thickness, then the current density distribution improves, but the manufacturing precision requirements increase
Solution Approach 1:
The patent implements local quality through variable thickness design where the sensing zone has greater thickness than the routing zone. This localized variation concentrates current-carrying capability where needed, improving current density distribution. The thickness transition is designed to be gradual or well-defined to manage manufacturing precision requirements while achieving the desired electrical performance.
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 enables reliable and robust current measurement capable of withstanding currents over 50 A and surge currents above 20 kA, preventing overheating and fusing, while minimizing material usage and maintaining industry-standard dimensions.
Implementation Method 1
a sensing zone for generating a signal detectable by a current sensing element when current flows through the lead frame
Implementation Method 2
At least the sensing zone includes additional material disposed on the conductive piece so a total thickness of the sensing zone is thicker than the average thickness of said largest area
Data Source
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AI summary
A lead frame for a current sensor is provided. The frame includes a conductive piece with an average thickness, and a sensing zone for generating a signal detectable by a current sensing element when current flows through the lead frame. It also includes a routing zone outside the sensing zone for routing current towards the sensing zone. The routing zone comprises a region with the largest area having a predetermined average thickness. At least the sensing zone includes additional material disposed on the conductive piece so the total thickness of the sensing zone is thicker than the average thickness of said largest area.