Multi-Level Micromold Conductive Layer Selectivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for manufacturing micromechanical components with multiple levels through electroforming face challenges in achieving uniformity due to issues like mushrooming and microcavities, primarily caused by conductive layer deposition on vertical sides of photoresist structures, which are difficult to prevent effectively.
Innovation Solution
The method involves using dry photoresists like SU-8, which are deposited hot and shaped to form uniform layers, and a conductive layer is applied only to the upper horizontal surfaces of the photoresist micromold, with directional vacuum deposition and controlled chemical attack to minimize conductive layer thickness on vertical sides, ensuring uniform electroforming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If directional evaporation is used to deposit conductive material parallel to vertical sides of photoresist, then gold deposition on vertical sides is reduced, but perfect parallel alignment is difficult to achieve and some gold still deposits on vertical sides
Solution Approach 1:
A masking layer of photoresist is introduced as an intermediary between the conductive material deposition process and the vertical sides of the photoresist structure. This masking layer is selectively applied only to horizontal surfaces where conductive material deposition is desired, and it physically blocks gold particles from depositing on vertical sides during evaporation, eliminating the alignment problem entirely
Solution Approach 2:
The masking layer is applied locally only to horizontal surfaces of the photoresist structure through selective spray coating, creating different surface properties in different locations. This local application ensures conductive material is deposited only where needed while preventing deposition on vertical sides, achieving high selectivity without requiring perfect global alignment
2Area of stationary object
If spray coating technique is used to structure evaporated gold, then complete coverage is achieved, but uniform thin layers are not produced and pronounced edge effects occur
Solution Approach 1:
The spray coating process is applied with excessive coverage initially, coating the entire photoresist structure including vertical sides. However, the masking layer strategy ensures that even though spray reaches all areas, conductive material only deposits where the masking layer is present (horizontal surfaces), eliminating edge effects and achieving uniform thickness through controlled selective deposition rather than controlled spray parameters
3Manufacturing precision
If mask with openings slightly smaller than horizontal surfaces is used, then gold deposition on vertical sides is prevented, but perfect alignment between piece and mask is required and all masking structures must be connected to mask frame generating unwanted masking
Solution Approach 1:
Instead of creating openings in a mask frame and connecting masking structures to it (traditional approach), the invention inverts the approach by applying a masking layer directly to the photoresist structure itself. This eliminates the need for mask frames, connection structures, and complex alignment procedures, as the mask is applied locally where needed rather than globally
4Area of stationary object
If conductive layer is deposited on vertical sides of photoresist structure, then complete coverage is achieved, but mushrooming and microcavities occur during electroforming
Solution Approach 1:
The masking layer acts as an intermediary that selectively permits conductive material deposition only on horizontal surfaces while blocking vertical sides. This ensures complete coverage of intended areas (horizontal surfaces) while preventing deposition on areas that would cause defects (vertical sides), achieving both complete coverage and uniform electroforming without mushrooming or microcavities
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 allows for the production of micromolds with homogeneous metallic layers, significantly reducing manufacturing time and achieving precise, thick layers with minimal parasitic reflections and microcavities, enhancing the quality of electroformed metal components.
Implementation Method 1
irradiate through a mask using a synchrotron or by exposure to ultraviolet rays, develop, i.e. eliminate by chemical means the unpolymerized portions of photoresist
Implementation Method 2
depositing the gold by directional evaporation parallel to the vertical sides of the photoresist
Implementation Method 3
electroform a metal in this cavity in order to obtain the micromechanical component
Data Source
Figure 1~3
Figure 4~6
Figure 7~8
AI summary
The present invention relates to a method for manufacturing micromolds that allows for the deposition of a homogeneous metallic layer by electroforming in a multi-level cavity. The method for manufacturing micromolds for electroforming multi-level micromechanical components comprises successive steps of deposition, irradiation through a photomask, and polymerization of the irradiated portions of photoresist layers, followed by a single step of developing these photoresist layers. A conductive layer is selectively deposited on the visible upper horizontal surfaces of each level of the resulting micromold cavity. The use of dry photoresist allows for the advantageous production of micromolds with two or more levels.Micromolds are characterized in that the upper visible horizontal surfaces of each level of the cavity are covered with a conductive layer, the vertical sides of the cavity being free of a conductive layer.