When you carry out a screen repair on the iPhone 5S, there is a shield which need to be removed, this shield covers the LCD cable, Proximity sensor cable and the touch screen digitiser cable. This shield is fixed to the board of the 5S to stop the cables being dislodged easily by a drop, this was a common issue in older iPhone models and this is the reason the shield has been put in place. Now you can see from the image above that these screws are all individual and should be put back in the same slot they came out of.