Silicon Carbide TVS Mesa Structure for High Temperature Voltage Suppression
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Solution Overview
Problem
Silicon-based transient voltage suppressors are unsuitable for high temperature applications above 150°C due to increased current leakage and thermal strain, making them inadequate for protecting electronics in aviation and power generation systems exposed to high ambient temperatures and voltage surges.
Innovation Solution
A silicon carbide (SiC) transient voltage suppressor assembly with a mesa structure and glass housing, featuring a punch-through design and electrodes with matched thermal expansion coefficients, allowing reliable operation up to 300°C and effective voltage suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon-based TVS devices are used for voltage suppression, then voltage spike protection is provided, but current leakage increases significantly at temperatures above 150°C making them unsuitable for high temperature applications
Solution Approach 1:
The patent changes the fundamental material parameter (band gap) from silicon to silicon carbide, enabling the TVS device to maintain low current leakage characteristics at high temperatures above 150°C while preserving voltage suppression functionality. The SiC material's wider band gap inherently reduces thermal generation of charge carriers, solving the leakage problem.
Solution Approach 2:
The invention employs composite material structure combining silicon carbide semiconductor layers with matched coefficient of thermal expansion (CTE) packaging materials. This composite approach ensures both the semiconductor functionality and thermal stability, preventing delamination and maintaining reliability in high temperature environments up to 300°C.
2Reliability
If epoxy encapsulation is used for TVS device packaging, then device protection is provided, but thermal strain and decomposition occur at temperatures above 185°C
Solution Approach 1:
The patent changes the packaging material from epoxy to glass encapsulation, which maintains structural integrity and protective functionality at temperatures up to 300°C. The glass material's higher thermal stability and inertness prevent decomposition and chemical degradation that occur with epoxy at elevated temperatures.
Solution Approach 2:
The invention applies localized material selection where glass encapsulation is used specifically in the high temperature region (above 185°C) to provide thermal stability, while maintaining the TVS device's core semiconductor structure. This localized quality change addresses the packaging failure mode without redesigning the entire device.
3Measurement precision
If electronics are placed close to engine core for sensor performance, then sensor performance improves, but exposure to high ambient temperatures and voltage surges increases
Solution Approach 1:
The patent employs a sacrificial TVS device that can be strategically placed in high temperature zones near the engine core to protect critical electronics. The TVS device absorbs the thermal and electrical stress, acting as a disposable protective element that can be replaced rather than protecting the entire electronics system.
Solution Approach 2:
The SiC-based TVS device serves as an intermediary protective element between the high temperature environment and the sensitive electronics. It mediates the harsh conditions (high temperature and voltage surges) and prevents them from reaching the protected electronics, enabling close placement of sensors while maintaining electronics reliability.
4Temperature
If cooling systems are added to protect electronics from high temperature, then temperature control improves, but installation complexity and cost increase
Solution Approach 1:
The patent enables the TVS device and surrounding electronics to operate in high temperature environments without external cooling systems. The SiC semiconductor and glass encapsulation materials inherently withstand temperatures up to 300°C, making the system self-sufficient and eliminating the need for active cooling infrastructure.
Solution Approach 2:
The invention changes the operational temperature parameter from typical commercial ranges (below 150°C) to high temperature ranges (up to 300°C) by using SiC semiconductor technology. This parameter change eliminates the need for cooling systems entirely, as the device is designed to thrive in high temperature conditions rather than requiring active thermal management.
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 SiC transient voltage suppressor assembly provides reliable voltage suppression and minimal current leakage across a wide temperature range, enabling the protection of sensitive electronics from voltage spikes and electromagnetic interference in high-temperature environments without the need for additional cooling.
Implementation Method 1
When a voltage greater than a predetermined magnitude is applied across the first and second electrodes, the TVS assembly operates in a punch-though mode that permits a relatively large amount of current to flow through the TVS assembly
Implementation Method 2
encapsulating the die in a glass housing at least partially surrounding the die, and coupling a respective electrode in electrical communication with each of the first and the second sides, each electrode having a coefficient of thermal expansion that substantially matches a coefficient of thermal expansion of the glass housing
Data Source
AI summary
A method of forming a silicon carbide transient voltage suppressor (TVS) assembly and a system for a transient voltage suppressor (TVS) assembly are provided. The TVS assembly includes a semiconductor die in a mesa structure that includes a first layer of a first wide band gap semiconductor having a conductivity of a first polarity, a second layer of the first or a second wide band gap semiconductor having a conductivity of a second polarity coupled in electrical contact with the first layer wherein the second polarity is different than the first polarity. The TVS assembly also includes a third layer of the first, the second, or a third wide band gap semiconductor having a conductivity of the first polarity coupled in electrical contact with the second layer. The layer having a conductivity of the second polarity is lightly doped relative to the layers having a conductivity of the first polarity.