Nidec – Helium-filled HDD

By reducing the resistance of the airflow, the vibration of the disk is reduced

Realize the improvement of burning/reading accuracy of disks and low power consumption.

Normally, the inside of an HDD is filled with the same air as the outside world. The memory capacity of each unit of the HDD has increased with the evolution of the head and the way of recording, and the spindle motor in the HDD rotates thousands to 10,000 times per minute, and the disk vibration caused by the natural air flow resistance has a great impact on the burning/reading accuracy of the disk, hindering the increase of the disk recording capacity.

If you can reduce the vibration of the disk by reducing the airflow resistance, you can not only improve the accuracy of burning/reading, but also make the disk thinner and thinner, so that more disks can be stored in the HDD. In addition, the current flowing through the motor is reduced, which reduces power consumption.

Japan Electric Corporation's challenge was to reduce airflow resistance by filling the HDD with helium instead of air.

The airflow resistance caused by the air inside the HDD has become a major factor that cannot be ignored. By reducing the resistance to airflow, the vibration of the disk is reduced, which in turn improves the burning/reading accuracy of the disk and reduces power consumption

Helium is only one-seventh the density of air, and while the resistance to air flow decreases, the size of atoms also decreases, and it is easy to leak out of the holes in the adhesive material and the cast bottom plate of the aluminum cast. In particular, it is extremely difficult to ensure that helium is confined to the HDD for the 5-year product life cycle.

In order to prevent helium from leaking out of the base plate, which is only 1 mm to 2 mm thick, CAE is used to analyze the flow of molten aluminum during casting, and to optimize the shape and temperature control data of each part of the mold during casting.

In addition to vacuum casting technology, many casting technologies have been developed and adopted. As a result, we established a technology for mass production of base plates that can seal helium for five years with fewer structural defects.

In order to keep helium sealed for 5 years, certain structural defects are allowed. For example, the gap between the left and right of a strand of hair.

If the gap is outside of this range, helium will slowly leak out.

In addition to the structural defects of aluminum casting, the leakage of helium from the adhesive part has also become an issue. In order to prevent helium leakage in such cases, a structure has been established to ensure the thickness of the adhesive and to use a press-in bonding method for the parts.

Since gases other than helium can contaminate the inside of the HDD, an adhesive with less outgassing (volatile gas) was used. In addition, in order to reduce outgassing of adhesives and resin materials, heat treatment is carried out at each stage of the process, and pre-venting is performed.

In cooperation with oil manufacturers, we have also developed oil for hydrodynamic bearings for motors that has low volatility and can resist external air humidity.

Instructions from R&D personnel

Helium-charged HDDs, which have achieved large capacity and low power consumption, are selling well in the server market for data centers. In the future, we will continue to push forward the high-capacity development of HDDs by taking on the challenge of next-generation recording methods, such as thermally assisted recording methods and multi-layer magnetic recording methods. In this situation, Japan Electric Power should support the high-capacity HDD project, and take on the challenge of developing new technologies not only for the structure of the motor, but also for the substrate and top cover, as well as the materials used in these components.

Nidec – Helium-filled HDD

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