Continued from [iPhone 4S Teardown (1)] Totally Different Components
When one main board was laid on top of the other, it was obvious that the width of the iPhone 4S' main board was larger than that of the iPhone 4's main board.
While carefully looking at the extended part of the board, we found an antenna wire, which was not seen on the iPhone 4's main board. The wire was fixed by a metal cover employed as a countermeasure to electromagnetic noise, and it was in parallel with the main board.
When we were removing the antenna wire, we found a metal contact point that was in contact with the metal cover. Some people pointed out that the reception sensitivity of the iPhone 4 deteriorates depending on the way it is being held and that the problem is caused by the design of its antenna. Probably, Apple Inc addressed to this problem by using the new antenna design.
According to an article of iFixit, the antenna wire was actually employed for the first time for the CDMA version of the iPhone 4, which was not released in Japan. The shape of the iPhone 4S' main board is very similar to that of the CDMA version's.
Also, the iPhone 4S' vibrator, which is larger than the iPhone 4's vibrator, was seemingly employed for the first time for the CDMA version. The lower parts of the CDMA version's and the iPhone 4S' main boards were cut in a circular shape probably to make a space for the vibrator.
In terms of the positions of connectors on the main board, there was a considerable difference between the iPhone 4 and the iPhone 4S, but the difference is relatively small between the CDMA version and the iPhone 4S.
However, because the CDMA version does not have a SIM card slot, the layout of components on its main board is different from that on the iPhone 4S' main board, on which there is a SIM card slot. So, it can be said that the CDMA version was developed based on the iPhone 4 and the iPhone 4S was developed by improving the specifications of the CDMA version.