iPhone 6S Backlight Repair
An iPhone 6S backlight repair is a typical service we offer here at microsolderingrepairs.
Typically for a backlight to go out on the iPhone 6S would be a result of a few things, 1 being liquid damage on the motherboard causing corrosion and shorting out the backlight circuit which contains a diode, a backlight ic (U4020) as well as few other discrete components. Another way a backlight circuit can go out is also by installing a replacement screen and bridging a few of the connectors on the LCD FPC connection thus causing a short and ruining the circuit.
As you can see from the images above, this phone has sustained some substantial damage after coming into contact with some water.
As part of the liquid damage cleaning service, we first disassemble the device to get access to the motherboard. We then run the motherboard through our ultrasonic cleaning machine to rid the board of any visible corrosion and hopefully alleviate any shorted components.
After replacing a few burnt capacitors on the VCC_Main line we were able to get the phone booting again, but were left with a very dim image aka no backlight. After lurking around further on the logic board we noticed the below image of a burnt diode on the cathode backlight path. Of course part of the diodes "job" is to protect the backlight boost IC (U4020) and so if the diode burnt then 99% of the time the IC will be overwhelmed with current and also fail. Most often when the IC "dies" it does not do so as catastrophically as other components and leaves very little clues as to its failure.
After replacing both the diode and the back light driver boost ic we were presented with the gloryus apple boot screen image