Head Suspension Datum Feature for Bond Pad Alignment
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Solution Overview
Problem
Existing head suspension technologies face alignment challenges due to manufacturing tolerances and variations in copper trace and bond pad formation, leading to misalignment of head sliders with respect to bond pads, affecting fly height, static attitude, and electrical interconnections in disk storage devices.
Innovation Solution
The introduction of a datum feature in the electrically conductive layer, such as a circular or V-shaped aperture, which tracks the migration of bond pad edges during etching, ensuring accurate alignment of head sliders with bond pads despite etching-induced positional variations, and the use of alignment structures that remain visible post-installation for precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional alignment methods using reference apertures in stainless steel layers are used, then alignment structures can be formed, but misalignment occurs due to etching-induced migration of copper bond pads relative to the stainless steel reference features
Solution Approach 1:
The patent introduces a datum feature in the copper layer that serves as an intermediary reference between the stainless steel structure and the bond pads. This datum feature migrates with the bond pads during etching, maintaining accurate positional relationships without being affected by the stainless steel-copper layer registration errors. The datum feature acts as a mediator that tracks bond pad position dynamically throughout the manufacturing process.
Solution Approach 2:
The patent changes the reference parameter from fixed stainless steel aperture positions to dynamic copper layer datum feature positions. By forming the datum feature in the copper layer rather than the stainless steel layer, the reference system adapts to etching-induced dimensional changes and bond pad migration, maintaining alignment accuracy despite process variations.
2Ease of manufacture
If multiple manufacturing steps including etching are performed, then electrical interconnections are formed, but bond pad positions vary due to etching-induced migration
Solution Approach 1:
The patent performs preliminary formation of the datum feature in the copper layer before etching operations. This datum feature is positioned relative to the bond pads in advance, so that when etching occurs and bond pads migrate, the datum feature migrates with them, maintaining the positional relationship. This preliminary action establishes a reference that adapts to subsequent process variations.
Solution Approach 2:
The datum feature provides continuous positional feedback about bond pad locations throughout the manufacturing process. By tracking the datum feature's position relative to the stainless steel structure, manufacturers can compensate for etching-induced variations and ensure accurate alignment of head sliders with bond pads, effectively using the datum as a feedback mechanism for process control.
3Productivity
If head sliders are aligned to stainless steel reference apertures, then assembly can proceed, but misalignment with copper bond pads occurs affecting fly height and static attitude
Solution Approach 1:
The datum feature in the copper layer serves as an intermediary alignment reference that eliminates the need for separate stainless steel and copper layer alignment. By aligning head sliders to the datum feature rather than stainless steel apertures, manufacturers achieve direct alignment with bond pads, maintaining both productivity and precision without requiring tight inter-layer registration between stainless steel and copper layers.
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 approach enhances the accuracy of head slider alignment with bond pads, reducing misalignment issues and ensuring high-quality electrical interconnections, while maintaining proper static attitudes and fly heights, thereby improving the reliability of disk storage operations.
Implementation Method 1
The electrically conductive layer is subjected to etching chemicals so that the bond pad edge migrates towards the datum feature first edge and the datum feature first edge migrates away from the bond pad edge at an equal rate
Data Source
AI summary
A head suspension for supporting a head slider over a storage media in a dynamic storage device is provided with a head suspension component having a spring metal layer, an electrically conductive layer and a dielectric layer interposed between the metal layer and the electrically conductive layer. A plurality of electrically conductive traces with bond pads are formed in the electrically conductive layer. A feature datum is also formed in the electrically conductive layer on a detachable carrier strip. The feature datum defines a first edge in the electrically conductive layer parallel to an edge of the bond pads.