Ceramic Sub-Plate Mounting for HGA Resonance Testing
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Solution Overview
Problem
Existing head gimbal assembly (HGA) testers exhibit resonance modes within the frequencies of interest, distorting resonance data and requiring improved resonance performance for accurate testing, especially as areal density increases and track sizes shrink.
Innovation Solution
The use of materials with a higher modulus-to-density ratio, such as silicon carbide (SiC), in combination with 440 C stainless steel, to increase the natural frequencies of the system modes, thereby extending the usable test frequency range and reducing resonance modes within the frequencies of interest.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If 440 C stainless steel mounting plate is used, then ferromagnetic mounting is enabled, but resonance modes appear within the frequencies of interest (1-50 KHz)
Solution Approach 1:
The mounting plate is segmented into two distinct layers: a 440 C stainless steel base plate providing ferromagnetic mounting capability, and a silicon carbide sub-plate providing high stiffness and high natural frequencies. This segmentation allows each layer to fulfill its specific function without compromising the other.
Solution Approach 2:
The invention uses a composite structure combining 440 C stainless steel and silicon carbide materials. The steel provides magnetic properties for secure mounting, while the ceramic silicon carbide layer provides high modulus-to-density ratio to push resonance modes above the test frequency range, eliminating interference with measurements.
2Speed
If higher modulus-to-density ratio materials are used, then natural frequencies of system modes increase, but manufacturing complexity increases
Solution Approach 1:
The complex high-performance mounting plate is segmented into two manufacturable layers: a standard 440 C stainless steel base plate that is easy to manufacture and machine, and a silicon carbide sub-plate that can be produced using established ceramic manufacturing techniques. This segmentation makes the high-performance design practically manufacturable.
Solution Approach 2:
The composite structure allows combining materials with different manufacturing characteristics. The silicon carbide sub-plate can be manufactured separately using ceramic processing, then bonded to the steel base plate using conventional adhesive bonding techniques, making the overall structure manufacturable despite using advanced materials.
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 approach allows for more accurate resonance testing by eliminating resonance modes within the 1 KHz to 50 KHz frequency range, ensuring reliable data for HGA performance evaluation.
Implementation Method 1
The use of materials with a higher modulus-to-density ratio, such as silicon carbide (SiC), in combination with 440 C stainless steel, to increase the natural frequencies of the system modes
Implementation Method 2
a piezoelectric device to drive the HGA for resonance testing
Implementation Method 3
The shaker is mounted to the test assembly holder via an electromagnet
Data Source
AI summary
A test assembly for a disk drive suspension head gimbal assembly includes a steel mount plate and a mount sub-plate of a material such as silicon carbide having a modulus of elasticity to density ratio that is significantly higher than the ratio for stainless steel. Preferably the mount plate and the mount sub-plate taken together have a first resonant shear frequency of greater than 50 KHz, which is generally greater than the frequency range of interest for testing head gimbal assemblies. The high modulus of elasticity to density ratio helps to ensure that any shear mode resonances of the test assembly occur at frequencies that are higher than the frequencies of interesting for head gimbal assembly shear resonance testing purposes.