Tearing Down SoftBank's Handset w/ Touch Sensor

Apr 22, 2008
Nikkei Electronics Teardown Squad

This time, the Nikkei Electronics Teardown Squad will tackle SoftBank Mobile Corp's handset, the FULLFACE2 SoftBank 921SH.

The handset is manufactured by Sharp Corp. It is positioned as the successor of FULLFACE SoftBank 913SH released in July 2007. The main feature of the 921SH is that it can be operated by touching the screen, tracing on the screen with a finger or shaking the main unit. Although it also employed a touch sensor, its predecessor could not be operated by tracing on the screen with a fingertip.

The purpose of our teardown is to determine the differences and similarities between the former and latest models. We discovered that the latest model uses a number of parts that are the same as those in the former model, except for the sensor. In particular, the LSI mounted on the main board has the same components used not only in the 913SH, but also in the 920SH, which is also manufactured by Sharp and sold by SoftBank.

The following pages describe the structures of the touch sensor, the main board and the chassis. The investigation was conducted with the cooperation of Fomalhaut Techno Solutions, as with the disassembly operation of another mobile phones featuring improved camera functionality (See related article).

Product nameFULLFACE 2 SoftBank 921SH
DimensionAbout 112 × 50 × 15.9mm (excluding protruding portions)
MassAbout 135g
Standby timeAbout 330 hours
Talk timeAbout 240 minutes
DisplayAbout 3.2 inches (480 × 854 pixels)
Memory cardmicroSD memory card, microSDHC memory card)
Camera3.2 million effective pixels (main), 0.11 effective pixels (sub)
Battery3.7V, 790mAh

(Continue to the next page)

The touch sensor incorporated in the 921SH was a capacitance sensor that was most likely made by Alps Electric Co Ltd. Alps Electric's touch sensor was also used in the 913SH. But it is operated by three points on the sensor, which act as the buttons. The touch sensor of the 921SH has a scroll function used by tracing on the sensor screen with a finger.

(Continue to the next page)

The board was mounted on the back side of the 921SH LCD panel with a metal shield inserted between them. It has LCD and LED drivers, etc. The LED driver was most likely manufactured by Rohm Co Ltd.

(Continue to the next page)

The main board and the sub-boards with the card slot, etc, were supported by a plastic frame.

(Continue to the next page)

The LSIs mounted on the 921SH main board were composed of a number of chips that were the same as those used in the 913SH and the SoftBank 920SH, which was manufactured by Sharp and sold by SoftBank in November 2007. In particular, the chipset related to the communication functions and the application processor were identical to those used in the 920SH.

The same communication-related chip is also used in the 913SH. The application processor in the 913SH was made by the same manufacturer but with a slightly different model number. The same manufacturer provided the flash memory and other components for these three models.

The 921SH has a sensor available from Analog Devices Inc so that the handset can be operated by shaking or tilting the main unit. Assuming from the model number, the IC in the upper right photo is most likely an angular velocity sensor.

(Continue to the next page)

The various antennas can be found inside the chassis on the main camera side.