Wafer-level packaging

In WLP, the top and bottom layers of the packaging and the solder bumps are attached to the integrated circuits while they are still in the wafer.

Wafer-level packaging allows integration of wafer fab, packaging, test, and burn-in at wafer level in order to streamline the manufacturing process undergone by a device from silicon start to customer shipment.

Functions provided WLPs in smartphones include sensors, power management, and wireless.

[1] The iPhone 7 was rumored to use fan-out wafer-level packaging technology in order to achieve a thinner and lighter model.

[4] A WL-CSP or WLCSP package is just a bare die with a redistribution layer (RDL, interposer or I/O pitch) to rearrange the pins or contacts on the die so that they can be big enough and have sufficient spacing so that they can be handled just like a ball grid array (BGA) package.