Disk Drive Head Suspension Branched Limiter Shock Robustness
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Solution Overview
Problem
Modern magnetic hard disk drives face challenges in withstanding severe mechanical shocks during non-operating conditions, which can cause cracking of electrical connections between the read head and conductive traces of the head gimbal assembly (HGA) flexure, leading to potential catastrophic data loss and failure.
Innovation Solution
The design incorporates piezoelectric elements and structural features such as proximate and distal limiters in the laminated flexure of the HGA, which help distribute stress and prevent excessive separation of the tongue from the load beam during mechanical shocks, thereby reducing the maximum stress on electrical connections and enhancing robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the head suspension assembly uses a traditional laminated flexure structure, then the electrical connections are simple and manufacturing is easier, but the structure cannot withstand severe mechanical shocks during non-operating conditions, leading to cracking of electrical connections
Solution Approach 1:
The distal limiter arm is segmented into multiple branches that extend toward the tongue, creating a distributed stress field. This segmentation allows the structure to absorb shock forces through multiple contact points rather than concentrating stress at a single location, thereby preventing cracking of electrical connections while maintaining structural integrity.
Solution Approach 2:
The limiter arm extends in a direction substantially perpendicular to the tongue, adding a spatial dimension to the shock limitation mechanism. This perpendicular arrangement creates a branched structure that distributes forces across multiple dimensions, enhancing the ability to withstand severe mechanical shocks without increasing overall flexure complexity.
2Reliability
If shock limiters are added to the head suspension assembly, then mechanical shock robustness is improved, but the mass of the flexure increases
Solution Approach 1:
The shock limiter functionality is merged with the existing distal limiter arm structure of the laminated flexure. By integrating the shock limitation capability into the existing flexure geometry rather than adding separate components, the design achieves enhanced mechanical shock robustness without proportionally increasing the overall mass of the moving assembly.
Solution Approach 2:
The limiter arm is constructed as a thin, flexible structure that is substantially perpendicular to the tongue. This thin-film approach provides shock limitation functionality while minimizing added mass, as the flexible nature of the structure allows it to absorb shock forces without requiring heavy material.
3Stress or pressure
If the distal limiter arm is positioned closer to the tongue, then stress distribution is improved, but the available space for electrical connections is reduced
Solution Approach 1:
The limiter arm employs asymmetric branching, with multiple branches extending toward the tongue at different positions and angles. This asymmetric configuration optimizes stress distribution by directing forces away from critical connection areas while maintaining effective shock limitation. The branches are strategically positioned to create optimal stress patterns without encroaching on electrical connection space.
Data Source
AI summary
A head suspension assembly for a disk drive includes a load beam extending from a load beam supported end to a load beam distal end, and a laminated flexure supported by the load beam. The laminated flexure includes a structural layer having a head mounting tongue, a conductive layer having a plurality of patterned traces, and a dielectric layer between the structural layer and the conductive layer. The structural layer of the laminated flexure includes a distal limiter that has a first limiter arm and a second limiter arm adjoining at a distal apex. The distal apex is disposed closer to the load beam distal end than is the head mounting tongue. Each of the first and second limiter arms splits into a plurality of branches.