A package includes a device die, which includes a metal pillar at a top surface of the device die, and a solder region on a sidewall of the metal pillar. A molding material encircles the device die, wherein a top surface of the molding material is substantially level with a top surface of the device die. A dielectric layer overlaps the molding material and the device die, with a bottom surface of the dielectric layer contacting a top surface of the device die and a top surface of the molding material. A redistribution line (RDL) extends into the dielectric layer to electrically couple to the metal pillar.