A second substrate is positioned relative to a first substrate having phase-changeable bumps, such as solder bumps, between them, wherein the second substrate has a first face adjacent the first substrate, a second face remote from the first substrate, and at least one edge wall between the first and second faces. The phase-changeable bumps are liquefied to establish an equilibrium position of the first and second substrates relative to one another. At least a portion of the second face is pushed away from the equilibrium position towards the first substrate, to a new position, without applying external force to the first face other than spring forces of the phase-changeable bumps that are liquefied, and without applying external force to any edge wall. Thus, only spring forces of the phase-changeable bumps that are liquefied oppose the pushing. The phase-changeable bumps that are liquefied then are solidified, to maintain the new position.