There are the major settings to be consider to explode the BOM in sales order.

1.The BOM should create with the usage *5*-sales and
distribution.

2.Item category settings

go to VOV7 transaction select your item category then go in to details of that item category here you can find the fields called  Structure scope and  Application under Bill of Material/Configuration tab

These two fields will control the BOM explosion in the sales order.

If you want to explode the fields should have these data.

Structure scope -->

A - Explode single-level bill of material
B- Explode multi-level bill of material
C - Configuration, no BOM explosion
D - Configuration, poss. with BOM explosion
E- Structure from Customer_Function (product selection)

*Application*-->SD01-- Sales and distribution .

3.You need to do Itemcategory determination in VOV4 transaction for the header material and sub compnents of the BOM.

*********************************************************

There are two ways to process a bill of materials in Sales. Once you have entered a bill of material in a sales order, the system runs pricing, inventory control, and delivery processing at:

Main item level if the material is assembled, or
Component level if the material is not assembled

The type of processing used by the system is determined by the item category group that you enter in the material master record for relevant materials.

Processing at Main Item Level
If you want the system to carry out pricing, inventory control, and delivery processing at main item level, enter ERLA in the Item category group field of the Sales: sales org. 2 screen in the material master record of the finished product. This means that the components only function as text items and are not relevant for delivery. The following graphic shows how a bill of material is processed at main item level.

Processing at Component Level
If you want the system to carry out pricing, inventory control, and delivery processing at the component level, enter LUMF in the Item category group field of the Sales: sales org. 2 screen in the material master record of the finished product. In this case, only the components are relevant for delivery. During processing the system automatically creates a delivery group. The latest delivery date among all the components becomes the delivery date for the entire delivery group.