Circuit Board Manufacturing Using Aluminum Paste and Selective Etching
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Solution Overview
Problem
Existing methods for manufacturing ceramic circuit boards face challenges in achieving high adhesiveness between the substrate and conductor layer while ensuring easy removal of residues after etching, which affects precision and reliability in insulation between interconnections.
Innovation Solution
A method involving a substrate with silicon at the surface, using a metal paste with aluminum particles, and an etchant containing fluoride ions and metal ions with a higher standard electrode potential than aluminum, allows for the formation of a conductor layer with high adhesiveness and precise interconnections by forming a mixed layer of aluminum and silicon at the interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If glass frit containing silicon is added to the paste to provide adhesiveness, then adhesiveness between substrate and conductor layer is improved, but conductivity of the conductor layer deteriorates due to silicon residue after etching
Solution Approach 1:
The invention extracts the harmful silicon component from the conductor layer by using an etchant that selectively removes silicon-containing glass frit residue while preserving the aluminum conductor layer. This resolves the contradiction by removing the insulating residue that deteriorates conductivity and insulation reliability.
Solution Approach 2:
The invention changes the chemical composition parameters of the etchant to include specific concentrations of hydrofluoric acid (0.1-5% by weight) and nitric acid (5-30% by weight), which creates selective etching conditions that remove silicon residue without attacking the aluminum conductor layer, thus maintaining both adhesiveness and conductivity.
2Strength
If sandblast treatment is used to remove conductor layer residue, then adhesiveness is improved, but manufacturing precision deteriorates due to particle size restrictions
Solution Approach 1:
The invention replaces the mechanical sandblast treatment with a chemical etching process using a specifically formulated etchant. This chemical approach selectively removes silicon residue without the particle size limitations of mechanical methods, preserving the high precision of etched circuits while achieving complete residue removal.
Solution Approach 2:
The invention changes from mechanical parameters (particle size, pressure) to chemical parameters (etchant composition, concentration, temperature) to achieve residue removal. This allows precise control over the etching process that maintains circuit precision while effectively removing all silicon residue.
3Reliability
If metal paste with precious metals is used, then conductivity is improved, but cost increases significantly
Solution Approach 1:
The invention replaces expensive precious metals (gold, silver) with inexpensive aluminum metal particles in the paste formulation. Although aluminum is more reactive, the use of a protective etchant formulation and controlled firing process creates a stable, conductive aluminum layer that provides sufficient conductivity for circuit board applications at much lower cost.
Solution Approach 2:
The invention changes the material composition from precious metals to aluminum, and adjusts the paste formulation parameters including particle size distribution, organic vehicle composition, and glass frit content to optimize the firing process and achieve adequate conductivity and adhesion without requiring expensive materials.
4Reliability
If PVD or CVD is used to form conductor layer, then conductivity is improved, but manufacturing cost increases and adhesiveness is insufficient
Solution Approach 1:
The invention replaces expensive vacuum deposition processes (PVD/CVD) with a low-cost screen printing method using metal paste. The paste contains aluminum particles, organic vehicle, and glass frit, which when fired creates a conductive layer with adequate adhesion to the substrate, eliminating the need for costly vacuum equipment and complex process control.
Solution Approach 2:
The invention replaces the vacuum-based physical deposition processes with a chemical-based paste printing and firing system. This substitution uses conventional printing equipment and atmospheric firing instead of vacuum chambers, dramatically reducing manufacturing cost while achieving sufficient conductor layer properties through chemical bonding mechanisms.
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
This method enables high adhesiveness between the substrate and conductor layer, facilitates easy removal of residues, and maintains high precision in circuit formation, resulting in a circuit board with excellent reliability in insulation between interconnections, suitable for high-density chip mounting.
Implementation Method 1
removing with an etchant the conductor layer in a portion where the resist film has not been formed, the etchant containing fluoride ions and metal ions of metal M of which standard electrode potential is higher in value than a standard electrode potential of aluminum
Implementation Method 2
forming a mixed layer of aluminum and silicon at the interface
Data Source
AI summary
The present invention relates to a method for manufacturing a circuit board including the steps of preparing a substrate containing silicon at least at a surface, applying a paste containing aluminum particles onto the substrate, forming a conductor layer on the substrate by firing the substrate to which the paste has been applied, forming a resist film having a specific pattern on the conductor layer, and removing with an etchant, the conductor layer in a portion where the resist film has not been formed, the etchant containing fluoride ions and metal ions of a metal M of which standard electrode potential is higher in value than a standard electrode potential of aluminum, and to a circuit board which can be manufactured with such a method.