The analyst claims that the hardware design of Force Touch will be different than the technology used in the Apple Watch and 12-inch Retina MacBook. Instead of directly detecting the pressure applied by fingers, the new improved Force Touch hardware will monitor the contact area where a finger presses to determine how much pressure is being applied. The sensor will use capacitive technology and thin FPC material to save space.
Kuo adds that Apple is likely to change the hardware design of Force Touch again in 2016 by removing the metal shielding to achieve a thinner form factor. He notes that the changes should improve the iPhone user experience, but will likely create uncertainty for Force Touch module suppliers TPK and GIS, as well as metal shielding suppliers Minebea, Hi-P and Jabil."We believe that iPhone's Force Touch sensor doesn't directly detect the pressure applied by fingers. Instead, it monitors the contact area on which the finger touches the screen to decide how big the pressure is.
There are two possible structural designs for Force Touch from a technology viewpoint. The Force Touch sensor can either be placed between the cover lens and the In-cell touch panel or under the In-cell touch panel's backlight. In the first position, the technological challenge lies with how to produce the transparent Force Touch sensor; in the second position, the challenge is how to reduce signal interference from in-cell touch panel. Our understanding of the technology is that producing a transparent Force Touch sensor is more difficult, so the chances are the new iPhone this year will opt for the second position."
Article Link: iPhone's Force Touch Tech May Track Contact Area Instead of Pressure, New 4" Model Unlikely in 2015