An apparatus relating generally to a substrate is disclosed. In this apparatus, a first metal layer is on the substrate. The first metal layer has an opening. The opening of the first metal layer has a bottom and one or more sides extending from the bottom. A second metal layer is on the first metal layer. The first metal layer and the second metal layer provide a bowl-shaped structure. An inner surface of the bowl-shaped structure is defined responsive to the opening of the first metal layer and the second metal layer thereon. The opening of the bowl-shaped structure is configured to receive and at least partially retain a bonding material during a reflow process.