Carefully lift the logic board from the end closest to the speaker enclosure and slide it away from the top edge of the iPhone.

Remove the logic board.

Before reassembly, be sure to clean all metal-to-metal contact points on the logic board (not the mating halves of connectors) with a de-greaser such as windex or isopropyl alcohol. The oils on your fingers have the potential to cause grounding issues.

There's a small rectangular rubber pad at the top of the logic board that prevents the display cables from chafing against the edge of the board. If it comes loose during your repair, make sure to position it correctly when reinstalling your logic board.