Metal-Ceramic Substrate Bonding Layer Without Silver Migration
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Solution Overview
Problem
Existing methods for producing metal-ceramic substrates, such as DCB and silver-based soldering, face challenges including high temperature requirements, limited ceramic compatibility, and issues with silver migration, which affect the stability and conductivity of the substrates.
Innovation Solution
A metal-ceramic substrate with a bonding layer comprising a high-melting metal (M1 ≥ 700°C), a low-melting metal (M2 < 700°C), an active metal (M3), and a metal from the group of bismuth, gallium, zinc, indium, germanium, aluminum, and magnesium (M4), optimized in terms of weight percentages and silver content, to achieve a stable and conductive bond between the ceramic and metal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silver-based solder is used for bonding metal foil to ceramic body, then bonding stability is improved, but silver migration occurs causing reliability degradation
Solution Approach 1:
The patent removes silver from the solder composition entirely, extracting the harmful element while maintaining bonding functionality through alternative metal combinations (copper, bismuth, indium, zinc, titanium)
Solution Approach 2:
The patent replaces expensive silver with more economical metals like copper, bismuth, and indium that achieve comparable bonding performance without the migration issues, effectively using alternative materials that are less prone to degradation
2Strength
If low-melting metal content in bonding layer is increased to improve bond stability, then bonding strength is improved, but diffusion into metal layer increases reducing thermal and electrical conductivity
Solution Approach 1:
The patent optimizes the melting point parameter of the solder metal to be between 50-450°C, and controls the thickness of the bonding layer at 5-50 μm, creating optimal conditions for bonding without excessive diffusion that would harm conductivity
Solution Approach 2:
The patent creates a composite solder material combining multiple metals (copper, bismuth, indium, zinc, titanium) with specific weight ratios, where copper provides structural integrity and high conductivity, while lower-melting metals like bismuth and indium enhance bonding stability without excessive diffusion
3Reliability
If DCB method is used for bonding copper foil to ceramic body, then bonding stability is improved, but high temperature processing is required increasing energy consumption
Solution Approach 1:
The patent changes the melting point parameter of the solder metal to 50-450°C, significantly lower than DCB's ~1000°C, enabling bonding at reduced temperatures while maintaining stability through the multi-metal composition and controlled layer thickness
Solution Approach 2:
The patent uses a composite solder material combining copper (high melting point, high conductivity) with lower-melting metals (bismuth, indium, zinc) that eutectic or near-eutectic compositions enable bonding at lower temperatures while maintaining bond strength
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 proposed substrate achieves a highly stable bond between the metal and ceramic layers with high thermal and electrical conductivity, while avoiding issues related to silver migration, thus meeting the increasing demands of power electronics.
Implementation Method 1
The role of the active metal is to react with the ceramic material and to thus facilitate a bonding of the ceramic material to the remaining solder, forming a reaction layer
Implementation Method 2
When the copper foil treated in this way is applied to a ceramic body and the composite is fired, the copper compound melts and wets the surface of the ceramic body
Implementation Method 3
the copper compound melts and wets the surface of the ceramic body, so that a stable cohesive bond is achieved
Implementation Method 4
an increase in the low-melting metal content in the bonding layer results in the problem of increased diffusion of the low-melting metal into the metal layer of the metal-ceramic substrate
Data Source
AI summary
A metal-ceramic substrate which has a highly stable bond between the metal layer and the ceramic body, and also high thermal conductivity and electrical conductivity. The metal-ceramic substrate comprises (a) a ceramic body, (b) a metal layer, and (c) a bonding layer located between the ceramic body and the metal layer. The bonding layer comprises (i) a metal M1 having a melting point of at least 700° C., (ii) a metal M2 having a melting point of less than 700° C., (iii) a metal M3 selected from the group of active metals, and (iv) a metal M4 selected from the group consisting of bismuth, gallium, zinc, indium, germanium, aluminum and magnesium. The bonding layer has the following characteristics: (c1) M(M2)EDX=10-20 weight percent, (c2) 15 weight percent≤[M(M4)/M(M2)]ICP*1000 weight percent+M(M2)EDX≤100 weight percent and (c3) M(Ag)EDX<10 weight percent.