In 500 GB or higher capacity HDD's, you can frequently find these black things (see photo below). It is made from a very weird feeling material. It is not made of plastic, it has a dull glass sound when hitting something, it is not painted black iron/steel/aluminium, it is not ferrite (a magnet cannot pick it up), it is very strong, very light and very conductive.

What is this kind of material and what is it used for, shielding? I ask this because this part is not described anywhere. It seems a latest addition, does not exists in earlier lower capacity drives.

Any ideas?


  • 2
    \$\begingroup\$ Its a laminar flow cover made of carbon fibre which is stronger than steel and almost hard as glass. It must be non-magnetic and not metallic to avoid eddy currents. It looks like it crashed head. from radial scratch during power up or down. \$\endgroup\$ – Sunnyskyguy EE75 Jun 5 at 16:18
  • \$\begingroup\$ Hi, thanks for the answer! I think you are right. Just watched two video's about carbon fibre right now, it can also be molded in shapes like this and is conductive. Didn't know this. The question is why they add these things above the platters, older versions doesn't have these. To manage airflow? \$\endgroup\$ – Codebeat Jun 5 at 16:40
  • \$\begingroup\$ By older , do you mean prior to vertical recording at > 6000 RPM? \$\endgroup\$ – Sunnyskyguy EE75 Jun 6 at 5:27

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