Spray-Coated Protective Layer for MEMS Actuators

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Solution Overview

Problem

In microelectromechanical (MEMS) devices, applying a protective layer to sensitive components with non-flat profiles is challenging due to variations in topography, leading to thin and thick portions, and an overly thick layer can hinder actuator movement, while existing deposition methods like spin coating result in non-uniform layers.

Innovation Solution

A method using a curable organic material, such as SU-8, is applied via spray coating to form a continuous protective layer with specific thickness variations to ensure actuator functionality and fluid impermeability, with a curing temperature below 240°C to avoid material deformation and stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If spin coating is used to apply protective coating, then the coating process is simple and fast, but the layer thickness becomes non-uniform over non-flat surfaces

Engineering Contradiction:

Improvecoating process speedVSAvoidlayer thickness uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent changes the application method parameter from spin coating to spray coating, which fundamentally alters how the material is deposited. Spray coating allows for better control of material distribution and thickness uniformity across non-planar surfaces while maintaining efficient production rates.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical spin coating process with a spray coating process that uses aerosolization and controlled deposition. This substitution enables more precise control over layer formation and thickness distribution without relying on centrifugal forces that cause non-uniformity on complex surfaces.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If protective coating is made thin to allow actuator movement, then actuator functionality is maintained, but fluid impermeability is compromised

Engineering Contradiction:

Improveactuator movementVSAvoidfluid impermeability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent applies different thickness requirements to different regions: the protective layer is made thin over the actuator surface to allow movement, while being thicker in surrounding regions to ensure fluid impermeability. This local differentiation resolves the contradiction between maintaining actuator functionality and preventing fluid breaches.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent transitions from a single-layer uniform thickness approach to a multi-layer or variable thickness approach, effectively adding a dimensional aspect to the protective coating design. This allows the coating to have thin regions for actuator movement and thick regions for fluid barrier functionality simultaneously.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If protective coating is made thick to ensure fluid impermeability, then fluid barrier performance is improved, but actuator movement is hindered

Engineering Contradiction:

Improvefluid impermeabilityVSAvoidactuator movement

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

4Reliability

If high curing temperature is used to cure the protective layer, then complete curing is achieved, but sensitive components are damaged

Engineering Contradiction:

Improvecuring completenessVSAvoidcomponent damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the curing temperature parameter from high temperature to below 240°C, which is specifically selected to be sufficient for complete curing of the protective coating while remaining below the damage threshold for sensitive MEMS components. This parameter optimization resolves the contradiction between curing completeness and component safety.

Inventive Principle:

Principle #35Parameter changes

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

The method achieves a uniformly thick protective layer that prevents fluid exposure to sensitive components, maintains actuator functionality by ensuring adequate thickness and uniformity, and minimizes stress on underlying structures, while being compatible with materials like PZT.

Implementation Method 1

Photoimageable materials provide a convenient means for forming patterned layers, such as in a semiconductor device. An exemplary process for patterning photoimageable materials is to expose the materials to radiation, such as light, and developing to remove unwanted portions material and to form a desired pattern.

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Implementation Method 2

A method using a curable organic material like SU-8, applied via spray coating, forms a continuous protective layer with specific thickness variations

Methodology Applied

Scientific EffectSpray coating: Spray

Data Source

PatentUS8389084B2Device with protective layer

Publication Date: 2013.03.05 FUJIFILM CORP

AI summary

A fluid impermeable protective layer is described for a structure that has a 3-dimensional profile. The 3-dimensional profile can include actuators. The protective layer is applied so that there are no breaches in the protective layer and so that the protective layer is not too thick to prevent the actuators from being able to properly function.