Transparent Substrate UV Windows for Epoxy Curing
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Solution Overview
Problem
Photonic chips with Through Silicon Vias (TSVs) face challenges in edge coupling due to their thinness, which restricts the creation of deep trenches for lens or fiber placement, and conventional edge coupling techniques cannot be used, necessitating alternative alignment methods that are cost-effective and precise.
Innovation Solution
A fiber array unit (FAU) with a transparent substrate and optical windows is used to align and bond optical fibers to a photonic chip, employing passive alignment features and UV light to cure epoxy, allowing for efficient and precise optical coupling without active alignment feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional edge coupling techniques are used with thin photonic chips having TSVs, then the chip thickness is reduced for higher integration, but the ability to create deep trenches for lens or fiber placement is lost
Solution Approach 1:
The patent introduces an intermediary epoxy bonding layer between the optical fiber and the photonic chip surface. This epoxy layer fills the gap created by the thin chip structure and enables effective optical coupling without requiring deep trenches. The epoxy acts as a mediator that transfers optical signals across the interface between the fiber and chip while accommodating the reduced chip thickness.
Solution Approach 2:
The patent replaces the mechanical trench-based fiber placement system with a chemical bonding system using UV-curable epoxy. Instead of relying on mechanical structures (deep trenches) to position and couple fibers, the invention uses a chemical adhesive that can be precisely applied and cured to achieve both positioning and optical coupling in a single step.
2Measurement precision
If passive alignment is implemented without UV windows, then alignment precision is improved, but epoxy curing cannot be achieved through the substrate
Solution Approach 1:
The patent applies local quality by creating UV-transparent windows at specific locations on the silicon substrate where epoxy curing is required. The substrate maintains its opaque silicon material properties in most areas for mechanical strength and thermal management, but has localized transparent regions that allow UV light transmission. This enables selective UV curing of epoxy only at the necessary bonding locations while preserving the overall substrate characteristics.
Solution Approach 2:
The patent segments the substrate into regions with different optical properties - UV-transparent window areas and UV-opaque silicon areas. This segmentation allows the substrate to simultaneously provide mechanical support (through the opaque silicon) and enable UV curing (through the transparent windows), resolving the contradiction between maintaining substrate integrity and allowing epoxy curing.
3Strength
If silicon substrate is used for FAU, then mechanical strength is improved, but UV light transmission to cure epoxy is blocked
Solution Approach 1:
The patent modifies the silicon substrate by creating localized UV-transparent windows in specific regions where epoxy bonding is required. The majority of the substrate retains its opaque silicon material properties for mechanical strength, while the window regions are made transparent to UV light. This local quality change allows the substrate to simultaneously provide structural support and enable UV curing at the bonding locations.
Solution Approach 2:
The patent creates a composite structure by combining UV-transparent material regions with UV-opaque silicon material regions in the same substrate. This composite approach allows different material properties to coexist in different spatial locations, enabling both mechanical strength (from the silicon) and UV transmission (from the transparent windows) within the same substrate component.
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 method enables accurate and cost-effective passive alignment and bonding of optical fibers to photonic chips with TSVs, overcoming the limitations of conventional edge coupling techniques and ensuring high-performance optical signal transmission.
Implementation Method 1
curing the epoxy by passing electromagnetic radiation through the transparent substrate and the optical window to reach the epoxy well
Data Source
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AI summary
Embodiments herein describe a fiber array unit (FAU) (150) configured to couple a photonic chip (140) with a plurality of optical fibers (155). Epoxy can be used to bond the FAU (150) to the photonic chip (140). Flowever, curing the epoxy between the FAU (150) and the photonic chip (140) is difficult. As such, the FAU (150) can include one or more optical windows (415) etched into a non-transparent layer (405) that overlap with epoxy wells (205) in the photonic chip (140). Moreover, the FAU (150) may include a transparent substrate (305) on which the non-transparent layer (405) is disposed that permits UV light to pass therethrough. As such, during curing, UV light can be pass through the transparent substrate (305) and through the optical windows (415) in the non-transparent layer (405) to cure the epoxy disposed between the FAU (150) and the photonic chip (140).