Ceramic Substrate Insulation for High Voltage Circuit Boards
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Solution Overview
Problem
Conventional hybrid integrated circuit devices face issues with low breakdown voltage of the insulating layer when handling high voltage circuits, leading to potential short circuits, and increased thermal resistance when thickening the layer to improve breakdown voltage, which hampers heat dissipation.
Innovation Solution
A circuit device design featuring a metal circuit board with ceramic substrates and a semiconductor element mounted on the ceramic substrates, using a ceramic material with high breakdown voltage to insulate the semiconductor element from the circuit board, and employing a thin insulating layer with high thermal conductivity to enhance heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the insulating layer is made thicker to increase breakdown voltage, then voltage endurance is improved, but thermal resistance increases and heat dissipation deteriorates
Solution Approach 1:
The patent applies composite materials by combining ceramic substrate (high dielectric strength and high thermal conductivity) with metal circuit board and semiconductor elements. The ceramic substrate serves as both insulating layer and heat dissipation path, eliminating the trade-off between voltage endurance and heat dissipation by using materials that simultaneously provide both properties.
Solution Approach 2:
The patent changes the material parameter from organic insulating material to inorganic ceramic material, which fundamentally alters both dielectric strength and thermal conductivity parameters. This parameter change allows the insulating layer to achieve both high breakdown voltage and high thermal conductivity, resolving the contradiction between voltage endurance and heat dissipation.
2Temperature
If a thin insulating layer is used to improve heat dissipation, then thermal resistance decreases, but breakdown voltage is insufficient and short circuits occur
Solution Approach 1:
The ceramic substrate combines two previously separate functions (insulation and heat dissipation) into one material. The composite structure of ceramic provides both the thin profile needed for heat dissipation and the high dielectric strength needed for voltage endurance, eliminating the need to choose between the two conflicting requirements.
Solution Approach 2:
By changing the insulating material from epoxy resin to ceramic, the patent simultaneously improves thermal conductivity parameter and dielectric strength parameter. This material substitution allows the insulating layer to be thin (good for heat dissipation) while maintaining high breakdown voltage (good for reliability).
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 effectively prevents short circuits at high voltages while ensuring efficient heat dissipation, achieving both high voltage endurance and improved thermal management.
Implementation Method 1
a fixation substrate made of a ceramic and fixed to the island with a fixing material; and an semiconductor element mounted on an upper surface of the fixation substrate
Implementation Method 2
utilizing a ceramic fixation substrate and a solder with high thermal conductivity for improved heat dissipation
Data Source
AI summary
A circuit device having superior voltage resistance is provided. A structure is achieved that omits the resin layer that is normally provided to the top surface of a circuit board. Specifically, a ceramic substrate (22) is disposed on the top surface of a circuit board (12) comprising a metal, and a transistor (34) such as an IGBT is mounted to the top surface of the ceramic substrate (22). As a result, the transistor (34) and the circuit board (12) are insulated from each other by the ceramic substrate (22). The ceramic substrate (22), which comprises an inorganic material, has an extremely high voltage resistance compared to the conventionally used insulating layer comprising resin, and so even if a high voltage on the order of 1000V is applied to the transistor (34), short circuiting between the transistor (34) and the circuit board (12) is prevented.