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Hard disk drive manufacturing process

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Hard disk drive manufacturing process takes place in clean rooms, where the amount of dust in the atmosphere is kept very low, and is strictly controlled and monitored. The workers are dressed in special suits, to avoid contamination.

Over the course of almost 70 years the structure of hard disk drive has remained the same. On one side you can see the lid covering complex mechanics inside while on the other you’ll see a printed-circuit board (PCB). The PCB houses the electronics which makes the drive do what it is designed for, to store data.

Inside the casing, or underneath of the lid the space is occupied by one or more platters mounted one on top of the other, separated by ring-like aluminium peaces named spacers. Platters and spacers both are mounted on a spindle motor. As the data is stored on magnetic material on these platters the reading/reading head, and its (Voice Coil Motor) VCM mechanism are designed to fly the heads over the platter surface. Much like phonograph.

 

How hard disk drive manufacturing process works?

 

Video shows combined production process from various manufacturers. The process is done in several factories around the world. In most cases the platters are made in one plant, and yet prepared to store data in another. The reading head is produced some place else, while the final drive is assembled in yet another factory half way around the world. This way the production cost is kept low as we explained in several articles about consolidation of hard disk drive makers.

The drive head rides a cushion of air dozen atoms (nano meters) above the surface of the platter.The disk platter is finished to microscopic tolerances but the platter surface can’t be too smooth, or the drive head will not be able to fly properly. To understand the basic dynamics see Tesla turbine.
 

Platters

The platters come to the factory, packed in shipping cassettes. which are basically carrying cases. When the cassettes have to move from one room to another, they do so on automatic guided vehicles. This is to prevent contamination.

The first step in getting the platter ready to record data is Mechanical Texturing. Here, roughness and groove are applied to the polished surface of the platter which helps in depositing magnetic material on the disk later. During the texturing process, small amounts of nickel get removed from surface of the disk and then washed, process is called Oliver Wash.

Some drives land their heads on the surface while turned off so some platters will have a 2-4 mm band near the center. This is the Laser Texture, the landing area. The landing area is created by creating microscopic bumps, using a laser. This prevents the head clinging to the disk surface when the disk is spinning.

The final cleaning of the platter is done using a series of ultrasonic, mega sonic and Quick Dump Rinse (QDR) steps. At the end of the final clean, the platter has an ultra-clean surface and is ready for depositing of magnetic media— a process known as sputtering. The platters now move to a Class10 clean room, in an automatic guided vehicle, described earlier. Sputtering is perhaps the most critical in the whole process of creating a recording media.
 

Head Stack Assembly and Voice Coil Motor

Head stack assembly (HSA) holds all the components necessary to safely fly the heads over the surface while Voice Coil Motor is designed to place the head over the specific track. HSA can be separated by its components which are head gimbals assembly (HGA), dual-stage assembly (DSA), slider head assembly, pre-amp on flex assembly and coil of a VCM assembly. These components are made using special robotic devices.

Head stack assemblies have fine flex circuits to transfer the signals from slider head to pre-amp. The circuits are set into the small channel on the arm to avoid air friction with UV-cure adhesive. DSA is embedded on HGA to adjust the slider head position precisely on the disk. PZT is a piezoelectric component designed to move the head slightly. Two PZTs are attached on HGA with die attach material. PZT size is around a millimeter size, and the die attach material thus has to be aimed to a-few-hundred-micron target, and multiple locations with a few hundred micron apart. The material dispensing is to be quite accurate, small dots and precise short moving.

The PZT needs interconnection with conductive paste (silver epoxy). Because of the PZT size, the paste dot also has to be small down to a few hundred microns: same challenge as PZT die attach material.
 

Pre-Amp on Flex Assembly

Pre-amp should be closer to the slider head to diminish noise. The pre-amp (flip chip) is located on flex circuits because they can be attached to the HSA. Flip chip needs underfill. Unlike rigid boards, flex circuits are “flexible”.

Final Assembly

Like stated above the hard disk drive manufacturing process takes place in clean rooms, where the amount of dust in the atmosphere is kept very low, and is strictly controlled and monitored. Previously assembled components are placed inside the disk chamber using fully automated robotic production line. Assembled drive is then loaded with its firmware and tested for performance.
 
 

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