Wiring Substrate Torsion Restrictor for Flying Lead Bonding
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Solution Overview
Problem
The existing techniques for connecting flying leads in hard disk drive flexures to external circuit boards using ultrasonic bonding face issues with physical strength and reliability due to the need for wide reinforcing sections, which compromise extensibility and bonding strength.
Innovation Solution
A wiring substrate design incorporating a torsion restrictor and an easily extensible part, where the torsion restrictor prevents twisting of flying leads during bonding and the extensible part allows the conductor pattern to extend, enhancing bonding reliability and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a wide reinforcing section is provided for the flying lead to enhance physical strength, then the strength of the flying lead is improved, but the extensibility of the flying lead deteriorates and bonding reliability decreases
Solution Approach 1:
The conductor pattern is divided into three functional sections: a narrow flying lead portion for bonding, a wide reinforcing section for strength, and an easily extensible part with reduced width for maintaining extensibility. This segmentation allows each section to perform its specific function optimally without compromising overall reliability.
Solution Approach 2:
Different sections of the conductor pattern are given different local properties: the flying lead has narrow width for extensibility, the reinforcing section has wide width for strength, and the easily extensible part has intermediate width to maintain extensibility while connecting to the reinforcing section. This local differentiation resolves the contradiction between strength and bonding reliability.
2Reliability
If the width of the reinforcing section is limited to maintain extensibility, then the extensibility of the flying lead is preserved, but the physical strength of the flying lead is insufficient
Solution Approach 1:
The conductor pattern is segmented into distinct functional zones including a wide reinforcing section for strength and a narrow easily extensible part for maintaining extensibility. This allows the reinforcing section to be sufficiently wide without compromising the extensibility of the bonding-critical flying lead portion.
Solution Approach 2:
The conductor pattern exhibits varying local widths optimized for different functions: the reinforcing section has maximum width for strength, while the easily extensible part has reduced width to maintain extensibility, and the flying lead has optimized narrow width for bonding performance.
3Ease of manufacture
If the flying lead is made thin and narrow for bonding performance, then the bonding process is feasible, but the physical strength of the flying lead becomes insufficient
Solution Approach 1:
The conductor pattern is divided into a narrow flying lead section for bonding feasibility and a wide reinforcing section for physical strength. The segmentation allows the flying lead to remain thin and narrow for successful ultrasonic bonding while the reinforcing section provides the necessary mechanical strength.
Solution Approach 2:
The conductor pattern has different local widths: the flying lead portion is narrow for bonding performance and the reinforcing section is wide for strength. This local quality differentiation enables both bonding feasibility and physical strength to be satisfied simultaneously.
Data Source
AI summary
A wiring substrate comprises a conductor pattern embedded in an insulating layer, the insulating layer having an opening to expose top and bottom faces of the conductor pattern and define a terminal of the wiring substrate, a torsion restrictor formed in the conductor pattern at a location passing over an edge of the opening, the torsion restrictor restricting torsion of the terminal, and an easily extensible part formed on at least one of the torsion restrictor and a portion of the terminal adjoining the torsion restrictor, the easily extensible part allowing the conductor pattern to longitudinally extend toward the opening.