The drive uses the M.2 2280 form factor, which makes it 22 mm wide and 80 mm long.
While most other M.2 NVMe SSDs transfer data over the PCI-Express 3.0 x4 interface, the WD Black SN850 connects to the host system over a PCI-Express 4.0 x4 interface, which doubles the theoretical bandwidth.
On the PCB, you'll find the controller, two flash chips, and one DRAM chip; the other side of the PCB is empty.
Chip Component Analysis
This is SanDisk's new PCIe Gen 4 controller. WD gave it the marketing name "WD G2." The controller uses eight flash channels and has support for NVMe 1.4, TLC, and DDR4 DRAM.
The two flash chips are Toshiba 96-layer 3D TLC NAND. Each chip has a capacity of 512 GB.
A Nanya DDR4-2666 chip provides 1 GB of fast DRAM storage for the controller to store the mapping tables.