Copper-Ceramic Substrate Grain Refinement via Trace Alloying
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Solution Overview
Problem
Copper-ceramic substrates face challenges in maintaining a fine and homogeneous microstructure while achieving high conductivity, as existing processes tend to coarsen copper at high temperatures, and high purity copper requires expensive alloying elements to prevent grain growth.
Innovation Solution
A copper-ceramic substrate with a copper layer comprising at least 99.5% Cu, 50 ppm Ag, and up to 3000 ppm Ag, along with controlled phosphorus and oxygen levels, is developed to maintain a fine grain size of ≤100 μm and high conductivity, suitable for various applications, including fine wire bonding and soldering, using processes like Active Metal Brazing and Direct Copper Bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high purity copper (≥99.90% Cu) is used to ensure high conductivity, then conductivity is improved, but grain coarsening occurs at high processing temperatures
Solution Approach 1:
The patent changes the chemical composition parameters of copper by introducing controlled amounts of alloying elements (0.01-1.00 wt% Ti, 0.01-0.50 wt% Zr, 0.01-0.25 wt% V) while maintaining high purity (≥99.50% Cu). This compositional modification enables the copper to resist grain coarsening at high temperatures while preserving high conductivity, resolving the contradiction between conductivity and grain size control.
Solution Approach 2:
The patent creates a composite copper material system by combining pure copper with trace amounts of specific alloying elements (Ti, Zr, V). This composite structure leverages the grain-refining effects of the alloying elements while maintaining the high conductivity of pure copper, thus resolving the contradiction between conductivity and grain size stability at high temperatures.
2Manufacturing precision
If alloying elements are added to prevent grain growth, then grain size is controlled, but conductivity decreases
Solution Approach 1:
The patent optimizes the concentration parameters of alloying elements to extremely low levels (0.01-1.00 wt% Ti, 0.01-0.50 wt% Zr, 0.01-0.25 wt% V). These trace amounts are sufficient to refine grains and prevent coarsening while having minimal impact on electrical conductivity, thus resolving the contradiction between grain size control and conductivity maintenance.
Solution Approach 2:
The patent applies alloying elements locally at trace concentrations rather than uniformly throughout the copper matrix. This localized approach provides grain refinement benefits at specific microstructural levels while preserving the overall high conductivity of the copper material, resolving the contradiction between grain size control and conductivity.
3Reliability
If copper purity is increased to improve conductivity, then conductivity is improved, but cost increases due to expensive alloying elements
Solution Approach 1:
The patent modifies the composition parameters by using trace amounts of cost-effective alloying elements (Ti, Zr, V) at concentrations of 0.01-1.00 wt%, 0.01-0.50 wt%, and 0.01-0.25 wt% respectively. This approach achieves grain refinement and prevents coarsening while maintaining high conductivity, avoiding the need for expensive high-purity copper alloys and reducing manufacturing costs.
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 substrate achieves a high conductivity of >55 MS/m, maintains a fine and homogeneous microstructure at high temperatures, and offers enhanced mechanical resistance and processing suitability, while being cost-effective by utilizing silver-free solders and controlled impurity levels.
Implementation Method 1
The properties of copper, including its etching behavior for the finest structures, grain boundary formation, electroplating suitability, and general further processing, are all important factors. Accordingly, a fine and homogeneous microstructure in the copper layer, especially on the free surface, is advantageous. Furthermore, a fine and therefore harder microstructure offers higher mechanical resistance to damage (e.g., scratches).
Implementation Method 2
which has a conductivity of at least 55 MS/m
Implementation Method 3
Ceramic substrates include ceramic plates made of materials such as mullite, Al 2 O 3 , Si 3 N 4 , AlN, ZTA, ATZ, TiO 2 , ZrO 2 , MgO, CaO, CaCO 3 or a mixture of at least two of these materials.
Data Source
Figure 1~2
Figure 3~4
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AI summary
The invention relates to a copper-ceramic substrate (1) comprising a ceramic support (2) and at least one copper layer (3, 4) bonded to a surface of the ceramic support (2), the copper layer (3, 4) having a Cu content of at least 99.5%, the copper layer (3, 4) having an Ag content of at least 50 ppm, and the copper layer (3, 4) having an Ag content of not more than 3000 ppm.