The LCD we see in our iPhone 6s doesn’t produce light itself but is backed by a back light illumination panel. The back light provides light to the LCD to show visible images to us with ambient light. The basic function of back light is to provide illumination to the LCD through back or sides and rest of the visualization is done on LCD through directions of other components. So, when we adjust brightness of the screen it is actually the back light that is adjusted. The back light has a panel made of several layers and it has a potential to get damaged over time. The most common reasons behind the non functional or problematic back light can be liquid ingress, excessive usage or accidents like phone fallen from height. Luckily, MyCel Care has expertise of dealing with all kinds of back light problems in iPhone 6s.