Once the battery and case back cover have been removed, the motherboard can be accessed as shown in this guide.
Slide the cover release button towards the bottom of the phone
Once the battery cover pops up, slide the cover towards the top of the phone and lift up.
Push the battery towards the top of the phone and lift up.
With a T5 screwdriver, unscrew the four T5 sized screws that hold the case back cover onto the rest of the case.
Remove the plastic case back cover by gently pulling it away from the body of the phone, starting at one edge and working your way down to the other.
Lift the motherboard away from the case of the phone, being careful not to break the wire that goes up into the hinge.
Peel the motherboard off of the keypad. The two pieces are glued together and separate without much effort.
The motherboard should now be completely disconnected from the phone.