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.
[Click to enlarge image]

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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