Flexure Tail Bond Pad Geometry for Dual Ultrasonic and ACF Bonding
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Solution Overview
Problem
Current disk drive head gimbal assembly designs are not adaptable for both ultrasonic bonding and anisotropic conductive film (ACF) bonding, limiting manufacturing flexibility as different designs are required for each method, and there is a need for a design that can facilitate both bonding processes during head stack assembly manufacturing.
Innovation Solution
The design of the flexure tail includes widened bond pads that accommodate both ultrasonic bonding and ACF bonding, with specific geometries and materials that ensure adequate conductivity and alignment for either method, featuring a structural layer, dielectric layer, and conductive traces with gold plating, allowing for either intimate gold contact or anisotropic conductive beads to establish electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the flexure tail is designed for ultrasonic bonding with small contact pads, then ultrasonic bonding is facilitated, but ACF bonding requires larger bond pads for adequate conductivity
Solution Approach 1:
The bond pad is designed with a larger area than traditionally required for ultrasonic bonding alone, enabling the same pad to accommodate both ultrasonic bonding tools and ACF bonding processes. This universal design allows the flexure tail to be manufactured using either bonding method without requiring different pad geometries, thereby resolving the contradiction between optimizing for ultrasonic bonding while maintaining ACF bonding compatibility.
2Adaptability or versatility
If the bond pad area is increased for ACF bonding, then ACF bonding is facilitated, but ultrasonic bonding tool tip contact area is reduced
Solution Approach 1:
The bond pad is designed with a larger area than traditionally required for ultrasonic bonding alone, enabling the same pad to accommodate both ultrasonic bonding tools and ACF bonding processes. This universal design allows the flexure tail to be manufactured using either bonding method without requiring different pad geometries, thereby resolving the contradiction between optimizing for ultrasonic bonding while maintaining ACF bonding compatibility.
3Reliability
If different flexure tail designs are used for different bonding methods, then each bonding method is optimized, but manufacturing process complexity increases
Solution Approach 1:
The bond pad is designed with a larger area than traditionally required for ultrasonic bonding alone, enabling the same pad to accommodate both ultrasonic bonding tools and ACF bonding processes. This universal design allows the flexure tail to be manufactured using either bonding method without requiring different pad geometries, thereby resolving the contradiction between optimizing for ultrasonic bonding while maintaining ACF bonding compatibility.
Solution Approach 2:
The design merges the requirements of both ultrasonic bonding and ACF bonding into a single bond pad geometry. By combining the features needed for both bonding methods (sufficient area for ACF beads and adequate contact for ultrasonic tools), the patent eliminates the need for separate design variants, thereby reducing manufacturing process complexity while maintaining bonding reliability.
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 enables the same head gimbal assembly to be bonded using either ultrasonic bonding or ACF bonding, enhancing manufacturing flexibility and ensuring reliable electrical connections, accommodating various manufacturing tolerances and alignment variations.
Implementation Method 1
Such electrical connections may be made by ultrasonic bonding, which is a process during which ultrasonic wave energy is applied by a tool tip that presses upon bond pads of the flexure tail, to cause a gold plating on the flexure tail bond pads to join another gold plating upon the electrical terminals of the FPC.
Implementation Method 2
An anisotropic conductive film is typically an adhesive doped with conductive beads or cylindrical particles of uniform or similar diameter. As the doped adhesive is compressed and cured, it is squeezed between the surfaces to be bonded with sufficient uniform pressure that a single layer of the conductive beads makes contact with both surfaces to be bonded. The cured adhesive film may conduct electricity via the contacting beads in a direction normal to the bonded surfaces.
Data Source
AI summary
A head gimbal assembly for a disk drive includes a read head, 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 and includes a plurality of flexure bond pads that may facilitate ultrasonic or ACF bonding. Each of the plurality of flexure bond pads consists of a widened region of a corresponding one of the plurality of electrical traces in the conductive layer, and a gold coating upon the widened region. The widened region of each of the plurality of electrical traces extends transverse to the flexure tail's longitudinal axis at least 2.5 times more than it extends parallel to the flexure tail's longitudinal axis.