The hard drive is an industry of high technology and precision which gather the semiconductor, laser optics, precision machinery, higher physics, and chemical technology. The current market around the world, there are many related products of personal computer can be manufactured, but CPU and Hard Drive can only be made in the United States and Japan . The crucial hard drive techniques have been exceedingly strict controlled in the United States .

The principle of the HDD storage is using the Controller to change the polarity (+,-) of the magnetic on the surface of the media by Read/Write head to store the data. For storing more data in the media, the magnetic has to be made extremely small which is like the sensitization particles in the film, and then coat it on the surface of media with very high density. For the head can speed moving back and forth on the surface of media, it needs to “float” on the top of the media but not touch it. However, the signal will be too weak if the head is floating too high, and it will not be able to fulfill the need of high volume hard disks. Try to lower the flying height to about 0.5 uin which is like a 747 airliner needs to keep the flying height of 1 inch but not crashing. The surface of media must be very smooth; any particle or dust will cause the head to scratch the surface of magnetic (lower than 1% of hair diameter) and also cause the permanent damage to the data. This is the reason why all the processing action required to be taken only inside the uncontaminated Class 100 Clean Room.

This section will focus on some techniques which have not been known publicly. If there are any mistakes, it is very appreciated to have your comments.

The hard drive could divide into Base, PCBA, Media, Read/Write Head, Spindle Motor, and Voice Coil Motor.

The substrate of media is made of metal or glass. To achieve the quality of high density and stability, the surface has to be very smooth without any defects. Layered the magnetic particles coating on the substrate and then covered the lubricant on the top. Two high-tech procedures occur here: 1. to produce tiny magnetic particles without impurities. 2. to coat the magnetic particles evenly.

Using a 3.5" media as an example, the inner diameter is 25mm . The actual diameter becomes 20mm with the deduction of outer and inner circle that does not store data. A 60GB media is being converted into “Bit” as a unit (for easy to understand here: use “Bit” as a unit. 1 Bit record 0 or 1; 8 Bit record as 1 character, such as A, B, or C.)


The density of each side of the media is roughly 32,901,120,000 Bit, which is a very high density. For protecting the media from contamination, all the processing action only can be taken inside the Clean Room.

The media is completely blank and without any signals when the media leaves the factory. It will be encoded when the manufacturers assemble the hard drive.

The head is made of multiple read/write heads (up heads and down heads) on the same set of Actuator Arm. Since they fixed on the same set of Actuator Arm, the whole set of the Arms will move at the same time. The “writing principle” of a hard drive is based on the vertical recording, for example, when a data of 10MB is being stored, the first head writes 4096 Byte (differs in specification), the second head writes 4096 Byte and so on. A file is being broken up into several sections and stored into each media and same as “reading principle.” Multiple read/write heads could achieve high speed required, however, there is more advanced technique available.


The purpose of the Arm can move back to the original position precisely, arm cannot shake when it is moving in high speed, and the perpendicularity of head cannot have any deviation (limited to 0.001% of the diameter of a hair). The head and media cannot be loose or declination , otherwise the track will not be able to follow. The current technologies are not able to make the head or the media return back to the original position when it has been deviated. Besides using the X, Y coordinates and the perpendicular point of the head in 3D graph, the difference of the outer and the inner diameter also have to be taken in consideration. This is also the reason why the hard drive afraid to be collision.

There are one or more than one media on Spindle Motor that have 7,200 or 10,000 RPM (revolution per minute) available. For keeping its balance without shaking, its bearing (ball or liquefied ) qualities required are strict. It needs to be able to sustain 24H x 365 Days of operation continuously without grinding or bearing noise.

Hard drive is assembled in the following order: Spindle Motor, Media, Voice Coil Motor, and Head . And then check the Fly Height which is qualified or not (should be about 0.5 u in).

The head can speed moving between each track because the head is floating on the media without touching it. However, the signal will be too weak if the head is floating too high. On the contrary, the surface of the media will be scratched if the head is floating too low. The surface of media must be very smooth; any particle or dust will cause the head to damage it and the data will lose permanently. Therefore, any actions of the hard drive only can be taken in a high-purified Clean Room. The laser equipment is required to assemble the hard drive, but unable to be done manually.

The hard drive will not be usable until the media has the Sectors. It needs to encode through the specific Servo Track Writer from each manufacturer. Using a 60GB media for example, each side of the media has about 64,260,000 sectors. The amount of sector of inner diameter is smaller than the outer diameter because the media is made by circle. This hardest technique is called Zone Bit Recording.

The hard drive will be usable after Embedded Servo is completed. When the computer power on, the head can stay on the track normally, and the BIOS can detect its specification such as the values of Cylinder, Head and Sector. Finally, the BIOS will send the Controller over to the operating system, and then you could store the data after create a new partition and format.

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