An iPhone 6 needed photos saved. The screen showed a damaged backlight and had no touch response, even with a good screen. Turns out the phone was water damaged. So, step one is a careful inspection.Lots of corrosion around the display and touch connectors and a little on the back.
After a careful cleaning, I re-worked the corroded feet on the connectors, but still no improvement. Then I started measuring. Found that several touch related signals from the touch chip were short to ground. Pulled the touch chip, known as “Meson”- corroded underneath.
Cleaned that up, replaced the chip- phone saved!