Integrated Lead Suspension Ground Plane Structure
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Solution Overview
Problem
Integrated lead suspensions in disk drives face challenges in achieving high signal performance due to the coupling of traces and ground planes, primarily because of the thin dielectric layer, which affects signal characteristics, especially at high frequencies, and existing solutions are not efficiently manufacturable.
Innovation Solution
A multiple-layer, high conductivity ground plane structure is created by forming second conductive ground planes on a stainless steel base, followed by forming first conductive ground planes, an insulating layer, and traces, with voids created in the stainless steel base using the second conductive ground planes as etch stops, enhancing manufacturing efficiency and signal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thin dielectric layer is used to separate traces from the ground plane, then the device structure is simplified and manufacturing is easier, but signal performance deteriorates due to coupling between traces and ground plane
Solution Approach 1:
The ground plane is segmented into multiple layers: a stainless steel base layer and additional conductive ground plane layers formed thereon. This segmentation allows the thin dielectric layer to be maintained for manufacturing simplicity while the multi-layer ground plane structure compensates for signal performance by providing better electrical characteristics and reduced coupling effects.
Solution Approach 2:
The invention uses a composite ground plane structure combining stainless steel base layer with additional conductive materials deposited thereon. This composite approach maintains the mechanical properties and thin profile needed for ease of manufacture while enhancing the electrical properties to improve signal performance through controlled impedance and reduced parasitic effects.
2Reliability
If holes are drilled through the stainless steel layer to reduce parasitic capacitance, then signal performance is improved, but manufacturing complexity increases
Solution Approach 1:
Instead of modifying the stainless steel layer by drilling holes (vertical modification), the invention adds conductive ground plane layers in another dimension (horizontal layering) on top of the existing stainless steel base. This dimensional approach reduces parasitic capacitance and improves signal performance without requiring complex hole-drilling and filling operations.
3Productivity
If a shield is formed by electro-deposition to improve signal performance, then manufacturing efficiency is maintained, but the structure becomes more complex
Solution Approach 1:
The conductive ground plane layers formed by electro-deposition serve multiple functions simultaneously: they act as shields for signal traces, provide additional ground plane area for impedance control, and function as part of the overall ground plane structure. This multi-functionality improves signal performance and maintains manufacturing efficiency without requiring separate dedicated shield structures.
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
The solution reduces impedance and improves signal transmission performance by making impedance more uniform, enhancing peak current capacity, bandwidth, and rise times without compromising mechanical functionality, and allows for efficient manufacturing processes.
Implementation Method 1
forming voids in void portions of the stainless steel base layer using the first etchant and the second conductive ground planes as etch stops
Data Source
AI summary
Multi-layer ground plane structures and methods of manufacture for integrated lead suspension flexures. A flexure in accordance with one embodiment of the invention includes an insulating layer, a plurality of traces on the insulating layer and a stainless steel base layer on the side of the insulating layer opposite the traces. The stainless steel base layer includes one or more void portions with voids in the base layer opposite the insulating layer from the traces and one or more backed portions with the base layer backing the traces. A plurality of patterned and transversely-spaced first conductive ground planes are located opposite the insulating layer from the traces at the void portions and backed portions of the stainless steel base layer. A continuous gold second conductive ground plane is located opposite the insulating layer and the first ground planes from the side of the insulating layer adjacent to the traces at the void portions and backed portions of the stainless steel base layer. The gold ground plane can be used as an etch stop during formation of the voids in the base layer.