PCB Signal Trace Width Asymmetry for Impedance Balancing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional printed circuit boards in hard disk drives experience signal transmission errors due to impedance imbalances caused by differences in coupling capacitances between conductors and the metal substrate, leading to crosstalk and transmission errors in differential signals.
Innovation Solution
A printed circuit board design with specific configurations of insulating layers and wiring trace widths, where the second wiring trace has a larger width than the first, ensuring equal capacitances and impedances between the traces and the conductive substrate, thereby preventing signal transmission errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the distances between write conductors and read conductors are made equal to prevent crosstalk, then crosstalk is reduced, but the distances between individual conductors and the metal substrate become different, causing impedance imbalance
Solution Approach 1:
The patent applies local quality by making the second wiring trace wider than the first wiring trace. This local variation in trace width compensates for the different distances to the ground conductor, ensuring that both traces in the differential pair have equal characteristic impedance despite their different positions relative to the ground plane.
Solution Approach 2:
The patent changes the physical parameter of trace width to control impedance. By adjusting the width of the second wiring trace to be larger than the first, the patent balances the coupling capacitance differences caused by unequal distances to the ground conductor, thereby achieving equal characteristic impedance for both traces in the differential pair.
2Reliability
If different wiring trace widths are used to balance impedance, then signal transmission accuracy is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent intentionally introduces asymmetry in the wiring trace widths of the differential pair. The second wiring trace is designed with a larger width than the first wiring trace, creating an asymmetric structure that compensates for the asymmetric positioning relative to the ground conductor and achieves symmetric electrical characteristics (equal impedance).
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
This configuration effectively prevents signal transmission errors by balancing the impedances of the signal line pairs, ensuring reliable data transmission during writing and reading operations in hard disk drives.
Implementation Method 1
the coupling capacitance between the write conductor W1 and the metal substrate 902 is different from the coupling capacitance between the write conductor W2 and the metal substrate 902
Data Source
AI summary
A first insulating layer is formed on a suspension body, and a write wiring trace and a read wiring trace are formed on the first insulating layer. A second insulating layer is formed on the first insulating layer so as to cover the wiring traces. A write wiring trace and a read wiring trace are formed on the second insulating layer. A third insulating layer is formed on the second insulating layer so as to cover the wiring traces. The width of the wiring trace is larger than the width of the wiring trace, and the width of the wiring trace is larger than the width of the wiring trace.