> sample decapsulating, milling die from the plastic package with CNC, then etch... | Hacker News

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ThePowerOfFuet on April 30, 2020 | parent | context | favorite | on: Revengineered ancient PDP-11 CPUs, originals and c...

> sample decapsulating, milling die from the plastic package with CNC, then etching with 104 percents boiling oleum

Then etching with... what?

kees99 on April 30, 2020 [–]

Oleum. Fuming sulfuric acid.

https://en.wikipedia.org/wiki/Oleum

wolfgang42 on May 1, 2020 | [–]

And apparently the percentage is strength relative to (non-fuming?) sulfuric acid (i.e. neat sulfuric acid without sulfur trioxide added) which is why it’s over 100%.

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