Thick Copper Electrodeposition on Sintered Substrates
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Solution Overview
Problem
Existing methods for electrodepositing metal layers on ceramic substrates face challenges such as poor adhesion, defects like nodules and whiskers, and difficulty in achieving homogeneous alloying and thickness, especially in high power electronic applications where thermal stress is a concern, leading to issues with electrical and thermal conductivity.
Innovation Solution
A method involving pre-treatment of the sintered layer with a micro etchant containing sulfuric acid and peroxo compounds, followed by electrodepositing a copper layer using an acidic copper plating solution with specific additives and pulse plating, to achieve high adhesion, low defect density, and improved conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If sintered metal powder containing pastes are used as adhesive layers on ceramic substrates, then good adhesion is achieved, but the resulting layers have non-homogeneous alloying, non-uniform thickness, and contain impurities like voids, blisters, and oxides
Solution Approach 1:
The sintered metal powder layer is pre-treated with a micro-etchant solution containing sulfuric acid and peroxo compounds before electrodeposition. This preliminary chemical treatment removes surface impurities, oxides, and organic residues, and creates a micro-roughened surface that enhances subsequent copper layer adhesion while eliminating the harmful effects of paste contaminants
Solution Approach 2:
The invention changes the chemical and physical parameters of the sintered layer surface through controlled micro-etching. The etchant composition (sulfuric acid concentration, peroxo compound type and concentration, temperature, treatment time) is optimized to selectively remove impurities while preserving the underlying metal structure, transforming the surface from contaminated to clean and receptive
2Device complexity
If conventional pre-treatment methods are used before electrodeposition, then the process is simple, but defects like nodules and whiskers occur in the deposited copper layer
Solution Approach 1:
The invention uses a specifically formulated micro-etchant with optimized parameters: sulfuric acid concentration (5-50 g/L), peroxo compound concentration (5-50 g/L), treatment temperature (20-80°C), and treatment time (30 seconds to 5 minutes). These parameter changes enable effective impurity removal without excessive etching that would create surface defects
Solution Approach 2:
Peroxo compounds (hydrogen peroxide, peroxodisulfate, permonosulfate) are introduced as strong oxidizing agents in the micro-etchant. These oxidants rapidly remove organic residues, reduce metal oxides, and clean the sintered layer surface more effectively than acid alone, significantly reducing defect formation in the subsequent copper deposition
3Reliability
If thick copper layers are electrodeposited for high power electronic applications, then electrical and thermal conductivity is improved, but internal stress and adhesion problems increase
Solution Approach 1:
The micro-etching treatment is performed as a preliminary step before electrodeposition of thick copper layers. This pre-cleaning and surface activation ensures optimal nucleation sites for copper deposition, creating a strong interface that can support thick layers without delamination or excessive internal stress
Solution Approach 2:
The micro-etched surface acts as an intermediary layer between the sintered metal powder and the thick copper deposit. The controlled roughening and cleaning create a transition zone that improves mechanical interlocking and chemical bonding, allowing thick copper layers to adhere reliably while maintaining low internal 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 method results in copper layers with high thermal resistance, good electrical and thermal conductivity, and strong adhesion to the sintered layer, reducing defects and internal stress, making it suitable for high power electronic applications.
Implementation Method 1
contacting the at least one electrically conductive, sintered layer with a micro etchant comprising a sulfuric solution and at least one peroxo compound as oxidizing agent
Implementation Method 2
contacting the sintered layer with an electrolytic copper plating solution and applying an electrical current between the sintered layer and at least one anode, and thereby depositing a copper layer onto the sintered layer
Data Source
Figure 1A~1B
Figure 2~3
AI summary
The present invention relates to a method for electrodepositing a thick copper layer onto an electrically conductive, sintered layer. The thick copper layer has a high adhesion strength, is poor in defects and internal stress, and has high electrical and thermal conductivity. The thick copper layer on the sintered layer is suited for printed circuit boards for high power electronic applications.