PCB Radial Pad Group Equal Trace Length Routing
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Solution Overview
Problem
Printed circuit boards (PCBs) in ball grid array (BGA) packages face challenges in preventing signal distortion and maintaining reliability due to the limitations in trace length uniformity and solder ball pad arrangement, which affect the transmission of signals between semiconductor chips and solder balls.
Innovation Solution
The PCB design incorporates radial pad groups with solder ball pads arranged at uniform intervals and traces of equal lengths, where first traces connect to solder ball pads and extend inward, and second traces connect to the inward first traces and outward, ensuring equal total lengths for signal transmission, thereby preventing signal distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional trace routing is used in PCB, then device complexity is reduced, but signal distortion occurs due to unequal trace lengths
Solution Approach 1:
The trace routing is divided into two distinct segments: first traces extending from solder ball pads toward the center region, and second traces extending from the first traces to the outside of the radial pad group. This segmentation allows independent optimization of each trace segment to achieve equal total lengths while maintaining routing simplicity.
Solution Approach 2:
The patent employs asymmetric trace routing where first traces and second traces have different geometric paths but are designed to have equal total lengths. This asymmetric design compensates for the radial arrangement of solder ball pads while ensuring uniform signal transmission characteristics across all channels.
2Area of stationary object
If solder ball pads are arranged in radial direction, then area utilization is improved, but signal transmission uniformity deteriorates due to varying distances from center
Solution Approach 1:
The patent applies local quality by designing different trace configurations for different regions. First traces connect solder ball pads in the radial arrangement to a center region, while second traces extend from there to the outside. This local differentiation ensures that despite the radial arrangement, all signals experience uniform transmission characteristics.
Solution Approach 2:
The patent transitions from direct radial routing to a two-stage routing approach, adding an intermediate dimension (the center region connection point). This dimensional change allows equalization of trace lengths while preserving the compact radial pad arrangement.
3Reliability
If trace lengths are made equal to prevent signal distortion, then signal transmission quality is improved, but routing flexibility is reduced
Solution Approach 1:
The patent employs preliminary action by pre-establishing center region connection points before final trace routing. This preliminary structuring enables equal trace length design while maintaining sufficient routing flexibility for different PCB layouts and applications.
Data Source
AI summary
A printed circuit board (PCB) includes a base substrate including upper and lower surfaces, a plurality of solder ball pads separately formed on the lower surface of the base substrate in a radial direction and forming one or more radial pad groups, a plurality of first traces respectively connected to the plurality of solder ball pads and extending to an inside of the radial pad group, and a plurality of second traces respectively connected to the plurality of first traces and extending to an outside of the radial pad group.