Wiring Board Stepped Portion Perpendicular Traversal
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Solution Overview
Problem
Conventional wiring boards with differential transmission lines experience impedance mismatch and intra skew due to asymmetric and discontinuous cross-sectional shapes at stepped portions, particularly at high frequencies above 20GHz, leading to deteriorated signal quality.
Innovation Solution
The wiring board design ensures that the extending direction of the wirings traversing the stepped portion is perpendicular to the periphery defined by the top and lateral faces of the insulation resin layer, maintaining a consistent cross-sectional shape for both wires, which facilitates continuous and symmetric structure, allowing for accurate characteristic impedance design and minimizing impedance mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the wirings traverse the stepped portion at an oblique angle to connect terminals with different pitches, then the connection between optical device terminals and printed board terminals is achieved, but the cross-sectional shape of the wirings becomes asymmetric and discontinuous, resulting in impedance mismatch and deteriorated transmission property
Solution Approach 1:
The patent applies asymmetry principle in reverse - it deliberately avoids asymmetric wiring configuration by ensuring wirings traverse the stepped portion perpendicular to the periphery, maintaining symmetric cross-sectional shapes. This resolves the impedance mismatch caused by oblique traversal while still achieving pitch conversion between optical device terminals and printed board terminals.
Solution Approach 2:
The patent introduces a specific directional constraint (perpendicular traversal) in the spatial arrangement of wirings relative to the stepped portion. By controlling the traversal direction in the plan view dimension, it maintains cross-sectional symmetry while achieving the required pitch conversion function.
2Use of energy by moving object
If the insulation resin layer is provided only at the other end of the wirings to avoid blocking optical signals, then optical signal transmission is enabled, but the wirings must traverse the stepped portion causing asymmetric cross-sectional shapes
Solution Approach 1:
The patent addresses the asymmetry problem by carefully positioning the insulation resin layer to cover only specific regions. The resin layer is configured to avoid the optical path while providing insulation where wirings traverse the stepped portion perpendicularly, maintaining symmetric cross-sectional shapes and reliable signal transmission.
Data Source
Figure 1A~1B
Figure 2A
Figure 2B~2D
AI summary
A wiring board including: a board; a differential transmission line which is constituted by two wirings disposed on the board in parallel; an insulation resin layer which is formed on part of a face of the board, wherein a stepped portion constituted by a lateral face of the insulation resin layer is formed at a boundary between the face of the board and a top face of the insulation resin layer, the two wirings extend from the face of the board to the top face of the insulation resin layer so as to traverse the stepped portion, and the extending direction of the wirings traversing the stepped portion and the direction of a periphery are perpendicular to each other in a plan view of the board, the periphery being defined by a boundary between the top face of the insulation resin layer and the lateral face of the insulation resin layer constituting the stepped portion.