Continued from [iPhone X Teardown] Parts-containing Main Board (4)
Considering that many connectors were mounted on the AP substrate, the engineer said, "Apple probably considers that the combination of solder and connectors realizes a high noise resistance and is suited for high-speed operation. At a glance, it seems that no ACF (anisotropic conductive film) is used."
Slimness, heat radiation performance of FOWLP serve purpose at this point
The thickness of the interposer is less than 2mm. With this thickness, it is probably difficult to adjust the heights of parts mounted on the upper and lower surfaces. The "A11 Bionic," which was mounted on the interposer, uses FOWLP (fan out wafer level package), as in the case of the A10 Bionic (previous model). FOWLP is a technology that pulls out the pins of semiconductor chip by using a semiconductor technology-based rewiring layer without a package board (interposer). It reduces thickness and realizes a high heat radiation performance.
However, the thickness of some products including the iPhone 7, which is the first iPhone equipped with the A10, did not change much. And some experts wondered for what purpose FOWLP was used for them. If Apple employed FOWLP (which reduces thickness and improves heat radiation performance) for the A10 (iPhone 7) in the aim of gaining experience and producing results with an eye to the two-story PCB of the iPhone X, we can say that Apple is formidable.