Optical Waveguide Underfill Resin Filling via Segmented Cladding
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Solution Overview
Problem
In optical waveguide devices, the difficulty in pouring underfill resin into contact holes due to the lower face of the optical element touching the upper face of the waveguide limits the reliability of the connection, as air expansion during heating processes can compromise the electric connection.
Innovation Solution
The optical waveguide device is designed with a second cladding layer having opening portions that communicate with contact holes, allowing underfill resin to be filled through these openings, ensuring the lower side of the optical element is sealed and maintaining connection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lower face of the optical element touches the upper face of the optical waveguide, then the optical coupling is improved, but the underfill resin cannot be poured into the contact holes
Solution Approach 1:
The contact hole is divided into two segments: the first contact hole formed in the first cladding layer, and the second contact hole formed in the second cladding layer. This segmentation allows the underfill resin to be poured through the second contact hole while the optical element is mounted on the first cladding layer, resolving the contradiction between optical coupling and resin filling.
Solution Approach 2:
The invention introduces a vertical dimension by forming contact holes through both the first and second cladding layers. The second contact hole extends from the second cladding layer down to the wiring substrate, creating a vertical pathway for underfill resin injection that does not interfere with the horizontal optical coupling between the optical element and waveguide.
2Productivity
If air remains in the contact holes, then the manufacturing process is simpler, but air expansion during heating compromises electric connection
Solution Approach 1:
The invention performs preliminary action by forming the second contact hole through the second cladding layer before mounting the optical element. This preliminary structure preparation enables subsequent underfill resin injection to displace air from the contact holes, preventing air expansion issues during later heating processes while maintaining manufacturing efficiency.
Solution Approach 2:
The underfill resin acts as an intermediary substance that is injected through the second contact hole to displace air from the contact holes. This intermediary material fills the void spaces, preventing air expansion during heating while maintaining the electrical connection between the connection terminal and wiring substrate.
3Device complexity
If the optical element is mounted directly on the waveguide, then the device structure is simpler, but underfill resin cannot seal the lower side of the optical element
Solution Approach 1:
The cladding structure is segmented into a first cladding layer and a second cladding layer. The optical element is mounted on the first cladding layer while the second cladding layer forms an overlying structure with contact holes. This segmentation allows the underfill resin to be injected and seal the lower side of the optical element through the second contact hole, maintaining both structural simplicity and sealing reliability.
Data Source
AI summary
An optical waveguide device includes a wiring substrate, a connection pad formed in the wiring substrate, an optical waveguide in which a first cladding layer, a core layer, and a second cladding layer are formed of the wiring substrate in this order, an opening portion formed in the second cladding layer in a region including the connection pad, a contact hole formed at least in the first cladding layer on the connection pad, and being communicated with the opening portion of the second cladding layer, an optical element, including a connection terminal, connected to the connection pad through the contact hole, and underfill resin filled in the opening portion of the second cladding layer and the contact hole, and sealing a lower side of the optical element, wherein a part of the opening portion or the second cladding layer is exposed from the optical element.