Continued from [iPhone X Teardown] Parts-containing Main Board (1)
However, the MSAP can only narrow the line interval of printed circuit board (PCB), and it cannot reduce the number of parts or their footprints. The main board of iPhone is known for its high-density mounting. Various sizes of parts are tightly arranged with no space like a jigsaw puzzle. So, there is no extra space in the first place. We analyzed the PCB with experts who were very interested in how all the necessary parts were mounted on the board whose area was reduced by 1/3.
You may notice that the detached main board is strangely thick. It turned out to be a PCB that has a "two-story structure" with something like a spacer in between. With this method, it is possible to secure space for mounting parts. The method of splitting a PCB and stacking them has already been used for many consumer products.
Of course, the two boards need to be connected with each other in some way. In general, they are connected by using cables, flexible PCBs, etc, but there seemed to be no such thing on the PCBs of the iPhone X.
"These days, there are many cases in which a rigid flexible PCB (a PCB made by combining rigid and flexible substrates) is used to connect PCBs," said an engineer who work for a substrate material maker.
But there seemed to be nothing similar to it.