Disk Drive Head Suspension Flexure Ground Feature Miniaturization
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Solution Overview
Problem
Existing disk drive head suspension flexures require large plated ground features to accommodate layer-to-layer misregistration, which occupies excessive space and hinders miniaturization.
Innovation Solution
The use of a polymer covercoat to cover the plated ground feature and surrounding region, allowing for smaller ground features by accommodating misregistrations and exposing stainless steel regions, with the covercoat ensuring coverage of apertures and preventing corrosion through selective plating of trace portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large plated ground features are used to accommodate layer-to-layer misregistration, then reliable electrical connections are maintained, but the space occupied by ground features increases excessively
Solution Approach 1:
A polymer covercoat layer is introduced as an intermediary element between the plated ground feature and the environment. This covercoat serves multiple functions: it protects the plated ground feature from corrosion, accommodates misregistrations between layers, and allows for smaller ground feature dimensions while maintaining electrical connection reliability. The covercoat acts as a mediator that enables the system to achieve both reliability and miniaturization.
Solution Approach 2:
The invention changes the physical and chemical parameters of the ground feature system by applying a polymer covercoat. This parameter change enables the ground feature to be smaller in size while maintaining its functional integrity. The covercoat modifies the surface properties and protective characteristics, allowing the ground feature to accommodate misregistrations and resist corrosion without requiring excessive size.
2Reliability
If plated ground features are made larger to cover apertures and accommodate misregistration, then electrical interconnection is ensured, but miniaturization of the assembly is hindered
Solution Approach 1:
The polymer covercoat serves as a mediator that enables smaller ground features while maintaining electrical interconnection reliability. It protects the plated ground feature and accommodates misregistrations, allowing the assembly to be miniaturized without compromising the electrical interconnection between traces and the stainless steel layer.
Solution Approach 2:
The polymer covercoat is implemented as a thin film layer that provides protective and functional benefits. This thin film accommodates misregistrations and protects the plated ground feature, enabling the ground feature to be smaller in size while ensuring reliable electrical interconnection and corrosion resistance.
3Object-affected harmful factors
If non-corrosive materials like NiAu are plated on copper traces, then corrosion resistance is improved, but adhesion to stainless steel deteriorates
Solution Approach 1:
The polymer covercoat acts as an intermediary layer that separates the plated ground feature from the environment, providing corrosion protection without requiring the plated material to adhere to the stainless steel. This intermediary approach allows the use of non-corrosive plating materials on copper traces while maintaining adhesion through the trace structure rather than relying on plating adhesion to the stainless steel.
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
Enables the reduction of ground feature size, allowing for more compact designs and improved miniaturization of disk drive assemblies while maintaining reliable electrical connections and corrosion resistance.
Implementation Method 1
The ground feature and the region surrounding the ground feature can be covered by polymer covercoat material
Implementation Method 2
These ground features are, for example, used to electrically interconnect the traces though apertures in the dielectric insulating layer to the underlying stainless steel layer
Implementation Method 3
The copper or other conductive material of the traces to which the ground features are connected are often plated with relatively non-corrosive materials such as NiAu (nickel-gold)
Data Source
AI summary
Various embodiments concern an electrical interconnect of a head suspension. The electrical interconnect can comprise a spring metal layer and a dielectric layer having an aperture with a portion of the spring metal layer being exposed through the dielectric layer within the aperture. The electrical interconnect can further comprise a trace layer disposed on the dielectric layer and extending into the aperture to connect with the spring metal layer. Part of the spring metal layer within the aperture may not be covered by the trace layer. The exposure of the spring metal layer through the aperture can be due to the width of the trace layer being less than the width of the aperture and/or the exposure can be due to expected misregistration. A polymer covercoat can be applied over the aperture to protect the trace layer from corrosion.