Try to remove the top metal with gallium (if aluminum is there)

[ogamespec]

Gallium forms an amalgam with aluminum, so you can peel off the amalgam to avoid working with acids.

Gallium can be ordered from aliexpress, you don't need much, since the chip surface is small.

https://aliexpress.ru/item/1005001300820374.html

Gallium attacks aluminium: https://www.youtube.com/watch?v=IgXNwLoS-Hw

[ogamespec]

There's aluminum inside, confirmed.

We must take into account that the surface of the chip is most likely covered with a film of SiO2, so just to put gallium on the surface will not be enough. You must first scratch off part of the upper film, and most likely the aluminum itself is covered with a film of aluminum oxide, as usual.

[ogamespec]

[ogamespec]

[ogamespec]

[ogamespec]

[ogamespec]

Experiments with gallium yielded weak results. The metal comes off, but very slowly, if almost none.

So I removed the metal by the old tried-and-true way, using GOI paste and Dremel. (https://github.com/emu-russia/psxdev/blob/master/docs/Delayering_by_russians.pdf)

[ogamespec]

One last note about gallium is that it's an asshole that stains surfaces very badly with a gray ectoplasm, which then doesn't come off well.