Hi Keerthan,
As pete explained, it is not mandatory to create assembly but it can give a clear picture how the technical object is structured.
IBAU (assembly) type material can be created which doesn't exists physically, but is a structure.
Now you can create material BOM of this IBAU type material which consist of BOM items which may be physical materials and or further sub assemblies (IBAU). Now this sub assembly also may consist further combination of materials.
Again this main IBAU type material BOM shall be assigned to equipments in construction type field (In equipment master).
By this way we can structure complex technical objects.
Regards,
Vinod. V