HDD Head Suspension Multilayer Ground Flexure
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Solution Overview
Problem
Existing head suspension designs in hard disk drives face challenges in achieving low wiring impedance and wide frequency band on the write side while maintaining high impedance and low transmission loss on the read side due to the low conductivity of stainless-steel substrates, which limits signal transmission efficiency.
Innovation Solution
A high-conductivity ground layer is formed between the substrate and the base insulating layer only on the write wiring side of the head suspension, using copper plating to reduce impedance and transmission loss on the write side and increase impedance on the read side, thereby expanding the frequency band on both sides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a copper ground layer is arranged to entirely cover the width of the stainless-steel substrate, then the wiring impedance on the read side is decreased, but the wiring impedance on the write side cannot be lowered and the frequency band cannot be widened
Solution Approach 1:
The patent applies local quality by forming a copper ground layer only in the write wiring region, rather than covering the entire substrate width. This localized approach allows the write side to benefit from low impedance and wide frequency band while the read side maintains high impedance for proper signal expansion, resolving the contradiction between universal ground coverage and side-specific impedance requirements
2Device complexity
If the stainless-steel substrate is used as the ground layer, then the structure is simple, but the conductivity is low causing large signal transmission loss and narrow frequency band
Solution Approach 1:
The patent uses composite materials by combining the stainless-steel substrate with a copper ground layer in the write wiring region. This composite structure leverages the mechanical properties of stainless steel while utilizing copper's superior conductivity to reduce signal transmission loss and widen the frequency band, overcoming the limitations of using stainless steel alone
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 reduces transmission loss by 30-50% and increases the frequency band by 60-170% on the write side, while maintaining low transmission loss and wide frequency band on the read side, effectively addressing the impedance and frequency band limitations of previous designs.
Implementation Method 1
a ground layer having a higher conductivity than a substrate of a flexure of the head suspension between the substrate and a base insulating layer of the flexure only on the write wiring side
Implementation Method 2
using copper plating to reduce impedance and transmission loss on the write side
Data Source
AI summary
A head suspension includes a load beam to apply load onto a head that writes and reads information to and from the hard disk and a flexure attached to the load beam and supporting the head. The flexure has write wires and read wires connected to the head. The flexure includes a substrate made of a conductive thin plate, a base insulating layer made of flexible resin and formed on the substrate, and the wires are arranged on the base insulating film. A ground layer is formed at least partly between the substrate and the base insulating layer. The ground layer only corresponds to the write wires in a width direction of the flexure. The conductivity of the ground layer is higher than that of the substrate that is made of a conductive thin plate.