If you want to for research and higher studies after your M. tech. IISC, Bangalore is the best option.
If you are joining from job perspective, then IIT, Bombay will be very nice option.
Later you can choose from any older IIT preferably IIT Delhi, Madras, Kanpur and Kharagpur.
If you want to do Mahcine Design, IIT Bombay and Delhi are best.
For thermal, IIT Madras and Kharagpur are right options.