The gang at iFixIt have torn apart yet another iPhone 6 to answer two burning questions. One: How exactly did Apple implement the 3D Touch feature? Two: What will that do to the screen repair procedure?
Here's what iFixIt found:
The 3D Touch sensor assembly lives on the very back of the display panel, and is fairly easily separated from the backlight, display, and digitizer glass.
The home button cable has been replaced by traces along the side of the 3D Touch sensor panel, eliminating the need to transfer the cable for certain display repairs.
The sensor panel is a grid of rectangular capacitor plates, connected to the controller IC by very tiny traces. These plates would be huge for a touch sensor—luckily their job isn't to pinpoint your fingertip on the screen, as the in-screen digitizer will still handle that. These sensors measure the distance to your finger, equating to the force of a press through pliable glass.
"This teardown was quite the endeavor—we definitely do not recommend you attempt this at home without the right tools and experience," says iFixIt. You can find more details here.