Direct Aluminum-Ceramic Bonding for Stronger Power Module Substrates
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Solution Overview
Problem
Conventional metal/ceramic bonding substrates face issues with low bonding strength and thermal expansion differences leading to warping, which deteriorate heat radiating properties in power modules for electric vehicles and machine tools.
Innovation Solution
A method involving a ceramic substrate in a mold with reduced oxygen concentration and dew point, where molten aluminum is injected and solidified to form an aluminum plate directly bonded to the ceramic substrate, achieving high bonding strength by minimizing oxide layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If soldering is used to bond the metal base plate to the metal/ceramic insulating substrate, then the bonding process is simple and conventional, but the metal base plate warps due to thermal expansion differences and bonding strength is limited
Solution Approach 1:
The invention changes the bonding parameters by eliminating soldering and using direct bonding between the aluminum plate and ceramic substrate. This involves controlling bonding temperature, pressure, and atmosphere to achieve strong bonding without the intermediate solder layer, thereby improving bonding strength while avoiding warping issues
Solution Approach 2:
The invention extracts and removes the solder layer from the bonding interface between the metal base plate and metal/ceramic insulating substrate. By eliminating this intermediate layer, the direct bonding surface is exposed, allowing for stronger mechanical and thermal contact while preventing the warping that occurs during soldering processes
2Ease of manufacture
If soldering is used to bond semiconductor chips to the metal/ceramic insulating substrate, then the bonding process is conventional and simple, but heat radiating properties deteriorate due to low thermal conductivity of solder
Solution Approach 1:
The invention extracts and removes the solder layer from the bonding interface between the metal base plate and metal/ceramic insulating substrate. By eliminating this intermediate layer, the direct bonding surface is exposed, allowing for stronger mechanical and thermal contact while preventing the warping that occurs during soldering processes
Solution Approach 2:
The invention creates a composite structure with direct aluminum plate to ceramic substrate bonding, eliminating the need for solder intermediate layers. This composite approach uses the inherent properties of aluminum and ceramic materials to achieve both strong mechanical bonding and superior thermal conduction, improving heat radiating efficiency
3Loss of energy
If direct bonding of aluminum plate to ceramic substrate is implemented, then heat radiating properties improve and warping is reduced, but bonding strength is insufficient at about 30 kg/cm
Solution Approach 1:
The invention changes the bonding parameters by controlling temperature, pressure, and atmosphere during the direct bonding process. By optimizing these parameters, the bonding strength is enhanced while maintaining the thermal and mechanical advantages of direct bonding, resolving the contradiction between bond strength and heat radiating efficiency
Solution Approach 2:
The invention employs an inert atmosphere during the direct bonding process to prevent oxidation of the aluminum plate surface and ceramic substrate. This controlled environment ensures clean bonding interfaces and enhances bonding strength while preserving the thermal conductivity benefits of direct contact
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 method produces a metal/ceramic bonding substrate with a bonding strength of 330 N/cm or more, significantly higher than conventional substrates, while maintaining low oxide layer thickness, enhancing thermal conductivity and stability.
Implementation Method 1
injecting a molten metal of aluminum into the mold so as to allow the molten metal to contact one side of the ceramic substrate
Implementation Method 2
cooling and solidifying the molten metal in the mold to form an aluminum plate on the one side of the ceramic substrate
Implementation Method 3
lowering an oxygen concentration to 25 ppm or less and a dew point to −45° C. or lower in the furnace
Data Source
AI summary
A metal/ceramic bonding substrate wherein the bonding strength of an aluminum plate bonded directly to a ceramic substrate is higher than that of conventional metal/ceramic bonding substrates, and a method for producing same, wherein the method includes arranging a ceramic substrate in a mold; putting the mold in a furnace; lowering an oxygen concentration to 25 ppm or less and a dew point to −45° C. or lower in the furnace; injecting a molten metal of aluminum into the mold to contact the surface of the ceramic substrate; and cooling and solidifying the molten metal to form a metal plate for a circuit pattern of aluminum on one side of the ceramic substrate to bond one side of the metal plate for a circuit pattern directly to the ceramic substrate, while forming a metal base plate of aluminum on the other side of the ceramic substrate.