after btech is it good mba

Well, I think your answer is embedded in your question. If you wish to work in it's core, it doesn't necessarily make all that much sense. Advancing in your technical field might very well be more worthwhile (Masters, PhD), but very often, people who decide to do an MBA have slightly different or

Best practice would be to gain couple of years experience before taking up MBA. This way, the experience gained will help to understand better the general principles of management and also equip you to be ready for the leadership role down in your career