LED Lens Attachment Using Adhesive Gap for Air Release
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Solution Overview
Problem
Light emitting devices face misalignment issues due to mechanical impacts, adhesive shrinkage, and trapped air during manufacturing processes, leading to inconsistent light output patterns.
Innovation Solution
A light emitting device design featuring a lens element with a cavity and an adhesive strip around the perimeter, including a gap for air release, is used. The adhesive is partially cured for initial shear strength before transport, and sealed with a compatible material to maintain alignment accuracy through subsequent processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is applied to attach lens element to substrate, then lens element is fixed to substrate, but adhesive shrinkage during curing causes misalignment of lens element
Solution Approach 1:
A compliant layer is introduced as an intermediary between the lens element and the adhesive bondline. This compliant layer absorbs the shrinkage forces generated during adhesive curing, acting as a buffer that prevents these forces from transferring to the lens element and causing misalignment. The compliant layer has mechanical properties that allow it to deform and accommodate the volume change of the adhesive while maintaining the positional stability of the lens element.
2Ease of manufacture
If adhesive with low viscosity is used for attachment, then adhesive flows to form seal, but mechanical impact during transport moves lens element before adhesive cures
Solution Approach 1:
The pick-and-place machine performs preliminary alignment of the lens element with the light emitting element before the adhesive fully cures. Alignment features on the substrate and/or lens element are used to establish precise positioning. This preliminary alignment is maintained during transport because the compliant layer and partially cured adhesive provide sufficient temporary stabilization, allowing the lens to remain in the correct position until final curing occurs.
3Strength
If adhesive is cured thermally, then adhesive bond strength increases, but trapped air expands and creates steam pressure that shifts lens element position
Solution Approach 1:
Air vents are designed into the adhesive seal to extract trapped air from the bondline during the curing process. These vents provide escape pathways for air bubbles and gases that are released during thermal curing, preventing pressure buildup that would otherwise push against the lens element and cause positional shifts. The vents allow the adhesive to cure completely while maintaining lens element alignment.
4Object-affected harmful factors
If adhesive forms complete seal around light emitting element, then protection from external elements is improved, but trapped air cannot escape causing misalignment
Solution Approach 1:
The adhesive seal is designed with non-uniform properties: in most regions, the adhesive forms a complete seal to protect the light emitting element from external contaminants, while in specific localized regions (air vents), the seal is intentionally interrupted or made permeable to allow air escape. This local variation in seal quality enables simultaneous achievement of protection and pressure relief functions.
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 high alignment accuracy and reliability of light output patterns by providing a strong bond that withstands mechanical and environmental stresses during manufacturing, maintaining the initial alignment of the lens and light emitting elements.
Implementation Method 1
A strip of adhesive attaches the lens element to the substrate
Implementation Method 2
The adhesive is situated around the perimeter of the lens element, but includes a gap in the perimeter that enables the release of material (e.g. heated air) from beneath the lens element
Implementation Method 3
The adhesive element also serves to isolate the light emitting element from external elements by forming a seal that surrounds the light emitting element
Implementation Method 4
adhesives such as epoxy and silicone that are cured thermally will shrink when the crosslink (cure) occurs, which may introduce a shift in the location of the lens element relative to the light emitting element
Implementation Method 5
during the cure of the adhesive, which usually involves heat, the trapped air will likely expand and create steam pressure inside the lens element
Data Source
Figure 1A~3
Figure 4
AI summary
A light emitting device includes a light emitting element on a substrate, and a lens element that includes a cavity within which the light emitting element is situated, and is optically aligned with the light emitting element. A strip of adhesive that attaches the lens element to the substrate substantially surrounds the light emitting element, but includes a gap that facilitates release of material from the cavity during the attachment of the lens element to the substrate. When the lens element is placed upon the substrate, the adhesive is partially cured to provide a relatively high shear strength before the light emitting device is transported or subjected to other processes. To provide compatibility with subsequent processes or applications, and to protect the light emitting element from the environment, the gap in each device is sealed with a sealing material.