A device for assembling an element on a surface of a substrate by providing a solder-forming mass. The device has a means for moving the element and a measurement means. The means for moving the element includes a support and an element gripper member. The gripper member has a vertical axis that is perpendicular to the surface of the substrate and is mounted to move freely in translation on the support in a direction parallel to its vertical axis. The measurement means measures a variation of the position of the element in vertical translation.