Molten Salt SU-8 Template Removal for Metal Matrix Devices
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Solution Overview
Problem
Current methods for removing three-dimensional photonic crystal templates are inefficient, particularly due to the high temperatures required, which can damage fine-scale structural and mechanical properties of deposited metals, and are not compatible with devices featuring complicated microstructures.
Innovation Solution
A method using a molten salt bath composed of alkali metal hydroxides, such as lithium hydroxide and potassium hydroxide, at temperatures below 350°C to decompose and remove cured aromatic epoxy resins, allowing for rapid degradation without significant oxidation to the metal or alloy, facilitating the formation of metal matrix devices with percolating voids for enhanced heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pyrolysis or traditional molten salt baths are used to remove SU-8 templates, then the template can be removed, but temperatures greater than 300°C are required which can adversely affect the fine scale structural and mechanical properties of deposited metals
Solution Approach 1:
The invention changes the chemical composition parameters of the molten salt from traditional oxidizing salts (nitrates, carbonates) to a specific mixture of alkali metal hydroxides (NaOH, KOH, LiOH) in defined ratios. This parameter change enables the removal process to proceed at lower temperatures (200-350°C) while maintaining effective template removal, thus preserving the fine scale structural and mechanical properties of deposited metals.
Solution Approach 2:
The invention uses a composite molten salt system comprising multiple alkali metal hydroxides (NaOH, KOH, and LiOH) in specific proportions rather than a single salt. This composite composition synergistically enhances the ability to dissolve cured SU-8 at lower temperatures, resolving the contradiction between removal effectiveness and temperature control.
2Manufacturing precision
If traditional oxidizing molten salt baths are used, then template removal can be achieved, but significant oxidation occurs to the metal or alloy
Solution Approach 1:
The invention creates a chemically inert removal environment by using alkali metal hydroxide molten salts instead of oxidizing salts. These hydroxide-based molten salts do not promote oxidation of metals, thereby protecting the deposited metal or alloy from significant oxidation while still enabling effective template removal through alternative chemical mechanisms.
Solution Approach 2:
The invention converts the typically harmful oxidizing nature of molten salt baths into a beneficial non-oxidizing environment. By replacing oxidizing anions (nitrate, carbonate) with hydroxide anions, the process eliminates the harmful oxidation effect while maintaining the beneficial template removal capability through hydroxide-based dissolution mechanisms.
3Productivity
If reactive ion etching or downstream chemical etching is used, then removal rate can be increased, but the methods are damaging to semiconductors and result in large oxide layers forming on metals
Solution Approach 1:
The invention changes the fundamental chemical parameters of the removal medium from oxidizing environments (RIE plasma, CF4/O2 mixtures) to a non-oxidizing molten salt environment based on alkali metal hydroxides. This parameter change enables high removal rates comparable to aggressive etching methods while eliminating the harmful side effects of semiconductor damage and excessive metal oxidation.
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
Enables the rapid and non-oxidative removal of three-dimensional photonic crystal templates, preserving the structural integrity of metal matrix devices and enabling the creation of high thermal conductivity materials suitable for heat transfer applications.
Implementation Method 1
consum e a cured aromatic epoxy resin by degradation and dissolving the cured resin in a molten salt
Implementation Method 2
The liquid state can be formed at temperatures above about 250° C.
Data Source
AI summary
A method of decomposing a cured aromatic epoxy resin uses a molten salt bath at less than about 350° C. The molten salt bath includes a plurality of alkali metal hydroxides. The cured aromatic epoxy resin can be in intimate physical contact with a metal or alloy. The cured aromatic epoxy resin can be patterned by a lithographic method. The lithographic method can be multibeam interference lithography to form a three-dimensional photonic crystal template on a conductive substrate for electrodeposition of metal. Contacting the three-dimensional photonic crystal template with the electrodeposited metal with the molten salt bath can form a metal matrix device displaying a periodic pattern that is the inverse of the periodic pattern of the decomposed three-dimensional photonic crystal template.