Optical Waveguide Laminated Wiring Board Via Formation
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Solution Overview
Problem
Conventional methods for forming conductive vias in optical waveguide laminated wiring boards face challenges in arranging vias at fine pitches due to aspect ratio and via depth restrictions, leading to insufficient filling of conductive material and reduced yield rates.
Innovation Solution
A method involving the formation of conductive vias in two stages, where a first via hole is filled with a conductive material to form a 'mushroom'-like conductor portion, followed by the formation of a second via hole in a covering cladding layer, allowing for the filling of a second conductor portion, thereby eliminating restrictions on aspect ratio and via depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a via hole is formed in the optical waveguide by laser and filled with conductive material by electroless plating, then electrical connection between electrode terminal and pad is achieved, but the aspect ratio and via depth restrict the arrangement of vias at fine pitches
Solution Approach 1:
The patent divides the via formation process into two stages: first forming a via hole in the first cladding layer and filling it with conductive material to create a conductor portion protruding from the surface, then forming a second via hole in the second cladding layer and filling it to connect to the first conductor portion. This segmentation allows each via stage to have reduced aspect ratio, enabling fine pitch arrangement without electrical conduction failures.
2Ease of manufacture
If the aspect ratio is 1 or lower with via diameter of 50 μm and thickness of 55 μm, then via formation is simplified, but conductive material is insufficiently filled into the via hole causing electrical conduction failure
Solution Approach 1:
The patent segments the via formation into two stages with different aspect ratios. The first via hole has a smaller aspect ratio allowing complete conductive material filling and reliable electrical connection. The second via hole connects to the first conductor portion, ensuring both stages achieve sufficient filling without electrical conduction failure.
Solution Approach 2:
The patent performs preliminary action by forming the first conductor portion that protrudes from the surface of the first cladding layer before forming the second via hole. This preliminary structure ensures that the second via can be filled completely with conductive material, preventing electrical conduction failure while maintaining ease of manufacture.
3Productivity
If conductive vias are arranged at fine pitches, then component density is increased, but the conventional via formation method cannot meet the demand due to aspect ratio restrictions
Solution Approach 1:
The patent segments the via formation process into two stages, allowing each stage to operate with reduced aspect ratio requirements. This enables conductive vias to be arranged at fine pitches while maintaining manufacturing precision, as each via stage can be formed with appropriate dimensional control without the restrictions of conventional single-stage via formation.
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
Enables the arrangement of conductive vias at fine pitches without electrical conduction failures, improving yield rates by allowing higher aspect ratios for each via stage and relaxing patterning accuracy requirements.
Implementation Method 1
the via hole is filled with a conductive material by electroless plating
Data Source
AI summary
A via hole is formed in a first cladding layer laminated on a wiring board. A conductive material is filled in the via hole so as to form a first conductor portion (a portion of a conductive via) having a mushroom-like shape projecting from a surface of the first cladding layer. Then, a second cladding layer is formed to cover the first conductor portion, the first cladding layer and a core layer, and a via hole is formed in the second cladding layer. A conductive material is filled in the via hole so as to form a second conductor portion (a remaining portion of the conductive via) connected to the first conductor portion.