Ah, I remember those from the IBM Deathstar 75GXP 😀
It should just be an ESD proof cover so that the hard drive is less likely to get damaged during installation. But it could also serve a purpose of protecting delicate / easily dislodged pins.

Seagate did similar stuff with the SeaShield metal cover on some of their drives from around that time. And the silly rubber cover on some of them. All in an effort to reduce RMA rates probably

These are ESD shields. Back in the day ICs was extremely sensitive.

Cheers,

Honestly, I am having a hard time to believe that this is ESD related.

First, the shields don't protect if traces beneath are being touched, and it is really unlikely that one touches these recessed pins first.
Second, ESD protection stuff (diodes etc) is quite common since early-mid 1970s.
Third, HDDs are normally first touched at the metal, which also does ESD discharge (relative to drive ground).

So I think the SeaShield is more useful in ESD protection than these plastic covers.

What makes me wonder is that these chips are often scorchingly hot, so one can get burn blisters.
I am thus tempted to speculate that it is for burn/fire protection.
But speculating is different than knowing, so my question.

Any one who had C= computers would disagree with you. Very sensitive to ESD. This is what killed our Ti 94/A back in the day, no matter how careful we were.

Cheers,

The traces are protected by solder mask. You're not going to esd through that

retardware wrote on 2021-09-09, 00:49:

What makes me wonder is that these chips are often scorchingly hot, so one can get burn blisters.
I am thus tempted to speculate that it is for burn/fire protection.
But speculating is different than knowing, so my question.

if it was to protect you from getting burned there wouldn't be holes right where the hot part of the chip is, also would be very counter productive to cooling :p
esd protection just makes the most sense, protecting against anyone handling the hdd from touching the package legs directly where esd would certainly cause the most damage.

Another manufacturer was putting full body wetsuits (Or IDK, maybe they were meant to be latex gimp suits) on their drives, so maybe they did it so the salesdroids weren't constantly bugged with "Why come YOUR drives don't have protection?"

I've seen this on other hard drives, quantum, and maxtor for example, sometimes they had a black shield too. I like to believe they put this in so you can test the hard drive outside the case without the risk of something touching a metal surface (which would cause a short circuit)

What you see is a compromise. That chip needs ESD protection but they can't just put a lid on the whole thing, the chips would overheat in a fully enclosed case.
So they did the next best thing.