Windowed Spring Metal and Coverlay for Integrated Lead Flexures
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Solution Overview
Problem
Integrated lead or wireless disk drive head suspensions face challenges in achieving improved signal performance due to electrical coupling between thin insulating layers and spring metal layers, which affects signal performance characteristics.
Innovation Solution
The design includes a spring metal layer with windows adjacent to traces and a coverlay with corresponding windows, optimizing signal performance by reducing parasitic capacitance and enhancing high-frequency characteristics, while maintaining efficient manufacturing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a thin insulating layer is used to separate the spring metal layer and conductor layer, then the device structure is compact and manufacturing is simplified, but electrical coupling occurs between the layers which degrades signal performance
Solution Approach 1:
The patent removes portions of the spring metal layer to create windows adjacent to the conductor traces. This extraction eliminates the source of parasitic capacitance in those regions, thereby reducing electrical coupling between the spring metal layer and conductor layer while maintaining the thin insulating layer structure.
Solution Approach 2:
The spring metal layer is configured with varying local properties - it is present in some regions and removed in others (windows) adjacent to traces. This local modification reduces parasitic capacitance where it most impacts signal performance while preserving the ground plane function in other areas.
2Reliability
If holes are drilled through the spring metal layer below conductors to reduce parasitic capacitance, then signal performance improves, but manufacturing complexity and cost increase
Solution Approach 1:
The windows are created in the spring metal layer during the photolithography and etching processes that form the flexure structure itself, before final assembly. This preliminary action integrates the parasitic capacitance reduction into the base manufacturing process rather than requiring separate post-processing steps like drilling holes.
Solution Approach 2:
The formation of windows in the spring metal layer is merged with the existing photolithography and etching processes used to create the flexure structure. This combines multiple functions into a single manufacturing sequence, avoiding the need for separate hole-drilling operations.
3Reliability
If coverlay is removed from between adjoining conductive lines to reduce capacitance, then high-frequency characteristics improve, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses the insulating layer as an intermediary structure that defines the boundaries of both the conductor traces and the coverlay windows. By aligning coverlay windows with the insulating layer features rather than directly with conductor traces, manufacturing precision requirements are reduced since the insulating layer serves as a readily available alignment reference.
Data Source
AI summary
An integrated lead flexure having a spring metal layer, a dielectric insulating layer on a side of the spring metal layer, a conductor layer on the side of the insulating layer opposite the spring metal layer and a coverlay on the side of the conductor layer opposite the insulating layer. The flexure further includes base region, a gimbal region extending from the base region, and a tail region extending from the base region opposite the gimbal region. The conductor layer includes terminal pads at the tail region and head bond pads at the gimbal region. Traces in the conductor layer extend between the terminal pads and the head bond pads across the tail, base and gimbal regions. One or more spring metal windows in the spring metal layer at the tail region are adjacent to substantial portions of at least some of the traces. One or more coverlay windows in the coverlay at the tail region are adjacent to substantial portions of the tail region spring metal windows.