Magnet Encapsulation via Adhesive Compression in Plasma Reactors
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Solution Overview
Problem
Conventional magnet encapsulation techniques for high-strength magnets like NdFeB in plasma reactors are labor-intensive and costly due to laser welding, which is difficult to control and can cause thermal and mechanical damage, leading to unpredictable variability and frequent magnetic field mapping.
Innovation Solution
A thin-wall shell encapsulation method using two sliding shell members with a flowable and curable adhesive, where the adhesive is compressed between the shell members and the magnet, providing hermetic sealing and rigid support without the need for high-temperature processing, allowing for encapsulation in either the magnetized or unmagnetized state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser welding is used to encapsulate magnets, then hermetic sealing is achieved, but thermal and mechanical damage occurs leading to unpredictable variability
Solution Approach 1:
The patent replaces the laser welding process (thermal/mechanical system) with a chemical bonding system using two-part epoxy adhesive. The adhesive is injected into the encapsulation shell, allowed to flow and wet the magnet surfaces, then cured to form strong chemical bonds. This substitution eliminates the harmful thermal and mechanical effects of laser welding while achieving equivalent hermetic sealing and structural integrity.
Solution Approach 2:
The patent changes the bonding mechanism from high-temperature welding to room-temperature adhesive curing. By controlling the viscosity, flow characteristics, and curing properties of the epoxy adhesive, the process achieves reliable bonding without the thermal damage associated with laser welding. The adhesive parameters (viscosity, cure time, bond strength) are optimized to replace the welding parameters.
2Reliability
If conventional encapsulation methods are used, then magnets are protected, but the process is labor-intensive and costly
Solution Approach 1:
The encapsulation process is segmented into distinct steps: shell preparation, adhesive injection, magnet placement, and curing. This segmentation allows for automation and standardization, reducing labor intensity. The two-part adhesive system is pre-prepared and injected through automated dispensing, eliminating manual mixing and application steps.
Solution Approach 2:
The adhesive system is designed to be self-aligning and self-leveling. When injected, the low-viscosity adhesive automatically flows to cover the magnet surfaces and fills gaps without requiring precise manual application. The magnet itself serves as the substrate for bonding, eliminating the need for separate mounting operations.
3Strength
If laser welding is used for encapsulation, then structural integrity is achieved, but frequent magnetic field mapping is required due to variability
Solution Approach 1:
The patent replaces laser welding with adhesive bonding, which applies gradual chemical bonding forces rather than concentrated thermal and mechanical stresses. This substitution eliminates the unpredictable variability introduced by laser welding parameters (power, speed, focus), resulting in more consistent magnetic field properties and reduced need for frequent mapping.
Solution Approach 2:
The bonding process parameters are changed from high-energy welding parameters to controlled adhesive curing parameters (temperature, humidity, cure time). These parameters are easier to control and reproduce, leading to more consistent bonding quality and magnetic field characteristics across production batches.
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 reduces costs and variability by simplifying the encapsulation process, eliminating the need for high-temperature processing, and providing a reliable, hermetically sealed structure that minimizes mechanical damage and the need for frequent magnetic field mapping.
Implementation Method 1
A flowable and curable adhesive is inserted with the supported member inside the shell members. The shell members may be pressed together to squeeze the adhesive between the sides of the supported member and the shell and between overlapping portions of the shell members
Implementation Method 2
The compression process may rely upon the mutual attraction along a common axis of two magnetic assemblies
Data Source
AI summary
A magnet encapsulated within a canister formed from two cans into a laminated structure particularly useful in plasma processing reactors. Each can includes an end wall and a cylindrical sidewall. One can additionally includes an annular lip that slidably fits outside the sidewall of the other can with a small gap therebetween. The magnet is inserted into the two cans together with a flowable and curable adhesive such as epoxy. The cans are slid together and compressed to cause the adhesive to flow between the magnet and the two cans and between the lip of one can and the sidewall of the other. The adhesive is cured to bond the magnet to the cans and to bond the cans together and to also hermetically seal the structure. The cans may be deep drawn from non-magnetic stainless steel with wall thicknesses of less than 0.064 mm.