Disc Drive Suspension Flexure Humidity Expansion Control
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Solution Overview
Problem
The pitch static attitude of disc drive sliders is susceptible to variations due to machining accuracy, temperature changes, and especially humidity changes, particularly in flexures with conductors, which can lead to significant fluctuations.
Innovation Solution
A suspension for a disc drive is designed with a flexure comprising a metal base member, a circuit member with a resin base and conductors, and a resin cover member, where the resin cover member has a lower humidity expansion coefficient than the resin base member, reducing the influence of humidity changes on the slider's pitch static attitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a photosensitive polyimide is used for the resin cover member of the circuit member, then the flexure can be easily manufactured and processed, but the pitch static attitude varies considerably in response to humidity changes
Solution Approach 1:
The patent changes the material parameter (humidity expansion coefficient) of the resin cover member by selecting a polyimide with a lower humidity expansion coefficient than the resin base member. This parameter change ensures that the cover member expands less than the base member when humidity increases, preventing excessive warping and maintaining the pitch static attitude within allowable ranges while still using processable polyimide materials.
Solution Approach 2:
The patent applies different material properties to different parts of the circuit member. The resin base member and resin cover member are made from polyimides with different humidity expansion coefficients, creating a local quality difference that generates a counteracting moment to balance warping effects. This localized material differentiation resolves the contradiction between manufacturability and stability.
2Device complexity
If the resin base member and resin cover member have similar humidity expansion coefficients, then the structure is simpler, but the pitch static attitude varies significantly with humidity changes
Solution Approach 1:
The patent intentionally creates a parameter difference (humidity expansion coefficient) between the resin base member and resin cover member. By selecting materials with different expansion characteristics, the patent transforms a simple uniform structure into a differentiated composite structure that actively compensates for humidity-induced warping, thereby improving stability without excessive complexity.
Solution Approach 2:
The patent uses a composite material structure where the resin base member and resin cover member are made from different polyimide materials with distinct humidity expansion coefficients. This composite approach allows the two layers to interact mechanically, with the differential expansion creating a balancing effect that stabilizes the pitch static attitude against humidity variations.
3Reliability
If a flexure with conductors is used, then electrical connection to the slider is achieved, but the pitch static attitude is more susceptible to humidity changes
Solution Approach 1:
The patent addresses the humidity sensitivity of flexures with conductors by changing the material parameter (humidity expansion coefficient) of the resin cover member. By using a polyimide with a lower humidity expansion coefficient for the cover member compared to the base member, the patent creates a differential expansion behavior that counteracts warping, thereby maintaining pitch static attitude stability while preserving the electrical connection functionality.
Solution Approach 2:
The patent employs a composite material structure for the circuit member, combining resin base member and resin cover member made from different polyimide materials. This composite construction provides both electrical insulation and mechanical stability, with the differential material properties creating a self-balancing effect against humidity-induced deformation, thus resolving the contradiction between electrical reliability and attitude stability.
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 restricts the pitch static attitude of the slider within an allowable range by minimizing changes due to humidity variations, with a difference in humidity expansion coefficients between the resin base and cover members kept at 3 ppm/% RH or less, preventing excessive warping and maintaining performance.
Implementation Method 1
The resin cover member is lower than the resin base member in humidity expansion coefficient
Data Source
AI summary
A suspension for a disc drive includes a base plate, a load beam, and a flexure. The flexure includes a metal base member and a circuit member disposed along the metal base member. The circuit member extends along the load beam. The circuit member includes a resin base member formed of a first polyimide, conductors, and a resin cover member formed of a second polyimide. The resin cover member is lower than the resin base member in humidity expansion coefficient.