Thin Active Solder Foil for Metal-Ceramic Bond Stress Reduction
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Solution Overview
Problem
Existing solder materials for bonding metal layers to ceramic layers in metal-ceramic substrates are inefficient due to high material usage and susceptibility to thermomechanical stresses, which can damage the substrate and reduce its lifespan.
Innovation Solution
A solder material comprising a thin film with a base material and an active metal layer, where the total thickness is less than 25 μm, preferably between 4 and 15 μm, allowing for a stable and permanent bond between metal and ceramic layers, using active metals like titanium, zirconium, and silver-copper-titanium mixtures, and optionally a protective layer to prevent oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick solder materials (above 100 μm) are used for bonding metal layers to ceramic layers, then sufficient material is available to bridge the gap and form reaction layers, but material usage is excessive and the substrate becomes more susceptible to thermomechanical stresses
Solution Approach 1:
The patent changes the thickness parameter of the solder material from conventional thick (above 100 μm) to thin (less than 25 μm, preferably less than 15 μm). This parameter change reduces material consumption while maintaining bonding effectiveness through optimized layer composition with active metals that facilitate chemical bonding to ceramic surfaces.
Solution Approach 2:
The solder material is designed as a composite structure containing a base material (such as copper, silver, or nickel) combined with active metals (such as titanium, zirconium, or hafnium). This composite composition enables the thin foil to achieve both adequate bonding strength and chemical reactivity with ceramic layers, replacing the need for thick homogeneous materials.
2Strength
If thick solder materials are used to ensure adequate bonding material, then bonding strength is sufficient, but the substrate is more susceptible to thermomechanical stresses and damage
Solution Approach 1:
The patent reduces the thickness parameter of the solder material to less than 25 μm, which decreases the mass and thermal inertia of the bonding layer. This helps the substrate respond more uniformly to thermal changes, reducing thermomechanical stress while maintaining bonding strength through the active metal content that promotes strong chemical bonding.
Solution Approach 2:
The composite structure with active metals embedded in the base material provides both bonding strength and thermal compatibility. The active metals form reaction layers with the ceramic that accommodate thermal expansion differences, while the thin overall thickness reduces the bonding layer's resistance to thermal stress.
3Loss of substance
If thin solder materials (less than 25 μm) are used to reduce material usage and thermomechanical stress, then material efficiency improves and stress resistance increases, but adequate bonding material availability becomes challenging
Solution Approach 1:
The thin foil is designed as a composite material containing a base material (copper, silver, or nickel) that provides bulk and material availability, combined with active metals (titanium, zirconium, hafnium, niobium, or cerium) that provide chemical reactivity. This composite structure ensures sufficient bonding material is present in a thin profile.
Solution Approach 2:
The active metals are distributed within the thin foil structure to provide localized chemical reactivity where needed for bonding. This local concentration of reactive elements ensures adequate bonding capability throughout the thin material without requiring overall thickness increase.
4Duration of action of stationary object
If thin solder materials are used to mitigate thermomechanical stresses, then substrate durability improves, but manufacturing precision requirements increase to ensure adequate bonding
Solution Approach 1:
The composite structure with base material and active metals provides a forgiving manufacturing window. The base material ensures adequate thickness and material availability, while the dispersed active metals ensure bonding capability even with normal thickness variations, reducing the need for ultra-precise thickness control.
Solution Approach 2:
By specifying a thickness range (less than 25 μm, preferably less than 15 μm) rather than a single precise value, the patent creates a manufacturing window that accommodates normal production tolerances while still achieving the benefits of thin-foil bonding and reduced thermomechanical stress.
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 thin solder material reduces material usage, enhances bonding efficiency, and mitigates thermomechanical stresses, providing a stable connection that withstands high temperatures and expansion differences between metal and ceramic layers, thus extending the substrate's lifespan.
Implementation Method 1
the active metal has to bridge a comparatively small distance to the ceramic layer and/or metal layer in order to form a reaction layer there, which enables bonding during the AMB process
Implementation Method 2
These carriers or These metal-ceramic substrates are particularly exposed to thermal stress both during production and during operation. Due to the different expansion coefficients of metal and ceramic, this typically leads to comparatively high thermomechanical stresses
Data Source
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AI summary
The invention relates to a solder material (30) for connecting a metal layer (20) to a ceramic layer (10), in particular to form a metal-ceramic substrate as a carrier for electrical components, comprising a base material and an active metal, wherein the solder material (30) is a foil containing the base material in a first layer (31) and the active metal in a second layer (32), and wherein the foil has a total thickness (GD) of less than 50 µm, preferably less than 25 µm and particularly preferably less than 15 µm.