Optical Element Stack Assemblies with Spacer Height Control
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Solution Overview
Problem
Existing fabrication techniques for optical element stack assemblies face issues with height variation due to adhesive, adhesive migration affecting optical characteristics, and incomplete sealing, which complicates achieving effective seals.
Innovation Solution
The optical element stack assembly features sub-assemblies with edge features and a spacer that surrounds and holds them together, using a wafer-level method where edge features are attached by adhesive and spacers are formed via vacuum injection molding to control z-height and protect optical elements from environmental factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is used to bond wafers to form stack assemblies, then the wafers can be joined together, but height variation occurs and adhesive may migrate onto optical element surfaces interfering with optical characteristics
Solution Approach 1:
The invention divides the bonding interface into two separate functions: a spacer structure provides the mechanical bond and height reference, while a separate adhesive layer provides sealing. This segmentation prevents the adhesive from causing height variation while maintaining bond strength.
Solution Approach 2:
The spacer acts as an intermediary element between the wafers, providing a stable mechanical bond and height reference without the height variation problems of adhesive. The adhesive then seals around this spacer without affecting the optical element height.
2Strength
If adhesive is used to bond wafers, then wafers can be joined, but adhesive may migrate onto adjacent surfaces and interfere with optical characteristics
Solution Approach 1:
The invention extracts the bonding function from the adhesive and assigns it to the spacer structure. The adhesive is then taken out of the bonding role and used only for sealing, which prevents migration onto optical surfaces while maintaining bond strength.
Solution Approach 2:
The bonding and sealing functions are segmented into separate components: the spacer handles bonding without migration issues, while the adhesive handles sealing in a controlled manner away from optical elements.
3Object-generated harmful factors
If small amounts of adhesive are used to avoid migration, then optical element surfaces are protected, but effective sealing becomes difficult to achieve
Solution Approach 1:
The sealing function is separated from the bonding function. The adhesive is used exclusively for sealing around the spacer, allowing sufficient adhesive to be applied for effective sealing without risking migration onto optical elements, since the spacer physically prevents this.
Solution Approach 2:
The spacer serves as an intermediary that enables effective sealing by providing a barrier that allows more adhesive to be used for sealing purposes without the risk of migration onto optical surfaces.
4Strength
If adhesive is used at the wafer interface, then wafers can be bonded, but z-height control becomes difficult due to height variation
Solution Approach 1:
The bonding interface is segmented into a spacer structure that provides the mechanical bond and height reference, separate from the adhesive that provides sealing. This eliminates the height variation caused by adhesive while maintaining bond strength.
Solution Approach 2:
The spacer acts as an intermediary that provides a stable mechanical bond and height reference, preventing the adhesive from causing z-height variation while maintaining effective bonding.
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 precise control of z-height, minimizes adhesive interference with optical elements, and provides effective sealing and protection from water, moisture, and dust, enabling consistent and reliable assembly of optical element stack assemblies.
Implementation Method 1
A vacuum injection molding technique can be used to provide the spacer
Implementation Method 2
The edge features of the first sub-assembly are attached, by adhesive, to the edge features of the second sub-assembly
Data Source
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AI summary
Optical stack assemblies and fabrication techniques thereof. The optical stack assembly includes first and second sub-assemblies, each of which include a substrate and a sub-structure fixed to the respective substrate. Each sub-structures includes a respective first edge feature and a respective second edge feature that project away from the substrate of that sub-structure, each second edge feature being disposed laterally closer to an outer periphery of the respective sub-structure than the first edge feature of the same sub-structure. The first edge feature of the first sub-structure is in direct contact with the first edge feature of the second sub¬ structure, while the second edge feature of the first sub-structure and the second edge feature of the second sub-structure are attached to one another by adhesive. At least one of the first or second sub-structures includes an optical element on a same side of the sub-structure as the first and second edge features of that sub-structure. The optical element stack assembly further includes a spacer laterally surrounding, and moulded to, the first and second sub-assemblies.