Multilayer Substrate Differential Pair Width Adjustment
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Solution Overview
Problem
In multilayer substrates, differential signal transmission lines often experience phase deviations, leading to impaired signal recovery and increased noise due to variations in transmission time and impedance, which existing layouts attempt to mitigate by equalizing physical lengths but result in impedance mismatches and signal quality deterioration.
Innovation Solution
The solution involves maintaining a constant interval between differential pair lines while varying their widths, with the shorter line having a thicker width than the longer line, adjusting their electrical lengths to match signal transmission speeds and retain constant impedance, thereby reducing signal transmission time differences and impedance mismatches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the physical lengths of differential pair lines are equalized, then signal transmission time differences are reduced, but impedance mismatches occur and signal quality deteriorates
Solution Approach 1:
The patent applies local quality by making the width of each line in the differential pair different according to its specific position and length characteristics. The shorter line has a greater width than the longer line, creating localized property variations that compensate for length differences while maintaining overall signal quality and constant impedance throughout the transmission path.
2Ease of manufacture
If the widths of differential pair lines are made equal, then manufacturing is simplified, but signal transmission speeds differ and differential characteristics deteriorate
Solution Approach 1:
The patent deliberately introduces asymmetry by setting different widths for the two lines in the differential pair. The shorter line has a greater width than the longer line, creating an asymmetric configuration that compensates for length differences and equalizes electrical characteristics, thereby improving signal transmission reliability while maintaining manufacturing feasibility.
3Area of stationary object
If the interval between differential pair lines is reduced, then space is saved, but impedance control becomes difficult and signal integrity is compromised
Solution Approach 1:
The patent applies parameter changes by adjusting the width parameter of each line in the differential pair to compensate for spacing variations. By making the shorter line wider than the longer line, the patent maintains constant impedance and signal integrity even when the interval between lines is reduced, thereby optimizing space utilization without compromising reliability.
Data Source
AI summary
According to one embodiment, there is provided a multilayer substrate including a signal layer. The signal layer includes a first line and a second line which form a differential pair. The first line electrically connects a first node and a second node in the signal layer. The second line electrically connects a third node and a fourth node in the signal layer. The interval between the first line and the second line is approximately constant from the first node to the second node. A physical length from the third node to the fourth node in the second line is shorter than a physical length from the first node to the second node in the first line. A width of the second line is thicker than a width of the first line.