A scaling model is proposed for A-B diblock copolymers in homopolymer melts based on the minimization of free energy. Competition between the migration of block copolymer to the A and B homopolymer interface and formation of micelles in the B phase has been modeled. Sample calculations done for polystyrene (PS), polybutadiene (PB), and PS-PB diblock copolymers support experimental observation for the onset of micellization and for the aggregation number of a micelle. The model is relatively simple and testable. It can be used as a predictive tool, once knowledge of three scaling factors is obtained. This would allow a priori calculation of the block copolymer concentration needed for full coverage of the homopolymer interface.