Monolithic Standoff Absorbs Adhesive Strain in HDD Slider
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Solution Overview
Problem
The assembly process and thermal changes in hard disk drives cause undesirable deformation of the head slider due to adhesive shrinkage and differing thermal expansion properties of materials, leading to non-trivial alterations in slider flying height.
Innovation Solution
A head gimbal assembly with a flexure and a standoff structure featuring a monolithic element that absorbs strain energy from adhesive curing, reducing deformation by surrounding the monolithic element with adhesive and strategically positioning it to mitigate stress and strain from adhesive shrinkage and thermal changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is used to adhere the head slider to the suspension, then the head slider can be securely attached, but the adhesive shrinkage during curing causes deformation of the head slider
Solution Approach 1:
A compliant layer is introduced between the head slider and suspension as an intermediary element. This layer absorbs the shrinkage stress generated during adhesive curing, preventing direct transmission of deformation forces to the head slider while maintaining secure attachment
Solution Approach 2:
The adhesive formulation is modified to change its curing characteristics, specifically using low-shrinkage epoxy adhesives that minimize volume change during curing, thereby reducing the shrinkage forces that cause slider deformation
2Adaptability or versatility
If materials with different thermal expansion properties are used in the assembly, then design flexibility is improved, but thermal changes cause slider crown deformation
Solution Approach 1:
The suspension structure incorporates elements with matched thermal expansion coefficients to the head slider materials. This ensures that during thermal cycling, all components expand and contract at similar rates, preventing differential expansion forces that would cause slider crown deformation
Solution Approach 2:
The compliant layer serves as a thermal stress mediator that decouples the thermal expansion differences between dissimilar materials. It absorbs thermal expansion mismatches through its elasticity, preventing transmission of thermal stresses to the head slider
3Reliability
If the adhesive is applied in large amounts to ensure proper bonding, then bond reliability is improved, but the shrinkage energy and deformation increase
Solution Approach 1:
The adhesive formulation is changed to a low-shrinkage epoxy that maintains high bond reliability with minimal shrinkage. This chemical parameter change allows adequate bonding strength with reduced shrinkage energy
Solution Approach 2:
The compliant layer acts as a stress-absorbing intermediary that permits using sufficient adhesive for reliable bonding without transmitting excessive shrinkage forces to the slider
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
The solution effectively inhibits deformation of the head slider, maintaining consistent flying height and reducing both delta crown and thermal crown issues, thereby enhancing the reliability and performance of hard disk drives.
Implementation Method 1
the monolithic element may absorb strain energy caused by curing of the adhesive
Implementation Method 2
A head slider in which a read-write head is housed is adhered to the flexure with an adhesive
Implementation Method 3
a standoff structure extending from the planar surface, where the standoff structure includes a monolithic element
Data Source
AI summary
A head gimbal assembly for a hard disk drive comprises a flexure having a planar surface and a standoff structure extending from the planar surface, where the standoff structure includes a monolithic element. A head slider in which a read-write head is housed is adhered to the flexure with an adhesive, such that the adhesive surrounds the monolithic element so that the monolithic element may absorb strain energy caused by curing of the adhesive.