Disk Drive Flexure Tail Folded Bonding for Electrical Connections
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Solution Overview
Problem
Modern magnetic hard disk drives face challenges in accommodating an increased number of electrical connections due to limited space in the bonding region of contemporary flexure tails, which are exacerbated by the inclusion of flexure bond pads in the conductive layer, leading to increased cost and complexity when a second conductive layer is added to address this issue.
Innovation Solution
The design of a flexure tail with a structural layer that includes flexure bond pads facing the FPC, allowing for a smaller via connection land size, enabling more space for conductive traces and accommodating additional electrical connections without the need for a second conductive layer, utilizing a folded configuration to optimize bonding and reduce the size of bond pads, and employing anisotropic conductive film (ACF) bonding with electrically conductive beads for secure and reliable connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a second conductive layer is added to accommodate more electrical connections, then the number of electrical connections increases, but the cost and complexity of the flexure tail increases
Solution Approach 1:
The patent utilizes the third dimension by folding the flexure tail to create multiple bonding surfaces. Instead of adding a second conductive layer in the same plane, the flexure is folded back on itself, allowing bond pads to be positioned on opposite sides of the folded structure. This enables additional electrical connections to be made to the same conductive layer through spatial arrangement rather than adding more conductive layers.
Solution Approach 2:
The flexure tail is folded back onto itself, creating a nested structure where portions of the flexure are positioned within or adjacent to other portions. This nesting allows multiple bond pads to be in close proximity and enables additional electrical connections without requiring additional conductive layers or increasing the overall footprint of the flexure tail.
2Adaptability or versatility
If the flexure tail size is increased to accommodate more traces, then more electrical connections can be made, but the space available in the bonding region decreases
Solution Approach 1:
By folding the flexure tail, the patent transforms a two-dimensional bonding region into a three-dimensional structure with multiple bonding surfaces. The fold creates additional bonding interfaces without increasing the planar footprint, allowing more electrical connections to be made within the same bonding region area.
Solution Approach 2:
The flexure tail is designed to be flexible and capable of folding, transforming from a rigid linear structure to a dynamic multi-layer configuration. This flexibility allows the same conductive layer to provide multiple bonding surfaces when folded, increasing the number of electrical connections without requiring additional space.
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 allows for an increased number of electrical connections within the existing conductive layer, reducing manufacturing complexity and cost while ensuring reliable and efficient electrical conductivity, thereby enhancing the flexibility and functionality of magnetic hard disk drives.
Implementation Method 1
The flexure tails must be held or constrained against the conductive electrical terminals of the FPC while the aforementioned electrical connections are made by ultrasonic bonding, solder jet bonding, solder bump reflow, or anisotropic conductive film (ACF) bonding.
Data Source
AI summary
A head gimbal assembly has a laminate flexure that includes a metallic conductive layer that includes a plurality of electrically conductive traces that are elongated and narrow and electrically connected to the read head, and a metallic structural layer that is stiffer than the conductive layer. A first dielectric layer is disposed between the structural layer and the conductive layer. A second dielectric layer substantially covers the conductive layer in a flexure tail bonding region that overlaps a flexible printed circuit (FPC). The structural layer includes a plurality of flexure bond pads that are aligned with, facing, and bonded to corresponding FPC bond pads. The flexure bond pads in the structural layer are electrically connected to the electrically conductive traces in the conductive layer by vias through the first dielectric layer. In certain embodiments, the flexure tail is folded upon itself in the flexure tail bonding region.