An interposer is the name for an interface that links one electrical connection to another. In this repair, it is the board connecting the battery to logic board.
Lift the Interposer off the logic board and remove it.
Removing this board will ensure that the battery remains disconnected throughout your repair, preventing your computer from accidentally powering on. It's also a good idea to take it out so it doesn't fall out unexpectedly.
Lift and remove the heat sink up off the logic board assembly.
When reinstalling the heat sink, be sure to apply a new layer of thermal paste. If you have never applied thermal paste before, we have a guide that makes it easy.