A device includes a first and a second package component. A metal trace is disposed on a surface of the first package component. The metal trace has a lengthwise direction. The metal trace includes a portion having an edge, wherein the edge is not parallel to the lengthwise direction of the metal trace. The second package component includes a metal pillar, wherein the second package component is disposed over the first package component. A solder region bonds the metal pillar to the metal trace, wherein the solder region contacts a top surface and the edge of the portion of the metal trace.