The appropriate HDD head inspection – The light source
The head replacement procedure on a hard drive is one of the most delicate mechanical operation during data recovery process.
Due to various types of head damage, this procedure sometimes may takes several tries and donors. In a certain number of cases, engineers need to inspect and clean the heads from all dust and small particles which got stuck on the head’s sliders (ferrits).
The whole inspection process should be performed under the microscope and with extreme caution in order to preserve the functionality of the heads.
The HDD head inspection equipment
When we speak about the proper inspection process, it is important to mention the necessary equipment for performing such operation:
- Holder for the heads
- Artificial light
In the following paragraphs we will try to further describe the equipment listed above.
The Microscope is a necessary piece of equipment for this kind of operation. The hand magnifying glass can be used, but it is not as usefull as a microscope when you need to analyze the black surface of 1x1mm slider.
When comes to magnification, a single-lensed simple microscopes can magnify up to 300×, while compound microscopes can magnify up to 2,000×. For data recovery company, any affordable microscope which can magnify the object between 10 and 100x should be quite enough.
Additionally, you can connect the LCD display and have even a better view of the operation.
Holder for the heads
Considering the size and position of the sliders, a special holder for the heads is necessary in order to maintain a sharp in-focus image as well as stability during the inspection.
These holders are special assistive tools which enable tight clamping, stability and even shifting of the head assembly under the microscope.
A standard Clean room does not have enough natural light for the microscope to be used. That’s why we need to bring the artificial lighting close to the heads.
This light source should have a certain power so the slider can be properly examined. For the proper inspection, it is recommended to keep between 6000 and 7000 Lux units on the heads, as this is the optimal light power to notice the particles on the heads.
When comes to microscope light, the most important setting is the position of the source.
From the angle of the light depends on the reflection of the surface of the head, and therefore the ability to notice the trails of the dust.
On the image below you may see different position of the light source on the same slider:
As you can see, it is obvious that the left image has a better light source and reveals more information about the surface.
Now let's explain the sources.
On the image below you can see how these sources were positioned during the inspection:
The two possible ways to attach the artificial light source are the side lighting and top lighting.
The side lighting is a light that illuminates laterally on the object of observation. The result will be better reflection which will allow engineers to easily separate surfaces, lines, wedges, notches and shapes.
The top lighting will bring the light source directly above the object, in this case the slider. All the shapes and structures on the surface will be less visible and hard to detect due to the loss of shadows.
As you can conclude, the left image from the experiment above had the side lighting and the right image had the top lighting.
The 3D depth can be easily discovered when the light comes from the side rather than the top.
Because of the flat surface and the angle of ~45°, the sliders will reflect the side light from the source directly to your eye.
This allow you to inspect and clean the heads if necessary.
When speaking about mechanical problems on HDD, each data recovery case will be unique and it will maybe require a completely different approach in solving the malfunction.
In order to successfully solve these types of problems on hard drives, engineers need to have good tools, experience, practice and a lot of patience.
The described items can save a lot of time and increase the efficiency of the recovery process. Of course, having the additional equipment like various tweezers, sticks, gloves, etc. come handy with the cleaning process and it is recommended to have it in the lab.
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