Discrete Ground Staples for QSFP-DD PCB Width Minimization
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Solution Overview
Problem
The existing QSFP-DD module design with a unitary zigzag ground bar limits the minimization of the printed circuit board width due to the large pitch between hidden and exposed passages, making it difficult to densely arrange modules side by side.
Innovation Solution
The use of discrete ground staples instead of a unitary ground bar, with a pitch of 3.38 mm, allows for the efficient arrangement of wires on both surfaces of the printed circuit board, minimizing the board's width by staggering and offsetting the staples to avoid interference and enable dense packing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a unitary zigzag ground bar is used to secure wires, then the ground bar can extend along the transverse direction forming hidden and exposed passages, but the pitch between adjacent passages becomes large (around 3.75 mm), making it difficult to minimize the printed circuit board width
Solution Approach 1:
The unitary ground bar is divided into multiple discrete ground staples spaced at specific intervals. Each ground staple independently secures wires at specific locations, replacing the continuous ground bar structure. This segmentation allows for optimized spacing that reduces the pitch between adjacent wire passages from 3.75 mm to a smaller dimension, thereby minimizing the overall width of the printed circuit board while maintaining wire securing functionality.
2Productivity
If the pitch between hidden and exposed passages is reduced to enable dense module arrangement, then the width of the printed circuit board can be minimized, but the unitary zigzag ground bar structure makes this reduction difficult
Solution Approach 1:
The ground bar is segmented into discrete staples that can be independently positioned and spaced. This segmentation simplifies the overall structure by eliminating the complex zigzag geometry required for a unitary ground bar, allowing for straightforward placement at optimized intervals that enable reduced pitch and denser module arrangement.
Solution Approach 2:
The wire routing is reorganized to utilize both front and rear surfaces of the printed circuit board. Wires connect to the front surface at exposed passages and to the rear surface at hidden passages, effectively using the third dimension (board thickness) to separate wire paths. This dimensional approach allows for reduced horizontal pitch between passages while maintaining proper wire routing and connection.
Data Source
AI summary
The QSFP-DD module has an internal printed circuit board defining a mating port at a front edge region, and a connecting port at a rear edge region, and plural sets of wires mechanically and electrically connected to the connecting port with a plurality of ground staples discrete from one another to secure the respective sets of wires to the printed circuit board. The pitch among the ground staples is essentially 3.38 mm, and the wires are connected to two opposite surfaces of the printed circuit board with the associated ground staples. The staples are arranged in rows along the transverse direction.