Sub-Items 
Partial quantities of a BOM item may be installed at different points. Sub-items are used to describe the different installation points of these partial quantities.
- In Customizing for Production, you define for each item category whether sub-items are supported by choosing Bill of material → Item Data → Define item categories. For example, in the standard system, sub-items are supported for Stock items and Variable-size items.
- In the standard system, changes to sub-item data are not recorded by engineering change management.
In Customizing for bills of material, under Define modification parameters, you can define whether the old change state of a sub-item is retained after you change the sub-item.
If at least one values of the sub-item is changed with changed effectivity parameters, the system creates a new item record for the new change state.
- You can maintain the sub-item quantity and a description for each sub-item.
Sub-items have no operational function in the BOM. They are not copied to the production order. However, you can use sub-items to help you create programs for your company (for example, automatic assembly programs).
In the production of printed circuit boards, the resistors of a printed circuit are installed in different positions. Information on the installation point, precise coordinates, installation method, and instructions for the automatic assembly machines is stored as independent programs.