HDD Feedthrough Mounting Surface Width Variation for Thermal Stress
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Solution Overview
Problem
Hermetically sealing low-density gases like helium in hard disk drives (HDDs) is challenging due to poor sealing reliability at solder joints, which leads to helium leakage and thermal stress issues, affecting the device's performance and reliability.
Innovation Solution
The solution involves modifying the feedthrough mounting surface by varying its width to manage thermal stress, with increased width at areas of high stress and decreased width at areas of low stress, and adjusting solder thickness and joint locations to enhance sealing reliability and prevent crack formation and solder overflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the feedthrough is solder-jointed to the base with a fixed width mounting surface, then the manufacturing process is simple, but the solder joint reliability is insufficient due to thermal stress from helium sealing
Solution Approach 1:
The mounting surface width is varied locally across different regions: the first region has a larger width to accommodate high thermal stress areas, while the second region has a smaller width for low stress areas. This local differentiation optimizes solder joint reliability without requiring complete redesign of the entire mounting surface.
Solution Approach 2:
The mounting surface is divided into multiple regions with different width characteristics. This segmentation allows each region to be optimized independently for its specific thermal stress conditions, improving overall solder joint reliability while managing complexity through modular design.
2Reliability
If the mounting surface width is increased to reduce thermal stress, then solder joint reliability improves, but solder overflow and short circuit risk increase
Solution Approach 1:
The mounting surface width is differentiated by region: the first region with larger width is positioned where thermal stress is high and solder overflow is less critical, while the second region with smaller width is positioned where thermal stress is low but solder overflow could cause shorts. This local optimization balances reliability against harmful factors.
3Loss of energy
If helium gas is used for sealing, then turbulence and windage loss are reduced, but helium leakage occurs due to poor sealing
Solution Approach 1:
The physical state of the sealing material is changed by controlling the width parameter of the mounting surface. By optimizing the width in different regions, the mechanical stress parameters on the sealing material are adjusted to prevent helium leakage while maintaining the low-density gas sealing benefits.
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 significantly improves the reliability of the solder joint section, reducing helium leakage and maintaining the integrity of the sealed helium environment, thereby enhancing the HDD's performance and reducing power consumption and noise.
Implementation Method 1
the thermal expansion coefficient of the flange is preferably between the ones of the sealing material and the base. Since the thermal expansion coefficient of the flange is different from the one of the base, large thermal stress is applied to the solder joint section of the flange and the base.
Implementation Method 2
the flange is soldered to the rim of the opening on the bottom surface of the base so as to securely seal the attaching section
Implementation Method 3
the pins of the feedthrough are fixed to the flange with the sealing material. As the sealing material, glass is frequently used.
Implementation Method 4
there is an idea to reduce the turbulence and windage loss by enclosing low-density gas instead of air in a hermetically-sealed HDD. Hydrogen, helium, or the like is exemplified as the low-density gas
Implementation Method 5
molecules of helium are so small and a diffusion coefficient of helium is large. Therefore, there has been a problem that enclosures used for usual HDDs are poorly sealed so that helium gas leaks easily
Data Source
AI summary
In a disk drive device in which low-density gas is sealed, embodiments of the present invention help to improve joint reliability at a solder joint section between a feedthrough and an enclosure with respect to stress applied by deformation due to changes in temperature environment in use. According to one embodiment, helium gas is sealed in an interior space of an HDD. A feedthrough is solder jointed to a feedthrough mounting surface of a base. At a part with relatively large thermal stress, a width of the feedthrough mounting surface is increased, and at a part with relatively small thermal stress, a width of the feedthrough mounting surface is decreased. This prevents a crack penetrating path from being generated at the solder joint section due to the thermal stress and prevents the solder joint section from contacting pins.