HDD PCB Impedance Balancing via Variable Trace Width
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Solution Overview
Problem
Conventional printed circuit boards in hard disk drives experience signal transmission errors due to impedance imbalances between write and read conductors, caused by differences in coupling capacitances and conductor positions, leading to crosstalk and signal distortion.
Innovation Solution
A printed circuit board design featuring a conductive substrate with alternating wider and narrower wiring traces, each covered by insulating layers, with ground traces on either side to balance impedance and prevent signal errors, ensuring equal induced electromotive forces and reduced crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the distances between write conductors and read conductors are made equal to balance induced electromotive forces, then crosstalk is reduced, but impedance imbalance occurs due to different coupling capacitances with the metal substrate
Solution Approach 1:
The patent applies local quality by making the second wiring trace wider than the first wiring trace in the region where they are arranged opposite to each other. This local variation in trace width compensates for the impedance differences caused by unequal coupling capacitances with the metal substrate, while maintaining equal distances between write and read conductors to prevent crosstalk.
Solution Approach 2:
The patent changes the physical parameter of wiring trace width to adjust impedance characteristics. By increasing the width of the second wiring trace in specific regions, the impedance is modified to compensate for coupling capacitance differences, thereby maintaining signal balance without requiring changes to the overall conductor spacing configuration.
2Reliability
If different wiring trace widths are used to compensate for impedance differences, then signal balance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the wiring trace width variation to specific regions where impedance compensation is needed, rather than making all traces uniform or completely variable. The second insulating layer covers only the necessary portions, allowing precise control of trace widths in critical areas while keeping other regions simple and easy to manufacture.
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 suppresses impedance differences between signal lines, preventing signal transmission errors and ensuring reliable data writing and reading in hard disk drives by maintaining signal balance and reducing crosstalk.
Implementation Method 1
When a write current flows through the write conductors W1, W2, induced electromotive forces are generated in the read conductors R1, R2 by electromagnetic induction in the suspension board 900
Implementation Method 2
a first insulating layer formed on the conductive substrate, a first wiring trace formed on the first insulating layer
Data Source
AI summary
A first insulating layer is formed on a suspension body and a wiring trace is formed on the first insulating layer. In addition, a ground trace is formed on the first insulating layer so as to extend along the wiring trace on one side of the wiring trace with a spacing therebetween. A second insulating layer is formed on the first insulating layer to cover the wiring trace and the ground trace. On the second insulating layer, a wiring trace is formed at a position above the wiring trace. A third insulating layer is formed on the second insulating layer to cover the wiring trace. The width of the wiring trace is set larger than the width of the wiring trace. At least a partial region of the ground trace and at least a partial region of the wiring trace are opposite to each other with part of the second insulating layer sandwiched therebetween.