This guide provides instructions on how to replace the shutter button assembly on the Canon PowerShot S400.
Remove the 4.75mm screw located in the top right corner of the backside of the camera.
Remove the four # screws located on the bottom of the camera.
Remove the two screws located on the right side of the camera.(the side with the USB adaption plug)
Remove the four screws on the left side of the camera.
This will release a small metal plate. Remove this plate.
Now separate the front and back camera casings.
Using a spudger, carefully pry the shutter button assembly from the camera.
Install the replacement shutter button assembly.