After removing the back cover of the iPhone, the engineers set themselves to detach the main circuit board and the secondary battery (See related article). We took out the screws that fixed the main circuit board and pulled out the battery and the board from the body.
The main circuit board and the secondary battery. This side faces to the display of the iPhone.
There are a mark "+3.7V LC_" and three six-figure numbers shown on the battery, but, seemingly, there is no clue to the specifications, such as current capacity.
A polymer-type lithium-ion secondary battery
The main circuit board apparently consists of two double-sided printed-circuit boards. There is a slot for a SIM card on one side of the board, occupying a large space.
Many flexible substrates are used to connect the main circuit board with other circuit boards or devices such as display modules. And most of them are printed with "APPLE," showing the company's attachment to the name.
Flexible substrates are used in many parts
The main circuit board and the secondary battery are connected to each other by three cables colored red, white and black. And it looked like that they were soldered.
"How is the secondary battery changed?" the engineers questioned. Probably, the change of the battery was not considered enough.
"We must cut these cables not to be electrified," they said. "But once we cut them, we cannot go back." We felt that it might be wasteful but made a decision to move ahead.
Separating two circuit boards
By taking off the shield from the main circuit board and inserting a tool between two circuit boards, they split up shortly. They seemed to be jointed by only one connector.
Between the two board, there is a 14 mm × 14 mm LSI with the mark of "ARM." The details of the two double-sided circuit boards are coming to light.
Two circuit boards. The right board mounts on the left one.
Break up an iPhone: Part 2 (01:36)
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