<p>The solder (105) on the contact surface where a pad (2) is contacted, has a central zone and an edge zone. The solder in the central zone is more strongly alloyed with the material at the central surface (3) of the pad, than is the solder in the edge zone. The separation between components (101) is set by stand-offs so that the solder causes an attraction between the component and the substrate due to its surface tension in a molten state.</p>
