Optical Die Packaging With Lens Protection During Planarization
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Solution Overview
Problem
Conventional methods for forming packages with optical dies often result in damage to micro lenses during planarization processes, leading to degraded transmission performance.
Innovation Solution
The use of a protection layer, such as a die-attach film, is applied to the optical die to protect the micro lens, followed by encapsulation and planarization, then the protection layer is removed to reveal the lens, ensuring it is not damaged by the planarization process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If planarization process is applied to the optical die, then the encapsulant surface is flattened, but the micro lens is damaged leading to degraded transmission performance
Solution Approach 1:
The optical die is divided into two functional surfaces: the first surface retains the micro lens structure for optical functions, while the second surface is planarized for mechanical alignment and bonding. This segmentation allows each surface to be optimized independently, preserving the lens while achieving surface flatness.
Solution Approach 2:
Different surface treatments are applied to different regions of the optical die. The first surface maintains its original micro lens topology for optimal optical performance, while the second surface undergoes planarization to achieve flatness within 1 micrometer. This local differentiation resolves the contradiction between preserving optical structures and achieving surface flatness.
2Manufacturing precision
If the micro lens is exposed during planarization, then the encapsulant can be flattened, but the lens becomes damaged or contaminated
Solution Approach 1:
The optical die is bonded to the encapsulant before the planarization process begins. This preliminary bonding action secures the lens in place and protects it from damage during subsequent planarization operations. The lens is shielded from mechanical contact with planarization tools while still allowing the encapsulant surface to be flattened.
Solution Approach 2:
A protective layer or sacrificial material is applied over the micro lens before planarization to cushion it from mechanical damage. This protective layer absorbs the mechanical stress of planarization while allowing the encapsulant surface to be flattened, preventing direct contact between planarization tools and the delicate lens structure.
3Manufacturing precision
If the optical die is planarized to improve alignment, then the mounting precision is improved, but the micro lens structure is degraded
Solution Approach 1:
The optical die surface is segmented into two distinct regions with different geometries: the first surface maintains the curved micro lens shape for optical focusing, while the second surface is planarized for precise alignment and bonding. This segmentation allows the die to achieve both optical functionality and mechanical alignment precision simultaneously.
Solution Approach 2:
The solution moves from a two-dimensional planar surface to a three-dimensional differentiated surface structure. By creating distinct first and second surfaces with different topologies on the same die, the invention achieves both lens functionality and alignment precision without compromising either aspect.
Data Source
AI summary
A method includes forming a package, which includes an optical die and a protection layer attached to the optical die. The optical die includes a micro lens, with the protection layer and the micro lens being on a same side of the optical die. The method further includes encapsulating the package in an encapsulant, planarizing the encapsulant to reveal the protection layer, and removing the protection layer to form a recess in the encapsulant. The optical die is underlying the recess, with the micro lens facing the recess.