A constraint stiffener for reinforcing an integrated circuit package is provided. In one embodiment, the constraint stiffener comprises a rigid, planar base element for bonding to an integrated circuit substrate. The base element has a plurality of elongated support members, and the base element has an opening therein for surrounding an integrated circuit. The base element and support members reduce warpage due to thermal expansion mismatches between at least the integrated circuit and the substrate. In one embodiment, the elongated support members are detachable from the corners of the base element. In another embodiment, the elongated support members have means for attaching and detaching to the corners of the base element. In yet another embodiment, the elongated support members are detachable from about the midsections of the base element. In another embodiment, the elongated support members have means for attaching and detaching to the midsections of the base element.