2008 Wrap Up: iPhone 3G Teardown

Dec 29, 2008
Nikkei Electronics

It is doubtless that Apple's "iPhone 3G" was one of the products that attracted the most public attention in 2008. Although it did not impacted the Japanese market as much as expected, the iPhone 3G added excitement to the smartphone market all over the world, especially in the US.

Provided below is the article we published when we acquired the handset immediately after the release, analyzing its internal structure ahead of anyone else. The way that Apple packaged the secondary battery surprised the engineers attending our teardown project.

On July 11, 2008, Apple Inc released the "iPhone 3G" third-generation (3G) technology mobile phone in 22 countries including Japan. Nikkei Electronics obtained a Japanese version of iPhone 3G released from SoftBank Mobile Corp and disassembled it with the help of Japanese engineers.

Secondary battery hard to be replaced

Many of the engineers participating in the teardown were surprised at the way of packaging the Li-polymer secondary battery. Its shape and the position in the chassis were quite different from those of handsets manufactured by Japanese firms (Fig 1). The Li-polymer secondary battery in the iPhone 3G employed a structure, in which a battery cell is only directly wrapped in a laminate film. Japanese manufacturers usually case battery cells in metal or plastic covers.

"Japanese telecommunications carriers are sensitive to the reliability (of handset)," said an engineer from a Japanese mobile phone manufacturer. "It's hard to believe this kind of design was accepted."

Fig 1: The Li-polymer secondary battery bonded with the back cover of the chassis. The battery capacity was not indicated on the iPhone 3G's Li-polymer secondary battery, which was made in China. The battery cell was directly wrapped in a laminate film, without casing of plastic or any other material. It was fixed on the back cover of the chassis with adhesive tape. The W-CDMA/GSM main antenna on a flexible substrate was positioned at the lower part of the chassis. The sub antenna at the upper part of the chassis was made of metal and seemed to support wireless LAN, Bluetooth and GPS.
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The Li-polymer secondary battery was tightly bonded to the back cover of the plastic chassis. To reach that point, as many as 20 screws and the main substrate must be removed.

"This design does not allow the user to easily replace the battery," said an engineer from a Japanese component manufacturer.

In fact, Apple offers battery replacement service for iPhone 3G users by replacing the handset itself.

We could recognize Apple's efforts to protect components from the heat of the Li-polymer secondary battery. The main substrate and the back cover of the chassis were covered with a graphite sheet at part where they contact with the Li-polymer secondary battery. The sheet appeared to be aimed at preventing the Li-polymer battery's temperature from rising, as well as at discharging heat to the main board's side.

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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.

Fig 2: The iPhone 3G's main board. Major components packaged on one side. Many of the key components including RF circuit, base band circuit and application processor are mounted on one side (the side of the display) of the substrate. Only a few components including flash memory and wireless LAN/Bluetooth transmission module are embedded on the side of the Li-polymer secondary battery. It measures about 84.3 x 53.8mm with a thickness of about 0.7mm. It appears to be an 8-layer substrate. The names of the manufacturers and the purposes of the components were estimated by Nikkei Electronics.
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Fig 3: A sign of Apple's struggle to cut down on noise? The stainless shields that covered the main board seen from the back side. Apple seems to have plated copper on the back of the shield that covers the area where application processor, display interface IC and touch panel controller IC are packaged, to enhance its measures against noise.
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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.

Fig 4: More measures against noise found in the display part. The LCD panel and the touch panel mounted in the iPhone 3G. The 2.2mm-thick LCD panel is a product of Sharp Corp. The flexible substrate is coated with dielectric paste, which seems to prevent noise.
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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.