Disk Drive Flexure Jumper Placement for Uniform ACF Bonding
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Solution Overview
Problem
In magnetic hard disk drives, the connection of flexure tails to flexible printed circuits (FPCs) using anisotropic conductive film (ACF) bonding can be compromised by the presence of jumpers, leading to non-uniform pressure and heat distribution, which may result in undesirable shorting and connection issues.
Innovation Solution
The design incorporates discontinuous jumper islands and bonding islands in the flexure tail terminal regions, allowing for increased thickness at bond pad locations, enabling uniform heat and pressure application using a non-patterned thermode tool, and strategically positioning jumpers to avoid overlap with FPC traces and bond pads, thereby enhancing connection uniformity and reducing the risk of shorting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If jumpers are present in the flexure tail terminal region, then electrical connection flexibility is improved, but pressure and heat distribution uniformity deteriorates
Solution Approach 1:
The flexure tail terminal region is segmented into bonding islands and jumper islands. The bonding islands are positioned to receive uniform pressure and heat from the thermode tool, while jumper islands are separated and positioned away from the bonding area. This segmentation allows independent optimization of bonding uniformity and electrical connection flexibility.
Solution Approach 2:
Different regions of the flexure tail terminal region are assigned different functions and properties. The bonding islands have properties optimized for uniform pressure and heat reception, while the jumper islands are positioned and sized to provide electrical connection flexibility without interfering with the bonding process. This local differentiation resolves the contradiction between uniformity and flexibility.
2Area of stationary object
If jumpers are positioned close to bond pads, then space utilization is improved, but risk of shorting increases
Solution Approach 1:
The jumpers are extracted from the bonding area and positioned in separate jumper islands away from the bond pads. This spatial separation eliminates the risk of shorting between jumpers and bond pads while still utilizing the flexure tail terminal region effectively for electrical connections.
Solution Approach 2:
The jumper islands act as intermediary structures that provide electrical connection functionality without directly contacting the bond pads. This intermediary positioning allows space utilization while preventing harmful shorting through physical separation.
3Ease of manufacture
If non-patterned thermode tool is used, then manufacturing complexity is reduced, but bonding uniformity becomes difficult to achieve
Solution Approach 1:
The bonding islands are designed with uniform properties and positioning to receive homogeneous pressure and heat distribution from the non-patterned thermode tool. This homogeneity in bonding island design enables simple tools to achieve uniform bonding results.
Solution Approach 2:
The bonding islands are positioned and sized to automatically receive uniform pressure and heat from the thermode tool without requiring complex tool patterning. The structure itself facilitates uniform bonding, making the manufacturing process simpler while maintaining precision.
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 ensures more consistent and reliable electrical connections by maintaining uniform pressure and heat distribution during bonding, even with jumpers present, and reduces the risk of incidental shorting, facilitating improved manufacturing efficiency and reliability.
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 necessarily conduct electricity parallel to the bonded surfaces, since the beads may not touch each other laterally)
Implementation Method 2
the aforementioned electrical connections may employ a type of anisotropic conductive film (ACF) bonding. As the doped adhesive is compressed and cured, it is heated and squeezed between the surfaces to be bonded
Implementation Method 3
the doped adhesive is compressed and cured, it is heated and squeezed between the surfaces to be bonded with sufficient uniform pressure
Data Source
AI summary
A head stack assembly (HSA) for a disk drive includes a flexible printed circuit (FPC). The FPC includes a plurality of electrically conductive FPC traces, each leading to a respective one of a plurality of FPC bond pads. The HSA also includes a head gimbal assembly (HGA) having a laminated flexure with a plurality of electrically conductive flexure bond pads that are bonded to the plurality of FPC bond pads. The laminated flexure includes a flexure tail having an overlap region that overlaps the FPC. A structural layer of the laminated flexure includes a jumper in the overlap region. The jumper is electrically connected to at least two of the plurality of flexure electrical traces in the flexure conductive layer. The jumper is disposed at least 50 microns from any of the plurality of FPC electrical traces or FPC bond pads.