Piezo Stack Passivation for Arcing Prevention
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Solution Overview
Problem
Existing piezo stacks face issues with electrical arcing and short circuits due to inadequate passivation, particularly at the edges, leading to material waste and increased complexity in the passivation process, which can result in rejected products.
Innovation Solution
A method for passivating piezo stacks by applying rectangular passivation layers on opposite sides of the stack, ensuring uniform coverage and preventing edge thinning, combined with additional layers extending beyond the initial passivation thickness to prevent arcing, using materials like polyimide for insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passivation coating is applied to all four sides of the piezo stack separately, then electrical insulation is improved, but the process complexity and material waste increase due to edge thinning and layer inhomogeneities
Solution Approach 1:
The passivation process is segmented into two distinct phases: first applying coating to only two opposite sides of the piezo stack, then after cutting, applying coating to the remaining two sides. This segmentation allows each coating operation to focus on specific surfaces, avoiding the complexity and defects associated with coating all four sides simultaneously or sequentially in the conventional manner.
Solution Approach 2:
The passivation coating is applied preliminarily to two opposite sides before the piezo stack is cut into individual actuators. This preliminary action ensures uniform coating thickness and proper curing before the cutting process, preventing edge thinning and layer inhomogeneities that would occur if coating were applied after cutting.
2Reliability
If passivation coating is applied to all four sides of the piezo stack, then electrical insulation is improved, but material waste increases due to defective piezo stacks being rejected
Solution Approach 1:
The process segments the passivation operation to apply coating to only two sides before cutting, rather than all four sides. This reduces the amount of coating material required per unit and eliminates the waste associated with rejecting defective stacks that result from improper passivation of all four sides.
Solution Approach 2:
Instead of applying passivation coating to all four sides (excessive action), the method applies coating to only two opposite sides (partial action) before cutting. This partial application is sufficient to prevent electrical arcing and short circuits during operation, while reducing material consumption and eliminating the need to reject defective stacks.
3Reliability
If passivation coating is applied to all four sides of the piezo stack, then electrical insulation is improved, but layer thickness inhomogeneities and edge thinning occur
Solution Approach 1:
The passivation process is divided into two separate coating operations: first coating two opposite sides before cutting, then coating the remaining two sides after cutting. This segmentation allows each coating operation to achieve uniform thickness on the specific surfaces treated, avoiding the edge thinning and inhomogeneities that occur when all four sides are coated in a single operation.
Solution Approach 2:
The passivation coating is applied preliminarily to two opposite sides before the piezo stack is cut into individual actuators. This preliminary coating ensures uniform thickness and proper adhesion on the larger surface area, preventing edge thinning and layer inhomogeneities that would occur if coating were applied after the stack is cut into smaller individual units.
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 ensures reliable electrical insulation, reduces material waste, and simplifies the passivation process by avoiding edge thinning and layer inhomogeneities, thereby enhancing the operational stability and manufacturing efficiency of piezo stacks.
Implementation Method 1
In the case of the piezo ceramics used, use is made of the effect that they become charged under mechanical pressure, or tension, and on the other hand they expand when an electrical voltage is applied along the principal axis of the ceramic layer
Implementation Method 2
Passivation generally involves a nonmetallic protective layer, insulation layer or the like, by means of which electrical arcing and short circuits between neighboring electrode layers can be avoided
Data Source
AI summary
A piezo-stack includes a plurality of lateral surfaces and a first passivation layer applied to a first lateral surface. The first passivation layer terminates flush with opposing lateral surfaces that adjoin the first lateral surface.