Dear shyam,
Consider if you have 3 material A-FIN, B-SEM. AND C-RAW, now your issue is how to send C to vendor and recieve A. correct if I m wrong.
If this is the case, please follow settings in master.
1) Go to Finish matl bom.
2) go to SFG material and mark as phantom assy. with key 50. and save.
Or
you can create a alternative bom for subcontracting process which includes only raw under FG.
Hope it helps you.
With best regards,
Manish K. Bachate