Aircraft Ignition Switching Assembly Leakage Control
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Solution Overview
Problem
High voltage switches in aircraft ignition systems face challenges in maintaining high voltage without current leakage, as existing solutions like pulse power thyristor semiconductor devices require mechanical beveling and additional dielectric layers to control leakage.
Innovation Solution
A switching assembly comprising a substrate with a semiconductor device, leads, and potting material, designed to reduce current leakage by using a ceramic substrate, copper pad, switch die with an anode pad, and lead frame, and potting material with low thermal expansion, allowing for automated assembly and low inductance connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical beveling and dielectric layers are applied to control current leakage, then voltage handling capability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent extracts the leakage control function from the semiconductor device itself and relocates it to the PCB board level through guard traces and ground planes. This separates the high-voltage switching function from the leakage control function, allowing each to be optimized independently and reducing overall device complexity.
Solution Approach 2:
The patent introduces an intermediary layer (potting material) between the semiconductor device and the environment that provides both mechanical protection and electrical isolation. This intermediary structure simplifies the device by consolidating multiple protective functions into a single material layer.
2Manufacturing precision
If mechanical beveling and chemical etching are used to control leakage, then manufacturing precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent replaces mechanical beveling processes with standard PCB fabrication techniques (copper plating, trace routing, and grounding). This substitution eliminates complex mechanical machining and chemical etching steps while achieving equivalent or superior leakage control through electrical field management.
Solution Approach 2:
The patent changes the approach from geometric modification (beveling) to electrical parameter control (trace impedance, grounding configuration, and potential distribution). By controlling electrical parameters through PCB design rather than mechanical parameters, manufacturing becomes more standardized and easier to implement.
3Reliability
If polyimide film or dielectric layer is applied to reduce surface leakage, then voltage handling is improved, but device complexity and manufacturing steps increase
Solution Approach 1:
The patent merges the dielectric protection function with the PCB substrate itself. The PCB board, with its ground planes and copper traces, serves simultaneously as the structural support, electrical connection medium, and leakage control mechanism, eliminating the need for separate polyimide film applications.
Solution Approach 2:
The PCB board is designed to perform multiple functions: mechanical support, electrical connection, signal routing, and leakage control through guard traces and ground planes. This multi-functionality reduces device complexity by consolidating what would otherwise require separate components.
Data Source
AI summary
A switching assembly is disclosed for a high voltage aircraft ignition system. The switching assembly includes a ceramic substrate and switch die that includes an anode bonded to an electrical pad on the ceramic substrate. The switch die includes a semiconductor device having a plurality of interleaved gates and cathodes, and includes a ceramic cap having at least one gate pad connected to the gates and at least one cathode pad connected to the cathodes. The switching assembly includes leads connected to the gate pad, the cathode pad, and the electrical pad on the substrate. The switch die and a portion of the leads are potted to form the completed assembly.