Kuo believes that we will see a home button with a convex (raised) shape instead of the concave one we see in all iPhones today. The new convex shape would give Apple more room to fit in a fingerprint sensor -- a feature that is expected to be a discerning factor between the iPhone 5 and iPhone 5S.
Convex home button creates space for fingerprint sensor; yield to improve. We think that a fingerprint sensor will be placed under the home button of iPhone 5S. However, assembling it could be difficult as the space under home button is limited as it already has to accommodate the Lightning connector, speaker and microphone. Thus, we think the shape of the home button could be changed from concave to convex to create more space for a fingerprint sensor.
Sapphire prevents home button from being scratched. A convex home button could be more easily scratched, so a harder material is required. We believe Apple will switch from plastic to sapphire, whose hardness is second only to diamond. Sapphire would protect the home button from being scratched and the fingerprint sensor from being damaged.
While some have suggested the fingerprint sensor in the iPhone 5S could almost be a gimmick, Kuo believes Apple will utilize RF and capacitive technologies to make their sensor more durable and resistant
to dust and other contaminants.
The iPhone 5S is rumored to be unveiled on September 10th.
Interestingly enough, despite all the iPhone 5S part leaks, we have yet to see any physical evidence of an iPhone 5S fingerprint sensor (only code fragments and from previous betas and other rumors).