A method includes forming a redistribution structure, which formation process includes forming a plurality of dielectric layers over a carrier, forming a plurality of redistribution lines extending into the plurality of dielectric layers, and forming a reinforcing patch over the carrier. The method further includes bonding a package component to the redistribution structure, with the package component having a peripheral region overlapping a portion of the reinforcing patch. And de-bonding the redistribution structure and the first package component from the carrier.