Micromold Electroforming via Selective Conductive Masking
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Solution Overview
Problem
Existing methods for manufacturing micromolds for metal micromechanical components via electroforming face challenges in preventing parasitic galvanic growth on the top surface, often resulting in incomplete filling due to conductive layers on the upper surfaces, and require complex and delicate processes to ensure proper insulation and conductive layer deposition.
Innovation Solution
A method involving the application of a solvent-based ink on the horizontal surfaces of the top photoresist layer, followed by directional vacuum evaporation of a conductive layer, and subsequent controlled chemical etching to minimize metal deposition on vertical surfaces, ensuring only the bottom and horizontal surfaces are conductive, while keeping the upper surface non-conductive.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive layer is deposited on the entire mold surface to ensure proper electroforming operation, then electrical conductivity is improved, but parasitic galvanic growth occurs on the top surface causing incomplete filling
Solution Approach 1:
The patent applies different surface properties to different regions of the mold: the bottom and lateral surfaces are made conductive to ensure proper electroforming operation, while the top surface is kept non-conductive to prevent parasitic galvanic growth. This is achieved through selective masking techniques that protect the top surface during metallization, creating local quality differences that resolve the contradiction between needing conductivity for operation and avoiding harmful galvanic effects.
2Object-generated harmful factors
If mechanical machining is used to remove the conductive top layer to prevent galvanic growth, then parasitic growth is prevented, but burrs are created and fine structures are damaged
Solution Approach 1:
The patent prevents the formation of the conductive layer on the top surface in the first place through preliminary masking before metallization. By applying a protective mask to the top surface before depositing the conductive layer, the harmful galvanic growth is prevented without requiring subsequent removal operations. This preliminary action avoids the need for mechanical machining that would damage fine structures.
3Manufacturing precision
If additional photomask and lift-off technique are used to apply conductive layer only on first level, then selective metallization is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent achieves selective metallization by creating local quality differences through masking. The mask is applied to protect specific regions (top surface or upper levels) while allowing metallization on other regions (bottom and lateral surfaces). This approach provides manufacturing precision for selective conductive layer deposition without requiring complex lift-off techniques or multiple photomasks, as the masking itself creates the necessary spatial selectivity.
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 approach effectively prevents parasitic galvanic growth and ensures proper filling of the mold by maintaining the upper surface as non-conductive, reducing the risk of burrs and preserving the fine structures of the resin mold, while simplifying the manufacturing process.
Implementation Method 1
apply an ink to all or part of the horizontal surfaces of the top layer of photoresist by mechanical transfer from an ink pad
Implementation Method 2
deposit a conductive layer on the micromold by directional vacuum evaporation parallel to the vertical sides of the cavity
Implementation Method 3
deposit a conductive layer on the micromold by directional vacuum evaporation
Implementation Method 4
remove the second conductive layer covering the vertical sides of the cavity by controlled chemical etching
Implementation Method 5
remove the ink, thereby removing the conductive layer placed on said ink
Data Source
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AI summary
The present invention relates to a method for manufacturing micromolds for depositing a homogeneous metallic layer by electroforming in a multi-level cavity. According to this application, a method for manufacturing micromolds for electroforming a micromechanical component having at least two levels is proposed. This method comprises the following steps: a) applying, illuminating, and developing at least two layers of photoresist, namely a first layer and a top layer, to obtain a micromold with at least two levels of polymerized photoresist, comprising at least one cavity having a bottom formed by a first conductive layer covering the substrate, upper horizontal surfaces of the first level, upper horizontal surfaces of the top layer, and vertical sides; b) depositing a conductive layer on the bottom of the cavity and on the upper horizontal surfaces of the first level.characterized in that the deposition of this layer comprises the steps: i) applying ink to all or part of the horizontal surfaces of the top layer of photoresist by mechanical transfer from an ink pad, ii) depositing a conductive layer onto the micromold by directional vacuum evaporation parallel to the vertical sides of the cavity in order to minimize the thickness of metal deposited on these vertical sides, the thickness of metal deposited on the vertical sides being less than that deposited on the horizontal surfaces, iii) removing the conductive layer covering the vertical sides of the cavity by controlled chemical etching, said conductive layer covering only the bottom of the cavity and the upper horizontal surfaces of the first level and the top layer, iv) removing the ink, thereby removing the conductive layer placed on said ink.