Flexure Tail Segmentation for Uniform ACF Bonding Pressure
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Solution Overview
Problem
In high-volume manufacturing of magnetic hard disk drives, maintaining uniform pressure across multiple bond pads during the electrical connection of flexure tails to flexible printed circuits is challenging, leading to inefficiencies in bonding processes like anisotropic conductive film (ACF) bonding.
Innovation Solution
The design of flexure tails with widened regions and discontinuous islands allows for increased thickness at bond pads, enabling uniform heat and pressure application using a non-patterned thermode tool, facilitating reliable electrical connections across multiple bond pads simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tool presses only upon a single bond pad to maintain uniform pressure during ACF bonding, then bonding quality is improved, but manufacturing productivity deteriorates due to sequential bonding of multiple bond pads
Solution Approach 1:
The flexure tail is segmented with discontinuous structural layer islands positioned at each bond pad location. Each island acts as an independent pressure transmission point, allowing a distributed tool to apply uniform pressure across multiple bond pads simultaneously while maintaining the quality control achieved with single-point pressing.
Solution Approach 2:
The structural layer islands serve as intermediaries between the bonding tool and the bond pads. These islands concentrate and transmit pressure from the tool to the adhesive layer and conductive beads, ensuring uniform pressure distribution across multiple bond pads without requiring complex tooling for each individual pad.
2Reliability
If existing HGA designs are used with single bond pad pressing tools, then uniform bonding pressure is achieved, but bonding time increases significantly in high-volume manufacturing
Solution Approach 1:
The flexure tail structure is divided into discrete segments (islands) at each bond pad location. This segmentation enables a multi-point pressing tool to apply uniform pressure to multiple bond pads simultaneously, reducing the bonding cycle time from sequential single-pad pressing to parallel multi-pad bonding while maintaining pressure uniformity.
Solution Approach 2:
The invention changes the physical parameters of the flexure tail by adding discontinuous structural layer islands that increase local thickness at bond pad positions. This parameter change enables effective pressure transmission and uniform bonding across multiple pads simultaneously, transforming the bonding process from a time-consuming sequential operation to an efficient parallel operation.
3Productivity
If flexure tails with increased thickness at bond pads are designed, then uniform heat and pressure application is enabled for simultaneous multi-pad bonding, but manufacturing complexity increases
Solution Approach 1:
The flexure tail is designed with local quality variations: discontinuous structural layer islands are added only at specific bond pad locations where increased thickness is needed for pressure and heat application. The rest of the flexure tail maintains its original thin, flexible structure. This localized modification achieves the desired bonding capability without significantly increasing overall manufacturing complexity.
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 design enhances the uniformity of bonding pressure and heat transfer, improving the efficiency and reliability of electrical connections in high-volume manufacturing, reducing the time and cost associated with bonding processes.
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
enabling uniform heat and pressure application using a non-patterned thermode tool
Data Source
AI summary
A head gimbal assembly for a disk drive includes a read head and a suspension assembly. The suspension assembly includes a load beam and a laminate flexure. The laminate flexure includes a structural layer, a dielectric layer, and a conductive layer that includes a plurality of electrical traces. The laminate flexure includes a tongue portion that connects to the read head and a flexure tail that extends away from the tongue portion. The flexure tail includes a plurality of flexure bond pads. Each of the plurality of flexure bond pads includes a widened region of a corresponding one of the plurality of electrical traces in the conductive layer, and a corresponding one of a plurality of segments or discontinuous islands in the structural layer.