does all data from dead phone is crashed if motherboard get changed



It is possible to get the data, but it is too much work to get the data from the chips if the phone is dead.
It requires careful precision and a skilled repair tech to take on such operation. You will have to remove (unsolder) the NAND flash from the logic board and then you will have to careful clean them and solder each chip back into another working logic board.



 


Only encryption will work.
But you don't need to worry about it....Unless you have data worth something and the person that happens to have your device knows it. ;)