Isn't the idea with IR that you can transmit through the silicon and part of the package. There are slightly higher resolution options like IR confocal microsco

Isn't the idea with IR that you can transmit through the silicon and part of the package. There are slightly higher resolution options like IR confocal microscopes https://www.wdidevice.com/products/ https://www.wdidevice.com/products/ and X-ray can do some similar stuff.