Lead Frame Sensing Zone Thickness for High Current Handling
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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 for integrated current sensors with a conductive piece having a thicker sensing zone and a routing zone, where the sensing zone has additional material to increase thickness, allowing for higher current density and improved heat dissipation without fusing, while maintaining a standard form factor and using industry-standard material thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard thickness lead frame is used, then manufacturing cost is reduced and ease of manufacture is improved, but current carrying capability and reliability under high current are insufficient
Solution Approach 1:
The lead frame has different thicknesses 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 for cost-effective manufacturing. This local differentiation allows the frame to withstand high currents at critical areas without requiring expensive thick construction throughout the entire structure.
2Reliability
If additional material is added to sensing zone, then current density handling and heat dissipation are improved, but device complexity and material usage increase
Solution Approach 1:
Additional conductive material is added only to the sensing zone where high current density and heat generation occur, while the routing zone maintains standard thickness. This localized approach improves thermal handling exactly where needed without unnecessarily complicating the overall structure or wasting material in areas where high current doesn't flow.
Solution Approach 2:
The lead frame is divided into functional zones (sensing zone and routing zone) with different thickness requirements. The sensing zone is segmented as a distinct region requiring enhanced thickness for thermal management, while the routing zone maintains standard construction. This segmentation allows optimized performance in critical areas without overall structural complexity.
3Reliability
If thicker lead frame is used, then current carrying capability is improved, but form factor and device size increase
Solution Approach 1:
The lead frame maintains standard thickness in the routing zone for compact overall dimensions, while locally increasing thickness only in the sensing zone to handle current surges. This allows the device to withstand high current peaks without increasing the overall form factor, as the thicker section is confined to the minimal area necessary for sensing.
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 enables reliable and robust current measurement capable of handling currents over 50 A and surge currents above 20 kA, preventing overheating and thermal damage, while maintaining a compact design and using minimal additional material.
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
a high current density can be provided with a heat generation lower than the necessary to fuse the lead frame
Implementation Method 3
the thicker area extending beyond the sensing zone improves die stability
Data Source
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.