Main board design improved
The main board functions were integrated into a single piece, which mounts most of the major components on the side of the display (Fig 2). In the first-generation (2G) iPhone, the wireless circuit board was separate from the main board.
"The design has quite advanced and come close to the level of main board sseen in Japanese handsets," said the engineer from a Japanese handset manufacturer.
The RF circuit part, to which W-CDMA/HSDPA function was added, employed a chipset of Infineon Technologies AG of Germany.
"Apple appears to have added little arrangement to Infineon's reference design," the engineer said.
The company equipped the iPhone 3G with three units of TriQuint Semiconductor Inc's W-CDMA/HSDPA power amplifier/duplexer modules to support four frequency bands and make the handset usable all over the world.
"If the handset were dedicated only to SoftBank Mobile (Japanese carrier for the iPhone 3G), it would require only one module," the engineer said.
Meanwhile, Apple seems to have struggled to cut electromagnetic noise around the main board. Only the back of the shield covering application processor, display interface IC and touch panel control IC is plated in copper (Fig 3). It seems to be aimed at strengthening measures against noise.
"Apple may have added it later when it found a problem during the prototype stage," an engineer from a handset manufacturer said.
The flexible substrates of the LCD panel display and the touch panel are coated with dielectric paste, which appears to be aimed at preventing defective display caused by electromagnetic noise and malfunction of the touch panel (Fig 4). This is possibly related to the fact that the touch panel controller IC is mounted on the main board.
"As touch panels often malfunction due to electromagnetic noise, a touch panel controller IC is usually located as close to a panel as possible by, for example, mounting it on a flexible substrate," the engineer said.