Disk Drive Flexure Tail Edge Stiffener Alignment
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Solution Overview
Problem
In high-volume manufacturing of magnetic hard disk drives, there is a need for an improved method to facilitate automated rapid and reliable alignment and electrical connection of conductive traces of flexure tails to conductive electrical terminals on a flexible printed circuit, ensuring proper alignment and uniform pressure during adhesive curing in the bonding process.
Innovation Solution
The design incorporates structural features such as discontinuous bond pad backing islands and edge stiffener islands in the flexure tail terminal regions, which help in aligning and securely attaching the flexure tails to the FPC, allowing for efficient use of anisotropic conductive film bonding, and facilitating the use of automatic tools for alignment and pressure application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If automated bonding equipment is used to bond flexure tails to FPC, then productivity and cost-effectiveness are improved, but alignment precision and uniform pressure application become difficult to achieve
Solution Approach 1:
The flexure tail structure includes built-in alignment features (protrusions on the FPC and corresponding recesses or stiffener islands on the flexure tail) that automatically guide and position the components relative to each other during automated bonding. This self-aligning mechanism eliminates the need for complex external alignment systems while ensuring precise positioning of conductive traces to electrical terminals.
Solution Approach 2:
The alignment features are pre-formed during the manufacturing of the FPC and flexure tail components. The protrusions and recesses are created in advance as integral parts of the components, so that when the components are brought together during bonding, the alignment is automatically achieved without requiring additional alignment steps or complex positioning mechanisms during the bonding process.
2Productivity
If automated bonding equipment is used to bond flexure tails to FPC, then productivity is improved, but uniform pressure application during adhesive curing becomes difficult
Solution Approach 1:
The stiffener islands and alignment features serve a dual function: they provide structural reinforcement for pressure distribution and simultaneously act as self-aligning mechanisms. The rigid stiffener islands create natural contact points that distribute bonding pressure uniformly across the bonding interface, while the alignment features ensure proper positioning, all without requiring complex external pressure control systems.
3Productivity
If multiple bond pads are bonded simultaneously, then productivity is improved, but achieving proper alignment and uniform pressure across all pads becomes more difficult
Solution Approach 1:
The bonding interface is segmented into multiple discrete bonding locations, each with its own alignment features (protrusions and recesses). These segmented alignment features are distributed across the FPC and flexure tail, providing localized alignment control at each bonding position. This allows multiple bond pads to be bonded simultaneously while maintaining proper alignment at each location through the distributed alignment feature network.
Solution Approach 2:
The alignment features and stiffener islands serve multiple functions simultaneously: they provide alignment guidance, structural reinforcement for pressure distribution, and positioning references for multiple bonding locations. This multi-functionality enables simultaneous bonding of multiple pads while maintaining alignment and pressure uniformity across all bonding positions through a single integrated feature system.
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 solution enables fast, cost-effective, and robust bonding of multiple bond pads simultaneously, improving the reliability and efficiency of the electrical connection process in high-volume HSA manufacturing by ensuring precise alignment and uniform pressure application.
Implementation Method 1
The cured adhesive film may conduct electricity via the contacting beads in a direction normal to the bonded surfaces (though may not conduct electricity parallel to the bonded surfaces, since the beads may not touch each other laterally)
Implementation Method 2
the aforementioned electrical connections are made, e.g., by ultrasonic bonding
Data Source
AI summary
A head gimbal assembly for a disk drive includes a flexure tail terminal region having flexure bond pads in electrical communication with the head. Each of the flexure bond pads includes a widened region of a corresponding one of a plurality of electrical traces in a conductive layer, and a discontinuous bond pad backing island in a structural layer that overlaps the widened region. The flexure tail terminal region also includes a plurality of discontinuous edge stiffener islands in the structural layer that do not overlap the widened region of any flexure bond pad, and that are disposed no more than 50 microns from one of the two opposing longitudinal outer edges of the flexure tail terminal region. At least one of the plurality of discontinuous bond pad backing islands is disposed no more than 50 microns from one of the two opposing longitudinal outer edges.