When opening the shutter assembly, there are 3 small rubber parts. A larger one at the bottom left, 2 smaller ones fit in the bottom right. You'll notice rectangular slots (horizontal or at 45°). That's where they fit.

These 3 JIS #0 screws require quite some torque to unscrew.

Don't forget to open the ZIF connector of the sensor ribbon cable before removing the sensor board.

Inspect the motherboard and ensure that all ribbon cables have been disconnected. Two ribbon cables hide underneath other ribbon cables (top right, bottom left).

The power cable is routed along the real-time clock battery and kept in place with yellow mylar tape. Gently lift the tape to release the power cable and then reattach it to reuse it later when reassembling the camera body.

Remove the motherboard by gently lifting the bottom right corner and gently pulling the motherboard a bit to the right and then rotating it a bit clockwise to dislodge it from the left side.

These are 7 identical JIS #00 screws with a length of 4.4 mm.

Note for D7100: at the bottom of the motherboard, there are 3 ZIF sockets (far left, top: black lever at bottom; far left, bottom (underneath the previous): black lever at top; adjacent to the right: black lever at top).

Note for D7100: at the top of the motherboard, there are 2 wide ZIF sockets (far left: white lever at top; far right: brown lever at bottom) and a narrow "no-fuss ribbon cable connector" (cable connector makes a 90° turn from 12 o' clock to 3 o'clock).

Note for D7100: the 2 ribbon cables that connect the back cover to the motherboard have ZIF sockets with the black lever at the bottom. Leave the other 2 (leftmost) ribbon cables at the bottom of the motherboard untouched.

⚠️ Note for D7100: this step IS needed when disassembling the D7100 body as the rubber conceals 2 JIS #000 screws (5.5 mm at top and 3 mm at bottom). Without removing those 2 screws the back case won't separate from the body. When detaching the rubber cover, make sure to keep the small plastic cover embedded at the bottom of the rubber.

The SD card cover will fall out from the camera body when separating the back case.

Note for D7100: these 4 screws are 6.30-6.35mm long

Note for D7100: the screw holding the diopter dial is 11.4mm long.