In a described example, a method includes: forming cavities in a die mount surface of a package substrate, the cavities extending into the die mount surface of the package substrate at locations corresponding to post connects on a semiconductor die to be flip-chip mounted to the package substrate; placing flux in the cavities; placing solder balls on the flux; and performing a thermal reflow process and melting the solder balls to form solder pads in the cavities on the package substrate.